Algorithm for correcting the keratometric error in the estimation of the corneal power in eyes with previous myopic laser refractive surgery.

PubMed

Camps, Vicente J; Piñero, David P; Mateo, Veronica; Ribera, David; de Fez, Dolores; Blanes-Mompó, Francisco J; Alzamora-Rodríguez, Antonio

2013-11-01

To calculate theoretically the errors in the estimation of corneal power when using the keratometric index (nk) in eyes that underwent laser refractive surgery for the correction of myopia and to define and validate clinically an algorithm for minimizing such errors. Differences between corneal power estimation by using the classical nk and by using the Gaussian equation in eyes that underwent laser myopic refractive surgery were simulated and evaluated theoretically. Additionally, an adjusted keratometric index (nkadj) model dependent on r1c was developed for minimizing these differences. The model was validated clinically by retrospectively using the data from 32 myopic eyes [range, -1.00 to -6.00 diopters (D)] that had undergone laser in situ keratomileusis using a solid-state laser platform. The agreement between Gaussian (Pc) and adjusted keratometric (Pkadj) corneal powers in such eyes was evaluated. It was found that overestimations of corneal power up to 3.5 D were possible for nk = 1.3375 according to our simulations. The nk value to avoid the keratometric error ranged between 1.2984 and 1.3297. The following nkadj models were obtained: nkadj = -0.0064286r1c + 1.37688 (Gullstrand eye model) and nkadj = -0.0063804r1c + 1.37806 (Le Grand). The mean difference between Pkadj and Pc was 0.00 D, with limits of agreement of -0.45 and +0.46 D. This difference correlated significantly with the posterior corneal radius (r = -0.94, P < 0.01). The use of a single nk for estimating the corneal power in eyes that underwent a laser myopic refractive surgery can lead to significant errors. These errors can be minimized by using a variable nk dependent on r1c.

Effects of myopic spectacle correction and radial refractive gradient spectacles on peripheral refraction.

PubMed

Tabernero, Juan; Vazquez, Daniel; Seidemann, Anne; Uttenweiler, Dietmar; Schaeffel, Frank

2009-08-01

The recent observation that central refractive development might be controlled by the refractive errors in the periphery, also in primates, revived the interest in the peripheral optics of the eye. We optimized an eccentric photorefractor to measure the peripheral refractive error in the vertical pupil meridian over the horizontal visual field (from -45 degrees to 45 degrees ), with and without myopic spectacle correction. Furthermore, a newly designed radial refractive gradient lens (RRG lens) that induces increasing myopia in all radial directions from the center was tested. We found that for the geometry of our measurement setup conventional spectacles induced significant relative hyperopia in the periphery, although its magnitude varied greatly among different spectacle designs and subjects. In contrast, the newly designed RRG lens induced relative peripheral myopia. These results are of interest to analyze the effect that different optical corrections might have on the emmetropization process.

Wave aberrations in rhesus monkeys with vision-induced ametropias

PubMed Central

Ramamirtham, Ramkumar; Kee, Chea-su; Hung, Li-Fang; Qiao-Grider, Ying; Huang, Juan; Roorda, Austin; Smith, Earl L.

2007-01-01

The purpose of this study was to investigate the relationship between refractive errors and high-order aberrations in infant rhesus monkeys. Specifically, we compared the monochromatic wave aberrations measured with a Shack-Hartman wavefront sensor between normal monkeys and monkeys with vision-induced refractive errors. Shortly after birth, both normal monkeys and treated monkeys reared with optically induced defocus or form deprivation showed a decrease in the magnitude of high-order aberrations with age. However, the decrease in aberrations was typically smaller in the treated animals. Thus, at the end of the lens-rearing period, higher than normal amounts of aberrations were observed in treated eyes, both hyperopic and myopic eyes and treated eyes that developed astigmatism, but not spherical ametropias. The total RMS wavefront error increased with the degree of spherical refractive error, but was not correlated with the degree of astigmatism. Both myopic and hyperopic treated eyes showed elevated amounts of coma and trefoil and the degree of trefoil increased with the degree of spherical ametropia. Myopic eyes also exhibited a much higher prevalence of positive spherical aberration than normal or treated hyperopic eyes. Following the onset of unrestricted vision, the amount of high-order aberrations decreased in the treated monkeys that also recovered from the experimentally induced refractive errors. Our results demonstrate that high-order aberrations are influenced by visual experience in young primates and that the increase in high-order aberrations in our treated monkeys appears to be an optical byproduct of the vision-induced alterations in ocular growth that underlie changes in refractive error. The results from our study suggest that the higher amounts of wave aberrations observed in ametropic humans are likely to be a consequence, rather than a cause, of abnormal refractive development. PMID:17825347

More irregular eye shape in low myopia than in emmetropia.

PubMed

Tabernero, Juan; Schaeffel, Frank

2009-09-01

To improve the description of the peripheral eye shape in myopia and emmetropia by using a new method for continuous measurement of the peripheral refractive state. A scanning photorefractor was designed to record refractive errors in the vertical pupil meridian across the horizontal visual field (up to +/-45 degrees ). The setup consists of a hot mirror that continuously projects the infrared light from a photoretinoscope under different angles of eccentricity into the eye. The movement of the mirror is controlled by using two stepping motors. Refraction in a group of 17 emmetropic subjects and 11 myopic subjects (mean, -4.3 D; SD, 1.7) was measured without spectacle correction. For the analysis of eye shape, the refractive error versus the eccentricity angles was fitted with different polynomials (from second to tenth order). The new setup presents some important advantages over previous techniques: The subject does not have to change gaze during the measurements, and a continuous profile is obtained rather than discrete points. There was a significant difference in the fitting errors between the subjects with myopia and those with emmetropia. Tenth-order polynomials were required in myopic subjects to achieve a quality of fit similar to that in emmetropic subjects fitted with only sixth-order polynomials. Apparently, the peripheral shape of the myopic eye is more "bumpy." A new setup is presented for obtaining continuous peripheral refraction profiles. It was found that the peripheral retinal shape is more irregular even in only moderately myopic eyes, perhaps because the sclera lost some rigidity even at the early stage of myopia.

Corrective Techniques and Future Directions for Treatment of Residual Refractive Error Following Cataract Surgery

PubMed Central

Moshirfar, Majid; McCaughey, Michael V; Santiago-Caban, Luis

2015-01-01

Postoperative residual refractive error following cataract surgery is not an uncommon occurrence for a large proportion of modern-day patients. Residual refractive errors can be broadly classified into 3 main categories: myopic, hyperopic, and astigmatic. The degree to which a residual refractive error adversely affects a patient is dependent on the magnitude of the error, as well as the specific type of intraocular lens the patient possesses. There are a variety of strategies for resolving residual refractive errors that must be individualized for each specific patient scenario. In this review, the authors discuss contemporary methods for rectification of residual refractive error, along with their respective indications/contraindications, and efficacies. PMID:25663845

Corrective Techniques and Future Directions for Treatment of Residual Refractive Error Following Cataract Surgery.

PubMed

Moshirfar, Majid; McCaughey, Michael V; Santiago-Caban, Luis

2014-12-01

Postoperative residual refractive error following cataract surgery is not an uncommon occurrence for a large proportion of modern-day patients. Residual refractive errors can be broadly classified into 3 main categories: myopic, hyperopic, and astigmatic. The degree to which a residual refractive error adversely affects a patient is dependent on the magnitude of the error, as well as the specific type of intraocular lens the patient possesses. There are a variety of strategies for resolving residual refractive errors that must be individualized for each specific patient scenario. In this review, the authors discuss contemporary methods for rectification of residual refractive error, along with their respective indications/contraindications, and efficacies.

Ciliary Muscle Thickness in Anisometropia

PubMed Central

Kuchem, Mallory K; Sinnott, Loraine T; Kao, Chiu-Yen; Bailey, Melissa D

2014-01-01

Purpose The purpose of this study was to investigate the relationships between ciliary muscle thickness (CMT), refractive error, and axial length both across subjects and between the more and less myopic eyes of adults with anisometropia. Methods Both eyes of 29 adult subjects with at least 1.00 D of anisometropia were measured. Ciliary muscle thickness was measured at the maximum thickness (CMTMAX) and at 1.0 mm (CMT1), 2.0 mm (CMT2), and 3.0 mm (CMT3) posterior to the scleral spur, and also at the apical region (Apical CMTMAX = CMTMAX – CMT2, and Apical CMT1 = CMT1 – CMT2). Multilevel regression models were used to determine the relationship between the various CMT measures and cycloplegic refractive error or axial length, and to assess whether there are CMT differences between the more and less myopic eyes of an anisometropic adult. Results CMTMAX, CMT1, CMT2 and CMT3 were negatively associated with mean refractive error (all p ≤ 0.03), and the strongest association was in the posterior region (CMT2 and CMT3). Apical CMTMAX and Apical CMT1, however, were positively associated with mean refractive error (both p < 0.0001) across subjects. Within a subject, i.e., comparing the two anisometropic eyes, there was no statistically significant difference in CMT in any region. Conclusions Similar to previous studies, across anisometropic subjects, a thicker posterior region of the ciliary muscle (CMT2 and CMT3) was associated with increased myopic refractive error. Conversely, shorter, more hyperopic eyes tended to have thicker anterior, apical fiber portions of their ciliary muscle (Apical CMTMAX and Apical CMT1). There was no difference between the two eyes for any CMT measurement, indicating that in anisometropia, an eye can grow longer and more myopic than its fellow eye without resulting in an increase in CMT. PMID:24100479

Topography-modified refraction (TMR): adjustment of treated cylinder amount and axis to the topography versus standard clinical refraction in myopic topography-guided LASIK.

PubMed

Kanellopoulos, Anastasios John

2016-01-01

To evaluate the safety, efficacy, and contralateral eye comparison of topography-guided myopic LASIK with two different refraction treatment strategies. Private clinical ophthalmology practice. A total of 100 eyes (50 patients) in consecutive cases of myopic topography-guided LASIK procedures with the same refractive platform (FS200 femtosecond and EX500 excimer lasers) were randomized for treatment as follows: one eye with the standard clinical refraction (group A) and the contralateral eye with the topographic astigmatic power and axis (topography-modified treatment refraction; group B). All cases were evaluated pre- and post-operatively for the following parameters: refractive error, best corrected distance visual acuity (CDVA), uncorrected distance visual acuity (UDVA), topography (Placido-disk based) and tomography (Scheimpflug-image based), wavefront analysis, pupillometry, and contrast sensitivity. Follow-up visits were conducted for at least 12 months. Mean refractive error was -5.5 D of myopia and -1.75 D of astigmatism. In group A versus group B, respectively, the average UDVA improved from 20/200 to 20/20 versus 20/16; post-operative CDVA was 20/20 and 20/13.5; 1 line of vision gained was 27.8% and 55.6%; and 2 lines of vision gained was 5.6% and 11.1%. In group A, 27.8% of eyes had over -0.50 diopters of residual refractive astigmatism, in comparison to 11.7% in group B ( P <0.01). The residual percentages in both groups were measured with refractive astigmatism of more than -0.5 diopters. Topography-modified refraction (TMR): topographic adjustment of the amount and axis of astigmatism treated, when different from the clinical refraction, may offer superior outcomes in topography-guided myopic LASIK. These findings may change the current clinical paradigm of the optimal subjective refraction utilized in laser vision correction.

Topography-modified refraction (TMR): adjustment of treated cylinder amount and axis to the topography versus standard clinical refraction in myopic topography-guided LASIK

PubMed Central

Kanellopoulos, Anastasios John

2016-01-01

Purpose To evaluate the safety, efficacy, and contralateral eye comparison of topography-guided myopic LASIK with two different refraction treatment strategies. Setting Private clinical ophthalmology practice. Patients and methods A total of 100 eyes (50 patients) in consecutive cases of myopic topography-guided LASIK procedures with the same refractive platform (FS200 femtosecond and EX500 excimer lasers) were randomized for treatment as follows: one eye with the standard clinical refraction (group A) and the contralateral eye with the topographic astigmatic power and axis (topography-modified treatment refraction; group B). All cases were evaluated pre- and post-operatively for the following parameters: refractive error, best corrected distance visual acuity (CDVA), uncorrected distance visual acuity (UDVA), topography (Placido-disk based) and tomography (Scheimpflug-image based), wavefront analysis, pupillometry, and contrast sensitivity. Follow-up visits were conducted for at least 12 months. Results Mean refractive error was −5.5 D of myopia and −1.75 D of astigmatism. In group A versus group B, respectively, the average UDVA improved from 20/200 to 20/20 versus 20/16; post-operative CDVA was 20/20 and 20/13.5; 1 line of vision gained was 27.8% and 55.6%; and 2 lines of vision gained was 5.6% and 11.1%. In group A, 27.8% of eyes had over −0.50 diopters of residual refractive astigmatism, in comparison to 11.7% in group B (P<0.01). The residual percentages in both groups were measured with refractive astigmatism of more than −0.5 diopters. Conclusion Topography-modified refraction (TMR): topographic adjustment of the amount and axis of astigmatism treated, when different from the clinical refraction, may offer superior outcomes in topography-guided myopic LASIK. These findings may change the current clinical paradigm of the optimal subjective refraction utilized in laser vision correction. PMID:27843292

Relative peripheral hyperopic defocus alters central refractive development in infant monkeys

PubMed Central

Smith, Earl L.; Hung, Li-Fang; Huang, Juan

2009-01-01

Understanding the role of peripheral defocus on central refractive development is critical because refractive errors can vary significantly with eccentricity and peripheral refractions have been implicated in the genesis of central refractive errors in humans. Two rearing strategies were used to determine whether peripheral hyperopia alters central refractive development in rhesus monkeys. In intact eyes, lens-induced relative peripheral hyperopia produced central axial myopia. Moreover, eliminating the fovea by laser photoablation did not prevent compensating myopic changes in response to optically imposed hyperopia. These results show that peripheral refractive errors can have a substantial impact on central refractive development in primates. PMID:19632261

Studies of intrastromal corneal ring segments for the correction of low to moderate myopic refractive errors.

PubMed Central

Schanzlin, D J

1999-01-01

PURPOSE: Intrastromal corneal ring segments (ICRS) were investigated for safety and reliability in the correction of low to moderate myopic refractive errors. METHODS: Initially, 74 patients with spherical equivalent refractive errors between -1.00 and -4.25 diopters (D) received the ICRS in 1 eye. After 6 months, 51 of these patients received the ICRS in the contralateral eye. The total number of eyes investigated was 125. The outcome measures were uncorrected and best-corrected visual acuity, predictability and stability of the refraction, refractive astigmatism, contrast sensitivity, and endothelial cell morphology. RESULTS: The 89 eyes with 12-month follow-up showed significant improvement with uncorrected visual acuities of 20/16 or better in 37%, 20/20 or better in 62%, and 20/40 or better in 97%. Cycloplegic refraction spherical equivalents showed that 68% of the eyes were within +/- 0.50 D and 90% within +/- 1.00 D of the intended correction. Refractive stability was present by 3 months after the surgery. Only 1 patients had a loss greater than 2 lines or 10 letters of best spectacle-corrected visual acuity, but the patient's acuity was 20/20. Refractive cylinder, contrast sensitivity, and endothelial cell morphology were not adversely affected. The ICRS was removed from the eyes of 6 patients. Three removals were prompted by glare and double images occurring at night; 3 were for nonmedical reasons. All patients returned to within +/- 1.00 D of their preoperative refractive spherical equivalent, and no patients lost more than 1 line of best corrected visual acuity by 3 months after ICRS removal. CONCLUSION: The ICRS safely and reliably corrects myopic refractive errors between -1.00 and -4.50 D. Images FIGURE 1 FIGURE 2 FIGURE 3 FIGURE 6 FIGURE 7 FIGURE 8 FIGURE 9 FIGURE 10 FIGURE 11 FIGURE 12 PMID:10703146

Ocular Biometrics of Myopic Eyes With Narrow Angles.

PubMed

Chong, Gabriel T; Wen, Joanne C; Su, Daniel Hsien-Wen; Stinnett, Sandra; Asrani, Sanjay

2016-02-01

The purpose of this study was to compare the ocular biometrics between myopic patients with and without narrow angles. Patients with a stable myopic refraction (myopia worse than -1.00 D spherical equivalent) were prospectively recruited. Angle status was assessed using gonioscopy and biometric measurements were performed using an anterior segment optical coherence tomography and an IOLMaster. A total of 29 patients (58 eyes) were enrolled with 13 patients (26 eyes) classified as having narrow angles and 16 patients (32 eyes) classified as having open angles. Baseline demographics of age, sex, and ethnicity did not differ significantly between the 2 groups. The patients with narrow angles were on average older than those with open angles but the difference did not reach statistical significance (P=0.12). The central anterior chamber depth was significantly less in the eyes with narrow angles (P=0.05). However, the average lens thickness, although greater in the eyes with narrow angles, did not reach statistical significance (P=0.10). Refractive error, axial lengths, and iris thicknesses did not differ significantly between the 2 groups (P=0.32, 0.47, 0.15). Narrow angles can occur in myopic eyes. Routine gonioscopy is therefore recommended for all patients regardless of refractive error.

Temporal integration characteristics of the axial and choroidal responses to myopic defocus induced by prior form deprivation versus positive spectacle lens wear in chickens.

PubMed

Nickla, Debora L; Sharda, Vandhana; Troilo, David

2005-04-01

In chicks, the temporal response characteristics to form deprivation and to spectacle lens wear (myopic and hyperopic defocus) show essential differences, suggesting that the emmetropization system "weights" the visual signals differently. To further explore how the eye integrates opposing visual signals, we examined the responses to myopic defocus induced by prior form deprivation vs. that induced by positive spectacle lenses, in both cases alternating with form deprivation. Three experimental paradigms were used: 1) Form deprivation was induced by monocular occluders for 7 days. Over the subsequent 7 days, the occluders were removed daily for 12 hours (n = 13), 4 hours (n = 7), 2 hours (n = 7), or 0 hours (n = 6). 2) Birds were form-deprived on day 12. Over the subsequent 7 days, occluders were replaced with a +10 D lens for 2 hours per day (n = 13). 3) Starting at day 11, a +10 D lens was placed over one eye for 2 hours (n = 13), 3 hours (n = 5), or 6 hours (n = 10) per day and were otherwise untreated. Ocular dimensions were measured with high-frequency A-scan ultrasonography; refractive errors were measured by streak retinoscopy at various intervals. In recovering eyes, 2 hours per day of myopic defocus was as effective as 12 hours at inducing refractive and axial recovery (change in refractive error: +10 D vs. +13 D, respectively). By contrast, 2 hours of lens-induced defocus (alternating with form deprivation) was not sufficient to induce refractive or axial compensation (change in refractive error: -1.7 D). When myopic defocus alternated with unrestricted vision, 6 hours per day were sufficient to induce nearly full compensation (2 hours vs. 6 hours: 4.4 D vs. 8.2 D; p < 0.0005). Choroids showed rapid increases in thickness to the daily episodes of myopic defocus; these resulted in "long-term" thickness changes in recovering eyes and eyes wearing lenses for 3 or 6 hours per day. The response to myopic defocus induced by prior form deprivation is more robust than the response induced by positive lenses, suggesting that the underlying mechanisms differ. Presumably, this difference is related to the size of the eye at the onset. Compensatory decreases in growth rate occur without full compensatory choroidal thickening.

Effects of local myopic defocus on refractive development in monkeys.

PubMed

Smith, Earl L; Hung, Li-Fang; Huang, Juan; Arumugam, Baskar

2013-11-01

Visual signals that produce myopia are mediated by local, regionally selective mechanisms. However, little is known about spatial integration for signals that slow eye growth. The purpose of this study was to determine whether the effects of myopic defocus are integrated in a local manner in primates. Beginning at 24 ± 2 days of age, seven rhesus monkeys were reared with monocular spectacles that produced 3 diopters (D) of relative myopic defocus in the nasal visual field of the treated eye but allowed unrestricted vision in the temporal field (NF monkeys). Seven monkeys were reared with monocular +3 D lenses that produced relative myopic defocus across the entire field of view (FF monkeys). Comparison data from previous studies were available for 11 control monkeys, 8 monkeys that experienced 3 D of hyperopic defocus in the nasal field, and 6 monkeys exposed to 3 D of hyperopic defocus across the entire field. Refractive development, corneal power, and axial dimensions were assessed at 2- to 4-week intervals using retinoscopy, keratometry, and ultrasonography, respectively. Eye shape was assessed using magnetic resonance imaging. In response to full-field myopic defocus, the FF monkeys developed compensating hyperopic anisometropia, the degree of which was relatively constant across the horizontal meridian. In contrast, the NF monkeys exhibited compensating hyperopic changes in refractive error that were greatest in the nasal visual field. The changes in the pattern of peripheral refractions in the NF monkeys reflected interocular differences in vitreous chamber shape. As with form deprivation and hyperopic defocus, the effects of myopic defocus are mediated by mechanisms that integrate visual signals in a local, regionally selective manner in primates. These results are in agreement with the hypothesis that peripheral vision can influence eye shape and potentially central refractive error in a manner that is independent of central visual experience.

Hyperopic photorefractive keratectomy and central islands

NASA Astrophysics Data System (ADS)

Gobbi, Pier Giorgio; Carones, Francesco; Morico, Alessandro; Vigo, Luca; Brancato, Rosario

1998-06-01

We have evaluated the refractive evolution in patients treated with yhyperopic PRK to assess the extent of the initial overcorrection and the time constant of regression. To this end, the time history of the refractive error (i.e. the difference between achieved and intended refractive correction) has been fitted by means of an exponential statistical model, giving information characterizing the surgical procedure with a direct clinical meaning. Both hyperopic and myopic PRk procedures have been analyzed by this method. The analysis of the fitting model parameters shows that hyperopic PRK patients exhibit a definitely higher initial overcorrection than myopic ones, and a regression time constant which is much longer. A common mechanism is proposed to be responsible for the refractive outcomes in hyperopic treatments and in myopic patients exhibiting significant central islands. The interpretation is in terms of superhydration of the central cornea, and is based on a simple physical model evaluating the amount of centripetal compression in the apical cornea.

Near work, outdoor activity, and their association with refractive error.

PubMed

Lin, Zhong; Vasudevan, Balamurali; Jhanji, Vishal; Mao, Guang Yun; Gao, Tie Ying; Wang, Feng Hua; Rong, Shi Song; Ciuffreda, Kenneth J; Liang, Yuan Bo

2014-04-01

To assess the relationship between near work, outdoor activity, and refractive error in schoolchildren in Beijing. The Beijing Myopia Progression Study is a hospital-based myopia study, in which 386 students from primary (aged 6 to 12 years) and secondary (aged 13 to 17 years) schools in the inner city of Beijing were enrolled. Cycloplegic refraction and a detailed questionnaire probing near, intermediate, and distance visual activities were completed. Three hundred seventy (95.9%) of 386 students with complete cycloplegic autorefraction and myopia questionnaire data were enrolled in this study. Children with more near work time did not exhibit a significantly more myopic refraction in both the primary and secondary school levels after adjusting for the children's gender, outdoor activity time, and average parental refractive error. A significant association between outdoor activity time (in hours per day) and the children's spherical equivalent (in diopters) was found in the primary school students (β = 0.27, p = 0.03) but not in the secondary school students (β = 0.04, p = 0.70) after adjusting for similar confounders. The time spent on outdoor sports and outdoor leisure in the primary school students was also significantly associated with the children's spherical equivalent (β = 0.46, p = 0.04 and β = 0.31, p = 0.02, respectively). Primary school students with more time outdoors exhibited relatively less myopic refraction than their peers (ptrend = 0.0003), but this relation was not demonstrated in the secondary school children (ptrend = 0.53) after adjusting for similar confounders. Higher levels of outdoor activity were associated with less myopic refraction in primary school students in the inner city of Beijing. Near work activity was not found to be associated with refraction at either school level.

Delayed visual attention caused by high myopic refractive error.

PubMed

Winges, Kimberly M; Zarpellon, Ursula; Hou, Chuan; Good, William V

2005-06-01

Delayed visual maturation (DVM) is usually a retrospective diagnosis given to infants who are born with no or poor visually-directed behavior, despite normal acuity on objective testing, but who recover months later. This condition can be organized into several types based on associated neurodevelopmental or ocular findings, but the etiology of DVM is probably complex and involves multiple possible origins. Here we report two infants who presented with delayed visual maturation (attention). They were visually unresponsive at birth but were later found to have high myopic errors. Patient 1 had -4 D right eye, -5 D left eye. Patient 2 had -9 D o.u. Upon spectacle correction at 5 and 4 months, respectively, both infants immediately displayed visually-directed behavior, suggesting that a high refractive error was the cause of inattention in these patients. These findings could add to knowledge surrounding DVM and the diagnosis of apparently blind infants. Findings presented here also indicate the importance of prompt refractive error measurement in such cases.

Do Peripheral Refraction and Aberration Profiles Vary with the Type of Myopia? - An Illustration Using a Ray-Tracing Approach

PubMed Central

Bakaraju, Ravi C.; Ehrmann, Klaus; Papas, Eric B.; Ho, Arthur

2010-01-01

Purpose Myopia is considered to be the most common refractive error occurring in children and young adults, around the world. Motivated to elucidate how the process of emmetropization is disrupted, potentially causing myopia and its progression, researchers have shown great interest in peripheral refraction. This study assessed the effect of the myopia type, either refractive or axial, on peripheral refraction and aberration profiles. Methods Using customized schematic eye models for myopia in a ray tracing algorithm, peripheral aberrations, including the refractive error, were calculated as a function of myopia type. Results In all the selected models, hyperopic shifts in the mean spherical equivalent (MSE) component were found whose magnitude seemed to be largely dependent on the field angle. The MSE profiles showed larger hyperopic shifts for the axial type of myopic models than the refractive ones and were evident in -4 and -6 D prescriptions. Additionally, greater levels of astigmatic component (J180) were also seen in axial-length-dependent models, while refractive models showed higher levels of spherical aberration and coma. Conclusion This study has indicated that myopic eyes with primarily an axial component may have a greater risk of progression than their refractive counterparts albeit with the same degree of refractive error. This prediction emerges from the presented theoretical ray tracing model and, therefore, requires clinical confirmation.

Optical and Biometric Characteristics of Anisomyopia in Human Adults

PubMed Central

Tian, Yibin; Tarrant, Janice; Wildsoet, Christine F.

2011-01-01

Purpose To investigate the role of higher order optical aberrations and thus retinal image degradation in the development of myopia, through the characterization of anisomyopia in human adults in terms of their optical and biometric characteristics. Methods The following data were collected from both eyes of fifteen young adult anisometropic myopes and sixteen isometropic myopes: subjective and objective refractive errors, corneal power and shape, monochromatic optical aberrations, anterior chamber depth, lens thickness, vitreous chamber depth, and best corrected visual acuity. Monochromatic aberrations were analyzed in terms of their higher order components, and further analyzed in terms of 31 optical quality metrics. Interocular differences for the two groups (anisomyopes vs. isomyopes) were compared and the relationship between measured ocular parameters and refractive errors also analyzed across all eyes. Results As expected, anisomyopes and isomyopes differed significantly in terms of interocular differences in vitreous chamber depth, axial length and refractive error. However, interocular differences in other optical properties showed no significant intergroup differences. Overall, higher myopia was associated with deeper anterior and vitreous chambers, higher astigmatism, more prolate corneas, and more positive spherical aberration. Other measured optical and biometric parameters were not significantly correlated with spherical refractive error, although some optical quality metrics and corneal astigmatism were significantly correlated with refractive astigmatism. Conclusions An optical cause for anisomyopia related to increased higher order aberrations is not supported by our data. Corneal shape changes and increased astigmatism in more myopic eyes may be a by-product of the increased anterior chamber growth in these eyes; likewise, the increased positive spherical aberration in more myopic eyes may be a product of myopic eye growth. PMID:21797915

Eye laterality: a comprehensive analysis in refractive surgery candidates.

PubMed

Linke, Stephan J; Druchkiv, Vasyl; Steinberg, Johannes; Richard, Gisbert; Katz, Toam

2013-08-01

To explore eye laterality (higher refractive error in one eye) and its association with refractive state, spherical/astigmatic anisometropia, age and sex in refractive surgery candidates. Medical records of 12 493 consecutive refractive surgery candidates were filtered. Refractive error (subjective and cycloplegic) was measured in each subject and correlated with eye laterality. Only subjects with corrected distance visual acuity (CDVA) of >20/22 in each eye were enrolled to exclude amblyopia. Associations between eye laterality and refractive state were analysed by means of t-test, chi-squared test, Spearman's correlation and multivariate logistic regression analysis, respectively. There was no statistically significant difference in spherical equivalent between right (-3.47 ± 2.76 D) and left eyes (-3.47 ± 2.76 D, p = 0.510; Pearson's r = 0.948, p < 0.001). Subgroup analysis revealed (I) right eye laterality for anisometropia >2.5 D in myopic (-5.64 ± 2.5 D versus -4.92 ± 2.6 D; p = 0.001) and in hyperopic (4.44 ± 1.69 D versus 3.04 ± 1.79 D; p = 0.025) subjects, (II) a tendency for left eye cylindrical laterality in myopic subjects, and (III) myopic male subjects had a higher prevalence of left eye laterality. (IV) Age did not show any significant impact on laterality. Over the full refractive spectrum, this study confirmed previously described strong interocular refractive correlation but revealed a statistically significant higher rate of right eye laterality for anisometropia >2.5 D. In general, our results support the use of data from one eye only in studies of ocular refraction. © 2013 The Authors. Acta Ophthalmologica © 2013 Acta Ophthalmologica Scandinavica Foundation.

The effect of fractal contact lenses on peripheral refraction in myopic model eyes.

PubMed

Rodriguez-Vallejo, Manuel; Benlloch, Josefa; Pons, Amparo; Monsoriu, Juan A; Furlan, Walter D

2014-12-01

To test multizone contact lenses in model eyes: Fractal Contact Lenses (FCLs), designed to induce myopic peripheral refractive error (PRE). Zemax ray-tracing software was employed to simulate myopic and accommodation-dependent model eyes fitted with FCLs. PRE, defined in terms of mean sphere M and 90°-180° astigmatism J180, was computed at different peripheral positions, ranging from 0 to 35° in steps of 5°, and for different pupil diameters (PDs). Simulated visual performance and changes in the PRE were also analyzed for contact lens decentration and model eye accommodation. For comparison purposes, the same simulations were performed with another commercially available contact lens designed for the same intended use: the Dual Focus (DF). PRE was greater with FCL than with DF when both designs were tested for a 3.5 mm PD, and with and without decentration of the lenses. However, PRE depended on PD with both multizone lenses, with a remarkable reduction of the myopic relative effect for a PD of 5.5 mm. The myopic PRE with contact lenses decreased as the myopic refractive error increased, but this could be compensated by increasing the power of treatment zones. A peripheral myopic shift was also induced by the FCLs in the accommodated model eye. In regard to visual performance, a myopia under-correction with reference to the circle of least confusion was obtained in all cases for a 5.5 mm PD. The ghost images, generated by treatment zones of FCL, were dimmer than the ones produced with DF lens of the same power. FCLs produce a peripheral myopic defocus without compromising central vision in photopic conditions. FCLs have several design parameters that can be varied to obtain optimum results: lens diameter, number of zones, addition and asphericity; resulting in a very promising customized lens for the treatment of myopia progression.

The Prevalence of Open-Angle Glaucoma by Age in Myopia: The Korea National Health and Nutrition Examination Survey.

PubMed

Shim, Seong Hee; Sung, Kyung Rim; Kim, Joon Mo; Kim, Hyun Tae; Jeong, Jinho; Kim, Chan Yun; Lee, Mi Yeon; Park, Ki Ho

2017-01-01

To investigate the prevalence of open-angle glaucoma (OAG) in myopia by age. A cross-sectional study using a stratified, multistage, probability cluster survey. Participants in the Korean National Health and Nutrition Examination Survey between 2010 and 2011 were included. A standardized protocol was used to interview every participant and perform comprehensive ophthalmic examinations. Glaucoma was diagnosed according to the International Society of Geographical and Epidemiological Ophthalmology (ISGEO) criteria. After adjusting for age and sex, there was a positive correlation between OAG prevalence and increasing myopic refractive error except in participants with hyperopia. Younger participants with higher myopic refractive error had higher OAG prevalence than older participants with lower myopic refractive error. Participants with high myopia (OR 3.90, 95% confidence interval (CI) 2.30-6.59) had significantly greater age- and sex-adjusted odd ratios (ORs) than did those with emmetropia who were younger than 60 years. These data suggest that OAG develops earlier in participants with high myopia than in others. There was a high prevalence of OAG in participants with high myopia, even in those 19-29 years of age. Therefore, OAG screening should be performed earlier in participants with high myopia than is suggested by traditional guidelines.

Refractive error at birth and its relation to gestational age.

PubMed

Varughese, Sara; Varghese, Raji Mathew; Gupta, Nidhi; Ojha, Rishikant; Sreenivas, V; Puliyel, Jacob M

2005-06-01

The refractive status of premature infants is not well studied. This study was done to find the norms of refractive error in newborns at different gestational ages. One thousand two hundred three (1203) eyes were examined for refractive error by streak retinoscopy within the first week of life between June 2001 and September 2002. Tropicamide eye drops (0.8%) with phenylephrine 0.5% were used to achieve cycloplegia and mydriasis. The refractive error was measured in the vertical and horizontal meridia in both eyes and was recorded to the nearest dioptre (D). The neonates were grouped in five gestational age groups ranging from 24 weeks to 43 weeks. Extremely preterm babies were found to be myopic with a mean MSE (mean spherical equivalent) of -4.86 D. The MSE was found to progressively decrease (become less myopic) with increasing gestation and was +2.4 D at term. Astigmatism of more than 1 D spherical equivalent was seen in 67.8% of the eyes examined. Among newborns with > 1 D of astigmatism, the astigmatism was with-the-rule (vertical meridian having greater refractive power than horizontal) in 85% and against-the-rule in 15%. Anisometropia of more than 1 D spherical equivalent was seen in 31% babies. Term babies are known to be hypermetropic, and preterm babies with retinopathy of prematurity (ROP) are known to have myopia. This study provides data on the mean spherical equivalent, the degree of astigmatism, and incidence of anisometropia at different gestational ages. This is the largest study in world literature looking at refractive errors at birth against gestational age. It should help understand the norms of refractive errors in preterm babies.

[Refractive errors as causes of visual impairment in children from public schools of the Botucatu region - SP].

PubMed

Oliveira, Claudia Akemi Shiratori de; Hisatomi, Kenia Scrocaro; Leite, Cristiano Pinheiro; Schellini, Silvana Artioli; Padovani, Carlos Roberto; Padovani, Carlos Roberto Pereira

2009-01-01

To evaluate the refractive errors as cause of visual impairment in school children from the Botucatu region. A sectional study was conducted evaluating preschool and elementary school students, according to gender, refractive error, visual acuity and treatment. Four thousand six hundred and twenty-three (4,623) children were submitted to visual acuity evaluation and 8.1% of them were submitted to complete ocular examination. There were 63.2% hyperopic astigmatism, 15.7% myopic astigmatism, 12.5% astigmatism, 4.9% hyperopia and 3.7% myopia. Corrective lenses were prescribed for 48.7% of the evaluated children. The most frequent refractive error was hyperopic astigmatism and 50% of the children received treatment. The frequency of refractive errors was 3.9% of the studied population.

Reduced vision in highly myopic eyes without ocular pathology: the ZOC-BHVI high myopia study.

PubMed

Jong, Monica; Sankaridurg, Padmaja; Li, Wayne; Resnikoff, Serge; Naidoo, Kovin; He, Mingguang

2018-01-01

The aim was to investigate the relationship of the magnitude of myopia with visual acuity in highly myopic eyes without ocular pathology. Twelve hundred and ninety-two highly myopic eyes (up to -6.00 DS both eyes, no astigmatic cut-off) with no ocular pathology from the ZOC-BHVI high myopia study in China, had cycloplegic refraction, followed by subjective refraction and visual acuities and axial length measurement. Two logistic regression models were undertaken to test the association of age, gender, refractive error, axial length and parental myopia with reduced vision. Mean group age was 19.0 ± 8.6 years; subjective spherical equivalent refractive error was -9.03 ± 2.73 D; objective spherical equivalent refractive error was -8.90 ± 2.60 D and axial length was 27.0 ± 1.3 mm. Using visual acuity, 82.4 per cent had normal vision, 16.0 per cent had mildly reduced vision, 1.2 per cent had moderately reduced vision, 0.3 per cent had severely reduced vision and no subjects were blind. The percentage with reduced vision increased with spherical equivalent to 74.5 per cent from -15.00 to -39.99 D, axial length to 67.7 per cent of eyes from 30.01 to 32.00 mm and age to 22.9 per cent of those 41 years and over. Spherical equivalent and axial length were significantly associated with reduced vision (p < 0.0001). Age and parental myopia were not significantly associated with reduced vision. Gender was significant for one model (p = 0.04). Mildly reduced vision is common in high myopia without ocular pathology and is strongly correlated with greater magnitudes of refractive error and axial length. Better understanding is required to minimise reduced vision in high myopes. © 2017 Optometry Australia.

Effect of refractive error on temperament and character properties.

PubMed

Kalkan Akcay, Emine; Canan, Fatih; Simavli, Huseyin; Dal, Derya; Yalniz, Hacer; Ugurlu, Nagihan; Gecici, Omer; Cagil, Nurullah

2015-01-01

To determine the effect of refractive error on temperament and character properties using Cloninger's psychobiological model of personality. Using the Temperament and Character Inventory (TCI), the temperament and character profiles of 41 participants with refractive errors (17 with myopia, 12 with hyperopia, and 12 with myopic astigmatism) were compared to those of 30 healthy control participants. Here, temperament comprised the traits of novelty seeking, harm-avoidance, and reward dependence, while character comprised traits of self-directedness, cooperativeness, and self-transcendence. Participants with refractive error showed significantly lower scores on purposefulness, cooperativeness, empathy, helpfulness, and compassion (P<0.05, P<0.01, P<0.05, P<0.05, and P<0.01, respectively). Refractive error might have a negative influence on some character traits, and different types of refractive error might have different temperament and character properties. These personality traits may be implicated in the onset and/or perpetuation of refractive errors and may be a productive focus for psychotherapy.

Corneal and crystalline lens dimensions before and after myopia onset.

PubMed

Mutti, Donald O; Mitchell, G Lynn; Sinnott, Loraine T; Jones-Jordan, Lisa A; Moeschberger, Melvin L; Cotter, Susan A; Kleinstein, Robert N; Manny, Ruth E; Twelker, J Daniel; Zadnik, Karla

2012-03-01

To describe corneal and crystalline lens dimensions before, during, and after myopia onset compared with age-matched emmetropic values. Subjects were 732 children aged 6 to 14 years who became myopic and 596 emmetropic children participating between 1989 and 2007 in the Collaborative Longitudinal Evaluation of Ethnicity and Refractive Error Study. Refractive error was measured using cycloplegic autorefraction, corneal power using a hand-held autokeratometer, crystalline lens parameters using video-based phakometry, and vitreous chamber depth (VCD) using A-scan ultrasonography. Corneal and crystalline lens parameters in children who became myopic were compared with age-, gender-, and ethnicity-matched model estimates of emmetrope values annually from 5 years before through 5 years after the onset of myopia. The comparison was made without and then with statistical adjustment of emmetrope component values to compensate for the effects of longer VCDs in children who became myopic. Before myopia onset, the crystalline lens thinned, flattened, and lost power at similar rates for emmetropes and children who became myopic. The crystalline lens stopped thinning, flattening, and losing power within ±1 year of onset in children who became myopic compared with emmetropes statistically adjusted to match the longer VCDs of children who became myopic. In contrast, the cornea was only slightly steeper in children who became myopic compared with emmetropes (<0.25 D) and underwent little change across visits. Myopia onset is characterized by an abrupt loss of compensatory changes in the crystalline lens that continue in emmetropes throughout childhood axial elongation. The mechanism responsible for this decoupling remains speculative but might include restricted equatorial growth from internal mechanical factors.

Nature versus nurture: A systematic approach to elucidate gene-environment interactions in the development of myopic refractive errors.

PubMed

Miraldi Utz, Virginia

2017-01-01

Myopia is the most common eye disorder and major cause of visual impairment worldwide. As the incidence of myopia continues to rise, the need to further understand the complex roles of molecular and environmental factors controlling variation in refractive error is of increasing importance. Tkatchenko and colleagues applied a systematic approach using a combination of gene set enrichment analysis, genome-wide association studies, and functional analysis of a murine model to identify a myopia susceptibility gene, APLP2. Differential expression of refractive error was associated with time spent reading for those with low frequency variants in this gene. This provides support for the longstanding hypothesis of gene-environment interactions in refractive error development.

Comparison of two techniques of marking the horizontal axis during excimer laser keratorefractive surgery for myopic astigmatism.

PubMed

Burka, Jenna M; Bower, Kraig S; Cute, David L; Stutzman, Richard D; Subramanian, Prem S; Rabin, Jeff C

2005-04-01

To compare two methods of limbal marking used during laser refractive surgery for myopic astigmatism. Retrospective chart review. Forty-two eyes of 42 patients who underwent photorefractive keratectomy (PRK) or laser-assisted in-situ keratomileusis (LASIK) for myopic astigmatism were marked preoperatively to identify the horizontal axis. In 18 eyes, marks were placed at the slit lamp (SL) with the slit beam set at 180 degrees as a reference. In 24 eyes, marks were placed in the laser room (LR) immediately before reclining under the laser. All treatments were performed with the Alcon LADARVision excimer laser system. Vector analysis of postoperative cylinder and reduction in cylinder and uncorrected and best-corrected visual acuity were evaluated for both groups. The mean postoperative magnitude of error was -0.19 +/- 0.44 diopters for the LR group and -0.09 +/- 0.42 diopters for the SL group (P = .439, NS). Both groups had a mean angle of error indicating an overall counterclockwise rotation of axis with an angle of error of 6.3 +/- 8.7 degrees for the LR group and 8.0 +/- 10.2 degrees for the SL group (P = .562, NS). We found no significant difference in outcomes with an overall trend toward undercorrection of cylinder in both groups, leaving room for improvement after refractive surgery for myopic astigmatism.

Effects of Head-Mounted Display on the Oculomotor System and Refractive Error in Normal Adolescents.

PubMed

Ha, Suk-Gyu; Na, Kun-Hoo; Kweon, Il-Joo; Suh, Young-Woo; Kim, Seung-Hyun

2016-07-01

To investigate the clinical effects of head-mounted display on the refractive error and oculomotor system in normal adolescents. Sixty volunteers (age: 13 to 18 years) watched a three-dimensional movie and virtual reality application of head-mounted display for 30 minutes. The refractive error (diopters [D]), angle of deviation (prism diopters [PD]) at distance (6 m) and near (33 cm), near point of accommodation, and stereoacuity were measured before, immediately after, and 10 minutes after watching the head-mounted display. The refractive error was presented as spherical equivalent (SE). Refractive error was measured repeatedly after every 10 minutes when a myopic shift greater than 0.15 D was observed after watching the head-mounted display. The mean age of the participants was 14.7 ± 1.3 years and the mean SE before watching head-mounted display was -3.1 ± 2.6 D. One participant in the virtual reality application group was excluded due to motion sickness and nausea. After 30 minutes of watching the head-mounted display, the SE, near point of accommodation, and stereoacuity in both eyes did not change significantly (all P > .05). Immediately after watching the head-mounted display, esophoric shift was observed (0.6 ± 1.5 to 0.2 ± 1.5 PD), although it was not significant (P = .06). Transient myopic shifts of 17.2% to 30% were observed immediately after watching the head-mounted display in both groups, but recovered fully within 40 minutes after watching the head-mounted display. There were no significant clinical effects of watching head-mounted display for 30 minutes on the normal adolescent eye. Transient changes in refractive error and binocular alignment were noted, but were not significant. [J Pediatr Ophthalmol Strabismus. 2016;53(4):238-245.]. Copyright 2016, SLACK Incorporated.

Physiological pseudomyopia.

PubMed

Jones, R

1990-08-01

Objective refraction through plus fogging lenses and base-in prisms revealed that normally accommodation is not completely relaxed when the stimulus to accommodation is zero. The myopic shift in the refractive error due to this focus error of accommodation was defined as physiological pseudomyopia. Two previously established features of accommodation are responsible for this behavior: (1) accommodation acts as a proportional control system for steady-state responses; and (2) the rest focus of accommodation is nonzero. It is proposed that the hyperopic shift in refraction observed in cycloplegia is the result of elimination of physiological pseudomyopia.

Prevalence of refraction errors and color blindness in heavy vehicle drivers.

PubMed

Erdoğan, Haydar; Ozdemir, Levent; Arslan, Seher; Cetin, Ilhan; Ozeç, Ayşe Vural; Cetinkaya, Selma; Sümer, Haldun

2011-01-01

To investigate the frequency of eye disorders in heavy vehicle drivers. A cross-sectional type study was conducted between November 2004 and September 2006 in 200 driver and 200 non-driver persons. A complete ophthalmologic examination was performed, including visual acuity, and dilated examination of the posterior segment. We used the auto refractometer for determining refractive errors. According to eye examination results, the prevalence of the refractive error was 21.5% and 31.3% in study and control groups respectively (P<0.05). The most common type of refraction error in the study group was myopic astigmatism (8.3%) while in the control group simple myopia (12.8%). Prevalence of dyschromatopsia in the rivers, control group and total group was 2.2%, 2.8% and 2.6% respectively. A considerably high number of drivers are in lack of optimal visual acuity. Refraction errors in drivers may impair the traffic security.

Prevalence of refraction errors and color blindness in heavy vehicle drivers

PubMed Central

Erdoğan, Haydar; Özdemir, Levent; Arslan, Seher; Çetin, Ilhan; Özeç, Ayşe Vural; Çetinkaya, Selma; Sümer, Haldun

2011-01-01

AIM To investigate the frequency of eye disorders in heavy vehicle drivers. METHODS A cross-sectional type study was conducted between November 2004 and September 2006 in 200 driver and 200 non-driver persons. A complete ophthalmologic examination was performed, including visual acuity, and dilated examination of the posterior segment. We used the auto refractometer for determining refractive errors. RESULTS According to eye examination results, the prevalence of the refractive error was 21.5% and 31.3% in study and control groups respectively (P<0.05). The most common type of refraction error in the study group was myopic astigmatism (8.3%) while in the control group simple myopia (12.8%). Prevalence of dyschromatopsia in the rivers, control group and total group was 2.2%, 2.8% and 2.6% respectively. CONCLUSION A considerably high number of drivers are in lack of optimal visual acuity. Refraction errors in drivers may impair the traffic security. PMID:22553671

Management of pseudophakic myopic anisometropic amblyopia with piggyback Visian® implantable collamer lens.

PubMed

Eissa, Sherif A

2017-03-01

To assess the outcomes of sulcus implantation of the Visian ® implantable collamer lens (ICL) to correct pseudophakic myopic anisometropic amblyopia with myopic shift and/or primary refractive overcorrection. Prospective case series enrolled 14 pseudophakic eyes of 14 patients, 5-9 years old, with history of cataract surgery and primary in the bag-intraocular lenses (IOL) implantation, followed by myopic shift and/or refractive overcorrection and anisometropic amblyopia of variable degrees. All cases had implantation of a piggyback ICL/toric ICL, to correct the myopia/myopic astigmatism. Preoperatively, we evaluated the uncorrected distance visual acuity (UCVA), corrected distance visual acuity (CDVA), manifest refraction spherical equivalent (MRSE), intraocular pressure (IOP) and endothelial cell density (ECD). We assessed the position and vaulting of the ICLs on slit lamp examination and confirmed by Scheimpflug tomography. Postoperative follow-up was at 1st week and 1, 3, 6, 9, 12, 18 and 24 months. Uncorrected distance visual acuity improved in all cases, and CDVA improved in 11 amblyopic eyes (2-4 lines). There was no evidence of interlenticular opacification (ILO) throughout the 2-year follow-up. Two cases were complicated with early postoperative acute elevation of IOP and were controlled with topical beta-blockers. Postoperative acute anterior uveitis occurred in six eyes and controlled by topical steroids. Implantable collamer lens (ICL) vault was measured using Pentacam, with mean value of 470 ± 238 μm. Sulcus implantation of the secondary piggyback ICL to correct unilateral pseudophakic myopic refractive error in children was safe, efficient, predictable and well tolerated in management of anisometropic amblyopia in all eyes. © 2016 Acta Ophthalmologica Scandinavica Foundation. Published by John Wiley & Sons Ltd.

Refractive error and visual impairment in school children in Northern Ireland.

PubMed

O'Donoghue, L; McClelland, J F; Logan, N S; Rudnicka, A R; Owen, C G; Saunders, K J

2010-09-01

To describe the prevalence of refractive error (myopia and hyperopia) and visual impairment in a representative sample of white school children. The Northern Ireland Childhood Errors of Refraction study, a population-based cross-sectional study, examined 661 white 12-13-year-old and 392 white 6-7-year-old children between 2006 and 2008. Procedures included assessment of monocular logarithm of the minimum angle of resolution (logMAR), visual acuity (unaided and presenting) and binocular open-field cycloplegic (1% cyclopentolate) autorefraction. Myopia was defined as -0.50DS or more myopic spherical equivalent refraction (SER) in either eye, hyperopia as > or =+2.00DS SER in either eye if not previously classified as myopic. Visual impairment was defined as >0.30 logMAR units (equivalent to 6/12). Levels of myopia were 2.8% (95% CI 1.3% to 4.3%) in younger and 17.7% (95% CI 13.2% to 22.2%) in older children: corresponding levels of hyperopia were 26% (95% CI 20% to 33%) and 14.7% (95% CI 9.9% to 19.4%). The prevalence of presenting visual impairment in the better eye was 3.6% in 12-13-year-old children compared with 1.5% in 6-7-year-old children. Almost one in four children fails to bring their spectacles to school. This study is the first to provide robust population-based data on the prevalence of refractive error and visual impairment in Northern Irish school children. Strategies to improve compliance with spectacle wear are required.

Myopic refractive shift represents dense nuclear sclerosis and thin lens in lenticular myopia.

PubMed

Cho, Yang Kyung; Huang, Wei; Nishimura, Eiichi

2013-09-01

It is not rare to meet unilateral nuclear sclerotic cataracts with myopic refractive changes (lenticular myopia) compared with the fellow eye in the ophthalmic examination of patients with decreased visual acuity. To determine the relationship between the myopic refractive changes and interocular differences of parameters, we investigated the interocular differences of ocular parameters between a lenticular myopic eye and the fellow eye. This retrospective study included 68 eyes of 34 patients, who showed unilateral lenticular myopia. We compared the dimensions of ocular component, such as anterior chamber depth, anterior chamber volume, lens thickness, vitreous chamber depth, lens position, lens density of nuclear sclerosis, anterior lens curvature and myopic refractive changes (spherical equivalent refraction) between the lenticular myopic eye and the myopic refractive change were examined. Statistically significant differences were found between the lenticular myopic eye and the fellow eye for anterior chamber depth (p = 0.015) anterior chamber volume (p = 0.031), lens thickness (p < 0.001), lens density of the nuclear sclerosis (p < 0.001) and the spherical equivalent myopic refractive changes (p < 0.001). Based on univariate analysis, the interocular difference in spherical equivalent refraction was significantly correlated with interocular differences of the density of the nuclear sclerosis (r = 0.79, p < 0.001), lens thickness (r = -0.70, p < 0.001) and vitreous chamber depth (r = 0.43, p = 0.012). Based on multiple regression analysis, the interocular difference in spherical equivalent refraction was significantly correlated with interocular differences of density of nuclear sclerosis (p < 0.001) and lens thickness (p = 0.007). The difference in myopic spherical change reflects the differences in the severity of nuclear sclerosis and lens thickness between the lenticular myopic eye and the fellow eye. © 2013 The Authors. Clinical and Experimental Optometry © 2013 Optometrists Association Australia.

Refractive Lenticule Transplantation for Correction of Iatrogenic Hyperopia and High Astigmatism After LASIK.

PubMed

Lazaridis, Apostolos; Reinstein, Dan Z; Archer, Timothy J; Schulze, Stephan; Sekundo, Walter

2016-11-01

To design a technique for intrastromal transplantation of stromal lenticules with specific refractive power for correction of post-LASIK induced hyperopia and astigmatism. A 28-year-old patient was referred for consultation after complicated LASIK for moderate myopia and astigmatism. The refractive error of the right eye was severely overcorrected due to data entry error. Post-LASIK refraction showed high astigmatism (right eye: +6.50 -9.00 @ 84°) and corrected distance visual acuity (CDVA) of 20/32. The corneal thickness was 282 µm. A refractive lenticule transplantation was performed due to contact lens intolerance, poor visual acuity, and severe anisometropia. A toric and myopic lenticule, obtained from a donor using the femtosecond lenticule extraction technique, was implanted under the flap to reduce the refractive error, bring the refraction of the eye to the level correctable by phakic intraocular lens, and restore corneal volume. Six weeks postoperatively, the donor lenticule was spread smoothly in the interface with a minor temporal decentration in relation to pupil center. The refraction showed a reduction of astigmatism but a stronger myopization compared to preoperative calculations (right eye: -6.50 -4.00 @ 70°). At 3 months, the CDVA returned to the preoperative value of 20/32. One year postoperatively, corneal tomography showed no signs of ectasia and biomicroscopy revealed no signs of rejection. After implanting a toric myopic implantable collamer lens, the patient regained uncorrected distance visual acuity of 20/40 and full stereopsis. The refractive lenticule transplantation technique offers a solution for rare cases of post-LASIK hyperopia and high astigmatism while restoring the volume of thin corneas. Moreover, it is a reversible procedure with low probability of rejection. [J Refract Surg. 2016;32(11):780-786.]. Copyright 2016, SLACK Incorporated.

Corneal and Crystalline Lens Dimensions Before and After Myopia Onset

PubMed Central

Mutti, Donald O.; Mitchell, G. Lynn; Sinnott, Loraine T.; Jones-Jordan, Lisa A.; Moeschberger, Melvin L.; Cotter, Susan A.; Kleinstein, Robert N.; Manny, Ruth E.; Twelker, J. Daniel; Zadnik, Karla

2011-01-01

Purpose To describe corneal and crystalline lens dimensions before, during, and after myopia onset compared to age-matched emmetropic values. Methods Subjects were 732 children 6 to 14 years of age who became myopic and 596 emmetropic children participating between 1989 and 2007 in the Collaborative Longitudinal Evaluation of Ethnicity and Refractive Error Study. Refractive error was measured using cycloplegic autorefraction, corneal power using a hand-held autokeratometer, crystalline lens parameters using video-based phakometry, and vitreous chamber depth (VCD) using A-scan ultrasonography. Corneal and crystalline lens parameters in children who became myopic were compared to age-, gender-, and ethnicity-matched model estimates of emmetrope values annually from 5 years before through 5 years after the onset of myopia. The comparison was made without, then with statistical adjustment of emmetrope component values to compensate for the effects of longer VCDs in children who became myopic. Results Before myopia onset, the crystalline lens thinned, flattened, and lost power at similar rates for emmetropes and children who became myopic. The crystalline lens stopped thinning, flattening, and losing power within ±1 year of onset in children who became myopic compared to emmetropes statistically adjusted to match the longer vitreous chamber depths of children who became myopic. In contrast, the cornea was only slightly steeper in children who became myopic compared to emmetropes (<0.25 D) and underwent little change across visits. Conclusions Myopia onset is characterized by an abrupt loss of compensatory changes in the crystalline lens that continue in emmetropes throughout childhood axial elongation. The mechanism responsible for this decoupling remains speculative, but might include restricted equatorial growth from internal mechanical factors. PMID:22227914

Repeatability of Spectral Domain Optical Coherence Tomography Measurements in High Myopia.

PubMed

Rao, Harsha L; Kumar, Addepalli U; Bonala, Sampath R; Yogesh, Kadam; Lakshmi, Bodduluri

2016-05-01

The purpose of this study was to compare the repeatability of spectral domain optical coherence tomography (SDOCT) parameters in high-myopic and emmetropic healthy subjects, and to evaluate the influence of axial length on the repeatability of SDOCT parameters in high myopia. In a prospective study, 93 eyes of 63 high-myopic subjects (spherical refractive error, -6 to -12 D; median age, 25 y) and 28 eyes of 14 emmetropic (spherical refractive error, 0 D; median age, 30 y) subjects underwent optic nerve head, retinal nerve fiber layer (RNFL), and ganglion cell complex imaging with SDOCT. For the repeatability analysis, 31 eyes of 31 high-myopic subjects and 14 eyes of 14 emmetropic subjects underwent 3 repeated scans in the same session. Among the optic nerve head parameters, within-subject coefficient of variation (CVw) measurements of the disc area (0.6% vs. 0.2%), rim area (8.7 vs. 2.8), and rim volume (16.7 vs. 8.9) were significantly larger (worse) in high-myopic compared with the emmetropic subjects. CVw measurements of all RNFL (range, 1.7 to 22.4) and ganglion cell complex (range, 1.8 to 2.5) parameters in high-myopic subjects were comparable to that in emmetropic subjects (2.4 to 24.0 and 1.7 to 2.0, respectively). Axial length significantly affected the CVw of nasal (coefficient, 0.01; P=0.04) and average RNFL (coefficient, 0.004; P=0.001) parameters but not that of the other SDOCT parameters. Repeatabilities of most of the SDOCT parameters in high-myopic subjects were good and comparable to that of emmetropic subjects. This suggests that SDOCT can be useful for following up high-myopic glaucoma patients to detect progression.

Peripheral refraction in pseudophakic eyes measured by infrared scanning photoretinoscopy.

PubMed

Tabernero, Juan; Ohlendorf, Arne; Fischer, M Dominik; Bruckmann, Anna R; Schiefer, Ulrich; Schaeffel, Frank

2012-05-01

To obtain quantitative data of peripheral refractive errors in pseudophakic eyes including measurements up to ±45 degrees on the retina. University Eye Hospital, Tübingen, Germany. Population-based cross-sectional study. Pseudophakic and phakic subjects were measured with a purpose-built scanning photorefractor. The instrument was improved over previous versions. It permits measurement of semicontinuous peripheral profiles over the central 90-degree field of the retina at a faster speed (4 s/scan). Twenty-four pseudophakic and 43 phakic subjects were enrolled. The intraocular lenses (IOLs) induced a mean myopic shift of 2.00 diopters (D) at ±45 degrees of eccentricity in the vertical pupil meridian. Ray-tracing simulations with phakic eye and pseudophakic eye models agreed well with the experimental data. They showed that changes induced by IOLs were a consequence of an increase in astigmatism with eccentricity and a myopic shift in the spherical equivalent. The peripheral refractions in pseudophakic eyes were more myopic than in phakic eyes as a consequence of the optical design of the IOLs. Whether a more myopic refraction of approximately 2.00 D at 45 degrees has significant effects on visual performance must be tested. Perhaps there is room for improvement in the peripheral optics of IOLs. No author has a financial or proprietary interest in any material or method mentioned. Copyright © 2012 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.

Effects of Foveal Ablation on Emmetropization and Form-Deprivation Myopia

PubMed Central

Smith, Earl L.; Ramamirtham, Ramkumar; Qiao-Grider, Ying; Hung, Li-Fang; Huang, Juan; Kee, Chea-su; Coats, David; Paysse, Evelyn

2009-01-01

Purpose Because of the prominence of central vision in primates, it has generally been assumed that signals from the fovea dominate refractive development. To test this assumption, the authors determined whether an intact fovea was essential for either normal emmetropization or the vision-induced myopic errors produced by form deprivation. Methods In 13 rhesus monkeys at 3 weeks of age, the fovea and most of the perifovea in one eye were ablated by laser photocoagulation. Five of these animals were subsequently allowed unrestricted vision. For the other eight monkeys with foveal ablations, a diffuser lens was secured in front of the treated eyes to produce form deprivation. Refractive development was assessed along the pupillary axis by retinoscopy, keratometry, and A-scan ultrasonography. Control data were obtained from 21 normal monkeys and three infants reared with plano lenses in front of both eyes. Results Foveal ablations had no apparent effect on emmetropization. Refractive errors for both eyes of the treated infants allowed unrestricted vision were within the control range throughout the observation period, and there were no systematic interocular differences in refractive error or axial length. In addition, foveal ablation did not prevent form deprivation myopia; six of the eight infants that experienced monocular form deprivation developed myopic axial anisometropias outside the control range. Conclusions Visual signals from the fovea are not essential for normal refractive development or the vision-induced alterations in ocular growth produced by form deprivation. Conversely, the peripheral retina, in isolation, can regulate emmetropizing responses and produce anomalous refractive errors in response to abnormal visual experience. These results indicate that peripheral vision should be considered when assessing the effects of visual experience on refractive development. PMID:17724167

Prevalence of refractive errors among schoolchildren in rural central Ethiopia.

PubMed

Mehari, Zelalem Addisu; Yimer, Abdirahman Wollie

2013-01-01

The aim of the present study was to assess the prevalence of refractive errors and visual impairment among schoolchildren in rural central Ethiopia. A cross-sectional study was conducted from November 2010 to January 2011 among 5,470 schoolchildren from 14 schools, of whom 4,238 (aged 7-18 years) were screened for refractive errors. In all participants, uncorrected vision and best corrected visual acuity were determined and those with a visual acuity of 6/12 or worse, underwent a complete ophthalmic examination to determine the cause of visual impairment. Myopia was defined as a spherical equivalent of -0.50 dioptre (D) or greater in one or both eyes and hyperopia as a spherical equivalent of +2.00 D or greater. A cylindrical power of -0.50 DC (D cylinder) or greater was considered as astigmatism. Chi-square was used to test differences in proportions. Differences were considered to be statistically significant at the five per cent level. Of the 4,238 children, 405 (9.5 per cent) were visually impaired and of these 267 children were diagnosed as having refractive errors, with an overall prevalence of 6.3 per cent, comprised of 6.1 per cent in boys and 6.6 per cent in girls. Myopia is the most prevalent refractive error; accounting for 6.0 per cent, followed by compound myopic astigmatism 1.2 per cent, then simple myopic astigmatism 0.5 per cent, mixed astigmatism 0.26 per cent and finally hyperopia 0.33 per cent. Reasons for visual acuity of 6/12 or worse in the better eye were found to be refractive error (65.9 per cent), corneal problems (12.8 per cent) and amblyopia (9.6 per cent). The prevalence of manifest strabismus in the study group was 1.1 per cent (n = 45). The study concluded that uncorrected refractive error is a common cause of visual impairment among schoolchildren in rural central Ethiopia. This indicates the need for regular school-screening programs that provide glasses at low cost or free of charge for those who have refractive errors. © 2012 The Authors; Clinical and Experimental Optometry © 2012 Optometrists Association Australia.

[Nature or nurture: effects of parental ametropia on children's refractive errors].

PubMed

Landmann, A; Bechrakis, E

2013-12-01

The aim of this study was to quantify the degree of association between juvenile refraction errors and parental refraction status. Using a simple questionnaire we conducted a cross-sectional study to determine the prevalence and magnitudes of refractive errors and of parental refraction status in a sample (n=728) of 10- to 18-year-old Austrian grammar school students. Students with myopia or hyperopia were more likely to have ametropic parents and refraction was more myopic in juveniles with one or two parents being ametropic. The prevalence of myopia in children with 2 ametropic parents was 54%, decreasing to 35% in pupils with 1 and to 13% in children with no ametropic parents. The odds ratio for 1 and 2 compared with no ametropic parents was 8.3 and 3.7 for myopia and 1.3 and 1.6 for hyperopia, respectively. Furthermore, the data indicate a stronger influence of the maternal ametropia on children's refractive errors than paternal ametropia. Genetic factors play a significant role in refractive error and may be of dominant influence for school myopia under conditions of low environmental variation.

Comparison of astigmatic correction after femtosecond lenticule extraction and wavefront-guided LASIK for myopic astigmatism.

PubMed

Ali, Mohamed A; Kobashi, Hidenaga; Kamiya, Kazutaka; Igarashi, Akihito; Miyake, Toshiyuki; Elewa, Mohamed Ehab M; Komatsu, Mari; Shimizu, Kimiya

2014-12-01

To compare postoperative astigmatic correction between femtosecond lenticule extraction (FLEx) and wavefront-guided LASIK in eyes with myopic astigmatism. Fifty-eight eyes of 41 patients undergoing FLEx and 49 eyes of 29 patients undergoing wavefront-guided LASIK to correct myopic astigmatism were examined. Visual acuity, cylindrical refraction, predictability of the astigmatic correction, and astigmatic vector components were compared between groups 6 months after surgery. There was no statistically significant difference in manifest cylindrical refraction (P = .08) or percentage of eyes within ± 0.50 diopter (D) of its refraction (P = .11) between the surgical procedures. The index of success in FLEx was statistically significantly better than that of wavefront-guided LASIK (P = .02), although there was no significant difference between the groups in other indices (eg, surgically induced astigmatism, target-induced astigmatism, astigmatic correction index, angle of error, difference vector, and flattening index). Subgroup analysis showed that FLEx had a better index of success (P = .02) and difference vector (P = .04) than wavefront-guided LASIK in the low cylinder subgroup; the angle of error in FLEx was significantly smaller than that of wavefront-guided LASIK in the moderate cylinder subgroup (P = .03). Both FLEx and wavefront-guided LASIK worked well for the correction of myopic astigmatism by the 6-month follow-up visit. Although FLEx had a better index of success than wavefront-guided LASIK when using vector analysis, it appears equivalent to wavefront-guided LASIK in terms of visual acuity and the correction of astigmatism. Copyright 2014, SLACK Incorporated.

Comparison of Astigmatic Correction after Femtosecond Lenticule Extraction and Small-Incision Lenticule Extraction for Myopic Astigmatism

PubMed Central

Kobashi, Hidenaga; Kamiya, Kazutaka; Ali, Mohamed A.; Igarashi, Akihito; Elewa, Mohamed Ehab M.; Shimizu, Kimiya

2015-01-01

Purpose To compare postoperative astigmatic correction between femtosecond lenticule extraction (FLEx) and small-incision lenticule extraction (SMILE) in eyes with myopic astigmatism. Methods We examined 26 eyes of 26 patients undergoing FLEx and 26 eyes of 26 patients undergoing SMILE to correct myopic astigmatism (manifest astigmatism of 1 diopter (D) or more). Visual acuity, cylindrical refraction, the predictability of the astigmatic correction, and the astigmatic vector components using Alpin’s method, were compared between the two groups 3 months postoperatively. Results We found no statistically significant difference in manifest cylindrical refraction (p=0.74) or in the percentage of eyes within ± 0.50 D of their refraction (p=0.47) after the two surgical procedures. Moreover, no statistically significant difference was detected between the groups in astigmatic vector components, namely, surgically induced astigmatism (0.80), target induced astigmatism (p=0.87), astigmatic correction index (p=0.77), angle of error (p=0.24), difference vector (p=0.76), index of success (p=0.91), flattening effect (p=0.79), and flattening index (p=0.84). Conclusions Both FLEx and SMILE procedures are essentially equivalent in correcting myopic astigmatism using vector analysis, suggesting that the lifting or non-lifting of the flap does not significantly affect astigmatic outcomes after these surgical procedures. PMID:25849381

Refractive regression after laser in situ keratomileusis.

PubMed

Yan, Mabel K; Chang, John Sm; Chan, Tommy Cy

2018-04-26

Uncorrected refractive errors are a leading cause of visual impairment across the world. In today's society, laser in situ keratomileusis (LASIK) has become the most commonly performed surgical procedure to correct refractive errors. However, regression of the initially achieved refractive correction has been a widely observed phenomenon following LASIK since its inception more than two decades ago. Despite technological advances in laser refractive surgery and various proposed management strategies, post-LASIK regression is still frequently observed and has significant implications for the long-term visual performance and quality of life of patients. This review explores the mechanism of refractive regression after both myopic and hyperopic LASIK, predisposing risk factors and its clinical course. In addition, current preventative strategies and therapies are also reviewed. © 2018 Royal Australian and New Zealand College of Ophthalmologists.

Relative peripheral refraction across 4 meridians after orthokeratology and LASIK surgery.

PubMed

Queirós, António; Amorim-de-Sousa, Ana; Lopes-Ferreira, Daniela; Villa-Collar, César; Gutiérrez, Ángel Ramón; González-Méijome, José Manuel

2018-01-01

To characterize the axial and off-axis refraction across four meridians of the retina in myopic eyes before and after Orthokeratology (OK) and LASIK surgery. Sixty right eyes with a spherical equivalent (M) between - 0.75 to - 5.25 D (cylinder <- 1.00 D) underwent LASIK (n = 26) or OK (n = 34) to treat myopia. Axial and off-axis refraction were measured with an open-field autorefractometer before and after stabilized treatments. Off-axis measurements were obtained for the horizontal (35° nasal and temporal retina) and vertical (15° superior and inferior retina) meridians, and for two oblique directions (45-225° and 135-315°) up to 20° of eccentricity. The refractive profile was addressed as relative peripheral refractive error (RPRE). OK and LASIK post-treatment results showed an increase of myopic relative refraction at several eccentric locations. At the four meridians evaluated, the M component of the pre-treatment RPRE values was not statistically different ( p > 0.05) from the post-treatment RPRE within 30° and 20° of the central visual field after LASIK and OK, respectively. These results demonstrated that the treatment zone warrants an optimal central field of vision. The present study gives an overview of RPRE after refractive corneal reshaping treatments (OK and LASIK) across vertical, horizontal and two oblique meridians together. This allows a 3D representation of RPRE at the retina and shows that the myopic shift induced by both treatments is more relevant in horizontal directions.

Clinical vision characteristics of the congenital achromatopsias. I. Visual acuity, refractive error, and binocular status.

PubMed

Haegerstrom-Portnoy, G; Schneck, M E; Verdon, W A; Hewlett, S E

1996-07-01

Visual acuity, refractive error, and binocular status were determined in 43 autosomal recessive (AR) and 15 X-linked (XL) congenital achromats. The achromats were classified by color matching and spectral sensitivity data. Large interindividual variation in refractive error and visual acuity was present within each achromat group (complete AR, incomplete AR, and XL). However, the number of individuals with significant interocular acuity differences is very small. Most XLs are myopic; ARs show a wide range of refractive error from high myopia to high hyperopia. Acuity of the AR and XL groups was very similar. With-the-rule astigmatism of large amount is very common in achromats, particularly ARs. There is a close association between strabismus and interocular acuity differences in the ARs, with the fixating eye having better than average acuity. The large overlap of acuity and refractive error of XL and AR achromats suggests that these measures are less useful for differential diagnosis than generally indicated by the clinical literature.

Agreement Between Autorefraction and Subjective Refraction in Keraring-Implanted Keratoconic Eyes.

PubMed

Al-Tuwairqi, Waleed S; Ogbuehi, Kelechi C; Razzouk, Haya; Alanazi, Mana A; Osuagwu, Uchechukwu L

2017-03-01

To assess the agreement between subjective refraction and autorefraction and to explore the relationship between the magnitude of higher order aberration, and visual acuity and refraction, before and after keraring implantation. This prospective, randomized, interventional study enrolled 27 subjects (mean age 28.1±6.5 years) with keratoconus. Noncycloplegic refraction was performed subjectively by one clinician and with an autorefractor by another clinician, before and 6 months after surgery. The limit of agreement (LoA) between methods was assessed, and the relationships between the corrected distance visual acuity, logMAR on the one hand and refraction measurements and higher-order aberrations on the other, were examined. The agreement in mean spherical equivalent refraction (MSER) between methods was good postoperatively but poor preoperatively. The autorefractor gave a more myopic refraction than subjective refraction preoperatively (-3.28±3.06 D; LoA -9.27 to +2.71 D, P<0.0001) and postoperatively (-0.63±1.64 D; LoA -3.85 to +2.58 D, P=0.055), and returned higher negative cylinders preoperatively (-1.10±1.17 D; LoA -3.40 to +1.19 D, P<0.0001) and postoperatively (-1.08±1.27 D; LoA -3.60 to +1.41 D, P<0.0001) in keratoconic eyes. The difference in MSER between methods was significantly related to the refractive error at both visits (P<0.05) and to the magnitude of higher-order aberrations in keratoconic eyes preoperatively (P<0.05). The logMAR visual acuity achieved subjectively worsened as the magnitude of higher-order aberrations increased preoperatively (P<0.001). The autorefractor returns values that are significantly more myopic in MSER and higher negative cylinders than subjective refraction, preoperatively, but the MSER was similar between devices postoperatively. The autorefactor seems a valid starting point for subjective refraction in keratoconic eyes treated with keraring, but the cylinder should be corrected by about +1 D. The instruments agree more in less myopic than high myopic eyes.

Manual limbal markings versus iris-registration software for correction of myopic astigmatism by laser in situ keratomileusis.

PubMed

Shen, Elizabeth P; Chen, Wei-Li; Hu, Fung-Rong

2010-03-01

To compare the efficacy and safety of manual limbal markings and wavefront-guided treatment with iris-registration software in laser in situ keratomileusis (LASIK) for myopic astigmatism. National Taiwan University Hospital, Taipei, Taiwan. Eyes with myopic astigmatism had LASIK with a Technolas 217z laser. Eyes in the limbal-marking group had conventional LASIK (PlanoScan or Zyoptix tissue-saving algorithm) with manual cyclotorsional-error adjustments according to 2 limbal marks. Eyes in the iris-registration group had wavefront-guided ablation (Zyoptix) in which cyclotorsional errors were automatically detected and adjusted. Refraction, corneal topography, and visual acuity data were compared between groups. Vector analysis was by the Alpins method. The mean preoperative spherical equivalent (SE) was -6.64 diopters (D) +/- 1.99 (SD) in the limbal-marking group and -6.72 +/- 1.86 D in the iris-registration group (P = .92). At 6 months, the mean SE was -0.42 +/- 0.63 D and -0.47 +/- 0.62 D, respectively (P = .08). There was no statistically significant difference between groups in the astigmatism correction, success, or flattening index values using 6-month postoperative refractive data. The angle of error was within +/-10 degrees in 73% of eyes in the limbal-marking group and 75% of eyes in the iris-registration group. Manual limbal markings and iris-registration software were equally effective and safe in LASIK for myopic astigmatism, showing that checking cyclotorsion by manual limbal markings is a safe alternative when automated systems are not available. Copyright 2010 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.

Width of anterior chamber angle determined by OCT, and correlation to refraction and age in a German working population: the MIPH Eye&Health Study.

PubMed

Vossmerbaeumer, Urs; Schuster, Alexander K; Fischer, Joachim E

2013-12-01

Optical coherence tomography (OCT) of the anterior segment allows quantitative analysis of the geometry of the chamber angle. We performed bilateral spectral-domain OCT measurements in healthy, emmetropic, hyperopic, and myopic subjects to establish correlations between the width of the angle, the refraction, and intraocular pressure of the test persons. Out of 4,617 eyes (2,309 subjects), those with refractive errors of < -4 or > +3 diopters were identified by objective refraction measurement (KR-8800 Kerato-Refractometer, Topcon Inc., Japan) and examined using the anterior segment mode of a spectral-domain 3D OCT-2000 (Topcon Inc., Japan). Non-contact tonometry was performed (CT-80, Topcon Inc., Japan). One hundred and eight eyes of 54 emmetropic subjects (± 0.5 dpt) served as reference group. Previous ocular surgery was exclusion criterion in all groups. Width of the chamber angle was determined using semi-automated software tools and statistical analysis of the data (Pearson correlation, ANOVA with post-hoc test and Bonferroni correction, regression analysis) was performed using SPSS software (SPSS 19.0, Chicago, IL, USA). Six hundred and sixty-eight eyes of 398 persons (292 male, 96 female) were included in the study. Mean hyperopic refraction was +4.24 (+3  to +7.75) dpt, mean myopic refraction was -5.86 (-4 to -11.75) dpt. Valid chamber angle OCT measurements could be obtained from 50 (69.4 %) hyperopic and 400 (71.4 %) myopic eyes meeting the inclusion criteria. The mean width of the chamber angle was determined as 31.8° (range: 13.5 to 45.6, SD 7.49) in the hyperopic group, 40.8° (range: 19.3 to 66.0, SD 8.1) in the myopic group, and 36.3° (range: 21.1 to 51.8, SD 6.8) in the emmetropic reference group. Correlation was highly significant (p > 0.001) between refractive error and the aperture of the chamber angle as measured from OCT. The association of the intraocular pressure and the refraction was also highly significant (p > 0.001) for the three groups. The spectral-domain OCT yielded measurements that could be used for digital analysis of the chamber angle geometry. Our results highlight the correlation between refraction and aperture of the angle in hyperopia and myopia as determined by the 3D OCT-2000: hyperopia is associated with a narrower chamber angle, myopia with a wider aperture of the angle.

Clinical outcomes of Transepithelial photorefractive keratectomy to treat low to moderate myopic astigmatism.

PubMed

Xi, Lei; Zhang, Chen; He, Yanling

2018-05-09

To evaluate the refractive and visual outcomes of Transepithelial photorefractive keratectomy (TransPRK) in the treatment of low to moderate myopic astigmatism. This retrospective study enrolled a total of 47 eyes that had undergone Transepithelial photorefractive keratectomy. Preoperative cylinder diopters ranged from - 0.75D to - 2.25D (mean - 1.11 ± 0.40D), and the sphere was between - 1.50D to - 5.75D. Visual outcomes and vector analysis of astigmatism that included error ratio (ER), correction ratio (CR), error of magnitude (EM) and error of angle (EA) were evaluated. At 6 months after TransPRK, all eyes had an uncorrected distance visual acuity of 20/20 or better, no eyes lost ≥2 lines of corrected distant visual acuity (CDVA), and 93.6% had residual refractive cylinder within ±0.50D of intended correction. On vector analysis, the mean correction ratio for refractive cylinder was 1.03 ± 0.30. The mean error magnitude was - 0.04 ± 0.36. The mean error of angle was 0.44° ± 7.42°and 80.9% of eyes had axis shift within ±10°. The absolute astigmatic error of magnitude was statistically significantly correlated with the intended cylinder correction (r = 0.48, P < 0.01). TransPRK showed safe, effective and predictable results in the correction of low to moderate astigmatism and myopia.

Retinal oxygen saturation in Chinese adolescents.

PubMed

Liu, Xue; Wang, Shuang; Liu, Yi; Liu, Li Juan; Lv, Yan Yun; Tang, Ping; Jonas, Jost B; Xu, Liang

2017-02-01

To study the retinal oxygen saturation in normal eyes of Chinese adolescents. Performing retinal oximetry with the Oxymap T1 Retinal Oximeter in healthy children and adolescents (aged 5-18 years old), we measured the arterial (SaO 2 ) and venular (SvO 2 ) oxygen saturation and the arteriovenous difference in oxygen saturation (Sa-vO 2 ). The study included 122 individuals with a mean age of 13.0 ± 2.9 years (range: 5-18 years) and a mean refractive error of -3.25 ± 2.49 dioptres (range:-8.88 to +3.13 dioptres). Mean SaO 2 , SvO 2 and Sa-vO 2 was 85.5 ± 7.1%, 48.2 ± 5.5% and 37.3 ± 6.5%, respectively. Mean SaO 2 was significantly (p < 0.001) the lowest in the inferotemporal quadrant (79.1 ± 9.0%), followed by the superotemporal quadrant (83.4 ± 9.7%), the inferonasal quadrant (90.4 ± 10.6%) and the superonasal quadrant (93.4 ± 10.8%). In a similar manner, the values of the SvO 2 were the lowest (p < 0.001) in the inferotemporal quadrant (42.1 ± 8.3%), followed by the superotemporal quadrant (47.8 ± 7.2%), the inferonasal quadrant (52.3 ± 8.4%) and the superonasal quadrant (55.1 ± 7.6%). Arteriovenous difference in oxygen saturation (Sa-vO 2 ) did not differ significantly (all p > 0.05) between the fundus quadrants. In multiple linear regression analysis, SaO 2 increased (regression coefficient r 2  = 0.28) with older age (standardized regression coefficient β: 0.23; p = 0.01) and more myopic refractive error (β: -0.39; p < 0.001). Higher SvO 2 was significantly correlated with more myopic refractive error (β: -0.46; p < 0.001; r 2  = 0.20), while Sa-vO 2 increased significantly only with older age in the multivariate analysis (β: 0.26; p = 0.01; r 2  = 0.07). Our study provides normative data for Chinese children and adolescents who showed lower values than adults for SaO 2 and SvO 2 . SaO 2 increased with older age and higher myopic refractive error, SvO 2 increased with higher myopic refractive error, and Sa-vO 2 increased with older age. © 2016 Acta Ophthalmologica Scandinavica Foundation. Published by John Wiley & Sons Ltd.

Laser in situ keratomileusis for astigmatism ≤ 0.75 Diopter combined with low myopia: a retrospective data analysis

PubMed Central

2014-01-01

Background This study examined the refractive and visual outcome of wavefront-optimized laser in situ keratomileusis (LASIK) in eyes with low myopia and compound myopic astigmatism ≤ 0.75 diopter (D). Methods 153 eyes from 153 consecutive myopic patients (74 male, 79 female; mean age at surgery 40.4 ± 10.4 years) who had a preoperative refractive cylinder ≤ 0.75 D and a manifest sphere between -0.25 D and -2.75 D, and who had completed 4-month follow-up. Three subgroups defined by the magnitude of preoperative manifest refractive cylinder (0.25, 0.50, and 0.75 D) were formed. Manifest refraction, uncorrected and corrected visual acuity were assessed pre- and postoperatively. The astigmatic changes achieved were determined using the Alpins vector analysis. Results After 4 months (120.0 ± 27.6 days) of follow-up, a mean uncorrected distant visual acuity of 0.07 ± 0.11 logMAR and a mean manifest refraction spherical equivalent of -0.06 ± 0.56 D were found. There was no statistically significant difference in efficacy and safety between the preoperative cylinder groups. Astigmatic overcorrection for preoperative cylinder of ≤ 0.50 D was suggested by the correction index, the magnitude of error, the index of success, and the flattening index. Conclusions Low myopic eyes with a preoperative cylinder of ≤ 0.50 D were significantly overcorrected with regard to cylinder correction when combined with low myopic LASIK. Accordingly, we are cautious in recommending full astigmatic correction for eyes with low myopia and manifest cylinder of ≤ 0.50 D. PMID:24393469

High susceptibility to experimental myopia in a mouse model with a retinal on pathway defect.

PubMed

Pardue, Machelle T; Faulkner, Amanda E; Fernandes, Alcides; Yin, Hang; Schaeffel, Frank; Williams, Robert W; Pozdeyev, Nikita; Iuvone, P Michael

2008-02-01

Nob mice share the same mutation in the Nyx gene that is found in humans with complete congenital stationary night blindness (CSNB1). Nob mutant mice were studied to determine whether this defect resulted in myopia, as it does in humans. Refractive development was measured in unmanipulated wild-type C57BL/6J (WT) and nob mice from 4 to 12 weeks of age by using an infrared photorefractor. The right eye was form deprived by means of a skull-mounted goggling apparatus at 4 weeks of age. Refractive errors were recorded every 2 weeks after goggling. The content of dopamine and the dopamine metabolite 3,4-dihydroxyphenylacetic acid (DOPAC) were measured by HPLC with electrochemical detection (HPLC-ECD) in retinas of nob and WT mice under light- and dark-adapted conditions. The nob mice had greater hyperopic refractive errors than did the WT mice under normal visual conditions, until 12 weeks of age when both strains had similar refractions. At 6 weeks of age, refractions became less hyperopic in the nob mice but continued to become more hyperopic in the WT mice. After 2 weeks of form deprivation (6 weeks of age), the nob mice displayed a significant myopic shift (~4 D) in refractive error relative to the opposite and control eyes, whereas WT mice required 6 weeks of goggling to elicit a similar response. As expected with loss of ON pathway transmission, light exposure did not alter DOPAC levels in the nob mice. However, dopamine and DOPAC levels were significantly lower in the nob mice compared with WT. Under normal laboratory visual conditions, only minor differences in refractive development were observed between the nob and WT mice. The largest myopic shift in the nob mice resulted after form deprivation, suggesting that visual pathways dependent on nyctalopin and/or abnormally low dopaminergic activity play a role in regulating refractive development. These findings demonstrate an interaction of genetics and environment in refractive development.

High susceptibility to experimental myopia in a mouse model with a retinal ON pathway defect

PubMed Central

Pardue, Machelle T.; Faulkner, Amanda E.; Fernandes, Alcides; Yin, Hang; Schaeffel, Frank; Williams, Robert W.; Pozdeyev, Nikita; Iuvone, P. Michael

2009-01-01

Purpose Nob mice share the same mutation in the Nyx gene that is found in humans with complete congenital stationary night blindness (CSNB1). We studied nob mutant mice to determine whether this defect resulted in myopia as it does in humans. Methods Refractive development was measured in unmanipulated wildtype C57BL/6J (WT) and nob mice from 4 to 12 weeks of age using an infrared photorefractor. The right eye was form-deprived by means of a skull-mounted goggling apparatus at 4 weeks of age. Refractive errors were recorded every 2 weeks after goggling. The content of dopamine and the dopamine metabolite, DOPAC, were measured using HPLC-ECD in retinas of nob and WT mice under light- and dark-adapted conditions. Results Nob mice had greater hyperopic refractive errors than WT mice under normal visual conditions until 12 weeks of age, when both strains had similar refractions. At 6 weeks of age, refractions became less hyperopic in nob mice but continued to become more hyperopic in WT mice. Following two weeks of form deprivation (6 weeks of age), nob mice displayed a significant myopic shift (~4 D) in refractive error relative to the opposite and control eyes, while WT mice required 6 weeks of goggling to elicit a similar response. As expected with loss of ON pathway transmission, light exposure did not alter DOPAC levels in nob mice. However, dopamine and DOPAC levels were significantly lower in nob mice compared to WT. Conclusions Under normal laboratory visual conditions, only minor differences in refractive development were observed between nob and WT mice. The largest myopic shift in nob mice resulted after form deprivation, suggesting that visual pathways dependent on nyctalopin and/or abnormally low dopaminergic activity play a role in regulating refractive development. These findings demonstrate an interaction of genetics and environment in refractive development. PMID:18235018

Relations between age, weight, refractive error and eye shape by computerized tomography in children.

PubMed

Song, Ha Tae; Kim, Young Jun; Lee, Soo Jung; Moon, Yeon Sung

2007-09-01

To investigate relationships between age, weight, refractive error, and morphologic changes in children's eyes by computerized tomography (CT). Of the 772 eyes of 386 patients under the age of 20 years, who visited our Department of Ophthalmology between January 2005 to August 2006 and underwent CT of the orbit, 406 eyes of 354 patients with clear CT images and normal eyeball contour were enrolled in the present retrospective study. The axial lengths, widths, horizontal and vertical lengths, refractive errors, and body weight of eyes were measured, and relationship between these parameters were investigated. Axial length was found to correlate significantly with eye width (r=0.914), and in emmetropic eyes and myopic eyes, axial lengths and widths were found to increase as age and body weight increased. Axial lengths increased rapidly until age 10, and then increased slowly. In emmetropic eyes, widths/axial lengths increased with age, but in myopic eyes these decreased as age or severity of myopia increased. Moreover, as age increased, the myopic population and severity also increased. The axial length was longer in case of myopia compared to emmetropia in all age groups and there was almost no difference in the increase rate of axial length by the age of myopia and emmetropia. However, the width was wider in case of myopia compared to emmetropia in all age groups and the increase rate of width in myopia by age was smaller than that of emmetropia. Myopia showed decreasing rate of width/axial length with increase of age, from 1.004 in 5 years to 0.971 in 20 years. However, emmetropia showed increasing rate of width/axial length with increase of age, from 0.990 in 5 years to 1.006 in 20 years.

Relations between Age, Weight, Refractive Error and Eye Shape by Computerized Tomography in Children

PubMed Central

Song, Ha Tae; Kim, Young Jun; Lee, Soo Jung

2007-01-01

Purpose To investigate relationships between age, weight, refractive error, and morphologic changes in children's eyes by computerized tomography (CT). Methods Of the 772 eyes of 386 patients under the age of 20 years, who visited our Department of Ophthalmology between January 2005 to August 2006 and underwent CT of the orbit, 406 eyes of 354 patients with clear CT images and normal eyeball contour were enrolled in the present retrospective study. The axial lengths, widths, horizontal and vertical lengths, refractive errors, and body weight of eyes were measured, and relationship between these parameters were investigated. Results Axial length was found to correlate significantly with eye width (r=0.914), and in emmetropic eyes and myopic eyes, axial lengths and widths were found to increase as age and body weight increased. Axial lengths increased rapidly until age 10, and then increased slowly. In emmetropic eyes, widths / axial lengths increased with age, but in myopic eyes these decreased as age or severity of myopia increased. Moreover, as age increased, the myopic population and severity also increased. Conclusions The axial length was longer in case of myopia compared to emmetropia in all age groups and there was almost no difference in the increase rate of axial length by the age of myopia and emmetropia. However, the width was wider in case of myopia compared to emmetropia in all age groups and the increase rate of width in myopia by age was smaller than that of emmetropia. Myopia showed decreasing rate of width/axial length with increase of age, from 1.004 in 5 years to 0.971 in 20 years. However, emmetropia showed increasing rate of width/axial length with increase of age, from 0.990 in 5 years to 1.006 in 20 years. PMID:17804923

Changes in Astigmatism, Densitometry, and Aberrations After SMILE for Low to High Myopic Astigmatism: A 12-Month Prospective Study.

PubMed

Pedersen, Iben Bach; Ivarsen, Anders; Hjortdal, Jesper

2017-01-01

To evaluate 12-month changes in refraction, visual outcome, corneal densitometry, and postoperative aberrations after small incision lenticule extraction (SMILE) for myopic astigmatism. This 12-month prospective clinical trial comprised 101 eyes (101 patients) treated with SMILE for myopic astigmatism with cylinder of 0.75 to 4.00 diopters (D). The preoperative, 1-week, and 1-, 3-, 6-, 9-, and 12-month examinations included measurement of manifest refraction, uncorrected distance visual acuity (UDVA), and corrected (CDVA) distance visual acuity. Astigmatic error vector analysis was performed using Al-pin's method. Densitometry and aberrations were evaluated with Pentacam HR (Oculus Optikgeräte, Wetzlar, Germany). Preoperative spherical equivalent averaged -6.78 ± 1.90 D with 1.81 ± 1.00 D in cylinder correction. After 12 months, 74% and 93% of the eyes were within ±0.50 and ±1.00 D of the attempted refraction, respectively. The logMAR UDVA and CDVA averaged 0.03 ± 0.16 and -0.08 ± 0.09, respectively. Vector analysis showed a with-the-rule undercorrection at 12 months with a mean difference vector of 0.31 D @ 91°. There was a minor counterclockwise rotation of the axis, with an arithmetic angle of error of 0.34° ± 14°. An undercorrection of approximately 11% per diopter of attempted correction was seen at 12 months. Spherical aberrations, coma, and higher order aberrations remained stable during the postoperative period (P < .09). After 12 months, no increase in densitometry could be identified. Treatment of astigmatism with SMILE seems to be predictable and effective, but with an astigmatic undercorrection of approximately 11% and a small counterclockwise rotation of the axis. [J Refract Surg. 2017;33(1):11-17.]. Copyright 2017, SLACK Incorporated.

Relative peripheral refraction in children: twelve-month changes in eyes with different ametropias.

PubMed

Lee, Tsui-Tsui; Cho, Pauline

2013-05-01

To determine the peripheral refraction of children with different types of ametropias and to evaluate the relationship between central refractive changes, baseline relative peripheral refraction (RPR) and changes in RPR over a 12-month monitoring period. Cycloplegic central and peripheral refraction were performed biannually on the right eyes of children aged 6-9 for 12 months, using an open-view autorefractor. Peripheral refraction were measured along 10°, 20° and 30° from central fixation in both nasal and temporal fields. Refractive data were transposed into M, J0 and J45 vectors for analyses. RPR was determined by subtracting the central measurement from each peripheral measurement. Hyperopic eyes showed relative peripheral myopia while myopic eyes had relative hyperopia across the central 60° horizontal field at baseline. Emmetropic eyes had relative myopia within but showed relative hyperopia beyond the central 30° field. However, there was no significant correlation between central refractive changes and baseline RPR or between changes in central refraction and RPR over twelve months in any refractive groups. Correlations between changes in PR and central myopic shift were found mainly in the nasal field in different groups. In the subgroup analysis on the initially emmetropic and the initially myopic groups, the subgroups with faster myopic progression did not have significantly different RPR from the subgroups with slower progression. The RPR pattern of the initially emmetropic and the initially myopic groups became more asymmetric at the end of the study period with a larger increase in relative hyperopia in the temporal field. RPR patterns were different among hyperopic, emmetropic and myopic eyes. However, baseline RPR and changes in RPR cannot predict changes in central refraction over time. Our results did not provide evidence to support the hypothesis of RPR as a causative factor for myopic central refractive changes in children. Ophthalmic & Physiological Optics © 2013 The College of Optometrists.

Association between Refractive Errors and Ocular Biometry in Iranian Adults

PubMed Central

Hashemi, Hassan; Khabazkhoob, Mehdi; Emamian, Mohammad Hassan; Shariati, Mohammad; Miraftab, Mohammad; Yekta, Abbasali; Ostadimoghaddam, Hadi; Fotouhi, Akbar

2015-01-01

Purpose: To investigate the association between ocular biometrics such as axial length (AL), anterior chamber depth (ACD), lens thickness (LT), vitreous chamber depth (VCD) and corneal power (CP) with different refractive errors. Methods: In a cross-sectional study on the 40 to 64-year-old population of Shahroud, random cluster sampling was performed. Ocular biometrics were measured using the Allegro Biograph (WaveLight AG, Erlangen, Germany) for all participants. Refractive errors were determined using cycloplegic refraction. Results: In the first model, the strongest correlations were found between spherical equivalent with axial length and corneal power. Spherical equivalent was strongly correlated with axial length in high myopic and high hyperopic cases, and with corneal power in high hyperopic cases; 69.5% of variability in spherical equivalent was attributed to changes in these variables. In the second model, the correlations between vitreous chamber depth and corneal power with spherical equivalent were stronger in myopes than hyperopes, while the correlations between lens thickness and anterior chamber depth with spherical equivalent were stronger in hyperopic cases than myopic ones. In the third model, anterior chamber depth + lens thickness correlated with spherical equivalent only in moderate and severe cases of hyperopia, and this index was not correlated with spherical equivalent in moderate to severe myopia. Conclusion: In individuals aged 40-64 years, corneal power and axial length make the greatest contribution to spherical equivalent in high hyperopia and high myopia. Anterior segment biometric components have a more important role in hyperopia than myopia. PMID:26730304

Evaluation of the toric implantable collamer lens for simultaneous treatment of myopia and astigmatism.

PubMed

Price, Marianne O; Price, Francis W

2015-01-01

Myopic astigmatism is a prevalent condition that can be treated with spectacles, contact lenses, or laser refractive surgery. However, these treatment options have functional limitations at higher levels of refractive error. The toric implantable collamer lens is designed to treat a broad range of refractive error, generally up to -18 diopters with +1 to +6 diopters of astigmatism. Approval for a more limited treatment range of up to 15 diopters of myopia with +1 to +4 diopters of astigmatism is being sought in the US, where this device has not yet received marketing approval. Surgical correction of high-myopic astigmatism can be life-altering and allow people to participate in activities that were not previously feasible because of visual limitations. The toric implantable collamer lens is implanted behind the iris and in front of the natural crystalline lens. With earlier lens designs, it was necessary to create an iridectomy or iridotomy to prevent pupillary block. The newest toric implantable collamer lens model has a small central hole that is not visually noticeable. This eliminates the need to create a hole in the iris, thereby enhancing the safety of the procedure.

Influence of the difference between corneal and refractive astigmatism on LASIK outcomes using solid-state technology.

PubMed

Piñero, David P; Ribera, David; Pérez-Cambrodí, Rafael J; Ruiz-Fortes, Pedro; Blanes-Mompó, Francisco J; Alzamora-Rodríguez, Antonio; Artola, Alberto

2014-12-01

To evaluate the influence of the difference between preoperative corneal and refractive astigmatism [ocular residual astigmatism (ORA)] on outcomes obtained after laser in situ keratomileusis (LASIK) surgery for correction of myopic astigmatism using the solid-state laser technology. One hundred one consecutive eyes with myopia or myopic astigmatism of 55 patients undergoing LASIK surgery using the Pulzar Z1 solid-state laser (CustomVis Laser Pty Ltd, currently CV Laser) were included. Visual and refractive changes at 6 months postoperatively and changes in ORA and anterior corneal astigmatism and posterior corneal astigmatism (PCA) were analyzed. Postoperatively, uncorrected distance visual acuity improved significantly (P < 0.01). Likewise, refractive cylinder magnitude and spherical equivalent were reduced significantly (P < 0.01). In contrast, no significant changes were observed in ORA magnitude (P = 0.81) and anterior corneal astigmatism (P = 0.12). The mean overall efficacy and safety indices were 0.96 and 1.01, respectively. These indices were not correlated with preoperative ORA (r = -0.15, P = 0.15). Furthermore, a significant correlation was found between ORA (r = 0.81, P < 0.01) and PCA postoperatively, but not preoperatively (r = 0.12, P = 0.25). Likewise, a significant correlation of ORA with manifest refraction was only found postoperatively (r = -0.38, P < 0.01). The magnitude of ORA does not seem to be a predictive factor of efficacy and safety of myopic LASIK using a solid-state laser platform. The higher relevance of PCA after surgery in some cases may explain the presence of unexpected astigmatic residual refractive errors.

Peripheral refraction in normal infant rhesus monkeys

PubMed Central

Hung, Li-Fang; Ramamirtham, Ramkumar; Huang, Juan; Qiao-Grider, Ying; Smith, Earl L.

2008-01-01

Purpose To characterize peripheral refractions in infant monkeys. Methods Cross-sectional data for horizontal refractions were obtained from 58 normal rhesus monkeys at 3 weeks of age. Longitudinal data were obtained for both the vertical and horizontal meridians from 17 monkeys. Refractive errors were measured by retinoscopy along the pupillary axis and at eccentricities of 15, 30, and 45 degrees. Axial dimensions and corneal power were measured by ultrasonography and keratometry, respectively. Results In infant monkeys, the degree of radial astigmatism increased symmetrically with eccentricity in all meridians. There were, however, initial nasal-temporal and superior-inferior asymmetries in the spherical-equivalent refractive errors. Specifically, the refractions in the temporal and superior fields were similar to the central ametropia, but the refractions in the nasal and inferior fields were more myopic than the central ametropia and the relative nasal field myopia increased with the degree of central hyperopia. With age, the degree of radial astigmatism decreased in all meridians and the refractions became more symmetrical along both the horizontal and vertical meridians; small degrees of relative myopia were evident in all fields. Conclusions As in adult humans, refractive error varied as a function of eccentricity in infant monkeys and the pattern of peripheral refraction varied with the central refractive error. With age, emmetropization occurred for both central and peripheral refractive errors resulting in similar refractions across the central 45 degrees of the visual field, which may reflect the actions of vision-dependent, growth-control mechanisms operating over a wide area of the posterior globe. PMID:18487366

Planning for Coupling Effects in Bitoric Mixed Astigmatism Ablative Treatments.

PubMed

Alpins, Noel; Ong, James K Y; Stamatelatos, George

2017-08-01

To demonstrate how to determine the historical coupling adjustments of bitoric mixed astigmatism ablative treatments and how to use these historical coupling adjustments to adjust future bitoric treatments. The individual coupling adjustments of the myopic and hyperopic cylindrical components of a bitoric treatment were derived empirically from a retrospective study where the theoretical combined treatment effect on spherical equivalent was compared to the actual change in refractive spherical equivalent. The coupling adjustments that provided the best fit in both mean and standard deviation were determined to be the historical coupling adjustments. Theoretical treatments that incorporated the historical coupling adjustments were then calculated. The actual distribution of postoperative spherical equivalent errors was compared to the theoretically adjusted distribution. The study group comprised 242 eyes and included 118 virgin right eyes and 124 virgin left eyes of 155 individuals. For the laser used, the myopic coupling adjustment was -0.02 and the hyperopic coupling adjustment was 0.30, as derived by global nonlinear optimization. This implies that almost no adjustment of the myopic component of the bitoric treatment is necessary, but that the hyperopic component of the bitoric treatment generates a large amount of unintended spherical shift. The theoretically adjusted treatments targeted zero mean spherical equivalent error, as intended, and the distribution of the theoretical spherical equivalent errors had the same spread as the distribution of actual postoperative spherical equivalent errors. Bitoric mixed astigmatism ablative treatments may display non-trivial coupling effects. Historical coupling adjustments should be taken into consideration when planning mixed astigmatism treatments to improve surgical outcomes. [J Refract Surg. 2017;33(8):545-551.]. Copyright 2017, SLACK Incorporated.

Visual impairment and spectacle use in schoolchildren in rural and urban regions in Beijing.

PubMed

Guo, Yin; Liu, Li Juan; Xu, Liang; Lv, Yan Yun; Tang, Ping; Feng, Yi; Meng, Lei; Jonas, Jost B

2014-01-01

To determine prevalence and associations of visual impairment and frequency of spectacle use among grade 1 and grade 4 students in Beijing. This school-based, cross-sectional study included 382 grade 1 children (age 6.3 ± 0.5 years) and 299 grade 4 children (age 9.4 ± 0.7 years) who underwent a comprehensive eye examination including visual acuity, noncycloplegic refractometry, and ocular biometry. Presenting visual acuity (mean 0.04 ± 0.17 logMAR) was associated with younger age (p = 0.002), hyperopic refractive error (p<0.001), and male sex (p = 0.03). Presenting visual impairment (presenting visual acuity ≤20/40 in the better eye) was found in 44 children (prevalence 6.64 ± 1.0% [95% confidence interval (CI) 4.74, 8.54]). Mean best-corrected visual acuity (right eyes -0.02 ± 0.04 logMAR) was associated with more hyperopic refractive error (p = 0.03) and rural region of habitation (p<0.001). The prevalence of best-corrected visual impairment (best-corrected visual acuity ≤20/40 in the better eye) was 2/652 (0.30 ± 0.21% [95% CI 0.00, 0.72]). Undercorrection of refractive error was present in 53 children (7.99 ± 1.05%) and was associated with older age (p = 0.003; B 0.53; OR 1.71 [95% CI 1.20, 2.42]), myopic refractive error (p = 0.001; B -0.72; OR 0.49 [95% CI 0.35, 0.68]), and longer axial length (p = 0.002; B 0.74; OR 2.10 [95% CI 1.32, 3.32]). Spectacle use was reported for 54 children (8.14 ± 1.06%). Mean refractive error of the worse eyes of these children was -2.09 ± 2.88 D (range -7.38 to +7.25 D). Factors associated with presenting visual impairment were older age, myopic refractive error, and higher maternal education level. Despite a prevalence of myopia of 33% in young schoolchildren in Greater Beijing, prevalence of best-corrected visual impairment (0.30% ± 0.21%), presenting visual impairment (6.64% ± 1.0%), and undercorrection of refractive error (7.99% ± 1.05%) were relatively low.

Relative Proportion Of Different Types Of Refractive Errors In Subjects Seeking Laser Vision Correction.

PubMed

Althomali, Talal A

2018-01-01

Refractive errors are a form of optical defect affecting more than 2.3 billion people worldwide. As refractive errors are a major contributor of mild to moderate vision impairment, assessment of their relative proportion would be helpful in the strategic planning of health programs. To determine the pattern of the relative proportion of types of refractive errors among the adult candidates seeking laser assisted refractive correction in a private clinic setting in Saudi Arabia. The clinical charts of 687 patients (1374 eyes) with mean age 27.6 ± 7.5 years who desired laser vision correction and underwent a pre-LASIK work-up were reviewed retrospectively. Refractive errors were classified as myopia, hyperopia and astigmatism. Manifest refraction spherical equivalent (MRSE) was applied to define refractive errors. Distribution percentage of different types of refractive errors; myopia, hyperopia and astigmatism. The mean spherical equivalent for 1374 eyes was -3.11 ± 2.88 D. Of the total 1374 eyes, 91.8% (n = 1262) eyes had myopia, 4.7% (n = 65) eyes had hyperopia and 3.4% (n = 47) had emmetropia with astigmatism. Distribution percentage of astigmatism (cylinder error of ≥ 0.50 D) was 78.5% (1078/1374 eyes); of which % 69.1% (994/1374) had low to moderate astigmatism and 9.4% (129/1374) had high astigmatism. Of the adult candidates seeking laser refractive correction in a private setting in Saudi Arabia, myopia represented greatest burden with more than 90% myopic eyes, compared to hyperopia in nearly 5% eyes. Astigmatism was present in more than 78% eyes.

Choroidal and scleral mechanisms of compensation for spectacle lenses in chicks.

PubMed

Wildsoet, C; Wallman, J

1995-05-01

It is known that when hyperopic or myopic defocus is imposed on chick eyes by spectacle lenses, they rapidly compensate, becoming myopic or hyperopic respectively, by altering the depth of their vitreous chamber. Changes in two components--ocular length and choroidal thickness--underlie this rapid compensation. With monocular lens treatment, hyperopic defocus imposed by negative lenses resulted in substantially increased ocular elongation and a slight thinning of the choroid, both changes resulting in myopia; myopic defocus imposed by positive lenses resulted a dramatic increase in choroidal thickness, which pushed the retina forward toward the image plane, and a slight decrease in ocular elongation, both changes resulting in hyperopia. The refractive error after 5 days of lens wear correlated well with vitreous chamber depth, which reflected the changes in both choroidal thickness and ocular length. The degree of compensation for lenses was not affected by whether the fellow eye was covered or open. Both form-deprivation myopia and lens-induced myopia declined with age in parallel, but wearing a -15 D lens produced more myopia than did form deprivation. The spectacle lenses affected the refractive error not only of the lens-wearing eye, but also, to a much lesser degree, of the untreated fellow eye. At lens removal refractive errors were opposite in sign to the lense worn, and the subsequent changes in choroidal thickness and ocular length were also opposite to those that occurred when the lenses were in place. In this situation as well, effects of the spectacle lenses on the fellow eyes were observed. Eyes with no functional afferent connection to the brain because of either prior optic nerve section or intraocular tetrodotoxin injections showed compensatory changes to imposed defocus, but these were limited to compensation for imposed myopic defocus, at least for the eyes with optic nerve section. In addition, optic nerve section, but not tetrodotoxin treatment, moved the set-point of the visual compensatory mechanism toward hyperopia. Optic nerve section prevents myopia in response to negative lenses but not to diffusers, suggesting that compensation for hyperopia requires the central nervous system.

Relation of anthropometric measurements to ocular biometric changes and refractive error in children with thalassemia.

PubMed

Elkitkat, Rania S; El-Shazly, Amany A; Ebeid, Weam M; Deghedy, Marwa R

2018-03-01

To evaluate and correlate anthropometric, biometric, and refractive error changes in thalassemia major (TM). One hundred children with TM and another hundred healthy controls were recruited. Height, weight, body mass index (BMI), and occipitofrontal circumference (OFC) were the anthropometric parameters recorded. Full ophthalmologic examination was performed, including best-corrected visual acuity, cycloplegic refraction, slit-lamp examination, Goldmann applanation tonometry, indirect ophthalmoscopy, keratometry (K readings), and ocular biometry. Compared to controls, children with TM were shorter and lighter, with a smaller BMI (p<0.001); however, no significant difference existed in OFC. Regarding ocular biometric data, patients with thalassemia had steeper mean K readings (p = 0.03), shorter axial length (AXL) (p = 0.005), shorter vitreous chamber depth (p<0.001), and thicker crystalline lens (p<0.001) than controls. Patients with thalassemia had a significant myopic shift (p = 0.003). Multiple regression analyses only showed a significant correlation between corneal astigmatism and both weight and height (β = -0.05 and p = 0.03 and β = 0.06 and p = 0.04, respectively). Spherical equivalent was significantly correlated to K readings, lens thickness, and anterior chamber depth (p<0.0001 for all parameters). Compared to controls, children with TM have significant retardation in general and ocular growth (smaller BMI and shorter AXL). Ocular growth changes probably resulted in compensatory biometric changes (steeper corneas and thicker lenses) to reach emmetropization, with an exaggerated response and subsequent myopic shift. However, growth retardation is not directly related to ocular growth changes, myopic shift, or variations in biometric parameters.

Refractive errors and binocular dysfunctions in a population of university students.

PubMed

Risovic, D J; Misailovic, K R; Eric-Marinkovic, J M; Kosanovic-Jakovic, N G; Milenkovic, S M; Petrovic, L Z

2008-01-01

This clinical study was performed to determine the presence of refractive errors and binocular dysfunctions in a population of university students. Refraction and binocular function were evaluated in a young patient population (230 students and 234 nonstudent subjects, aged 18-27 years). Distance visual acuity (DVA) and near visual acuity (NVA), refraction, cover test (CT), ocular motility, near-point of convergence, horizontal phoria measurement by Maddox wing, negative and positive vergence amplitude in prism diopters, fusion amplitude in synoptophore, as well as stereoacuity (Titmus test) were tested. Emmetropia was the most frequent refractive status in our student and nonstudent groups (78.7%). Myopia was the most frequent refractive disorder in the whole population (13.1%). Myopia and hypermetropia were significantly more frequent in the students than in nonstudents (chi-square emp 47.55). Exophoria is significantly more frequent in myopic subjects. Vergence amplitude (t test 0.000) and fusion amplitude (t test 0.005) show significantly lower values in student population. Results of Titmus test in the student group is significantly worse than in the nonstudent group (t test 0.000). Maddox wing resulted in significantly higher degree of heterophoria in the student population (t test 0.000). Myopic subjects, in the student group (t test 0.002) as well as in the nonstudent group (t test 0.001), show significantly better results in Titmus test. High near visual demand could be the most important factor for higher incidence of myopia, worse convergence and fusion amplitude, higher degree of exophoria, and worse results in Titmus test in the student population.

Interocular Difference of Peripheral Refraction in Anisomyopic Eyes of Schoolchildren

PubMed Central

Chen, Junhong; He, Ji C.; Chen, Yunyun; Xu, Jingjing; Wu, Haoran; Wang, Feifu; Lu, Fan; Jiang, Jun

2016-01-01

Purpose Refraction in the peripheral visual field is believed to play an important role in the development of myopia. The purpose of this study was to investigate the differences in peripheral refraction among anisomyopia, isomyopia, and isoemmetropia for schoolchildren. Methods Thirty-eight anisomyopic children were recruited and divided into two groups: (1) both eyes were myopic (anisomyopic group, AM group) and (2) one eye was myopic and the contralateral eye was emmetropic (emmetropic anisomyopic group, EAM group). As controls, 45 isomyopic and isoemmetropic children were also recruited with age and central spherical equivalent (SE) matched to those of the AM and EAM groups. The controls were divided into three groups: (1) intermediate myopia group (SE matched to the more myopic eye of AM group), (2) low myopia group (SE matched to the less myopic eye of AM group and the more myopic eye of EAM group), and (3) emmetropia group (SE matched to the less myopic eye of EAM group). Peripheral refraction at 7 points across the central ±30° on the horizontal visual field with a 10° interval was measured with an autorefractor. Axial length (AL), corneal curvature (CC), and anterior chamber depth (ACD) were also determined by using the Zeiss IOL-Master. Results The relative peripheral spherical equivalent [RPR(M)] and relative peripheral spherical value [RPR(S)] of the more myopic eye was shifted more hyperopically than the contralateral eye in both the AM and the EAM groups (both p<0.0001). The RPR(M, S) of the less myopic eyes in the AM and EAM groups showed a relatively flat trend across the visual field and were not significantly different from the emmetropia group. The RPR(M, S) of less myopic eyes in the AM group were shifted less hyperopically than in the isomyopic low myopia group and the more myopic eye of the EAM group [RPR(M), p = 0.007; RPR(S), p = 0.001], although the central SEs of the three groups were not significantly different from each other. However, RPR(M, S) of the more myopic eyes were not different from the corresponding isomyopic groups. There was also no significant difference in the relative peripheral astigmatism [RPR(J0, J45)] between the more and the less myopic eyes in either the AM or the EAM group. Conclusion Refraction of anisomyopia differs between the two eyes not only at the central visual field but also at the off-axis periphery. The relative peripheral refraction of the more myopic eye of anisomyopia was shifted hyperopically, as occurs in isomyopia with similar central subjective SE values. Less myopic eyes were much less hyperopically shifted in relative peripheral refraction than the corresponding isomyopic eyes, but are comparable to emmetropic eyes. This emmetropia-like relative peripheral refraction in less myopic eyes might be a factor responsible for slowing down the progression of myopia. PMID:26881745

Interocular Difference of Peripheral Refraction in Anisomyopic Eyes of Schoolchildren.

PubMed

Chen, Junhong; He, Ji C; Chen, Yunyun; Xu, Jingjing; Wu, Haoran; Wang, Feifu; Lu, Fan; Jiang, Jun

2016-01-01

Refraction in the peripheral visual field is believed to play an important role in the development of myopia. The purpose of this study was to investigate the differences in peripheral refraction among anisomyopia, isomyopia, and isoemmetropia for schoolchildren. Thirty-eight anisomyopic children were recruited and divided into two groups: (1) both eyes were myopic (anisomyopic group, AM group) and (2) one eye was myopic and the contralateral eye was emmetropic (emmetropic anisomyopic group, EAM group). As controls, 45 isomyopic and isoemmetropic children were also recruited with age and central spherical equivalent (SE) matched to those of the AM and EAM groups. The controls were divided into three groups: (1) intermediate myopia group (SE matched to the more myopic eye of AM group), (2) low myopia group (SE matched to the less myopic eye of AM group and the more myopic eye of EAM group), and (3) emmetropia group (SE matched to the less myopic eye of EAM group). Peripheral refraction at 7 points across the central ±30° on the horizontal visual field with a 10° interval was measured with an autorefractor. Axial length (AL), corneal curvature (CC), and anterior chamber depth (ACD) were also determined by using the Zeiss IOL-Master. The relative peripheral spherical equivalent [RPR(M)] and relative peripheral spherical value [RPR(S)] of the more myopic eye was shifted more hyperopically than the contralateral eye in both the AM and the EAM groups (both p<0.0001). The RPR(M, S) of the less myopic eyes in the AM and EAM groups showed a relatively flat trend across the visual field and were not significantly different from the emmetropia group. The RPR(M, S) of less myopic eyes in the AM group were shifted less hyperopically than in the isomyopic low myopia group and the more myopic eye of the EAM group [RPR(M), p = 0.007; RPR(S), p = 0.001], although the central SEs of the three groups were not significantly different from each other. However, RPR(M, S) of the more myopic eyes were not different from the corresponding isomyopic groups. There was also no significant difference in the relative peripheral astigmatism [RPR(J0, J45)] between the more and the less myopic eyes in either the AM or the EAM group. Refraction of anisomyopia differs between the two eyes not only at the central visual field but also at the off-axis periphery. The relative peripheral refraction of the more myopic eye of anisomyopia was shifted hyperopically, as occurs in isomyopia with similar central subjective SE values. Less myopic eyes were much less hyperopically shifted in relative peripheral refraction than the corresponding isomyopic eyes, but are comparable to emmetropic eyes. This emmetropia-like relative peripheral refraction in less myopic eyes might be a factor responsible for slowing down the progression of myopia.

Refractive Lenticule Implantation for Correction of Ametropia: Case Reports and Literature Review.

PubMed

Lazaridis, A; Messerschmidt-Roth, A; Sekundo, W; Schulze, S

2017-01-01

The ReLEx® technique allows correction of refractive errors through the creation and extraction of refractive stromal lenticules. Contrary to excimer laser corneal refractive procedures, where the stromal tissue is photoablated, the extracted lenticules obtained with ReLEx® can be preserved. Recent studies and case reports have described autologous re-implantation and allogeneic implantation of refractive lenticules into femtosecond-laser created stromal pockets in order to reverse the refractive outcome of a myopic corneal refractive procedure, correct hyperopia, aphakia, presbyopia and treat keratoconus. The use of stromal lenticules has also been described for therapeutic purposes, with an allogenic lenticule being transplanted under a LASIK flap in order to restore corneal volume and reduce the refractive error in a case of excessive stromal tissue removal after LASIK. This review summarises the results of the latest case reports and studies that describe the implantation of cryopreserved or fresh refractive stromal lenticules and discusses the feasibility, safety and refractive outcomes of the procedure, on the basis of published literature as well as our own experience. Georg Thieme Verlag KG Stuttgart · New York.

The Response AC/A Ratio Before and After the Onset of Myopia

PubMed Central

Mutti, Donald O.; Mitchell, G. Lynn; Jones-Jordan, Lisa A.; Cotter, Susan A.; Kleinstein, Robert N.; Manny, Ruth E.; Twelker, J. Daniel; Zadnik, Karla

2017-01-01

Purpose To investigate the ratio of accommodative convergence per diopter of accommodative response (AC/A ratio) before, during, and after myopia onset. Methods Subjects were 698 children aged 6 to 14 years who became myopic and 430 emmetropic children participating in the Collaborative Longitudinal Evaluation of Ethnicity and Refractive Error. Refractive error was measured using cycloplegic autorefraction, near work by parent survey, and the AC/A ratio by simultaneously monitoring convergence and accommodative response. The response AC/A ratios of children who became myopic were compared with age-, sex-, and ethnicity-matched model estimates for emmetropic children from 5 years before through 5 years after the onset of myopia. Results The response AC/A ratio was not significantly different between the two groups 5 years before onset, then increased monotonically in children who became myopic until reaching a plateau at myopia onset of about 7 Δ/D compared to about 4 Δ/D for children who remained emmetropic (differences between groups significant at P < 0.01 from 4 years before onset through 5 years after onset). A higher AC/A ratio was associated with greater accommodative lag but not with the rate of myopia progression regardless of the level of near work. Conclusions An increasing AC/A ratio is an early sign of becoming myopic, is related to greater accommodative lag, but does not affect the rate of myopia progression. The association with accommodative lag suggests that the AC/A ratio increase is from greater neural effort needed per diopter of accommodation rather than change in the accommodative convergence crosslink gain relationship. PMID:28291868

OUTCOMES AFTER LASER VERSUS COMBINED LASER AND BEVACIZUMAB TREATMENT FOR TYPE 1 RETINOPATHY OF PREMATURITY IN ZONE I.

PubMed

Yoon, Je Moon; Shin, Dong Hoon; Kim, Sang Jin; Ham, Don-Il; Kang, Se Woong; Chang, Yun Sil; Park, Won Soon

2017-01-01

To investigate the anatomical and refractive outcomes in patients with Type 1 retinopathy of prematurity in Zone I. The medical records of 101 eyes of 51 consecutive infants with Type 1 retinopathy of prematurity in Zone I were analyzed. Infants were treated by conventional laser photocoagulation (Group I), combined intravitreal bevacizumab injection and Zone I sparing laser (Group II), or intravitreal bevacizumab with deferred laser treatment (Group III). The proportion of unfavorable anatomical outcomes including retinal fold, disc dragging, retrolental tissue obscuring the view of the posterior pole, retinal detachment, and early refractive errors were compared among the three groups. The mean gestational age at birth and the birth weight of all 51 infants were 24.3 ± 1.1 weeks and 646 ± 143 g, respectively. In Group I, an unfavorable anatomical outcome was observed in 10 of 44 eyes (22.7%). In contrast, in Groups II and III, all eyes showed favorable anatomical outcomes without reactivation or retreatment. The refractive error was less myopic in Group III than in Groups I and II (spherical equivalent of -4.62 ± 4.00 D in Group I, -5.53 ± 2.21 D in Group II, and -1.40 ± 2.19 D in Group III; P < 0.001). In Type 1 retinopathy of prematurity in Zone I, intravitreal bevacizumab with concomitant or deferred laser therapy yielded a better anatomical outcome than conventional laser therapy alone. Moreover, intravitreal bevacizumab with deferred laser treatment resulted in less myopic refractive error.

Assessment of corneal biomechanical properties and intraocular pressure in myopic spanish healthy population.

PubMed

Del Buey, María A; Lavilla, Laura; Ascaso, Francisco J; Lanchares, Elena; Huerva, Valentín; Cristóbal, José A

2014-01-01

Purpose. To examine biomechanical parameters of the cornea in myopic eyes and their relationship with the degree of myopia in a western healthy population. Methods. Corneal hysteresis (CH), corneal resistance factor (CRF), Goldmann correlated intraocular pressure (IOP), and corneal compensated IOP (IOPcc) were measured using the ocular response analyzer (ORA) in 312 eyes of 177 Spanish subjects aged between 20 and 56 years. Refraction was expressed as spherical equivalent (SE), which ranged from 0 to -16.50 diopters (D) (mean: -3.88 ± 2.90 D). Subjects were divided into four groups according to their refractive status: group 1 or control group: emmetropia (-0.50 ≤ SE < 0.50); group 2: low myopia (-0.75 ≤ SE < 3.00 D); group 3: moderate myopia (-3.00 ≤ SE ≤ -6.00 D); and group 3: high myopia (SE greater than -6.00 D). We analyzed the relationship between corneal biomechanics measured with ORA and SE. Results. CH in the emmetropia, low myopia, moderate myopia, and high myopia groups was 11.13 ± 0.98, 11.49 ± 1.25, 10.52 ± 1.54, and 10.35 ± 1.33 mmHg, respectively. CH in the highly myopic group was significantly lower than that in the emmetropic group (P = 0.07) and low myopic group (P = 0.035); however, there were no differences with the moderate myopic group (P = 0.872). There were no statistically significant differences regarding IOP among the four groups (P > 0.05); nevertheless, IOPcc was significantly higher in the moderately myopic (15.47 ± 2.47 mmHg) and highly myopic (16.14 ± 2.59 mmHg) groups than in the emmetropia (15.15 ± 2.06 mmHg) and low myopia groups (14.53 ± 2.37 mmHg). No correlation between age and the measured parameters was found. CH and IOPcc were weakly but significantly correlated with SE (r = 0.171, P = 0.002 and r = -0.131, P = 0.021, resp.). Conclusions. Present study showed only a very weak, but significant, correlation between CH and refractive error, with CH being lower in both moderately and highly myopic eyes than that in the emmetropic and low myopic eyes. These changes in biomechanical properties of the cornea may have an impact on IOP measurement, increasing the risk of glaucoma.

The refractive state of the eye in Icelandic horses with the Silver mutation.

PubMed

Johansson, Maria K; Jäderkvist Fegraeus, Kim; Lindgren, Gabriella; Ekesten, Björn

2017-06-02

The syndrome Multiple Congenital Ocular Anomalies (MCOA) is a congenital eye disorder in horses. Both the MCOA syndrome and the Silver coat colour in horses are caused by the same missense mutation in the premelanosome protein (PMEL) gene. Horses homozygous for the Silver mutation (TT) are affected by multiple ocular defects causing visual impairment or blindness. Horses heterozygous for the Silver mutation (CT) have less severe clinical signs, usually cysts arising from the ciliary body iris or retina temporally. It is still unknown if the vision is impaired in horses heterozygous for the Silver mutation. A recent study reported that Comtois horses carrying the Silver mutation had significantly deeper anterior chambers of the eye compared to wild-type horses. This could potentially cause refractive errors. The purpose of the present study was to investigate if Icelandic horses with the Silver mutation have refractive errors compared to wild-type horses. One hundred and fifty-two Icelandic horses were included in the study, 71 CT horses and five TT horses. All horses were genotyped for the missense mutation in PMEL. Each CT and TT horse was matched by a wild-type (CC) horse of the same age ± 1 year. Skiascopy and a brief ophthalmic examination were performed in all horses. Association between refraction and age, eye, genotype and sex was tested by linear mixed-effect model analysis. TT horses with controls were not included in the statistical analyses as they were too few. The interaction between age and genotype had a significant impact on the refractive state (P = 0.0001). CT horses older than 16 years were on average more myopic than wild-type horses of the same age. No difference in the refractive state could be observed between genotypes (CT and CC) in horses younger than 16 years. TT horses were myopic (-2 D or more) in one or both eyes regardless of age. Our results indicate that an elderly Icelandic horse (older than 16 years) carrying the Silver mutation is more likely to be myopic than a wild-type horse of the same age.

Multiple regression analysis in nomogram development for myopic wavefront laser in situ keratomileusis: Improving astigmatic outcomes.

PubMed

Allan, Bruce D; Hassan, Hala; Ieong, Alvin

2015-05-01

To describe and evaluate a new multiple regression-derived nomogram for myopic wavefront laser in situ keratomileusis (LASIK). Moorfields Eye Hospital, London, United Kingdom. Prospective comparative case series. Multiple regression modeling was used to derive a simplified formula for adjusting attempted spherical correction in myopic LASIK. An adaptation of Thibos' power vector method was then applied to derive adjustments to attempted cylindrical correction in eyes with 1.0 diopter (D) or more of preoperative cylinder. These elements were combined in a new nomogram (nomogram II). The 3-month refractive results for myopic wavefront LASIK (spherical equivalent ≤11.0 D; cylinder ≤4.5 D) were compared between 299 consecutive eyes treated using the earlier nomogram (nomogram I) in 2009 and 2010 and 414 eyes treated using nomogram II in 2011 and 2012. There was no significant difference in treatment accuracy (variance in the postoperative manifest refraction spherical equivalent error) between nomogram I and nomogram II (P = .73, Bartlett test). Fewer patients treated with nomogram II had more than 0.5 D of residual postoperative astigmatism (P = .0001, Fisher exact test). There was no significant coupling between adjustments to the attempted cylinder and the achieved sphere (P = .18, t test). Discarding marginal influences from a multiple regression-derived nomogram for myopic wavefront LASIK had no clinically significant effect on treatment accuracy. Thibos' power vector method can be used to guide adjustments to the treatment cylinder alongside nomograms designed to optimize postoperative spherical equivalent results in myopic LASIK. mentioned. Copyright © 2015 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.

Relative Proportion Of Different Types Of Refractive Errors In Subjects Seeking Laser Vision Correction

PubMed Central

Althomali, Talal A.

2018-01-01

Background: Refractive errors are a form of optical defect affecting more than 2.3 billion people worldwide. As refractive errors are a major contributor of mild to moderate vision impairment, assessment of their relative proportion would be helpful in the strategic planning of health programs. Purpose: To determine the pattern of the relative proportion of types of refractive errors among the adult candidates seeking laser assisted refractive correction in a private clinic setting in Saudi Arabia. Methods: The clinical charts of 687 patients (1374 eyes) with mean age 27.6 ± 7.5 years who desired laser vision correction and underwent a pre-LASIK work-up were reviewed retrospectively. Refractive errors were classified as myopia, hyperopia and astigmatism. Manifest refraction spherical equivalent (MRSE) was applied to define refractive errors. Outcome Measures: Distribution percentage of different types of refractive errors; myopia, hyperopia and astigmatism. Results: The mean spherical equivalent for 1374 eyes was -3.11 ± 2.88 D. Of the total 1374 eyes, 91.8% (n = 1262) eyes had myopia, 4.7% (n = 65) eyes had hyperopia and 3.4% (n = 47) had emmetropia with astigmatism. Distribution percentage of astigmatism (cylinder error of ≥ 0.50 D) was 78.5% (1078/1374 eyes); of which % 69.1% (994/1374) had low to moderate astigmatism and 9.4% (129/1374) had high astigmatism. Conclusion and Relevance: Of the adult candidates seeking laser refractive correction in a private setting in Saudi Arabia, myopia represented greatest burden with more than 90% myopic eyes, compared to hyperopia in nearly 5% eyes. Astigmatism was present in more than 78% eyes. PMID:29872484

The significance of retinal image contrast and spatial frequency composition for eye growth modulation in young chicks

PubMed Central

Tran, Nina; Chiu, Sara; Tian, Yibin; Wildsoet, Christine F.

2009-01-01

Purpose This study sought further insight into the stimulus dependence of form deprivation myopia, a common response to retinal image degradation in young animals. Methods Each of 4 Bangerter diffusing filters (0.6, 0.1, <0.1, and LP (light perception only)) combined with clear plano lenses, as well as plano lenses alone, were fitted monocularly to 4-day-old chicks. Axial ocular dimensions and refractive errors were monitored over a 14-day treatment period, using high frequency A-scan ultrasonography and an autorefractor, respectively. Results Only the <0.1 and LP filters induced significant form deprivation myopia; these filters induced similarly large myopic shifts in refractive error (mean interocular differences ±SEM: -9.92 ±1.99, -7.26 ± 1.60 D respectively), coupled to significant increases in both vitreous chamber depths and optical axial lengths (p<0.001). The other 3 groups showed comparable, small changes in their ocular dimensions (p>0.05), and only small myopic shifts in refraction (<3.00 D). The myopia-inducing filters eliminated mid-and-high spatial frequency information. Conclusions Our results are consistent with emmetropization being tuned to mid-spatial frequencies. They also imply that form deprivation is not a graded phenomenon. PMID:18533221

The effect of procedure room temperature and humidity on LASIK outcomes.

PubMed

Seider, Michael I; McLeod, Stephen D; Porco, Travis C; Schallhorn, Steven C

2013-11-01

To determine whether procedure room temperature or humidity during LASIK affect refractive outcomes in a large patient sample. Retrospective cohort study. A total of 202 394 eyes of 105 712 patients aged 18 to 75 years who underwent LASIK at an Optical Express, Inc., location in their United Kingdom and Ireland centers from January 1, 2008, to June 30, 2011, who met inclusion criteria. Patient age, gender, flap creation technique, pre- and 1-month post-LASIK manifest refraction, and ambient temperature and humidity during LASIK were recorded. Effect size determination and univariate and multivariate analyses were performed to characterize the relationships between LASIK procedure room temperature and humidity and postoperative refractive outcome. One month post-LASIK manifest refraction. No clinically significant effect of procedure room temperature or humidity was found on LASIK refractive outcomes. When considering all eyes in our population, an increase of 1°C during LASIK was associated with a 0.003 diopter (D) more hyperopic refraction 1 month postoperatively, and an increase in 1% humidity was associated with a 0.0004 more myopic refraction. These effect sizes were the same or similar when considering only myopic eyes, only hyperopic eyes, and subgroups of eyes stratified by age and preoperative refractive error. Neither procedure room temperature nor humidity during LASIK were found to have a clinically significant relationship with postoperative manifest refraction in our population. Copyright © 2013 American Academy of Ophthalmology. Published by Elsevier Inc. All rights reserved.

The effect of procedure room temperature and humidity on LASIK outcomes

PubMed Central

Seider, Michael I.; McLeod, Stephen D.; Porco, Travis C.; Schallhorn, Steven C.

2013-01-01

Objective To determine if procedure room temperature and humidity during LASIK affects refractive outcomes in a very large patient sample. Design Retrospective cohort study. Participants 202,394 eyes of 105,712 patients aged 18 to 75 years old who underwent LASIK at an Optical Express, Inc. location in their United Kingdom and Ireland centers from January 1, 2008 to June 30, 2011 who met inclusion criteria. Methods Patient age, gender, pre- and one month post-LASIK manifest refraction and flap creation technique were recorded as well as the ambient temperature and humidity during LASIK. Effect size determination, in addition to univariate and multivariate analysis was performed to characterize the relationships between LASIK procedure room temperature and humidity and post-operative refractive outcome. Main Outcome Measures One month post-LASIK manifest refraction. Results No clinically significant effect of procedure room temperature or humidity was found on LASIK refractive outcomes. When considering all eyes in our population, an increase of one degree Celsius during LASIK was associated with a 0.003 diopter more hyperopic refraction one month post-operatively and an increase in one percent humidity was associated with a 0.0004 more myopic refraction. These effect sizes were the same or similar when considering only myopic eyes, only hyperopic eyes and subgroups of eyes stratified by age and pre-operative refractive error. Conclusions Procedure room temperature or humidity during LASIK was found to have no clinically significant relationship with post-operative manifest refraction in our population. PMID:23769199

Correlation between dry eye and refractive error in Saudi young adults using noninvasive Keratograph 4

PubMed Central

Fahmy, Rania M; Aldarwesh, Amal

2018-01-01

Purpose: The purpose is to study the correlation between dry eye and refractive errors in young adults using noninvasive Keratograph. Methods: In this cross sectional study, a total of 126 participants in the age range of 19–25 years and who were free of ocular surface disease, were recruited from King Saud University Campus. Refraction was defined by the spherical equivalent (SE) as the following: 49 emmetropic eyes (±0.50 SE), 48 myopic eyes (≤−0.75 SE and above), and 31 hyperopic eyes (>+0.75 SE). All participants underwent full ophthalmic examinations assessing their refractive status and dryness level including noninvasive breakup time (NIBUT) and tear meniscus height using Keratograph 4. Results: The prevalence of dry eye was 24.6%, 36.5%, and 17.4% in emmetropes, myopes, and hypermetropes, respectively. NIBUT has a negative correlation with hyperopia and a positive correlation with myopia with a significant reduction in the average NIBUT in myopes and hypermetropes in comparison to emmetropes. Conclusion: The current results succeeded to demonstrate a correlation between refractive errors and dryness level. PMID:29676308

Analysis of Macular and Retinal Nerve Fiber Layer Thickness in Children with Refractory Amblyopia after Femtosecond Laser-assisted Laser In situ Keratomileusis: A Retrospective Study.

PubMed

Zhao, Peng-Fei; Zhou, Yue-Hua; Zhang, Jing; Wei, Wen-Bin

2017-09-20

Localized macular edema and retinal nerve fiber layer (RNFL) thinning have been reported shortly after laser in situ keratomileusis (LASIK) in adults. However, it is still unclear how LASIK affects the retina of children. This study aimed to investigate the macular retina and RNFL thickness in children with refractive amblyopia who underwent femtosecond laser-assisted LASIK (FS-LASIK). In this study, we included 56 eyes of 32 patients with refractive amblyopia who underwent FS-LASIK in our hospital from January 2012 to December 2016. Foveal (foveal center retinal, parafoveal retinal, and perifoveal), macular inner retinal (superior and inferior), and peripapillary RNFL thicknesses (superior, inferior, temporal, and nasal) were measured using Fourier-domain optical coherence tomography before surgery and 1 day, 3 days, and 1 week after surgery. We divided these patients into three groups based on their refractive error: High myopic group with 22 eyes (equivalent sphere, >6.00 D), mild myopic group with 19 eyes (equivalent sphere, 0-6.00 D), and hyperopic group with 15 eyes (equivalent sphere, >+0.50 D). We compared the macular retina and RNFL thickness before and after LASIK. A paired simple t-test was used for data analysis. One week after surgery, the visual acuity for all 56 eyes of the 32 patients reached their preoperative best-corrected vision. Visual acuity improved two lines or better for 31% of the patients. The residual refractive errors in 89% of the patients were within ±0.5 D. In the high myopic group, the foveal center retinal and parafoveal retinal thicknesses were thicker 1 day and 3 days after surgery than before surgery (t = 2.689, P = 0.012; t = 2.383, P = 0.018, respectively); no significant difference was found 1 week after surgery (P > 0.05). The foveal center retinal and parafoveal retinal thicknesses were greater 1 day after surgery than they were before surgery (P = 0.000 and P = 0.005, respectively) in the mild myopic and hyperopic groups. No significant difference was found 3 days or 1 week after surgery (P > 0.05). In all three groups, no significant difference was found in the macular inner retinal or peripapillary RNFL thickness 1 day, 3 days, or 1 week after surgery (P > 0.05). The foveal center retinal edema after FS-LASIK is mild and reversible in children, that mostly occurred in the high myopic group with no effect on the visual acuity, and is always relieved within 1 week.

A Model of the Effect of Lens Development on Refraction in Schoolchildren.

PubMed

He, Ji C

2017-12-01

The study provides a new theory on the mechanism underlying myopia development, and it could be useful in clinical practice to control myopia development in schoolchildren. To model the effect of the crystalline lens on refractive development in schoolchildren. The Zemax 13 was used to calculate Zernike aberrations and refractions across 50° horizontal visual fields. Optical effects of the anterior chamber depth, lens thickness, and radii of curvature of the lens surfaces on refractions were modeled. Refractive changes induced by lens development in emmetropic and myopic eyes, based on a previous longitudinal study from literature, were calculated. A lens thickness reduction with an anterior chamber depth deepening caused a hyperopic shift over the visual fields and even more at the periphery. Opposite effects were found when the lens was thinned without any change of the anterior chamber depth. While a flattening of the anterior lens surface produced hyperopic refractions overall, a posterior lens flattening caused a myopic shift at the periphery, but a hyperopic shift of the central refraction. In the myopic eye, lens development induced refractive change toward more hyperopic over the visual fields and more at the periphery. Lens thinning and lens axial movement participate in peripheral refractive development in schoolchildren, and lens development with a deeper anterior chamber depth and a flatter lens surface in the myopic eye could generate extra hyperopia over visual fields. The myopic lens development could be due to a backward movement of the lens, driven by a backward growth of the ciliary process, which might be a causative factor of myopia development.

The BHVI-EyeMapper: peripheral refraction and aberration profiles.

PubMed

Fedtke, Cathleen; Ehrmann, Klaus; Falk, Darrin; Bakaraju, Ravi C; Holden, Brien A

2014-10-01

The aim of this article was to present the optical design of a new instrument (BHVI-EyeMapper, EM), which is dedicated to rapid peripheral wavefront measurements across the visual field for distance and near, and to compare the peripheral refraction and higher-order aberration profiles obtained in myopic eyes with and without accommodation. Central and peripheral refractive errors (M, J180, and J45) and higher-order aberrations (C[3, 1], C[3, 3], and C[4, 0]) were measured in 26 myopic participants (mean [±SD] age, 20.9 [±2.0] years; mean [±SD] spherical equivalent, -3.00 [±0.90] diopters [D]) corrected for distance. Measurements were performed along the horizontal visual field with (-2.00 to -5.00 D) and without (+1.00 D fogging) accommodation. Changes as a function of accommodation were compared using tilt and curvature coefficients of peripheral refraction and aberration profiles. As accommodation increased, the relative peripheral refraction profiles of M and J180 became significantly (p < 0.05) more negative and the profile of M became significantly (p < 0.05) more asymmetric. No significant differences were found for the J45 profiles (p > 0.05). The peripheral aberration profiles of C[3, 1], C[3, 3], and C[4, 0] became significantly (p < 0.05) less asymmetric as accommodation increased, but no differences were found in the curvature. The current study showed that significant changes in peripheral refraction and higher-order aberration profiles occurred during accommodation in myopic eyes. With its extended measurement capabilities, that is, permitting rapid peripheral refraction and higher-order aberration measurements up to visual field angles of ±50 degrees for distance and near (up to -5.00 D), the EM is a new advanced instrument that may provide additional insights in the ongoing quest to understand and monitor myopia development.

The BHVI-EyeMapper: Peripheral Refraction and Aberration Profiles

PubMed Central

Fedtke, Cathleen; Ehrmann, Klaus; Falk, Darrin; Bakaraju, Ravi C.; Holden, Brien A.

2014-01-01

ABSTRACT Purpose The aim of this article was to present the optical design of a new instrument (BHVI-EyeMapper, EM), which is dedicated to rapid peripheral wavefront measurements across the visual field for distance and near, and to compare the peripheral refraction and higher-order aberration profiles obtained in myopic eyes with and without accommodation. Methods Central and peripheral refractive errors (M, J180, and J45) and higher-order aberrations (C[3, 1], C[3, 3], and C[4, 0]) were measured in 26 myopic participants (mean [±SD] age, 20.9 [±2.0] years; mean [±SD] spherical equivalent, −3.00 [±0.90] diopters [D]) corrected for distance. Measurements were performed along the horizontal visual field with (−2.00 to −5.00 D) and without (+1.00 D fogging) accommodation. Changes as a function of accommodation were compared using tilt and curvature coefficients of peripheral refraction and aberration profiles. Results As accommodation increased, the relative peripheral refraction profiles of M and J180 became significantly (p < 0.05) more negative and the profile of M became significantly (p < 0.05) more asymmetric. No significant differences were found for the J45 profiles (p > 0.05). The peripheral aberration profiles of C[3, 1], C[3, 3], and C[4, 0] became significantly (p < 0.05) less asymmetric as accommodation increased, but no differences were found in the curvature. Conclusions The current study showed that significant changes in peripheral refraction and higher-order aberration profiles occurred during accommodation in myopic eyes. With its extended measurement capabilities, that is, permitting rapid peripheral refraction and higher-order aberration measurements up to visual field angles of ±50 degrees for distance and near (up to −5.00 D), the EM is a new advanced instrument that may provide additional insights in the ongoing quest to understand and monitor myopia development. PMID:25105690

Myopia Control: A Review.

PubMed

Walline, Jeffrey J

2016-01-01

Slowing the progression of myopia has become a considerable concern for parents of myopic children. At the same time, clinical science is rapidly advancing the knowledge about methods to slow myopia progression. This article reviews the peer-reviewed literature regarding several modalities attempting to control myopia progression. Several strategies have been shown to be ineffective for myopia control, including undercorrection of myopic refractive error, alignment fit gas-permeable contact lenses, outdoor time, and bifocal of multifocal spectacles. However, a recent randomized clinical trial fitted progressing myopic children with executive bifocals for 3 years and found a 39% slowing of myopia progression for bifocal-only spectacles and 50% treatment effect for bifocal spectacles with base-in prism, although there was not a significant difference in progression between the bifocal-only and bifocal plus prism groups. Interestingly, outdoor time has shown to be effective for reducing the onset of myopia but not for slowing the progression of myopic refractive error. More effective methods of myopia control include orthokeratology, soft bifocal contact lenses, and antimuscarinic agents. Orthokeratology and soft bifocal contact lenses are both thought to provide myopic blur to the retina, which acts as a putative cue to slow myopic eye growth. Each of these myopia control methods provides, on average, slightly less than 50% slowing of myopia progression. All studies have shown clinically meaningful slowing of myopia progression, including several randomized clinical trials. The most investigated antimuscarinic agents include pirenzepine and atropine. Pirenzepine slows myopia progression by approximately 40%, but it is not commercially available in the United States. Atropine provides the best myopia control, but the cycloplegic and mydriatic side effects render it a rarely prescribed myopia control agent in the United States. However, low-concentration atropine has been shown to provide effective myopia control with far fewer side effects than 1.0% atropine. Finally, two agents, low-concentration atropine and outdoor time have been shown to reduce the likelihood of myopia onset. Over the past few years, much has been learned about how to slow the progression of nearsightedness in children, but we still have a lot to learn.

Prevalence of amblyopia and refractive errors in an unscreened population of children.

PubMed

Polling, Jan-Roelof; Loudon, Sjoukje E; Klaver, Caroline C W

2012-11-01

To describe the frequency of refractive errors and amblyopia in unscreened children aged 2 months to 12 years from a rural town in Poland. Five hundred ninety-one children were identified by medical records and examined in a standardized manner.Visual acuity was measured using LogMAR charts; refractive error was determined using retinoscopy or autorefraction after cycloplegia. Myopia was defined as spherical equivalent (SE) ≤ -0.50 D, emmetropia as SE between -0.5 D and+0.5 D, mild hyperopia as SE between +0.5 D and +2.0 D, and high hyperopia as SE Q+2.0 D. Amblyopia was classified as best-corrected visual acuity ≥0.3 (≤ 20/40) LogMAR, in combination with a 2 LogMAR line difference between the two eyes and the presence of an amblyogenic factor. Refractive errors ranged from 84.2% in children aged up to 2 years to 75.5% in those aged 10 to 12 years.Refractive error showed a myopic shift with age; myopia prevalence increased from 2.2% in those aged 6 to 7 years to 6.3% in those aged 10 to 12 years. Of the examined children, 77 (16.3%) had refractive errors, with visual loss; of these,60 (78%) did not use corrections. The prevalence of amblyopia was 3.1%, and refractive error attributed to the amblyopiain 9 of 13 (69%) children. Refractive errors are common in Caucasian children and often remain undiagnosed. The prevalence of amblyopia was three times higher in this unscreened population compared with screened populations. Greater awarenessof these common treatable visual conditions in children is warranted.

Refractive states of eyes and associations between ametropia and age, breed, and axial globe length in domestic cats.

PubMed

Konrade, Kricket A; Hoffman, Allison R; Ramey, Kelli L; Goldenberg, Ruby B; Lehenbauer, Terry W

2012-02-01

To determine the refractive states of eyes in domestic cats and to evaluate correlations between refractive error and age, breed, and axial globe measurements. 98 healthy ophthalmologically normal domestic cats. The refractive state of 196 eyes (2 eyes/cat) was determined by use of streak retinoscopy. Cats were considered ametropic when the mean refractive state was ≥ ± 0.5 diopter (D). Amplitude-mode ultrasonography was used to determine axial globe length, anterior chamber length, and vitreous chamber depth. Mean ± SD refractive state of all eyes was -0.78 ± 1.37 D. Mean refractive error of cats changed significantly as a function of age. Mean refractive state of kittens (≤ 4 months old) was -2.45 ± 1.57 D, and mean refractive state of adult cats (> 1 year old) was -0.39 ± 0.85 D. Mean axial globe length, anterior chamber length, and vitreous chamber depth were 19.75 ± 1.59 mm, 4.66 ± 0.86 mm, and 7.92 ± 0.86 mm, respectively. Correlations were detected between age and breed and between age and refractive states of feline eyes. Mean refractive error changed significantly as a function of age, and kittens had greater negative refractive error than did adult cats. Domestic shorthair cats were significantly more likely to be myopic than were domestic mediumhair or domestic longhair cats. Domestic cats should be included in the animals in which myopia can be detected at a young age, with a likelihood of progression to emmetropia as cats mature.

Retinal measurements using time domain optical coherence tomography imaging before and after myopic Lasik

PubMed Central

Lei, Feng; Burns, Stephen A.; shao, Liqin; Yang, Yabo

2014-01-01

Purpose To compare retinal measurements obtained by time domain optical coherence tomography (OCT) devices before and after myopic laser in situ keratomileusis (Lasik) and to assess the interaction of Lasik and retinal structures as measured by time domain OCT. Methods 53 patients randomly selected participated in the study. Only the right eye of each subject was included in the study. Comprehensive ophthalmic examinations including refraction examination, slitlamp examination, dilated fundus examination, corneal topography, corneal thickness, intraocular pressure, and retinal Stratus OCT scans were acquired for each patient before myopic Lasik and 3 months after surgery. Results Total macular volume (TMV) changed significantly between preoperative and postoperative measurements (p=0.003). No statistical differences were found between preoperative and postoperative disc area, rim area, cup/disk vert. ratio, or average foveal thickness (p>0.05). The variation in TMV correlated significantly with the change in spherical refraction equivalent, maximal corneal curvature, minimal corneal curvature, and corneal ablation depth. Conclusion Most retinal OCT measurements undergo no obvious changes after myopic Lasik. The increased TMV measurements we measured after Lasik seem to be correlated with the alteration in corneal shape. The exact mechanism for this change is not clear, while we examined several possibilities including subclinical macular edema, magnification changes, errors in OCT analysis and IOP, none of these seem to be a likely cause. PMID:22512373

Influence of Near Tasks on Posture in Myopic Chinese Schoolchildren

PubMed Central

Bao, Jinhua; Drobe, Björn; Wang, Yuwen; Chen, Ke; Seow, Eu Jin; Lu, Fan

2015-01-01

ABSTRACT Purpose To investigate near-vision posture in Chinese myopic schoolchildren and compare near-vision posture during different near-vision tasks (i.e., playing video games, reading, and writing). Methods The study investigated 120 myopic children (grades 1 through 6 and aged 6 to 13 years). An electromagnetic motion-tracking system was used for continuous measurements of the working distance and head declination of the subjects while they were playing video games or reading or writing at a desk. The reading and writing documents were adjusted by grade level (i.e., grades 1 to 2, 3 to 4, and 5 to 6). For analysis, the subjects were grouped in two refractive groups according to their median spherical equivalent refractive error (−1.50D). Results The myopic schoolchildren used close working distances for all tasks: 21.3 ± 5.2 cm (video games), 27.2 ± 6.4 cm (reading), and 24.9 ± 5.8 cm (writing). The mean head declinations were 63.5 ± 12.2 deg (video games), 37.1 ± 12.8 deg (reading), and 44.5 ± 14.1 deg (writing). Working distance decreased significantly across time for the reading and writing tasks (p < 0.001). Head declination increased significantly across time only for the reading task (p < 0.001). Grade level significantly influenced working distance, but the difference was not significant when working distance was adjusted by the subject’s size. No differences were observed within the refractive or the accommodative lag groups in terms of the posture data (p > 0.05). Working distance was negatively correlated with head declination (r = −0.53, p < 0.001). Conclusions Close working distances were observed for Chinese myopic schoolchildren. The attention dedicated to each task, the task difficulty, and the page/screen size may affect near working distance and head declination. Handheld video games were associated with the closest working distance, which may be a risk factor for myopia progression, according to previous studies. PMID:26107025

Correlation between refraction level and retinal breaks in myopic eye.

PubMed

Alimanović-Halilović, Emina

2008-11-01

In this study we analyzed 180 myopic eyes in order to determine the refraction that is "critical" for the occurrence of retinal breaks as a main cause of retinal detachment. Detachment of retina involves separation of the neurosensory retina from the pigmented epithelium with the severe impairment of vision. After the focused ophthalmological assessment, determination of objective refraction, indirect binocular ophthalmoscopy, we compared the diagnosed retinal breaks according to the shape with the refraction. All the examined eyes were divided into six groups according to the axis length. Mean age of our patients was between 48,43 and 51,60 years with SD ranging from 13,88 to 18,45. The age differences among the groups were not statistically significant. This study included 102 (56,7%) male and 78 (43,3%) female patients and no statistically significant differences between genders was found regarding the occurrence of retinal breaks compared to refraction. The most dominant ruptures were the round ones (28,2%), followed by oval (25%), the category of multiple small holes (19,2%), horseshoe shaped (15,3%), and finally holes with operculum. In cases with myopic refraction ranging between 3,50 and 7,49 dsph, the frequency of retinal breaks statistically significantly differs from all other analyzed refractions. Also, there is positive correlation between the above mentioned myopic refraction and the frequency of retinal breaks. In order to prevent retinal detachment in a myopic eye, we suggest further thorough examinations of the eye fundus in patients with the above mentioned myopia. Diagnosing retinal breaks involves the application of adequate therapy: laser photocoagulation, cryotherapy, sclera buckling and pneumatic retinopexy.

Self-refraction accuracy with adjustable spectacles among children in Ghana.

PubMed

Ilechie, Alex Azuka; Abokyi, Samuel; Owusu-Ansah, Andrew; Boadi-Kusi, Samuel Bert; Denkyira, Andrew Kofi; Abraham, Carl Halladay

2015-04-01

To determine the accuracy of self-refraction (SR) in myopic teenagers, we compared visual and refractive outcomes of self-refracting spectacles (FocusSpecs) with those obtained using cycloplegic subjective refraction (CSR) as a gold standard. A total of 203 eligible schoolchildren (mean [±SD] age, 13.8 [±1.0] years; 59.1% were female) completed an examination consisting of SR with FocusSpecs adjustable spectacles, visual acuity with the logMAR (logarithm of the minimum angle of resolution) chart, cycloplegic retinoscopy, and CSR. Examiners were masked to the SR findings. Wilcoxon signed rank test and paired Student t test were used to compare measures across refraction methods (95% confidence intervals [CIs]). The mean (±SD) spherical equivalent refractive error measured by CSR and SR was -1.22 (±0.49) diopters (D) and -1.66 (±0.73) D, respectively, a statistically significant difference of -0.44 D (p < 0.001, t = 15.517). The greatest proportion of participants was correctable to visual acuity greater than or equal to 6/7.5 (logMAR 0.1) in the better eye by CSR (99.0%; 95% CI, 96.5 to 99.7%), followed by cycloplegic retinoscopy (94.1%; 95% CI, 90.0 to 96.6%) and SR (85.2%; 95% CI, 79.7 to 89.5%). These proportions differed significantly from each other (p < 0.001, Wilcoxon signed rank test). Myopic inaccuracy of greater than 0.50 D and greater than or equal to -1.00 D was present in 29 (15.3%) and 16 (8.4%) right eyes, respectively, with SR. In logistic regression models, failure to achieve visual acuity greater than or equal to 6/7.5 in right eyes with SR was significantly associated with age (odds ratio, 1.92; 95% CI, 1.12 to 3.28; p = 0.017) and spherical power (odds ratio, 0.017; 95% CI, 0.005 to 0.056; p < 0.001). Self-refraction offers acceptable visual and refractive results for young people in a rural setting in Ghana, although myopic inaccuracy in the more negative direction occurred in some children.

Prevalence of refractive errors in the Slovak population calculated using the Gullstrand schematic eye model.

PubMed

Popov, I; Valašková, J; Štefaničková, J; Krásnik, V

2017-01-01

A substantial part of the population suffers from some kind of refractive errors. It is envisaged that their prevalence may change with the development of society. The aim of this study is to determine the prevalence of refractive errors using calculations based on the Gullstrand schematic eye model. We used the Gullstrand schematic eye model to calculate refraction retrospectively. Refraction was presented as the need for glasses correction at a vertex distance of 12 mm. The necessary data was obtained using the optical biometer Lenstar LS900. Data which could not be obtained due to the limitations of the device was substituted by theoretical data from the Gullstrand schematic eye model. Only analyses from the right eyes were presented. The data was interpreted using descriptive statistics, Pearson correlation and t-test. The statistical tests were conducted at a level of significance of 5%. Our sample included 1663 patients (665 male, 998 female) within the age range of 19 to 96 years. Average age was 70.8 ± 9.53 years. Average refraction of the eye was 2.73 ± 2.13D (males 2.49 ± 2.34, females 2.90 ± 2.76). The mean absolute error from emmetropia was 3.01 ± 1.58 (males 2.83 ± 2.95, females 3.25 ± 3.35). 89.06% of the sample was hyperopic, 6.61% was myopic and 4.33% emmetropic. We did not find any correlation between refraction and age. Females were more hyperopic than males. We did not find any statistically significant hypermetopic shift of refraction with age. According to our estimation, the calculations of refractive errors using the Gullstrand schematic eye model showed a significant hypermetropic shift of more than +2D. Our results could be used in future for comparing the prevalence of refractive errors using same methods we used.Key words: refractive errors, refraction, Gullstrand schematic eye model, population, emmetropia.

Refraction in Adults with Diabetes

PubMed Central

Klein, Barbara E. K.; Lee, Kristine E.; Klein, Ronald

2010-01-01

Objective(s) Examine refraction, change in refraction, and risk factors for change in refraction in adults with type 1 and type 2 diabetes. Methods Population based study. Modified Early Treatment of Diabetic Retinopathy Study refractions and a standard history were obtained for all participants. Baseline and ten-year follow-up data were available. Results Age was significantly associated with refraction in persons with younger-onset diabetes (T1D) and those with older-onset diabetes (T2D); refractions were similar for both groups. Persons of similar age with T1D were likely to be more myopic than those with T2D (P<.01). Years of education were significantly associated with more myopic refraction (P<.0001). In those with T1D on average there was a −.35 diopter (D) change in refraction over 10 years. However, there was a systematic decrease in myopic shift with increasing age at baseline. Those with longer duration of diabetes and with proliferative retinopathy were more likely to have hyperopic shifts in refraction. In those with T2D there was, on average, a +.25D change in refraction over the 10 years but there was little consistency in the amount of change by age at baseline. There were no other significant effects on change in refraction in this group. Conclusions In persons of similar age, those with T1D are likely to be slightly more myopic than those with T2D. Overall, mean refractions and the important risk factors of age and education are similar to those reported in non-diabetic populations. PMID:21220629

Wnt Signaling in Form Deprivation Myopia of the Mice Retina

PubMed Central

Ma, Mingming; Zhang, Zhengwei; Du, Ergang; Zheng, Wenjing; Gu, Qing; Xu, Xun; Ke, Bilian

2014-01-01

Background The canonical Wnt signaling pathway plays important roles in cellular proliferation and differentiation, axonal outgrowth, cellular maintenance in retinas. Here we test the hypothesis that elements of the Wnt signaling pathway are involved in the regulation of eye growth and prevention of myopia, in the mouse form-deprivation myopia model. Methodology/Principal Findings (1) One hundred twenty-five C57BL/6 mice were randomly distributed into form-deprivation myopia and control groups. Form-deprivation myopia (FDM) was induced by suturing the right eyelid, while the control group received no treatment. After 1, 2, and 4 weeks of treatment, eyes were assessed in vivo by cycloplegic retinoscopic refraction and axial length measurement by photography or A-scan ultrasonography. Levels of retinal Wnt2b, Fzd5 and β-catenin mRNA and protein were evaluated using RT-PCR and western blotting, respectively. (2) Another 96 mice were divided into three groups: control, drugs-only, and drugs+FDM (by diffuser). Experimentally treated eyes in the last two groups received intravitreal injections of vehicle or the proteins, DKK-1 (Wnt-pathway antagonist) or Norrin (Wnt-pathway agonist), once every three days, for 4 injections total. Axial length and retinoscopic refraction were measured on the 14th day of form deprivation. Following form-deprivation for 1, 2, and 4 weeks, FDM eyes had a relatively myopic refractive error, compared with contralateral eyes. There were no significant differences in refractive error between right and left eye in control group. The amounts of Wnt2b, Fzd5 and β-catenin mRNA and protein were significantly greater in form-deprived myopia eyes than in control eyes.DKK-1 (antagonist) reduced the myopic shift in refractive error and increase in axial elongation, whereas Norrin had the opposite effect in FDM eyes. Conclusions/Significance Our studies provide the first evidence that the Wnt2b signaling pathway may play a role in the development and progression of form-deprivation myopia, in a mammalian model. PMID:24755605

Wnt signaling in form deprivation myopia of the mice retina.

PubMed

Ma, Mingming; Zhang, Zhengwei; Du, Ergang; Zheng, Wenjing; Gu, Qing; Xu, Xun; Ke, Bilian

2014-01-01

The canonical Wnt signaling pathway plays important roles in cellular proliferation and differentiation, axonal outgrowth, cellular maintenance in retinas. Here we test the hypothesis that elements of the Wnt signaling pathway are involved in the regulation of eye growth and prevention of myopia, in the mouse form-deprivation myopia model. (1) One hundred twenty-five C57BL/6 mice were randomly distributed into form-deprivation myopia and control groups. Form-deprivation myopia (FDM) was induced by suturing the right eyelid, while the control group received no treatment. After 1, 2, and 4 weeks of treatment, eyes were assessed in vivo by cycloplegic retinoscopic refraction and axial length measurement by photography or A-scan ultrasonography. Levels of retinal Wnt2b, Fzd5 and β-catenin mRNA and protein were evaluated using RT-PCR and western blotting, respectively. (2) Another 96 mice were divided into three groups: control, drugs-only, and drugs+FDM (by diffuser). Experimentally treated eyes in the last two groups received intravitreal injections of vehicle or the proteins, DKK-1 (Wnt-pathway antagonist) or Norrin (Wnt-pathway agonist), once every three days, for 4 injections total. Axial length and retinoscopic refraction were measured on the 14th day of form deprivation. Following form-deprivation for 1, 2, and 4 weeks, FDM eyes had a relatively myopic refractive error, compared with contralateral eyes. There were no significant differences in refractive error between right and left eye in control group. The amounts of Wnt2b, Fzd5 and β-catenin mRNA and protein were significantly greater in form-deprived myopia eyes than in control eyes.DKK-1 (antagonist) reduced the myopic shift in refractive error and increase in axial elongation, whereas Norrin had the opposite effect in FDM eyes. Our studies provide the first evidence that the Wnt2b signaling pathway may play a role in the development and progression of form-deprivation myopia, in a mammalian model.

The longitudinal orthokeratology research in children (LORIC) in Hong Kong: a pilot study on refractive changes and myopic control.

PubMed

Cho, Pauline; Cheung, Sin Wan; Edwards, Marion

2005-01-01

Myopia is a common ocular disorder, and progression of myopia in children is of increasing concern. Modern overnight orthokeratology (ortho-k) is effective for myopic reduction and has been claimed to be effective in slowing the progression of myopia (myopic control) in children, although scientific evidence for this has been lacking. This 2 year pilot study was conducted to determine whether ortho-k can effectively reduce and control myopia in children. We monitored the growth of axial length (AL) and vitreous chamber depth (VCD) in 35 children (7-12 years of age), undergoing ortho-k treatment and compared the rates of change with 35 children wearing single-vision spectacles from an earlier study (control). For the ortho-k subjects, we also determined the changes in corneal curvature and the relationships with changes of refractive errors, AL and VCD. The baseline spherical equivalent refractive errors (SER), the AL, and VCD of the ortho-k and control subjects were not statistically different. All the ortho-k subjects found post-ortho-k unaided vision acceptable in the daytime. The residual SER at the end of the study was -0.18 +/- 0.69 D (dioptre) and the reduction (less myopic) in SER was 2.09 +/- 1.34 D (all values are mean +/- SD). At the end of 24 months, the increases in AL were 0.29 +/- 0.27 mm and 0.54 +/- 0.27 mm for the ortho-k and control groups, respectively (unpaired t test; p = 0.012); the increases in VCD were 0.23 +/- 0.25 mm and 0.48 +/- 0.26 mm for the ortho-k and control groups, respectively (p = 0.005). There was significant initial corneal flattening in the ortho-k group but no significant relationships were found between changes in corneal power and changes in AL and VCD. Ortho-k can have both a corrective and preventive/control effect in childhood myopia. However, there are substantial variations in changes in eye length among children and there is no way to predict the effect for individual subjects.

Correlation of major components of ocular astigmatism in myopic patients.

PubMed

Mohammadpour, Mehrdad; Heidari, Zahra; Khabazkhoob, Mehdi; Amouzegar, Afsaneh; Hashemi, Hassan

2016-02-01

To investigate the correlation of major components of ocular astigmatism in myopic patients in an academic hospital. This cross-sectional study was conducted on 376 eyes of 188 patients who were referred to Farabi Eye Hospital for refractive surgery. Preoperative examinations including refraction and corneal topography were performed for all candidates to measure refractive and corneal astigmatism. Ocular residual astigmatism was calculated using vector analysis. Pearson's correlation and ANOVA analysis were used to evaluate the strength of the association between different types of astigmatism. Both eyes were defined as cluster and the Generalized Estimating Equations (GEE) analysis were performed. Mean age of 119 women (63.3%) and 69 men (36.7%) was 27.8 ± 5.7 years. Mean refractive error based on spherical equivalent was -3.59 ± 1.95D (range, -0.54 to -10.22D). Mean refractive and corneal astigmatism was 1.97 ± 1.3D and 1.85 ± 1.01D, respectively. Mean amount of ORA was 0.65 ± 0.36D.There was a significant correlation between ORA and refractive astigmatism(r=0.23, p<0.001), corneal and refractive astigmatism (r=0.91, p<0.001) and a weak correlation between ORA and corneal astigmatism (r=0.13, p=0.014). There was a significant correlation between J0 and J45 values of ORA and corneal astigmatism (p<0.001). There is a significant correlation between ORA and refractive astigmatism, refractive and corneal astigmatism and a weak correlation between ORA and corneal astigmatism in refractive surgery candidates. Identifying the type of astigmatism and preoperative measurement of ocular residual astigmatism is highly recommended prior to any refractive surgery, especially in cases with significant astigmatism. Copyright © 2015 Elsevier Ltd. All rights reserved.

Baseline peripheral refractive error and changes in axial refraction during one year in a young adult population.

PubMed

Hartwig, Andreas; Charman, William Neil; Radhakrishnan, Hema

2016-01-01

To determine whether the initial characteristics of individual patterns of peripheral refraction relate to subsequent changes in refraction over a one-year period. 54 myopic and emmetropic subjects (mean age: 24.9±5.1 years; median 24 years) with normal vision were recruited and underwent conventional non-cycloplegic subjective refraction. Peripheral refraction was also measured at 5° intervals over the central 60° of horizontal visual field, together with axial length. After one year, measurements of subjective refraction and axial length were repeated on the 43 subjects who were still available for examination. In agreement with earlier studies, higher myopes tended to show greater relative peripheral hyperopia. There was, however, considerable inter-subject variation in the pattern of relative peripheral refractive error (RPRE) at any level of axial refraction. Across the group, mean one-year changes in axial refraction and axial length did not differ significantly from zero. There was no correlation between changes in these parameters for individual subjects and any characteristic of their RPRE. No evidence was found to support the hypothesis that the pattern of RPRE is predictive of subsequent refractive change in this age group. Copyright © 2015 Spanish General Council of Optometry. Published by Elsevier Espana. All rights reserved.

Refractive Error, Visual Acuity and Causes of Vision Loss in Children in Shandong, China. The Shandong Children Eye Study

PubMed Central

Wu, Jian Feng; Bi, Hong Sheng; Wang, Shu Mei; Hu, Yuan Yuan; Wu, Hui; Sun, Wei; Lu, Tai Liang; Wang, Xing Rong; Jonas, Jost B.

2013-01-01

Purpose To examine the prevalence of refractive errors and prevalence and causes of vision loss among preschool and school children in East China. Methods Using a random cluster sampling in a cross-sectional school-based study design, children with an age of 4–18 years were selected from kindergartens, primary schools, and junior and senior high schools in the rural Guanxian County and the city of Weihai. All children underwent a complete ocular examination including measurement of uncorrected (UCVA) and best corrected visual acuity (BCVA) and auto-refractometry under cycloplegia. Myopia was defined as refractive error of ≤−0.5 diopters (D), high myopia as ≤−6.0D, and amblyopia as BCVA ≤20/32 without any obvious reason for vision reduction and with strabismus or refractive errors as potential reasons. Results Out of 6364 eligible children, 6026 (94.7%) children participated. Prevalence of myopia (overall: 36.9±0.6%;95% confidence interval (CI):36.0,38.0) increased (P<0.001) from 1.7±1.2% (95%CI:0.0,4.0) in the 4-years olds to 84.6±3.2% (95%CI:78.0,91.0) in 17-years olds. Myopia was associated with older age (OR:1.56;95%CI:1.52,1.60;P<0.001), female gender (OR:1.22;95%CI:1.08,1.39;P = 0.002) and urban region (OR:2.88;95%CI:2.53,3.29;P<0.001). Prevalence of high myopia (2.0±0.2%) increased from 0.7±0.3% (95%CI:0.1,1.3) in 10-years olds to 13.9±3.0 (95%CI:7.8,19.9) in 17-years olds. It was associated with older age (OR:1.50;95%CI:1.41,1.60;P<0.001) and urban region (OR:3.11;95%CI:2.08,4.66);P<0.001). Astigmatism (≥0.75D) (36.3±0.6%;95%CI:35.0,38.0) was associated with older age (P<0.001;OR:1.06;95%CI:1.04,1.09), more myopic refractive error (P<0.001;OR:0.94;95%CI:0.91,0.97) and urban region (P<0.001;OR:1.47;95%CI:1.31,1.64). BCVA was ≤20/40 in the better eye in 19 (0.32%) children. UCVA ≤20/40 in at least one eye was found in 2046 (34.05%) children, with undercorrected refractive error as cause in 1975 (32.9%) children. Amblyopia (BCVA ≤20/32) was detected in 44 (0.7%) children (11 children with bilateral amblyopia). Conclusions In coastal East China, about 14% of the 17-years olds were highly myopic, and 80% were myopic. Prevalence of myopia increased with older age, female gender and urban region. About 0.7% of pre-school children and school children were amblyopic. PMID:24376575

Paediatric Refractive Errors in an Eye Clinic in Osogbo, Nigeria.

PubMed

Michaeline, Isawumi; Sheriff, Agboola; Bimbo, Ayegoro

2016-03-01

Paediatric ophthalmology is an emerging subspecialty in Nigeria and as such there is paucity of data on refractive errors in the country. This study set out to determine the pattern of refractive errors in children attending an eye clinic in South West Nigeria. A descriptive study of 180 consecutive subjects seen over a 2-year period. Presenting complaints, presenting visual acuity (PVA), age and sex were recorded. Clinical examination of the anterior and posterior segments of the eyes, extraocular muscle assessment and refraction were done. The types of refractive errors and their grades were determined. Corrected VA was obtained. Data was analysed using descriptive statistics in proportions, chi square with p value <0.05. The age range of subjects was between 3 and 16 years with mean age = 11.7 and SD = 0.51; with males making up 33.9%.The commonest presenting complaint was blurring of distant vision (40%), presenting visual acuity 6/9 (33.9%), normal vision constituted >75.0%, visual impairment20% and low vision 23.3%. Low grade spherical and cylindrical errors occurred most frequently (35.6% and 59.9% respectively). Regular astigmatism was significantly more common, P <0.001. The commonest diagnosis was simple myopic astigmatism (41.1%). Four cases of strabismus were seen. Simple spherical and cylindrical errors were the commonest types of refractive errors seen. Visual impairment and low vision occurred and could be a cause of absenteeism from school. Low-cost spectacle production or dispensing unit and health education are advocated for the prevention of visual impairment in a hospital set-up.

Population density and refractive error among Chinese children.

PubMed

Zhang, Mingzhi; Li, Liping; Chen, Lizhen; Lee, Jack; Wu, Jiasi; Yang, Amy; Chen, Connie; Xu, Daocheng; Lam, Dennis S C; Sharma, Abhishek; Griffiths, Sian; Gao, Yang; Congdon, Nathan

2010-10-01

China is urbanizing rapidly, and the prevalence of myopia is high. This study was conducted to identify the reasons for observed differences in the prevalence of myopia among urban versus rural Chinese children. All children with uncorrected acuity of 6/12 or worse and a 50% random sample of children with vision better than 6/12 at all secondary schools in mixed rural-urban Liangying Township, Guangdong, underwent cycloplegic refraction, and provided data on age, gender, parental education, weekly near work and time outdoors, and urban development level of respondents' neighborhoods (12-item questionnaire). Population density of 32 villages and urban zones in Liangying was calculated from census figures (mean population density, 217 persons/km(2); range, 94-957; mean for Guangdong, 486). Among 5844 eligible children, 4612 (78.9%) had parental consent and completed examinations; 2957 were refracted per protocol, and 2480 (83.9%) of these had questionnaire data. Those with completed examinations were more likely to be girls (P < 0.001), and questionnaire respondents were more myopic (P = 0.02), but otherwise did not differ significantly from nonrespondents. In multivariate models, older age (P < 0.001), more near work (P = 0.02), and higher population density (P = 0.003), but not development index, parental education, or time outdoors were significantly associated with more myopic refractive error. Higher population density appears to be associated with myopia risk, independent of academic activity, time spent outdoors, familial educational level, or economic development, factors that have been thought to explain higher myopia prevalence among urban children. Mechanisms for this apparent association should be sought.

Time course of the effects of orthokeratology on peripheral refraction and corneal topography.

PubMed

Kang, Pauline; Swarbrick, Helen

2013-05-01

To describe the time course of changes in both peripheral refraction and corneal topography in myopic adults wearing myopic orthokeratology (OK) lenses. Nineteen adult myopes were fitted with OK lenses in both eyes for overnight wear. Central and peripheral refraction and corneal topography were measured along the horizontal meridian at baseline and after 1, 4, 7 and 14 nights of lens wear. At baseline, refraction was myopic at all positions along the horizontal meridian. Two weeks of OK lens wear caused a significant change in refraction where the general trend was a hyperopic shift in spherical equivalent (M) except at 35° in the nasal visual field where there was instead a myopic shift in M. The most significant change in M occurred between baseline and after 1 night of OK lens wear and the effect became less dramatic across subsequent days of OK treatment. Similarly, OK caused significant change in corneal refractive power at all positions along the horizontal corneal chord. There was a reduction in corneal power or flattening of the cornea at all positions except at 2.4 mm and 2.8 mm on the nasal cornea where there was an increase in corneal refractive power or steepening of the cornea. This change was most apparent after 1 night of OK lens wear and, similar to changes in peripheral refraction, changes in corneal refractive power on subsequent days of OK treatment became less marked. Orthokeratology caused significant changes in both peripheral refraction and corneal topography. The greatest change in refraction and corneal refractive power across the horizontal corneal meridian occurred during the first night of OK lens wear. Subsequent changes in both peripheral refraction and corneal topography were less dramatic, in the same manner as reported changes in apical radius and central refraction after OK. This study confirms that with OK treatment, the peripheral retina experiences myopic defocus, which is conjectured to underlie the observed slowing of myopia progression. Ophthalmic & Physiological Optics © 2013 The College of Optometrists.

Analysis of Macular and Retinal Nerve Fiber Layer Thickness in Children with Refractory Amblyopia after Femtosecond Laser-assisted Laser In situ Keratomileusis: A Retrospective Study

PubMed Central

Zhao, Peng-Fei; Zhou, Yue-Hua; Zhang, Jing; Wei, Wen-Bin

2017-01-01

Background: Localized macular edema and retinal nerve fiber layer (RNFL) thinning have been reported shortly after laser in situ keratomileusis (LASIK) in adults. However, it is still unclear how LASIK affects the retina of children. This study aimed to investigate the macular retina and RNFL thickness in children with refractive amblyopia who underwent femtosecond laser-assisted LASIK (FS-LASIK). Methods: In this study, we included 56 eyes of 32 patients with refractive amblyopia who underwent FS-LASIK in our hospital from January 2012 to December 2016. Foveal (foveal center retinal, parafoveal retinal, and perifoveal), macular inner retinal (superior and inferior), and peripapillary RNFL thicknesses (superior, inferior, temporal, and nasal) were measured using Fourier-domain optical coherence tomography before surgery and 1 day, 3 days, and 1 week after surgery. We divided these patients into three groups based on their refractive error: High myopic group with 22 eyes (equivalent sphere, >6.00 D), mild myopic group with 19 eyes (equivalent sphere, 0–6.00 D), and hyperopic group with 15 eyes (equivalent sphere, >+0.50 D). We compared the macular retina and RNFL thickness before and after LASIK. A paired simple t-test was used for data analysis. Results: One week after surgery, the visual acuity for all 56 eyes of the 32 patients reached their preoperative best-corrected vision. Visual acuity improved two lines or better for 31% of the patients. The residual refractive errors in 89% of the patients were within ±0.5 D. In the high myopic group, the foveal center retinal and parafoveal retinal thicknesses were thicker 1 day and 3 days after surgery than before surgery (t = 2.689, P = 0.012; t = 2.383, P = 0.018, respectively); no significant difference was found 1 week after surgery (P > 0.05). The foveal center retinal and parafoveal retinal thicknesses were greater 1 day after surgery than they were before surgery (P = 0.000 and P = 0.005, respectively) in the mild myopic and hyperopic groups. No significant difference was found 3 days or 1 week after surgery (P > 0.05). In all three groups, no significant difference was found in the macular inner retinal or peripapillary RNFL thickness 1 day, 3 days, or 1 week after surgery (P > 0.05). Conclusions: The foveal center retinal edema after FS-LASIK is mild and reversible in children, that mostly occurred in the high myopic group with no effect on the visual acuity, and is always relieved within 1 week. PMID:28875960

Through-focus optical characteristics of monofocal and bifocal soft contact lenses across the peripheral visual field.

PubMed

Ji, Qiuzhi; Yoo, Young-Sik; Alam, Hira; Yoon, Geunyoung

2018-05-01

To characterise the impact of monofocal soft contact lens (SCL) and bifocal SCLs on refractive error, depth of focus (DoF) and orientation of blur in the peripheral visual field. Monofocal and two bifocal SCLs, Acuvue Bifocal (AVB, Johnson & Johnson) and Misight Dual Focus (DF, CooperVision) with +2.0 D add power were modelled using a ray tracing program (ZEMAX) based on their power maps. These SCLs were placed onto the anterior corneal surface of the simulated Atchison myopic eye model to correct for -3.0 D spherical refractive error at the fovea. To quantify through-focus retinal image quality, defocus from -3.5 D to 1.5 D in 0.5 D steps was induced at each horizontal eccentricity from 0 to 40° in 10° steps. Wavefront aberrations were computed for each visual eccentricity and defocus. The retinal images were simulated using a custom software program developed in Matlab (The MathWorks) by convolving the point spread function calculated from the aberration with a reference image. The convolved images were spatially filtered to match the spatial resolution limit of each peripheral eccentricity. Retinal image quality was then quantified by the 2-D cross-correlation between the filtered convolved retinal images and the reference image. Peripheral defocus, DoF and orientation of blur were also estimated. In comparison with the monofocal SCL, the bifocal SCLs degraded retinal image quality while DoF was increased at fovea. From 10 to 20°, a relatively small amount of myopic shift (less than 0.3 D) was induced by bifocal SCLs compared with monofocal. DoF was also increased with bifocal SCLs at peripheral vision of 10 and 20°. The trend of myopic shift became less consistent at larger eccentricity, where at 30° DF showed a 0.75 D myopic shift while AVB showed a 0.2 D hyperopic shift and both AVB and DF exhibited large relative hyperopic defocus at 40°. The anisotropy in orientation of blur was found to increase and change its direction through focus beyond central vision. This trend was found to be less dominant with bifocal SCLs compared to monofocal SCL. Bifocal SCLs have a relatively small impact on myopic shift in peripheral refractive error while DoF is increased significantly. We hypothetically suggest that a mechanism underlying myopia control with these bifocal or multifocal contact lenses is an increase in DoF and a decrease in anisotropy of peripheral optical blur. © 2018 The Authors Ophthalmic & Physiological Optics © 2018 The College of Optometrists.

Myopia and depressive symptoms among older Chinese adults.

PubMed

Wu, Yin; Ma, Qinghua; Sun, Hong-Peng; Xu, Yong; Niu, Mei-E; Pan, Chen-Wei

2017-01-01

Few population-based data support the hypothesis that refractive errors are associated with depressive symptoms. We aim to assess the impact of myopia on the risk of having depressive symptoms in a community-based cohort of elderly Chinese. A community-based cross-sectional study of 4611 Chinese adults aged 60 years or older was conducted. Depressive symptoms were measured using the 9-item Patient Health Questionnaire (PHQ-9) depression scale in 4597 adults. Refraction was determined by auto-refraction followed by subjective refraction. Myopia was defined as spherical equivalent (SE) < -0.50 diopters (D) and high myopia as SE < -6.00 D. After adjusting for age, gender, education, lifestyle-related exposures, presenting visual acuity and age-related cataract, myopic adults were more likely to have any depressive symptoms compared with non-myopic ones (odds ratio = 1.39; 95% confidence interval 1.04, 1.92). There were no significant differences in the risk of having any depressive symptoms between those with and without high myopia. Myopia or high myopia was not associated with having moderate depressive symptoms. The impact of myopia on depressive symptoms was stronger in adults with no formal education compared with those with formal education. Myopia was related with the presence of depressive symptoms among older adults.

Differences between wavefront and subjective refraction for infrared light.

PubMed

Teel, Danielle F W; Jacobs, Robert J; Copland, James; Neal, Daniel R; Thibos, Larry N

2014-10-01

To determine the accuracy of objective wavefront refractions for predicting subjective refractions for monochromatic infrared light. Objective refractions were obtained with a commercial wavefront aberrometer (COAS, Wavefront Sciences). Subjective refractions were obtained for 30 subjects with a speckle optometer validated against objective Zernike wavefront refractions on a physical model eye (Teel et al., Design and validation of an infrared Badal optometer for laser speckle, Optom Vis Sci 2008;85:834-42). Both instruments used near-infrared (NIR) radiation (835 nm for COAS, 820 nm for the speckle optometer) to avoid correction for ocular chromatic aberration. A 3-mm artificial pupil was used to reduce complications attributed to higher-order ocular aberrations. For comparison with paraxial (Seidel) and minimum root-mean-square (Zernike) wavefront refractions, objective refractions were also determined for a battery of 29 image quality metrics by computing the correcting lens that optimizes retinal image quality. Objective Zernike refractions were more myopic than subjective refractions for 29 of 30 subjects. The population mean discrepancy was -0.26 diopters (D) (SEM = 0.03 D). Paraxial (Seidel) objective refractions tended to be hyperopically biased (mean discrepancy = +0.20 D, SEM = 0.06 D). Refractions based on retinal image quality were myopically biased for 28 of 29 metrics. The mean bias across all 31 measures was -0.24 D (SEM = 0.03). Myopic bias of objective refractions was greater for eyes with brown irises compared with eyes with blue irises. Our experimental results are consistent with the hypothesis that reflected NIR light captured by the aberrometer originates from scattering sources located posterior to the entrance apertures of cone photoreceptors, near the retinal pigment epithelium. The larger myopic bias for brown eyes suggests that a greater fraction of NIR light is reflected from choroidal melanin in brown eyes compared with blue eyes.

The Refractive Error of Professional Baseball Players.

PubMed

Laby, Daniel M; Kirschen, David G

2017-05-01

High levels of visual acuity are required to hit a baseball effectively. Research has shown that any decrease in vision is likely caused by low-order optical aberrations. This study is designed to validate the SVOne autorefractor, and describe the amount and type, of low-order optical aberrations present in a large cohort of professional baseball players. A retrospective chart review on the 608 Major League Baseball players evaluated during the 2016 Spring Training Season was performed. Results for a subset of players who had both manifest refraction as well as autorefraction were calculated. Subsequently, after determining the accuracy of the autorefraction system in this population, refractive results for the entire population were determined. There was a borderline statistically significant difference in mean spherical refractive error (M) between the manifest refraction and the SVOne auto refraction (-0.273D in the manifest refraction method vs. -0.503D in the SVOne method, P = .06) in the subset of athletes who underwent both tests. Additionally, there was no difference in the J0 or J45 cylindrical component vectors for each method. For the entire eligible population, the SVOne autorefraction system found a mean spherical refractive error (M) of -0.228D, a J0 value of -0.013D, and a J45 value of -0.040D. These data suggest that the SVOne autorefraction system is generally able to measure the refractive error in the baseball population. The system was slightly biased, often reporting more myopia in myopic subjects. Thus, careful evaluation of the refractive status of these athletes coupled with careful subjective refractive correction for those with less than average vision for baseball is strongly suggested.

Combining primary and piggyback intraocular lenses to treat extreme myopic astigmatism in stable keratoconus following cataract surgery.

PubMed

Goh, Yi Wei; Misra, Stuti; Patel, Dipika V; McGhee, Charles N J

2013-03-01

The majority of those with keratoconus can maximise visual acuity with spectacle or contact lens correction as they age; however, as subjects enter their sixties, cataracts may supervene and contact lens tolerance diminishes with consequent reduction in visual acuity. Following cataract extraction, the complex refractive error associated with keratoconus may not be readily corrected by an intraocular lens alone. This report highlights the planned implantation of a primary posterior chamber toric intraocular lens with a secondary piggyback, sulcus-based, intraocular lens in advanced but stable keratoconus with extreme myopic astigmatism and cataract. © 2013 The Authors. Clinical and Experimental Optometry © 2013 Optometrists Association Australia.

Total ocular, anterior corneal and lenticular higher order aberrations in hyperopic, myopic and emmetropic eyes.

PubMed

Philip, Krupa; Martinez, Aldo; Ho, Arthur; Conrad, Fabian; Ale, Jit; Mitchell, Paul; Sankaridurg, Padmaja

2012-01-01

Total ocular higher order aberrations and corneal topography of myopic, emmetropic and hyperopic eyes of 675 adolescents (16.9 ± 0.7 years) were measured after cycloplegia using COAS aberrometer and Medmont videokeratoscope. Corneal higher order aberrations were computed from the corneal topography maps and lenticular (internal) higher order aberrations derived by subtraction of corneal aberrations from total ocular aberrations. Aberrations were measured for a pupil diameter of 5mm. Multivariate analysis of variance followed by multiple regression analysis found significant difference in the fourth order aberrations (SA RMS, primary spherical aberration coefficient) between the refractive error groups. Hyperopic eyes (+0.083 ± 0.05 μm) had more positive total ocular primary spherical aberration compared to emmetropic (+0.036 ± 0.04 μm) and myopic eyes (low myopia=+0.038 ± 0.05 μm, moderate myopia=+0.026 ± 0.06 μm) (p<0.05). No difference was observed for the anterior corneal spherical aberration. Significantly less negative lenticular spherical aberration was observed for the hyperopic eyes (-0.038 ± 0.05 μm) than myopic (low myopia=-0.088 ± 0.04 μm, moderate myopia=-0.095 ± 0.05 μm) and emmetropic eyes (-0.081 ± 0.04 μm) (p<0.05). These findings suggest the existence of differences in the characteristics of the crystalline lens (asphericity, curvature and gradient refractive index) of hyperopic eyes versus other eyes. Crown Copyright © 2011. Published by Elsevier Ltd. All rights reserved.

Vision and academic performance of learning disabled children.

PubMed

Wharry, R E; Kirkpatrick, S W

1986-02-01

The purpose of this study was to assess difference in academic performance among myopic, hyperopic, and emmetropic children who were learning disabled. More specifically, myopic children were expected to perform better on mathematical and spatial tasks than would hyperopic ones and that hyperopic and emmetropic children would perform better on verbal measures than would myopic ones. For 439 learning disabled students visual anomalies were determined via a Generated Retinal Reflex Image Screening System. Test data were obtained from school files. Partial support for the hypothesis was obtained. Myopic learning disabled children outperformed hyperopic and emmetropic children on the Key Math test. Myopic children scored better than hyperopic children on the WRAT Reading subtest and on the Durrell Analysis of Reading Difficulty Oral Reading Comprehension, Oral Rate, Flashword, and Spelling subtests, and on the Key Math Measurement and Total Scores. Severity of refractive error significantly affected the Wechsler Intelligence Scale for Children--Revised Full Scale, Performance Scale, Verbal Scale, and Digit Span scores but did not affect any academic test scores. Several other findings were also reported. Those with nonametropic problems scored higher than those without problems on the Key Math Time subtest. Implications supportive of the theories of Benbow and Benbow and Geschwind and Behan were stated.

Peripheral myopization and visual performance with experimental rigid gas permeable and soft contact lens design.

PubMed

Pauné, J; Queiros, A; Quevedo, L; Neves, H; Lopes-Ferreira, D; González-Méijome, J M

2014-12-01

To evaluate the performance of two experimental contact lenses (CL) designed to induce relative peripheral myopic defocus in myopic eyes. Ten right eyes of 10 subjects were fitted with three different CL: a soft experimental lens (ExpSCL), a rigid gas permeable experimental lens (ExpRGP) and a standard RGP lens made of the same material (StdRGP). Central and peripheral refraction was measured using a Grand Seiko open-field autorefractometer across the central 60° of the horizontal visual field. Ocular aberrations were measured with a Hartman-Shack aberrometer, and monocular contrast sensitivity function (CSF) was measured with a VCTS6500 without and with the three contact lenses. Both experimental lenses were able to increase significantly the relative peripheral myopic defocus up to -0.50 D in the nasal field and -1.00 D in the temporal field (p<0.05). The ExpRGP induced a significantly higher myopic defocus in the temporal field compared to the ExpSCL. ExpSCL induced significantly lower levels of Spherical-like HOA than ExpRGP for the 5mm pupil size (p<0.05). Both experimental lenses kept CSF within normal limits without any statistically significant change from baseline (p>0.05). RGP lens design seems to be more effective to induce a significant myopic change in the relative peripheral refractive error. Both lenses preserve a good visual performance. The worsened optical quality observed in ExpRGP was due to an increased coma-like and spherical-like HOA. However, no impact on the visual quality as measured by CSF was observed. Copyright © 2014 British Contact Lens Association. Published by Elsevier Ltd. All rights reserved.

Ocular residual astigmatism's effect on high myopic astigmatism LASIK surgery

PubMed Central

Teus, M A; Arruabarrena, C; Hernández-Verdejo, J L; Cañones, R; Mikropoulos, D G

2014-01-01

Purpose To analyze the effect of ocular residual astigmatism (ORA) on the effectiveness of LASIK for treating high myopic astigmatism. Methods This is an observational, cross-sectional study. We studied 116 consecutive myopic eyes with −3 diopters (D) or more of astigmatism that underwent LASIK surgery. The magnitude of uncorrected residual refractive astigmatism 3 months postoperatively was measured. Results The mean preoperative cylinder was −4.0±0.83 D (range, −7.5 to −3 D) and the mean preoperative ORA was 0.82±0.5 D. The mean residual refractive cylinder 3 months postoperatively was −0.78±0.83 D (range, −3 to 0 D). No correlation was found between ORA and the refractive cylinder 3 months postoperatively (P=0.6). Conclusion In eyes with high myopic astigmatism undergoing LASIK, ORA was not correlated with the residual postoperative cylinder. PMID:24971989

Comparison of Subjective Refraction under Binocular and Monocular Conditions in Myopic Subjects.

PubMed

Kobashi, Hidenaga; Kamiya, Kazutaka; Handa, Tomoya; Ando, Wakako; Kawamorita, Takushi; Igarashi, Akihito; Shimizu, Kimiya

2015-07-28

To compare subjective refraction under binocular and monocular conditions, and to investigate the clinical factors affecting the difference in spherical refraction between the two conditions. We examined thirty eyes of 30 healthy subjects. Binocular and monocular refraction without cycloplegia was measured through circular polarizing lenses in both eyes, using the Landolt-C chart of the 3D visual function trainer-ORTe. Stepwise multiple regression analysis was used to assess the relations among several pairs of variables and the difference in spherical refraction in binocular and monocular conditions. Subjective spherical refraction in the monocular condition was significantly more myopic than that in the binocular condition (p < 0.001), whereas no significant differences were seen in subjective cylindrical refraction (p = 0.99). The explanatory variable relevant to the difference in spherical refraction between binocular and monocular conditions was the binocular spherical refraction (p = 0.032, partial regression coefficient B = 0.029) (adjusted R(2) = 0.230). No significant correlation was seen with other clinical factors. Subjective spherical refraction in the monocular condition was significantly more myopic than that in the binocular condition. Eyes with higher degrees of myopia are more predisposed to show the large difference in spherical refraction between these two conditions.

Comparison of Subjective Refraction under Binocular and Monocular Conditions in Myopic Subjects

PubMed Central

Kobashi, Hidenaga; Kamiya, Kazutaka; Handa, Tomoya; Ando, Wakako; Kawamorita, Takushi; Igarashi, Akihito; Shimizu, Kimiya

2015-01-01

To compare subjective refraction under binocular and monocular conditions, and to investigate the clinical factors affecting the difference in spherical refraction between the two conditions. We examined thirty eyes of 30 healthy subjects. Binocular and monocular refraction without cycloplegia was measured through circular polarizing lenses in both eyes, using the Landolt-C chart of the 3D visual function trainer-ORTe. Stepwise multiple regression analysis was used to assess the relations among several pairs of variables and the difference in spherical refraction in binocular and monocular conditions. Subjective spherical refraction in the monocular condition was significantly more myopic than that in the binocular condition (p < 0.001), whereas no significant differences were seen in subjective cylindrical refraction (p = 0.99). The explanatory variable relevant to the difference in spherical refraction between binocular and monocular conditions was the binocular spherical refraction (p = 0.032, partial regression coefficient B = 0.029) (adjusted R2 = 0.230). No significant correlation was seen with other clinical factors. Subjective spherical refraction in the monocular condition was significantly more myopic than that in the binocular condition. Eyes with higher degrees of myopia are more predisposed to show the large difference in spherical refraction between these two conditions. PMID:26218972

Impact of Primary Spherical Aberration, Spatial Frequency and Stiles Crawford Apodization on Wavefront determined Refractive Error: A Computational Study

PubMed Central

Xu, Renfeng; Bradley, Arthur; Thibos, Larry N.

2013-01-01

Purpose We tested the hypothesis that pupil apodization is the basis for central pupil bias of spherical refractions in eyes with spherical aberration. Methods We employed Fourier computational optics in which we vary spherical aberration levels, pupil size, and pupil apodization (Stiles Crawford Effect) within the pupil function, from which point spread functions and optical transfer functions were computed. Through-focus analysis determined the refractive correction that optimized retinal image quality. Results For a large pupil (7 mm), as spherical aberration levels increase, refractions that optimize the visual Strehl ratio mirror refractions that maximize high spatial frequency modulation in the image and both focus a near paraxial region of the pupil. These refractions are not affected by Stiles Crawford Effect apodization. Refractions that optimize low spatial frequency modulation come close to minimizing wavefront RMS, and vary with level of spherical aberration and Stiles Crawford Effect. In the presence of significant levels of spherical aberration (e.g. C40 = 0.4 µm, 7mm pupil), low spatial frequency refractions can induce −0.7D myopic shift compared to high SF refraction, and refractions that maximize image contrast of a 3 cycle per degree square-wave grating can cause −0.75D myopic drift relative to refractions that maximize image sharpness. Discussion Because of small depth of focus associated with high spatial frequency stimuli, the large change in dioptric power across the pupil caused by spherical aberration limits the effective aperture contributing to the image of high spatial frequencies. Thus, when imaging high spatial frequencies, spherical aberration effectively induces an annular aperture defining that portion of the pupil contributing to a well-focused image. As spherical focus is manipulated during the refraction procedure, the dimensions of the annular aperture change. Image quality is maximized when the inner radius of the induced annulus falls to zero, thus defining a circular near paraxial region of the pupil that determines refraction outcome. PMID:23683093

Disruption of emmetropization and high susceptibility to deprivation myopia in albino guinea pigs.

PubMed

Jiang, Liqin; Long, Keli; Schaeffel, Frank; Zhang, Sen; Zhou, Xiangtian; Lu, Fan; Qu, Jia

2011-08-03

To compare emmetropization in albino and pigmented guinea pigs. Distributions of refractive state were examined in 214 albino and 234 pigmented guinea pigs. Albino (A) and pigmented (P) guinea pigs were divided into two groups, hyperopic (H) and myopic (M). Eye development was separately followed in 10 randomly selected animals from each group (AH, AM, PH, PM) from 2 to 10 weeks of age. In addition, deprivation myopia was induced in 36 age-matched albino (18 AH and 18 AM) and 36 pigmented (18 PH and 18 PM) guinea pigs by diffusers that were worn from 2 to 6 weeks of age. Finally, sclera fibril diameters were measured using transmission electron microscopy. Strikingly, the distributions of refractive errors were bimodal at 2 weeks of age, both in albino and pigmented animals, with clearly different averages (-2.86 ± 5.60 diopters [D] vs. 2.13 ± 5.27 D respectively; t = 9.712; P < 0.001). Spontaneous myopia was more common in albino animals: 70.1% were myopic (AM) and 29.9% hyperopic (AH), whereas only 28.6% were myopic (PM) and 71.4% hyperopic (PH) in pigmented guinea pigs. Different from PM and AM did not show any recovery from myopia. With diffusers, AH became more myopic (-7.61 ± 2.71 D and -11.17 ± 2.55 D) than PH (-4.48 ± 1.46 D and -8.28 ± 2.13 D) after 2 and 4 weeks, respectively. Deprivation myopia could still be induced in PM (-1.64 ± 1.44 D and -5.17 ± 1.88 D after 2 and 4 weeks, respectively; P < 0.01) but not in AM. Scleral fibril diameters were smaller in myopic animals, both albino and pigmented. Deprivation myopia could not be induced in spontaneously myopic but only in hyperopic albino guinea pigs, where it was even higher than in pigmented animals. The distinct effects of albinism on emmetropization will help to elucidate the mechanisms underlying the emmetropization.

Posterior corneal surface differences between non-laser in situ keratomileusis (LASIK) and 10-year post-LASIK myopic eyes.

PubMed

Dai, Ma-Li; Wang, Qin-Mei; Lin, Zu-Shun; Yu, Ye; Huang, Jin-Hai; Savini, Giacomo; Zhang, Jia; Wang, Ling; Xu, Chen-Chen

2018-03-01

To evaluate the posterior corneal surface differences between non-laser in situ keratomileusis (LASIK) and 10-year post-LASIK myopic eyes. The study included 130 eyes from 65 patients, who were treated with myopic LASIK 10 years ago. In addition, 130 eyes from 65 unoperated myopic patients of matching present age and preoperative refraction were divided into control group. Data on the posterior corneal surface and anterior chamber were obtained from Pentacam software and compared between the groups. Postoperative visual acuity (VA) and refractive error were also analysed. The mean preoperative spherical equivalent (SE) was -6.99 ± 1.78 dioptre (D) in the LASIK group. Ten years after surgery, the mean SE was -0.45 ± 1.22 D, the efficacy index was 0.98, and the safety index was 1.01. The posterior corneal elevations of the LASIK group at 2 mm corneal diameter were significantly lower than those of the control group. However, posterior corneal elevations at 6 mm corneal diameter were higher in the LASIK group than the controls (p < 0.01 for all). The mean Q-values of posterior corneal surface demonstrated significant positive direction compared to that of control eyes at 6 and 7 mm corneal diameters (p < 0.05 for both). At the thinnest point of the cornea, the anterior chamber depths were shallower in the LASIK group than in controls. Meanwhile, the anterior chamber volumes (ACV) were smaller in the LASIK group than in the control group. Our results demonstrated that the posterior corneal surface tends to show signs of central flattening and peripheral steepening 10 years after myopic LASIK surgery compared to that of non-operated myopic eyes. © 2017 Acta Ophthalmologica Scandinavica Foundation. Published by John Wiley & Sons Ltd.

Outcomes of photorefractive keratectomy enhancement after LASIK.

PubMed

Lee, Bryan S; Gupta, Preeya K; Davis, Elizabeth A; Hardten, David R

2014-08-01

To report the outcomes of photorefractive keratectomy (PRK) enhancement after LASIK for patients diagnosed as having hyperopic and myopic refractive errors. In this retrospective case series at a single private practice in the United States, all patients undergoing PRK enhancement after LASIK were identified. Patients with visually significant cataract, non-plano targets, and follow-up of fewer than 226 days were excluded. The primary outcome measure was uncorrected distance visual acuity (UDVA) with secondary measures of corrected distance visual acuity (CDVA) and postoperative refractive error. Linear regression analysis was performed for actual versus targeted change in spherical equivalent. Mean UDVA improved from 20/39 to 20/24 for hyperopes (n = 14; P < .002) and from 20/45 to 20/22 for myopes (n = 29; P < .0000001) after enhancement. All patients had a UDVA of 20/40 or better at their most recent follow-up visit. Fifty percent of hyperopes and 65.5% of myopes were 20/20 or better. The mean refractive error for hyperopes changed from +1.10 ± 0.71 (range: +0.13 to +2.25 diopters [D]) to +0.38 ± 0.66 D (range: -0.75 to +1.38 D) and from -1.21 ± 0.61 (range: -3.25 to -0.38 D) to +0.34 ± 0.45 D (range: -0.25 to +1.75 D) for myopes. The manifest refraction cylinder decreased from 0.84 to 0.46 D in hyperopes (P = .02) and from 0.64 to 0.26 D in myopes (P < .002). CDVA was maintained in both groups, with only one patient in each worse than 20/20. There was a nonsignificant trend toward less haze in the patients receiving mitomycin C (5.1% vs 25%, P = .14). Linear regression showed a tendency toward overtreatment in the myopic group. PRK is safe and highly effective for patients who previously underwent LASIK and in whom the surgeon would prefer not to perform a flap-lift enhancement. Copyright 2014, SLACK Incorporated.

Variant myopia: A new presentation?

PubMed Central

Hussaindeen, Jameel Rizwana; Anand, Mithra; Sivaraman, Viswanathan; Ramani, Krishna Kumar; Allen, Peter M

2018-01-01

Purpose: Variant myopia (VM) presents as a discrepancy of >1 diopter (D) between subjective and objective refraction, without the presence of any accommodative dysfunction. The purpose of this study is to create a clinical profile of VM. Methods: Fourteen eyes of 12 VM patients who had a discrepancy of >1D between retinoscopy and subjective acceptance under both cycloplegic and noncycloplegic conditions were included in the study. Fourteen eyes of 14 age- and refractive error-matched participants served as controls. Potential participants underwent a comprehensive orthoptic examination followed by retinoscopy (Ret), closed-field autorefractor (CA), subjective acceptance (SA), choroidal and retinal thickness, ocular biometry, and higher order spherical aberrations measurements. Results: In the VM eyes, a statistically and clinically significant difference was noted between the Ret and CA and Ret and SA under both cycloplegic and noncycloplegic conditions (multivariate repeated measures analysis of variance, P < 0.0001). A statistically significant difference was observed between the VM eyes, non-VM eyes, and controls for choroidal thickness in all the quadrants (Univariate ANOVA P < 0.05). The VM eyes had thinner choroids (197.21 ± 13.04 μ) compared to the non-VM eyes (249.25 ± 53.70 μ) and refractive error-matched controls (264.62 ± 12.53 μ). No statistically significant differences between groups in root mean square of total higher order aberrations and spherical aberration were observed. Conclusion: Accommodative etiology does not play a role in the refractive discrepancy seen in individuals with the variant myopic presentation. These individuals have thinner choroids in the eye with variant myopic presentation compared to the fellow eyes and controls. Hypotheses and clinical implications of variant myopia are discussed. PMID:29785987

Ciliary Body Thickness and Refractive Error in Children

PubMed Central

Bailey, Melissa D.; Sinnott, Loraine T.; Mutti, Donald O.

2010-01-01

Purpose To determine whether ciliary body thickness (CBT) is related to refractive error in school-age children. Methods Fifty-three children, 8 to 15 years of age, were recruited. CBT was measured from anterior segment OCT images (Visante; Carl Zeiss Meditec, Inc., Dublin, CA) at 1 (CBT1), 2 (CBT2) and 3 (CBT3) mm posterior to the scleral spur. Cycloplegic refractive error was measured with an autorefractor, and axial length was measured with an optical biometer. Multilevel regression models determined the relationship between CBT measurements and refractive error or axial length. A Bland-Altman analysis was used to assess the between-visit repeatability of the ciliary body measurements. Results The between-visits coefficients of repeatability for CBT1, -2, and -3 were 148.04, 165.68, and 110.90, respectively. Thicker measurements at CBT2 (r = −0.29, P = 0.03) and CBT3 (r = −0.38, P = 0.005) were associated with increasingly myopic refractive errors (multilevel model: P < 0.001). Thicker measurements at CBT2 (r = 0.40, P = 0.003) and CBT3 (r = 0.51, P < 0.001) were associated with longer axial lengths (multilevel model: P < 0.001). Conclusions Thicker ciliary body measurements were associated with myopia and a longer axial length. Future studies should determine whether this relationship is also present in animal models of myopia and determine the temporal relationship between thickening of the ciliary muscle and the onset of myopia. PMID:18566470

Crystalline lens and refractive development.

PubMed

Iribarren, Rafael

2015-07-01

Individual refractive errors usually change along lifespan. Most children are hyperopic in early life. This hyperopia is usually lost during growth years, leading to emmetropia in adults, but myopia also develops in children during school years or during early adult life. Those subjects who remain emmetropic are prone to have hyperopic shifts in middle life. And even later, at older ages, myopic shifts are developed with nuclear cataract. The eye grows from 15 mm in premature newborns to approximately 24 mm in early adult years, but, in most cases, refractions are maintained stable in a clustered distribution. This growth in axial length would represent a refractive change of more than 40 diopters, which is compensated by changes in corneal and lens powers. The process which maintains the balance between the ocular components of refraction during growth is still under study. As the lens power cannot be measured in vivo, but can only be calculated based on the other ocular components, there have not been many studies of lens power in humans. Yet, recent studies have confirmed that the lens loses power during growth in children, and that hyperopic and myopic shifts in adulthood may be also produced by changes in the lens. These studies in children and adults give a picture of the changing power of the lens along lifespan. Other recent studies about the growth of the lens and the complexity of its internal structure give clues about how these changes in lens power are produced along life. Copyright © 2015 Elsevier Ltd. All rights reserved.

Astigmatism in Chinese primary school children: prevalence, change, and effect on myopic shift.

PubMed

Chan, Shao-En; Kuo, Hsi-Kung; Tsai, Chia-Ling; Wu, Pei-Chang

2018-05-01

To study the prevalence, type, and progression of astigmatism in primary school children, and its effect on myopic shift. A prospective study carried out in a primary school in southern Taiwan. The study was performed on a subset of children, one year after initial examination. Refractive error measured by cycloplegic autorefraction was the main study outcome. Astigmatism was recorded as negative cylinder form, and we defined clinical significant astigmatism (CSA) as cylinder refraction -1.0 D or greater. Myopia was defined as a spherical equivalent refraction (SER) of -0.50 D or greater. Three hundred sixty-two children, mean age was 8.97 y/o (SD 1.41; range 7 to 11 y/o) participated in the study. One hundred nineteen (32.9 %) subjects had CSA at the initial screening. The mean cylinder refraction was -0.80 + 0.84 diopters (D) (-5.25 D to 0.00 D), with predominant with rule astigmatism (69.7%). In the 183 children studied longitudinally, the mean cylinder refraction was reduced from -0.74 D to -0.58 D (p< 0.05). The cylinder refraction in the initial CSA group was not associated with SER change (p=0.99) or axial length change (p=0.55). Compared to the initial non-CSA group, the initial CSA group had no significant difference in axial length elongation (p=0.20). The prevalence of astigmatism was not low in the Chinese primary school children and with-the-rule astigmatism was predominant. The astigmatism decreased during the 1 year follow-up. The CSA was not associated with myopia progression (p=0.99).

Computerized Scheimpflug densitometry as a measure of corneal optical density after excimer laser refractive surgery in myopic eyes.

PubMed

Cennamo, Gilda; Forte, Raimondo; Aufiero, Bernardino; La Rana, Agostino

2011-08-01

To evaluate changes in anterior corneal optical density and the refractive index after photorefractive keratectomy (PRK) using a rotating Scheimpflug system. Department of Ophthalmology, University Federico II, Naples, Italy. Comparative case series. Anterior corneal optical density was evaluated with a rotating Scheimpflug system at baseline and 3 months and 12 months after PRK in eyes with a refractive error between -6.00 diopters (D) and -12.00 D (study group). A control group of unoperated eyes with the same refraction range was used to calculate corneal optical density and the Gladstone-Dale constant in unoperated eyes using the Gladstone-Dale formula. In the study group, changes in the anterior corneal optical density were evaluated over time and variations in the anterior corneal refractive index were obtained using the Gladstone-Dale constant. The study group comprised 37 eyes and the control group, 200 eyes. In the study group, the mean anterior corneal optical density and refractive index, respectively, were 27.71 ± 4.39 and 1.360 ± 0.05 at baseline, 37.812 ± 12.31 and 1.491 ± 0.16 after 3 months (P<.001 compared with baseline), and 26.29 ± 4.93 and 1.341 ± 0.06 after 12 months (P=.03 compared with baseline). The mean corneal optical density in the control group was 27.71 ± 4.31 (SD), and the resultant Gladstone-Dale constant was 0.013. An early increase and a subsequent reduction in anterior corneal optical density and the refractive index were present in myopic eyes during 1 year after PRK. Copyright © 2011 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.

Prevalence of refractive error among preschool children in an urban population: the Baltimore Pediatric Eye Disease Study.

PubMed

Giordano, Lydia; Friedman, David S; Repka, Michael X; Katz, Joanne; Ibironke, Josephine; Hawes, Patricia; Tielsch, James M

2009-04-01

To determine the age-specific prevalence of refractive errors in white and African-American preschool children. The Baltimore Pediatric Eye Disease Study is a population-based evaluation of the prevalence of ocular disorders in children aged 6 to 71 months in Baltimore, Maryland. Among 4132 children identified, 3990 eligible children (97%) were enrolled and 2546 children (62%) were examined. Cycloplegic autorefraction was attempted in all children with the use of a Nikon Retinomax K-Plus 2 (Nikon Corporation, Tokyo, Japan). If a reliable autorefraction could not be obtained after 3 attempts, cycloplegic streak retinoscopy was performed. Mean spherical equivalent (SE) refractive error, astigmatism, and prevalence of higher refractive errors among African-American and white children. The mean SE of right eyes was +1.49 diopters (D) (standard deviation [SD] = 1.23) in white children and +0.71 D (SD = 1.35) in African-American children (mean difference of 0.78 D; 95% confidence interval [CI], 0.67-0.89). Mean SE refractive error did not decline with age in either group. The prevalence of myopia of 1.00 D or more in the eye with the lesser refractive error was 0.7% in white children and 5.5% in African-American children (relative risk [RR], 8.01; 95% CI, 3.70-17.35). The prevalence of hyperopia of +3 D or more in the eye with the lesser refractive error was 8.9% in white children and 4.4% in African-American children (RR, 0.49; 95% CI, 0.35-0.68). The prevalence of emmetropia (<-1.00 D to <+1.00 D) was 35.6% in white children and 58.0% in African-American children (RR, 1.64; 95% CI, 1.49-1.80). On the basis of published prescribing guidelines, 5.1% of the children would have benefited from spectacle correction. However, only 1.3% had been prescribed correction. Significant refractive errors are uncommon in this population of urban preschool children. There was no evidence for a myopic shift over this age range in this cross-sectional study. A small proportion of preschool children would likely benefit from refractive correction, but few have had this prescribed.

Myopia progression control lens reverses induced myopia in chicks.

PubMed

Irving, Elizabeth L; Yakobchuk-Stanger, Cristina

2017-09-01

To determine whether lens induced myopia in chicks can be reversed or reduced by wearing myopia progression control lenses of the same nominal (central) power but different peripheral designs. Newly hatched chicks wore -10D Conventional lenses unilaterally for 7 days. The myopic chicks were then randomly divided into three groups: one fitted with Type 1 myopia progression control lenses, the second with Type 2 myopia progression control lenses and the third continued to wear Conventional lenses for seven more days. All lenses had -10D central power, but Type 1 and Type 2 lenses had differing peripheral designs; +2.75D and +1.32D power rise at pupil edge, respectively. Axial length and refractive error were measured on Days 0, 7 and 14. Analyses were performed on the mean differences between treated and untreated eyes. Refractive error and axial length differences between treated and untreated eyes were insignificant on Day 0. On Day 7 treated eyes were longer (T1; 0.44 ± 0.07 mm, T2; 0.27 ± 0.06 mm, C; 0.40 ± 0.06 mm) and more myopic (T1; -9.61 ± 0.52D, T2; -9.57 ± 0.61D, C; -9.50 ± 0.58D) than untreated eyes with no significant differences between treatment groups. On Day 14 myopia was reversed (+2.91 ± 1.08D), reduced (-3.83 ± 0.94D) or insignificantly increased (-11.89 ± 0.79D) in treated eyes of Type 1, Type 2 and Conventional treated chicks respectively. Relative changes in axial lengths (T1; -0.13 ± 0.09 mm, T2; 0.36 ± 0.09 mm, C; 0.56 ± 0.05 mm) were consistent with changes in refraction. Refractive error differences were significant for all group comparisons (p < 0.001). Type 1 length differences were significantly different from Conventional and Type 2 groups (p < 0.001). Myopia progression control lens designs can reverse lens-induced myopia in chicks. The effect is primarily due to axial length changes. Different lens designs produce different effects indicating that lens design is important in modifying refractive error. © 2017 The Authors. Ophthalmic and Physiological Optics published by John Wiley & Sons Ltd on behalf of College of Optometrists.

Comparison of newer IOL power calculation methods for post-corneal refractive surgery eyes

PubMed Central

Wang, Li; Tang, Maolong; Huang, David; Weikert, Mitchell P.; Koch, Douglas D.

2015-01-01

Objective To compare the newer formulae, the optical coherence tomography based intraocular lens (IOL) power formula (OCT formula) and the Barrett True-K formula (True-K), to the methods on the ASCRS calculator in eyes with previous myopic LASIK/PRK. Design Prospective case series. Participants One-hundred and four eyes of 80 patients who had previous myopic LASIK/PRK and subsequent cataract surgery and IOL implantation. Methods Using the actual refraction following cataract surgery as target refraction, predicted IOL power for each method was calculated. The IOL prediction error (PE) was obtained by subtracting the predicted IOL power from the power of IOL implanted. Main outcome measures Arithmetic IOL PEs, variances of mean arithmetic IOL PE, median refractive PE and percent of eyes within 0.5 D and 1.0 D of refractive PE. Results OCT produced smaller variance of IOL PE than did Wang-Koch-Maloney, and Shammas (P<0.05). With the OCT, True-K No History, Wang-Koch-Maloney, Shammas, Haigis-L, and Average of these 5 formulas, respectively, the median refractive PEs were 0.35 D, 0.42 D, 0.51 D, 0.48 D, 0.39 D, and 0.35 D, and the % of eyes within 0.5 D of refractive PE were 68.3%, 58.7%, 50.0%, 52.9%, 55.8%, and 67.3%, and within 1.0 D of RPE, 92.3%, 90.4%, 86.9%, 88.5%, 90.4%, and 94.2%, respectively. The OCT formula had smaller refractive PE compared to Wang-Koch-Maloney and Shammas, and the Average approach produced significantly smaller refractive PE than did all methods except OCT (all P<0.05). Conclusions The OCT and True-K No History are promising formulas. The ASCRS IOL calculator has been updated to include the OCT and Barrett True K formulas. Trial registration Intraocular Lens Power Calculation After Laser Refractive Surgery Based on Optical Coherence Tomography (OCT IOL); Identifier: NCT00532051; www.ClinicalTrials.gov PMID:26459996

Bidirectional Expression of Metabolic, Structural, and Immune Pathways in Early Myopia and Hyperopia

PubMed Central

Riddell, Nina; Giummarra, Loretta; Hall, Nathan E.; Crewther, Sheila G.

2016-01-01

Myopia (short-sightedness) affects 1.45 billion people worldwide, many of whom will develop sight-threatening secondary disorders. Myopic eyes are characterized by excessive size while hyperopic (long-sighted) eyes are typically small. The biological and genetic mechanisms underpinning the retina's local control of these growth patterns remain unclear. In the present study, we used RNA sequencing to examine gene expression in the retina/RPE/choroid across 3 days of optically-induced myopia and hyperopia induction in chick. Data were analyzed for differential expression of single genes, and Gene Set Enrichment Analysis (GSEA) was used to identify gene sets correlated with ocular axial length and refraction across lens groups. Like previous studies, we found few single genes that were differentially-expressed in a sign-of-defocus dependent manner (only BMP2 at 1 day). Using GSEA, however, we are the first to show that more subtle shifts in structural, metabolic, and immune pathway expression are correlated with the eye size and refractive changes induced by lens defocus. Our findings link gene expression with the morphological characteristics of refractive error, and suggest that physiological stress arising from metabolic and inflammatory pathway activation could increase the vulnerability of myopic eyes to secondary pathologies. PMID:27625591

Accuracy of refractive outcomes in myopic and hyperopic laser in situ keratomileusis: Manifest versus aberrometric refraction.

PubMed

Reinstein, Dan Z; Morral, Merce; Gobbe, Marine; Archer, Timothy J

2012-11-01

To compare the achieved refractive accuracy of laser in situ keratomileusis (LASIK) performed based on manifest refraction with the predicted accuracy that would have been achieved using WASCA aberrometric refraction with and without Seidel correction factor for sphere. London Vision Clinic, London, United Kingdom. Comparative case series. Myopic eyes and hyperopic eyes had LASIK based on manifest refraction. Two aberrometric refractions were obtained preoperatively: Seidel, which includes spherical aberration in the sphere calculation, and non-Seidel. Bland-Altman plots were used to show the agreement between aberrometric and manifest refractions. Predicted LASIK outcomes had aberrometric refraction been used were modeled by shifting the postoperative manifest refraction by the vector difference between the preoperative manifest and aberrometric refractions. This study included 869 myopic eyes and 413 hyperopic eyes. The mean differences (manifest minus aberrometric) in spherical equivalent were +0.03 diopters (D) ± 0.48 (SD) (Seidel aberrometric) and +0.45 ± 0.42 D (non-Seidel aberrometric) for myopia and -0.20 ± 0.39 D and +0.39 ± 0.34 D, respectively, for hyperopia. The mean differences in cylinder magnitude were -0.10 ± 0.27 D and 0.00 ± 0.25 D, respectively. The percentage of eyes within ±0.50 D of the attempted correction was 81% (manifest), 70% (Seidel), and 67% (non-Seidel) for myopia and 71% (manifest), 61% (Seidel), and 64% (non-Seidel) for hyperopia. The achieved refractive accuracy by manifest refraction was better than the predicted accuracy had Seidel or non-Seidel aberrometric refractions been used for surgical planning. Using the Seidel method improved the accuracy in myopic eyes but not in hyperopic eyes. Dr. Reinstein is a consultant to Carl Zeiss Meditec AG and has a proprietary interest in the Artemis technology (Arcscan Inc., Morrison, Colorado, USA) through patents administered by the Cornell Center for Technology Enterprise and Commercialization, Ithaca, New York. No other author has a financial or proprietary interest in any material or method mentioned. Copyright © 2012 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.

Visual disability, visual function, and myopia among rural chinese secondary school children: the Xichang Pediatric Refractive Error Study (X-PRES)--report 1.

PubMed

Congdon, Nathan; Wang, Yunfei; Song, Yue; Choi, Kai; Zhang, Mingzhi; Zhou, Zhongxia; Xie, Zhenling; Li, Liping; Liu, Xueyu; Sharma, Abhishek; Wu, Bin; Lam, Dennis S C

2008-07-01

To evaluate visual acuity, visual function, and prevalence of refractive error among Chinese secondary-school children in a cross-sectional school-based study. Uncorrected, presenting, and best corrected visual acuity, cycloplegic autorefraction with refinement, and self-reported visual function were assessed in a random, cluster sample of rural secondary school students in Xichang, China. Among the 1892 subjects (97.3% of the consenting children, 84.7% of the total sample), mean age was 14.7 +/- 0.8 years, 51.2% were female, and 26.4% were wearing glasses. The proportion of children with uncorrected, presenting, and corrected visual disability (< or = 6/12 in the better eye) was 41.2%, 19.3%, and 0.5%, respectively. Myopia < -0.5, < -2.0, and < -6.0 D in both eyes was present in 62.3%, 31.1%, and 1.9% of the subjects, respectively. Among the children with visual disability when tested without correction, 98.7% was due to refractive error, while only 53.8% (414/770) of these children had appropriate correction. The girls had significantly (P < 0.001) more presenting visual disability and myopia < -2.0 D than did the boys. More myopic refractive error was associated with worse self-reported visual function (ANOVA trend test, P < 0.001). Visual disability in this population was common, highly correctable, and frequently uncorrected. The impact of refractive error on self-reported visual function was significant. Strategies and studies to understand and remove barriers to spectacle wear are needed.

Polar Value Analysis of Low to Moderate Astigmatism with Wavefront-Guided Sub-Bowman Keratomileusis

PubMed Central

Zhang, Yu

2017-01-01

Purpose To evaluate the astigmatic outcomes of wavefront-guided sub-Bowman keratomileusis (WFG-SBK) for low to moderate myopic astigmatism. Methods This study enrolled 100 right eyes from 100 patients who underwent WFG-SBK for the correction of myopia and astigmatism. The polar value method was performed with anterior and posterior corneal astigmatism measured with Scheimpflug camera combined with Placido corneal topography (Sirius, CSO) and refractive astigmatism preoperatively and 1 month, 3 months, and 6 months postoperatively. Results Similar results for surgically induced astigmatism (SIA) and error of the procedure in both anterior corneal astigmatism (ACA) and total ocular astigmatism (TOA). There was a minor undercorrection of the cylinder in both ACA and TOA. Posterior corneal astigmatism (PCA) showed no significant change. Conclusions Wavefront-guided SBK could provide good astigmatic outcomes for the correction of low to moderate myopic astigmatism. The surgical effects were largely attributed to the astigmatic correction of the anterior corneal surface. Posterior corneal astigmatism remained unchanged even after WFG-SBK for myopic astigmatism. Polar value analysis can be used to guide adjustments to the treatment cylinder alongside a nomogram designed to optimize postoperative astigmatic outcomes in myopic WFG-SBK. PMID:28831306

Peripheral Vision Can Influence Eye Growth and Refractive Development in Infant Monkeys

PubMed Central

Smith, Earl L.; Kee, Chea-su; Ramamirtham, Ramkumar; Qiao-Grider, Ying; Hung, Li-Fang

2006-01-01

PURPOSE Given the prominence of central vision in humans, it has been assumed that visual signals from the fovea dominate emmetropization. The purpose of this study was to examine the impact of peripheral vision on emmetropization. METHODS Bilateral, peripheral form deprivation was produced in 12 infant monkeys by rearing them with diffusers that had either 4- or 8-mm apertures centered on the pupils of each eye, to allow 24° or 37° of unrestricted central vision, respectively. At the end of the lens-rearing period, an argon laser was used to ablate the fovea in one eye of each of seven monkeys. Subsequently, all the animals were allowed unrestricted vision. Refractive error and axial dimensions were measured along the pupillary axis by retinoscopy and A-scan ultrasonography, respectively. Control data were obtained from 21 normal monkeys and 3 infants reared with binocular plano lenses. RESULTS Nine of the 12 treated monkeys had refractive errors that fell outside the 10th- and 90th-percentile limits for the age-matched control subjects, and the average refractive error for the treated animals was more variable and significantly less hyperopic/more myopic (+0.03 ± 2.39 D vs. +2.39 ± 0.92 D). The refractive changes were symmetric in the two eyes of a given animal and axial in nature. After lens removal, all the treated monkeys recovered from the induced refractive errors. No interocular differences in the recovery process were observed in the animals with monocular foveal lesions. CONCLUSIONS On the one hand, the peripheral retina can contribute to emmetropizing responses and to ametropias produced by an abnormal visual experience. On the other hand, unrestricted central vision is not sufficient to ensure normal refractive development, and the fovea is not essential for emmetropizing responses. PMID:16249469

Diagnostic Accuracy of Optical Coherence Tomography and Scanning Laser Tomography for Identifying Glaucoma in Myopic Eyes.

PubMed

Malik, Rizwan; Belliveau, Anne C; Sharpe, Glen P; Shuba, Lesya M; Chauhan, Balwantray C; Nicolela, Marcelo T

2016-06-01

Ruling out glaucoma in myopic eyes often poses a diagnostic challenge because of atypical optic disc morphology and visual field defects that can mimic glaucoma. We determined whether neuroretinal rim assessment based on Bruch's membrane opening (BMO), rather than conventional optic disc margin (DM)-based assessment or retinal nerve fiber layer (RNFL) thickness, yielded higher diagnostic accuracy in myopic patients with glaucoma. Case-control, cross-sectional study. Myopic patients with glaucoma (n = 56) and myopic normal controls (n = 74). Myopic subjects with refraction error greater than -2 diopters (D) (spherical equivalent) and typical myopic optic disc morphology, with and without glaucoma, were recruited from a glaucoma clinic and a local optometry practice. The final classification of myopic glaucoma or myopic control was based on consensus assessment by 3 clinicians of visual fields and optic disc photographs. Participants underwent imaging with confocal scanning laser tomography for measurement of DM rim area (DM-RA) and with spectral domain optical coherence tomography (SD OCT) for quantification of a BMO-based neuroretinal rim parameter, minimum rim width (BMO-MRW), and RNFL thickness. Sensitivity of DM-RA, BMO-MRW, and RNFL thickness at a fixed specificity of 90% and partial area under the curves (pAUCs) for global and sectoral parameters for specificities ≥90%. Sensitivities at 90% specificity were 30% for DM-RA and 71% for both BMO-MRW and RNFL thickness. The pAUC was higher for the BMO-MRW compared with DM-RA (P < 0.001), but similar to RNFL thickness (P > 0.5). Sectoral values of BMO-MRW tended to have a higher, but nonsignificant, pAUC across all sectors compared with RNFL thickness. Bruch's membrane opening MRW is more sensitive than DM-RA and similar to RNFL thickness for the identification of glaucoma in myopic eyes and offers a valuable diagnostic tool for patients with glaucoma with myopic optic discs. Copyright © 2016 American Academy of Ophthalmology. Published by Elsevier Inc. All rights reserved.

Education and myopia: assessing the direction of causality by mendelian randomisation.

PubMed

Mountjoy, Edward; Davies, Neil M; Plotnikov, Denis; Smith, George Davey; Rodriguez, Santiago; Williams, Cathy E; Guggenheim, Jeremy A; Atan, Denize

2018-06-06

To determine whether more years spent in education is a causal risk factor for myopia, or whether myopia is a causal risk factor for more years in education. Bidirectional, two sample mendelian randomisation study. Publically available genetic data from two consortiums applied to a large, independent population cohort. Genetic variants used as proxies for myopia and years of education were derived from two large genome wide association studies: 23andMe and Social Science Genetic Association Consortium (SSGAC), respectively. 67 798 men and women from England, Scotland, and Wales in the UK Biobank cohort with available information for years of completed education and refractive error. Mendelian randomisation analyses were performed in two directions: the first exposure was the genetic predisposition to myopia, measured with 44 genetic variants strongly associated with myopia in 23andMe, and the outcome was years in education; and the second exposure was the genetic predisposition to higher levels of education, measured with 69 genetic variants from SSGAC, and the outcome was refractive error. Conventional regression analyses of the observational data suggested that every additional year of education was associated with a more myopic refractive error of -0.18 dioptres/y (95% confidence interval -0.19 to -0.17; P<2e-16). Mendelian randomisation analyses suggested the true causal effect was even stronger: -0.27 dioptres/y (-0.37 to -0.17; P=4e-8). By contrast, there was little evidence to suggest myopia affected education (years in education per dioptre of refractive error -0.008 y/dioptre, 95% confidence interval -0.041 to 0.025, P=0.6). Thus, the cumulative effect of more years in education on refractive error means that a university graduate from the United Kingdom with 17 years of education would, on average, be at least -1 dioptre more myopic than someone who left school at age 16 (with 12 years of education). Myopia of this magnitude would be sufficient to necessitate the use of glasses for driving. Sensitivity analyses showed minimal evidence for genetic confounding that could have biased the causal effect estimates. This study shows that exposure to more years in education contributes to the rising prevalence of myopia. Increasing the length of time spent in education may inadvertently increase the prevalence of myopia and potential future visual disability. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/permissions.

Education and myopia: assessing the direction of causality by mendelian randomisation

PubMed Central

Mountjoy, Edward; Davies, Neil M; Plotnikov, Denis; Smith, George Davey; Rodriguez, Santiago; Williams, Cathy E; Guggenheim, Jeremy A

2018-01-01

Abstract Objectives To determine whether more years spent in education is a causal risk factor for myopia, or whether myopia is a causal risk factor for more years in education. Design Bidirectional, two sample mendelian randomisation study. Setting Publically available genetic data from two consortiums applied to a large, independent population cohort. Genetic variants used as proxies for myopia and years of education were derived from two large genome wide association studies: 23andMe and Social Science Genetic Association Consortium (SSGAC), respectively. Participants 67 798 men and women from England, Scotland, and Wales in the UK Biobank cohort with available information for years of completed education and refractive error. Main outcome measures Mendelian randomisation analyses were performed in two directions: the first exposure was the genetic predisposition to myopia, measured with 44 genetic variants strongly associated with myopia in 23andMe, and the outcome was years in education; and the second exposure was the genetic predisposition to higher levels of education, measured with 69 genetic variants from SSGAC, and the outcome was refractive error. Results Conventional regression analyses of the observational data suggested that every additional year of education was associated with a more myopic refractive error of −0.18 dioptres/y (95% confidence interval −0.19 to −0.17; P<2e-16). Mendelian randomisation analyses suggested the true causal effect was even stronger: −0.27 dioptres/y (−0.37 to −0.17; P=4e-8). By contrast, there was little evidence to suggest myopia affected education (years in education per dioptre of refractive error −0.008 y/dioptre, 95% confidence interval −0.041 to 0.025, P=0.6). Thus, the cumulative effect of more years in education on refractive error means that a university graduate from the United Kingdom with 17 years of education would, on average, be at least −1 dioptre more myopic than someone who left school at age 16 (with 12 years of education). Myopia of this magnitude would be sufficient to necessitate the use of glasses for driving. Sensitivity analyses showed minimal evidence for genetic confounding that could have biased the causal effect estimates. Conclusions This study shows that exposure to more years in education contributes to the rising prevalence of myopia. Increasing the length of time spent in education may inadvertently increase the prevalence of myopia and potential future visual disability. PMID:29875094

Study of Theories about Myopia Progression (STAMP) Design and Baseline Data

PubMed Central

Berntsen, David A.; Mutti, Donald O.; Zadnik, Karla

2011-01-01

Purpose The Study of Theories about Myopia Progression (STAMP) is a two-year, double-masked, randomized clinical trial of myopic children 6 to 11 years old. STAMP will evaluate the one-year effect of progressive addition lenses (PALs) compared to single vision lenses (SVLs) on central refraction, peripheral refraction in four quadrants, and accommodative response and convergence. STAMP will also evaluate any changes one year after discontinuing PALs. Baseline characteristics of enrolled children are reported. Methods Eligible children had a high accommodative lag and either: (1) low myopia (less myopic than −2.25 D spherical equivalent) or (2) high myopia (more myopic that −2.25 D spherical equivalent) and esophoria at near. Children were randomly assigned to wear either PALs or SVLs for one year to determine the difference in myopia progression in the PAL group relative to the SVL group. All children will then wear SVLs for the second year to evaluate the permanence of any treatment effect. Complete ocular biometric data are collected at six-month intervals. Results Over 17 months, 192 children were screened, and 85 (44%) were eligible and enrolled. Of these 85 children, 44 (52%) were female, and 54 (64%) were esophoric at near. The mean age (± SD) was 9.8 ± 1.3 years. The right eye mean cycloplegic spherical equivalent refractive error was −1.95 ± 0.78 D. Horizontal relative peripheral hyperopia (30° nasal retina +0.56 ± 0.59 D; 30° temporal retina +0.61 ± 0.77 D) and vertical relative peripheral myopia (30° superior retina −0.36 ± 0.92 D; 20° inferior retina −0.48 ± 0.83 D) were found. Conclusions The baseline data for STAMP are reported. Asymmetry between vertical and horizontal meridian relative peripheral refraction was found. STAMP will utilize the ocular biometric changes associated with the PAL-treatment effect to attempt to elucidate the mechanism responsible for the treatment effect. PMID:20935586

Levodopa inhibits the development of form-deprivation myopia in guinea pigs.

PubMed

Mao, Junfeng; Liu, Shuangzhen; Qin, Wenjuan; Li, Fengyun; Wu, Xiaoying; Tan, Qian

2010-01-01

It has been shown that visual deprivation leads to a myopic refractive error and also reduces the retinal concentration of dopamine. Exogenously 3,4-dihydroxy-L-phenylalanine (levodopa, L-DOPA) can be converted into dopamine in vivo, which safely and effectively treats Parkinson disease. Moreover, L-DOPA was also used in the treatment of amblyopia in clinical studies. However, the effect of L-DOPA on the development of myopia has not been studied. The aim of this study was to investigate whether intraperitoneal injection of L-DOPA could inhibit form-deprivation myopia in guinea pigs and to explore a new strategy for drug treatment of myopia. Sixty guinea pigs, at age of 4 weeks, were randomly divided into six groups: normal control, L-DOPA group, saline group, deprived group, deprived plus L-DOPA group, and deprived plus saline group. Form deprivation was induced with translucent eye shields on the right eye and lasted for 10 days. L-DOPA was injected intraperitoneally into the guinea pig once a day. The corneal radius of curvature, refraction, and axial length were measured in all animals. Subsequently, retinal dopamine content was evaluated by high-performance liquid chromatography with electrochemical detection. Ten days of eye occlusion caused the form-deprived eyes to elongate and become myopic, and retinal dopamine content to decrease, but the corneal radius of curvature was not affected. Repeated intraperitoneal injection of L-DOPA could inhibit the myopic shift (from -3.62 +/- 0.98 D to -1.50 +/- 0.38 D; p < 0.001) due to goggles occluding and compensate retinal dopamine (from 0.65 +/- 0.10 ng to 1.33 +/- 0.23 ng; p < 0.001). Administration of L-DOPA to the unoccluded animals had no effect on its ocular refraction. There was no effect of intraperitoneal saline on the ocular refractive state and retinal dopamine. Systemic L-DOPA was partly effective in this guinea pig model and, therefore, is worth testing for effectiveness in progressing human myopes.

Myopia and/or longer axial length are protective against diabetic retinopathy: a meta-analysis.

PubMed

Fu, Yu; Geng, Dengfeng; Liu, Hua; Che, Huixin

2016-06-01

To evaluate the current evidence of the relationship between myopia, together with its structural and refractive component, and diabetic retinopathy (DR) risk. A systematic search was performed up to April, 2015. Summary odds ratios (ORs) and 95% confidence intervals (CIs) were calculated employing random-effects models. Three models were used to assess the association between myopia and risk of DR: axial length (AL) (per millimetre increase) and DR; myopia (myopia versus non-myopia) and DR; refractive error (RE) (per D decrease) and DR. Publication bias of the literature was evaluated using Begg's funnel plots and Egger's test. A total of 11 studies that met the predefined criteria were included in this meta-analysis. Overall, longer AL (per millimetre increase) was associa-ted with a significantly decreased risk of DR (combined OR, 0.75; 95% CI, 0.65-0.86; p < 0.001); myopic eyes (myopia versus non-myopia) showed a lower risk of DR (combined OR, 0.70; 95% CI, 0.58-0.85; p < 0.001). A greater degree of myopic RE (per D decrease) also revealed a significantly decreased risk of DR (combined OR, 0.89; 95% CI, 0.85-0.93; p < 0.001). The sensitivity analyses and cumulative meta-analysis showed similar results. No publication bias was detected in any of the three models. This meta-analysis suggests that both myopic refraction and longer AL are associated with a lower risk of DR. Further studies are needed to determine exact mechanisms underpinning the protective effect of myopia against DR. © 2015 Acta Ophthalmologica Scandinavica Foundation. Published by John Wiley & Sons Ltd.

Influence of the flap on outcomes in corneal refractive surgery with femtosecond laser: SMILE vs. FLEx.

PubMed

Alió, J L; El Bahrawy, M; Angelov, A; Ortiz, D; Yébana, P

2017-05-01

To investigate the influence of creating a flap on the postoperative optical quality of the cornea in terms of predicted corneal curvature and Seidel aberrations after 2 modalities of femtosecond assisted corneal lenticule extraction laser for the correction of myopia and myopic astigmatism: The flapless procedure small incision lenticular extraction (SMILE) and the flap-based femtosecond lenticular extraction (FLEx). The study is a prospective consecutive non-randomised comparative interventional case series including 64 eyes with myopic or myopic astigmatism refractive errors. Patients were divided into 2 groups matched for age, sex and myopia. One group underwent SMILE treatment and the other underwent FLEx treatment. Seidel aberrations root-mean-square values were obtained with a 10mm aperture using the ATLAS 9000 topographer before surgery and 3 months after surgery. The relationship between the post-surgical corneal radius and the predicted sculpted radius were analysed in each group. The mean percentage change in the curvature radius was -2.03% in the FLEx group and -1.77% in the SMILE group (P=.655). The higher correlation for the SMILE group demonstrates a better predictability after the surgery. As regards corneal aberrations, the FLEx treatment showed a greater increase of higher order aberrations than SMILE treatment (P=.04). The mean refractive change in corneal curvature, which is indirectly related to the biomechanical response of the corneal surface after the lenticule cut and extraction, was similar after both treatments. However, the flap based FLEx procedure showed a greater degradation of the corneal optical quality in terms of induction of higher order aberrations. Copyright © 2016 Sociedad Española de Oftalmología. Publicado por Elsevier España, S.L.U. All rights reserved.

Single-Step Transepithelial PRK vs Alcohol-Assisted PRK in Myopia and Compound Myopic Astigmatism Correction.

PubMed

Kaluzny, Bartlomiej J; Cieslinska, Iwona; Mosquera, Samuel A; Verma, Shwetabh

2016-02-01

Transepithelial photorefractive keratectomy (tPRK), where both the epithelium and stroma are removed in a single-step, is a relatively new procedure of laser refractive error correction. This study compares the 3-month results of myopia and compound myopic astigmatism correction by tPRK or conventional alcohol-assisted PRK (aaPRK).This prospective, nonrandomized, case-control study recruited 148 consecutive patients; 93 underwent tPRK (173 eyes) and 55 aaPRK (103 eyes). Refractive results, predictability, safety, and efficacy were evaluated during the 3-month follow-up. The main outcome measures were uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), and mean refractive spherical equivalent (MRSE).Mean preoperative MRSE was -4.30 ± 1.72 D and -4.33 ± 1.96 D, respectively (P = 0.87). The 3-month follow-up rate was 82.1% in the tPRK group (n = 145) and 86.4% in aaPRK group (n = 90), P = 0.81. Postoperative UDVA was 20/20 or better in 97% and 94% of eyes, respectively (P = 0.45). In the tPRK and aaPRK groups, respectively, 13% and 21% of eyes lost 1 line of CDVA, and 30% and 31% gained 1 or 2 lines (P = 0.48). Mean postoperative MRSE was -0.14 ± 0.26 D in the tPRK group and -0.12 ± 0.20 D in the aaPRK group (P = 0.9). The correlation between attempted versus achieved MRSE was equally high in both groups.Single-step transepithelial PRK and conventional PRK provide very similar results 3 months postoperatively. These procedures are predictable, effective, and safe for correction of myopia and compound myopic astigmatism.

Curvature of iris profile in spectral domain optical coherence tomography and dependency to refraction, age and pupil size - the MIPH Eye&Health Study.

PubMed

Schuster, Alexander K; Fischer, Joachim E; Vossmerbaeumer, Urs

2017-03-01

Optical coherence tomography (OCT) of the anterior segment allows quantitative analysis of the geometry of the iris. We performed spectral domain OCT examinations in healthy emmetropic, hyperopic and myopic subjects to investigate iris curvature and its associations. In a cross-sectional study, out of 4617 eyes (2309 subjects) those with refractive errors of <-4 or >+3 dioptres were identified by objective refraction. The iris was examined using the anterior segment mode of a spectral domain 3D OCT-2000 (Topcon Inc., Japan) in the temporal meridian, and OCT scans were investigated with respect to presence and amount of convex and concave iris configuration. Ninety-three eyes of 50 subjects served as emmetropic group (-0.5 ≤ x ≤+0.5 dioptres). Previous ocular surgery was exclusion criterion. Six hundred and sixty-eight eyes of 398 persons [292 male (76%); age range; 18-66 years] were included in the study. In the myopic group, 105 eyes had a concave iris configuration (26%), while in the hyperopic group, no eye had this configuration (0%) and in the emmetropic group five eyes (5%). Convex iris configuration was found in 96% of hyperopic, in 85% of the emmetropic and in 67% of the myopic eyes. There was an association between concave iris configuration and myopia, younger age and male gender, and with anterior chamber angle width. Spectral domain OCT images can be used for analysis of the iris structure and geometry. Our results are limited to the properties of the study population having an age range from 18 to 66 years and consisting mainly of men. © 2016 Acta Ophthalmologica Scandinavica Foundation. Published by John Wiley & Sons Ltd.

The effects of simultaneous dual focus lenses on refractive development in infant monkeys.

PubMed

Arumugam, Baskar; Hung, Li-Fang; To, Chi-Ho; Holden, Brien; Smith, Earl L

2014-10-16

We investigated the effects of two simultaneously imposed, competing focal planes on refractive development in monkeys. Starting at 3 weeks of age and continuing until 150 ± 4 days of age, rhesus monkeys were reared with binocular dual-focus spectacle lenses. The treatment lenses had central 2-mm zones of zero power and concentric annular zones with alternating powers of +3.0 diopter [D] and plano (pL or 0 D) (n = 7; +3D/pL) or -3.0 D and plano (n = 7; -3D/pL). Retinoscopy, keratometry, and A-scan ultrasonography were performed every 2 weeks throughout the treatment period. For comparison purposes data were obtained from monkeys reared with full field (FF) +3.0 (n = 4) or -3.0 D (n = 5) lenses over both eyes and 33 control animals reared with unrestricted vision. The +3 D/pL lenses slowed eye growth resulting in hyperopic refractive errors that were similar to those produced by FF+3 D lenses (+3 D/pL = +5.25 D, FF +3 D = +4.63 D; P = 0.32), but significantly more hyperopic than those observed in control monkeys (+2.50 D, P = 0.0001). One -3 D/pL monkey developed compensating axial myopia; however, in the other -3 D/pL monkeys refractive development was dominated by the zero-powered portions of the treatment lenses. The refractive errors for the -3 D/pL monkeys were more hyperopic than those in the FF -3 D monkeys (-3 D/pL = +3.13 D, FF -3D = -1.69 D; P = 0.01), but similar to those in control animals (P = 0.15). In the monkeys treated with dual-focus lenses, refractive development was dominated by the more anterior (i.e., relatively myopic) image plane. The results indicate that imposing relative myopic defocus over a large proportion of the retina is an effective means for slowing ocular growth. Copyright 2014 The Association for Research in Vision and Ophthalmology, Inc.

The Effects of Simultaneous Dual Focus Lenses on Refractive Development in Infant Monkeys

PubMed Central

Arumugam, Baskar; Hung, Li-Fang; To, Chi-ho; Holden, Brien; Smith, Earl L.

2014-01-01

Purpose. We investigated the effects of two simultaneously imposed, competing focal planes on refractive development in monkeys. Methods. Starting at 3 weeks of age and continuing until 150 ± 4 days of age, rhesus monkeys were reared with binocular dual-focus spectacle lenses. The treatment lenses had central 2-mm zones of zero power and concentric annular zones with alternating powers of +3.0 diopter [D] and plano (pL or 0 D) (n = 7; +3D/pL) or −3.0 D and plano (n = 7; −3D/pL). Retinoscopy, keratometry, and A-scan ultrasonography were performed every 2 weeks throughout the treatment period. For comparison purposes data were obtained from monkeys reared with full field (FF) +3.0 (n = 4) or −3.0 D (n = 5) lenses over both eyes and 33 control animals reared with unrestricted vision. Results. The +3 D/pL lenses slowed eye growth resulting in hyperopic refractive errors that were similar to those produced by FF+3 D lenses (+3 D/pL = +5.25 D, FF +3 D = +4.63 D; P = 0.32), but significantly more hyperopic than those observed in control monkeys (+2.50 D, P = 0.0001). One −3 D/pL monkey developed compensating axial myopia; however, in the other −3 D/pL monkeys refractive development was dominated by the zero-powered portions of the treatment lenses. The refractive errors for the −3 D/pL monkeys were more hyperopic than those in the FF −3 D monkeys (−3 D/pL = +3.13 D, FF −3D = −1.69 D; P = 0.01), but similar to those in control animals (P = 0.15). Conclusions. In the monkeys treated with dual-focus lenses, refractive development was dominated by the more anterior (i.e., relatively myopic) image plane. The results indicate that imposing relative myopic defocus over a large proportion of the retina is an effective means for slowing ocular growth. PMID:25324283

Effect of iris registration on outcomes of FEMTOLASIK for myopia and myopic astigmatism.

PubMed

Ghoreishi, Mohammad; Beni, Zahra Naderi; Beni, Afsaneh Naderi; Kianersi, Farzan

2017-09-05

To compare the visual and refractive outcomes after FEMTOLASIK with and without iris registration. In this randomized, prospective, comparative, contralateral eye study, 118 eyes of 59 patients with myopia and myopic astigmatism underwent LASIK using the Femto LDV femtosecond laser (160 µm) and the MEL80 with or without iris registration. For each patient, iris registration FEMTOLASIK was performed on one eye and non-iris registration FEMTOLASIK was performed on the other eye, assigned at random. Patients were evaluated before and 12 months. Uncorrected visual acuity, best-corrected visual acuity, manifest refraction, contrast sensitivity, and higher-order aberrations (HOAs) were evaluated. At 12 months, the mean UDVA was 0.002 ± 0.07 logMAR (20/19) in iris registration eyes and 0.00 ± 0.06 logMAR (20/24) in non-iris registration eyes (P = 0.9). 61% of iris registration eyes and 71.2% of non-iris registration eyes achieved a UDVA of 20/20 or better (P = 0.31); 98.3% of eyes with the iris registration FEMTOLASIK and 94.9% with the non-iris registration FEMTOLASIK were within ±0.50 D from emmetropia (P = 0.71). No statistically significant difference was found in postoperative contrast sensitivity between groups at 3, 6, 12, or 18 cycles/degree (P > 0.05). There was significant increase in total HOA root mean square in two groups. The mean error magnitude of surgically induced astigmatism 12 months postoperatively was -0.33 in iris registration eyes and -0.24 in the non-iris registration eyes (P = 0.36). FEMTOLASIK with and without iris registration provides similar results in myopic and myopic astigmatism patients.

The relationship between scleral staphyloma and choroidal thinning in highly myopic eyes: The Beijing Eye Study.

PubMed

Zhou, Ling Xiao; Shao, Lei; Xu, Liang; Wei, Wen Bin; Wang, Ya Xing; You, Qi Sheng

2017-08-29

Based on the Beijing Eye Study 2011, a detailed ophthalmic examination was performed including spectral-domain optical coherence tomography (SD-OCT) with enhanced depth imaging for measurement of subfoveal choroidal thickness (SFCT) and relative height of posterior scleral staphyloma. OCT images were obtained in 103 highly myopic eyes (≤-6.00 diopters) and 227 normal eyes. The mean SFCT in highly myopic eyes was 110.6 ± 85.2 μm (range, 3 to 395 μm). The SFCT of high myopia without posterior scleral staphyloma(55 eyes) was 157.79 ± 85.18 μm, which was significantly greater than that (54.94 ± 49.96 μm) of high myopia with posterior scleral staphyloma (48 eyes) (P < 0.001). In multivariate analysis, posterior scleral staphyloma was the most important factor of choroidal thinning in high myopia (F = 22.63; P < 0.001), then age (F = 19.14; P < 0.001), axial length (F = 17.37; P < 0.001) and gender (F = 17.31; P < 0.001). The SFCT in highly myopic eyes is very thin and undergoes further thinning with increasing age and axial length (refractive error). Posterior staphyloma formation was a key factor in choroidal thinning in highly myopic eyes and to be a good indicator for risk management of choroidal thinning. Abnormalities of the choroid may play a role in the pathogenesis of myopic degeneration.

[Epidemiologic study of refractive errors in schoolchildren in socioeconomically deprived regions in Tunisia].

PubMed

Ayed, T; Sokkah, M; Charfi, O; El Matri, L

2002-09-01

This study's purpose was to estimate the prevalence of common refractive errors in schoolchildren in low socioeconomic regions in Tunisia and to assess their effect on school performance. This was a cross-sectional study done from November 1999 to January 2000 within the context of health care screening campaigns carried out by volunteer ophthalmologists and opticians in low-end socioeconomic regions in Tunisia. The concerned population was schoolchildren living in the cities of Tunis and Tabarka (North), Kerkena (Center), and Tozeur (South). We examined a total of 708 children with a mean age of 11.9 +/-3.21 years (from 6 to 20 years) and a sex ratio of 0.84. A cycloplegic refraction examination was performed on all the children. Statistical analyses with the chi squared test and the Fisher exact test allowed us to calculate the prevalence of the refractive errors totally and separately as well as the distribution according to age, sex, and region. We also searched for a possible relation between refractive errors and academic failure. Among the 708 children, 57.2% [CI(95)=53.4-60] had refractive errors, of which 31.6% [CI(95)=28.2-35.2] were hyperopic, whereas 9.1% [CI(95)=7.1-11.5] were myopic. Astigmatism was found in 16.4% [CI(95)=13.7-19.3]. The prevalence of myopia was significantly higher after the age of fourteen. It increased significantly with age (P=0.0003). The prevalence of hyperopia was significantly higher between the ages of 8 and 11 (P=0.0004). Hyperopic astigmatism was significantly more frequent between 6 and 9 years of age (P=0.001). There was no significant difference regarding sex. However, the distribution of the refractive errors by region showed a significantly high level of myopia in Tunis, Kerkena, and Tozeur. This difference disappeared with increasing age. The study of the effect of these refractive errors on school performance of these children from poor areas showed a significant association between all types of refractive errors and academic failure, with an odds ratio of 2.13 for all types of refractive errors, 2.69 for hyperopia, 2.87 for myopia, and 2.73 for astigmatism. This study showed the prevalence of refractive errors in a poor population of schoolchildren and emphasized the importance of such examinations. The ability of a child to participate in the educational experience is at least partially dependent on good vision.

The child self-refraction study results from urban Chinese children in Guangzhou.

PubMed

He, Mingguang; Congdon, Nathan; MacKenzie, Graeme; Zeng, Yangfa; Silver, Joshua D; Ellwein, Leon

2011-06-01

To compare visual and refractive outcomes between self-refracting spectacles (Adaptive Eyecare, Ltd, Oxford, UK), noncycloplegic autorefraction, and cycloplegic subjective refraction. Cross-sectional study. Chinese school-children aged 12 to 17 years. Children with uncorrected visual acuity ≤ 6/12 in either eye underwent measurement of the logarithm of the minimum angle of resolution visual acuity, habitual correction, self-refraction without cycloplegia, autorefraction with and without cycloplegia, and subjective refraction with cycloplegia. Proportion of children achieving corrected visual acuity ≥ 6/7.5 with each modality; difference in spherical equivalent refractive error between each of the modalities and cycloplegic subjective refractive error. Among 556 eligible children of consenting parents, 554 (99.6%) completed self-refraction (mean age, 13.8 years; 59.7% girls; 54.0% currently wearing glasses). The proportion of children with visual acuity ≥ 6/7.5 in the better eye with habitual correction, self-refraction, noncycloplegic autorefraction, and cycloplegic subjective refraction were 34.8%, 92.4%, 99.5% and 99.8%, respectively (self-refraction versus cycloplegic subjective refraction, P<0.001). The mean difference between cycloplegic subjective refraction and noncycloplegic autorefraction (which was more myopic) was significant (-0.328 diopter [D]; Wilcoxon signed-rank test P<0.001), whereas cycloplegic subjective refraction and self-refraction did not differ significantly (-0.009 D; Wilcoxon signed-rank test P = 0.33). Spherical equivalent differed by ≥ 1.0 D in either direction from cycloplegic subjective refraction more frequently among right eyes for self-refraction (11.2%) than noncycloplegic autorefraction (6.0%; P = 0.002). Self-refraction power that differed by ≥ 1.0 D from cycloplegic subjective refractive error (11.2%) was significantly associated with presenting without spectacles (P = 0.011) and with greater absolute power of both spherical (P = 0.025) and cylindrical (P = 0.022) refractive error. Self-refraction seems to be less prone to accommodative inaccuracy than noncycloplegic autorefraction, another modality appropriate for use in areas where access to eye care providers is limited. Visual results seem to be comparable. Greater cylindrical power is associated with less accurate results; the adjustable glasses used in this study cannot correct astigmatism. Further studies of the practical applications of this modality are warranted. Proprietary or commercial disclosure may be found after the references. Copyright © 2011 American Academy of Ophthalmology. Published by Elsevier Inc. All rights reserved.

M to L cone ratios determine eye sizes and baseline refractions in chickens.

PubMed

Gisbert, Sandra; Schaeffel, Frank

2018-07-01

Following a hypothesis raised by M. and J. Neitz, Seattle, we have tested whether the abundance and the ratio of Long wavelength-sensitive (L) to Middle wavelength-sensitive (M) cones may affect eye size and development of myopia in the chicken. Fourteen chickens were treated with frosted plastic diffusers in front of one eye on day 10 post-hatching for a period of 7 days to induce deprivation myopia. Ocular dimensions were measured by A-scan ultrasonography at the beginning and at the end of the treatment and development of refractive state was tracked using infrared photorefraction. At the end of the treatment period, L and M cone densities and ratios were analyzed in retinal flat mounts of both myopic and control eyes, using the red and yellow oil droplets as markers. Because large numbers of cones were counted (>10000), software was written in Visual C++ for automated cone detection and density analysis. (1) On average, 9.7 ± 1.7D of deprivation myopia was induced in 7 days (range from 6.8D to 13.7D) with an average increase in axial length by 0.65 ± 0.20 mm (range 0.42 mm-1.00 mm), (2) the increase in vitreous chamber depth was correlated with the increase in myopic refractive error, (3) average central M cone densities were 10,498 cells/mm 2 , and L cone densities 9574 cells/mm 2 . In the periphery, M cone densities were 6343 cells/mm 2 and L cones 5735 cells/mm 2 (4) M to L cone ratios were highly correlated in both eyes of each animal (p < 0.01 in all cases), (5) the most striking finding was that ratios of M to L cones were significantly correlated with vitreous chamber depths and refractive states in the control eyes with normal vision, both in the central and peripheral retinas (p < 0.05 to p < 0.01), (6) M to L cone ratios did however not predict the amount of deprivation myopia that could be induced. M and L cone ratios are most likely genetically determined in each animal. The more L cones, the deeper the vitreous chambers and the more myopic were the refractions in eyes. M to L cone ratios may determine the set point of emmetropization and thereby ultimately the probability of becoming myopic. Deprivation myopia was not determined by M to L cone ratios. Copyright © 2018 The Authors. Published by Elsevier Ltd.. All rights reserved.

The Distinct Biometric Features of High Myopia Compared to Moderate Myopia.

PubMed

Chung, Hye Jin; Park, Chan Kee

2016-12-01

To evaluate changes in biometric parameters in myopic eyes. 412 eyes of 412 young myopic patients underwent ophthalmic examinations including assessments of refractive error, axial length (AL), anterior chamber depth (ACD), and central corneal thickness (CCT). By using spectral domain optical coherence tomography (SD-OCT), peripapillary retinal nerve fiber layer (pRNFL) thickness was measured. Subjects were divided into two groups: a moderate-myope group (-6 diopters (D) or more) and a high-myope group (less than -6 D). The relationships among ocular biometric parameters including pRNFL thickness, AL, ACD, and CCT were calculated for each group. In the moderate-myopia group, the anterior chamber deepened as AL increased (Pearson's coefficient = 0.346, p < 0.01). However, in the high-myopia group, ACD did not correlate with AL (Pearson's r = 0.065, p = 0.383). Average pRNFL thickness was also more related to SE than AL in highly myopic eyes. In highly myopic eyes, ACD did not increase as AL increased. pRNFL thickness was more related to SE than to AL. That might be due to the uneven elongation of anterior and posterior portions of the eyeball and the discrepancy between distance from the cornea to the fovea and distance from the cornea to the bottom of the eyeball as axial eye elongation. Interpretation of ocular biometric parameter in highly myopic eyes should consider these differences.

Prevalence of Refractive Error among Preschool Children in an Urban Population: The Baltimore Pediatric Eye Disease Study

PubMed Central

Giordano, Lydia; Friedman, David S.; Repka, Michael X.; Katz, Joanne; Ibironke, Josephine; Hawes, Patricia; Tielsch, James M.

2009-01-01

Purpose To determine the age-specific prevalence of refractive errors in White and African-American preschool children. Design The Baltimore Pediatric Eye Disease Study is a population-based evaluation of the prevalence of ocular disorders in children aged six through 71 months in Baltimore, Maryland, United States. Participants Among 4,132 children identified, 3,990 eligible children (97%) were enrolled and 2,546 children (62%) were examined. Methods Cycloplegic autorefraction was attempted on all children using a Nikon Retinomax K-Plus 2. If a reliable autorefraction could not be obtained after three attempts, cycloplegic streak retinoscopy was performed. Main Outcome Measures Mean spherical equivalent (SE) refractive error, astigmatism, and prevalence of higher refractive errors among African American and White children. Results The mean spherical equivalent (SE) of right eyes was +1.49 diopter (D) (standard deviation (SD) =1.23) in White and +0.71D (SD=1.35) in African-American children (mean difference of 0.78D, 95% CI: 0.67, 0.89). Mean SE refractive error did not decline with age in either group. The prevalence of myopia of 1.00 D or more in the eye with the lesser refractive error was 0.7% in White and 5.5% in African-American children (RR: 8.01 95% confidence interval (CI): 3.70, 17.35). The prevalence of hyperopia of +3D or more in the eye with the lesser refractive error was 8.9% in White and 4.4% in African-American children (relative risk (RR): 0.49, 95% CI: 0.35, 0.68). The prevalence of emmetropia (less than −1.00 D to less than +1.00 D) was 35.6% in Whites and 58.0 % in African-Americans (RR: 1.64, 95% CI: 1.49, 1.80). Based on published prescribing guidelines 5.1% of the children would have benefited from spectacle correction. However, only 1.3% had been previously prescribed correction. Conclusions Significant refractive errors are uncommon in this population of urban preschool children. There was no evidence for a myopic shift over this age range in this cross-sectional study. A small proportion of preschool children would likely benefit from refractive correction, but few have had this prescribed. PMID:19243832

Iris colour in relation to myopia among Chinese school-aged children.

PubMed

Pan, Chen-Wei; Qiu, Qin-Xiao; Qian, Deng-Juan; Hu, Dan-Ning; Li, Jun; Saw, Seang-Mei; Zhong, Hua

2018-01-01

Understanding the association of iris colour and myopia may provide further insights into the role of the wavelength of lights in the pathophysiology of myopia. We aim to assess the association of iris colour and myopia in a school-based sample of Chinese students. Two thousand three hundred and forty-six Year 7 students from 10 middle schools (93.5% response rate) aged 13-14 years in Mojiang, a small county located in Southwestern China, participated in the study. We obtained standardised slit lamp photographs and developed a grading system assessing iris colour (higher grade denoting a darker iris). Refractive error was measured after cycloplegia using an autorefractor by optometrists or trained technicians. An IOLMaster (www.zeiss.com) was used to measure ocular biometric parameters including axial length (AL). Of all the study participants, 693 (29.5%) were affected by myopia with the prevalence estimates being higher in girls (36.8%; 95% confidence interval [CI]: 34.0, 39.6) than in boys (22.8%; 95% CI: 20.4, 25.1) (p < 0.001). After adjusting for gender, height, parental history of myopia, time spent on computer, time spent watching TV, time spent outdoors, and time spent reading and writing, participants with a darker iris colour tended to have a higher prevalence of myopia, a more myopic refraction and a longer AL. Dose-response relationships were observed in all regression models (p for trend <0.05). Darker iris colour was associated with more myopic refractive errors and longer ALs among Chinese school-aged children and this association was independent of other known myopia-related risk factors. © 2017 The Authors Ophthalmic & Physiological Optics © 2017 The College of Optometrists.

Prevalence of Amblyopia and Refractive Errors Among Primary School Children

PubMed Central

Rajavi, Zhale; Sabbaghi, Hamideh; Baghini, Ahmad Shojaei; Yaseri, Mehdi; Moein, Hamidreza; Akbarian, Shadi; Behradfar, Narges; Hosseini, Simin; Rabei, Hossein Mohammad; Sheibani, Kourosh

2015-01-01

Purpose: To determine the prevalence of amblyopia and refractive errors among 7 to 12-year-old primary school children in Tehran, Iran. Methods: This population-based cross-sectional study included 2,410 randomly selected students. Visual acuity was tested using an E-chart on Yang vision tester. Refractive errors were measured by photorefractometry and cycloautorefraction. Strabismus was checked using cover test. Direct ophthalmoscopy was used to assess the anterior segment, lens opacities, red reflex and fundus. Functional amblyopia was defined as best corrected visual acuity ≤20/40 in one or both eyes with no anatomical problems. Results: Amblyopia was present in 2.3% (95% CI: 1.8% to 2.9%) of participants with no difference between the genders. Amblyopic subjects were significantly younger than non-amblyopic children (P=0.004). Overall, 15.9% of hyperopic and 5.9% of myopic cases had amblyopia. The prevalence of hyperopia ≥+2.00D, myopia ≤-0.50D, astigmatism ≥0.75D, and anisometropia (≥1.00D) was 3.5%, 4.9%, 22.6%, and 3.9%, respectively. With increasing age, the prevalence of myopia increased (P<0.001), that of hyperopia decreased (P=0.007), but astigmatism showed no change. Strabismus was found in 2.3% of cases. Strabismus (OR=17.9) and refractive errors, especially anisometropia (OR=12.87) and hyperopia (OR=11.87), were important amblyogenic risk factors. Conclusion: The high prevalence of amblyopia in our subjects in comparison to developed countries reveals the necessity of timely and sensitive screening methods. Due to the high prevalence of amblyopia among children with refractive errors, particularly high hyperopia and anisometropia, provision of glasses should be specifically attended by parents and supported by the Ministry of Health and insurance organizations. PMID:27051485

Education influences the association between genetic variants and refractive error: a meta-analysis of five Singapore studies

PubMed Central

Fan, Qiao; Wojciechowski, Robert; Kamran Ikram, M.; Cheng, Ching-Yu; Chen, Peng; Zhou, Xin; Pan, Chen-Wei; Khor, Chiea-Chuen; Tai, E-Shyong; Aung, Tin; Wong, Tien-Yin; Teo, Yik-Ying; Saw, Seang-Mei

2014-01-01

Refractive error is a complex ocular trait governed by both genetic and environmental factors and possibly their interplay. Thus far, data on the interaction between genetic variants and environmental risk factors for refractive errors are largely lacking. By using findings from recent genome-wide association studies, we investigated whether the main environmental factor, education, modifies the effect of 40 single nucleotide polymorphisms on refractive error among 8461 adults from five studies including ethnic Chinese, Malay and Indian residents of Singapore. Three genetic loci SHISA6-DNAH9, GJD2 and ZMAT4-SFRP1 exhibited a strong association with myopic refractive error in individuals with higher secondary or university education (SHISA6-DNAH9: rs2969180 A allele, β = −0.33 D, P = 3.6 × 10–6; GJD2: rs524952 A allele, β = −0.31 D, P = 1.68 × 10−5; ZMAT4-SFRP1: rs2137277 A allele, β = −0.47 D, P = 1.68 × 10−4), whereas the association at these loci was non-significant or of borderline significance in those with lower secondary education or below (P for interaction: 3.82 × 10−3–4.78 × 10−4). The evidence for interaction was strengthened when combining the genetic effects of these three loci (P for interaction = 4.40 × 10−8), and significant interactions with education were also observed for axial length and myopia. Our study shows that low level of education may attenuate the effect of risk alleles on myopia. These findings further underline the role of gene–environment interactions in the pathophysiology of myopia. PMID:24014484

Refractive Error in a Sample of Black High School Children in South Africa.

PubMed

Wajuihian, Samuel Otabor; Hansraj, Rekha

2017-12-01

This study focused on a cohort that has not been studied and who currently have limited access to eye care services. The findings, while improving the understanding of the distribution of refractive errors, also enabled identification of children requiring intervention and provided a guide for future resource allocation. The aim of conducting the study was to determine the prevalence and distribution of refractive error and its association with gender, age, and school grade level. Using a multistage random cluster sampling, 1586 children, 632 males (40%) and 954 females (60%), were selected. Their ages ranged between 13 and 18 years with a mean of 15.81 ± 1.56 years. The visual functions evaluated included visual acuity using the logarithm of minimum angle of resolution chart and refractive error measured using the autorefractor and then refined subjectively. Axis astigmatism was presented in the vector method where positive values of J0 indicated with-the-rule astigmatism, negative values indicated against-the-rule astigmatism, whereas J45 represented oblique astigmatism. Overall, patients were myopic with a mean spherical power for right eye of -0.02 ± 0.47; mean astigmatic cylinder power was -0.09 ± 0.27 with mainly with-the-rule astigmatism (J0 = 0.01 ± 0.11). The prevalence estimates were as follows: myopia (at least -0.50) 7% (95% confidence interval [CI], 6 to 9%), hyperopia (at least 0.5) 5% (95% CI, 4 to 6%), astigmatism (at least -0.75 cylinder) 3% (95% CI, 2 to 4%), and anisometropia 3% (95% CI, 2 to 4%). There was no significant association between refractive error and any of the categories (gender, age, and grade levels). The prevalence of refractive error in the sample of high school children was relatively low. Myopia was the most prevalent, and findings on its association with age suggest that the prevalence of myopia may be stabilizing at late teenage years.

[Hyperopic Laser-in-situ-Keratomileusis after trifocal intraocular lens implantation : Aberration-free femto-Laser-in-situ-Keratomileusis treatment after implantation of a diffractive, multifocal, toric intraocular lens-case analysis].

PubMed

Hemkeppler, E; Böhm, M; Kohnen, T

2018-05-29

A 52-year-old highly myopic female patient was implanted with a multifocal, diffractive, toric intraocular lens because of the wish to be independent of eyeglasses. Despite high-quality, extensive preoperative examinations, a hyperopic refractive error remained postoperatively, which led to the patient's dissatisfaction. This error was treated with Laser-in-situ-Keratomileusis (LASIK). After corneal LASIK treatment and implantation of a diffractive toric multifocal intraocular lens the patient showed a good postoperative visual result without optical phenomena.

Relationship between refractive error and ocular biometrics in twin children: the Guangzhou Twin Eye Study.

PubMed

Wang, Decai; Liu, Bin; Huang, Shengsong; Huang, Wenyong; He, Mingguang

2014-09-01

A cross-sectional study was conducted to explore the relationship between refractive error and ocular biometrics in children from the Guangzhou twin eye study. Twin participants aged 7-15 years were selected from Guangzhou Twin Eye Study. Ocular examinations included visual acuity measurement, ocular motility evaluation, autorefraction under cycloplegia, and anterior segment, media, and fundus examination. Axial length (AL), anterior chamber depth (ACD), and corneal curvature radius were measured using partial coherence laser interferometry. A multivariate linear regression model was used for statistical analysis. Twin children from Guangzhou city showed a decreased spherical equivalent with age, whereas both AL and ACD were increased and corneal curvature radius remained unchanged. When adjusted by age and gender, the data from 77% of twins presenting with spherical equivalent changes indicated that these were caused by predictable variables (R2 = 0.77, P < 0.001). Primary factors affecting children's refraction included axial length (β = -0.97,P < 0.001), ACD (β = 0.33, P < 0.001), and curvature radius (β = 2.10, P < 0.001). Girls had a higher tendency for myopic status than did boys (β = -0.26, P < 0.001). Age exerted no effect upon the changes in refraction (β = -0.01, P = 0.25). Refraction is correlated with ocular biometrics. Refractive status is largely determined by axial length as the major factor.

High myopia in Greater Beijing School Children in 2016.

PubMed

Guo, Yin; Duan, Jia Li; Liu, Li Juan; Sun, Ying; Tang, Ping; Lv, Yan Yun; Xu, Liang; Jonas, Jost B

2017-01-01

To assess prevalence and associated factors of myopia and high myopia in schoolchildren in Greater Beijing. The school-based, cross-sectional Greater Beijing School Children Myopia study was carried out in the year 2016 in 54 schools randomly selected from 15 districts in Beijing. Non-cycloplegic auto-refractometry of the right eyes was performed. The study included 35,745 (99.4%) out of 35,968 eligible pupils with a mean age of 12.6±3.4 years (range 6-18 years). Prevalence of myopia defined as myopic refractive error of ≥-0.50 diopters (D),≥-1D,≥-6D,≥-8D and ≥-10D was 70.9%(95% confidence intervals (CI):70.5,71.4), 60.9% (95%CI:60.4,61.4), 8.6%(95%CI:8.4,8.9), 2.2%(95%CI:2.0,2.4), and 0.3% (95%CI:0.3,0.4), respectively. The frequency of high myopia (≥-6D, ≥-8D, ≥-10D) increased from 1.5% (95%CI:1.0,2.0), 0.4% (95%CI:0.1,0.6) and 0.1% (95%CI:0.00,0.02), respectively in 10-year-olds to 19.4% (95%CI:17.3,21.6), 5.2% (95%CI:4.0,6.4) and 0.9% (95%CI:0.4,1.5), respectively, in 18-year-olds. Mean refractive error in the 18-year-olds was -3.74±2.56D (median:-3.63D;range:-19.6D to + 6.25D). Higher prevalence of high myopia (≥-6D and ≥-8D) was correlated (all P<0.001) with older age (OR:1.18, and 1.15, respectively), female gender (OR: 1.44 and 1.40, respectively), higher body mass index (OR: 1.02 and 1.03, respectively), taller body height (OR: 1.03 and 1.02, respectively), urban region of habitation (OR: 1.26 and 1.33, respectively) and higher school type (OR:1.57 and 2.22, respectively). Prevalence of severe high myopia (≥-10D) was associated only with older age (P<0.001; OR: 1.44; 95%CI: 1.31, 1.59) but not with any education-related parameter such as higher school type (P = 0.48), urban region of habitation (P = 0.07) or female gender (P = 0.37). In this most recent survey, prevalence of high myopia (≥-6D:19.4%;≥-8D:5.2%;≥-10D:0.9%) in 18-year-old school children was higher than in previous surveys from mainland China. In contrast to minor high myopia and moderate high myopia (defined as myopic refractive error of <-10D), severe high myopia (myopic refractive error ≥-10D) was not strongly correlated with educational parameters.

Influence of internal optical astigmatism on the correction of myopic astigmatism by LASIK.

PubMed

Qian, Yi-Shan; Huang, Jia; Liu, Rui; Chu, Ren-Yuan; Xu, Ye; Zhou, Xing-Tao; Hoffman, Matthew R

2011-12-01

To investigate the influence of the origin of astigmatism on the correction of myopic astigmatism by LASIK. A retrospective study was conducted of the records of 192 patients (192 eyes) undergoing LASIK for correction of myopia and myopic astigmatism from January to September 2010. Ocular residual astigmatism (ORA) and lenticular astigmatism (LA) were determined by vector analysis using objective refraction and Pentacam (Oculus Optikgeräte GmbH) imaging of both corneal surfaces. Patients were divided into two groups according to ORA (high ORA group: ORA/preoperative refractive astigmatism >1; normal ORA group: ORA/preoperative refractive astigmatism ≤ 1) and LA (high LA group: LA/preoperative refractive astigmatism >1; normal LA group: LA/preoperative refractive astigmatism ≤ 1). Procedural efficacy was compared between those eyes with and without a significant amount of internal optical astigmatism using index of success. Mean preoperative vectors for the astigmatism of the anterior cornea, posterior cornea, and lens were -1.33 × 3.0°, -0.33 × 95.3°, and -0.27 × 103.3°, respectively. Mean indices of success in the high and low ORA groups were 1.75 and 0.59, respectively (t=7.81, P<.001). Mean indices of success in the high and low LA groups were 2.07 and 0.70, respectively (t=12.36, P<.001). The higher indices of success in the high ORA and high LA groups suggest a lower efficacy of LASIK in treating astigmatism primarily located intraocularly. Myopic LASIK is less effective in correcting astigmatism when astigmatism is mainly located at the internal optics. Topography and refractive value should be incorporated in the treatment of patients when a significant amount of internal optical astigmatism is detected preoperatively.

Photorefractive keratectomy at 193 nm using an erodible mask

NASA Astrophysics Data System (ADS)

Gordon, Michael; Brint, Stephen F.; Durrie, Daniel S.; Seiler, Theo; Friedman, Marc D.; Johnsson, N. M. F.; King, Michael C.; Muller, David F.

1992-08-01

Clinical experience with more than ten thousand sighted eyes has demonstrated great promise for correcting myopia with photorefractive keratectomy (PRK). Previously reported techniques have incorporated computer-controlled irises, diaphragms, and apertures to regulate the desired distribution of 193 nm radiation onto the eye. This paper reports on an entirely new approach for performing PRK which utilizes an erodible mask to control the shape transfer process. Compared to the more traditional techniques, the erodible mask offers promise of correcting a broad range of refractive errors. In this paper the erodible mask and associated hardware are described in detail. We describe the shape transfer experiments used to predict the functional relationship between the desired refractive correction and the mask shape. We report on early clinical results from five patients with myopic astigmatism. We conclude that the early shape transfer experiments overestimated the spherical component of the correction by 1.25 diopters and underestimated the cylindrical component by approximately 0.85 diopters. The data suggest there may be biological effects which evoke different healing responses when myopic PRK corrections are performed with and without astigmatism. Clinical trials are proceeding with the mask shapes adjusted for these observations.

Corneal power evaluation after myopic corneal refractive surgery using artificial neural networks.

PubMed

Koprowski, Robert; Lanza, Michele; Irregolare, Carlo

2016-11-15

Efficacy and high availability of surgery techniques for refractive defect correction increase the number of patients who undergo to this type of surgery. Regardless of that, with increasing age, more and more patients must undergo cataract surgery. Accurate evaluation of corneal power is an extremely important element affecting the precision of intraocular lens (IOL) power calculation and errors in this procedure could affect quality of life of patients and satisfaction with the service provided. The available device able to measure corneal power have been tested to be not reliable after myopic refractive surgery. Artificial neural networks with error backpropagation and one hidden layer were proposed for corneal power prediction. The article analysed the features acquired from the Pentacam HR tomograph, which was necessary to measure the corneal power. Additionally, several billion iterations of artificial neural networks were conducted for several hundred simulations of different network configurations and different features derived from the Pentacam HR. The analysis was performed on a PC with Intel ® Xeon ® X5680 3.33 GHz CPU in Matlab ® Version 7.11.0.584 (R2010b) with Signal Processing Toolbox Version 7.1 (R2010b), Neural Network Toolbox 7.0 (R2010b) and Statistics Toolbox (R2010b). A total corneal power prediction error was obtained for 172 patients (113 patients forming the training set and 59 patients in the test set) with an average age of 32 ± 9.4 years, including 67% of men. The error was at an average level of 0.16 ± 0.14 diopters and its maximum value did not exceed 0.75 dioptres. The Pentacam parameters (measurement results) providing the above result are tangential anterial/posterior. The corneal net power and equivalent k-reading power. The analysis time for a single patient (a single eye) did not exceed 0.1 s, whereas the time of network training was about 3 s for 1000 iterations (the number of neurons in the hidden layer was 400).

Cycloplegic autorefraction in young adults: is it mandatory?

PubMed

Mimouni, Michael; Zoller, Lilach; Horowitz, Josefa; Wygnanski-Jaffe, Tamara; Morad, Yair; Mezer, Eedy

2016-02-01

The precise correction of refractive error is especially important in young adults. It is unclear whether cycloplegic refraction is necessary in this age group. The purpose of this study was to compare the non-cycloplegic and cycloplegic spherical equivalent (SE) refractive error measured in young adults. This was a prospective study of 1400 eyes (n = 700) of enlisted soldiers aged 18 to 21 years who were consecutively evaluated in an outpatient army ophthalmology clinic. One drop of cyclopentolate 1 % was installed twice 10 min apart, and cycloplegic refraction was performed in both eyes 40 min later using an auto-refractor. The difference between non-cycloplegic and cycloplegic refractive measurements was analyzed. The mean difference in SE between non-cycloplegic and cycloplegic measurements was 0.68 ± 0.83 D (95 % CI, 0.64-0.72). Significantly greater differences were observed in hypermetropes than myopes (1.30 ± 0.90 D versus 0.46 ± 0.68 D, p < 0.001). Moderate hypermetropes (2 to 5 D) demonstrated significantly greater refractive error than mild (0.5 to 2 D) or severe (>5 D) hypermetropes (1.71 ± 1.18 D versus 1.19 ± 0.74 D and 1.16 ± 1.08 D respectively, p < 0.001). Young hypermetropic adults possessed +1 to +2 D of latent hypermetropia. In contrast, young myopic adults revealed pseudomyopia of -0.5 D. Cycloplegic refraction should be performed in young hypermetropic adults complaining of various signs of asthenopia.

Peripheral refraction and retinal contour in stable and progressive myopia.

PubMed

Faria-Ribeiro, Miguel; Queirós, António; Lopes-Ferreira, Daniela; Jorge, Jorge; González-Méijome, José Manuel

2013-01-01

To compare the patterns of relative peripheral astigmatic refraction (tangential and sagittal power errors) and eccentric eye length between progressing and stable young-adult myopes. Sixty-two right eyes of 62 white patients participated in the study, of which 30 were nonprogressing myopes (NP group) for the last 2 years and 32 were progressing myopes (P group). Groups were matched for mean spherical refraction, axial length, and age. Peripheral refraction and eye length were measured along the horizontal meridian up to 35 and 30 degrees of eccentricity, respectively. There were statistically significant differences between groups (p < 0.001) in the nasal retina for the astigmatic components of peripheral refraction. The P group presented a hyperopic relative sagittal focus at 35 degrees in the nasal retina of +1.00 ± 0.83 diopters, as per comparison with a myopic relative sagittal focus of -0.10 ± 0.98 diopters observed in the NP group (p < 0.001). Retinal contour in the P group had a steeper shape in the nasal region than that in the NP group (t test, p = 0.001). An inverse correlation was found (r = -0.775; p < 0.001) between retinal contour and peripheral refraction. Thus, steeper retinas presented a more hyperopic trend in the periphery. Stable and progressing myopes of matched age, axial length, and central refraction showed significantly different characteristics in their peripheral retinal shape and astigmatic components of tangential and sagittal power errors. The present findings may help explain the mechanisms that regulate ocular growth in humans.

One-year visual outcome of small incision lenticule extraction (SMILE) surgery in high myopic eyes: retrospective cohort study

PubMed Central

Wu, Wenjing; Wang, Yan; Zhang, Hui; Zhang, Jiamei; Li, Hua; Dou, Rui

2016-01-01

Objective To determine whether the long-term visual outcome of small incision lenticule extraction (SMILE) surgery is consistent with the short-term results in high myopic eyes. Design Retrospective cohort study; data collected from 8 August 2011 to 31 August 2015. Setting Single refractive surgery centre. Participants A total of 156 eyes were studied: 65 eyes of 39 subjects (22 female/17 male) in the high myopic group (manifest refraction spherical equivalent (MRSE) ≥−6.0 D), and 91 eyes of 54 subjects (29 female/25 male) in the control group (MRSE <−6.0 D). The inclusion criteria were subjects who had follow-ups after 1 day, 1 week, 1 month, 3, 6 months and 1 year with the manifest refraction, uncorrected and corrected distance visual acuity (UDVA/CDVA). There were no statistically significant differences between the two groups in the subjects' gender, age, or cylindrical dioptre, preoperatively (p=0.835, p=0.055, p=0.341, respectively). Primary and secondary outcome measures UDVA, refractive stability, safety index (postoperative CDVA/preoperative CDVA), and predictability (the percentage of eyes within ±0.50 D). Results In both groups, the 1-year UDVA and safety index were significantly better than results at 1 day (high myopic group: p=0.035, p<0.001; control group: p<0.016, p<0.001); the 1-year predictability showed no significant difference with the short-term results (p=1.00 in both groups). In the high myopic eyes, the 1-year MRSE was significantly worse than the short-term result (p=0.048). To correct it, the added magnitude (D) for the high myopic eyes may equal 0.13×Attempted SE (D)−0.66 D. However, the postoperative MRSE showed no differences from 1 day to 1 year (p=0.612) in the control group. Conclusions The 1-year visual outcomes were better than the short-term results after the SMILE surgery on the visual acuity and safety. However, the high myopic eyes suffered a significant regression at 1 year, which may be corrected by adding additional magnitude to the SE for high myopic eyes. PMID:27655258

[Refractive Surgery in Children with Myopic Anisometropia and Amblyopia in Comparison with Conventional Treatment by Contact Lenses].

PubMed

Autrata, R; Krejčířová, I; Griščíková, L; Doležel, Z

2016-01-01

Our study evaluated the visual and refractive results of LASEK and anterior chamber phakic intraocular lens (pIOL) implantation performed for high myopic anisometropia with amblyopia and contact lens intolerance in children compared with conventional treatment by contact lenses.Fourty-three patients (Group A) aged 3 to 7 years (mean, 5,6 years) with high myopic anisometropia and amblyopia had performed multizonal LASEK (27 eyes) or pIOL Verisyse implantation (16 eyes) on the more myopic eye in general anesthesia. Surgery was followed by patching of the dominant eye. Postoperative visual and refractive outcomes were analyzed and all children had minimally two years follow-up after procedure. Refractive surgical data were reported in standard format to describe safety, efficacy, predictability and stability of the procedure. This Group A of 43 children was compared with control Group B of 37 children (mean age 5,4 years), in whom myopic anisometropia and amblyopia were treated conventionally by contact lenses (CL) and patching of the dominant eye. Visual acuity (VA) and binocular vision (BV) outcome were analyzed and compared in both groups.The mean preoperative spherical equivalent (SE) cycloplegic refraction in Group A was - 9,45 ± 2,47 diopters (D) (range -6.0 to -18.25 D) and the mean postoperative SE -1,48 ± 1,13 D (range + 0,75 to - 2,25 D). The mean preop. decimal uncorrected visual acuity (UCVA) 0,023 ± 0,017 increased to 0,46 ± 0,18. The mean preop.decimal best-corrected visual acuity (BCVA) in Group A was 0,28 ± 0.22 and changed to 0,78± 0,19 by 2 years after surgery. The mean BCVA in Group B was 0,23 ± 0,19, at start of CL correction and amblyopia therapy, and improved to 0,42 ± 0,15 after two years. The mean BCVA at final examination was significantly better in Group A (P < 0,05). Binocular vision improvement expressed by the proportions of subjects gained fusion and stereopsis, was overall better in Group A (81 %) than in Group B (33 %), (P < 0,05). There were no complications after surgery.Refractive surgery in children, multizonal LASEK and pIOL Verisyse implantation, are effective and safe methods for correction of high myopic anisometropia, and has an important role in the treatment of amblyopia in children when contact lens intolerance. Visual acuity and binocular vision outcomes were better in children who received permanent surgical correction of anisometropia, than in children conventionally treated by contact lenses. myopic anisometropia, amblyopia, children, laser subepithelial keratomileusis (LASEK), anterior chamber phakic intraocular lenses (AC pIOL), binocular vision.

Spectacle-wear compliance in school children in Concepción Chile.

PubMed

von-Bischhoffshausen, Fernando Barria; Muñoz, Beatriz; Riquelme, Ana; Ormeño, Maria Jose; Silva, Juan Carlos

2014-12-01

Although international policies promote programs for correction of refractive errors in school children, recent studies report low compliance with respect to spectacle wear. Our aim was to assess spectacle-wear compliance and identify associated visual factors among children participating in Chile's school spectacle provision program. A total of 270 school children were prescribed spectacles and monitored after 1 year. Visual acuity, refractive error, reasons for not wearing spectacles, and self-reported visual function were assessed. Compliance is reported as the proportion of children wearing spectacles at the 1-year visit. Factors associated with compliance and reasons for not wearing spectacles were examined using contingency table analyses. Logistic models were constructed to assess independently associated factors. Only 204 children (76%) participated in the 1-year follow-up. Mean age was 10 years (range 4-19 years); 58% were girls, 42% boys. Overall compliance was 58%. Spectacle use was independently associated with age and refractive error. Older children were less likely to be compliant (odds ratio, OR, 0.8, 95% confidence interval, CI, 0.76-0.92/year of increasing age). Compared with children with refractions of -0.75 to +0.75 diopters, both myopic and hyperopic children were more compliant (OR 4.93, 95% CI 2.28-10.67 and OR 2.37, 95% CI 1.06-5.31, respectively). Primary reasons for not wearing spectacles included breakage/loss in younger children, and disliking the appearance in teenagers. We found greater compliance in spectacle wear than that reported in most published studies. Guidelines for provision of children's spectacles should consider excluding children with mild refractive error and improving spectacle quality and appearance.

Comparative Efficacy of the New Optical Biometer on Intraocular Lens Power Calculation (AL-Scan versus IOLMaster).

PubMed

Ha, Ahnul; Wee, Won Ryang; Kim, Mee Kum

2018-05-15

To evaluate the agreement in axial length (AL), keratometry, and anterior chamber depth measurements between AL-Scan and IOLMaster biometers and to compare the efficacy of the AL-Scan on intraocular lens (IOL) power calculations and refractive outcomes with those obtained by the IOLMaster. Medical records of 48 eyes from 48 patients who underwent uneventful phacoemulsification and IOL insertion were retrospectively reviewed. One of the two types of monofocal aspheric IOLs were implanted (Tecnis ZCB00 [Tecnis, n = 34] or CT Asphina 509M [Asphina, n = 14]). Two different partial coherence interferometers measured and compared AL, keratometry (2.4 mm), anterior chamber depth, and IOL power calculations with SRK/T, Hoffer Q, Holladay2, and Haigis formulas. The difference between expected and actual final refractive error was compared as refractive mean error (ME), refractive mean absolute error (MAE), and median absolute error (MedAE). AL measured by the AL-Scan was shorter than that measured by the IOLMaster (p = 0.029). The IOL power of Tecnis did not differ between the four formulas; however, the Asphina measurement calculated using Hoffer Q for the AL-Scan was lower (0.28 diopters, p = 0.015) than that calculated by the IOLMaster. There were no statistically significant differences between the calculations by MAE and MedAE for the four formulas in either IOL. In SRK/T, ME in Tecnis-inserted eyes measured by AL-Scan showed a tendency toward myopia (p = 0.032). Measurement by AL-Scan provides reliable biometry data and power calculations compared to the IOLMaster; however, refractive outcomes of Tecnis-inserted eyes by AL-Scan calculated using SRK/T can show a slight myopic tendency. © 2018 The Korean Ophthalmological Society.

Effect of Orthokeratology on myopia progression: twelve-year results of a retrospective cohort study.

PubMed

Lee, Yueh-Chang; Wang, Jen-Hung; Chiu, Cheng-Jen

2017-12-08

Several studies reported the efficacy of orthokeratology for myopia control. Somehow, there is limited publication with follow-up longer than 3 years. This study aims to research whether overnight orthokeratology influences the progression rate of the manifest refractive error of myopic children in a longer follow-up period (up to 12 years). And if changes in progression rate are found, to investigate the relationship between refractive changes and different baseline factors, including refraction error, wearing age and lens replacement frequency. In addition, this study collects long-term safety profile of overnight orthokeratology. This is a retrospective study of sixty-six school-age children who received overnight orthokeratology correction between January 1998 and December 2013. Thirty-six subjects whose baseline age and refractive error matched with those in the orthokeratology group were selected to form control group. These subjects were followed up at least for 12 months. Manifest refractions, cycloplegic refractions, uncorrected and best-corrected visual acuities, power vector of astigmatism, corneal curvature, and lens replacement frequency were obtained for analysis. Data of 203 eyes were derived from 66 orthokeratology subjects (31 males and 35 females) and 36 control subjects (22 males and 14 females) enrolled in this study. Their wearing ages ranged from 7 years to 16 years (mean ± SE, 11.72 ± 0.18 years). The follow-up time ranged from 1 year to 13 years (mean ± SE, 6.32 ± 0.15 years). At baseline, their myopia ranged from -0.5 D to -8.0 D (mean ± SE, -3.70 ± 0.12 D), and astigmatism ranged from 0 D to -3.0 D (mean ± SE, -0.55 ± 0.05 D). Comparing with control group, orthokeratology group had a significantly (p < 0.001) lower trend of refractive error change during the follow-up periods. According to the analysis results of GEE model, greater power of astigmatism was found to be associated with increased change of refractive error during follow-up years. Overnight orthokeratology was effective in slowing myopia progression over a twelve-year follow-up period and demonstrated a clinically acceptable safety profile. Initial higher astigmatism power was found to be associated with increased change of refractive error during follow-up years.

Unbiased Estimation of Refractive State of Aberrated Eyes

PubMed Central

Martin, Jesson; Vasudevan, Balamurali; Himebaugh, Nikole; Bradley, Arthur; Thibos, Larry

2011-01-01

To identify unbiased methods for estimating the target vergence required to maximize visual acuity based on wavefront aberration measurements. Experiments were designed to minimize the impact of confounding factors that have hampered previous research. Objective wavefront refractions and subjective acuity refractions were obtained for the same monochromatic wavelength. Accommodation and pupil fluctuations were eliminated by cycloplegia. Unbiased subjective refractions that maximize visual acuity for high contrast letters were performed with a computer controlled forced choice staircase procedure, using 0.125 diopter steps of defocus. All experiments were performed for two pupil diameters (3mm and 6mm). As reported in the literature, subjective refractive error does not change appreciably when the pupil dilates. For 3 mm pupils most metrics yielded objective refractions that were about 0.1D more hyperopic than subjective acuity refractions. When pupil diameter increased to 6 mm, this bias changed in the myopic direction and the variability between metrics also increased. These inaccuracies were small compared to the precision of the measurements, which implies that most metrics provided unbiased estimates of refractive state for medium and large pupils. A variety of image quality metrics may be used to determine ocular refractive state for monochromatic (635nm) light, thereby achieving accurate results without the need for empirical correction factors. PMID:21777601

Perspectives of using the 223-nm wavelength of the KrCl excimer laser for refractive surgery and for the treatment of some eye diseases

NASA Astrophysics Data System (ADS)

Bagayev, Sergei N.; Chernikh, Valery V.; Razhev, Alexander M.; Zhupikov, Andrey A.

2000-06-01

The new surgical UV ophthalmic laser system Medilex based on the KrCl (223 nm) excimer laser for refractive surgery was created. The comparative analysis of using the UV ophthalmic laser systems Medilex based on the ArF (193 nm) and the KrCl (223 nm) excimer lasers for the correction of refractive errors was performed. The system with the radiation wavelength of 223 nanometer of the KrCl excimer laser for refractive surgery was shown to have several medical and technical advantages over the system with the traditionally used radiation wavelength of 193 nanometer of the ArF excimer laser. In addition the use of the wavelength of 223 nanometer extends functional features of the system, allowing to make not only standard for this type systems surgical and therapeutic procedures but also to treat such ocular diseases as the glaucoma and herpetic keratities. For the UV ophthalmic laser systems Medilex three variations of the beam delivery system including special rotating masks and different beam homogenize systems were developed. All created beam delivery systems are able to make the correction of myopia, hyperopia, astigmatism and myopic or hyperopic astigmatism and may be used for therapeutic procedures. The results of the initial treatments of refractive error corrections using the UV ophthalmic laser systems Medilex for both photorefractive keratectomy (PRK) and LASIK procedures are presented.

Complications after procedures of photorefractive keratectomy

NASA Astrophysics Data System (ADS)

Gierek-Ciaciura, Stanislawa

1998-10-01

Purpose: The aim of this study was to investigate the saveness of the PRK procedures. Material and method: 151 eyes after PRK for correction of myopia and 112 after PRK for correction of myopic astigmatism were examined. All PRK procedures have been performed with an excimer laser manufactured by Aesculap Meditec. Results: Haze, regression, decentration infection and overcorrection were found. Conclusions: The most often complication is regression. Corneal inflammation in the early postoperative period may cause the regression or haze. The greater corrected refractive error the greater haze degree. Haze decreases with time.

Small-incision lenticule extraction (SMILE): outcomes of 722 eyes treated for myopia and myopic astigmatism.

PubMed

Hansen, Rasmus Søgaard; Lyhne, Niels; Grauslund, Jakob; Vestergaard, Anders Højslet

2016-02-01

To study the outcomes of small-incision lenticule extraction (SMILE) for treatment of myopia and myopic astigmatism. Retrospective study of patients treated for myopia or myopic astigmatism with SMILE, using a VisuMax(®) femtosecond laser (Carl Zeiss Meditec, Jena, Germany), at the Department of Ophthalmology, Odense University Hospital, Odense, Denmark. Inclusion criteria were corrected distance visual acuity (CDVA) of 20/25 or better before surgery and no ocular conditions other than myopia up to -10.00 diopters (D) with astigmatism up to 3.00 D. Of the 729 treatments, 722 were included. The spherical equivalent (SE) refraction averaged -6.82 ± 1.66 diopters (D) before surgery. After 3 months, 88 % of eyes were within ±0.50 D of the intended refraction, whilst 98 % were within ±1.00 D. The mean difference between attempted and achieved SE refraction at 3 months after surgery was -0.06 ± 0.01 D (range: -1.25 to 1.25 D). In eyes with emmetropia as target refraction (n = 362), 63 % had uncorrected distance visual acuity (UDVA) of 20/25 or better 1 day after surgery, rising to 83 % at 3 months after surgery. The average gain in CDVA from before surgery to 3 months after surgery was 0.07 ± 0.03 (logMAR). However, 12 eyes (1.6 %) lost 2 or more lines of CDVA from before surgery to 3 months postoperatively. Simultaneous treatment of up to 3.00 D of astigmatism was not associated with less predictable refractive outcomes. In the short term, SMILE seemed predictable, efficient, and safe for treatment of myopia and myopic astigmatism.

Post-traumatic pseudomyopia.

PubMed

London, Richard; Wick, Bruce; Kirschen, David

2003-02-01

Many clinicians have noted that patients demonstrate a myopic refractive change following Traumatic Brain Injury (TBI). This apparent myopic shift disappears with cycloplegia, yet stubbornly reappears as soon as the pharmaceutical effect wears off. We propose that this shift is secondary to an irritative lesion that affects the parasympathetic innervation, resulting in ciliary body contracture. The dilemma for the clinician is whether to provide the immediate relief of clear distance vision by prescribing additional minus lenses, or to work toward attempting to re-establish the baseline refractive error. The natural history of post-traumatic pseudomyopia in our experience involves one of the following three courses: (1) a transient condition that will occasionally resolve; (2) the typical case, a recalcitrant condition that will resolve under cycloplegic intervention, but immediately return as the cycloplegic wears off; or (3) a less-common subgroup of patients who continue to show an increase in myopia over time. Our description of these cases demonstrates management strategies (including atropinization) to relax accommodative spasm, traditional vision therapy techniques aimed at loosening the accommodative system, and refractive corrections. Pseudomyopia is one of many ocular and behavioral sequelae following TBI. By understanding the natural course and potential management options for post-traumatic pseudomyopia, the clinician will be better prepared to deal with these challenging cases. Flexibility is required, since options that work with one patient may prove ineffective with another. Counseling the patient as to potential outcomes given the natural history of this condition helps establish more-realistic expectations by the patients being treated.

Quantitative evaluation of changes in eyeball shape in emmetropization and myopic changes based on elliptic fourier descriptors.

PubMed

Ishii, Kotaro; Iwata, Hiroyoshi; Oshika, Tetsuro

2011-11-04

To evaluate changes in eyeball shape in emmetropization and myopic changes using magnetic resonance imaging (MRI) and elliptic Fourier descriptors (EFDs). The subjects were 105 patients (age range, 1 month-19 years) who underwent head MRI. The refractive error was determined in 30 patients, and eyeball shape was expressed numerically by principal components analysis of standardized EFDs. In the first principal component (PC1; the oblate-to-prolate change), the proportion of variance/total variance in the development of the eyeball shape was 76%. In all subjects, PC1 showed a significant correlation with age (Pearson r = -0.314; P = 0.001), axial length (AL, r = -0.378; P < 0.001), width (r = -0.200, P = 0.0401), oblateness (r = 0.657, P < 0.001), and spherical equivalent refraction (SER, r = 0.438; P = 0.0146; n = 30). In the group containing patients aged 1 month to 6 years (n = 49), PC1 showed a significant correlation with age (r = -0.366; P = 0.0093). In the group containing patients aged 7 to 19 years (n = 56), PC1 showed a significant correlation with SER (r = 0.640; P = 0.0063). The main deformation pattern in the development of the eyeball shape from oblate to prolate was clarified by quantitative analysis based on EFDs. The results showed clear differences between age groups with regard to changes in the shape of the eyeball, the correlation between these changes, and refractive status changes.

The progression of myopia from its onset at age 8-12 to adulthood and the influence of heredity and external factors on myopic progression. A 23-year follow-up study.

PubMed

Pärssinen, Olavi; Kauppinen, Markku; Viljanen, Anne

2014-12-01

To examine myopic progression and factors connected with myopic progression. Myopic schoolchildren, with no previous spectacles, 119 boys and 121 girls, were recruited during 1983-1984 to a randomized 3-year clinical trial of bifocal treatment of myopia with a subsequent 20-year follow-up. Participants' mean age at Baseline was 10.9, ranging from 8.7 to 12.8 years. An ophthalmological examination was carried out annually for 3 years and twice thereafter at ca. 10-year intervals. Additional refraction values were received from prescriptions issued by different ophthalmologists and opticians. Altogether, 1915 refraction values were available. Reading distance and accommodation were measured at each control visit. Data on parents' myopia, daily time spent on reading and close work, outdoor activities and watching television were gathered with a structured questionnaire. Using bifocals (+1.75 add) or reading without glasses or accommodation stimulus during the 3-year period in childhood did not correlate with adulthood refraction. Short reading distance in childhood predicted higher adulthood myopia among females. The factors predicting faster myopic progression were parents' myopia and less time spent on sports and outdoor activities at childhood. Time spent on reading and close work in childhood was related to myopic progression during the first 3 years but did not predict adulthood myopia. Myopia throughout follow-up was higher among those who watched television <3 hr daily than those who spent more time watching television. Mean myopic progression 8 years after age 20-24 was -0.45 D ± 0.71 (SD), and in 45% of cases, progression was ≥0.5 D. In nearly half of the cases, myopia beginning at school continued to progress into adulthood. Higher adulthood myopia was mainly related to parents' myopia and less time spent on sports and outdoor activities in childhood. © 2014 Acta Ophthalmologica Scandinavica Foundation. Published by John Wiley & Sons Ltd.

Reversal of myopic anisometropic amblyopia with occlusion therapy in a 25 year old.

PubMed

Megbelayin, E; Ekpenyong, S M; Azunobi, J; Ejiro, G

2014-03-01

To report a reversal of myopic anisometropic amblyopia with occlusion therapy in a 25 year old. Case report. Eye clinic of a University Teaching Hospital in a metropolitan city. an index patient. Occlusion therapy. Post occlusion visual acuity. Presenting unaided visual acuity of right eye: 6/6, left eye: 4/60. Refraction result was: right eye: -0.50DS (6/6), left eye: -3.50DS (6/18). Following day time occlusion therapy of at least 6 hours for about 4 weeks, subjective refraction was: right eye: -0.5DS (6/5), left eye: -3.50DS (6/6(+3)). The remarkable improvement in vision at age 25 years of a patient with myopic anisometropic amblyopia shows that occlusion therapy might still be useful long after amblyogenic period.

Refractive accuracy with light-adjustable intraocular lenses.

PubMed

Villegas, Eloy A; Alcon, Encarna; Rubio, Elena; Marín, José M; Artal, Pablo

2014-07-01

To evaluate efficacy, predictability, and stability of refractive treatments using light-adjustable intraocular lenses (IOLs). University Hospital Virgen de la Arrixaca, Murcia, Spain. Prospective nonrandomized clinical trial. Eyes with a light-adjustable IOL (LAL) were treated with spatial intensity profiles to correct refractive errors. The effective changes in refraction in the light-adjustable IOL after every treatment were estimated by subtracting those in the whole eye and the cornea, which were measured with a Hartmann-Shack sensor and a corneal topographer, respectively. The refractive changes in the whole eye and light-adjustable IOL, manifest refraction, and visual acuity were obtained after every light treatment and at the 3-, 6-, and 12-month follow-ups. The study enrolled 53 eyes (49 patients). Each tested light spatial pattern (5 spherical; 3 astigmatic) produced a different refractive change (P<.01). The combination of 2 light adjustments induced a maximum change in spherical power of the light-adjustable IOL of between -1.98 diopters (D) and +2.30 D and in astigmatism of up to -2.68 D with axis errors below 9 degrees. Intersubject variability (standard deviation) ranged between 0.10 D and 0.40 D. The 2 required lock-in procedures induced a small myopic shift (range +0.01 to +0.57 D) that depended on previous adjustments. Light-adjustable IOL implantation achieved accurate refractive outcomes (around emmetropia) with good uncorrected distance visual acuity, which remained stable over time. Further refinements in nomograms and in the treatment's protocol would improve the predictability of refractive and visual outcomes with these IOLs. No author has a financial or proprietary interest in any material or method mentioned. Copyright © 2014 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.

Detection of posterior vortex veins in eyes with pathologic myopia by ultra-widefield indocyanine green angiography.

PubMed

Moriyama, Muka; Cao, Kejia; Ogata, Satoko; Ohno-Matsui, Kyoko

2017-09-01

To analyse the characteristics of posterior vortex veins detected in highly myopic eyes by wide-field indocyanine green angiography (ICGA). One hundred and fifty-eight consecutive patients (302 eyes) with high myopia (myopic refractive error >8.0 dioptres (D) or axial length ≥26.5 mm) were studied. Wide-field ICGA was performed with the Spectralis HRA module. Posterior vortex veins were found in 80 eyes (26%). The prevalence of posterior staphyloma was significantly higher in eyes in which posterior vortex vein was detected than in eyes without posterior vortex vein. The posterior vortex veins were classified into five types according to the site of exit from the eye; around the optic nerve in 28%, in the macular area in 17%, along the border of staphyloma in 6%, along the margin of macular atrophy or large peripapillary conus in 21%, and elsewhere in 28%. In one eye, two posterior vortex veins collected the choroidal venous blood from the entire fundus. Wide-field ICGA can analyse the characteristic features of choroidal blood outflow system through posterior vortex veins in highly myopic eyes. They may play an important role as routes of choroidal outflow in highly myopic eyes. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/.

Myopic Macular Retinoschisis in Teenagers: Clinical Characteristics and Spectral Domain Optical Coherence Tomography Findings

PubMed Central

Sun, Chuan-bin; You, Yong-sheng; Liu, Zhe; Zheng, Lin-yan; Chen, Pei-qing; Yao, Ke; Xue, An-quan

2016-01-01

To investigate the morphological characteristics of myopic macular retinoschisis (MRS) in teenagers with high myopia, six male (9 eyes) and 3 female (4 eyes) teenagers with typical MRS identified from chart review were evaluated. All cases underwent complete ophthalmic examinations including best corrected visual acuity (BCVA), indirect ophthalmoscopy, colour fundus photography, B-type ultrasonography, axial length measurement, and spectral-domain optical coherence tomography (SD-OCT). The average age was 17.8 ± 1.5 years, average refractive error was −17.04 ± 3.04D, average BCVA was 0.43 ± 0.61, and average axial length was 30.42 ± 1.71 mm. Myopic macular degenerative changes (MDC) by colour fundus photographs revealed Ohno-Matsui Category 1 in 4 eyes, and Category 2 in 9 eyes. Posterior staphyloma was found in 9 eyes. SD-OCT showed outer MRS in all 13 eyes, internal limiting membrane detachment in 7 eyes, vascular microfolds in 2 eyes, and inner MRS in 1 eye. No premacular structures such as macular epiretinal membrane or partially detached posterior hyaloids were found. Our results showed that MRS rarely occurred in highly myopic teenagers, and was not accompanied by premacular structures, severe MDC, or even obvious posterior staphyloma. This finding indicates that posterior scleral expansion is probably the main cause of MRS. PMID:27294332

Five-year change in refraction and its ocular components in the 40- to 64-year-old population of the Shahroud eye cohort study.

PubMed

Hashemi, Hassan; Khabazkhoob, Mehdi; Iribarren, Rafael; Emamian, Mohammad Hassan; Fotouhi, Akbar

2016-11-01

To assess 5-year refractive changes and their related factors in the 40- to 64-year-old population of Shahroud, Iran. Prospective cohort study. Of the 5190 participants of Phase I, 4737 participated in Phase II (response rate = 91.3%). Participants were tested by refraction, visual acuity, slit-lamp biomicroscopy, ophthalmoscopy and biometry. Myopia was defined as a spherical equivalent more negative than -0.5 dioptre (D) and hyperopia as a spherical equivalent more positive than +0.5 D. Mean 5-year change in spherical equivalent refraction. The mean 5-year change in spherical equivalent refraction was +0.24 D (95% CI: +0.22 to +0.25). After 5 years, 4.77% (95% CI: 4.08 to 5.46) of subjects developed at least 0.5 D of myopia and 22.27% (95% CI: 20.97 to 23.57) developed at least 0.5 D of hyperopia. Five-year changes in refraction included a hyperopic shift in all age groups. The greatest hyperopic shift was seen in middle-aged women. The greatest loss of lens power was observed in hyperopic women and the least in myopic men. Nuclear cataract was associated with a myopic shift in refraction. The axial length and the corneal power had very small changes during this period. Myopes showed the greatest increase in axial length. Corneal power increased by a very small amount in all refractive groups. The most important biometric index related to hyperopic shifts, which were greater in magnitude in women, was loss of lens power, whereas nuclear cataract was associated with myopic shifts. © 2016 Royal Australian and New Zealand College of Ophthalmologists.

Outcomes of presbyopia-correcting intraocular lenses after laser in situ keratomileusis.

PubMed

Chow, Sharon S W; Chan, Tommy C Y; Ng, Alex L K; Kwok, Alvin K H

2018-03-28

Laser in situ keratomileusis (LASIK) is the most common refractive surgery in young patients, which aims at providing a clear distance vision without the use of spectacles. With time, these patients develop symptomatic cataract, which affects activities of daily living, and to improve visual acuity, intraocular lens (IOL) implantation can be considered. In post-myopic LASIK patients, to allow continuation of spectacle independence, the implantation of presbyopia-correcting IOLs is a suitable option. The purpose of this retrospective case series is to report the visual outcome and quality in post-myopic LASIK eyes after the implantation of AT LISA tri839MP IOL. Twenty eyes of 13 patients with history of myopic LASIK within 20 years underwent phacoemulsification by one single surgeon. All eyes were implanted with AT LISA tri839PMP IOL, and their outcomes were evaluated at 6 months postoperation. The mean postoperative uncorrected distance visual acuity (VA) is 0.28 ± 0.29, while the corrected distance VA is 0.06 ± 0.14. The mean postoperative uncorrected near VA is 0.02 ± 0.05, while the corrected near VA is 0.01 ± 0.02. The mean postoperative manifest refraction spherical equivalent (SE) is - 0.92 ± 0.76D. There is a statistically significant difference between the preoperative and postoperative refraction (p = 0.02), which shows a postoperative myopic shift. There is also a statistically significant difference between the mean targeted SE and postoperative manifest refraction SE (p = 0.00). Only one out of 20 eyes (5%) reported halo and glare symptoms. Ten out of 20 eyes (50%) are able to achieve spectacles independence. In conclusion, in post-myopic LASIK eyes, AT LISA tri839MP provides a good visual outcome at both near and distance, but is more predictable at near than at distance. There is a myopic shift in the postoperative SE. Visual quality is satisfactory and has not been exacerbated. Most patients can remain to be spectacles free at all distances.

Prevalence and Risk Factors for Refractive Errors: Korean National Health and Nutrition Examination Survey 2008-2011

PubMed Central

Kim, Eun Chul; Morgan, Ian G.; Kakizaki, Hirohiko; Kang, Seungbum; Jee, Donghyun

2013-01-01

Purpose To examine the prevalence and risk factors of refractive errors in a representative Korean population aged 20 years old or older. Methods A total of 23,392 people aged 20+ years were selected for the Korean National Health and Nutrition Survey 2008–2011, using stratified, multistage, clustered sampling. Refractive error was measured by autorefraction without cycloplegia, and interviews were performed regarding associated risk factors including gender, age, height, education level, parent's education level, economic status, light exposure time, and current smoking history. Results Of 23,392 participants, refractive errors were examined in 22,562 persons, including 21,356 subjects with phakic eyes. The overall prevalences of myopia (< -0.5 D), high myopia (< -6.0 D), and hyperopia (> 0.5 D) were 48.1% (95% confidence interval [CI], 47.4–48.8), 4.0% (CI, 3.7–4.3), and 24.2% (CI, 23.6–24.8), respectively. The prevalence of myopia sharply decreased from 78.9% (CI, 77.4–80.4) in 20–29 year olds to 16.1% (CI, 14.9–17.3) in 60–69 year olds. In multivariable logistic regression analyses restricted to subjects aged 40+ years, myopia was associated with younger age (odds ratio [OR], 0.94; 95% Confidence Interval [CI], 0.93-0.94, p < 0.001), education level of university or higher (OR, 2.31; CI, 1.97–2.71, p < 0.001), and shorter sunlight exposure time (OR, 0.84; CI, 0.76–0.93, p = 0.002). Conclusions This study provides the first representative population-based data on refractive error for Korean adults. The prevalence of myopia in Korean adults in 40+ years (34.7%) was comparable to that in other Asian countries. These results show that the younger generations in Korea are much more myopic than previous generations, and that important factors associated with this increase are increased education levels and reduced sunlight exposures. PMID:24224049

Prevalence and risk factors for refractive errors: Korean National Health and Nutrition Examination Survey 2008-2011.

PubMed

Kim, Eun Chul; Morgan, Ian G; Kakizaki, Hirohiko; Kang, Seungbum; Jee, Donghyun

2013-01-01

To examine the prevalence and risk factors of refractive errors in a representative Korean population aged 20 years old or older. A total of 23,392 people aged 20+ years were selected for the Korean National Health and Nutrition Survey 2008-2011, using stratified, multistage, clustered sampling. Refractive error was measured by autorefraction without cycloplegia, and interviews were performed regarding associated risk factors including gender, age, height, education level, parent's education level, economic status, light exposure time, and current smoking history. Of 23,392 participants, refractive errors were examined in 22,562 persons, including 21,356 subjects with phakic eyes. The overall prevalences of myopia (< -0.5 D), high myopia (< -6.0 D), and hyperopia (> 0.5 D) were 48.1% (95% confidence interval [CI], 47.4-48.8), 4.0% (CI, 3.7-4.3), and 24.2% (CI, 23.6-24.8), respectively. The prevalence of myopia sharply decreased from 78.9% (CI, 77.4-80.4) in 20-29 year olds to 16.1% (CI, 14.9-17.3) in 60-69 year olds. In multivariable logistic regression analyses restricted to subjects aged 40+ years, myopia was associated with younger age (odds ratio [OR], 0.94; 95% Confidence Interval [CI], 0.93-0.94, p < 0.001), education level of university or higher (OR, 2.31; CI, 1.97-2.71, p < 0.001), and shorter sunlight exposure time (OR, 0.84; CI, 0.76-0.93, p = 0.002). This study provides the first representative population-based data on refractive error for Korean adults. The prevalence of myopia in Korean adults in 40+ years (34.7%) was comparable to that in other Asian countries. These results show that the younger generations in Korea are much more myopic than previous generations, and that important factors associated with this increase are increased education levels and reduced sunlight exposures.

Prevalence of habitual refractive errors and anisometropia among Dutch schoolchildren and hospital employees.

PubMed

Hendricks, Theo J W; de Brabander, John; Vankan-Hendricks, Marlou H P; van der Horst, Frans G; Hendrikse, Fred; Knottnerus, J Andre

2009-08-01

Refractive error (RE) is suggested to cause not only visual impairment, but also functional problems such as aspecific health complaints and lower levels of school achievement. During the last few decades the prevalence of myopia has increased worldwide, especially in Asia. We investigated the prevalence of habitual RE and anisometropia in a Dutch population of children and employees. In a cross-sectional study, RE in both eyes of 520 children (aged 11-13 years) and 444 hospital employees (aged 17-60 years) were measured using an autorefractometer. The measurements were performed without using a cycloplegium. Pearson's correlation coefficient (r) was used to analyse correlations between the right and left eyes. Chi-square tests were used to test the differences between subgroups according to gender and age. In schoolchildren 28% of right eyes were myopic (> 0.50 D) and 8% hyperopic (> 0.50 D). Pearson's r between right and left eyes for spherical equivalent power (SEP) was 0.93. The mean cylinder deviation in right eyes was 0.26 D (range 0.00-4.50 D). Anisometropia > 1.00 D was present in 4.6% of children; 22% of children were not optimally (> 0.50 D) corrected. In hospital employees, 30% of right eyes were myopic (> 0.50 D) and 10% hyperopic (> 0.50 D). Pearson's r between right and left eyes for SEP was 0.53. The mean cylinder deviation in right eyes was 0.35 D (range 0.00-5.75 D). Anisometropia > 1.00 D was present in 25% of employees. Anisometropia was more frequently present in employees aged 40-60 years, than in those aged 17-39 years (30% versus 18%; p = 0.02, Cramer's V = 0.15). Refractive errors are common in children aged 11-13 years and in working adults aged 17-60 years. Distributions of sphere and cylinder deviations are similar for Dutch schoolchildren and hospital employees. Surprisingly, anisometropia proved to be more prevalent with age. In children many eyes are not optimally corrected. Increased attention should be paid to uncorrected and miscorrected REs.

Safety and efficacy of wavefront-guided myopic laser in situ keratomileusis using a new wavefront sensor technology: first 100 cases.

PubMed

Smadja, David; Santhiago, Marcony R; Tellouck, Joy; De Castro, Tania; Lecomte, Fanny; Mello, Glauco R; Touboul, David

2015-08-01

To evaluate the safety and efficacy of wavefront-guided laser in situ keratomileusis (LASIK) for the correction of low to high myopia and myopic astigmatism using data derived from a new-generation Hartmann-Shack aberrometer. Refractive Surgery Unit, Bordeaux Hospital University, France. Retrospective case series. This retrospective study analyzed the initial group of eyes treated with wavefront-guided LASIK for myopia and myopic astigmatism using the Visx S4IR excimer laser and wavefront data derived from a new Hartmann-Shack aberrometer (iDesign Advanced Wavescan aberrometer). Refractive (refraction and refractive accuracy) and visual outcomes (uncorrected [UDVA] and corrected [CDVA] distance visual acuities) were recorded 3 months postoperatively. The study included 100 eyes of 50 consecutively treated patients. The mean decimal UDVA improved from 0.1 ± 0.1 (SD) preoperatively to 1.1 ± 0.15 postoperatively (P < .01). A monocular UDVA of 20/16, 20/20, and 20/25 were achieved in 76.6%, 94.4%, and 96.6% of eyes, respectively. The postoperative manifest spherical equivalent was within ±0.5 diopter in all eyes. No eye lost 2 or more lines of CDVA, and 29.2% of the eyes gained 1 or more lines of CDVA. Wavefront-guided LASIK performed using data derived from the new Hartmann-Shack aberrometer was safe, effective, and predictable for treating myopia and myopic astigmatism. No author has a financial or proprietary interest in any material or method mentioned. Copyright © 2015 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.

Accommodative Behavior of Young Eyes Wearing Multifocal Contact Lenses.

PubMed

Altoaimi, Basal H; Almutairi, Meznah S; Kollbaum, Pete S; Bradley, Arthur

2018-05-01

The effectiveness of multifocal contact lenses (MFCLs) at slowing myopia progression may hinge on the accommodative behavior of young eyes fit with these presbyopic style lenses. Can they remove hyperopic defocus? Convergence accommodation as well as pupil size and the zonal geometry are likely to contribute to the final accommodative responses. The aim of this study was to examine the accommodation behavior of young adult eyes wearing MFCLs and the effectiveness of these MFCLs at removing foveal hyperopic defocus when viewing near targets binocularly. Using a high-resolution Shack-Hartmann aberrometer, accommodation and pupil behavior of eight young adults (27.25 ± 2.05 years) were measured while subjects fixated a 20/40 character positioned between 2 m and 20 cm (0.50 to 5.00 diopters [D]) in 0.25-D steps. Refractive states were measured while viewing binocularly and monocularly with single-vision and both center-distance and center-near +2.00 D add MFCLs. Refractive state was defined using three criteria: the dioptric power that would (1) minimize the root mean square wavefront error, (2) focus the pupil center, and (3) provide the peak image quality. Refractive state pupil maps reveal the complex optics that exist in eyes wearing MFCLs. Reduced accommodative gain beyond the far point of the near add revealed that young subjects used the added plus power to help focus near targets. During accommodation to stimuli closer than the far point generated by the add power, a midperipheral region of the pupil was approximately focused, resulting in the smallest accommodative errors for the minimum root mean square-defined measures of refractive state. Paraxial images were always hyperopically or myopically defocused in eyes viewing binocularly with center-distance or center-near MFCLs, respectively. Because of zone geometry in the concentric MFCLs tested, the highly aberrated transition zone between the distance and near optics contributed a significant proportion and sometimes the majority of light to the resulting images. Young eyes fit with MFCLs containing significant transition zones accommodated to focus pupil regions between the near and distance optics, which resulted in less than optimal retinal image quality and myopic or hyperopic defocus in either the pupil center or pupil margins.

Near work, outdoor activity, and myopia in children in rural China: the Handan offspring myopia study.

PubMed

Lin, Zhong; Gao, Tie Ying; Vasudevan, Balamurali; Ciuffreda, Kenneth J; Liang, Yuan Bo; Jhanji, Vishal; Fan, Su Jie; Han, Wei; Wang, Ning Li

2017-11-17

The near work and outdoor activity are the most important environmental risk factors for myopia. However, data from Chinese rural children are relatively rare and remain controversial. Therefore, the purpose of this study was to evaluate the relationship of both near work and outdoor activities with refractive error in rural children in China. In this cross-sectional study, 572 (65.1%) of 878 children (6-18 years of age) were included from the Handan Offspring Myopia Study (HOMS). Information from the parents on these children, as well as the parent's non-cycloplegic refraction, were obtained from the database of the Handan Eye Study conducted in the years 2006-2007. A comprehensive vision examination, including cycloplegic refraction, and a related questionnaire, were assessed on all children. The overall time spent on near work and outdoor activity in the children was 4.8 ± 1.6 and 2.9 ± 1.4 h per day, respectively. Myopic children spent more time on near work (5.0 ± 1.7 h vs.4.7 ± 1.6 h, p = 0.049), while no significant difference was found in outdoor activity hours (2.8 ± 1.3 h vs. 3.0 ± 1.4 h, p = 0.38), as compared to non-myopic children. In the multiple logistic analysis, in general, no association between near work and myopia was found after adjusting for the children's age, gender, parental refractive error, parental educational level, and daily outdoor activity hours [odds ratio (OR), 95% confidence interval (CI): 1.10, 0.94-1.27]. However, a weak protective effect of the outdoor activity on myopia was found (OR, 95% CI: 0.82, 0.70-0.96), after adjusting for similar confounders. In general, no association between near work and myopia was found, except for the high near work subgroup with moderate outdoor activity levels. A weak protective effect of outdoor activity on myopia in Chinese rural children was observed.

Combined laser in situ keratomileusis and prophylactic high-fluence corneal collagen crosslinking for high myopia: two-year safety and efficacy.

PubMed

Kanellopoulos, Anastasios John; Asimellis, George

2015-07-01

To evaluate the safety, efficacy, and refractive and keratometric stability of myopic femtosecond laser in situ keratomileusis (LASIK) with concurrent prophylactic high-fluence corneal collagen crosslinking (CXL) compared with the outcomes of standard femtosecond LASIK. Private clinical practice, Athens, Greece. Consecutive randomized prospective comparative study. Eyes that had myopic LASIK or myopic LASIK with concurrent high-fluence CXL were evaluated preoperatively and up to 2 years postoperatively for manifest refraction spherical equivalent (MRSE), refractive astigmatism, visual acuity, corneal keratometry (K), and endothelial cell count. One hundred forty consecutive eyes had myopic LASIK; 65 of the eyes were treated additionally with CXL. In the LASIK-CXL eyes, the mean postoperative MRSE was -0.18 diopter (D) ± 17.0 (SD) from -6.67 ± 2.14 D preoperatively. The postoperative flat K was 37.67 D from 43.92 D, and the steep K was 38.38 D from 45.15 D. The correlation coefficient of SE correction predictability was 0.975. In the LASIK-only eyes, the mean postoperative MRSE was -0.32 ± 0.24 D from -5.49 ± 1.99 D preoperatively. The flat K was 38.04 D from 43.15 D, and the steep K was 38.69 D from 44.03 D. The correlation coefficient of SE correction predictability was 0.968. The differences between the 2 groups at the 20/20 and 20/25 levels were statistically significant (P = .045 and P = .039, respectively). Two-year results indicate that the application of prophylactic CXL concurrently with high-myopic LASIK appears to improve refractive and keratometric stability, presumably by affecting corneal biomechanical properties. Dr. Kanellopoulos is a consultant to Alcon Surgical, Inc., Wavelight Laser Technologie AG, Allergan, Inc., Avedro, Inc., and i-Optics Corp. Dr. Asimellis has no financial or proprietary interest in any material or method mentioned. Copyright © 2015 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.

The corneal nerve density in the sub-basal plexus decreases with increasing myopia: a pilot study.

PubMed

Harrison, Wendy W; Putnam, Nicole M; Shukis, Christine; Nguyen, Evelyn; Reinard, Kristen; Hundelt, Elizabeth; Vardanyan, Galina; Gabai, Celine; Yevseyenkov, Vladimir

2017-07-01

Myopia can cause many changes in the health of the eye. As it becomes more prevalent worldwide, more patients seek correction in the form of glasses, contact lenses and refractive surgery. In this study we explore the impact that high myopia has on central corneal nerve density by comparing sub basal nerve plexus density measured by confocal microscopy in a variety of refractive errors. Seventy healthy adult subjects between the ages of 21-50 years participated in this study. The study took place in two phases with no overlapping subjects (n = 30 phase 1 and n = 40 phase 2). In both phases an autorefraction, keratometry reading, corneal thickness measure and confocal corneal scan of the sub basal nerve plexus were performed for both eyes. There were 11 hyperopes (+0.50 to +3.50DS), six emmetropes (-0.25 to +0.50DS), 30 low myopes (-5.50 to -0.50DS), and 23 high myopes (-5.50DS and above). In the second phase of the study additional tests were performed including an axial length, additional corneal scans, and a questionnaire that asked about age of first refractive correction and contact lens wear. Corneal nerves were imaged over the central cornea with a Nidek CS4 confocal microscope (460 × 345 μm field). Nerves were evaluated using the NeuronJ program for density calculation. One eye was selected for inclusion based on image quality and higher refractive error (more myopic or hyperopic). As myopia increased, nerve density decreased (t 1  = 3.86, p < 0.001). We also note a decrease in data scatter above -7 D. The relationship between axial length values and nerve density was also significant and the slope was not as robust as refractive error (t 1  = 2.4, p < 0.04). As expected there was a significant difference between the four groups in axial length (F 3  = 19.9, p < 0.001) and age of first refractive correction of the myopic groups (14.9 vs 11.5 years; t 46  = 2.99 p < 0.01). There was no difference in keratometry readings or corneal thickness between the groups (F 3  = 0.6, p = 0.66 and F 3  = 1.2, p = 0.33 respectively). Corneal nerve density in the sub-basal plexus decreased with increasing myopia. This could have implications for corneal surgery and contact lens wear in this patient population. © 2017 The Authors Ophthalmic & Physiological Optics © 2017 The College of Optometrists.

Vector analysis of astigmatic correction after small-incision lenticule extraction and femtosecond-assisted LASIK for low to moderate myopic astigmatism.

PubMed

Chan, Tommy C Y; Ng, Alex L K; Cheng, George P M; Wang, Zheng; Ye, Cong; Woo, Victor C P; Tham, Clement C Y; Jhanji, Vishal

2016-04-01

To compare astigmatic correction between femtosecond-assisted laser in situ keratomileusis (LASIK) and small-incision lenticule extraction (SMILE). A total of 111 patients were included in this prospective study. Fifty-seven eyes were treated with LASIK and 54 eyes were treated with SMILE for myopia with low to moderate (-0.25 to -4.0 D) astigmatism. Uncorrected distance visual acuity (UDVA), corrected distance visual acuity and manifest refraction were measured preoperatively and at 1 and 3 months postoperatively. Visual and refractive outcomes were reported. Changes in refractive astigmatism were evaluated using vector analysis. Preoperative characteristics were similar between both groups. The UDVA at 1 and 3 months was better in the LASIK group compared with the SMILE group (p<0.009). Postoperative cylinder was higher in the SMILE group (p<0.001). Fewer eyes attained the attempted cylindrical correction in the SMILE group (p<0.029). Vector analysis showed no significant difference in target-induced astigmatism (p=0.091) and angle of error (p>0.596) between the two groups. Surgically induced astigmatism was significantly lower in the SMILE group (p<0.023), while the difference vector (p<0.001) and absolute angle of error (p<0.016) were significantly higher in the SMILE group. No significant difference was found in these parameters between 1 and 3 months in both groups (p>0.122). Our results showed that SMILE offered a less favourable astigmatic correction comparable to femtosecond-assisted LASIK in eyes with low to moderate myopic astigmatism. The alignment of treatment was more variable in SMILE, leading to a lower efficacy compared with LASIK by 3 months postoperatively. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/

Comparison of the biometric formulas used for applanation A-scan ultrasound biometry.

PubMed

Özcura, Fatih; Aktaş, Serdar; Sağdık, Hacı Murat; Tetikoğlu, Mehmet

2016-10-01

The purpose of the study was to compare the accuracy of various biometric formulas for predicting postoperative refraction determined using applanation A-scan ultrasound. This retrospective comparative study included 485 eyes that underwent uneventful phacoemulsification with intraocular lens (IOL) implantation. Applanation A-scan ultrasound biometry and postoperative manifest refraction were obtained in all eyes. Biometric data were entered into each of the five IOL power calculation formulas: SRK-II, SRK/T, Holladay I, Hoffer Q, and Binkhorst II. All eyes were divided into three groups according to axial length: short (≤22.0 mm), average (22.0-25.0 mm), and long (≥25.0 mm) eyes. The postoperative spherical equivalent was calculated and compared with the predicted refractive error using each biometric formula. The results showed that all formulas had significantly lower mean absolute error (MAE) in comparison with Binkhorst II formula (P < 0.01). The lowest MAE was obtained with the SRK-II for average (0.49 ± 0.40 D) and short (0.67 ± 0.54 D) eyes and the SRK/T for long (0.61 ± 0.50 D) eyes. The highest postoperative hyperopic shift was seen with the SRK-II for average (46.8 %), short (28.1 %), and long (48.4 %) eyes. The highest postoperative myopic shift was seen with the Holladay I for average (66.4 %) and long (71.0 %) eyes and the SRK/T for short eyes (80.6 %). In conclusion, the SRK-II formula produced the lowest MAE in average and short eyes and the SRK/T formula produced the lowest MAE in long eyes. The SRK-II has the highest postoperative hyperopic shift in all eyes. The highest postoperative myopic shift is with the Holladay I for average and long eyes and SRK/T for short eyes.

Prevalence and association of refractive anisometropia with near work habits among young schoolchildren: The evidence from a population-based study

PubMed Central

Lee, Chia-Wei; Fang, Shao-You; Huang, Nicole; Hsu, Chih-Chien; Chen, Shing-Yi; Chiu, Allen Wen-Hsiang

2017-01-01

Background Lifestyle behaviour may play a role in refractive error among children, but the association between near work habits and refractive anisometropia remains unclear. Methods We estimated the prevalence of refractive anisometropia and examined its association with near work activities among 23,114 children in the Myopia Investigation Study in Taipei who were grade 2 elementary school students at baseline in 2013 and 2014. Baseline data on demographics, medical history, parental history and near work habits were collected by parent-administered questionnaire survey. Refractive status was determined by cycloplegic autorefraction. Refractive anisometropia was defined as the spherical equivalent difference ≥ 1.0 diopter between eyes. Results The prevalence of refractive anisometropia was 5.3% (95% confidence interval [CI], 5.0% to 5.6%). The prevalence and severity of refractive anisometropia increased with both myopic and hyperopic refractive error. Multivariate logistic regression analysis revealed that refractive anisometropia was significantly associated with myopia (odds ratio [OR], 2.98; 95% CI, 2.53–3.51), hyperopia (OR, 2.37; 95% CI, 1.98–2.83), degree of astigmatism (OR, 1.005; 95% CI, 1.005–1.006), amblyopia (OR, 2.54; 95% CI, 2.06–3.12), male gender (OR, 0.88; 95% CI, 0.78–0.99) and senior high school level of maternal education (OR, 0.69; 95% CI, 0.52–0.92). Though anisometropic children were more likely to spend more time on near work (crude OR, 1.15; 95% CI, 1.02–1.29) and to have less eye-to-object distance in doing near work (crude OR, 1.15; 95% CI, 1.01–1.30), these associations became insignificant after additional adjustment for ocular, demographic and parental factors. Conclusions The present study provides large-scale, population-based evidence showing no independent association between refractive anisometropia and near work habits, though myopia is associated with refractive anisometropia. PMID:28273153

Prevalence and association of refractive anisometropia with near work habits among young schoolchildren: The evidence from a population-based study.

PubMed

Lee, Chia-Wei; Fang, Shao-You; Tsai, Der-Chong; Huang, Nicole; Hsu, Chih-Chien; Chen, Shing-Yi; Chiu, Allen Wen-Hsiang; Liu, Catherine Jui-Ling

2017-01-01

Lifestyle behaviour may play a role in refractive error among children, but the association between near work habits and refractive anisometropia remains unclear. We estimated the prevalence of refractive anisometropia and examined its association with near work activities among 23,114 children in the Myopia Investigation Study in Taipei who were grade 2 elementary school students at baseline in 2013 and 2014. Baseline data on demographics, medical history, parental history and near work habits were collected by parent-administered questionnaire survey. Refractive status was determined by cycloplegic autorefraction. Refractive anisometropia was defined as the spherical equivalent difference ≥ 1.0 diopter between eyes. The prevalence of refractive anisometropia was 5.3% (95% confidence interval [CI], 5.0% to 5.6%). The prevalence and severity of refractive anisometropia increased with both myopic and hyperopic refractive error. Multivariate logistic regression analysis revealed that refractive anisometropia was significantly associated with myopia (odds ratio [OR], 2.98; 95% CI, 2.53-3.51), hyperopia (OR, 2.37; 95% CI, 1.98-2.83), degree of astigmatism (OR, 1.005; 95% CI, 1.005-1.006), amblyopia (OR, 2.54; 95% CI, 2.06-3.12), male gender (OR, 0.88; 95% CI, 0.78-0.99) and senior high school level of maternal education (OR, 0.69; 95% CI, 0.52-0.92). Though anisometropic children were more likely to spend more time on near work (crude OR, 1.15; 95% CI, 1.02-1.29) and to have less eye-to-object distance in doing near work (crude OR, 1.15; 95% CI, 1.01-1.30), these associations became insignificant after additional adjustment for ocular, demographic and parental factors. The present study provides large-scale, population-based evidence showing no independent association between refractive anisometropia and near work habits, though myopia is associated with refractive anisometropia.

What is the influence of parents' myopia on their children's myopic progression? A 22-year follow-up study.

PubMed

Pärssinen, Olavi; Kauppinen, Markku

2016-09-01

To study the connection between parental myopia and their children's myopia from school age to adulthood. Two hundred and forty myopic schoolchildren (119 boys, 121 girls, mean age 10.9 years) with no previous spectacles for myopia were recruited to a 3-year treatment trial with different use of spectacles. Follow-ups were performed at mean ages of 13.9, 23.7 and 33.2 years for 238, 176 and 170 subjects respectively. Subjective refraction was calibrated to the spherical equivalent at corneal level (SEcor). Corneal refractive power (CR) and axial length (AL) were measured. Parental myopia was assessed with a questionnaire and the children assigned accordingly to one of three hereditary groups: both parents myopic H++, one myopic parent = H+- and no myopic parents = H-. At baseline, no significant gender differences in age or SEcor were found in the different hereditary groups. Among girls, CR was significantly higher in hereditary group H++ (45.20 ± 1.08 D) than in group H+- (44.19 ± 1.28 D; p = 0.006) or H- (43.84 ± 1.18 D; p < 0.001). Among boys, the differences in CR between the hereditary groups were smaller and significant at follow-up 2 only. At follow-up end, among males, no significant differences between the hereditary groups were found in SEcor, CR, AL or myopic progression. Among females, myopic progression was 4.21 ± 1.81 D if one or both parents were myopic and -3.19 ± 1.36 D if neither parent was myopic (p = 0.035), but no significant difference was observed in AL. The main difference between the hereditary groups was higher CR and myopic progression among females with myopic parents than non-myopic parents, but with no significant difference in AL with respect to parental myopia at study end. © 2016 Acta Ophthalmologica Scandinavica Foundation. Published by John Wiley & Sons Ltd.

Stereoacuity changes after laser in situ keratomileusis.

PubMed

Singh, Digvijay; Saxena, Rohit; Sinha, Rajesh; Titiyal, Jeewan S

2015-02-01

To study changes in near and distance stereoacuity after laser in situ keratomileusis (LASIK). A prospective interventional study was conducted at an apex tertiary care ophthalmology center in India. Near and distance stereoacuity was tested in 40 patients (80 eyes) who underwent LASIK for myopic correction and got unaided vision of 0.67 or better in each eye. Stereoacuity was tested with best spectacle correction before LASIK, and post-LASIK stereoacuity was tested with unaided eye near and distance Randot tests. Forty patients (80 eyes) had a mean (±SD) pre-LASIK refractive error of -4.70 (±1.72) DS OD and -4.59 (±1.58) DS OS and a mean (±SD) anisometropia of 0.55 (±0.51) DS. The median pre-LASIK near stereoacuity was 70 arcsec and distance stereoacuity was 200 arcsec, both of which improved after LASIK to 30 and 60 arcsec, respectively (p < 0.001, both). Amount of refractive error was not associated with stereoacuity but anisometropia of greater than or equal to 1 diopter had significantly worse distance stereoacuity in both the pre-LASIK and post-LASIK period. The post-LASIK near stereoacuity and distance stereoacuity were strongly associated (r = 0.706, p < 0.001) unlike the change in stereoacuity. Near and distance stereoacuity shows significant improvement after LASIK. Stereoacuity is associated with the degree of anisometropia but not the amount of refractive error corrected.

Acute acquired comitant esotropia related to excessive Smartphone use.

PubMed

Lee, Hyo Seok; Park, Sang Woo; Heo, Hwan

2016-04-09

To describe the clinical characteristics and outcomes of acute acquired comitant esotropia (AACE) related to excessive smartphone use in adolescents. The medical records of 12 patients with AACE and a history of excessive smartphone use were retrospectively reviewed, and the duration of smartphone use, angle of deviation, refractive error, stereopsis, and treatment options were analyzed. All patients showed convergent and comitant esotropia ranging from 15 to 45 prism diopters (PD; average: 27.75 ± 11.47 PD) at far fixation. The angle of deviation was nearly equivalent for far and near fixation. Every patient used a smartphone for more than 4 h a day over a period of several months (minimum 4 months). Myopic refractive errors were detected in eight patients (average:-3.84 ± 1.68 diopters (D]), and the remaining four patients showed mild hyperopic refractive error (average: +0.84 ± 0.53 D). Reductions in esodeviation were noted in all patients after refraining from smartphone use, and bilateral medial rectus recession was performed in three patients with considerable remnant esodeviation. Postoperative exams showed orthophoria with good stereoacuity in these patients. Excessive smartphone use might influence AACE development in adolescents. Refraining from smartphone use can decrease the degree of esodeviation in these patients, and remnant deviation can be successfully managed with surgical correction.

Stability of corneal topography and wavefront aberrations in young Singaporeans.

PubMed

Zhu, Mingxia; Collins, Michael J; Yeo, Anna C H

2013-09-01

The aim was to investigate the differences between and variations across time in corneal topography and ocular wavefront aberrations in young Singaporean myopes and emmetropes. We used a videokeratoscope and wavefront sensor to measure the ocular surface topography and wavefront aberrations of the total-eye optics in the morning, midday and late afternoon on two separate days. Topographic data were used to derive the corneal surface wavefront aberrations. Both the corneal and total wavefronts were analysed up to the fourth radial order of the Zernike polynomial expansion and were centred on the entrance pupil (5.0 mm). The participants included 12 young progressing myopes, 13 young stable myopes and 15 young age-matched emmetropes. For all subjects considered together, there were significant changes in some of the aberrations across the day, such as spherical aberration ( Z(4 0)) and vertical coma ( Z (3 - 1)) (repeated measures analysis of variance, p < 0.05). The magnitude of positive spherical aberration ( Z(4 0)) was significantly lower in the progressing myopic group than in the stable myopic (p = 0.04) and emmetropic (p = 0.02) groups. There were also significant interactions between refractive group and time of day for with and against-the-rule astigmatism ( Z(2 2)). Significantly lower fourth-order root mean square of ocular wavefront aberrations were found in the progressing myopic group compared with the stable myopes and emmetropes (p < 0.01). These differences and variations in the corneal and total aberrations may have significance for our understanding of refractive error development and for clinical applications requiring accurate wavefront measurements. © 2013 The Authors. Clinical and Experimental Optometry © 2013 Optometrists Association Australia.

Prevalence and risk factors for refractive errors in Indians: the Singapore Indian Eye Study (SINDI).

PubMed

Pan, Chen-Wei; Wong, Tien-Yin; Lavanya, Raghavan; Wu, Ren-Yi; Zheng, Ying-Feng; Lin, Xiao-Yu; Mitchell, Paul; Aung, Tin; Saw, Seang-Mei

2011-05-16

To determine the prevalence and risk factors for refractive errors in middle-aged to elderly Singaporeans of Indian ethnicity. A population-based, cross-sectional study of Indians aged over 40 years of age residing in Southwestern Singapore was conducted. An age-stratified (10-year age group) random sampling procedure was performed to select participants. Refraction was determined by autorefraction followed by subjective refraction. Myopia was defined as spherical equivalent (SE) < -0.50 diopters (D), high myopia as SE < -5.00 D, astigmatism as cylinder < -0.50 D, hyperopia as SE > 0.50 D, and anisometropia as SE difference > 1.00 D. Prevalence was adjusted to the 2000 Singapore census. Of the 4497 persons eligible to participate, 3400 (75.6%) were examined. Complete data were available for 2805 adults with right eye refractive error and no prior cataract surgery. The age-adjusted prevalence was 28.0% (95% confidence interval [CI], 25.8-30.2) for myopia and 4.1% (95% CI, 3.3-5.0) for high myopia. There was a U-shaped relationship between myopia and increasing age. The age-adjusted prevalence was 54.9% (95% CI, 52.0-57.9) for astigmatism, 35.9% (95% CI, 33.7-38.3) for hyperopia, and 9.8% (95% CI, 8.6-11.1) for anisometropia. In a multiple logistic regression model, adults who were female, younger, taller, spent more time reading and writing per day, or had astigmatism were more likely to be myopic. Adults who were older or had myopia or diabetes mellitus had higher risk of astigmatism. In Singapore, the prevalence of myopia in Indian adults is similar to those in Malays, but lower than those in Chinese. Risk factors for myopia are similar across the three ethnic groups in Singapore.

Visual outcomes after spectacles treatment in children with bilateral high refractive amblyopia.

PubMed

Lin, Pei-Wen; Chang, Hsueh-Wen; Lai, Ing-Chou; Teng, Mei-Ching

2016-11-01

The aim was to investigate the visual outcomes of treatment with spectacles for bilateral high refractive amblyopia in children three to eight years of age. Children with previously untreated bilateral refractive amblyopia were enrolled. Bilateral high refractive amblyopia was defined as visual acuity (VA) being worse than 6/9 in both eyes in the presence of 5.00 D or more of hyperopia, 5.00 D or more of myopia and 2.00 D or more of astigmatism. Full myopic and astigmatic refractive errors were corrected, and the hyperopic refractive errors were corrected within 1.00 D of the full correction. All children received visual assessments at four-weekly intervals. VA, Worth four-dot test and Randot preschool stereotest were assessed at baseline and every four weeks for two years. Twenty-eight children with previously untreated bilateral high refractive amblyopia were enrolled. The mean VA at baseline was 0.39 ± 0.24 logMAR and it significantly improved to 0.21, 0.14, 0.11, 0.05 and 0.0 logMAR at four, eight, 12, 24 weeks and 18 months, respectively (all p = 0.001). The mean stereoacuity (SA) was 1,143 ± 617 arcsec at baseline and it significantly improved to 701, 532, 429, 211 and 98 arcsec at four, eight, 12, 24 weeks and 18 months, respectively (all p = 0.001). The time interval for VA achieving 6/6 was significantly shorter in the eyes of low spherical equivalent (SE) (-2.00 D < SE < +2.00 D) than in those of high SE (SE > +2.00 D) (3.33 ± 2.75 months versus 8.11 ± 4.56 months, p = 0.0005). All subjects had normal fusion on Worth four-dot test at baseline and all follow-up visits. Refractive correction with good spectacles compliance improves VA and SA in young children with bilateral high refractive amblyopia. Patients with greater amounts of refractive error will achieve resolution of amblyopia with a longer time. © 2016 Optometry Australia.

The albino chick as a model for studying ocular developmental anomalies, including refractive errors, associated with albinism.

PubMed

Rymer, Jodi; Choh, Vivian; Bharadwaj, Shrikant; Padmanabhan, Varuna; Modilevsky, Laura; Jovanovich, Elizabeth; Yeh, Brenda; Zhang, Zhan; Guan, Huanxian; Payne, W; Wildsoet, Christine F

2007-10-01

Albinism is associated with a variety of ocular anomalies including refractive errors. The purpose of this study was to investigate the ocular development of an albino chick line. The ocular development of both albino and normally pigmented chicks was monitored using retinoscopy to measure refractive errors and high frequency A-scan ultrasonography to measure axial ocular dimensions. Functional tests included an optokinetic nystagmus paradigm to assess visual acuity, and flash ERGs to assess retinal function. The underlying genetic abnormality was characterized using a gene microarray, PCR and a tyrosinase assay. The ultrastructure of the retinal pigment epithelium (RPE) was examined using transmission electron microscopy. PCR confirmed that the genetic abnormality in this line is a deletion in exon 1 of the tyrosinase gene. Tyrosinase gene expression in isolated RPE cells was minimally detectable, and there was minimal enzyme activity in albino feather bulbs. The albino chicks had pink eyes and their eyes transilluminated, reflecting the lack of melanin in all ocular tissues. All three main components, anterior chamber, crystalline lens and vitreous chamber, showed axial expansion over time in both normal and albino animals, but the anterior chambers of albino chicks were consistently shallower than those of normal chicks, while in contrast, their vitreous chambers were longer. Albino chicks remained relatively myopic, with higher astigmatism than the normally pigmented chicks, even though both groups underwent developmental emmetropization. Albino chicks had reduced visual acuity yet the ERG a- and b-wave components had larger amplitudes and shorter than normal implicit times. Developmental emmetropization occurs in the albino chick but is impaired, likely because of functional abnormalities in the RPE and/or retina as well as optical factors. In very young chicks the underlying genetic mutation may also contribute to refractive error and eye shape abnormalities.

Refractive errors in students from Middle Eastern backgrounds living and undertaking schooling in Australia.

PubMed

Azizoglu, Serap; Junghans, Barbara M; Barutchu, Ayla; Crewther, Sheila G

2011-01-01

  Environmental factors associated with schooling systems in various countries have been implicated in the rising prevalence of myopia, making the comparison of prevalence of refractive errors in migrant populations of interest. This study aims to determine the prevalence of refractive errors in children of Middle Eastern descent, raised and living in urban Australia but actively maintaining strong ties to their ethnic culture, and to compare them with those in the Middle East where myopia prevalence is generally low.   A total of 354 out of a possible 384 late primary/early secondary schoolchildren attending a private school attracting children of Middle Eastern background in Melbourne were assessed for refractive error and visual acuity. A Shin Nippon open-field NVision-K5001 autorefractor was used to carry out non-cycloplegic autorefraction while viewing a distant target. For statistical analyses students were divided into three age groups: 10-11 years (n = 93); 12-13 years (n = 158); and 14-15 years (n = 102).   All children were bilingual and classified as of Middle Eastern (96.3 per cent) or Egyptian (3.7 per cent) origin. Ages ranged from 10 to 15 years, with a mean of 13.17 ± 0.8 (SEM) years. Mean spherical equivalent refraction (SER) for the right eye was +0.09 ± 0.07 D (SEM) with a range from -7.77 D to +5.85 D. The prevalence of myopia, defined as a spherical equivalent refraction 0.50 D or more of myopia, was 14.7 per cent. The prevalence of hyperopia, defined as a spherical equivalent refraction of +0.75 D or greater, was 16.4 per cent, while hyperopia of +1.50 D or greater was 5.4 per cent. A significant difference in SER was seen as a function of age; however, no significant gender difference was seen.   This is the first study to report the prevalence of refractive errors for second-generation Australian schoolchildren coming from a predominantly Lebanese Middle Eastern Arabic background, who endeavour to maintain their ethnic ties. The relatively low prevalence of myopia is similar to that found for other metropolitan Australian school children but higher than that reported in the Middle East. These results suggest that lifestyle and educational practices may be a significant influence in the progression of myopic refractive errors. © 2010 The Authors. Clinical and Experimental Optometry © 2010 Optometrists Association Australia.

Time spent in outdoor activities in relation to myopia prevention and control: a meta-analysis and systematic review.

PubMed

Xiong, Shuyu; Sankaridurg, Padmaja; Naduvilath, Thomas; Zang, Jiajie; Zou, Haidong; Zhu, Jianfeng; Lv, Minzhi; He, Xiangui; Xu, Xun

2017-09-01

Outdoor time is considered to reduce the risk of developing myopia. The purpose is to evaluate the evidence for association between time outdoors and (1) risk of onset of myopia (incident/prevalent myopia); (2) risk of a myopic shift in refractive error and c) risk of progression in myopes only. A systematic review followed by a meta-analysis and a dose-response analysis of relevant evidence from literature was conducted. PubMed, EMBASE and the Cochrane Library were searched for relevant papers. Of the 51 articles with relevant data, 25 were included in the meta-analysis and dose-response analysis. Twenty-three of the 25 articles involved children. Risk ratio (RR) for binary variables and weighted mean difference (WMD) for continuous variables were conducted. Mantel-Haenszel random-effects model was used to pool the data for meta-analysis. Statistical heterogeneity was assessed using the I 2 test with I 2  ≥ 50% considered to indicate high heterogeneity. Additionally, subgroup analyses (based on participant's age, prevalence of myopia and study type) and sensitivity analyses were conducted. A significant protective effect of outdoor time was found for incident myopia (clinical trials: risk ratio (RR) = 0.536, 95% confidence interval (CI) = 0.338 to 0.850; longitudinal cohort studies: RR = 0.574, 95% CI = 0.395 to 0.834) and prevalent myopia (cross-sectional studies: OR = 0.964, 95% CI = 0.945 to 0.982). With dose-response analysis, an inverse nonlinear relationship was found with increased time outdoors reducing the risk of incident myopia. Also, pooled results from clinical trials indicated that when outdoor time was used as an intervention, there was a reduced myopic shift of -0.30 D (in both myopes and nonmyopes) compared with the control group (WMD = -0.30, 95% CI = -0.18 to -0.41) after 3 years of follow-up. However, when only myopes were considered, dose-response analysis did not find a relationship between time outdoors and myopic progression (R 2  = 0.00064). Increased time outdoors is effective in preventing the onset of myopia as well as in slowing the myopic shift in refractive error. But paradoxically, outdoor time was not effective in slowing progression in eyes that were already myopic. Further studies evaluating effect of outdoor in various doses and objective measurements of time outdoors may help improve our understanding of the role played by outdoors in onset and management of myopia. © 2017 The Authors. Acta Ophthalmologica published by John Wiley & Sons Ltd on behalf of Acta Ophthalmologica Scandinavica Foundation.

Primary angle closure glaucoma in a myopic kinship.

PubMed

Hagan, J C; Lederer, C M

1985-03-01

Three related myopic individuals with primary angle closure glaucoma are reported. They had true myopia and not pseudomyopia secondary to increased lenticular index of refraction. We believe one of these individuals (-8.62 spherical equivalent) to have the most myopic case of primary angle closure glaucoma reported in the literature. Although myopia is associated with anatomical factors that offer considerable protection from primary angle closure glaucoma, its presence does not eliminate the possibility of this disease. Laser iridectomy was effective in the treatment of these patients.

Emmetropization and Eye Growth in Young Aphakic Chickens

PubMed Central

Ai, Likun; Li, Jing; Guan, Huan; Wildsoet, Christine F.

2009-01-01

Purpose To establish a chick model to investigate the trends of eye growth and emmetropization after early lensectomy for congenital cataract. Methods Four monocular treatments were applied: lens extraction (LX); sham surgery/-30 D lens; LX/+20 D lens; and LX/+30-D lens (nine per group). Lens powers were selected to slightly undercorrect or overcorrect the induced hyperopia in LX eyes and to induce comparable hyperopia in sham-surgery eyes. Refractive errors and axial ocular dimensions were measured over a 28-day period. External ocular dimensions were obtained when the eyes were enucleated on the last day. Results The growth patterns of experimental (Exp) eyes varied with the type of manipulation. All eyes experiencing hyperopia initially grew more than their fellow eyes and exhibited myopic shifts in refraction. The sham/-30 D lens group showed the greatest increase in optical axial length, followed by the LX group, and then the LX/+20 D lens group. The Exp eyes of the LX/+30 D lens group, which were initially slightly myopic, grew least, and showed a small hyperopic shift. Lensectomized eyes enlarged more equatorially than axially (i.e., oblate), irrespective of the optical treatment applied. Conclusions The refractive changes observed in young, aphakic eyes are consistent with compensation for the defocus experienced, and thus emmetropization. However, differences in the effects of lensectomy compared to those of sham surgery raise the possibility that the lens is a source of essential growth factors. Alterative optical and mechanical explanations are offered for the oblate shapes of aphakic eyes. PMID:18719085

Effects of the chromatic defocus caused by interchange of two monochromatic lights on refraction and ocular dimension in guinea pigs.

PubMed

Qian, Yi-Feng; Dai, Jin-Hui; Liu, Rui; Chen, Min-Jie; Zhou, Xing-Tao; Chu, Ren-Yuan

2013-01-01

To investigate refractive and axial responses to the shift of focal plane resulting from the interchange of two monochromatic lights separately corresponding to the peak wavelengths of the cones absorption spectrum in retina, fifty 2-week-old pigmented guinea pigs were randomly assigned to five groups based on the mode of illumination: short-wavelength light (SL), middle-wavelength light (ML) and broad-band white light (BL) for 20 weeks, SL for 10 weeks followed by ML for 10 weeks (STM), as well as ML for 10 weeks followed by SL for 10 weeks (MTS). Biometric and refractive measurements were then performed every 2 weeks. After 10 weeks, SL and STM groups became more hyperopic and had less vitreous elongation than BL group. However, ML and MTS groups became more myopic and had more vitreous elongation. After interchange of the monochromatic light, the refractive error decreased rapidly by about 1.93D and the vitreous length increased by 0.14 mm in STM group from 10 to 12 weeks. After that, there were no significant intergroup differences between STM and BL groups. The interchange from ML to SL quickly increased the refractive error by about 1.53D and decreased the vitreous length by about 0.13 mm in MTS group after two weeks. At this time, there were also no significant intergroup differences between MTS and BL groups. The guinea pig eye can accurately detect the shift in focal plane caused by interchange of two monochromatic lights and rapidly generate refractive and axial responses. However, an excessive compensation was induced. Some properties of photoreceptors or retina may be changed by the monochromatic light to influence the following refractive development.

LASIK for spherical refractive myopia: effect of topographic astigmatism (ocular residual astigmatism, ORA) on refractive outcome.

PubMed

Frings, Andreas; Richard, Gisbert; Steinberg, Johannes; Skevas, Christos; Druchkiv, Vasyl; Katz, Toam; Linke, Stephan J

2015-01-01

In eyes with a preoperative plano refractive cylinder, it would appear that there is no rationale for astigmatic treatment. The aim of this retrospective, cross-sectional data analysis was to determine the amount of topographic astigmatism in refractive plano eyes that results in reduced efficacy after myopic laser in situ keratomileusis (LASIK). This study included 267 eyes from 267 consecutive myopic patients with a refractive plano cylinder. Receiver operating characteristic analysis was used to find the cut-off values of preoperative ocular residual astigmatism (= topographic astigmatism) that can best discriminate between groups of efficacy and safety indices in preoperative plano refractive cylinder eyes. Preoperative ocular residual astigmatism (ORA) (or topographic astigmatism) of ≤0.9 diopters (D) resulted in an efficacy index of at least 0.8 statistically significantly more frequently than eyes with a preoperative ORA of >0.9 D. Eyes with a high ORA preoperatively also had a high ORA postoperatively. Regression analysis showed that each diopter of preoperative ORA reduced efficacy by 0.07. A preoperative corneal astigmatism of ≥0.9 D could (partially) be taken into account in the LASIK design, even if the subjective refractive astigmatism is neutral.

Autosomal recessive retinitis pigmentosa with RP1 mutations is associated with myopia.

PubMed

Chassine, Thomas; Bocquet, Béatrice; Daien, Vincent; Avila-Fernandez, Almudena; Ayuso, Carmen; Collin, Rob Wj; Corton, Marta; Hejtmancik, J Fielding; van den Born, L Ingeborgh; Klevering, B Jeroen; Riazuddin, S Amer; Sendon, Nathacha; Lacroux, Annie; Meunier, Isabelle; Hamel, Christian P

2015-10-01

To determine the refractive error in patients with autosomal recessive retinitis pigmentosa (arRP) caused by RP1 mutations and to compare it with that of other genetic subtypes of RP. Twenty-six individuals had arRP with RP1 mutations, 25 had autosomal dominant RP (adRP) with RP1 mutation, 8 and 33 had X-linked RP (xlRP) with RP2 and RPGR mutations, respectively, 198 and 93 had Usher syndrome and arRP without RP1 mutations, respectively. The median of the spherical equivalent (SE) and the IQR (Q25-Q75) was determined and multiple comparisons were performed. arRP patients with RP1 mutations had SE median at -4.0 dioptres (D) OD (Ocula Dextra); -3.88 D OS (Ocula Sinistra), whereas arRP patients without RP1 mutations (-0.50 D OD; -0.75 D OS) and Usher syndrome patients (-0.50 D OD; -0.38 D OS) were significantly less myopic (p<0.0001). Conversely, myopia of xlRP patients with either an RPGR mutation (-4.50 D OD; -5.25 D OS) or an RP2 mutation (-6.25 D OD; -6.88 D OS) was not significantly different from the arRP group with RP1 mutations. arRP without RP1 mutations, Usher syndrome and adRP with RP1 mutation had a narrow IQR (-9.06 to -1.13 D), whereas arRP with RP1 mutations and xlRP with RP2 or RPGR mutations had a larger range (-9.06; -1.13 D). arRP patients with RP1 mutations have myopia not different from patients with xlRP with RP2 or RPGR mutations, while RP patients from other genetic subgroups were emmetropic or mildly myopic. We suggest that arRP patients with high myopic refractive error should be preferentially analysed for RP1 mutations. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/permissions.

Retinal degeneration increases susceptibility to myopia in mice

PubMed Central

Park, Hanna; Tan, Christopher C.; Faulkner, Amanda; Jabbar, Seema B.; Schmid, Gregor; Abey, Jane; Iuvone, P. Michael

2013-01-01

Purpose Retinal diseases are often associated with refractive errors, suggesting the importance of normal retinal signaling during emmetropization. For instance, retinitis pigmentosa, a disease characterized by severe photoreceptor degeneration, is associated with myopia; however, the underlying link between these conditions is not known. This study examines the influence of photoreceptor degeneration on refractive development by testing two mouse models of retinitis pigmentosa under normal and form deprivation visual conditions. Dopamine, a potential stop signal for refractive eye growth, was assessed as a potential underlying mechanism. Methods Refractive eye growth in mice that were homozygous for a mutation in Pde6b, Pde6brd1/rd1 (rd1), or Pde6brd10/rd10 (rd10) was measured weekly from 4 to 12 weeks of age and compared to age-matched wild-type (WT) mice. Refractive error was measured using an eccentric infrared photorefractor, and axial length was measured with partial coherence interferometry or spectral domain ocular coherence tomography. A cohort of mice received head-mounted diffuser goggles to induce form deprivation from 4 to 6 weeks of age. Dopamine and 3,4-dihydroxyphenylacetic acid (DOPAC) levels were measured with high-performance liquid chromatography in each strain after exposure to normal or form deprivation conditions. Results The rd1 and rd10 mice had significantly greater hyperopia relative to the WT controls throughout normal development; however, axial length became significantly longer only in WT mice starting at 7 weeks of age. After 2 weeks of form deprivation, the rd1 and rd10 mice demonstrated a faster and larger myopic shift (−6.14±0.62 and −7.38±1.46 diopter, respectively) compared to the WT mice (−2.41±0.47 diopter). Under normal visual conditions, the DOPAC levels and DOPAC/dopamine ratios, a measure of dopamine turnover, were significantly lower in the rd1 and rd10 mice compared to the WT mice, while the dopamine levels were similar or higher than WT in the rd10 mice. Lower basal levels of DOPAC were highly correlated with increasing myopic shifts. Conclusions Refractive development under normal visual conditions was disrupted toward greater hyperopia from 4 to 12 weeks of age in these photoreceptor degeneration models, despite significantly lower DOPAC levels. However, the retinal degeneration models with low basal levels of DOPAC had increased susceptibility to form deprivation myopia. These results indicate that photoreceptor degeneration may alter dopamine metabolism, leading to increased susceptibility to myopia with an environmental visual challenge. PMID:24146540

Refractive errors in an older population: the Blue Mountains Eye Study.

PubMed

Attebo, K; Ivers, R Q; Mitchell, P

1999-06-01

To determine prevalence and associations with refractive errors in a defined older population. Cross-sectional study. A total of 3654 residents, aged 49-97, of the Blue Mountains, west of Sydney, Australia. Comprehensive questionnaire and detailed eye examination, including refraction. Refractive error of phakic eyes, age, gender, and education. Prevalence rates were determined for myopia (15%), hyperopia (57%), and emmetropia (28%). Hyperopia prevalence was age-related, increasing from 36% in persons aged <60 years to 71 % of persons aged > or = 80 (P < 0.0001), whereas myopia prevalence decreased with age, from 21 % in persons aged <60 years to 10% of persons aged > or = 80 years (P < 0.0001). Younger myopic subjects in this population reported first wearing distance correction at a significantly younger age than older subjects, P < 0.0001. After adjustment for age, women were slightly more hyperopic (mean +0.75 diopters [D]) than men (mean +0.59 D, P = 0.0012. The gender-adjusted mean spherical error increased with age from +0.03 D in persons aged <60 years to +1.2 D in persons aged > or = 80 years (P < 0.0001). The gender-adjusted mean cylinder power also increased with age, from -0.6 D in persons aged <60 years to -1.2 D in persons aged > or = 80 years (P < 0.0001). The mean axis of astigmatism was "against the rule" in all age groups. Anisometropia increased with age, from a mean of 0.4 D in persons aged <60 to 0.9 D in persons aged > or = 80 years (P < 0.0001). Higher education was associated with myopia in men (P = 0.009) but not in women (P = 0.21) after adjustment for age. This report has documented the detailed refractive status of an older population, confirming previously described trends but also finding an apparent higher prevalence of myopia among younger members of this community.

A Limitation of Hartmann-Shack System in Measuring Wavefront Aberrations for Patients Received Laser Refractive Surgery

PubMed Central

Wu, Ying; He, Ji C.; Zhou, Xing T.; Chu, Ren Y.

2015-01-01

Purpose To explore the relationship between ablation parameters of myopic laser surgery and measurement area of wavefront aberration (WA) with Hartmann-Shack wavefront sensor. Methods 58 subjects undergone myopic laser surgeries and 74 uncorrected myopic subjects were enrolled in this experiment. The laser ablation parameters were obtained from surgical records, which included spherical error (Rx), depth, and optical zone (OZ) of ablation. The measured area of WA was tested by the WASCA, and the real pupil size was tested by Pentacam. The corneal eccentricity (E value) and curvature was also measured with the Pentacam. All the measurements were performed under mydriatic condition. Results For uncorrected myopic eyes, the measured area of WA was similar with the real pupil size. But for the corrected eyes, the measured area of WA was smaller than the real pupil size with a mean difference of 0.66 ± 0.54 mm for moderate myopia (t = 6.45, p < 0.0001) and 1.76 ± 0.55 mm for high myopia (t = 18.92, p < 0.0001), but not for mild myopia. The Rx (t = -3.20, p = 0.0017), OZ (t = 64.4, p < 0.0001) and postoperative corneal E value (t = 2.52, p = 0.017) were the independent factors of measured area of WA. Measured area of WA = -0.81*Rx + 1.13*OZ + 0.49*postoperative corneal E value (r2 = 0.997). Conclusions The WASCA has a limitation in measuring wavefront aberration over the whole pupil area when it’s used for patients received myopic laser surgery. The measured area is smaller than the real pupil size and depends linearly on ablation depth, optical zone and corneal eccentricity. PMID:25692489

Study of the relationship between myopia and personality.

PubMed

Rodríguez Uña, I; Pérez Bartolomé, F; Urriés Ortiz, M; Arriola Villalobos, P; Bermúdez Vallecilla, M; Fernández-Vega Cueto, L; Martín Villaescusa, C; Marticorena Álvarez, P

2015-08-01

To study the correlation between the myopic refractive error and certain personality traits, and to determine whether there is a correlation between the degree of myopia and an increased frequency in personality disorders. Cross-sectional observational multicenter study conducted on 82 subjects (26 men, 56 women) age over 18 years with myopia (spherical defect ≤ -0.5 D), with 30 subjects having high myopia (<-6 D). age and gender, academic level, result in the Neo PI-R personality test, autorefractometry, myopic pathology, and ophthalmological treatment. Correlation (Spearman's) between the magnitude of the spherical defect and the 5 personality traits studied in the total sample was not statistically significant: neuroticism (-0.057; P=.610), extroversion (-0.020; P=.857), openness (-0.032; P=.774), kindness (-0.060; P=.592), and responsibility (-0.034; P=.765). By dividing them into subgroups of low and high significance (t-test), a significant (P=.002) upward trend of the myopic defect with increasing scores on extraversion was found. When comparing high myopic subjects to the non-high myopic ones, there were significant differences between the 2 groups in terms of the associated pathology (P=.001), received treatment (P=.001) and the level of studies (P=.013). There were no differences in the variables of personality: neuroticism (P=.852), extroversion (P=.199), openness (P=.560), kindness (P=.584), and responsibility (P=.722). A low correlation was found between myopia and personality. There was no difference in the degree of myopia between the groups with different education levels. Subjects with more severe ocular pathology associated with myopia had higher scores in neuroticism, without finding any significant association. Copyright © 2014 Sociedad Española de Oftalmología. Published by Elsevier España, S.L.U. All rights reserved.

Level of education associated with ophthalmic diseases. The Beijing Eye Study.

PubMed

Xu, Liang; Wang, Ya Xing; Jonas, Jost B

2010-01-01

To determine associations between educational level and ophthalmic diseases in Chinese. The population-based Beijing Eye Study, performed in 2006, enrolled 3,251 participants (age: 45+ years) out of 4,439 subjects invited to participate (response rate: 73.2%). The participants underwent an interview including questions concerning their educational level, and a detailed ophthalmic examination. Data on the level of education were available for 3,221 (99.1%) subjects, with 1,484 (46.1%) subjects living in the rural region. The mean age was 60.4 +/- 10.1 years (range: 45-89 years). In a multivariate analysis, a higher level of education was significantly associated with myopic refractive error, higher best-corrected visual acuity, lower degree of nuclear cataract, and lower prevalence of angle-closure glaucoma, and with the systemic parameters of lower age, male gender, urban region, taller body height, and lower body mass index. It was not significantly associated with intraocular pressure, amount of subcapsular cataract and cortical cataract, cataract surgery, and the prevalences of diabetes mellitus, retinal vein occlusions, chronic open-angle glaucoma, and age-related macular degeneration, and with the systemic parameters of fasting serum concentrations of glucose, high-density lipoproteins, low-density lipoproteins, cholesterol and triglycerides, systolic and diastolic blood pressure. In the Greater Beijing area, a higher level of education was associated with myopic refractive error, higher best-corrected visual acuity, and lower prevalence of nuclear cataract and angle-closure glaucoma, after adjusting for the systemic parameters of younger age, male gender, urban region, taller body height, lower body mass index less smoking and less alcohol consumption. Educational level was not significantly associated with intraocular pressure, cortical cataract, blood pressure, and frequencies of age-related macular degeneration, retinal vein occlusions and chronic open-angle glaucoma.

Risk Factors for Cortical, Nuclear, Posterior Subcapsular, and Mixed Lens Opacities: The Los Angeles Latino Eye Study

PubMed Central

Richter, Grace M.; Torres, Mina; Choudhury, Farzana; Azen, Stanley P.; Varma, Rohit

2012-01-01

Purpose To identify socio-demographic and biological risk factors associated with having cortical, nuclear, posterior sub-capsular (PSC), and mixed lens opacities. Design Population-based, cross-sectional study Participants Five thousand nine hundred forty-five Latinos 40 years and older from 6 census tracts in Los Angeles, California. Methods Participants underwent an interview and detailed eye examination, including best-corrected visual acuity and slit-lamp assessment of lens opacities using the Lens Opacities Classification System II. Univariate and stepwise logistic regression analyses were used to identify independent risk factors associated with each type of lens opacity. Main Outcome Measures Odds ratios for socio-demographic and biological risk factors associated with cortical only, nuclear only, PSC only, and mixed lens opacities. Results Of the 5945 participants with gradable lenses, 468 had cortical only lens opacities, 217 had nuclear only lens opacities, 27 had PSC only opacities, and 364 had mixed lens opacities. Older age, higher hemoglobin A1c, and history of diabetes mellitus were independent risk factors for cortical only lens opacities. Older age, smoking, and myopic refractive error were independent risk factors for nuclear only lens opacities. Higher systolic blood pressure and history of diabetes were independent risk factors for posterior sub-capsular lens opacities. Older age, myopic refractive error, history of diabetes, higher systolic blood pressure, female gender, and presence of large drusen were independent risk factors for mixed lens opacities. Conclusions The modifiable and non-modifiable risk factors identified in this study provide insight into the mechanisms related to the development of lens opacification. Improved glycemic control, smoking cessation and prevention, and blood pressure control may help to reduce the risk of having lens opacities and their associated vision loss. PMID:22197433

Outcomes of Same-Size Host and Donor Trephine in Deep Anterior Lamellar Keratoplasty for Keratoconus.

PubMed

Huang, Ting; Ouyang, Chen; Hou, Chao; Wu, Qianni; Hu, Yunwei

2016-06-01

To evaluate the efficacy of the same-size host and donor trephine on reducing myopic refractive errors for patients with keratoconus when deep anterior lamellar keratoplasty (DALK) was used. Randomized controlled clinical trial. One hundred eighteen eyes of 118 patients with keratoconus were enrolled. Using stratified blocked randomization, eligible eyes were allocated into the same-size trephine group or oversize trephine group. Postoperative uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BSCVA), spherical equivalent (SE), topography data, and eye axial length were compared at each year for 5 years. The same-size trephine group had comparable UCVA to the oversize trephine group through 5 years after surgery. But the former had better BSCVA than the latter after 3 years of follow-up. At 5 years, mean BSCVA was 0.17 ± 0.10 logMAR in the same-size trephine group vs 0.25 ± 0.13 logMAR in the oversize trephine group (P = .03). The same-size trephine group had lower topographic power than the oversize trephine group after 3 years of follow-up. At 5 years, mean topographic power was 45.30 ± 2.28 diopters (D) in the same-size trephine group vs 46.75 ± 2.60 D in the oversize trephine group (P = .006). Eye axial lengths at 5 years were longer than those preoperatively as well as at 1 year follow-up after surgery in both groups. The same-size host and donor trephine could reduce late-stage myopic refractive errors for the patients with keratoconus after DALK. The mechanism may be late-stage axial length increase with time. Copyright © 2016 Elsevier Inc. All rights reserved.

Effect of the equivalent refractive index on intraocular lens power prediction with ray tracing after myopic laser in situ keratomileusis.

PubMed

Canovas, Carmen; van der Mooren, Marrie; Rosén, Robert; Piers, Patricia A; Wang, Li; Koch, Douglas D; Artal, Pablo

2015-05-01

To determine the impact of the equivalent refractive index (ERI) on intraocular lens (IOL) power prediction for eyes with previous myopic laser in situ keratomileusis (LASIK) using custom ray tracing. AMO B.V., Groningen, the Netherlands, and the Department of Ophthalmology, Baylor College of Medicine, Houston, Texas, USA. Retrospective data analysis. The ERI was calculated individually from the post-LASIK total corneal power. Two methods to account for the posterior corneal surface were tested; that is, calculation from pre-LASIK data or from post-LASIK data only. Four IOL power predictions were generated using a computer-based ray-tracing technique, including individual ERI results from both calculation methods, a mean ERI over the whole population, and the ERI for normal patients. For each patient, IOL power results calculated from the four predictions as well as those obtained with the Haigis-L were compared with the optimum IOL power calculated after cataract surgery. The study evaluated 25 patients. The mean and range of ERI values determined using post-LASIK data were similar to those determined from pre-LASIK data. Introducing individual or an average ERI in the ray-tracing IOL power calculation procedure resulted in mean IOL power errors that were not significantly different from zero. The ray-tracing procedure that includes an average ERI gave a greater percentage of eyes with an IOL power prediction error within ±0.5 diopter than the Haigis-L (84% versus 52%). For IOL power determination in post-LASIK patients, custom ray tracing including a modified ERI was an accurate procedure that exceeded the current standards for normal eyes. Copyright © 2015 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.

Biometry and spectral domain optical coherence tomography parameters in children with large cupping.

PubMed

Jung, Jong Jin; Baek, Seung-Hee; Kim, Ungsoo Samuel

2013-09-01

The purpose of this study is to investigate optic nerve head using spectral domain optical coherence tomography (SD-OCT) in children with large cupping. 111 eyes (4-10 years) were divided into three groups according to the cup to disc ratio: group 1, ≤0.3; group 2, 0.4-0.6; and group 3, ≥0.7. The rim area, disc area, average cup to disc ratio, vertical cup to disc ratio, and cup volume were investigated using SD-OCT (Cirrus HD-OCT, Carl Zeiss, Jena, Germany), and the axial length and anterior chamber depth (ACD) were measured by IOL master (IOL master 500, Carl Zeiss, Jena, Germany). Next, we compared ocular biometry and SD-OCT between the three groups. The mean age of group 1 was 6.48 ± 1.42 years, 7.00 ± 1.75 years in group 2, and 6.63 ± 1.82 years in group 3 (p = 0.370). A significant difference was seen in the spherical equivalent between the groups (p = 0.001). Group 2 had the most myopic refractive errors. As the cup to disc ratio increases, disc area, average cup to disc ratio, vertical cup to disc ratio, and cup volume increase significantly. When the results of ocular biometry and SD-OCT are adjusted for axial length, only disc area showed a significant correlation with cup to disc ratio (ACD: p = 0.473, rim area: p = 0.639, disc area: p = 0.005, and cup volume: p = 0.325). Axial length is the key factor determining disc size, which in turn is important for determining cup to disc ratio. Normal children with large cupping should be examined for axial length, myopic refractive errors, and disc size.

Constant light affects retinal dopamine levels and blocks deprivation myopia but not lens-induced refractive errors in chickens.

PubMed

Bartmann, M; Schaeffel, F; Hagel, G; Zrenner, E

1994-01-01

Chickens were raised with either translucent occluders or lenses, both under normal light cycles (12-h light/12-h dark) and in constant light (CL). Under normal light cycles, eyes with occluders became very myopic, and eyes with lenses became either relatively hyperopic (positive lenses) or myopic (negative lenses). After the treatment, retinal dopamine (DA), DOPAC, and serotonin levels were measured by high-pressure liquid chromatography (HPLC-EC). A significant drop in daytime retinal DOPAC (-20%) was observed after 1 week of deprivation, and in both DOPAC (-40%) and DA (-30%) after 2 weeks of deprivation. No changes in retinal serotonin levels were found. Retinal DA or DOPAC content remained unchanged after 2 or 4 days of lens wearing even though the lenses had already exerted their maximal effect on axial eye growth. When the chickens were raised in CL, development of deprivation myopia was reduced (8 days CL) or entirely blocked (13 days CL). Lens-induced changes in eye growth were not different after either 6 or 11 days in CL, compared to animals raised in a normal light cycle. Thirteen days of CL resulted in a dramatic reduction of DA and DOPAC levels, but serotonin levels were also lowered. The results suggest that lens-induced changes in refraction may not be dependent on dopaminergic pathways whereas deprivation myopia requires normal diurnal DA rhythms to develop.

Stabilization in early adult-onset myopia with corneal refractive therapy.

PubMed

González-Méijome, José M; Carracedo, Gonzalo; Lopes-Ferreira, Daniela; Faria-Ribeiro, Miguel A; Peixoto-de-Matos, Sofia C; Queirós, António

2016-02-01

To describe the stabilization of early adult-onset myopia in three university students after initiating orthokeratology treatment with corneal refractive therapy contact lenses. Three Caucasian early adult-onset progressing myopic subjects (1 male, 2 females) were fitted with corneal refractive therapy lenses to correct myopia between -1.50 and -2.50 D of sphere using Paragon CRT (Paragon Vision Sciences, Mesa, AZ) lenses for overnight orthokeratology. The pre-treatment refractive history from 2005 as well as refraction and axial length after treatment onset are reported over a period of 3 years between December 2009 and January 2013 with an additional year of follow-up after treatment discontinuation (January-December 2013). The peripheral refractive patterns and topographic changes are also reported individually. Treatment was successful in all three subjects achieving uncorrected visual acuity of 20/20 or better monocularly. During a period of 3 years of follow-up the subjects did not experience progression in their refractive error, nor in their axial length (measured during the last 2 years of treatment and 1 year after discontinuation). Furthermore, the subjects recovered to their baseline refraction and did not progressed further over the following year after lens wear discontinuation. We cannot attribute a causative effect to the orthokeratology treatment alone as underlying mechanism for myopia stabilization in this 3 patients. However, the present report points to the possibility of stabilization of early adult-onset myopia progression in young adults using corneal refractive therapy treatment. Copyright © 2015 Elsevier Ltd. All rights reserved.

Incidence and Outcomes of Optical Zone Enlargement and Recentration After Previous Myopic LASIK by Topography-Guided Custom Ablation.

PubMed

Reinstein, Dan Z; Archer, Timothy J; Carp, Glenn I; Stuart, Alastair J; Rowe, Elizabeth L; Nesbit, Andrew; Moore, Tara

2018-02-01

To report the incidence, visual and refractive outcomes, optical zone enlargement, and recentration using topography-guided CRS-Master TOSCA II software with the MEL 80 excimer laser (Carl Zeiss Meditec AG, Jena, Germany) after primary myopic laser refractive surgery. Retrospective analysis of 73 eyes (40 patients) with complaints of night vision disturbances due to either a decentration or small optical zone following a primary myopic laser refractive surgery procedure using the MEL 80 laser. Multiple ATLAS topography scans were imported into the CRS-Master software for topography-guided ablation planning. The topography-guided re-treatment procedure was performed as either a LASIK flap lift, a new LASIK flap, a side cut only, or photorefractive keratectomy. Axial curvature maps were analyzed using a fixed grid and set of concentric circles superimposed to measure the topographic optical zone diameter and centration. Follow-up was 12 months. The incidence of use in the population of myopic treatments during the study period was 0.79% (73 of 9,249). The optical zone diameter was increased by 11% from a mean of 5.65 to 6.32 mm, with a maximum change of 2 mm in one case. Topographic decentration was reduced by 64% from a mean of 0.58 to 0.21 mm. There was a 44% reduction in spherical aberration, 53% reduction in coma, and 39% reduction in total higher order aberrations. A subjective improvement in night vision symptoms was reported by 93%. Regarding efficacy, 82% of eyes reached 20/20 and 100% reached 20/32 (preoperative CDVA was 20/20 or better in 90%). Regarding safety, no eyes lost two lines of CDVA and 27% gained one line. Regarding predictability, 71% of re-treatments were within ±0.50 diopters. Topography-guided ablation was effective in enlarging the optical zone, recentering the optical zone, and reducing higher order aberrations. Topography-guided custom ablation appears to be an effective method for re-treatment procedures of symptomatic patients after myopic LASIK. [J Refract Surg. 2018;34(2):121-130.]. Copyright 2018, SLACK Incorporated.

Recent advances in corneal collagen cross-linking

PubMed Central

Sachdev, Gitansha Shreyas; Sachdev, Mahipal

2017-01-01

Corneal collagen cross-linking has become the preferred modality of treatment for corneal ectasia since its inception in late 1990s. Numerous studies have demonstrated the safety and efficacy of the conventional protocol. Our understanding of the cross-linking process is ever evolving, with its wide implications in the form of accelerated and pulsed protocols. Newer advancements in technology include various riboflavin formulations and the ability to deliver higher fluence protocols with customised irradiation patterns. A greater degree of customisation is likely the path forward, which will aim at achieving refractive improvements along with disease stability. The use of cross-linking for myopic correction is another avenue under exploration. Combination of half fluence cross-linking with refractive correction for high errors to prevent post LASIK regression is gaining interest. This review aims to highlight the various advancements in the cross-linking technology and its clinical applications. PMID:28905820

LASIK for Spherical Refractive Myopia: Effect of Topographic Astigmatism (Ocular Residual Astigmatism, ORA) on Refractive Outcome

PubMed Central

Frings, Andreas; Richard, Gisbert; Steinberg, Johannes; Skevas, Christos; Druchkiv, Vasyl; Katz, Toam; Linke, Stephan J.

2015-01-01

Purpose In eyes with a preoperative plano refractive cylinder, it would appear that there is no rationale for astigmatic treatment. The aim of this retrospective, cross-sectional data analysis was to determine the amount of topographic astigmatism in refractive plano eyes that results in reduced efficacy after myopic laser in situ keratomileusis (LASIK). Methods This study included 267 eyes from 267 consecutive myopic patients with a refractive plano cylinder. Receiver operating characteristic analysis was used to find the cut-off values of preoperative ocular residual astigmatism (= topographic astigmatism) that can best discriminate between groups of efficacy and safety indices in preoperative plano refractive cylinder eyes. Results Preoperative ocular residual astigmatism (ORA) (or topographic astigmatism) of ≤0.9 diopters (D) resulted in an efficacy index of at least 0.8 statistically significantly more frequently than eyes with a preoperative ORA of >0.9 D. Eyes with a high ORA preoperatively also had a high ORA postoperatively. Regression analysis showed that each diopter of preoperative ORA reduced efficacy by 0.07. Conclusion A preoperative corneal astigmatism of ≥0.9 D could (partially) be taken into account in the LASIK design, even if the subjective refractive astigmatism is neutral. PMID:25875476

Influence of refractive condition on retinal vasculature complexity in younger subjects.

PubMed

Azemin, Mohd Zulfaezal Che; Daud, Norsyazwani Mohamad; Ab Hamid, Fadilah; Zahari, Ilyanoon; Sapuan, Abdul Halim

2014-01-01

The aim of this study was to compare the retinal vasculature complexity between emmetropia, and myopia in younger subjects. A total of 82 patients (24.12 ± 1.25 years) with two types of refractive conditions, myopia and emmetropia were enrolled in this study. Refraction data were converted to spherical equivalent refraction. These retinal images (right eyes) were obtained from NAVIS Lite Image Filing System and the vasculature complexity was measured by fractal dimension (D f ), quantified using a computer software following a standardized protocol. There was a significant difference (P < 0.05) in the value of D f between emmetropic (1.5666 ± 0.0160) and myopic (1.5588 ± 0.0142) groups. A positive correlation (rho = 0.260, P < 0.05) between the D f and the spherical equivalent refraction was detected in this study. Using a linear model, it was estimated that 6.7% of the variation in D f could be explained by spherical equivalent refraction. This study provides valuable findings about the effect of moderate to high myopia on the fractal dimension of the retinal vasculature network. These results show that myopic refraction in younger subjects was associated with a decrease in D f , suggesting a loss of retinal vessel density with moderate to high myopia.

Visual Acuity and Over-refraction in Myopic Children Fitted with Soft Multifocal Contact Lenses.

PubMed

Schulle, Krystal L; Berntsen, David A; Sinnott, Loraine T; Bickle, Katherine M; Gostovic, Anita T; Pierce, Gilbert E; Jones-Jordan, Lisa A; Mutti, Donald O; Walline, Jeffrey J

2018-04-01

Practitioners fitting contact lenses for myopia control frequently question whether a myopic child can achieve good vision with a high-add multifocal. We demonstrate that visual acuity is not different than spectacles with a commercially available, center-distance soft multifocal contact lens (MFCL) (Biofinity Multifocal "D"; +2.50 D add). To determine the spherical over-refraction (SOR) necessary to obtain best-corrected visual acuity (BCVA) when fitting myopic children with a center-distance soft MFCL. Children (n = 294) aged 7 to 11 years with myopia (spherical component) of -0.75 to -5.00 diopters (D) (inclusive) and 1.00 D cylinder or less (corneal plane) were fitted bilaterally with +2.50 D add Biofinity "D" MFCLs. The initial MFCL power was the spherical equivalent of a standardized subjective refraction, rounded to the nearest 0.25 D step (corneal plane). An SOR was performed monocularly (each eye) to achieve BCVA. Binocular, high-contrast logMAR acuity was measured with manifest spectacle correction and MFCLs with over-refraction. Photopic pupil size was measured with a pupilometer. The mean (±SD) age was 10.3 ± 1.2 years, and the mean (±SD) SOR needed to achieve BCVA was OD: -0.61 ± 0.24 D/OS: -0.58 ± 0.27 D. There was no difference in binocular high-contrast visual acuity (logMAR) between spectacles (-0.01 ± 0.06) and best-corrected MFCLs (-0.01 ± 0.07) (P = .59). The mean (±SD) photopic pupil size (5.4 ± 0.7 mm) was not correlated with best MFCL correction or the over-refraction magnitude (both P ≥ .09). Children achieved BCVA with +2.50 D add MFCLs that was not different than with spectacles. Children typically required an over-refraction of -0.50 to -0.75 D to achieve BCVA. With a careful over-refraction, these +2.50 D add MFCLs provide good distance acuity, making them viable candidates for myopia control.

Spectacle compliance amongst rural secondary school children in Pune district, India

PubMed Central

Gogate, Parikshit; Mukhopadhyaya, Debapriya; Mahadik, Ashok; Naduvilath, Thomas J; Sane, Shrivallabh; Shinde, Amit; Holden, Brien

2013-01-01

Background: Refractive errors (RE) are the most common cause of avoidable visual impairment in children. But benefits of visual aids, which are means for correcting RE, depend on the compliance of visual aids by end users. Aim: To study the compliance of spectacle wear among rural school children in Pune district as part of the sarva siksha abhiyan (education for all scheme) after 6 - 12 months of providing free spectacles. Settings and Design: Cross-sectional follow-up study of rural secondary school children in western India. Materials and Methods: The students were examined by a team of optometrists who collected the demographic details, observed if the child was wearing the spectacles, and performed an ocular examination. The students were asked to give reasons for non-wear in a closed-ended questionnaire. Statistical Analysis: Chi-square test and multiple logistic regression used for data analysis. Results: Of the 2312 students who were dispensed spectacles in 2009, 1018 were re-examined in 2010. 523 students (51.4%) were female, the mean age was 12.1 years 300 (29.5%) were wearing their spectacles, 492 (68.5%) students claimed to have them at home while 211 (29.4%) reported not having them at all. Compliance of spectacle wear was positively associated to the magnitude of refractive error (P < 0.001), father's education (P = 0.016), female sex (P = 0.029) and negatively associated to the visual acuity of the better eye (P < 0.001) and area of residence (P < 0.0001). Of those that were examined and found to be myopic (N = 499), 220 (44%) wore their spectacles to examination. Factors associated with compliance to spectacle usage in the myopic population included increasing refractive error (P < 0.001), worsening visual acuity (P < 0.001), and higher academic performance (P < 0.001). The causes for not wearing spectacles were ‘lost spectacles’ 67(9.3%), ‘broken spectacles’ 125 (17.4%), ‘forgot spectacles at home’ 117 (16.3%), ‘uses spectacles sometimes’ 109 (15.2%), ‘teased about spectacles’ 142 (19.8%) and ‘do not like the spectacles’ 86 (12%). Conclusion: Spectacle compliance was poor amongst school children in rural Pune; many having significant vision loss as a result. PMID:23275214

Self-refraction, ready-made glasses and quality of life among rural myopic Chinese children: a non-inferiority randomized trial.

PubMed

Zhou, Zhongqiang; Chen, Tingting; Jin, Ling; Zheng, Dongxing; Chen, Shangji; He, Mingguang; Silver, Josh; Ellwein, Leon; Moore, Bruce; Congdon, Nathan G

2017-09-01

To study, for the first time, the effect of wearing ready-made glasses and glasses with power determined by self-refraction on children's quality of life. This is a randomized, double-masked non-inferiority trial. Children in grades 7 and 8 (age 12-15 years) in nine Chinese secondary schools, with presenting visual acuity (VA) ≤6/12 improved with refraction to ≥6/7.5 bilaterally, refractive error ≤-1.0 D and <2.0 D of anisometropia and astigmatism bilaterally, were randomized to receive ready-made spectacles (RM) or identical-appearing spectacles with power determined by: subjective cycloplegic retinoscopy by a university optometrist (U), a rural refractionist (R) or non-cycloplegic self-refraction (SR). Main study outcome was global score on the National Eye Institute Refractive Error Quality of Life-42 (NEI-RQL-42) after 2 months of wearing study glasses, comparing other groups with the U group, adjusting for baseline score. Only one child (0.18%) was excluded for anisometropia or astigmatism. A total of 426 eligible subjects (mean age 14.2 years, 84.5% without glasses at baseline) were allocated to U [103 (24.2%)], RM [113 (26.5%)], R [108 (25.4%)] and SR [102 (23.9%)] groups, respectively. Baseline and endline score data were available for 398 (93.4%) of subjects. In multiple regression models adjusting for baseline score, older age (p = 0.003) and baseline spectacle wear (p = 0.016), but not study group assignment, were significantly associated with lower final score. Quality of life wearing ready-mades or glasses based on self-refraction did not differ from that with cycloplegic refraction by an experienced optometrist in this non-inferiority trial. © 2016 Acta Ophthalmologica Scandinavica Foundation. Published by John Wiley & Sons Ltd.

Comparing aspheric ablation profile with standard corneal ablation for correction of myopia and myopic astigmatism, a contralateral eye study.

PubMed

Ghoreishi, Mohammad; Naderi Beni, Afsaneh; Naderi Beni, Zahra; Zandi, Alireza; Kianersi, Farzan

2017-12-01

The purpose of this study is to compare visual outcomes of myopic refractive surgery, using tissue saving (TS), a standard ablation profile by a Technolas 217z100, and aberration smart ablation (ASA), an aspheric algorithm by a MEL 80 excimer laser in two eyes of one patient. In this prospective interventional paired-eye controlled study, a total of 100 eyes of 50 participants with myopia with or without astigmatism underwent thin-flap Femto-LASIK, using a Femto LDV femtosecond laser (Ziemer Ophthalmic Systems AG, Port, Switzerland). For each patient, one eye was randomly treated with tissue-saving algorithm (TS group) by the Technolas 217z100 excimer laser and the other eye was treated with optimized smart ablation profile (ASA group) by the MEL 80 excimer laser. Outcome measures were uncorrected distance visual acuities (UDVAs), corrected distance visual acuities (CDVAs), manifest refraction, higher-order aberrations (HOAs), contrast sensitivity, and patient satisfaction 12 months after surgery. At 12 months postoperative, "45 subjects returned with mean" UDVA was - 0.02 ± 0.08 Logarithm of mean angle of resolution (LogMAR) for TS group and - 0.02 ± 0.09 LogMAR for ASA group (P = 0.91). Of the TS eyes, 42/45 (93.3%) and 32/45 (71.1%) were within ± 0.5 D and ± 0.25 D of target refraction, respectively, and of the ASA eyes, 41/45 (91.1%) and 30/45 (66.6%) were within ± 0.5 D and ± 0.25 D of target refraction, respectively. No statistically significant differences were observed between groups in HOAs changes and contrast sensitivity function. Aspheric and non-aspheric LASIKs using the two different excimer lasers provide similar results in myopic and myopic astigmatism patients.

Peripheral refraction with eye and head rotation with contact lenses.

PubMed

Lopes-Ferreira, Daniela P; Neves, Helena I F; Faria-Ribeiro, Miguel; Queirós, António; Fernandes, Paulo R B; González-Méijome, José M

2015-04-01

To evaluate the impact of eye and head rotation in the measurement of peripheral refraction with an open-field autorefractometer in myopic eyes wearing two different center-distance designs of multifocal contact lenses (MFCLs). Nineteen right eyes from 19 myopic patients (average central M ± SD = -2.67 ± 1.66 D) aged 20-27 years (mean ± SD = 23.2 ± 3.3 years) were evaluated using a Grand-Seiko autorefractometer. Patients were fitted with one multifocal aspheric center-distance contact lens (Biofinity Multifocal D(®)) and with one multi-concentric MFCL (Acuvue Oasys for Presbyopia). Axial and peripheral refraction were evaluated by eye rotation and by head rotation under naked eye condition and with each MFCL fitted randomly and in independent sessions. For the naked eye, refractive pattern (M, J0 and J45) across the central 60° of the horizontal visual field values did not show significant changes measured by rotating the eye or rotating the head (p > 0.05). Similar results were obtained wearing the Biofinity D, for both testing methods, no obtaining significant differences to M, J0 and J45 values (p > 0.05). For Acuvue Oasys for presbyopia, also no differences were found when comparing measurements obtained by eye and head rotation (p > 0.05). Multivariate analysis did not showed a significant interaction between testing method and lens type neither with measuring locations (MANOVA, p > 0.05). There were significant differences in M and J0 values between naked eyes and each MFCL. Measurements of peripheral refraction by rotating the eye or rotating the head in myopic patients wearing dominant design or multi-concentric multifocal silicone hydrogel contact lens are comparable. Copyright © 2014 British Contact Lens Association. Published by Elsevier Ltd. All rights reserved.

Determination Of Association Of Pigmentary Glaucoma With Pigment Dispersion Syndrome.

PubMed

Shah, Imtiaz Ali; Shah, Shujaat Ali; Nagdev, Partab Rai; Abbasi, Safdar Ali; Abbasi, Naeem Ali; Katpar, Safdar Akhtar

2017-01-01

Pigment Dispersion Syndrome (PDS) is an autosomal dominant disorder of white males between 20 to 40 years of age characterized by deposition of pigment on the lens, zonules of lens, trabecular meshwork and corneal endothelium (Krukenberg's spindle) in addition to radial, spoke like transillumination defects in the mid peripheral iris. This study was conducted to determine the frequency of occurrence of Pigmentary Glaucoma in patients with Pigment Dispersion Syndrome (PDS). This longitudinal follow up study included patients presenting with Krukenberg's spindle on the endothelial side of cornea and pigmentation of angle of anterior chamber seen on slit lamp examination and gonioscopy. Seventy-two cases of PDS were included in the study, amongst them 63 (87.50%) were males. Mean age was 35.00±6.54 years (range 24-46 years). Forty-seven (65.28%) patients had an IOP in the range of 10-14 mmHg, 22 (30.56%) patients had an IOP in the range of 15-18 mmHg and 3 (4.17%) patients developed an IOP of greater than 19 mmHg. Fundoscopy showed myopic degeneration in 49 (68.06%) patients and optic disc cupping in 3 (4.17%) patients. Four (5.56%) patients had refractive error between +1D to +3D, 9 (12.50%) patients had refractive error between -1D to -4D, 21 (29.17%) patients had refractive error between -5 D to -8 D and 38 (52.78%) patients had refractive error between -9 D to -12 D. Our study showed that one patient having PDS developed glaucoma at 5 years of follow up and three patients developed glaucoma at 14 years of follow up. On the basis of this study we conclude that early onset primary open angle glaucoma associated with PDS or Juvenile glaucoma associated with PDS might have been mistaken as Pigmentary Glaucoma in Pakistani patients and a distinct entity in the form of Pigmentary Glaucoma may be non-existent.

The early results of excimer laser photorefractive keratectomy for compound myopic astigmatism.

PubMed

Horgan, S E; Pearson, R V

1996-01-01

An excimer laser (VISX Twenty/Twenty Excimer Refractive System) was used to treat 51 eyes for myopia and astigmatism. Uncorrected pretreatment visual acuity was between 6/18 and 6/60 (log unit +0.45 to +1.0) in 59% and worse than 6/60 in 29%. The mean pretreatment spherical refractive error was -4.05 dioptre (range 1.25 to 13.25), and the mean pretreatment cylindrical error was -0.97 dioptre (range 0.25 to 4.00). Uncorrected visual acuity measured 6/6 or better (log unit 0.0 or less) in 80% at three months, and averaged 6/6 for all eyes at six months post-treatment, with 75% eyes obtaining 6/6 or better. The mean post-treatment spherical error decayed according to pre-treatment values, with a mean sphere of -0.20 dioptre for eyes initially less than -2.00 dioptre, -0.40 dioptre (for those between -2.25 and -3.00), -0.71 dioptre (for those between -4.25 and -5.00), and -1.15 dioptre for eyes initially above -6.25 dioptre. Vectored cylindrical correction exhibited response proportional to initial refraction, with a mean post-treatment cylinder of -1.83 dioptre for eyes formerly averaging -3.08 dioptre, -0.55 dioptre (eyes initially averaging -1.63 dioptre), and -0.51 dioptre (eyes initially averaging -0.67 dioptre). Vector analysis of post-treatment astigmatism showed 58% eyes exhibiting 51 or more degrees of axis shift, although 34% eyes remained within 20 degrees of their pretreatment axis. An effective reduction in spherocylindrical error was achieved with all eyes, although axis misalignment was a common event.

Accommodation, accommodative convergence, and response AC/A ratios before and at the onset of myopia in children.

PubMed

Gwiazda, Jane; Thorn, Frank; Held, Richard

2005-04-01

The purpose of this study was to investigate accommodation, accommodative convergence, and AC/A ratios before and at the onset of myopia in children. Refractive error, accommodation, and phorias were measured annually over a period of 3 years in 80 6- to 18-year-old children (mean age at first visit = 11.1 years), including 26 who acquired myopia of at least -0.50 D and 54 who remained emmetropic (-0.25 to + 0.75 D). Refraction was measured by noncycloplegic distance retinoscopy. Concomitant measures of accommodation and phorias were taken for letter targets at 4.0 m and 0.33 m using the Canon R-1 open field-of-view autorefractor with an attached motorized Risley prism and Maddox rod. The accommodation and phoria measurements were used to calculate response AC/A ratios. Compared with children who remained emmetropic, those who became myopic had elevated response AC/A ratios at 1 and 2 years before the onset of myopia, in addition to at onset and 1 year later (t's = -2.97 to -4.04, p < 0.01 at all times). The significantly higher AC/A ratios in the children who became myopic are a result of significantly reduced accommodation. Accommodative convergence was significantly greater in myopes only at onset. These findings suggest that the abnormal oculomotor factors found before the onset of myopia may contribute to myopigenesis by producing hyperopic retinal defocus when a child is engaged in near-viewing tasks.

Changes in the accommodation-convergence relationship after the Artisan phakic intraocular lens implantation for myopic patients.

PubMed

Ryu, Ik Hee; Han, Jinu; Lee, Hyung Keun; Kim, Jin Kook; Han, Sueng-Han

2014-04-01

To evaluate the change of accommodation-convergence parameters after implantation of Artisan phakic intraocular lens (PIOL). Prospective study for the patients with the Artisan PIOL implantation was performed. A total of 37 patients (3 males and 34 females) enrolled the study. Preoperatively, convergence amplitude, the stimulus accommodative convergence per unit of accommodation (AC/A) ratio and the near point of convergence (NPC) were evaluated. After the Artisan PIOL implantation, the identical evaluations were repeated at 1 week, 1, 3, and 6 months after the surgery. Mean age was 24.3 ± 4.8 years old, and preoperative refractive error was -8.92 ± 4.13 diopters (D). After the implantation, mean refractive errors significantly decreased to within ±1.00 D, and noticeable complications were not found. The convergence amplitude and the stimulus AC/A ratio increased 1 month after the surgery, but progressively stabilized afterward to near preoperative values. NPC didn't show any significant change over follow-up period up to 6 months. These results regarding implantation of the Artisan PIOL revealed the increase of accommodation-convergence relationship within first 1 month after the surgery, but progressive stabilization was noted during follow-up periods.

Lenticular accommodation in relation to ametropia: the chick model.

PubMed

Choh, Vivian; Sivak, Jacob G

2005-03-04

Our goal was to determine whether experimentally induced ametropias have an effect on lenticular accommodation and spherical aberration. Form-deprivation myopia and hyperopia were induced in one eye of hatchling chicks by application of a translucent goggle and +15 D lens, respectively. After 7 days, eyes were enucleated and lenses were optically scanned prior to accommodation, during accommodation, and after accommodation. Accommodation was induced by electrical stimulation of the ciliary nerve. Lenticular focal lengths for form-deprived eyes were significantly shorter than for their controls and accommodation-associated changes in focal length were significantly smaller in myopic eyes compared to their controls. For eyes imposed with +15 D blur, focal lengths were longer than those for their controls and accommodative changes were greater. Spherical aberration of the lens increased with accommodation in both form-deprived and lens-treated birds, but induction of ametropia had no effect on lenticular spherical aberration in general. Nonmonotonicity from lenticular spherical aberration increased during accommodation but effects of refractive error were equivocal. The crystalline lens contributes to refractive error changes of the eye both in the case of myopia and hyperopia. These changes are likely attributable to global changes in the size and shape of the eye.

The screening of visual impairment among preschool children in an urban population in Malaysia; the Kuching pediatric eye study: a cross sectional study

PubMed Central

2013-01-01

Background To screen for visual impairment in Malaysian preschool children. Methods Visual screening was conducted in 400 preschool children aged 4 to 6 years. The screening involved two basic procedures; the distant visual acuity test using the Sheridan Gardiner chart and the depth perception test using the Langs stereoacuity test. Criteria for referral were a visual acuity of 6/12 or less in the better eye or a fail in the depth perception test. Results The prevalence of visual impairment was 5% (95% confidence interval [CI] = 3.3, 7.6). Of the 400 preschool children screened, 20 of them failed the distant visual acuity test or the stereopsis test. Refractive errors were the most common cause of visual impairment (95%, 95% CI = 76.2, 98.8); myopic astigmatism was the commonest type of refractive error (63.2%, 95% CI = 40.8, 80.9). Conclusion The study is a small but important step in the effort to understand the problem of visual impairment among our preschool children. Our study showed that it is feasible to measure distant visual acuity and stereopsis in this age group. PMID:23601160

The screening of visual impairment among preschool children in an urban population in Malaysia; the Kuching pediatric eye study: a cross sectional study.

PubMed

Premsenthil, Mallika; Manju, Rose; Thanaraj, Asokumaran; Rahman, Syed Alwi Syed Abdul; Kah, Tan Aik

2013-04-19

To screen for visual impairment in Malaysian preschool children. Visual screening was conducted in 400 preschool children aged 4 to 6 years. The screening involved two basic procedures; the distant visual acuity test using the Sheridan Gardiner chart and the depth perception test using the Langs stereoacuity test. Criteria for referral were a visual acuity of 6/12 or less in the better eye or a fail in the depth perception test. The prevalence of visual impairment was 5% (95% confidence interval [CI] = 3.3, 7.6). Of the 400 preschool children screened, 20 of them failed the distant visual acuity test or the stereopsis test. Refractive errors were the most common cause of visual impairment (95%, 95% CI = 76.2, 98.8); myopic astigmatism was the commonest type of refractive error (63.2%, 95% CI = 40.8, 80.9). The study is a small but important step in the effort to understand the problem of visual impairment among our preschool children. Our study showed that it is feasible to measure distant visual acuity and stereopsis in this age group.

Modern Diagnostic Techniques for the Assessment of Ocular Blood Flow in Myopia: Current State of Knowledge.

PubMed

Grudzińska, Ewa; Modrzejewska, Monika

2018-01-01

Myopia is the most common refractive error and the subject of interest of various studies assessing ocular blood flow. Increasing refractive error and axial elongation of the eye result in the stretching and thinning of the scleral, choroid, and retinal tissues and the decrease in retinal vessel diameter, disturbing ocular blood flow. Local and systemic factors known to change ocular blood flow include glaucoma, medications and fluctuations in intraocular pressure, and metabolic parameters. Techniques and tools assessing ocular blood flow include, among others, laser Doppler flowmetry (LDF), retinal function imager (RFI), laser speckle contrast imaging (LSCI), magnetic resonance imaging (MRI), optical coherence tomography angiography (OCTA), pulsatile ocular blood flowmeter (POBF), fundus pulsation amplitude (FPA), colour Doppler imaging (CDI), and Doppler optical coherence tomography (DOCT). Many researchers consistently reported lower blood flow parameters in myopic eyes regardless of the used diagnostic method. It is unclear whether this is a primary change that causes secondary thinning of ocular tissues or quite the opposite; that is, the mechanical stretching of the eye wall reduces its thickness and causes a secondary lower demand of tissues for oxygen. This paper presents a review of studies assessing ocular blood flow in myopes.

Retinal Microvascular Network and Microcirculation Assessments in High Myopia.

PubMed

Li, Min; Yang, Ye; Jiang, Hong; Gregori, Giovanni; Roisman, Luiz; Zheng, Fang; Ke, Bilian; Qu, Dongyi; Wang, Jianhua

2017-02-01

To investigate the changes of the retinal microvascular network and microcirculation in high myopia. A cross-sectional, matched, comparative clinical study. Twenty eyes of 20 subjects with nonpathological high myopia (28 ± 5 years of age) with a refractive error of -6.31 ± 1.23 D (mean ± SD) and 20 eyes of 20 age- and sex-matched control subjects (30 ± 6 years of age) with a refractive error of -1.40 ± 1.00 D were recruited. Optical coherence tomography angiography (OCTA) was used to image the retinal microvascular network, which was later quantified by fractal analysis (box counting [D box ], representing vessel density) in both superficial and deep vascular plexuses. The Retinal Function Imager was used to image the retinal microvessel blood flow velocity (BFV). The BFV and microvascular density in the myopia group were corrected for ocular magnification using Bennett's formula. The density of both superficial and deep microvascular plexuses was significantly decreased in the myopia group in comparison to the controls (P < .05). The decrease of the microvessel density of the annular zone (0.6-2.5 mm), measured as D box , was 2.1% and 2.9% in the superficial and deep vascular plexuses, respectively. Microvessel density reached a plateau from 0.5 mm to 1.25 mm from the fovea in both groups, but that in the myopic group was about 3% lower than the control group. No significant differences were detected between the groups in retinal microvascular BFV in either arterioles or venules (P > .05). Microvascular densities in both superficial (r = -0.45, P = .047) and deep (r = -0.54, P = .01) vascular plexuses were negatively correlated with the axial lengths in the myopic eye. No correlations were observed between BFV and vessel density (P > .05). Retinal microvascular decrease was observed in the high myopia subjects, whereas the retinal microvessel BFV remained unchanged. The retinal microvascular network alteration may be attributed to ocular elongation that occurs with the progression of myopia. The novel quantitative analyses of the retinal microvasculature may help to characterize the underlying pathophysiology of myopia and enable early detection and prevention of myopic retinopathy. Copyright © 2016 Elsevier Inc. All rights reserved.

Different roles of retinal dopamine in albino Guinea pig myopia.

PubMed

Mao, Junfeng; Liu, Shuangzhen

2017-02-03

To investigate whether the different role of ocular dopamine was involved in the myopic development between spontaneous myopia (SM) and form deprivation myopia (FDM) in albino guinea pigs. 55 myopic animals were randomly divided into SM, Levodapa (L-DOPA), L-DOPA+carbidopa and vehicle. 70 non-myopic animals were randomly divided into normal control, FDM, L-DOPA+FDM, L-DOPA+carbidopa+FDM and vehicle. Once per day, for 14days, L-DOPA (10mg/kg) was injected intraperitoneally, and carbidopa (1μg) was injected at the same time into the peribulbar space of the right eye. Refractive parameters and dopamine content in neural retina and RPE/choroid complex were measured. In SM animals, high myopia was formed at 5 week of ages. L-DOPA treatment could reduce its myopic degree, and inhibit the increase of axial length and vitreous chamber depth with the increase of retinal dopamine in both eyes. Administration of carbidopa could prevent the increase of retinal dopamine induced by L-DOPA, but no influenced on its refractive state in the injected eyes. In non-SM animals, intraperitoneal L-DOPA could inhibit FDM, accompanied by the increase of retinal dopamine. Carbidopa treatment diminished the inhibition of FDM and prevented the increase in retinal dopamine by L-Dopa. Retinal dopamine was highly correlated with ocular refraction in FDM, but not in SM. There was no significant difference in dopamine content of RPE/choroid complex among all groups. The role of retinal dopamine was different between SM and FDM in albino guinea pigs. Although systemic L-DOPA could inhibit the development of SM and FDM, retinal dopamine was only involved in the L-DOPA inhibition on FDM, but not on SM. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

Refractive and ocular biometric profile of children with a history of laser treatment for retinopathy of prematurity.

PubMed

Kaur, Savleen; Sukhija, Jaspreet; Katoch, Deeksha; Sharma, Mansi; Samanta, Ramanuj; Dogra, Mangat R

2017-09-01

Indian children belong to a diverse socioeconomic strata with retinopathy of prematurity (ROP) developing in mature, higher birth weight babies as well. The purpose of our study is to analyze the long-term status of refractive errors and its relationship with ocular biometry in children with ROP who were laser treated at a tertiary center in North India. Cross sectional study. Children (<16 years) enrolled from January 2014 to December 2014 with a history of laser treatment for ROP and examined for refractive and biometric status. Thirty-six children presenting to us at the mean age of 7.37 ± 3.07 years (6-15 years) were included. Mean spherical equivalent (SE) was -4.05 D ± 5.10. 75% were myopic, with high astigmatism in 31%. Higher lens thickness (P = 0.03) and higher SE (P = 0.002) at 1 year postnatal age were predictors of larger SE. 79.4% achieved a favorable functional outcome (visual acuity ≥20/40). 5.88% achieved unsatisfactory outcome (<20/200) despite having a favorable structural outcome. There are a substantial number of children who develop myopia and high astigmatism while undergoing laser treatment for ROP. We found myopia in our cohort to be lenticular and greater axial length contributing to the development of high myopia. An initial large refractive error predicts the future development of myopia in these children. Nearly 6% of patients with good structural outcome have unexplained subnormal vision. Our threshold for prescribing glasses in these children should be low.

Refractive and ocular biometric profile of children with a history of laser treatment for retinopathy of prematurity

PubMed Central

Kaur, Savleen; Sukhija, Jaspreet; Katoch, Deeksha; Sharma, Mansi; Samanta, Ramanuj; Dogra, Mangat R

2017-01-01

Purpose: Indian children belong to a diverse socioeconomic strata with retinopathy of prematurity (ROP) developing in mature, higher birth weight babies as well. The purpose of our study is to analyze the long-term status of refractive errors and its relationship with ocular biometry in children with ROP who were laser treated at a tertiary center in North India. Methods: Cross sectional study. Children (<16 years) enrolled from January 2014 to December 2014 with a history of laser treatment for ROP and examined for refractive and biometric status. Results: Thirty-six children presenting to us at the mean age of 7.37 ± 3.07 years (6–15 years) were included. Mean spherical equivalent (SE) was −4.05 D ± 5.10. 75% were myopic, with high astigmatism in 31%. Higher lens thickness (P = 0.03) and higher SE (P = 0.002) at 1 year postnatal age were predictors of larger SE. 79.4% achieved a favorable functional outcome (visual acuity ≥20/40). 5.88% achieved unsatisfactory outcome (<20/200) despite having a favorable structural outcome. Conclusion: There are a substantial number of children who develop myopia and high astigmatism while undergoing laser treatment for ROP. We found myopia in our cohort to be lenticular and greater axial length contributing to the development of high myopia. An initial large refractive error predicts the future development of myopia in these children. Nearly 6% of patients with good structural outcome have unexplained subnormal vision. Our threshold for prescribing glasses in these children should be low. PMID:28905827

Change in refraction after lens-sparing vitrectomy for rhegmatogenous retinal detachment and epiretinal membrane.

PubMed

Iwase, Takeshi; Yamamoto, Kentaro; Yanagida, Kosei; Kobayashi, Misato; Ra, Eimei; Murotani, Kenta; Terasaki, Hiroko

2016-08-01

The aim of this study was to compare changes in refraction following lens-sparing vitrectomy between patients with rhegmatogenous retinal detachment (RRD) and epiretinal membrane (ERM) and to investigate factors associated with the change in refraction.We reviewed medical records of 49 eyes of 49 patients with RRD (53.6 ± 7.8 years, mean ± standard deviation) and 24 eyes of 24 patients with ERM (50.9 ± 15.7 years) who underwent lens-sparing vitrectomy. Spherical equivalent refractive power was evaluated before and up to 18 months after surgery. The relationship between the change in refraction and several parameters was evaluated.A significant progressive myopic shift in refractive power was observed after vitrectomy in operated RRD and ERM eyes (P < 0.001, P = 0.016, respectively), with no significant difference in fellow eyes. The refraction values observed at ≥3 and ≥12 months following vitrectomy were significantly different as compared with those observed at baseline in the RRD group (P < 0.001) and the ERM group (P < 0.05), respectively. The change in refraction between the RRD and ERM groups was significant (P = 0.030). The multiple linear regression analysis showed that only age was significantly correlated with the change in refraction in RRD (P = 0.018) and ERM (P < 0.001) groups. The change in refraction was significantly and positively correlated with age in RRD (r = -0.461, P = 0.001) and ERM (r = -0.687, P < 0.001) groups. Following lens-sparing vitrectomy, cataract surgery was performed on 30 eyes after 0.89 ± 0.26 years in the RRD group and on 10 eyes after 1.11 ± 0.14 years in the ERM group; there was a significant difference in time to cataract surgery between the groups (P = 0.007). Kaplan-Meier survival analysis demonstrated that there was a significant difference in the rate of cataract surgeries between the RRD and ERM groups (P = 0.022).Following lens-sparing vitrectomy for RRD and ERM, a progressive myopic shift in refraction owing to nuclear sclerosis was observed. Core vitrectomy itself would cause a myopic shift of refraction. The only risk factor associated with cataract progression following lens-sparing vitrectomy is age for both types of patients.

Change in refraction after lens-sparing vitrectomy for rhegmatogenous retinal detachment and epiretinal membrane

PubMed Central

Iwase, Takeshi; Yamamoto, Kentaro; Yanagida, Kosei; Kobayashi, Misato; Ra, Eimei; Murotani, Kenta; Terasaki, Hiroko

2016-01-01

Abstract The aim of this study was to compare changes in refraction following lens-sparing vitrectomy between patients with rhegmatogenous retinal detachment (RRD) and epiretinal membrane (ERM) and to investigate factors associated with the change in refraction. We reviewed medical records of 49 eyes of 49 patients with RRD (53.6 ± 7.8 years, mean ± standard deviation) and 24 eyes of 24 patients with ERM (50.9 ± 15.7 years) who underwent lens-sparing vitrectomy. Spherical equivalent refractive power was evaluated before and up to 18 months after surgery. The relationship between the change in refraction and several parameters was evaluated. A significant progressive myopic shift in refractive power was observed after vitrectomy in operated RRD and ERM eyes (P < 0.001, P = 0.016, respectively), with no significant difference in fellow eyes. The refraction values observed at ≥3 and ≥12 months following vitrectomy were significantly different as compared with those observed at baseline in the RRD group (P < 0.001) and the ERM group (P < 0.05), respectively. The change in refraction between the RRD and ERM groups was significant (P = 0.030). The multiple linear regression analysis showed that only age was significantly correlated with the change in refraction in RRD (P = 0.018) and ERM (P < 0.001) groups. The change in refraction was significantly and positively correlated with age in RRD (r = −0.461, P = 0.001) and ERM (r = −0.687, P < 0.001) groups. Following lens-sparing vitrectomy, cataract surgery was performed on 30 eyes after 0.89 ± 0.26 years in the RRD group and on 10 eyes after 1.11 ± 0.14 years in the ERM group; there was a significant difference in time to cataract surgery between the groups (P = 0.007). Kaplan–Meier survival analysis demonstrated that there was a significant difference in the rate of cataract surgeries between the RRD and ERM groups (P = 0.022). Following lens-sparing vitrectomy for RRD and ERM, a progressive myopic shift in refraction owing to nuclear sclerosis was observed. Core vitrectomy itself would cause a myopic shift of refraction. The only risk factor associated with cataract progression following lens-sparing vitrectomy is age for both types of patients. PMID:27512843

Myopic progression and dark focus variation in optometric students during the first academic year.

PubMed

Jiang, Bai-chuan; Schatz, Scott; Seger, Ken

2005-05-01

The aim of this research was to investigate the change in refractive error (RE) of optometric students during their first academic year and whether these changes relate to changes in their dark focus (DF). The RE and DF of 64 students were measured objectively every three months during the first academic year, a total of four times, using a Canon R-1 infrared optometer. Thirty-five of the 64 students had an additional RE and DF measurement three weeks immediately after their Summer vacation. Students completed a survey regarding the near work demands they experienced during the Winter break and the teaching semesters. Over nine months, the average RE of the students changed significantly from -2.22 +/- 1.93 (SD) D to -2.50 +/- 2.05 D (p = 0.0002). The rate of myopic progression averaged -0.37 dioptres per year. Inclusion of measurements taken on 35 students immediately after the Summer vacation showed that their change in RE during the Summer vacation was not significant (p = 0.79). For these subjects, the DF measured immediately after the vacation was significantly lower than the DF measured before the vacation (p = 0.007). The reduction in the DF after the vacations corresponded to a period of relative myopic stability in these subjects. The results of this study suggest that optometric students performing extensive near work are at risk of developing myopia. The variation of their DF values indicates the changing demand for near work during different periods of the year. After Winter and Summer vacations, the DF was lower and the myopic progression was suspended. These findings further support the notion that myopic progression is related to high near work demands and suggest that this progression can be slowed by a period of reduced near work, for example, vacation periods.

Functional outcome and patient satisfaction after laser in situ keratomileusis for correction of myopia and myopic astigmatism.

PubMed

Bamashmus, Mahfouth A; Hubaish, Khammash; Alawad, Mohammed; Alakhlee, Hisham

2015-01-01

The purpose was to evaluate subjective quality of vision and patient satisfaction after laser in situ keratomileusis (LASIK) for myopia and myopic astigmatism. A self-administered patient questionnaire consisting 29 items was prospectively administered to LASIK patients at the Yemen Magrabi Hospital. Seven scales covering specific aspects of the quality of vision were formulated including; global satisfaction; quality of uncorrected and corrected vision; quality of night vision; glare; daytime driving and; night driving. Main outcome measures were responses to individual questions and scale scores and correlations with clinical parameters. The scoring scale ranged from 1 (dissatisfied) to 3 (very satisfied) and was stratified in the following manner: 1-1.65 = dissatisfied; 1.66-2.33 = satisfied and; 2.33-3 = very satisfied. Data at 6 months postoperatively are reported. This study sample was comprised of 200 patients (122 females: 78 males) ranging in age from 18 to 46 years old. The preoperative myopic sphere was - 3.50 ± 1.70 D and myopic astigmatism was 0.90 ± 0.82 D. There were 96% of eyes within ± 1.00 D of the targeted correction. Postoperatively, the uncorrected visual acuity was 20/40 or better in 99% of eyes. The mean score for the overall satisfaction was 2.64 ± 0.8. A total of 98.5% of patients was satisfied or very satisfied with their surgery, 98.5% considered their main goal for surgery was achieved. Satisfaction with uncorrected vision was 2.5 ± 0.50. The main score for glare was 1.98 ± 0.7 at night. Night driving was rated more difficult preoperatively by 6.2%, whereas 79% had less difficulty driving at night. Patient satisfaction with uncorrected vision after LASIK for myopia and myopic astigmatism appears to be excellent and is related to the residual refractive error postoperatively.

Functional Outcome and Patient Satisfaction after Laser In Situ Keratomileusis for Correction of Myopia and Myopic Astigmatism

PubMed Central

Bamashmus, Mahfouth A.; Hubaish, Khammash; Alawad, Mohammed; Alakhlee, Hisham

2015-01-01

Purpose: The purpose was to evaluate subjective quality of vision and patient satisfaction after laser in situ keratomileusis (LASIK) for myopia and myopic astigmatism. Patients and Methods: A self-administered patient questionnaire consisting 29 items was prospectively administered to LASIK patients at the Yemen Magrabi Hospital. Seven scales covering specific aspects of the quality of vision were formulated including; global satisfaction; quality of uncorrected and corrected vision; quality of night vision; glare; daytime driving and; night driving. Main outcome measures were responses to individual questions and scale scores and correlations with clinical parameters. The scoring scale ranged from 1 (dissatisfied) to 3 (very satisfied) and was stratified in the following manner: 1-1.65 = dissatisfied; 1.66-2.33 = satisfied and; 2.33-3 = very satisfied. Data at 6 months postoperatively are reported. Results: This study sample was comprised of 200 patients (122 females: 78 males) ranging in age from 18 to 46 years old. The preoperative myopic sphere was − 3.50 ± 1.70 D and myopic astigmatism was 0.90 ± 0.82 D. There were 96% of eyes within ± 1.00 D of the targeted correction. Postoperatively, the uncorrected visual acuity was 20/40 or better in 99% of eyes. The mean score for the overall satisfaction was 2.64 ± 0.8. A total of 98.5% of patients was satisfied or very satisfied with their surgery, 98.5% considered their main goal for surgery was achieved. Satisfaction with uncorrected vision was 2.5 ± 0.50. The main score for glare was 1.98 ± 0.7 at night. Night driving was rated more difficult preoperatively by 6.2%, whereas 79% had less difficulty driving at night. Conclusion: Patient satisfaction with uncorrected vision after LASIK for myopia and myopic astigmatism appears to be excellent and is related to the residual refractive error postoperatively. PMID:25624684

Visual Activity before and after the Onset of Juvenile Myopia

PubMed Central

Jones-Jordan, Lisa A.; Mitchell, G. Lynn; Cotter, Susan A.; Kleinstein, Robert N.; Manny, Ruth E.; Mutti, Donald O.; Twelker, J. Daniel; Sims, Janene R.

2011-01-01

Purpose. To investigate visual activities before and after the onset of juvenile myopia. Methods. The subjects were 731 incident myopes (−0.75 D or more myopia on cycloplegic autorefraction in both meridians) and 587 emmetropes (between −0.25 and +1.00 D) in the Collaborative Longitudinal Evaluation of Ethnicity and Refractive Error (CLEERE) Study. Parents supplied visual activity data annually. Data from myopic children 5 years before through 5 years after myopia onset were compared to data from age-, sex-, and ethnicity-matched models of children who remained emmetropic. Results. Hours per week spent reading or using a computer/playing video games did not differ between the groups before myopia onset; however, hours per week for both activities were significantly greater in myopes than in emmetropes at onset and in 4 of the 5 years after onset by 0.7 to 1.6 hours per week. Hours per week spent in outdoor/sports activities were significantly fewer for children who became myopic 3 years before onset through 4 years after onset by 1.1 to 1.8 hours per week. Studying and TV watching were not significantly different before myopia onset. Conclusions. Before myopia onset, near work activities of future myopic children did not differ from those of emmetropes. Those who became myopic had fewer outdoor/sports activity hours than the emmetropes before, at, and after myopia onset. Myopia onset may influence children's near work behavior, but the lack of difference before onset argues against a major causative role for near work. Less outdoor/sports activity before myopia onset may exert a stronger influence on development than near work. PMID:20926821

Animal models in myopia research.

PubMed

Schaeffel, Frank; Feldkaemper, Marita

2015-11-01

Our current understanding of the development of refractive errors, in particular myopia, would be substantially limited had Wiesel and Raviola not discovered by accident that monkeys develop axial myopia as a result of deprivation of form vision. Similarly, if Josh Wallman and colleagues had not found that simple plastic goggles attached to the chicken eye generate large amounts of myopia, the chicken model would perhaps not have become such an important animal model. Contrary to previous assumptions about the mechanisms of myopia, these animal models suggested that eye growth is visually controlled locally by the retina, that an afferent connection to the brain is not essential and that emmetropisation uses more sophisticated cues than just the magnitude of retinal blur. While animal models have shown that the retina can determine the sign of defocus, the underlying mechanism is still not entirely clear. Animal models have also provided knowledge about the biochemical nature of the signal cascade converting the output of retinal image processing to changes in choroidal thickness and scleral growth; however, a critical question was, and still is, can the results from animal models be applied to myopia in children? While the basic findings from chickens appear applicable to monkeys, some fundamental questions remain. If eye growth is guided by visual feedback, why is myopic development not self-limiting? Why does undercorrection not arrest myopic progression even though positive lenses induce myopic defocus, which leads to the development of hyperopia in emmetropic animals? Why do some spectacle or contact lens designs reduce myopic progression and others not? It appears that some major differences exist between animals reared with imposed defocus and children treated with various optical corrections, although without the basic knowledge obtained from animal models, we would be lost in an abundance of untestable hypotheses concerning human myopia. © 2015 Optometry Australia.

Sex, eye size, and the rate of myopic eye growth due to form deprivation in outbred white leghorn chickens.

PubMed

Chen, Yen-Po; Prashar, Ankush; Hocking, Paul M; Erichsen, Jonathan T; To, Chi Ho; Schaeffel, Frank; Guggenheim, Jeremy A

2010-02-01

There is considerable variation in the degree of form-deprivation myopia (FDM) induced in chickens by a uniform treatment regimen. Sex and pretreatment eye size have been found to be predictive of the rate of FD-induced eye growth. Therefore, this study was undertaken to test whether the greater rate of myopic eye growth in males is a consequence of their larger eyes or of some other aspect of their sex. Monocular FDM was induced in 4-day-old White Leghorn chicks for 4 days. Changes in ocular component dimensions and refractive error were assessed by A-scan ultrasonography and retinoscopy, respectively. Sex identification of chicks was performed by DNA test. Relationships between traits were assessed by multiple regression. FD produced (mean +/- SD) 13.47 +/- 3.12 D of myopia and 0.47 +/- 0.14 mm of vitreous chamber elongation. The level of induced myopia was not significantly different between the sexes, but the males had larger eyes initially and showed greater myopic eye growth than did the females. In multiple linear regression analysis, the partial correlation between sex and the degree of induced eye growth remained significant (P = 0.008) after adjustment for eye size, whereas the partial correlation between initial eye size and the degree of induced eye growth was no longer significant after adjustment for sex (P = 0.11). After adjustment for other factors, the chicks' sex accounted for 6.4% of the variation in FD-induced vitreous chamber elongation. The sex of the chick influences the rate of experimentally induced myopic eye growth, independent of its effects on eye size.

Changes in higher order aberrations after wavefront-guided PRK for correction of low to moderate myopia and myopic astigmatism: two-year follow-up.

PubMed

Wigledowska-Promienska, D; Zawojska, I

2007-01-01

To assess efficacy, safety, and changes in higher order aberrations after wavefront-guided photorefractive keratectomy (PRK) in comparison with conventional PRK for low to moderate myopia with myopic astigmatism using a WASCA Workstation with the MEL 70 G-Scan excimer laser. A total of 126 myopic or myopic-astigmatic eyes of 112 patients were included in this retrospective study. Patients were divided into two groups: Group 1, the study group; and Group 2, the control group. Group 1 consisted of 78 eyes treated with wavefront-guided PRK. Group 2 consisted of 48 eyes treated with spherocylindrical conventional PRK. Two years postoperatively, in Group 1, 5% of eyes achieved an uncorrected visual acuity (UCVA) of 0.05; 69% achieved a UCVA of 0.00; 18% of eyes experienced enhanced visual acuity of -0.18 and 8% of -0.30. In Group 2, 8% of eyes achieved a UCVA of 0.1; 25% achieved a UCVA of 0.05; and 67% achieved a UCVA of 0.00 according to logMAR calculation method. Total higher-order root-mean square increased by a factor 1.18 for Group 1 and 1.6 for Group 2. There was a significant increase of coma by a factor 1.74 in Group 2 and spherical aberration by a factor 2.09 in Group 1 and 3.56 in Group 2. The data support the safety and effectiveness of the wavefront-guided PRK using a WASCA Workstation for correction of low to moderate refractive errors. This method reduced the number of higher order aberrations induced by excimer laser surgery and improved uncorrected and spectacle-corrected visual acuity when compared to conventional PRK.

Exposure to Sunlight Reduces the Risk of Myopia in Rhesus Monkeys

PubMed Central

Wang, Yong; Ding, Hui; Stell, William K.; Liu, Liangping; Li, Saiqun; Liu, Hongshan; Zhong, Xingwu

2015-01-01

Exposure to sunlight has recently been postulated as responsible for the effect that more time spent outdoors protects children from myopia, while early life exposure to natural light was reported to be possibly related to onset of myopia during childhood. In this study, we had two aims: to determine whether increasing natural light exposure has a protective effect on hyperopic defocus-induced myopia, and to observe whether early postnatal exposure to natural light causes increased risk of refractive error in adolescence. Eight rhesus monkeys (aged 20-30 days) were treated monocularly with hyperopic-defocus (-3.0D lens) and divided randomly into two groups: AL group (n=4), reared under Artificial (indoor) Lighting (08:00-20:00); and NL group (n=4), exposed to Natural (outdoor) Light for 3 hours per day (11:00-14:00), and to indoor lighting for the rest of the light phase. After being reared with lenses for ca. 190 days, all monkeys were returned to unrestricted vision until the age of 3 years. Another eight age-matched monkeys, reared with unrestricted vision under artificial lighting since birth, were employed as controls. The ocular refraction, corneal curvature and axial dimensions were measured before lens-wearing (at 23±3 days of age), monthly during the light phase, and at the age of puberty (at 1185+3 days of age). During the lens-wearing treatment, infant monkeys in the NL group were more hyperopic than those in the AL group (F=5.726, P=0.032). Furthermore, the two eyes of most NL monkeys remained isometropic, whereas 3 of 4 AL monkeys developed myopic anisometropia more than -2.0D. At adolescence, eyes of AL monkeys showed significant myopic anisometropia compared with eyes of NL monkeys (AL vs NL: -1.66±0.87D vs -0.22±0.44D; P=0.002) and controls (AL vs Control: -1.66±0.87D vs -0.05±0.85D; P<0.0001). All differences in refraction were associated with parallel changes in axial dimensions. Our results suggest that exposure to natural outdoor light might have an effect to reduced hyperopic defocus-induced myopia. Also, the data imply that early life exposure to sunlight may help to maintain normal development of emmetropization later in life, and thus lower the risk of myopic anisometropia in adolescent monkey. PMID:26030845

Myopia and radial keratotomy: a survey among Norwegian ophthalmologists.

PubMed

Midelfart, A

1990-10-01

One hundred and eighty-nine of 200 ophthalmologists in Norway responded to a survey requesting them to report their age, sex, refractive state, use of corrective lenses, and if myopic, their view on radial keratotomy as a possible method to correct their own myopia. According to the answers, 32 (17%) females and 154 (82%) males, with mean age of 49 years, were registered. The reported refractive state was 26.5% emmetropy and 72.0% ametropy. The prevalence of myopia was 45%. The mean refractive status (equivalent sphere) in the right eye was -1.02 +/- 2.28 D with a range from -8.5 D to +7.25 D (n = 184). Of the ametropes, 64.8% used spectacles, 15.3% used both spectacles and contact lenses, whilst 3.6% used only contact lenses for distance vision. With the exception of one, all myopes used corrective lenses. Only 2 myopic ophthalmologists responded positively to the question of whether they would consider having radial keratotomy to correct their own myopia.

Effect of Cycloplegia on Corneal Biometrics and Refractive State.

PubMed

Bagheri, Abbas; Feizi, Mohadeseh; Shafii, Aliakbar; Faramarzi, Amir; Tavakoli, Mehdi; Yazdani, Shahin

2018-01-01

To determine changes in refractive state and corneal parameters after cycloplegia with cyclopentolate hydrochloride 1% using a dual Scheimpflug imaging system. In this prospective cross-sectional study patients aged 10 to 40 years who were referred for optometric evaluation enrolled and underwent autorefraction and corneal imaging with the Galilei dual Scheimpflug system before and 30 minutes after twice instillation of medication. Changes in refraction and astigmatism were investigated. Corneal biometrics including anterior and posterior corneal curvatures, total corneal power and corneal pachymetry were compared before and after cycloplegia. Two hundred and twelve eyes of 106 subjects with mean age of 28 ± 5 years including 201 myopic and 11 hyperopic eyes were evaluated. Mean spherical equivalent refractive error before cycloplegia was -3.4 ± 2.6 D. A mean hyperopic shift of 0.4 ± 0.5 D occurred after cycloplegia ( P < 0.001). The astigmatism power did not significantly change ( P = 0.8), however, 26.8% of eyes with significant astigmatism experienced a change of more than 5 degrees in the axis of astigmatism. Changes in posterior corneal curvature were scant but statistically significant ( P = 0.001). Moreover, corneal thickness was slightly increased in the central and paracentral regions ( P < 0.001 and P < 0.001, respectively). Cycloplegia causes a hyperopic shift and astigmatism axis changes, along with an increase in central and paracentral corneal thickness and change in posterior corneal curvature. The effects of cycloplegia on refraction and corneal biometrics should be considered before cataract and refractive surgeries.

Outcome after treatment of ametropia with implantable contact lenses.

PubMed

Lackner, Birgit; Pieh, Stefan; Schmidinger, Gerald; Hanselmayer, Georg; Dejaco-Ruhswurm, Irene; Funovics, Martin A; Skorpik, Christian

2003-11-01

To evaluate long-term results after insertion of implantable contact lenses (ICLs) in phakic eyes. Prospective, noncomparative, interventional case series. Seventy-five phakic eyes (65 myopic, 10 hyperopic eyes) of 45 patients aged 21.7 to 60.6 years were included. STAAR Collamer Implantable Contact Lenses (STAAR Surgical Inc., Nidau, Switzerland) were implanted for correction of high myopia and hyperopia. Uncorrected visual acuity (UCVA), best-corrected visual acuity (BCVA), and intraocular pressure (IOP) were determined. Presence of lens opacification and the distance between the ICL and the crystalline lens were assessed by slit-lamp examination before surgery and at 1, 3, 6 months, and yearly after lens implantation. Preoperative mean spherical equivalent was -16.23+/-5.29 diopters (D) for myopic eyes and +7.88 +/-1.46 D for hyperopic eyes. After ICL implantation, mean residual refractive error was -1.77+/-2.17 D in myopic patients and +0.44+/-0.69 D in hyperopic patients. Preoperative mean UCVA was Snellen 0.03+/-0.03 for myopic patients and Snellen 0.12+/-0.16 for hyperopic patients. Preoperative mean BCVA was Snellen 0.49+/-0.23 for myopic patients and Snellen 0.82+/-0.23 for hyperopic patients. After ICL implantation, mean UCVA up to the end of individual observation time was Snellen 0.36+/-0.36 for myopic patients and Snellen 0.58+/-0.28 for hyperopic patients. Mean BCVA was Snellen 0.73+/-0.26 for myopic and Snellen 0.80+/-0.24 for hyperopic patients. Mean preoperative IOP was 14.2+/-2.7 mmHg, and mean postoperative IOP was 13.46+/-2.1 mmHg over all follow-up investigations. The main complication was the development of subcapsular anterior opacifications of the crystalline lens in 25 eyes (33.3%), 2 of which showed direct contact to the ICL. Eleven eyes (14.7%) were stable in opacification and 14 eyes (18.7%) had progressive opacifications. The median time to opacification was 27.1 months. In 8 patients (10.7%), the subjective visual impairment mandated cataract surgery. The most significant long-term complication after ICL implantation is the formation of opacifications of the crystalline lens with the risk of the necessity of subsequent cataract surgery (10.7%). Old age, female gender, and contralateral opacification are independent significant risk factors for early formation of opacifications in this patient group.

Effect of Amblyopia Treatment on Macular Thickness in Eyes With Myopic Anisometropic Amblyopia.

PubMed

Pang, Yi; Frantz, Kelly A; Block, Sandra; Goodfellow, Geoffrey W; Allison, Christine

2015-04-01

To determine whether abnormal macular thickness in myopic anisometropic amblyopia differed after amblyopia treatment. Furthermore, to investigate whether effect of treatment on macular thickness was associated with subject age or improvement in stereoacuity. Seventeen children (mean age: 9.0 [±3.0] years, ranging from 5.7-13.9 years) with myopic anisometropic amblyopia (visual acuity [VA] in amblyopic eyes: 20/80-20/400) were recruited and treated with 16-week refractive correction, followed by an additional 16-week refractive correction and patching. Macular thickness, best-corrected VA, and stereoacuity were measured both before and after amblyopia treatment. Factorial repeated-measures analysis of variance was performed to determine whether macular thickness in amblyopic eyes changed after amblyopia treatment. Mean baseline VA in the amblyopic eye was 1.0 ± 0.3 logMAR and improved to 0.7 ± 0.3 after amblyopia treatment (P < 0.0001). The interaction between eye and amblyopia treatment was statistically significant for average foveal thickness (P = 0.040). There was no treatment effect on fellow eyes (P = 0.245); however, the average foveal thickness in the amblyopic eye was significantly reduced after amblyopia treatment (P = 0.049). No statistically significant interactions were found for the other macular thickness parameters (P > 0.05). Abnormal central macula associated with myopic anisometropic amblyopia tended to be thinner following amblyopia treatment with no significant changes in peripheral macular thickness.

How predictable are the results of excimer laser photorefractive keratectomy? A review.

PubMed

Grosvenor, T

1995-10-01

At the close of 1994, the AOA News reported that at least 14 companies were preparing to market equipment for excimer laser photorefractive keratectomy (PRK). More than a dozen PRK centers had been formed for the purpose of recruiting optometrists to co-manage PRK patients. Because the surgery is a "no-touch" computer-driven procedure whose duration is measured in seconds, the preoperative and postoperative care of PRK patients will assume major importance. Optometrists who will be asked to take part in the management of PRK patients must be able to counsel patients on matters such as the predictability of the procedure in terms of postoperative refractive error and visual acuity, as well as the possibility of unintended consequences such as difficulty in night driving. Information currently available, mainly as a result of studies conducted in other countries, shows that the results of PRK are highly predictable for preoperative myopia up to about -3.00 D and somewhat less predictable for myopia between -3.00 and -6.00 D, whereas for myopia greater than -6.00 D the probability of achieving a full correction decreases rapidly with increasing amounts of myopia. As compared to radial keratotomy (RK) in which the postoperative refractive error drifts relentlessly in the hyperopic direction, PRK brings about an initial hyperopic shift followed by regression leading to increasing myopia. Researchers disagree on the cause of the postoperative hyperopic shift and regression, and on the value of various methods of controlling regression including the use of wider and deeper ablation profiles and the postoperative use of corticosteroids and nonsteroid anti-inflammatory drugs. It is too early to determine whether the myopic creep in PRK will be as persistent as the hyperopic creep in RK, but it is likely that whereas presbyopic post-RK patients may have adequate distance vision but require corrective lenses for reading, presbyopic post-PRK patients may be sufficiently myopic to require lenses for distance vision but not for reading.

Optical Coherence Tomography–Based Corneal Power Measurement and Intraocular Lens Power Calculation Following Laser Vision Correction (An American Ophthalmological Society Thesis)

PubMed Central

Huang, David; Tang, Maolong; Wang, Li; Zhang, Xinbo; Armour, Rebecca L.; Gattey, Devin M.; Lombardi, Lorinna H.; Koch, Douglas D.

2013-01-01

Purpose: To use optical coherence tomography (OCT) to measure corneal power and improve the selection of intraocular lens (IOL) power in cataract surgeries after laser vision correction. Methods: Patients with previous myopic laser vision corrections were enrolled in this prospective study from two eye centers. Corneal thickness and power were measured by Fourier-domain OCT. Axial length, anterior chamber depth, and automated keratometry were measured by a partial coherence interferometer. An OCT-based IOL formula was developed. The mean absolute error of the OCT-based formula in predicting postoperative refraction was compared to two regression-based IOL formulae for eyes with previous laser vision correction. Results: Forty-six eyes of 46 patients all had uncomplicated cataract surgery with monofocal IOL implantation. The mean arithmetic prediction error of postoperative refraction was 0.05 ± 0.65 diopter (D) for the OCT formula, 0.14 ± 0.83 D for the Haigis-L formula, and 0.24 ± 0.82 D for the no-history Shammas-PL formula. The mean absolute error was 0.50 D for OCT compared to a mean absolute error of 0.67 D for Haigis-L and 0.67 D for Shammas-PL. The adjusted mean absolute error (average prediction error removed) was 0.49 D for OCT, 0.65 D for Haigis-L (P=.031), and 0.62 D for Shammas-PL (P=.044). For OCT, 61% of the eyes were within 0.5 D of prediction error, whereas 46% were within 0.5 D for both Haigis-L and Shammas-PL (P=.034). Conclusions: The predictive accuracy of OCT-based IOL power calculation was better than Haigis-L and Shammas-PL formulas in eyes after laser vision correction. PMID:24167323

Wavefront-optimized laser in situ keratomileusis with the Allegretto Wave Eye-Q excimer laser and the FEMTO LDV Crystal Line femtosecond laser: 6 month visual and refractive results.

PubMed

Ziaei, Mohammed; Mearza, Ali A; Allamby, David

2015-08-01

To present the first reported series of patients undergoing myopic LASIK with the FEMTO LDV Crystal Line femtosecond laser and the WaveLight Allegretto Eye-Q excimer laser. We report the uncorrected and corrected distance visual acuity (UDVA and CDVA), refractive predictability, efficacy and safety of laser in situ keratomileusis (LASIK) performed with the above laser platforms. This prospective interventional case series study evaluated consecutive eyes with low to moderate myopic astigmatism that underwent LASIK with the FEMTO LDV Crystal Line femtosecond laser and the WaveLight Allegretto Eye-Q 400 Hz excimer laser. Visual and refractive changes as well as complications were evaluated after wavefront-optimized laser treatment. Four hundred and forty four patients (887 eyes) reached the 6-month time gate. Mean age at time of procedure was 31 years (range: 20-59). Mean pre-op spherical-equivalent (SE) was -3.44 diopters (D)±1.34D (range: -0.50 to -7.00) whilst the postoperative spherical equivalent decreased to -0.08±0.31D (range -2.25 to 1.00). At 6-month follow up, 96.9% of patients had monocular uncorrected distance visual acuity of 20/20 or better with 95.2% of patients within ±0.5D of intended refractive outcome. All patients achieved 20/20 binocular distance uncorrected visual acuity. No significant intra-operative or postoperative complications were encountered during the 6-month follow-up period. The combination of the above laser platforms provides safe, effective and predictable results in correcting compound myopic astigmatism with excellent visual outcomes. Copyright © 2015 British Contact Lens Association. Published by Elsevier Ltd. All rights reserved.

Excimer laser photorefractive surgery of the cornea

NASA Astrophysics Data System (ADS)

Gaster, Ronald N.

1998-09-01

The 193 nm argon fluoride (ArF) excimer laser can effectively be used to change the radius of curvature of the cornea and thus alter the refractive state of the eye. This change allows myopic (nearsighted) patients to see well with less dependence on glasses or contact lenses. The two major techniques of laser refractive surgery currently in effect in the United States are photorefractive keratectomy (PRK) and laser in situ keratomileusis (LASIK). This paper will discuss these refractive cornea surgical techniques.

Internal Astigmatism in Myopes and Non-myopes: Compensation or Constant?

PubMed Central

Manny, Ruth E.; Deng, Li; Gwiazda, Jane; Hyman, Leslie; Weissberg, Erik; Scheiman, Mitchell; Fern, Karen D.

2016-01-01

Purpose To examine internal astigmatism (IA) in myopes and non-myopes using a new method to assess compensation of corneal astigmatism (CA) by IA, to look for predictors of high IA in young adult myopes and determine if as CA changes IA changes to reduce refractive astigmatism (RA) in an active compensatory process in myopes. Methods Right eye keratometry and cycloplegic autorefraction were measured annually over 14 years in 367 myopes and once in 204 non-myopes age- (mean 21.91 years ± 1.47), gender-, and ethnicity-matched to myopes at year 12. CA and RA at the corneal plane were expressed as J0, J45. IA = RA - CA. Inverse power transformation provided cylinder power and axis of IA for the compensation factor (IA/CA). Analyses included: 1) paired and unpaired t-tests (refractive data), 2) chi-square tests (distributions of compensation factor), 3) logistic regression analysis (predictors of high IA), and 4) linear mixed models (time effect on RA, CA and IA). Results The magnitude of IAJ0 varied by refractive error (myopes −0.25 ±0.24 vs non-myopes −0.32 ± 0.21, p<0.001). Compensation of CA by IA was poorer in myopes than non-myopes (χ2 p<0.001). When matched by CA, compensation remained poorer in myopes than non-myopes (χ2 all p≤ 0.04). Within each refractive group compensation was better when CA was low than high (χ2 p<0.001). When CA was low in myopes, high IA (≥1.00D) was less likely (p=0.01). Longitudinal follow-up of myopes found no evidence for an active compensatory role for IA as CA increased over time. There were differences in IAJ0 by ethnicity over time (p<0.0001). Conclusions In myopic and non-myopic eyes with low amounts of CA, IA may reduce CA’s contribution to RA, but IA is not a constant. However, there is no evidence for an active compensatory role for IA reducing CA in myopes. PMID:27564515

The Effects of the Relative Strength of Simultaneous Competing Defocus Signals on Emmetropization in Infant Rhesus Monkeys

PubMed Central

Arumugam, Baskar; Hung, Li-Fang; To, Chi-Ho; Sankaridurg, Padmaja; III, Earl L. Smith

2016-01-01

Purpose We investigated how the relative surface area devoted to the more positive-powered component in dual-focus lenses influences emmetropization in rhesus monkeys. Methods From 3 to 21 weeks of age, macaques were reared with binocular dual-focus spectacles. The treatment lenses had central 2-mm zones of zero-power and concentric annular zones that had alternating powers of either +3.0 diopters (D) and 0 D (+3 D/pL) or −3.0 D and 0 D (−3 D/pL). The relative widths of the powered and plano zones varied from 50:50 to 18:82 between treatment groups. Refractive status, corneal curvature, and axial dimensions were assessed biweekly throughout the lens-rearing period. Comparison data were obtained from monkeys reared with binocular full-field single-vision lenses (FF+3D, n = 6; FF−3D, n = 10) and from 35 normal controls. Results The median refractive errors for all of the +3 D/pL lens groups were similar to that for the FF+3D group (+4.63 D versus +4.31 D to +5.25 D; P = 0.18–0.96), but significantly more hyperopic than that for controls (+2.44 D; P = 0.0002–0.003). In the −3 D/pL monkeys, refractive development was dominated by the zero-powered portions of the treatment lenses; the −3 D/pL animals (+2.94 D to +3.13 D) were more hyperopic than the FF−3D monkeys (−0.78 D; P = 0.004–0.006), but similar to controls (+2.44 D; P = 0.14–0.22). Conclusions The results demonstrate that even when the more positive-powered zones make up only one-fifth of a dual-focus lens' surface area, refractive development is still dominated by relative myopic defocus. Overall, the results emphasize that myopic defocus distributed across the visual field evokes strong signals to slow eye growth in primates. PMID:27479812

Small incision lenticule extraction (SMILE) in the correction of myopic astigmatism: outcomes and limitations - an update.

PubMed

Alió Del Barrio, Jorge L; Vargas, Verónica; Al-Shymali, Olena; Alió, Jorge L

2017-01-01

Small Incision Lenticule Extraction (SMILE) is a flap-free intrastromal technique for the correction of myopia and myopic astigmatism. To date, this technique lacks automated centration and cyclotorsion control, so several concerns have been raised regarding its capability to correct moderate or high levels of astigmatism. The objective of this paper is to review the reported SMILE outcomes for the correction of myopic astigmatism associated with a cylinder over 0.75 D, and its comparison with the outcomes reported with the excimer laser-based corneal refractive surgery techniques. A total of five studies clearly reporting SMILE astigmatic outcomes were identified. SMILE shows acceptable outcomes for the correction of myopic astigmatism, although a general agreement exists about the superiority of the excimer laser-based techniques for low to moderate levels of astigmatism. Manual correction of the static cyclotorsion should be adopted for any SMILE astigmatic correction over 0.75 D.

Both the central and peripheral retina contribute to myopia development in chicks.

PubMed

Wang, Jian Chao; Chun, Rachel K M; Zhou, Yun Y; Zuo, Bing; Li, King Kit; Liu, Quan; To, Chi Ho

2015-11-01

This study examined the contribution of the central and peripheral retina to the development of form deprivation myopia in chicks. Chicks were treated for 7 days either with centrally form-deprived (CFD) lenses of 2/4/6/8 mm diameter central diffuse zone, or a full size diffuser lens on their right eyes. The left eyes wore a full field plano lens. Axial dimensions and refractions were measured before and after 4 and 7 days of lens wear. All eyes that had worn CFD lenses of 2/4/6/8 mm had significant changes in refractive errors (from -2.69 ± 0.40 D to -6.13 ± 0.76 D, p < 0.05), vitreous chamber depth (from 0.19 ± 0.04 mm to 0.56 ± 0.04 mm, p < 0.05) and axial length (from 0.42 ± 0.03 mm to 0.96 ± 0.04 mm, p < 0.05) during the experiment, except for the changes in refractive error (-2.81 ± 0.33 D, p = 0.053) and axial length (0.77 ± 0.04 mm, p = 0.050) in the 2 mm lens group after 7 days of lens wear. The myopic shift in the CFD lens wearing eyes was due primarily to an increase in vitreous chamber depth. Linear regression analysis showed that the changes of refractive error, vitreous chamber depth and axial length were positively correlated with the size of central form-deprived retina. Form depriving the central retina produced axial myopia even in the presence of clear peripheral vision. The current study showed that both the central and peripheral retina contributes to myopia development in chicks. The amount of myopia induced increased linearly with the area of retina being form-deprived. It suggests that in terms of decoding optical input for growth, the area of retina being exposed to optical signals may be critical in determining eye growth. © 2015 The Authors Ophthalmic & Physiological Optics © 2015 The College of Optometrists.

Refractive errors and ocular biometry components in thalassemia major patients.

PubMed

Heydarian, Samira; Jafari, Reza; Karami, Hosein

2016-04-01

The aim of this study is to determine and compare biometric and refractive characteristics of thalassemia major patients and normal individuals. In this cross-sectional study, 54 thalassemia major patients were selected randomly as case group, and 54 age- and sex-matched healthy subjects were regarded as control group. Refractive errors, corneal curvature and ocular components were measured by autokeratorefractometery and A-scan ultrasonography, respectively. Mean spherical equivalent was -0.0093 ± 0.86 D in thalassemia patients and -0.22 ± 1.33 D in the normal group. The prevalence of myopia, Hyperopia, and emmetropia among thalassemia patients was 16.7, 19.4, and 63.9 %, respectively. While in the control group, 26.9 % were myopic, 25 % were hyperopic, and 48.1 % were emmetropic. The prevalence of astigmatism in case group was 22.2 %, which was not significantly different from that in control group, (27.8 %, p = 0.346). Mean axial length in thalassemia patients was 22.89 ± 0.70 which was significantly lower than that in normal group (23.37 ± 0.91, p = 0.000). The flattest meridian of the cornea (R1) was significantly steeper in thalassemia patients (7.77 ± 0.24) in comparison to normal individuals (7.85 ± 0.28). Although thalassemic patients had significantly smaller axial length and vitreous chamber depth in comparison to normal group, which could be due to their abnormal physical growth, there was no significant difference between the mean of spherical equivalent among two groups. This can be due to their steeper corneal curvature that overcomes the refractive disadvantage of their shorter axial length.

Changes in the Accommodation-convergence Relationship after the Artisan Phakic Intraocular Lens Implantation for Myopic Patients

PubMed Central

Ryu, Ik Hee; Han, Jinu; Lee, Hyung Keun; Kim, Jin Kook

2014-01-01

Purpose To evaluate the change of accommodation-convergence parameters after implantation of Artisan phakic intraocular lens (PIOL). Methods Prospective study for the patients with the Artisan PIOL implantation was performed. A total of 37 patients (3 males and 34 females) enrolled the study. Preoperatively, convergence amplitude, the stimulus accommodative convergence per unit of accommodation (AC/A) ratio and the near point of convergence (NPC) were evaluated. After the Artisan PIOL implantation, the identical evaluations were repeated at 1 week, 1, 3, and 6 months after the surgery. Results Mean age was 24.3 ± 4.8 years old, and preoperative refractive error was -8.92 ± 4.13 diopters (D). After the implantation, mean refractive errors significantly decreased to within ±1.00 D, and noticeable complications were not found. The convergence amplitude and the stimulus AC/A ratio increased 1 month after the surgery, but progressively stabilized afterward to near preoperative values. NPC didn't show any significant change over follow-up period up to 6 months. Conclusions These results regarding implantation of the Artisan PIOL revealed the increase of accommodation-convergence relationship within first 1 month after the surgery, but progressive stabilization was noted during follow-up periods. PMID:24688257

Exome Sequence Analysis of 14 Families With High Myopia.

PubMed

Kloss, Bethany A; Tompson, Stuart W; Whisenhunt, Kristina N; Quow, Krystina L; Huang, Samuel J; Pavelec, Derek M; Rosenberg, Thomas; Young, Terri L

2017-04-01

To identify causal gene mutations in 14 families with autosomal dominant (AD) high myopia using exome sequencing. Select individuals from 14 large Caucasian families with high myopia were exome sequenced. Gene variants were filtered to identify potential pathogenic changes. Sanger sequencing was used to confirm variants in original DNA, and to test for disease cosegregation in additional family members. Candidate genes and chromosomal loci previously associated with myopic refractive error and its endophenotypes were comprehensively screened. In 14 high myopia families, we identified 73 rare and 31 novel gene variants as candidates for pathogenicity. In seven of these families, two of the novel and eight of the rare variants were within known myopia loci. A total of 104 heterozygous nonsynonymous rare variants in 104 genes were identified in 10 out of 14 probands. Each variant cosegregated with affection status. No rare variants were identified in genes known to cause myopia or in genes closest to published genome-wide association study association signals for refractive error or its endophenotypes. Whole exome sequencing was performed to determine gene variants implicated in the pathogenesis of AD high myopia. This study provides new genes for consideration in the pathogenesis of high myopia, and may aid in the development of genetic profiling of those at greatest risk for attendant ocular morbidities of this disorder.

Utility of an open field Shack-Hartmann aberrometer for measurement of refractive error in infants and young children

PubMed Central

Harvey, Erin M.; Miller, Joseph M.; Schwiegerling, Jim

2013-01-01

PURPOSE To assess the utility of an open-field Shack-Hartmann aberrometer for measurement of refractive error without cycloplegia in infants and young children. METHOD Data included 2698 subject encounters with Native American infants and children aged 6 months to <8 years. We attempted right eye measurements without cycloplegia using the pediatric wavefront evaluator (PeWE) on all participants while they viewed near (50 cm) and distant (2 m) fixation targets. Cycloplegic autorefraction (Rmax [Nikon Retinomax K-plus2]) measurements were obtained for children aged ≥3 years. RESULTS The success rates of noncycloplegic PeWE measurement for near (70%) and distant targets (56%) significantly improved with age. Significant differences in mean spherical equivalent (M) across near versus distant fixation target conditions were consistent with the difference in accommodative demand. Differences in astigmatism measurements for near versus distant target conditions were not clinically significant. Noncycloplegic PeWE and cycloplegic Rmax measurements of M and astigmatism were strongly correlated. Mean noncycloplegic PeWE M was significantly more myopic or less hyperopic and astigmatism measurements tended to be greater in magnitude compared with cycloplegic Rmax. CONCLUSIONS The PeWE tended to overestimate myopia and underestimate hyperopia when cycloplegia was not used. The PeWE is useful for measuring accommodation and astigmatism. PMID:24160970

Factors Affecting Long-term Myopic Regression after Laser In Situ Keratomileusis and Laser-assisted Subepithelial Keratectomy for Moderate Myopia.

PubMed

Lim, Sung A; Park, Yooyeon; Cheong, Yu Jin; Na, Kyung Sun; Joo, Choun-Ki

2016-04-01

High myopia is known to be a risk factor for long-term regression after laser refractive surgery. There have been few studies about the correction of moderate myopias that did not need retreatment after long-term follow-up. We evaluated 10 years of change in visual acuity and refractive power in eyes with moderate myopia after laser refractive surgery. We included patients that had undergone laser in situ keratomileusis (LASIK) or laser-assisted subepithelial keratectomy (LASEK) to correct their myopia and that had at least 10 years of follow-up. We evaluated the stability of visual acuity in terms of safety, efficacy, and refractive changes at examinations 6 months and 1, 2, 5, 7, and 10 years after surgery. The study evaluated 62 eyes (36 eyes in LASIK patients and 26 eyes in LASEK patients). In both groups, the efficacy index tended to decrease, and it was consistently higher in the LASEK group compared to the LASIK group over the 10 years of follow-up. The safety index improved over 10 years and was always higher than 0.9 in both groups. The difference between the spherical equivalent at 6 months postoperatively and later periods was statistically significant after 5, 7, and 10 years in both groups (LASIK, p = 0.036, p = 0.003, and p < 0.001, respectively; LASEK, p = 0.006, p = 0.002, and p = 0.001, respectively). Ten years after surgery,26 eyes (66.7%) in the LASIK group and 19 eyes (73.1%) in the LASEK group had myopia greater than 1 diopter. In comparison with the thickness at 6 months postoperatively, central corneal thickness was significantly increased after 5, 7, and 10 years in both LASIK and LASEK groups (LASIK, p < 0.001, p < 0.001, and p < 0.001, respectively; LASEK, p = 0.01, p < 0.001, and p < 0.001, respectively). Moderately myopic eyes showed progressive myopic shifting and corneal thickening after LASIK and LASEK during 10 years of follow-up. We also found that early refractive regression may indicate the long-term refractive outcome.

Factors Affecting Long-term Myopic Regression after Laser In Situ Keratomileusis and Laser-assisted Subepithelial Keratectomy for Moderate Myopia

PubMed Central

Lim, Sung A; Park, Yooyeon; Cheong, Yu Jin; Na, Kyung Sun

2016-01-01

Purpose High myopia is known to be a risk factor for long-term regression after laser refractive surgery. There have been few studies about the correction of moderate myopias that did not need retreatment after long-term follow-up. We evaluated 10 years of change in visual acuity and refractive power in eyes with moderate myopia after laser refractive surgery. Methods We included patients that had undergone laser in situ keratomileusis (LASIK) or laser-assisted subepithelial keratectomy (LASEK) to correct their myopia and that had at least 10 years of follow-up. We evaluated the stability of visual acuity in terms of safety, efficacy, and refractive changes at examinations 6 months and 1, 2, 5, 7, and 10 years after surgery. Results The study evaluated 62 eyes (36 eyes in LASIK patients and 26 eyes in LASEK patients). In both groups, the efficacy index tended to decrease, and it was consistently higher in the LASEK group compared to the LASIK group over the 10 years of follow-up. The safety index improved over 10 years and was always higher than 0.9 in both groups. The difference between the spherical equivalent at 6 months postoperatively and later periods was statistically significant after 5, 7, and 10 years in both groups (LASIK, p = 0.036, p = 0.003, and p < 0.001, respectively; LASEK, p = 0.006, p = 0.002, and p = 0.001, respectively). Ten years after surgery,26 eyes (66.7%) in the LASIK group and 19 eyes (73.1%) in the LASEK group had myopia greater than 1 diopter. In comparison with the thickness at 6 months postoperatively, central corneal thickness was significantly increased after 5, 7, and 10 years in both LASIK and LASEK groups (LASIK, p < 0.001, p < 0.001, and p < 0.001, respectively; LASEK, p = 0.01, p < 0.001, and p < 0.001, respectively). Conclusions Moderately myopic eyes showed progressive myopic shifting and corneal thickening after LASIK and LASEK during 10 years of follow-up. We also found that early refractive regression may indicate the long-term refractive outcome. PMID:27051256

Risk factors for astigmatism in the Vision in Preschoolers Study.

PubMed

Huang, Jiayan; Maguire, Maureen G; Ciner, Elise; Kulp, Marjean Taylor; Cyert, Lynn A; Quinn, Graham E; Orel-Bixler, Deborah; Moore, Bruce; Ying, Gui-Shuang

2014-05-01

To determine demographic and refractive risk factors for astigmatism in the Vision in Preschoolers Study. Three- to 5-year-old Head Start preschoolers (N = 4040) from five clinical centers underwent comprehensive eye examinations by study-certified optometrists and ophthalmologists, including monocular visual acuity testing, cover testing, and cycloplegic retinoscopy. Astigmatism was defined as the presence of greater than or equal to +1.5 diopters (D) cylinder in either eye, measured with cycloplegic refraction. The associations of risk factors with astigmatism were evaluated using the odds ratio (OR) and its 95% confidence interval (CI) from logistic regression models. Among 4040 Vision in Preschoolers Study participants overrepresenting children with vision disorders, 687 (17%) had astigmatism, and most (83.8%) had with-the-rule astigmatism. In multivariate analyses, African American (OR, 1.65; 95% CI, 1.22 to 2.24), Hispanic (OR, 2.25; 95% CI, 1.62 to 3.12), and Asian (OR, 1.76; 95% CI, 1.06 to 2.93) children were more likely to have astigmatism than non-Hispanic white children, whereas American Indian children were less likely to have astigmatism than Hispanic, African American, and Asian children (p < 0.0001). Refractive error was associated with astigmatism in a nonlinear manner, with an OR of 4.50 (95% CI, 3.00 to 6.76) for myopia (≤-1.0 D in spherical equivalent) and 1.55 (95% CI, 1.29 to 1.86) for hyperopia (≥+2.0 D) when compared with children without refractive error (>-1.0 D, <+2.0 D). There was a trend of an increasing percentage of astigmatism among older children (linear trend p = 0.06). The analysis for risk factors of with-the-rule astigmatism provided similar results. Among Head Start preschoolers, Hispanic, African American, and Asian race as well as myopic and hyperopic refractive error were associated with an increased risk of astigmatism, consistent with findings from the population-based Multi-ethnic Pediatric Eye Disease Study and the Baltimore Pediatric Eye Disease Study. American Indian children had lower risk of astigmatism.

Effect of Cycloplegia on Corneal Biometrics and Refractive State

PubMed Central

Bagheri, Abbas; Feizi, Mohadeseh; Shafii, Aliakbar; Faramarzi, Amir; Tavakoli, Mehdi; Yazdani, Shahin

2018-01-01

Purpose: To determine changes in refractive state and corneal parameters after cycloplegia with cyclopentolate hydrochloride 1% using a dual Scheimpflug imaging system. Methods: In this prospective cross-sectional study patients aged 10 to 40 years who were referred for optometric evaluation enrolled and underwent autorefraction and corneal imaging with the Galilei dual Scheimpflug system before and 30 minutes after twice instillation of medication. Changes in refraction and astigmatism were investigated. Corneal biometrics including anterior and posterior corneal curvatures, total corneal power and corneal pachymetry were compared before and after cycloplegia. Results: Two hundred and twelve eyes of 106 subjects with mean age of 28 ± 5 years including 201 myopic and 11 hyperopic eyes were evaluated. Mean spherical equivalent refractive error before cycloplegia was -3.4 ± 2.6 D. A mean hyperopic shift of 0.4 ± 0.5 D occurred after cycloplegia (P < 0.001). The astigmatism power did not significantly change (P = 0.8), however, 26.8% of eyes with significant astigmatism experienced a change of more than 5 degrees in the axis of astigmatism. Changes in posterior corneal curvature were scant but statistically significant (P = 0.001). Moreover, corneal thickness was slightly increased in the central and paracentral regions (P < 0.001 and P < 0.001, respectively). Conclusion: Cycloplegia causes a hyperopic shift and astigmatism axis changes, along with an increase in central and paracentral corneal thickness and change in posterior corneal curvature. The effects of cycloplegia on refraction and corneal biometrics should be considered before cataract and refractive surgeries. PMID:29719636

Visual outcomes after balanced salt solution infiltration during lenticule separation in small-incision lenticule extraction for myopic astigmatism.

PubMed

Liu, Ting; Zhu, Xiaomin; Chen, Kaijian; Bai, Ji

2017-07-01

To evaluate the refractive outcomes of balanced salt solution infiltration during small-incision lenticule extraction (SMILE).This randomized prospective study enrolled 52 patients (104 eyes) with myopic astigmatism. Patients underwent SMILE to correct the myopic astigmatism in Daping Hospital of the Third Military Medical University between January and July 2013. One eye of each patient received traditional SMILE (control group) and the other received a modified SMILE procedure (liquid infiltration group). The corrected distance visual acuity (CDVA), postoperative uncorrected distance visual acuity (UDVA), refraction, wavefront aberration, intraocular pressure (IOP), modulation transfer function (MTF) cut-off frequency, and objective scattering index (OSI) were evaluated.UDVA in the liquid infiltration group was significantly higher than that in the control group at 1 day postoperatively, but not at 1 month after surgery. Moreover, OSI and MTF cut-off frequency in the liquid infiltration group were higher than those in the control group at early follow-up. However, no significant intergroup difference was observed in the OSI and MTF cut-off frequency at 3 months after surgery. In addition, the predictability was better in the liquid infiltration group than in the control group. The changes of horizontal coma in the liquid infiltration group were lesser than those in the control group. However, no intergroup difference was observed in the reduction of IOP at 1 month after surgery.The modified SMILE procedure results in better visual outcomes than did the traditional SMILE procedure when used for treating myopic astigmatism.

Optical treatment strategies to slow myopia progression: Effects of the visual extent of the optical treatment zone

PubMed Central

Smith, Earl L.

2013-01-01

In order to develop effective optical treatment strategies for myopia, it is important to understand how visual experience influences refractive development. Beginning with the discovery of the phenomenon of form deprivation myopia, research involving many animal species has demonstrated that refractive development is regulated by visual feedback. In particular, animal studies have shown that optically imposed myopic defocus slows axial elongation, that the effects of vision are dominated by local retinal mechanisms, and that peripheral vision can dominate central refractive development. In this review, the results obtained from clinical trials of traditional optical treatment strategies employed in efforts to slow myopia progression in children are interpreted in light of the results from animal studies and are compared to the emerging results from preliminary clinical studies of optical treatment strategies that manipulate the effective focus of the peripheral retina. Overall, the results suggest that imposed myopic defocus can slow myopia progression in children and that the effectiveness of an optical treatment strategy in reducing myopia progression is influenced by the extent of the visual field that is manipulated. PMID:23290590

Evaluation of retinal nerve fiber layer thickness parameters in myopic population using scanning laser polarimetry (GDxVCC).

PubMed

Dada, Tanuj; Aggarwal, A; Bali, S J; Sharma, A; Shah, B M; Angmo, D; Panda, A

2013-01-01

Myopia presents a significant challenge to the ophthalmologist as myopic discs are often large, tilted, with deep cups and have a thinner neuroretinal rim all of which may mimic glaucomatous optic nerve head changes causing an error in diagnosis. To evaluate the retinal fiber layer (RNFL) thickness in low, moderate and high myopia using scanning laser polarimetry with variable corneal compensation (GDxVCC). One hundred eyes of 100 emmetropes, 30 eyes of low myopes (0 to - 4 D spherical equivalent(SE), 45 eyes with moderate myopia (- 4 to - 8D SE), and 30 eyes with high myopia (- 8 to - 15D SE) were subjected to retinal nerve fiber layer assessment using the scanning laser polarimetry (GDxVCC) in all subjects using the standard protocol. Subjects with IOP > 21 mm Hg, optic nerve head or visual field changes suggestive of glaucoma were excluded from the study. The major outcome parameters were temporal-superior-nasal-inferiortemporal (TSNIT) average, the superior and inferior average and the nerve fibre indicator (NFI). The TSNIT average (p = 0.009), superior (p = 0.001) and inferior average (p = 0.008) were significantly lower; the NFI was higher (P less than 0.001) in moderate myopes as compared to that in emmetropes. In high myopia the RNFL showed supranormal values; the TSNIT average, superior and inferior average was significantly higher(p less than 0.001) as compared to that in emmetropes. The RNFL measurements on scanning laser polarimetry are affected by the myopic refractive error. Moderate myopes show a significant thinning of the RNFL. In high myopia due to peripapillary chorioretinal atrophy and contribution of scleral birefringence, the RNFL values are abnormally high. These findings need to be taken into account while assessing and monitoring glaucoma damage in moderate to high myopes on GDxVCC. © NEPjOPH.

Vector analysis of high (≥3 diopters) astigmatism correction using small-incision lenticule extraction and laser in situ keratomileusis.

PubMed

Chan, Tommy C Y; Wang, Yan; Ng, Alex L K; Zhang, Jiamei; Yu, Marco C Y; Jhanji, Vishal; Cheng, George P M

2018-06-13

To compare the astigmatic correction in high myopic astigmatism between small-incision lenticule extraction and laser in situ keratomileusis (LASIK) using vector analysis. Hong Kong Laser Eye Center, Hong Kong. Retrospective case series. Patients who had correction of myopic astigmatism of 3.0 diopters (D) or more and had either small-incision lenticule extraction or femtosecond laser-assisted LASIK were included. Only the left eye was included for analysis. Visual and refractive results were presented and compared between groups. The study comprised 105 patients (40 eyes in the small-incision lenticule extraction group and 65 eyes in the femtosecond laser-assisted LASIK group.) The mean preoperative manifest cylinder was -3.42 D ± 0.55 (SD) in the small-incision lenticule extraction group and -3.47 ± 0.49 D in the LASIK group (P = .655). At 3 months, there was no significant between-group difference in uncorrected distance visual acuity (P = .915) and manifest spherical equivalent (P = .145). Ninety percent and 95.4% of eyes were within ± 0.5 D of the attempted cylindrical correction for the small-incision lenticule extraction and LASIK group, respectively (P = .423). Vector analysis showed comparable target-induced astigmatism (P = .709), surgically induced astigmatism vector (P = .449), difference vector (P = .335), and magnitude of error (P = .413) between groups. The absolute angle of error was 1.88 ± 2.25 degrees in the small-incision lenticule extraction group and 1.37 ± 1.58 degrees in the LASIK group (P = .217). Small-incision lenticule extraction offered astigmatic correction comparable to LASIK in eyes with high myopic astigmatism. Copyright © 2018 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.

Intraocular lens power calculations for cataract surgery after phototherapeutic keratectomy in granular corneal dystrophy type 2.

PubMed

Jung, Se Hwan; Han, Kyung Eun; Sgrignoli, Bradford; Kim, Tae-Im; Lee, Hyung Keun; Kim, Eung Kweon

2012-10-01

To investigate the predictability of various intraocular lens (IOL) power calculation methods in granular corneal dystrophy type 2 (GCD2) with prior phototherapeutic keratectomy (PTK) and to suggest the more predictable IOL power calculation method. Medical records of 20 eyes from 16 patients with GCD2, all having undergone cataract surgery after PTK, were retrospectively evaluated. Postoperative cataract refractive errors were compared with target diopters (D) using IOL power calculation methods as follows: 1) myopic and 2) hyperopic Haigis-L formula in IOLMaster (Carl Zeiss Meditec); 3) SRK/T formula using 4.5-mm zone Holladay equivalent keratometry readings (EKRs) (single-K Holladay EKRs method); 4) central keratometry power of true net power map in the Pentacam system (Oculus Optikgeräte GmbH); and 5) clinical history, Aramberri double-K, and double-K Holladay EKRs methods. Topographic status of corneal curvature after PTK was evaluated. Fourteen (70%) of 20 eyes showed central island formation after PTK. When central island was present, the mean absolute error (MAE) using the hyperopic Haigis-L formula was 0.25±0.15 D. When central island was not present, the myopic Haigis-L formula showed MAE of 0.33±0.16 D. When central island formation and IOLMaster keratometry underestimation were present, the hyperopic Haigis-L formula showed the least MAE of 0.26±0.08 D when switching the IOL-Master keratometry values equal to 4.5-mm zone Holladay EKRs. In planning for cataract surgery after PTK in GCD2, topographic analysis for central island formation is necessary. With or without central island formation, the hyperopic or myopic Haigis-L formula can be applied. When IOLMaster keratometry shows underestimation, the Haigis-L formula using 4.5-mm zone Holladay EKRs can be considered. Copyright 2012, SLACK Incorporated.

Dependency between light intensity and refractive development under light-dark cycles.

PubMed

Cohen, Yuval; Belkin, Michael; Yehezkel, Oren; Solomon, Arieh S; Polat, Uri

2011-01-01

The emmetropization process involves fine-tuning the refractive state by altering the refractive components toward zero refraction. In this study, we provided light-dark cycle conditions at several intensities and examined the effect of light intensity on the progression of chicks' emmetropization. Chicks under high-, medium-, and low-light intensities (10,000, 500, and 50 lux, respectively) were followed for 90 days by retinoscopy, keratometry, as well as ultrasound measurements. Emmetropization was reached from days 30-50 and from days 50-60 for the low- and medium-intensity groups, respectively. On day 90, most chicks in the low-intensity group were myopic, with a mean refraction of -2.41D (95% confidence interval (CI) -2.9 to -1.8D), whereas no chicks in the high-intensity group developed myopia, but they exhibited a stable mean hyperopia of +1.1D. The medium-intensity group had a mean refraction of +0.03D. The low-intensity group had a deeper vitreous chamber depth and a longer axial length compared with the high-intensity group, and shifted refraction to the myopic side. The low-intensity group had a flatter corneal curvature, a deeper anterior chamber, and a thinner lens compared with the high-intensity group, and shifted refraction to the hyperopic side. In all groups the corneal power was correlated with the three examined levels of log light intensity for all examined times (e.g., day 20 r = 0.6 P < 0.0001, day 90 r = 0.56 P < 0.0001). Thus, under light-dark cycles, light intensity is an environmental factor that modulates the process of emmetropization, and the low intensity of ambient light is a risk factor for developing myopia. Copyright © 2010 Elsevier Ltd. All rights reserved.

Myopia Stabilization and Associated Factors Among Participants in the Correction of Myopia Evaluation Trial (COMET)

PubMed Central

2013-01-01

Purpose. To use the Gompertz function to estimate the age and the amount of myopia at stabilization and to evaluate associated factors in the Correction of Myopia Evaluation Trial (COMET) cohort, a large ethnically diverse group of myopic children. Methods. The COMET enrolled 469 ethnically diverse children aged 6 to younger than 12 years with spherical equivalent refraction between −1.25 and −4.50 diopters (D). Noncycloplegic refraction was measured semiannually for 4 years and annually thereafter. Right eye data were fit to individual Gompertz functions in participants with at least 6 years of follow-up and at least seven refraction measurements over 11 years. Function parameters were estimated using a nonlinear least squares procedure. Associated factors were evaluated using linear regression. Results. In total, 426 participants (91%) had valid Gompertz curve fits. The mean (SD) age at myopia stabilization was 15.61 (4.17) years, and the mean (SD) amount of myopia at stabilization was −4.87 (2.01) D. Ethnicity (P < 0.0001) but not sex or the number of myopic parents was associated with the age at stabilization. Ethnicity (P = 0.02) and the number of myopic parents (P = 0.01) but not sex were associated with myopia magnitude at stabilization. At stabilization, African Americans were youngest (mean age, 13.82 years) and had the least myopia (mean, −4.36 D). Participants with two versus no myopic parents had approximately 1.00 D more myopia at stabilization. The age and the amount of myopia at stabilization were correlated (r = −0.60, P < 0.0001). Conclusions. The Gompertz function provides estimates of the age and the amount of myopia at stabilization in an ethnically diverse cohort. These findings should provide guidance on the time course of myopia and on decisions regarding the type and timing of interventions. PMID:24159085

Peripheral Optics with Bifocal Soft and Corneal Reshaping Contact Lenses

PubMed Central

Ticak, Anita; Walline, Jeffrey J.

2012-01-01

Purpose To determine whether bifocal soft contact lenses with a distance center design provide myopic defocus to the peripheral retina similar to corneal reshaping contact lenses. Methods Myopic subjects underwent five cycloplegic autorefraction readings centrally and at 10, 20, and 30 degrees temporally, nasally, superiorly, inferiorly while wearing a Proclear Multifocal “D” contact lens with a +2.00 D add (CooperVision, Fairport, NY) and after wearing a Corneal Refractive Therapy (Paragon Vision Sciences, Mesa, AZ) contact lens for two weeks Results Fourteen subjects completed the study. Nine (64%) were female, and 12 (86%) were Caucasian. The average (± standard deviation) spherical equivalent non-cycloplegic manifest refraction for the right eye was −2.84 ± 1.29 D. The average logMAR best-corrected, binocular high contrast visual acuity was −0.17 ± 0.15 while wearing the bifocal soft contact lens, and −0.09 ± 0.16 following corneal reshaping contact lens wear (ANOVA, p = 0.27). The orthokeratology contact lens yielded a more myopic peripheral optical profile than the soft bifocal contact lens at 20 and 30 degrees eccentricity (except inferior at 20 degrees); the two modalities were similar at 10 degrees eccentricity. Conclusions Our data suggest that the two modalities are dissimilar despite the statistical similarities. The corneal reshaping contact lens shows an increase in relative peripheral myopic refraction, a pattern achieved by other studies, but the bifocal lens does not exhibit such a pattern. The low statistical power of the study could be a reason for a lack of providing statistical difference in other positions of gaze, but the graphical representation of the data shows a marked difference in peripheral optical profile between the two modalities. More sophisticated methods of measuring the peripheral optical profile may be necessary to accurately compare the two modalities and to determine the true optical effect of the bifocal soft contact lens on the peripheral retina. PMID:23222924

Peripheral optics with bifocal soft and corneal reshaping contact lenses.

PubMed

Ticak, Anita; Walline, Jeffrey J

2013-01-01

To determine whether bifocal soft contact lenses with a distance center design provide myopic defocus to the peripheral retina similar to corneal reshaping contact lenses. Myopic subjects underwent five cycloplegic autorefraction readings centrally and at 10, 20, and 30 degrees temporally, nasally, superiorly, and inferiorly while wearing Proclear Multifocal "D" contact lenses with a +2.00-diopter add power (CooperVision, Fairport, NY) and after wearing Corneal Refractive Therapy (Paragon Vision Sciences, Mesa, AZ) contact lenses for 2 weeks. Fourteen subjects completed the study. Nine (64%) were female, and 12 (86%) were white. The average (± SD) spherical equivalent noncycloplegic manifest refraction for the right eye was -2.84 ± 1.29 diopters. The average logMAR best-corrected, binocular, high-contrast visual acuity was -0.17 ± 0.15 while wearing the bifocal soft contact lenses and -0.09 ± 0.16 after corneal reshaping contact lens wear (analysis of variance, p = 0.27). The orthokeratology contact lens yielded a more myopic peripheral optical profile than the soft bifocal contact lens at 20 and 30 degrees eccentricity (except inferior at 20 degrees); the two modalities were similar at 10 degrees eccentricity. Our data suggest that the two modalities are dissimilar despite the statistical similarities. The corneal reshaping contact lens shows an increase in relative peripheral myopic refraction, a pattern achieved by other studies, but the bifocal lens does not exhibit such a pattern. The low statistical power of the study could be a reason for lack of providing statistical difference in other positions of gaze, but the graphical representation of the data shows a marked difference in the peripheral optical profile between the two modalities. More sophisticated methods of measuring the peripheral optical profile may be necessary to accurately compare the two modalities and to determine the true optical effect of the bifocal soft contact lens on the peripheral retina.

Photopic visual input is necessary for emmetropization in mice

PubMed Central

Tkatchenko, Tatiana V.; Shen, Yimin; Braun, Rod D.; Bawa, Gurinder; Kumar, Pradeep; Avrutsky, Ivan; Tkatchenko, Andrei V.

2013-01-01

It was recently demonstrated that refractive errors in mice stabilize around emmetropic values during early postnatal development, and that they develop experimental myopia in response to both visual form deprivation and imposed optical defocus similar to other vertebrate species. Animal studies also suggest that photopic vision plays critical role in emmetropization in diurnal species; however, it is unknown whether refractive eye development is guided by photopic vision in the mouse, which is a nocturnal species. We used an infrared mouse photorefractor and a high-resolution MRI to clarify the role of photopic visual input in refractive eye development in the mouse. Refractive eye development and form-deprivation myopia in P21-P89 C57BL/6J mice were analyzed under 12:12 h light-dark cycle, constant light and constant darkness regimens. Animals in all experimental groups were myopic at P21 (-13.2 ± 1.6 D, light-dark cycle; -12.5 ± 0.9 D, constant light; -12.5 ± 2.0 D, constant dark). The mean refractive error in the light-dark-cycle-reared animals was -0.5 ± 1.3 D at P32 and, and did not change significantly until P40 (+0.3 ± 0.6 D, P40). Animals in this group became progressively hyperopic between P40 and P89 (+2.2 ± 0.6, P67; +3.7 ± 2.0, P89). The mean refractive error in the constant-light-reared mice was -1.0 ± 0.7 D at P32 and remained stable until P89 (+0.1 ± 0.6, P40; +0.3 ± 0.6, P67; 0.0 ± 0.4, P89). Dark-reared animals exhibited highly hyperopic refractive errors at P32 (+5.2 ± 1.8) and became progressively more hyperopic with age (+8.7 ± 1.9, P40; +11.2 ± 1.4, P67). MRI analysis revealed that emmetropization in the P40-P89 constant-light-reared animals was associated with larger eyes, a longer axial length and a larger vitreous chamber compared to the light-dark-cycle-reared mice. Constant-light-reared mice also developed 4 times higher degrees of form-deprivation myopia on average compared to light-dark-cycle-reared animals (-12.0 ± 1.4, constant light; -2.7 ± 0.7, light-dark cycle). Dark-rearing completely prevented the development of form-deprivation myopia (-0.3 ± 0.5). Thus, photopic vision plays important role in normal refractive eye development and ocular response to visual form deprivation in the mouse. PMID:23838522

Refractive errors characteristic of the patients at the Children’s Ophthalmology Outpatient Department of Kauno klinikos Hospital (Lithuanian University of Health Sciences) from 1 January 2012 to 31 December 2012

PubMed Central

Čiumbaraitė, Rasa; Liutkevičienė, Rasa

2017-01-01

Background. The purpose of our study was to assess the distribution and patterns of refractive errors in children for the proper planning of paediatric eye care at the centre. Material and methods. The study was conducted in the hospital of the Lithuanian University of Health Sciences in Kaunas, from 1 January 2012 to 31 December 2012. During this period, a total of 11,406 children, aged 0–18 years, were evaluated at the outpatient department of paediatric ophthalmology, Kauno klinikos, the Lithuanian University of Health Sciences. All the children underwent a complete ophthalmic examination with cycloplegic refraction. Results. Myopia increased from 1.5% (95% CI:1.2, 1.8) in the age group of 0–1 to 44.7% (95% CI:43.46, 45.94) in the age group of 14–18 (p < 0.001). Myopia was associated with older age, female gender (20.3%; 95% CI:19.3, 21.3; p < 0.001). Hypermetropia decreased from 84.6% (95% CI:83.7, 85.5) in the cohort of 0–1 to 11.4% (95% CI: 10.61, 12.19) in the 14–18 age group (p < 0.001). Hypermetropia was associated with younger age, male gender (43.4%; 95% CI:42.16, 44.64; p < 0.001), preterm birth (56.1%; 95% CI:54.86, 57.34; 43.4%; p < 0.001), low birth weight (61.8%; 95% CI:60.59, 63.01; p < 0.001), and birth by Caesarean section (57.1%; 95% CI: 55.87; 58.33) (p < 0.001). The prevalence of astigmatism was 25.5% (95% CI: 24.41; 26.59) (p < 0.001). Astigmatism was associated with female gender (20.1%; 95%. CI: 19.1; 21.1) and too big pregnancy weight (22.1%.; 95%. CI: 21.06; 23.14) (p < 0.001). Conclusions. Of the 14–18 age group, 44.7% of the patients were myopic. Of the 0–1 age group, 84.6% were hypermetropic. Astigmatism was detected in about 25.5% of children. The prevalence of refractive errors was associated with age, gender, gestation age, gestation weight, and parental refractive error. PMID:28845125

Cox proportional hazards model of myopic regression for laser in situ keratomileusis flap creation with a femtosecond laser and with a mechanical microkeratome.

PubMed

Lin, Meng-Yin; Chang, David C K; Hsu, Wen-Ming; Wang, I-Jong

2012-06-01

To compare predictive factors for postoperative myopic regression between laser in situ keratomileusis (LASIK) with a femtosecond laser and LASIK with a mechanical microkeratome. Nobel Eye Clinic, Taipei, Taiwan. Retrospective comparative study. Refractive outcomes were recorded 1 day, 1 week, and 1, 3, 6, 9, and 12 months after LASIK. A Cox proportional hazards model was used to evaluate the impact of the 2 flap-creating methods and other covariates on postoperative myopic regression. The femtosecond group comprised 409 eyes and the mechanical microkeratome group, 377 eyes. For both methods, significant predictors for myopic regression after LASIK included preoperative manifest spherical equivalent (P=.0001) and central corneal thickness (P=.027). Laser in situ keratomileusis with a mechanical microkeratome had a higher probability of postoperative myopic regression than LASIK with a femtosecond laser (P=.0002). After adjusting for other covariates in the Cox proportional hazards model, the cumulative risk for myopic regression with a mechanical microkeratome was higher than with a femtosecond laser 12 months postoperatively (P=.0002). With the definition of myopic regression as a myopic shift of 0.50 diopter (D) or more and residual myopia of -0.50 D or less, the risk estimate based on the mean covariates in all eyes in the femtosecond group and mechanical microkeratome group at 12 months was 43.6% and 66.9%, respectively. Laser in situ keratomileusis with a mechanical microkeratome had a higher risk for myopic regression than LASIK with a femtosecond laser through 12 months postoperatively. Copyright © 2012. Published by Elsevier Inc.

Biometric Risk Factors for Corneal Neovascularization Associated with Hydrogel Soft Contact Lens Wear in Korean Myopic Patients

PubMed Central

Lee, Dae Seung; Wee, Won Ryang

2014-01-01

Purpose To investigate the biometric risk factors for corneal surface complications associated with hydrogel soft contact lens (SCL) fitting in myopic patients in Korea. Methods This is a retrospective case-control study. The records of 124 subjects (124 eyes) who wore SCLs on a daily basis were reviewed. Thirty-one patients (31 eyes) who were diagnosed with corneal neovascularization (NV) while wearing SCLs were included in the complication group. Ninety-three age- and sex-matched patients (93 eyes) who wore SCLs, who did not have corneal NV and who visited our clinic for correction of refractive errors were included in the control group. The degree of spherical equivalent, astigmatism and corneal base curve radius (BCR) were compared in both groups. Results Patients with NV exhibited poorer best corrected visual acuity and more myopia than controls (p = 0.008 and 0.006, respectively). In univariate analysis, highly myopic patients (-9 diopters [D] or higher) were more likely to experience NV (odds ratio [OR], 2.232; 95% confidence interval [CI], 1.602 to 3.105). High astigmatism (≥2 D) increased the risk of complications (OR, 2.717; 95% CI, 1.141 to 6.451). Steep cornea, in which BCR was <7.5 mm, also raised the risk of complications (OR, 4.000; 95% CI, 1.661 to 9.804). Flat cornea was not a risk factor for the development of NV. Conclusions High myopia, high astigmatism, and steep cornea seemed to be risk factors in the development of corneal NV in SCL wearers. PMID:25120337

Biometric risk factors for corneal neovascularization associated with hydrogel soft contact lens wear in Korean myopic patients.

PubMed

Lee, Dae Seung; Kim, Mee Kum; Wee, Won Ryang

2014-08-01

To investigate the biometric risk factors for corneal surface complications associated with hydrogel soft contact lens (SCL) fitting in myopic patients in Korea. This is a retrospective case-control study. The records of 124 subjects (124 eyes) who wore SCLs on a daily basis were reviewed. Thirty-one patients (31 eyes) who were diagnosed with corneal neovascularization (NV) while wearing SCLs were included in the complication group. Ninety-three age- and sex-matched patients (93 eyes) who wore SCLs, who did not have corneal NV and who visited our clinic for correction of refractive errors were included in the control group. The degree of spherical equivalent, astigmatism and corneal base curve radius (BCR) were compared in both groups. Patients with NV exhibited poorer best corrected visual acuity and more myopia than controls (p = 0.008 and 0.006, respectively). In univariate analysis, highly myopic patients (-9 diopters [D] or higher) were more likely to experience NV (odds ratio [OR], 2.232; 95% confidence interval [CI], 1.602 to 3.105). High astigmatism (≥2 D) increased the risk of complications (OR, 2.717; 95% CI, 1.141 to 6.451). Steep cornea, in which BCR was <7.5 mm, also raised the risk of complications (OR, 4.000; 95% CI, 1.661 to 9.804). Flat cornea was not a risk factor for the development of NV. High myopia, high astigmatism, and steep cornea seemed to be risk factors in the development of corneal NV in SCL wearers.

High resolution OCT quantitative analysis of the space between the IOL and the posterior capsule during the early cataract postoperative period.

PubMed

Tao, Aizhu; Lu, Ping; Li, Jin; Shao, Yilei; Wang, Jianhua; Shen, Meixiao; Zhao, Yinying; Lu, Fan

2013-10-25

We quantitatively characterized the space between the IOL and the posterior capsule (IOL-PC space) during the early postphacoemulsification period, using high resolution optical coherence tomography (OCT). We recruited 30 eyes of 30 patients who underwent phacoemulsification and randomly divided them into two groups. Acrysof Natural IQ IOLs were implanted in one group (n = 15), and Adapt-AO IOLs were implanted into the other (n = 15). A custom-built OCT instrument was used to image the IOL-PC space at 1 day, 1 week, and 1 month after surgery. Slit-lamp examination and auto refraction were performed at each visit. The IOL-PC spaces in the IQ group were 0.72 ± 0.35, 0.40 ± 0.24, and 0.23 ± 0.16 mm(2) at 1 day, 1 week, and 1 month after surgery, respectively. At each of these times, the values for the AO group were significantly smaller (P < 0.001). Compared to 1 day after surgery, significant changes in the ACDs and refractive errors occurred up to 1 month postoperatively in the IQ group; however, changes in the ACD and refractive error were significant only at 1 week in the AO group. The decreases in IOL-PC space and in ACD during the early postoperative period were associated with a myopic shift. It appeared that the different IOL designs had a role in closure of the IOL-PC space. High resolution OCT was suitable for quantitative analysis of IOL-PC space. (ClinicalTrials.gov number, NCT01605812.).

Ten-year follow-up of photorefractive keratectomy for myopia.

PubMed

Koshimizu, Junko; Dhanuka, Raksha; Yamaguchi, Tatsuo

2010-12-01

The aim of this study is to evaluate the long-term (10-year) outcome of excimer laser photorefractive keratectomy (PRK) on myopic eyes. This retrospective study included 42 eyes of 29 patients (13 male, 16 female; mean age 33.4 years, range 21 to 60) who were treated with myopic PRK at St. Luke's International Hospital, Tokyo, Japan, from May 1 1995 to December 31 1998, and followed up for more than 10 years. The main outcome measures were efficacy, predictability, stability, safety, and complications. We also evaluated the progress of intraocular pressure, corneal thickness, and endothelial cell density after the surgery. The cases of retreatments were excluded from this study. Ten years after the surgery, 17 eyes (40%) had 20/20 vision or better, and 35 eyes (81%) had 20/40 or better. With regard to the refractive predictability, 55 percent of the eyes were within ± 1.0D and 76% were within ± 2.0D, 10 years after the surgery. There was myopic regression with a mean change in refraction of-0.51 ± 1.78D. Best spectacle-corrected visual acuity (BCVA) was unchanged or improved in 95%, and only two eyes lost 1 line of BCVA. The mean corneal haze score was 0.19 ± 0.40, and the decreasing rate of endothelial cell was 8.30 ± 9.94% at 10 years, which was slightly higher than the spontaneous decreasing rate with age. PRK is safe and effective in refraction even 10 years after surgery; however, further long-term follow-up is needed to evaluate the decreasing of endothelial cells.

Myopic Maculopathy and Optic Disc Changes in Highly Myopic Young Asian Eyes and Impact on Visual Acuity.

PubMed

Koh, Victor; Tan, Colin; Tan, Pei Ting; Tan, Marcus; Balla, Vinay; Nah, Gerard; Cheng, Ching-Yu; Ohno-Matsui, Kyoko; Tan, Mellisa M H; Yang, Adeline; Zhao, Paul; Wong, Tien Yin; Saw, Seang-Mei

2016-04-01

To determine the prevalence and risk factors of myopic maculopathy and specific optic disc and macular changes in highly myopic eyes of young Asian adults and their impact on visual acuity. Prospective cross-sectional study. In total, 593 highly myopic (spherical equivalent refraction [SER] less than -6.00 diopters [D]) and 156 emmetropic (SER between -1.00 and +1.00 D) male participants from a population-based survey were included. All participants underwent standardized medical interviews, ophthalmic examination, and color fundus photographs. These photographs were graded systematically to determine the presence of optic disc and macular lesions. Myopic maculopathy was classified based on the International Classification of Myopic Maculopathy. The mean age was 21.1 ± 1.2 years. The mean SER for the highly myopic and emmetropic group was -8.87 ± 2.11 D and 0.40 ± 0.39 D, respectively (P < .001). Compared to emmetropic eyes, highly myopic eyes were significantly more likely to have optic disc tilt, peripapillary atrophy (PPA), posterior staphyloma, chorioretinal atrophy, and myopic maculopathy (all P < .001). The main findings included PPA (98.3%), disc tilt (22.0%), posterior staphyloma (32.0%), and chorioretinal atrophy (8.3%). Myopic maculopathy was present in 8.3% of highly myopic eyes and was associated with older age (odds ratio [OR] 1.66; 95% CI: 1.22, 2.26), reduced choroidal thickness (OR 0.99; 95% CI: 0.98, 0.99), and increased axial length (AL) (OR 1.52; 95% CI: 1.06, 2.19). The presence of disc tilt, posterior staphyloma, and chorioretinal atrophy were associated with reduced visual acuity. Our study showed that myopia-related changes of the optic disc and macula were common in highly myopic eyes even at a young age. The risk factors for myopic maculopathy include increased age, longer AL, and reduced choroidal thickness. Some of these changes were associated with reduced central visual function. Copyright © 2016 Elsevier Inc. All rights reserved.

Relationship between Refraction, Anthropometrics, and Educational Status in a Nigerian Young Adult Population.

PubMed

Badmus, Sarat A; Ajaiyeoba, Ayotunde I; Adegbehingbe, Bernice O; Onakpoya, Oluwatoyin H; Adeoye, Adenike O; Ameye, Sanyaolu A

2018-01-01

The study aimed at determining the relationship between refraction and anthropometric measurements and the relationship between the level of education and refractive status in a Nigerian young adult population. Healthy volunteers from the students and staff of a teaching hospital in South-Western Nigeria were studied. Demographic profiles including participants' highest educational status, parental educational level, and the age at first formal school enrollment were documented. The height and weight of the participants were measured. Noncycloplegic objective refraction was determined with autorefractor, and the spherical equivalent refraction (SER) of the right eye was used for analysis. SPSS 16 was used to explore the relationships between refraction, height, weight, and body mass index and the educational status of the participants. Two hundred and thirty-nine adults with a mean age of 28.4 ± 6.5 years comprising 116 males and 123 females were studied. The mean height, weight, body mass index, and right eye SER were 1.7 ± 0.1 m, 64.4 ± 12.2 kg, 23.6 ± 4.3 kg/m 2 , and -0.8 ± 1.4 D, respectively. Height was negatively correlated with the SER ( R = -0.3, P < 0.01) in males but not in females. Refraction was not significantly related to weight or body mass index. Participants with higher levels of education were more likely to be myopic. Higher parental education and early formal school enrollment were significantly associated with myopia. This study demonstrated a significant positive relationship between height and myopia in male participants but not in females. Individual as well as parental higher levels of education have also shown a positive association with myopic tendency.

Relationship between Refraction, Anthropometrics, and Educational Status in a Nigerian Young Adult Population

PubMed Central

Badmus, Sarat A.; Ajaiyeoba, Ayotunde I.; Adegbehingbe, Bernice O.; Onakpoya, Oluwatoyin H.; Adeoye, Adenike O.; Ameye, Sanyaolu A.

2018-01-01

PURPOSE: The study aimed at determining the relationship between refraction and anthropometric measurements and the relationship between the level of education and refractive status in a Nigerian young adult population. MATERIALS AND METHODS: Healthy volunteers from the students and staff of a teaching hospital in South-Western Nigeria were studied. Demographic profiles including participants' highest educational status, parental educational level, and the age at first formal school enrollment were documented. The height and weight of the participants were measured. Noncycloplegic objective refraction was determined with autorefractor, and the spherical equivalent refraction (SER) of the right eye was used for analysis. SPSS 16 was used to explore the relationships between refraction, height, weight, and body mass index and the educational status of the participants. RESULTS: Two hundred and thirty-nine adults with a mean age of 28.4 ± 6.5 years comprising 116 males and 123 females were studied. The mean height, weight, body mass index, and right eye SER were 1.7 ± 0.1 m, 64.4 ± 12.2 kg, 23.6 ± 4.3 kg/m2, and −0.8 ± 1.4 D, respectively. Height was negatively correlated with the SER (R = −0.3, P < 0.01) in males but not in females. Refraction was not significantly related to weight or body mass index. Participants with higher levels of education were more likely to be myopic. Higher parental education and early formal school enrollment were significantly associated with myopia. CONCLUSION: This study demonstrated a significant positive relationship between height and myopia in male participants but not in females. Individual as well as parental higher levels of education have also shown a positive association with myopic tendency. PMID:29899648

Comparison of the ratio of keratometric change to refractive change induced by myopic ablation.

PubMed

Moshirfar, Majid; Christiansen, Steven M; Kim, Gene

2012-10-01

To compare the ratio of keratometric change (ΔK) to refractive change (ΔSE) induced by refractive laser ablation. The charts of 3337 eyes that underwent LASIK or photorefractive keratectomy (PRK) from 2002 to 2011 were retrospectively reviewed, and the ratio ΔK/ΔSE measured at 3 months postoperatively was compared between eyes with low ΔSE (0.00 to 2.99 diopters [D]), moderate ΔSE (3.00 to 5.99 D), and high ΔSE (6.00 to 8.99 D). Eyes were further stratified by LASIK vs PRK; custom vs conventional treatments; microkeratome vs IntraLase (Abbott Medical Optics Inc) femtosecond laser-created flaps; and flat (38.00 to 41.99 D) vs moderate (42.00 to 45.99 D) vs steep (46.00 to 49.99 D) preoperative keratometry, and the ratio ΔK/ΔSE was similarly compared. Significant differences were found in the ratio ΔK/ΔSE among eyes with low ΔSE (1.00±0.50 D), moderate ΔSE (0.83±0.19 D), and steep ΔSE (0.80±0.15 D) (P<.001), and between eyes with moderate and high ΔSE in LASIK vs PRK, custom vs conventional treatments, and microkeratome vs IntraLase flaps. Significant differences in the ratio ΔK/ΔSE were also found in eyes with low, moderate, and high ΔSE regardless of preoperative keratometry. The ratio ΔK/ΔSE compared with ΔSE follows a nonlinear pattern and tended to be higher and more variable at lower amounts of correction. The change in simulated keratometry required to achieve 1.00 D of myopic refractive correction decreased as the amount of refractive change increased, was more variable with lower amounts of correction, and followed a nonlinear relationship. Many variables, such as LASIK vs PRK, custom vs conventional, and microkeratome vs IntraLase flaps, affected the ratio of ΔK/ΔSE for moderate and high myopic corrections. Copyright 2012, SLACK Incorporated.

Myopia prevalence in Chinese-Canadian children in an optometric practice.

PubMed

Cheng, Desmond; Schmid, Katrina L; Woo, George C

2007-01-01

The high prevalence of myopia in Chinese children living in urban East Asian countries such as Hong Kong, Taiwan, and China has been well documented. However, it is not clear whether the prevalence of myopia would be similarly high for this group of children if they were living in a Western country. This study aims to determine the prevalence and progression of myopia in ethnic Chinese children living in Canada. Right eye refraction data of Chinese-Canadian children aged 6 to 12 years were collated from the 2003 clinical records of an optometric practice in Mississauga, Ontario, Canada. Myopia was defined as a spherical equivalent refraction (SER) equal or less than -0.50 D. The prevalence of myopia and refractive error distribution in children of different ages and the magnitude of refractive error shifts over the preceding 8 years were determined. Data were adjusted for potential biases in the clinic sample. A questionnaire was administered to 300 Chinese and 300 Caucasian children randomly selected from the clinic records to study lifestyle issues that may impact on myopia development. Optometric records of 1468 children were analyzed (729 boys and 739 girls). The clinic bias adjusted prevalence of myopia increased from 22.4% at age 6 to 64.1% at age 12 and concurrently the portion of the children that were emmetropic (refraction between -0.25 and +0.75 D) decreased (68.6% at 6 years to 27.2% at 12 years). The highest incidence of myopia for both girls ( approximately 35%) and boys ( approximately 25%) occurred at 9 and 10 years of age. The average annual refractive shift for all children was -0.52+/-0.42 D and -0.90+/-0.40 D for just myopic children. The questionnaire revealed that these Chinese-Canadian children spent a greater amount of time performing near work and less time outdoors than did Caucasian-Canadian children. Ethnic Chinese children living in Canada develop myopia comparable in prevalence and magnitude to those living in urban East Asian countries. Recent migration of the children and their families to Canada does not appear to lower their myopia risk.

Prevalence and associations of anisometropia with spherical ametropia, cylindrical power, age, and sex in refractive surgery candidates.

PubMed

Linke, Stephan J; Richard, Gisbert; Katz, Toam

2011-09-29

To analyze the prevalence and associations of anisometropia with spherical ametropia, astigmatism, age, and sex in a refractive surgery population. Medical records of 27,070 eyes of 13,535 refractive surgery candidates were reviewed. Anisometropia, defined as the absolute difference in mean spherical equivalent powers between right and left eyes, was analyzed for subjective (A(subj)) and cycloplegic refraction (A(cycl)). Correlations between anisometropia (>1 diopter) and spherical ametropia, cylindrical power, age, and sex, were analyzed using χ² and nonparametric Kruskal-Wallis or Mann-Whitney tests and binomial logistic regression analyses. Power vector analysis was applied for further analysis of cylindrical power. Prevalence of A(subj) was 18.5% and of A(cycl) was 19.3%. In hyperopes, logistic regression analysis revealed that only spherical refractive error (odds ratio [OR], 0.72) and age (OR, 0.97) were independently associated with anisometropia. A(subj) decreased with increasing spherical ametropia and advancing age. Cylindrical power and sex did not significantly affect A(subj). In myopes all explanatory variables (spherical power OR, 0.93; cylindrical power OR, 0.75; age OR, 1.02; sex OR, 0.8) were independently associated with anisometropia. Cylindrical power was most strongly associated with anisometropia. Advancing age and increasing spherical/cylindrical power correlated positively with increasing anisometropia in myopic subjects. Female sex was more closely associated with anisometropia. This large-scale retrospective analysis confirmed an independent association between anisometropia and both spherical ametropia and age in refractive surgery candidates. Notably, an inverse relationship between these parameters in hyperopes was observed. Cylindrical power and female sex were independently associated with anisometropia in myopes.

Laser-assisted subepithelial keratectomy (LASEK) versus laser-assisted in-situ keratomileusis (LASIK) for correcting myopia

PubMed Central

Kuryan, Jocelyn; Cheema, Anjum; Chuck, Roy S

2017-01-01

Background Near-sightedness, or myopia, is a condition in which light rays entering the eye along the visual axis focus in front of the retina, resulting in blurred vision. Myopia can be treated with spectacles, contact lenses, or refractive surgery. Options for refractive surgery include laser-assisted subepithelial keratectomy (LASEK) and laser-assisted in-situ keratomileusis (LASIK). Both procedures utilize a laser to shape the corneal tissue (front of the eye) to correct refractive error, and both create flaps before laser treatment of corneal stromal tissue. Whereas the flap in LASEK is more superficial and epithelial, in LASIK it is thicker and also includes some anterior stromal tissue. LASEK is considered a surface ablation procedure, much like its predecessor, photorefractive keratectomy (PRK). LASEK was developed as an alternative to PRK to address the issue of pain associated with epithelial debridement used for PRK. Assessing the relative benefits and risks/side effects of LASEK and LASIK warrants a systematic review. Objectives To assess the effects of LASEK versus LASIK for correcting myopia. Search methods We searched the Cochrane Central Register of Controlled Trials (CENTRAL), which contains the Cochrane Eyes and Vision Trials Register (2016, Issue 10); MEDLINE Ovid (1946 to 24 October 2016); Embase.com (1947 to 24 October 2016); PubMed (1948 to 24 October 2016); LILACS (Latin American and Caribbean Health Sciences Literature Database; 1982 to 24 October 2016); the metaRegister of Controlled Trials (mRCT) (www.controlled-trials.com), last searched 20 June 2014; ClinicalTrials.gov (www.clinicaltrials.gov); searched 24 October 2016; and the WHO International Clinical Trials Registry Platform (ICTRP) (www.who.int/ictrp/search/en); searched 24 October 2016. We did not use any date or language restrictions in the electronic searches for trials. Selection criteria We considered only randomized controlled trials (RCTs) for the purposes of this review. Eligible RCTs were those in which myopic participants were assigned randomly to receive either LASEK or LASIK in one or both eyes. We also included paired-eye studies in which investigators randomly selected which of the participant’s eyes would receive LASEK or LASIK and assigned the other eye to the other procedure. Participants were men or women between the ages of 18 and 60 years with myopia up to 12 diopters (D) and/or myopic astigmatism of severity up to 3 D, who did not have a history of prior refractive surgery. Data collection and analysis Two review authors independently screened all reports and assessed the risk of bias in trials included in this review. We extracted data and summarized findings using risk ratios (RRs) for dichotomous outcomes and mean differences (MDs) for continuous outcomes. In the absence of clinical and methodological heterogeneity across trials, we used a random-effects model to calculate summary effect estimates. We used a fixed-effect model when including fewer than three trials in a meta-analysis. When clinical, methodological, or statistical heterogeneity was observed across trials, we reported our findings in a narrative synthesis. Main results We identified four eligible trials with 538 eyes of 392 participants for the review, but only three trials (154 participants) provided outcome data for analysis. We found no ongoing trials. Two of four trials were from China, one trial was from Turkey, and the location of one trial was not reported. The risk of bias for most domains was unclear due to poor reporting of trial methods; no trial had a protocol or trial registry record. Three trials enrolled participants with mild to moderate myopia (less than −6.50 D); one trial included only participants with severe myopia (more than −6.00 D). The evidence showed uncertainty in whether there is a difference between LASEK and LASIK in uncorrected visual acuity (UCVA) at 12 months, the primary outcome in our review. The RR and 95% confidence interval (CI) at 12 months after surgery was 0.96 (95% CI 0.82 to 1.13) for UCVA of 20/20 or better and 0.90 (95% CI 0.67 to 1.21) for UCVA of 20/40 or better based on data from one trial with 57 eyes (very low-certainty evidence). People receiving LASEK were less likely to achieve a refractive error within 0.5 diopters of the target at 12 months follow-up (RR 0.69, 95% CI 0.48 to 0.99; 57 eyes; very low-certainty evidence). One trial reported mild corneal haze at six months in one eye in the LASEK group and none in the LASIK group (RR 2.11, 95% CI 0.57 to 7.82; 76 eyes; very low-certainty evidence). None of the included trials reported postoperative pain score or loss of visual acuity, spherical equivalent of the refractive error, or quality of life at 12 months. Refractive regression, an adverse event, was reported only in the LASEK group (8 of 37 eyes) compared with none of 39 eyes in the LASIK group in one trial (low-certainty evidence). Other adverse events, such as corneal flap striae and refractive over-correction, were reported only in the LASIK group (5 of 39 eyes) compared with none of 37 eyes in the LASEK group in one trial (low-certainty evidence). Authors’ conclusions Overall, from the available RCTs, there is uncertainty in how LASEK compares with LASIK in achieving better refractive and visual results in mildly to moderately myopic participants. Large, well-designed RCTs would be required to estimate the magnitude of any difference in efficacy or adverse effects between LASEK and LASIK for treating myopia or myopic astigmatism. PMID:28197998

Laser-assisted subepithelial keratectomy (LASEK) versus laser-assisted in-situ keratomileusis (LASIK) for correcting myopia.

PubMed

Kuryan, Jocelyn; Cheema, Anjum; Chuck, Roy S

2017-02-15

Near-sightedness, or myopia, is a condition in which light rays entering the eye along the visual axis focus in front of the retina, resulting in blurred vision. Myopia can be treated with spectacles, contact lenses, or refractive surgery. Options for refractive surgery include laser-assisted subepithelial keratectomy (LASEK) and laser-assisted in-situ keratomileusis (LASIK). Both procedures utilize a laser to shape the corneal tissue (front of the eye) to correct refractive error, and both create flaps before laser treatment of corneal stromal tissue. Whereas the flap in LASEK is more superficial and epithelial, in LASIK it is thicker and also includes some anterior stromal tissue. LASEK is considered a surface ablation procedure, much like its predecessor, photorefractive keratectomy (PRK). LASEK was developed as an alternative to PRK to address the issue of pain associated with epithelial debridement used for PRK. Assessing the relative benefits and risks/side effects of LASEK and LASIK warrants a systematic review. To assess the effects of LASEK versus LASIK for correcting myopia. We searched the Cochrane Central Register of Controlled Trials (CENTRAL), which contains the Cochrane Eyes and Vision Trials Register (2016, Issue 10); MEDLINE Ovid (1946 to 24 October 2016); Embase.com (1947 to 24 October 2016); PubMed (1948 to 24 October 2016); LILACS (Latin American and Caribbean Health Sciences Literature Database; 1982 to 24 October 2016); the metaRegister of Controlled Trials (mRCT) (www.controlled-trials.com), last searched 20 June 2014; ClinicalTrials.gov (www.clinicaltrials.gov); searched 24 October 2016; and the WHO International Clinical Trials Registry Platform (ICTRP) (www.who.int/ictrp/search/en); searched 24 October 2016. We did not use any date or language restrictions in the electronic searches for trials. We considered only randomized controlled trials (RCTs) for the purposes of this review. Eligible RCTs were those in which myopic participants were assigned randomly to receive either LASEK or LASIK in one or both eyes. We also included paired-eye studies in which investigators randomly selected which of the participant's eyes would receive LASEK or LASIK and assigned the other eye to the other procedure. Participants were men or women between the ages of 18 and 60 years with myopia up to 12 diopters (D) and/or myopic astigmatism of severity up to 3 D, who did not have a history of prior refractive surgery. Two review authors independently screened all reports and assessed the risk of bias in trials included in this review. We extracted data and summarized findings using risk ratios (RRs) for dichotomous outcomes and mean differences (MDs) for continuous outcomes. In the absence of clinical and methodological heterogeneity across trials, we used a random-effects model to calculate summary effect estimates. We used a fixed-effect model when including fewer than three trials in a meta-analysis. When clinical, methodological, or statistical heterogeneity was observed across trials, we reported our findings in a narrative synthesis. We identified four eligible trials with 538 eyes of 392 participants for the review, but only three trials (154 participants) provided outcome data for analysis. We found no ongoing trials. Two of four trials were from China, one trial was from Turkey, and the location of one trial was not reported. The risk of bias for most domains was unclear due to poor reporting of trial methods; no trial had a protocol or trial registry record. Three trials enrolled participants with mild to moderate myopia (less than -6.50 D); one trial included only participants with severe myopia (more than -6.00 D).The evidence showed uncertainty in whether there is a difference between LASEK and LASIK in uncorrected visual acuity (UCVA) at 12 months, the primary outcome in our review. The RR and 95% confidence interval (CI) at 12 months after surgery was 0.96 (95% CI 0.82 to 1.13) for UCVA of 20/20 or better and 0.90 (95% CI 0.67 to 1.21) for UCVA of 20/40 or better based on data from one trial with 57 eyes (very low-certainty evidence). People receiving LASEK were less likely to achieve a refractive error within 0.5 diopters of the target at 12 months follow-up (RR 0.69, 95% CI 0.48 to 0.99; 57 eyes; very low-certainty evidence). One trial reported mild corneal haze at six months in one eye in the LASEK group and none in the LASIK group (RR 2.11, 95% CI 0.57 to 7.82; 76 eyes; very low-certainty evidence). None of the included trials reported postoperative pain score or loss of visual acuity, spherical equivalent of the refractive error, or quality of life at 12 months.Refractive regression, an adverse event, was reported only in the LASEK group (8 of 37 eyes) compared with none of 39 eyes in the LASIK group in one trial (low-certainty evidence). Other adverse events, such as corneal flap striae and refractive over-correction, were reported only in the LASIK group (5 of 39 eyes) compared with none of 37 eyes in the LASEK group in one trial (low-certainty evidence). Overall, from the available RCTs, there is uncertainty in how LASEK compares with LASIK in achieving better refractive and visual results in mildly to moderately myopic participants. Large, well-designed RCTs would be required to estimate the magnitude of any difference in efficacy or adverse effects between LASEK and LASIK for treating myopia or myopic astigmatism.

[Visual outcomes four years after small incision lenticule extraction (SMILE) surgery on highly myopic eyes [French version

PubMed

Burazovitch, J; Naguzeswski, D; Beuste, T; Guillard, M

2017-09-01

To determine whether the visual outcomes of the refractive surgery technique, small incision lenticule extraction (SMILE), are stable, effective, and predictable for high myopia over a four-year period. This is a retrospective study. The data were collected between March 2012 and July 2016. Two hundred and forty-eight patients participated in the study; that is, 496 eyes: 140 eyes of 70 patients (52 women/18 men) were classified in the highly myopic group (refraction measured in spherical equivalent [RMSE]>-6D), and 356 eyes of 178 patients (98 women/80 men) in the control group (RMSE≤-6D). Follow-up tests were conducted immediately post-operatively (D+1), after three months, after one year, and after four years. Refraction, uncorrected visual acuity (UCVA), and best visual corrected acuity (BCVA) were measured. The highly myopic group (HMG) contained more women, and astigmatism was higher for this group than for the control group (CG). These are BCVA, refractive stability, the index of safety (SI: BCVA preoperatively D+1/BCVA postoperatively), and predictability (the percentage of eyes within±0.5 D of the target). In both groups, UCVA was better after the fourth year than it was immediately after the procedure (HMG: P=0.001; CG: P=0.001). Although it differed at one year (P=0.01), the groups' refractive stability tended to converge over four years (P=0.138). Both groups' SI was identical in the four follow-up tests (P=0.734 at D+1; P=0.07 at M+1; P=0.160 at M3 and Y1; and P=0.274 at Y4). For the HMG, SI stability was attained after three months (1.00±0.1); whereas it was attained after one month (0.91±0.11) for the CG. Four years after the surgery, we observed that 87 % of the operated eyes in the HMG were within 0.5 D of the target. SMILE is a good refractive surgery technique for treating high myopia. It yields stable, safe, effective, and predictable results over four years. Copyright © 2017 Elsevier Masson SAS. All rights reserved.

A teaching resource using the GUIDE environment: simplified model of the eye for secondary school students

NASA Astrophysics Data System (ADS)

Gómez-Varela, A. I.; Salvado-Vara, F.; Bao-Varela, C.

2014-07-01

Nowadays, new technologies have great influence on our lives and how we access to the information. The new generations have never known a world without them and make use of these new technologies in practically all facets of their day-to-day. Education systems have also evolved rapidly and frequently make use of learning strategies based on interactive tools. In this work we have created a graphical user interface with GUIDE, a development environment of MATLAB, to show, in a simple way, how the eye works. This interactive program is addressed to the first courses of secondary education and designed to introduce them to the basic concepts of the normal refractive condition of the eye and the most common refractive errors, as myopia and hyperopia. The graphic interface makes use of the simplified model of the eye, where the optic system of the visual organ is represented by a converging lens (cornea and crystalline) and a screen (retina). Emmetropic, myopic and hyperopic eye operation is shown graphically to the students, as well as how these focusing errors can be solved with a diverging and converging lens, respectively. This teaching tool was used this academic course in the Colegio Hogar de Santa Margarita (A Coruña) for a better understanding of the students in this matter and to catch their attention to the world of Optics and its importance.

Effects of flickering light on refraction and changes in eye axial length of C57BL/6 mice.

PubMed

Yu, Ying; Chen, Hui; Tuo, Jingsheng; Zhu, Yin

2011-01-01

To investigate the effectiveness and feasibility of inducing myopia in mice by flickering-light (FL) stimulation. Forty-five 28-day-old C57BL/6 (B6) mice were randomly assigned to three groups: control group, FL stimulation group and form deprivation (FD) group. Mice in the control group were raised under 250 lux illumination from 8:00 a.m. to 8:00 p.m. Mice in the FL group were raised under illumination with a duty cycle of 50% at a flash rate of 2 Hz from 8:00 a.m. to 8:00 p.m. for 6 weeks. Mice in the FD group were raised under the same conditions as the control group; the right eyes of the mice were covered with semitransparent hemispherical plastic shells serving as eye diffusers. The refractive state and axial length (AL) of the right eyes were measured by eccentric infrared photorefraction and A-scan ultrasonography, respectively, before treatment and after 2, 4, 6 or 8 weeks' treatment. After 6 weeks' exposure to FL, the refraction became more myopic compared with the control group as indicated by longer AL compared with the control group (p < 0.05); the FD eyes were more myopic than the FL eyes (p < 0.05). However, some mice lost their eye diffusers, and lens opacities were found. Myopia can be induced by FL in B6 mice. The myopic shift induced by FL is less than that induced by FD, but FL causes fewer side effects, and is safery and easier to manipulate. Copyright © 2011 S. Karger AG, Basel.

Simulation of the Effect of Different Presbyopia-Correcting Intraocular Lenses With Eyes With Previous Laser Refractive Surgery.

PubMed

Camps, Vicente J; Miret, Juan J; García, Celia; Tolosa, Angel; Piñero, David P

2018-04-01

To simulate the optical performance of three presbyopia-correcting intraocular lenses (IOLs) implanted in eyes with previous laser refractive surgery. A simulation of the through-focus modulation transfer function (MTF) was performed for three presbyopia-correcting IOLs (Mplus, Oculentis GmbH, Berlin, Germany; Symfony, Johnson & Johnson Vision, Santa Ana, CA; and Mini Well, SIFI S.p.A., Lavinaio, Italy) in one eye with previous myopic LASIK and another with hyperopic LASIK. Real topographic data and the wavefront aberration profile of each IOL obtained with a Hartmann-Shack sensor were used. In the eye with myopic LASIK, all IOLs lost optical quality at near and intermediate distances for 4- and 4.7-mm pupil size. For 3-mm pupil size, the Mini Well IOL showed the best intermediate and near MTF and maintained the far focus independently of the pupil. In the eye with hyperopic LASIK, the Mini Well IOL showed an intermediate, distance, and -4.00-diopter (D) foci for all pupils. The Symfony IOL showed a depth of focus at far and intermediate distance for 3-mm and a focus at -2.50 D in the rest. The Mplus showed a focus of -4.50 and -3.00 D for the 3- and 4-mm pupil, respectively. The Mini Well and Symfony IOLs seem to work better than the Mplus IOL in eyes with previous myopic LASIK. With previous hyperopic LASIK, the Mini Well IOL seems to be able to provide acceptable near, intermediate, and far foci for all pupil sizes. These findings should be confirmed in future clinical studies. [J Refract Surg. 2018;34(4):222-227.]. Copyright 2018, SLACK Incorporated.

Outcomes of photorefractive keratectomy following laser in situ keratomileusis: a cohort study.

PubMed

Iovieno, Alfonso; Teichman, Joshua C; Low, Stephanie; Yeung, Sonia N; Eve Lègarè, Marie; Lichtinger, Alejandro D; Slomovic, Allan R; Rootman, David S

2016-12-01

To analyze the outcomes of photorefractive keratectomy (PRK) on residual myopia and hyperopia post-laser in situ keratomileusis (LASIK) and to compare these results with PRK on eyes without previous laser refractive surgery. Retrospective comparative cohort study. Patients undergoing PRK between 2006 and 2010 were reviewed. Patients were divided into 4 groups, myopic or hyperopic PRK post-LASIK (mPRK-PL and hPRK-PL, respectively) and myopic or hyperopic PRK on corneas without previous laser refractive surgery (mPRK and hPRK, respectively). Uncorrected and corrected distance visual acuity, mean refractive spherical equivalent (MRSE), and mean keratometry and aberrations (total, higher order [HOA], coma, trefoil, and spherical aberration) were recorded at months 3 and 6 postoperatively, as were complications and attempted versus achieved MRSE. Thirty-three eyes of 25 patients who underwent PRK post-LASIK (21 eyes of 14 patients for hPRK-PL and 12 eyes of 11 patients for mPRK-PL) and 35 eyes of 21 patients who underwent PRK on virgin eyes (11 eyes of 8 patients for hPRK and 24 eyes of 13 patients for mPRK) were included in the study. The only significant differences in outcomes were found to be HOA at 3 months for hPRK-PL as compared with both hPRK and mPRK. Achieved MRSE was significantly different from expected MRSE for hPRK-PL at 3 months postoperatively. No haze- or flap-related complications were observed. Outcomes of PRK were not different in myopic and hyperopic corrections post-LASIK by 6 months or when compared with PRK in virgin eyes. HOA may render hPRK-PL results less predictable early in the postoperative period. Copyright © 2016 Canadian Ophthalmological Society. Published by Elsevier Inc. All rights reserved.

Autorefraction versus subjective refraction in a radially asymmetric multifocal intraocular lens.

PubMed

van der Linden, Jan Willem; Vrijman, Violette; Al-Saady, Rana; El-Saady, Rana; van der Meulen, Ivanka J; Mourits, Maarten P; Lapid-Gortzak, Ruth

2014-12-01

To evaluate whether the automated refraction (AR) correlates with subjective manifest (MR) refraction in eyes implanted with radially asymmetric multifocal intraocular lens (IOLs). This retrospective study evaluated 52 eyes (52 patients) implanted with a radially asymmetric multifocal IOL (LS-312 MF30, Oculentis, Germany). At 3 months postoperatively, the AR and MR values were compared to determine the correlation between the sphere (S), the spherical equivalent (SE) and the astigmatic components J0 and J45. The difference of mean spherical measurement was +0.98D ± 0.62, with the AR measuring more myopic. The difference of the mean spherical equivalent was +1.11D ± 0.57, again with AR being more myopic. Both these differences were statistically significant (p < 0.001). The astigmatic components showed less differences, with the mean difference of the J0 being -0.09D ± 0.43, and the J45 of +0.04D ± 0.47, which were both not statistically significant (p = 0.123 and p = 0.531, respectively). Correlation analysis of the refractive parameters showed r(2) = 0.067, r(2) = 0.078, r(2) = 0.018 and r(2) = 0.015, respectively, all of which point to a low correlation between the AR and the MR. Autorefraction shows poor correlation to manifest subjective refraction with these radially asymmetric multifocal IOLs. The autorefraction systematically underestimates the spherical and spherical equivalent power, while the correlation between the astigmatic components was also low. Autorefraction seems not a valid starting point for manifest subjective refraction with these types of lenses, unless a corrective factor of about +1 dioptre is used. © 2014 Acta Ophthalmologica Scandinavica Foundation. Published by John Wiley & Sons Ltd.

Predictive Formula for Refraction of Autologous Lenticule Implantation for Hyperopia Correction.

PubMed

Li, Meng; Li, Meiyan; Sun, Ling; Ni, Katherine; Zhou, Xingtao

2017-12-01

To create a formula to predict refractive correction of autologous lenticule implantation for correction of hyperopia (with myopia in one eye and hyperopia in the contralateral eye). In this prospective study, 10 consecutive patients (20 eyes) who had myopia in one eye and hyperopia in the contralateral eye were included. The preoperative spherical equivalent was -3.31 ± 1.73 diopters (D) for the myopic eyes and +4.46 ± 1.97 D for the hyperopic eyes. For each patient, the myopic eye was treated with small incision lenticule extraction and the lenticule was subsequently implanted into the contralateral hyperopic eye. The average length of follow-up was 17 months. All of the operations were successful without complications. At the last visit, the efficacy index (postoperative uncorrected distance visual acuity/preoperative corrected distance visual acuity [CDVA]) of the hyperopic eyes was 0.94 ± 0.35 and the safety index (postoperative CDVA/preoperative CDVA) was 1.36 ± 0.38. No eyes lost any lines of visual acuity. Six of 10 (60%) of the implanted eyes were within ±1.00 D of the intended refractive target. A predictive formula was derived: Lenticule implantation achieved correction (D) (LAC) = 1.224 Lenticule refractive power (D) (LRP) - 0.063 (R 2 =0.92, P < .001). On corneal topography, there was a significant increase in the corneal anterior surface keratometry value postoperatively, whereas the posterior surface keratometry value remained stable (P > .05). Autologous lenticule implantation could provide a reliable method of correcting hyperopia. The refractive correction formula may require further verification and adjustment. [J Refract Surg. 2017;33(12):827-833.]. Copyright 2017, SLACK Incorporated.

Refractive Changes Induced by Spherical Aberration in Laser Correction Procedures: An Adaptive Optics Study.

PubMed

Amigó, Alfredo; Martinez-Sorribes, Paula; Recuerda, Margarita

2017-07-01

To study the effect on vision of induced negative and positive spherical aberration within the range of laser vision correction procedures. In 10 eyes (mean age: 35.8 years) under cyclopegic conditions, spherical aberration values from -0.75 to +0.75 µm in 0.25-µm steps were induced by an adaptive optics system. Astigmatism and spherical refraction were corrected, whereas the other natural aberrations remained untouched. Visual acuity, depth of focus defined as the interval of vision for which the target was still perceived acceptable, contrast sensitivity, and change in spherical refraction associated with the variation in pupil diameter from 6 to 2.5 mm were measured. A refractive change of 1.60 D/µm of induced spherical aberration was obtained. Emmetropic eyes became myopic when positive spherical aberration was induced and hyperopic when negative spherical aberration was induced (R 2 = 81%). There were weak correlations between spherical aberration and visual acuity or depth of focus (R 2 = 2% and 3%, respectively). Contrast sensitivity worsened with the increment of spherical aberration (R 2 = 59%). When pupil size decreased, emmetropic eyes became hyperopic when preexisting spherical aberration was positive and myopic when spherical aberration was negative, with an average refractive change of 0.60 D/µm of spherical aberration (R 2 = 54%). An inverse linear correlation exists between the refractive state of the eye and spherical aberration induced within the range of laser vision correction. Small values of spherical aberration do not worsen visual acuity or depth of focus, but positive spherical aberration may induce night myopia. In addition, the changes in spherical refraction when the pupil constricts may worsen near vision when positive spherical aberration is induced or improve it when spherical aberration is negative. [J Refract Surg. 2017;33(7):470-474.]. Copyright 2017, SLACK Incorporated.

Comparison between toric and spherical phakic intraocular lenses combined with astigmatic keratotomy for high myopic astigmatism.

PubMed

Zheng, Lin-Yan; Zhu, Shuang-Qian; Su, Yan-Feng; Zou, Hu-Yong; Wang, Qin-Mei; Yu, A-Yong

2017-01-01

To compare the outcomes of a toric phakic intraocular lens (PIOL) and a spherical PIOL combined with astigmatic keratotomy (AK) for the correction of high myopic astigmatism. This study enrolled patients with high myopic astigmatism, including 30 eyes (22 patients) that received a toric PIOL implantation (TICL group), and 32 eyes (24 patients) that received combined AK and a spherical PIOL implantation (AK+ ICL group). The outcomes were compared between the two groups before surgery, and at the following time points after surgery: 1 week, 1, 3, 6 months, and 1, 2 years. Preoperatively, the mean manifest spherical equivalent (SE) was -14.14 ± 2.12 D in the TICL group and -14.83 ± 2.79 D in the AK + ICL group ( P  = 0.28), and the mean manifest refractive cylinder, -2.87 ± 1.09 D and -2.58 ± 0.85 D, respectively ( P  = 0.28). Two years postoperatively, the mean safety index was 1.53 ± 0.55 in the TICL group and 1.60 ± 0.70 in the AK + ICL group ( P  = 1.00), and the mean efficacy index, 1.18 ± 0.45 and 1.38 ± 0.52, respectively ( P  = 0.86). The mean manifest refractive cylinder correction was 1.94 ± 1.07 D in the TICL group and 1.39 ± 0.71 D in the AK + ICL group ( P  = 0.02). The mean changes in SE and refractive cylinder from 1 week to 2 years were less than 0.50 D in both groups. Both TICL implantation and AK + ICL implantation are a good alternative for correction of astigmatism in addition to high myopia. TICL implantation has better predictability in correction of high myopic astigmatism. NCT03202485.

Visual Guidance of Recovery from Lens-Induced Myopia in Tree Shrews (Tupaia glis belangeri)

PubMed Central

Amedo, Angela O.; Norton, Thomas T.

2011-01-01

Purpose To examine, in tree shrews, the visual guidance of recovery from negative lens-induced myopia by measuring the effect of wearing low-power negative or positive lenses during recovery. To learn if removing a negative lens for two hours per day, after compensation has occurred, is sufficient to produce recovery. Methods Starting 16 days after natural eye opening (days of visual experience), juvenile tree shrews wore a monocular –5 D lens for 11 days to produce compensation (age-appropriate refraction while wearing the lens). Recovery in four groups was started by discontinuing −5 D lens wear, which caused the treated eyes to be refractively myopic, and substituting: no lens (n = 7), a plano lens (n = 8), a −2 D lens (n = 6) or a +2 D lens (n = 10). In a fifth group (n = 6), the −5 D lens was removed for 2 hours each day but worn the remainder of the time. Non-cycloplegic refractive measurements were made daily for the first 10 days and then less frequently. After 31 to 35 days, the lens-guided recovery period was ended for most animals; periodic measures were continued to assess post-lens recovery changes. Results All the eyes responded to the −5 D lens and were myopic (-4.8±0.1 D, mean ± SEM) compared to the untreated fellow control eye. In all groups except the −2 D Lens group, some animals exhibited slow or incomplete recovery. During recovery, the treated eye of most animals recovered until its refraction, measured with the recovery-lens in place, was near to that of the control eye. Measured without the lens, the −2 D group was myopic and the +2 D group was hyperopic. With the lens in place, the plano-lens, −2 D lens, and +2 D lens groups remained slightly myopic (−1.0±0.3 D, −0.6±0.2 D and −1.3±0.1 D, respectively). The rate of recovery during the first four days was unrelated to the amount of myopia initially experienced by the recovering eyes. Removal of the −5 D lens for two hours each day produced recovery. Conclusions During recovery, the emmetropization mechanism uses the presence of myopia, but perhaps not the magnitude, to guide eyes toward a refractive state similar to the control eye, regardless of whether the optically-recovered eye is longer or shorter than the fellow control eye. Wearing a goggle frame containing a lens of any power limits the recovery. The recovery signal can be intermittent, present for only 2 hours per day, and still mediate recovery in competition with increasing amounts of hyperopia as recovery progresses. PMID:22035177

Visual guidance of recovery from lens-induced myopia in tree shrews (Tupaia glis belangeri).

PubMed

Amedo, Angela O; Norton, Thomas T

2012-03-01

To examine, in tree shrews, the visual guidance of recovery from negative lens-induced myopia by measuring the effect of wearing low-power negative or positive lenses during recovery. To learn if removing a negative lens for 2 h per day, after compensation has occurred, is sufficient to produce recovery. Starting 16 days after natural eye opening (days of visual experience), juvenile tree shrews wore a monocular -5 D lens for 11 days to produce compensation (age-appropriate refraction while wearing the lens). Recovery in four groups was started by discontinuing -5 D lens wear, which caused the treated eyes to be refractively myopic, and substituting: no lens (n = 7), a plano lens (n = 8), a -2 D lens (n = 6) or a +2 D lens (n = 10). In a fifth group (n = 6), the -5 D lens was removed for 2 h each day but worn the remainder of the time. Non-cycloplegic refractive measurements were made daily for the first 10 days and then less frequently. After 31-35 days, the lens-guided recovery period was ended for most animals; periodic measures were continued to assess post-lens recovery changes. All the eyes responded to the -5 D lens and were myopic (-4.8 ± 0.1 D, mean ± S.E.M.) compared to the untreated fellow control eye. In all groups except the -2 D lens group, some animals exhibited slow or incomplete recovery. During recovery, the treated eye of most animals recovered until its refraction, measured with the recovery-lens in place, was near to that of the control eye. Measured without the lens, the -2 D group was myopic and the +2 D group was hyperopic. With the lens in place, the plano-lens, -2 D lens, and +2 D lens groups remained slightly myopic (-1.0 ± 0.3 D, -0.6 ± 0.2 D and -1.3 ± 0.1 D, respectively). The rate of recovery during the first four days was unrelated to the amount of myopia initially experienced by the recovering eyes. Removal of the -5 D lens for 2 h each day produced recovery. During recovery, the emmetropization mechanism uses the presence of myopia, but perhaps not the magnitude, to guide eyes toward a refractive state similar to the control eye, regardless of whether the optically-recovered eye is longer or shorter than the fellow control eye. Wearing a goggle frame containing a lens of any power limits the recovery. The recovery signal can be intermittent, present for only 2 h per day, and still mediate recovery in competition with increasing amounts of hyperopia as recovery progresses. Ophthalmic & Physiological Optics © 2011 The College of Optometrists.

The Adenosine Receptor Antagonist, 7-Methylxanthine, Alters Emmetropizing Responses in Infant Macaques

PubMed Central

Hung, Li-Fang; Arumugam, Baskar; Ostrin, Lisa; Patel, Nimesh; Trier, Klaus; Jong, Monica; III, Earl L. Smith

2018-01-01

Purpose Previous studies suggest that the adenosine receptor antagonist, 7-methylxanthine (7-MX), retards myopia progression. Our aim was to determine whether 7-MX alters the compensating refractive changes produced by defocus in rhesus monkeys. Methods Starting at age 3 weeks, monkeys were reared with −3 diopter (D; n = 10; 7-MX −3D/pl) or +3D (n = 6; 7-MX +3D/pl) spectacles over their treated eyes and zero-powered lenses over their fellow eyes. In addition, they were given 100 mg/kg of 7-MX orally twice daily throughout the lens-rearing period (age 147 ± 4 days). Comparison data were obtained from lens-reared controls (−3D/pl, n = 17; +3D/pl, n = 9) and normal monkeys (n = 37) maintained on a standard diet. Refractive status, corneal power, and axial dimensions were assessed biweekly. Results The −3D/pl and +3D/pl lens-reared controls developed compensating myopic (−2.10 ± 1.07 D) and hyperopic anisometropias (+1.86 ± 0.54 D), respectively. While the 7-MX +3D/pl monkeys developed hyperopic anisometropias (+1.79 ± 1.11 D) that were similar to those observed in +3D/pl controls, the 7-MX −3D/pl animals did not consistently exhibit compensating myopia in their treated eyes and were on average isometropic (+0.35 ± 1.96 D). The median refractive errors for both eyes of the 7-MX −3D/pl (+5.47 D and +4.38 D) and 7-MX +3D/pl (+5.28 and +3.84 D) monkeys were significantly more hyperopic than that for normal monkeys (+2.47 D). These 7-MX–induced hyperopic ametropias were associated with shorter vitreous chambers and thicker choroids. Conclusions In primates, 7-MX reduced the axial myopia produced by hyperopic defocus, augmented hyperopic shifts in response to myopic defocus, and induced hyperopia in control eyes. The results suggest that 7-MX has therapeutic potential in efforts to slow myopia progression. PMID:29368006

Femtosecond laser-assisted sub-Bowman keratomileusis versus laser-assisted subepithelial keratomileusis to correct myopic astigmatism.

PubMed

Gros-Otero, Juan; Garcia-Gonzalez, Montserrat; Teus, Miguel A; Iglesias-Iglesias, MariLuz; Gimenez-Vallejo, Carlos

To compare femtosecond laser-assisted sub-Bowman keratomileusis (FSBK) versus laser-assisted subepithelial keratomileusis (LASEK) to correct moderate to high myopic astigmatism. Retrospective, nonrandomized, interventional, comparative case series. A total of eight hundred and fifty-two eyes with myopic astigmatism of -1.5 diopters (D) or higher were included in the study. We compared 427 eyes treated with FSBK versus 425 eyes treated with LASEK with or without mitomycin C. Visual and refractive results were evaluated 1 day, 1 week, 3 and 6 months postoperatively. Six months postoperatively, the residual spherical defect was slightly but significantly higher in the LASEK group (+0.15±0.62D) than in the FSBK group (+0.09±0.35D) (P=0.05). The postoperative residual astigmatism was also slightly but significantly higher in the LASEK group (-0.38±0.52D) than in the FSBK group (-0.26±0.45D) (P=0.0005). No significant differences were found in the efficacy (0.98±0.17 versus 0.98±0.36, P=0.6) and safety indexes (1.04±0.16 versus 1.05±0.37, P=0.1) between FSBK and LASEK. The enhancement rate was significantly higher in the FSBK group (22.6%) than in the LASEK group (15.5%) (P=0.01). Both FSBK and LASEK are safe and effective procedures to correct moderate to high myopic astigmatism. Slightly better visual and refractive results were observed in FSBK-treated eyes in a 6-month follow-up. Copyright © 2016 Spanish General Council of Optometry. Published by Elsevier España, S.L.U. All rights reserved.

Laser in situ keratomileusis using optimized aspheric profiles and cyclotorsion control to treat compound myopic astigmatism with high cylinder.

PubMed

Alió, Jorge L; Plaza-Puche, Ana B; Martinez, Lorena M; Torky, Magda; Brenner, Luis F

2013-01-01

To evaluate the visual outcomes after laser in situ keratomileusis (LASIK) surgery to correct primary compound myopic astigmatism with high cylinder performed using a fast-repetition-rate excimer laser platform with optimized aspheric profiles and cyclotorsion control. Vissum Corporation and Division of Ophthalmology, Universidad Miguel Hernández, Alicante, Spain. Retrospective consecutive observational nonrandomized noncomparative case series. Eyes with primary compound myopic astigmatism and a cylinder power over 3.00 diopters (D) had uneventful LASIK with femtosecond flap creation and fast-repetition-rate excimer laser ablation with aspheric profiles and cyclotorsion control. Visual, refractive, and aberrometric outcomes were evaluated at the 6-month follow-up. The astigmatic correction was evaluated using the Alpins method and Assort software. The study enrolled 37 eyes (29 patients; age range 19 to 55 years). The significant reduction in refractive sphere and cylinder 3 months and 6 months postoperatively (P<.01) was associated with improved uncorrected distance visual acuity (P<.01). Eighty-seven percent of eyes had a spherical equivalent within ±0.50 D; 7.5% of eyes were retreated. There was no significant induction of higher-order aberrations (HOAs). The targeted and surgically induced astigmatism magnitudes were 3.23 D and 2.96 D, respectively, and the correction index was 0.91. The safety and efficacy indices were 1.05 and 0.95, respectively. Laser in situ keratomileusis for primary compound myopic astigmatism with high cylinder (>3.00 D) performed using a fast-repetition-rate excimer laser with optimized aspheric profiles and cyclotorsion control was safe, effective, and predictable and did not cause significant induction of HOAs. Copyright © 2012 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.

Do outside temperature and sunlight duration influence the outcome of laser refractive surgery? Results from the Hamburg Weather Study

PubMed Central

Neuhaus-Richard, Ines; Frings, Andreas; Görsch, Isabel Caroline; Druchkiv, Vasyl; Katz, Toam; Linke, Stephan Johannes; Richard, Gisbert

2014-01-01

Purpose To examine the impact of temperature and sunlight duration on refractive and visual outcome of laser-assisted in situ keratomileusis (LASIK) in myopic eyes. Setting University Medical Center Hamburg-Eppendorf, Germany, and Care Vision Refractive Centers, Germany. Design Retrospective, cross-sectional data analysis. Methods This study comprised 1,052 eyes of 1,052 consecutive myopic patients (419 males, 633 females; mean age at surgery 35.0±9.0 years) with a mean preoperative refractive spherical equivalent (SE) of −3.88±1.85 diopters (D). Two subgroups were defined, comprising patients undergoing surgery during either meteorological winter or summer. Manifest refraction, uncorrected, and corrected distant visual acuity (UDVA and CDVA) were assessed pre- and postoperatively. We applied robust regression analysis with efficiency index (EI), safety index (SI), and postoperative SE (in D) as dependent variables. Results At the 1-month (33.0±5.0 days) follow-up, the mean postoperative SE was −0.18±0.44 D. Bivariate comparisons showed that statistically significant better EI was related to days with lower temperature. We obtained a significant difference for SI which suggested that low temperature had a positive influence on SI. No change by more than one line on LogMAR scale was obtained. Conclusion Although being statistically significant, there was no clinically relevant difference in the outcome of LASIK, which demonstrates its highly standardized quality. Prospective, longitudinal studies are warranted to address meteorotropic reactions through evaluating defined meteorological parameters. PMID:24966665

Comparison of monochromatic aberrations in young adults with different visual acuity and refractive errors.

PubMed

Yazar, Seyhan; Hewitt, Alex W; Forward, Hannah; McKnight, Charlotte M; Tan, Alex; Mountain, Jenny A; Mackey, David A

2014-03-01

To compare the monochromatic aberrations in a large cohort of 20-year-old Australians with differing levels of visual acuity and explore the relationship between these aberrations and refractive error. Lions Eye Institute, Perth, Western Australia, Australia. Cross-sectional analysis of a population-based cohort. Monochromatic aberrations were measured using a Zywave II wavefront aberrometer with natural pupils in a dark room. The logMAR corrected distance visual acuity (CDVA) was measured monocularly under normal illumination. Cycloplegic autorefraction was also performed. The study enrolled 2039 eyes of 1040 participants. Data from 1007 right eyes were analyzed. The median CDVA and spherical equivalent were -0.06 logMAR (interquartile range [IQR], -0.10 to 0.00) and +0.25 diopters (D) (IQR, -0.38 to 0.63), respectively. The median 6.0 mm higher-order aberration (HOA) was 0.58 μm (IQR, 0.44 to 0.79). Coma-like aberrations and 3rd-, 4th-, and 5th-order HOAs were significantly different between subjects with a CDVA of -0.10 logMAR or better and those with a CDVA worse than -0.10 logMAR. Fourth-order aberrations Z(4,-4) (P=.024) and Z(4,-2) (P=.029) and 2nd-order aberration Z(2,0) (P<.001) differed significantly between myopic eyes, emmetropic eyes, and hyperopic eyes. Subjects with higher myopia had slightly higher total HOAs. The HOAs in this population were marginally higher than previously reported values. The findings confirm there is a difference in monochromatic aberrations between different vision and refractive groups. Results in this study will benefit decision-making processes in the clinical setting. Copyright © 2014 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.

Preliminary results of tracked laser-assisted in-situ keratomileusis (T-LASIK) for myopia and hyperopia using the autonomous technologies excimer laser system

NASA Astrophysics Data System (ADS)

Maguen, Ezra I.; Nesburn, Anthony B.; Salz, James J.

2000-06-01

A study was undertaken to assess the safety and efficacy of LASIK with the LADARVision laser by Autonomous Technologies, (Orlando, FL). The study included four subsets: Spherical myopia -- up to -11.00D, spherical hyperopia -- up to +6.00D. Both myopic and hyperopic astigmatism could be corrected, up to 6.00D of astigmatism. A total of 105 patients participated. Sixty-six patients were myopic and 39 were hyperopic. The mean (+/- SD) age was 42.8 +/- 9.3 years for myopia and 53.2 +/- 9.9 years for hyperopia. At 3 months postop. Sixty-one myopic eyes were available for evaluation. Uncorrected visual acuity was 20/20 in 70% of eyes and 20/40 in 92.9% of all eyes. The refractive outcome was within +/- 0.50D in 73.8% of eyes and within +/- 1.00D in 96.7 of eyes. Thirty-eight hyperopic eyes were available. Uncorrected visual acuity was 20/20 in 42.1% of eyes and 20/40 in 88% of all eyes. The refractive outcome was within +/- 0.50D in 57.9% of eyes and within +/- 1.00D in 86.8% of eyes. Complications were not sight threatening and were discussed in detail. Lasik with the LADARVision laser appears to be safe and effective.

Form deprivation and lens-induced myopia: are they different?

PubMed Central

Morgan, Ian G.; Ashby, Regan S.; Nickla, Debora L.; Guggenheim, Jeremy A.

2013-01-01

Animal models have been crucial in shaping our understanding of emmetropisation as an active, visually-guided mechanism for overcoming innate refractive errors. For instance, when a ‘minus’ power spectacle lens is mounted in front of the eye of a juvenile animal, the eye is cued to thin its choroid and accelerate its rate of axial elongation. Such altered ocular growth responses serve to attenuate the imposed defocus and so continue over a period of days, weeks or months (depending on the rate of emmetropisation of the species concerned) until the eye attains its optimal refraction. Notably, refracted without the minus lens in place, the eye of an animal emmetropising to a minus lens is myopic (its axial length now being excessive for its anterior segment optics). Similar ocular growth changes are seen with form deprivation, typically achieved by covering the eye with a frosted diffuser, and preventing the eye from receiving clear vision. However while both minus lens wear and form deprivation induce axial myopia, the absence of meaningful visual feedback allows growth to continue in an ‘open-loop’ manner in the latter case, limited mostly by the duration of treatment. Here, Ian Morgan and Regan Ashby present the evidence that form deprivation and lens-induced myopia share the same physiological mechanisms, while Debora Nickla presents the opposing evidence that the underlying mechanisms are different. PMID:23662966

Application of the ISNT rules on retinal nerve fibre layer thickness and neuroretinal rim area in healthy myopic eyes.

PubMed

Qiu, Kunliang; Wang, Geng; Lu, Xuehui; Zhang, Riping; Sun, Lixia; Zhang, Mingzhi

2018-03-01

We determined the applicability of inferior > superior > nasal > temporal (ISNT) rules on retinal nerve fibre layer (RNFL) thickness and rim area and evaluated the impact of various ocular factors on the performance of the ISNT rules in healthy myopic eyes. A total of 138 eyes from 138 healthy myopic subjects were included in this cross-sectional observational study. The peripapillary RNFL and optic disc in each eye were imaged with Cirrus HD optical coherence tomography (OCT) and Heidelberg Retina Tomograph II (HRT2), respectively. The performance of the inferior > superior (IS), inferior > superior > nasal > temporal (IST) and ISNT rules on RNFL thickness and rim area was determined and compared between low-to-moderate myopia and high myopia. The effects of ocular factors [including axial length, disc area, disc tilt, disc torsion, disc-fovea angle (DFA) and retina artery angle] on the performance of ISNT rules were evaluated with logistic regression analysis. The mean axial length and refractive error were 25.57 ± 1.09 mm (range, 22.52-28.77 mm) and -5.12 ± 2.30 D [range, -9.63 to -0.50 dioptres (D)], respectively. Sixty-three per cent of the healthy eyes were compliant with the ISNT rule on rim area, while ISNT rule on RNFL thickness was followed in only 11.6% of the included eyes. For rim area, smaller disc area was significantly associated with increased compliance of the IS rule (odds ratio: 0.46, p = 0.039), IST rule (odds ratio: 0.46, p = 0.037) and ISNT rule (odds ratio: 0.44, p = 0.030). For RNFL thickness, greater DFA was significantly associated with increased compliance of the IS and IST rules (odds ratio: 1.30, p < 0.001; odds ratio: 1.19, p = 0.006, respectively). In healthy myopic subjects, 88.4% and 37% of eyes did not comply with the ISNT rule on RNFL thickness and rim area, respectively. Due to significant low compliance in healthy eyes, the ISNT rule and its variants have limited potential utility in diagnosing glaucoma in myopic subjects. © 2017 Acta Ophthalmologica Scandinavica Foundation. Published by John Wiley & Sons Ltd.

Topography-Guided Transepithelial Surface Ablation in the Treatment of Moderate to High Astigmatism.

PubMed

Chen, Xiangjun; Stojanovic, Aleksandar; Simonsen, David; Wang, Xiaorui; Liu, Yanhua; Utheim, Tor Paaske

2016-06-01

To analyze the outcomes of treatment of astigmatism of 2.00 diopters (D) or greater with topography-guided transepithelial surface ablation. Retrospective analysis of a series of 206 eyes divided into two groups: myopic astigmatism (153 eyes) and mixed astigmatism (53 eyes). All cases were treated with topography-guided transepithelial surface ablation. Efficacy, safety, and predictability were evaluated, and vector analysis of cylindrical correction was performed. The median preoperative spherical equivalent was -2.63 and -0.63 D for the myopic and mixed astigmatism groups, respectively, with median cylinder of -2.50 D. Postoperative uncorrected distance visual acuity was 20/20 or better in 92% and 83% of eyes in the myopic and mixed astigmatism groups, respectively; the corresponding efficacy indices were 1.00 and 0.96 and residual astigmatism of 0.50 D or less was present in 82.4% and 56.7% of eyes in the myopic and mixed astigmatism groups, respectively. The arithmetic mean magnitude of the difference vector was 0.38 (myopic) and 0.65 (mixed) D. Difference vector magnitude was positively correlated with the magnitude of target induced astigmatism in both groups. The geometric mean coefficient of adjustment index was 1.04 and 1.19, representing undercorrection of 4% and 19% in the myopic and mixed astigmatism groups, respectively. Topography-guided transepithelial ablation is a safe, effective, and predictable treatment for moderate to high astigmatism. [J Refract Surg. 2016;32(6):418-425.]. Copyright 2016, SLACK Incorporated.

Evaluation of a New Software Version of the RTVue Optical Coherence Tomograph for Image Segmentation and Detection of Glaucoma in High Myopia.

PubMed

Holló, Gábor; Shu-Wei, Hsu; Naghizadeh, Farzaneh

2016-06-01

To compare the current (6.3) and a novel software version (6.12) of the RTVue-100 optical coherence tomograph (RTVue-OCT) for ganglion cell complex (GCC) and retinal nerve fiber layer thickness (RNFLT) image segmentation and detection of glaucoma in high myopia. RNFLT and GCC scans were acquired with software version 6.3 of the RTVue-OCT on 51 highly myopic eyes (spherical refractive error ≤-6.0 D) of 51 patients, and were analyzed with both the software versions. Twenty-two eyes were nonglaucomatous, 13 were ocular hypertensive and 16 eyes had glaucoma. No difference was seen for any RNFLT, and average GCC parameter between the software versions (paired t test, P≥0.084). Global loss volume was significantly lower (more normal) with version 6.12 than with version 6.3 (Wilcoxon signed-rank test, P<0.001). The percentage agreement (κ) between the clinical (normal and ocular hypertensive vs. glaucoma) and the software-provided classifications (normal and borderline vs. outside normal limits) were 0.3219 and 0.4442 for average RNFLT, and 0.2926 and 0.4977 for average GCC with versions 1 and 2, respectively (McNemar symmetry test, P≥0.289). No difference in average RNFLT and GCC classification (McNemar symmetry test, P≥0.727) and the number of eyes with at least 1 segmentation error (P≥0.109) was found between the software versions, respectively. Although GCC segmentation was improved with software version 6.12 compared with the current version in highly myopic eyes, this did not result in a significant change of the average RNFLT and GCC values, and did not significantly improve the software-provided classification for glaucoma.

The opportunistic screening of refractive errors in school-going children by pediatrician using enhanced Brückner test.

PubMed

Jain, Piyush; Kothari, Mihir T; Gode, Vaibhav

2016-10-01

The aim of this study was to compare the results of enhanced Brückner test (EBT) performed by a pediatrician and an experienced pediatric ophthalmologist. In this prospective double-masked cohort study, a pediatrician and a pediatric ophthalmologist performed the EBT in a classroom of a school in semi-dark lighting condition using a direct ophthalmoscope. The results of the test were compared using 2 × 2 Bayesian table and kappa statistics. The findings of the pediatric ophthalmologists were considered gold standard. Two hundred and thirty-six eyes of 118 subjects, mean age 6.8 ± 0.5 years (range, 5.4-7.8 years), were examined. The time taken to complete this test was <10 s per subject. The ophthalmologist identified 59 eyes as ametropic (12 hyperopic and 47 myopic eyes) and 177 as emmetropic compared to 61 eyes as ametropic and 175 emmetropic by pediatrician. The prevalence of the test positive was 25.9%. The sensitivity of the pediatrician was 90.2%, specificity was 97.7%, predictive value of the positive test was 93.2%, and predictive value of the negative test was 96.6%. The clinical agreement (kappa) between the pediatric ophthalmologist and the pediatrician was 0.9. The results of the EBT performed by pediatrician were comparable to that of an experienced pediatric ophthalmologist. Opportunistic screening of refractive errors using EBT by a pediatrician can be an important approach in the detection of ametropia in children.

Nearwork-induced transient myopia in preadolescent Hong Kong Chinese.

PubMed

Wolffsohn, James Stuart; Gilmartin, Bernard; Li, Roger Wing-hong; Edwards, Marion Hastings; Chat, Sandy Wing-shan; Lew, John Kwok-fai; Yu, Bibianna Sin-ying

2003-05-01

To compare the magnitude and time course of nearwork-induced transient myopia (NITM) in preadolescent Hong Kong Chinese myopes and emmetropes. Forty-five Hong Kong Chinese children, 35 myopes and 10 emmetropes aged 6 to 12 years (median, 7.5), monocularly viewed a letter target through a Badal lens for 5 minutes at either 5.00- or 2.50-D accommodative demand, followed by 3 minutes of viewing the equivalent target at optical infinity. Accommodative responses were measured continuously with a modified, infrared, objective open-field autorefractor. Accommodative responses were also measured for a countercondition: viewing of a letter target for 5 minutes at optical infinity, followed by 3 minutes of viewing the target at a 5.00-D accommodative demand. The results were compared with tonic accommodation and both subject and family history of refractive error. Retinal-blur-driven NITM was significantly greater in Hong Kong Chinese children with myopic vision than in the emmetropes after both near tasks, but showed no significant dose effect. The NITM was still evident 3 minutes after viewing the 5.00-D near task for 5 minutes. The magnitude of NITM correlated with the accommodative drift after viewing a distant target for more than 4 minutes, but was unrelated to the subjects' or family history of refractive error. In a preadolescent ethnic population with known predisposition to myopia, there is a significant posttask blur-driven accommodative NITM, which is sustained for longer than has previously been found in white adults.

Updates of pathologic myopia.

PubMed

Ohno-Matsui, Kyoko; Lai, Timothy Y Y; Lai, Chi-Chun; Cheung, Chiu Ming Gemmy

2016-05-01

Complications from pathologic myopia are a major cause of visual impairment and blindness, especially in east Asia. The eyes with pathologic myopia may develop loss of the best-corrected vision due to various pathologies in the macula, peripheral retina and the optic nerve. Despite its importance, the definition of pathologic myopia has been inconsistent. The refractive error or axial length alone often does not adequately reflect the 'pathologic myopia'. Posterior staphyloma, which is a hallmark lesion of pathologic myopia, can occur also in non-highly myopic eyes. Recently a revised classification system for myopic maculopathy has been proposed to standardize the definition among epidemiological studies. In this META-PM (meta analyses of pathologic myopia) study classification, pathologic myopia was defined as the eyes having chorioretinal atrophy equal to or more severe than diffuse atrophy. In addition, the advent of new imaging technologies such as optical coherence tomography (OCT) and three dimensional magnetic resonance imaging (3D MRI) has enabled the detailed observation of various pathologies specific to pathologic myopia. New therapeutic approaches including intravitreal injections of anti-vascular endothelial growth factor agents and the advance of vitreoretinal surgeries have greatly improved the prognosis of patients with pathologic myopia. The purpose of this review article is to provide an update on topics related to the field of pathologic myopia, and to outline the remaining issues which need to be solved in the future. Copyright © 2016 Elsevier Ltd. All rights reserved.

Guiding flying-spot laser transepithelial phototherapeutic keratectomy with optical coherence tomography

PubMed Central

Li, Yan; Yokogawa, Hideaki; Tang, Maolong; Chamberlain, Winston; Zhang, Xinbo; Huang, David

2017-01-01

PURPOSE To analyze transepithelial phototherapeutic keratectomy (PTK) results using optical coherence tomography (OCT) and develop a model to guide the laser dioptric and depth settings. SETTING Casey Eye Institute, Portland, Oregon, USA. DESIGN Prospective nonrandomized case series. METHODS Patients with superficial corneal opacities and irregularities had transepithelial PTK with a flying-spot excimer laser by combining wide-zone myopic and hyperopic astigmatic ablations. Optical coherence tomography was used to calculate corneal epithelial lenticular masking effects, guide refractive laser settings, and measure opacity removal. The laser ablation efficiency and the refractive outcome were investigated using multivariate linear regression models. RESULTS Twenty-six eyes of 20 patients received PTK to remove opacities and irregular astigmatism due to scar, dystrophy, radial keratotomy, or previous corneal surgeries. The uncorrected distance visual acuity (UDVA) and corrected distance visual acuity (CDVA) were significantly improved (P < .01) by 3.7 Snellen lines and 2.0 Snellen lines, respectively, to a mean of 20/41.2 and 20/22.0, respectively. Achieved laser ablation depths were 31.3% (myopic ablation) and 63.0% (hyperopic ablation) deeper than the manufacturer’s nomogram. The spherical equivalent of the corneal epithelial lenticular masking effect was 0.73 diopter ± 0.61 (SD). The refractive outcome highly correlated to the laser settings and epithelial lenticular masking effect (Pearson R = 0.96, P < .01). The ablation rate of granular dystrophy opacities appeared to be slower. Smoothing ablation under masking fluid was needed to prevent focal steep islands in these cases. CONCLUSIONS The OCT-measured ablation depth efficiency could guide opacity removal. The corneal epithelial lenticular masking effect could refine the spherical refractive nomogram to achieve a better refractive outcome after transepithelial ablation. PMID:28532939

Guiding flying-spot laser transepithelial phototherapeutic keratectomy with optical coherence tomography.

PubMed

Li, Yan; Yokogawa, Hideaki; Tang, Maolong; Chamberlain, Winston; Zhang, Xinbo; Huang, David

2017-04-01

To analyze transepithelial phototherapeutic keratectomy (PTK) results using optical coherence tomography (OCT) and develop a model to guide the laser dioptric and depth settings. Casey Eye Institute, Portland, Oregon, USA. Prospective nonrandomized case series. Patients with superficial corneal opacities and irregularities had transepithelial PTK with a flying-spot excimer laser by combining wide-zone myopic and hyperopic astigmatic ablations. Optical coherence tomography was used to calculate corneal epithelial lenticular masking effects, guide refractive laser settings, and measure opacity removal. The laser ablation efficiency and the refractive outcome were investigated using multivariate linear regression models. Twenty-six eyes of 20 patients received PTK to remove opacities and irregular astigmatism due to scar, dystrophy, radial keratotomy, or previous corneal surgeries. The uncorrected distance visual acuity and corrected distance visual acuity were significantly improved (P < .01) by 3.7 Snellen lines and 2.0 Snellen lines, respectively, to a mean of 20/41.2 and 20/22.0, respectively. Achieved laser ablation depths were 31.3% (myopic ablation) and 63.0% (hyperopic ablation) deeper than the manufacturer's nomogram. The spherical equivalent of the corneal epithelial lenticular masking effect was 0.73 diopter ± 0.61 (SD). The refractive outcome highly correlated to the laser settings and epithelial lenticular masking effect (Pearson R = 0.96, P < .01). The ablation rate of granular dystrophy opacities appeared to be slower. Smoothing ablation under masking fluid was needed to prevent focal steep islands in these cases. The OCT-measured ablation depth efficiency could guide opacity removal. The corneal epithelial lenticular masking effect could refine the spherical refractive nomogram to achieve a better refractive outcome after transepithelial ablation. Copyright © 2017 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.

Aspheric photorefractive keratectomy for myopia and myopic astigmatism with the SCHWIND AMARIS laser: 2 years postoperative outcomes

PubMed Central

Aslanides, Ioannis M.; Padroni, Sara; Arba-Mosquera, Samuel

2012-01-01

Purpose To evaluate mid-term refractive outcomes and higher order aberrations of aspheric PRK for low, moderate and high myopia and myopic astigmatism with the AMARIS excimer laser system (SCHWIND eye-tech-solutions GmbH, Kleinostheim, Germany). Methods This prospective longitudinal study evaluated 80 eyes of 40 subjects who underwent aspheric PRK. Manifest refractive spherical equivalent (MRSE) of up to −10.00 diopters (D) at the spectacle plane with cylinder up to 3.25 was treated. Refractive outcomes and corneal wavefront data (6 mm pupil to the 7th Zernike order) were evaluated out to 2 years postoperatively. Statistical significance was indicated by P < 0.05. Results The mean manifest spherical equivalent refraction (MRSE) was −4.77 ± 2.45 (range, −10.00 D to −0.75 D) preoperatively and −0.12 ± 0.35 D (range, −1.87 D to +0.75 D) postoperatively (P < 0.0001). Postoperatively, 91% (73/80) of eyes had an MRSE within ±0.50 D of the attempted. No eyes lost one or more lines of corrected distance visual acuity (CDVA) and CDVA increased by one or more lines in 26% (21/80) of eyes. Corneal trefoil and corneal higher order aberration root mean square did not statistically change postoperatively compared to preoperatively (P > 0.05, both cases). There was a statistical increase in postoperative coma (+0.12 μm) and spherical aberration (+0.14 μm) compared to preoperatively (P < 0.001, both cases). Conclusion Aspheric PRK provides excellent visual and refractive outcomes with induction in individual corneal aberrations but not overall corneal aberrations.

Postoperative Corneal Asphericity in Low, Moderate, and High Myopic Eyes After Transepithelial PRK Using a New Pulse Allocation.

PubMed

Lin, David T C; Holland, Simon P; Verma, Shwetabh; Hogden, John; Arba-Mosquera, Samuel

2017-12-01

To evaluate the postoperative asphericity in low, moderate, and high myopic eyes after combined transepithelial photorefractive keratectomy and SmartSurf ACE treatment (SCHWIND eye-tech-solutions GmbH, Kleinostheim, Germany). In this retrospective case series, the outcomes of myopic SmartSurf ACE were evaluated at 3 months postoperatively in 106 eyes and divided into low (less than -4.125 diopters [D]), moderate (-4.125 to -6.25 D), and high (more than -6.25 D) myopia groups. In all cases, standard examinations and preoperative and postoperative corneal topography (SCHWIND Sirius) were performed. The analysis comprised evaluating the change in asphericity versus planned correction, comparing expected and achieved postoperative asphericity for all eyes, and comparison of the three groups in terms of the preoperative and postoperatively expected and achieved asphericity. RESULTS At 3 months postoperatively, the low myopia group (n = 33) improved average negative asphericity (Q = -0.04 ± 0.17 preoperative vs -0.19 ± 0.20 postoperative, P < .05). The moderate myopia group (n = 35) maintained or slightly improved average negative asphericity (Q = -0.07 ± 0.14 preoperative vs -0.05 ± 0.24 postoperative, P = .35). For the high myopia group (n = 38), the eyes became more oblate compared to the preoperative status (Q = -0.09 ± 0.15 preoperative vs 0.62 ± 0.70 postoperative, P < .05). In terms of asphericity, the difference between the three groups was not statistically significant preoperatively (P > .10), but showed significant differences postoperatively (P < .007). The cohort's average preoperative corrected distance visual acuity was 0.01 ± 0.04 logMAR (range: 0.0 to 0.18 logMAR) and uncorrected distance visual acuity was 0.03 ± 0.08 logMAR (range: -0.12 to 0.40 logMAR) 3 months postoperatively. SmartSurf ACE maintained or slightly improved preoperative corneal asphericity for low to moderate myopic corrections (up to -6.00 D). This may provide advantages in the quality of vision and the onset of presbyopic symptoms after laser refractive surgery in myopic patients. [J Refract Surg. 2017;33(12):820-826.]. Copyright 2017, SLACK Incorporated.

Retinal vascular nonperfusion in siblings with Dandy-Walker variant.

PubMed

Rusu, Irene; Gupta, Mrinali Patel; Patel, Samir N; Oltra, Erica; Chan, R V Paul

2016-04-01

We report the case of a 2-month-old girl with Dandy-Walker variant who presented with strabismus, pathologic myopia measuring -16.00 D in each eye, diffuse chorioretinal atrophy and pigment mottling in the macula of both eyes, and areas of retinal capillary nonperfusion in both eyes. The patient's brother also has Dandy-Walker variant and was found to have bilateral severe myopia, myopic fundi, tilted optic disks with peripapillary atrophy, extensive areas of white without pressure, areas of lattice degeneration, and several chronic-appearing atrophic retinal holes surrounded by pigmentation. We hypothesize that children with Dandy-Walker variant may present with refractive errors such as pathologic myopia and with diverse retinal findings, including retinal ischemia. A lower threshold for ophthalmologic examination may be considered in this population. Copyright © 2016 American Association for Pediatric Ophthalmology and Strabismus. Published by Elsevier Inc. All rights reserved.

Ablation algorithms and corneal asphericity in myopic correction with excimer lasers

NASA Astrophysics Data System (ADS)

Iroshnikov, Nikita G.; Larichev, Andrey V.; Yablokov, Michail G.

2007-06-01

The purpose of this work is studying a corneal asphericity change after a myopic refractive correction by mean of excimer lasers. As the ablation profile shape plays a key role in the post-op corneal asphericity, ablation profiles of recent lasers should be studied. The other task of this research was to analyze operation (LASIK) outcomes of one of the lasers with generic spherical ablation profile and to compare an asphericity change with theoretical predictions. The several correction methods, like custom generated aspherical profiles, may be utilized for mitigation of unwanted effects of asphericity change. Here we also present preliminary results of such correction for one of the excimer lasers.

Mild Myopic Astigmatism Corrected by Accidental Flap Complication: A Case Report

PubMed Central

Fahed, Daoud C; Fahed, Charbel D

2009-01-01

A 35-year-old female presented for laser in-situ keratomileusis (LASIK). Her preoperative eye exam was normal, with a preop refraction of OD −2.50 D Sph +1.25 D Cyl ×175 and OS −2.75 D Sph +1.50 D Cyl ×165 (cycloplegic and manifest), with 20/20 BCVA OU. The central pachymetry reading was 553 μm in the right eye. Preoperative topography was normal. At the start of the pendular microkeratome path, some resistance was felt, but the microkeratome continued along its path. Upon inspection of the flap, there was a central rectangle of intact epithelium with two mirror-image flaps on both sides. The flap was repositioned and LASIK was discontinued. The cornea healed with two faint thin linear vertical parallel scars at the edge of the pupil. Postoperative inspection of the blade revealed central blunting. One month postoperatively, the uncorrected visual acuity (UCVA) was 20/20. Manifest and cycloplegic refractions were plano. This is an interesting case of accidental flap complication resulting in the correction of mild myopic astigmatism. PMID:20404996

Simulation of the impact of refractive surgery ablative laser pulses with a flying-spot laser beam on intrasurgery corneal temperature.

PubMed

Shraiki, Mario; Arba-Mosquera, Samuel

2011-06-01

To evaluate ablation algorithms and temperature changes in laser refractive surgery. The model (virtual laser system [VLS]) simulates different physical effects of an entire surgical process, simulating the shot-by-shot ablation process based on a modeled beam profile. The model is comprehensive and directly considers applied correction; corneal geometry, including astigmatism; laser beam characteristics; and ablative spot properties. Pulse lists collected from actual treatments were used to simulate the temperature increase during the ablation process. Ablation efficiency reduction in the periphery resulted in a lower peripheral temperature increase. Steep corneas had lesser temperature increases than flat ones. The maximum rise in temperature depends on the spatial density of the ablation pulses. For the same number of ablative pulses, myopic corrections showed the highest temperature increase, followed by myopic astigmatism, mixed astigmatism, phototherapeutic keratectomy (PTK), hyperopic astigmatism, and hyperopic treatments. The proposed model can be used, at relatively low cost, for calibration, verification, and validation of the laser systems used for ablation processes and would directly improve the quality of the results.

[Peripheral refraction: cause or effect of refraction development?

PubMed

Tarutta, E P; Iomdina, E N; Kvaratskheliya, N G; Milash, S V; Kruzhkova, G V

to study peripheral refraction and the shape of the eyeball in children with different clinical refraction. Using an original method, peripheral refraction was measured at 10-12 degrees temporally and nasally from the fovea in 56 right eyes with different clinical, or axial, refraction of 20 boys and 36 girls aged 7 to 16 years (11.9±1.17 years on average). The shape of the eyeball was judged of by the ratio of its anterior-posterior axial length (AL) to horizontal diameter (HD). The incidence and value of peripheral myopic defocus in children appeared to decrease with clinical refraction increasing from high hyperopia to high myopia. This was the first time, mixed peripheral refraction was found in children, occurring more frequently in higher myopia. This mixed peripheral defocus, shown to be a transitional stage between relative peripheral myopia and relative hyperopia, indicates non-uniform stretching of posterior pole tissues in the course of refraction development and myopia progression. As ocular refraction increases from high hyperopia to high myopia, the growth of AL outpaces that of HD. Obviously, natural peripheral defocus results from changes in size and shape of the eyeball in the course of refraction development.

Long -term effects of optical defocus on eye growth and refractogenesis.

PubMed

Tarutta, Elena; Khodzhabekyan, Narine; Filinova, Oksana; Milash, Sergei; Kruzhkova, Galina

The aim of this paper was to study the effect of binocular and alternating monocular myopic constant defocus prescribed in spectacle format on myopia onset and progression in children. 129 children aged 5–12 years were divided into 4 groups: 48 children aged 5–8 years (1st group) with emmetropia and risk factors of myopia development were prescribed the continuous wearing of plus lenses to induce myopia of 1.0 D. 46 children aged 7–11 years (2nd group) with low myopia from −0.75 to −2.25 D were prescribed 2 pairs of spectacles for alternating continuous wearing. One eye was corrected for distance to obtain residual myopia in spectacles of about 0.50 D, and the fellow eye was corrected to obtain residual or induced myopia of about 1.50 D. The children changed spectacles every day. Control data were obtained from 15 children aged 6–9 years (1st control group) with pseudomyopia with no correction administered, and 20 low myopic children aged 7–12 years (2nd control group) wearing conventional spectacle correction. Autorefractometry before and after cycloplegia and ultrasound biometry were performed. A hyperopic shift caused by thinning of the crystalline lens and deepening of the anterior chamber in all patients of the 1st group was observed after 1 month and persisted over the follow -up period. Horizontal diameter (HD) increased more than 3 times as much as the axial length (AL). No cases of myopia onset were observed during the 9 -year follow -up period. 36 (81.8%) children of the 2nd group had stable refraction over the 4 year follow up, an insignificant increase in the AL and a significant increase in the HD were revealed. A 3-year follow -up revealed an increase in cycloplegic refraction in both control groups; the AL increased significantly, while the HD showed an insignificant increase. Permanent low myopic defocus of the image in binocular spectacle format inhibits eye growth and refraction shift to myopia in children with low hyperopia, emmetropia and low myopia. The method of alternating monolateral low myopic defocus arrests the myopia progression in 81.8% of children with low myopia for 4 years and 66% for 7 years.

Accuracy of PlusOptix A09 distance refraction in pediatric myopia and hyperopia.

PubMed

Payerols, Arnaud; Eliaou, Claudie; Trezeguet, Véronique; Villain, Max; Daien, Vincent

2016-06-01

The PlusOptix photoscreeners (PlusOptix GmbH, Nuremberg, Germany) is used in many vision screening programs. The purpose of the present study was to further explore the accuracy of the PlusOptix A09 photoscreener in children with ametropia (myopia or hyperopia). A total of 70 eyes (35 children) were prospectively included. Before administration with the cycloplegia treatment 1 % cyclopentolate hydrochloride, children underwent refraction measurement with the PlusOptix A09. A refraction was then performed after cycloplegia with either Retinomax hand-held or Nidek autorefractor before and after 3 years old, respectively. The median (interquartile range) age was 58 (18 to 86) months. The mean (SD) spherical equivalent differed between PlusOptix A09 and cycloplegic autorefraction (+0.54 [1.82] D vs +1.06 [2.04] D, p = 0.04). PlusOptix A09 refraction was positively correlated with cycloplegic autorefraction (r = 0.81, p < 0.001) with higher coefficient in myopic than in hyperopic children (r = 0.91, p = 0.0002 and r = 0.52, p = 0.01, respectively). The mean (SD) difference between PlusOptix A09 and cycloplegic autorefraction was higher with hyperopia than myopia (0.73 [1.34] vs 0.05 [0.66], p = 0.01). The proportion of children with < 1-D difference between cycloplegic and PlusOptix A09 refraction was 68.8 %, higher with myopia than hyperopia (90 % vs 54.5 %, p = 0.01). The spherical equivalent value with non-cycloplegic PlusOptix A09 refraction is closer to that with cycloplegic autorefraction than non-cycloplegic autorefraction. The PlusOptix A09 photoscreener underestimated the hyperopia of 0.73 D and slightly overestimated myopia of 0.05 D. The PlusOptix A09 could be used for screening with higher accuracy in myopic than hyperopic children.

Clinical outcomes of laser in situ keratomileusis with an aberration-neutral profile centered on the corneal vertex comparing vector planning with manifest refraction planning for the treatment of myopic astigmatism.

PubMed

Arbelaez, Maria Clara; Alpins, Noel; Verma, Shwetabh; Stamatelatos, George; Arbelaez, Juan Guillermo; Arba-Mosquera, Samuel

2017-12-01

To evaluate clinical outcomes of laser in situ keratomileusis (LASIK) with an aberration-neutral profile centered on the estimated visual axis (considering 70% of the pupil offset toward the corneal vertex) comparing vector planning with manifest refraction planning for the treatment of myopic astigmatism. Muscat Eye Laser Center, Muscat, Sultanate of Oman, Muscat, Oman. Retrospective case series. The outcomes were evaluated at a 6-month follow-up in eyes showing ocular residual astigmatism (ORA) over 0.75 diopters (D) preoperatively. Eighty-five treatments were based on manifest astigmatism (preoperative sphere -2.11 D ± 1.3 [SD], cylinder -0.90 ± 1.0 D), and 79 treatments were based on vector planning (preoperative sphere -2.46 ± 1.5 D, cylinder -0.78 ± 0.79 D). At a 6-month follow-up, 128 patients (164 eyes) were evaluated and no significant differences were observed between the 2 groups in terms of difference between corrected distance visual acuity and uncorrected distance visual acuity (UDVA) (P = .1, t test and Fisher exact test Snellen lines 1 or better, P = .4) and postoperative UDVA (P = .05, t test and Fisher exact test for UDVA 20/16 or better, P = .3). Significant differences were observed between the 2 groups in terms of achieved spherical equivalent (P = .04), corneal toricity, and ORA (P < .001, t test and Fisher exact test for ORA ≤0.75 D, P < .001). Performing LASIK for myopic astigmatism with the vector planning approach resulted in comparable visual outcomes to manifest refraction planning. Copyright © 2017 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.

Astigmatism among myopics and its changes from childhood to adult age: a 23-year follow-up study.

PubMed

Pärssinen, Olavi; Kauppinen, Markku; Viljanen, Anne

2015-05-01

To study the prevalence of and changes in astigmatism from the onset of myopia at school age. Two hundred and forty myopic schoolchildren (mean age 10.9 years), with no previous spectacles, were recruited during 1983-1984 to a randomized 3-year clinical trial of bifocal treatment of myopia. Three annual examinations with subjective cycloplegic refraction were performed for 237-238 subjects. Subsequent examinations were performed at the mean ages of 23.2 and 33.9 years for 178 and 163 subjects, and the last examination, including data from prescriptions of different ophthalmologists, for 32 subjects. Corneal topography was studied at baseline, at the 3-year follow-up and at the two adulthood follow-ups. Prevalence and changes in refractive astigmatism (RA), in its polar values J0 and J45, and corneal astigmatism (CA) were studied. Mean RA of the right eye increased during follow-up from 0.26 D (SD) ± 0.30 to 0.79 D ± 0.74. Mean CA was 1.07 D ± 0.74 at study end. The prevalence of RA ≥0.25 or ≥1.00 D increased from 54.9 and 3.8% to 83.4 and 34.4%, respectively. The main direction of the axis of RA and its polar value J0 and CA changed mainly through sphericity, from against the rule (ATR) to with the rule during the follow-up. There was a negative correlation between RA and spherical refraction in the ATR group at end of follow-up. Changes in RA were associated with increase in myopia and with changes in CA. The prevalence and mean amount of RA associated with CA increased, and the axis of astigmatism changed among myopics during the 23-year follow-up. © 2014 Acta Ophthalmologica Scandinavica Foundation. Published by John Wiley & Sons Ltd.

Astigmatism and Refractive Outcome After Late In-The-Bag Intraocular Lens Dislocation Surgery: A Randomized Clinical Trial.

PubMed

Kristianslund, Olav; Østern, Atle Einar; Drolsum, Liv

2017-09-01

To compare surgically induced astigmatism (SIA) and refractive outcomes between two operation methods for late in-the-bag IOL dislocation. In this prospective, randomized, parallel-group clinical trial, 104 patients (eyes) were assigned to IOL repositioning by scleral suturing 1.5- to 2-mm posterior to limbus (n = 54) or IOL exchange with a retropupillar iris-claw IOL using a 5.5-mm scleral pocket incision (n = 50). The SIA was determined by vector analysis through conversion of corneal cylinders to Cartesian coordinates, and is presented as magnitude in diopters @ direction in degrees (D @ °). Follow-up was 6 months. The SIA was 0.24 D @ 8° for IOL repositioning and 0.65 D @ 171° for IOL exchange, which was a nonsignificant group difference (X coordinate: P = 0.08; Y coordinate: P = 0.16). Mean SIA magnitude was 0.60 ± 0.50 D and 1.12 ± 0.85 D, respectively (P < 0.001). Mean postoperative spherical equivalent was -1.6 ± 1.6 D after IOL repositioning and -0.5 ± 1.0 D after IOL exchange (P < 0.001). For IOL repositioning, this represented a mean myopic shift of -0.7 ± 1.1 D compared with before the IOL dislocation (P < 0.001). For IOL exchange, it was within ±1 D of target refraction in 83% of the patients. Surgically induced astigmatism was modest in both operation groups, albeit with a tendency of being more pronounced for IOL exchange. Repositioning surgery led to a myopic shift, whereas exchange surgery provided good refractive predictability.

One-year refractive results, contrast sensitivity, high-order aberrations and complications after myopic small-incision lenticule extraction (ReLEx SMILE).

PubMed

Sekundo, Walter; Gertnere, Jana; Bertelmann, Thomas; Solomatin, Igor

2014-05-01

To report one year results of the first cohort of routine refractive lenticule extraction through a small incision (ReLEx SMILE) for correction of myopia and myopic astigmatism. Fifty-four eyes of 27 patients with spherical equivalent of -4.68 ± 1.29D who underwent routine ReLEx SMILE by a single surgeon were prospectively followed-up for 1 year. We used the VisuMax femtosecond laser system (Carl Zeiss Meditec AG, Germany) with a 500 kHz repetition rate. Folow-up intervals were at 1 day, 1 week, 1, 3, 6, and 12 months after surgery. We obtained following parameters: uncorrected (UDVA) and distance-corrected visual acuity (CDVA), contrast sensitivity, and wave front measurements. We also recorded all complications. Because of suction loss in one eye, 12-month results were obtained in 53 eyes as follows. After 1 year, 88% of eyes with plano target had an UDVA of 20/20 or better. Twelve percent of eyes lost 1 line of CDVA, while 31% gained 1 line and 3% gained 2 lines. The mean SE after 1 year was -0.19 ± 0.19. The mean refraction change between month 1 and 12 was 0.08 D. Neither mesopic nor photopic contrast sensitivity showed any significant changes. The high-order aberrations (HOA) increased from 0.17 to 0.27 μm (Malacara notation). No visually threatening complications were observed. In this first cohort, ReLEx SMILE produced satisfactory refractive outcomes with moderate induction of HOA and unaffected contrast sensitivity after 1 year.

Peripheral refraction in 7- and 14-year-old children in central China: the Anyang Childhood Eye Study.

PubMed

Li, Shi-Ming; Li, Si-Yuan; Liu, Luo-Ru; Zhou, Yue-Hua; Yang, Zhou; Kang, Meng-Tian; Li, He; Yang, Xiao-Yuan; Wang, Yi-Peng; Zhan, Si-Yan; Mitchell, Paul; Wang, Ningli; Atchison, David A

2015-05-01

To determine the distribution of peripheral refraction, including astigmatism, in 7- and 14-year-old Chinese children. 2134 7-year-old and 1780 14-year-old children were measured with cycloplegic central and horizontal peripheral refraction (15° and 30° at temporal and nasal visual fields). 7- and 14-year-old children included 9 and 594, respectively, with moderate and high myopia (≤-3.0 D), 259 and 831 with low myopia (-2.99 to -0.5 D), 1207 and 305 with emmetropia (-0.49 to +1.0 D), and 659 and 50 with hyperopia (>1.0 D), respectively. Myopic children had relative peripheral hyperopia while hyperopic and emmetropic children had relative peripheral myopia, with greater changes in relative peripheral refraction occurring in the nasal than the temporal visual field. The older group had the greater relative peripheral hyperopia and higher peripheral J180. Both age groups showed positive slopes of J45 across the visual field, with greater slopes in the older group. Myopic children in mainland China have relative peripheral hyperopia while hyperopic and emmetropic children have relative peripheral myopia. Significant differences exist between 7- and 14-year-old children, with the latter showing more relative peripheral hyperopia, greater rate of change in J45 across the visual field, and higher peripheral J180. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/permissions.

Early visual outcomes and optical quality after femtosecond laser small-incision lenticule extraction for myopia and myopic astigmatism correction of over -10 dioptres.

PubMed

Qin, Bing; Li, Meiyan; Chen, Xun; Sekundo, Walter; Zhou, Xingtao

2018-05-01

To investigate early visual and refractive outcomes, corneal stability and optical quality after femtosecond laser small-incision lenticule extraction (SMILE) for treating myopia and myopic astigmatism over -10 D. Thirty eyes (30 patients) with myopia and myopic astigmatism of over -10 D were treated with VisuMax ® femtosecond laser (version 3.0; Carl Zeiss Meditec AG, Jena, Germany). Six months postoperative safety, efficacy and predictability were evaluated. Corneal Scheimpflug topography was measured preoperatively, 1 day, 3 months and 6 months postoperatively. Wavefront aberrations were measured preoperatively, 3 months and 6 months postoperatively. Six months postoperatively, LogMAR uncorrected and corrected distance visual acuity (CDVA) were -0.013 ± 0.086 and -0.073 ± 0.069, respectively. 73% (97%) of eyes were within 0.5 (1) D of target refraction. No eyes lost CDVA, 43% (13 eyes) gained one line and 7% (two eyes) gained two lines. Mean corneal back curvature (KMB) and posterior central elevation (PCE) did not change significantly comparing preoperative and 6 months postoperative data (p = 0.91 and 0.77, respectively). Comparing 1 day with 6 months postoperative data, central corneal thickness (CCT), mean corneal front curvature (KMF), KMB and PCE did not change significantly (p = 0.27, 0.07, 0.52, 0.71, respectively). Total higher-order aberration (HOA), spherical aberration and coma increased significantly (p < 0.01) but trefoil remained stable (p = 0.49). Our results indicate that SMILE can correct myopia and myopic astigmatism of over -10 D predictably. No early ectasia was observed. Long-term changes in visual quality and corneal stability require further investigation. © 2017 Acta Ophthalmologica Scandinavica Foundation. Published by John Wiley & Sons Ltd.

Citicoline retards myopia progression following form deprivation in guinea pigs

PubMed Central

Liu, Shuangzhen; Fu, Chunyan

2016-01-01

The retinal dopaminergic system is involved in the myopic shift following form deprivation. Citicoline has been demonstrated to stimulate the dopaminergic system in the brain and retina. Furthermore, citicoline has been used in many neurogenic diseases, such as senile cognitive impairment, stroke and Parkinson's disease as well as in amblyopia and glaucoma. Our aim was to investigate the effect of citicoline on the refractive state and retinal dopamine level in form deprivation myopia of guinea pigs. Guinea pigs, at an age of four weeks, were randomly divided into normal control, deprivation, deprived + citicoline and deprived + vehicle groups. Form deprivation myopia was induced by a translucent eye shield covering the right eye. Citicoline was injected intraperitoneally twice a day (500 mg/kg, 9 am and 9 pm) for 10 days. In vitro, retinal explants were cultured with citicoline for 24 h, with a final citicoline concentration of 100 µmol/L. The ocular refractive parameters and retinal dopamine content were measured. After occlusion for 10 days, the form-deprived eyes became myopic with an increase in axial length and a decrease in retinal dopamine content. The intraperitoneal injection of citicoline reduced the myopic degree (from −3.25 ± 0.77D to −0.62 ± 0.47D, P < 0.001) and partially raised retinal dopamine levels (from 0.55 ± 0.21 ng to 0.81 ± 0.24 ng, P < 0.01) in the form-deprived eyes. After 24 h of culturing retinal explants with citicoline, retinal dopamine content increased significantly (from 0.42 ± 0.14 ng to 0.62 ± 0.21 ng, P < 0.05). These results demonstrated that an intraperitoneal injection of citicoline could retard the myopic shift induced by form deprivation in guinea pigs, which was mediated by an increase in the retinal dopamine levels. PMID:26979720

[Epidemiology of refractive errors].

PubMed

Wolfram, C

2017-07-01

Refractive errors are very common and can lead to severe pathological changes in the eye. This article analyzes the epidemiology of refractive errors in the general population in Germany and worldwide and describes common definitions for refractive errors and clinical characteristics for pathologicaal changes. Refractive errors differ between age groups due to refractive changes during the life time and also due to generation-specific factors. Current research about the etiology of refractive errors has strengthened the influence of environmental factors, which led to new strategies for the prevention of refractive pathologies.

Iris-fixated phakic intraocular lens implantation after retinal detachment surgery: long-term clinical results.

PubMed

Chung, Jin Kwon; Kim, Jin Kook; Lee, Jae Bum; Lee, Sung Jin

2013-10-01

To assess the efficacy and safety of iris-fixated phakic intraocular lens (pIOL) implantation to correct myopia in eyes with previous retinal detachment (RD) surgery. Department of Ophthalmology, Soonchunhyang University College of Medicine, Seoul, South Korea. Retrospective case series. Patients having pIOL implantation in both eyes were enrolled. Eyes that had scleral buckling or encircling (RD group) and healthy fellow eyes (non-RD group) were evaluated over a 6-year follow-up. The corrected distance visual acuity (CDVA), endothelial cell density (ECD), intraoperative complications, and long-term complications were safety outcomes. Uncorrected distance visual acuity (UDVA), predictability, and stability of refraction were efficacy outcomes. The study comprised 34 eyes (17 patients). The mean postoperative CDVA and ECD were not significantly different between groups, and no patient lost CDVA. The rate of transient intraocular pressure spike was significantly higher in the RD group (P=.043). After 3 years and 6 years, the mean postoperative UDVA was 0.06 logMAR ± 0.09 (SD) and 0.08 ± 0.10 logMAR, respectively, in the RD group and 0.04 ± 0.08 logMAR and 0.04 ± 0.09 logMAR, respectively, in the non-RD group (P=.518 and P=.478, respectively). The rate of eyes within ±0.50 diopter of the desired refraction and the postoperative refraction was not significantly different between groups. No eye had vitreoretinal changes requiring secondary surgical intervention. Iris-fixated pIOL implantation corrected the myopic refractive error in patients who had scleral buckling or encircling surgery for RD with a high degree of efficacy, safety, and long-term stability. No author has a financial or proprietary interest in any material or method mentioned. Copyright © 2013 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.

Comparison of DLK incidence after laser in situ keratomileusis associated with two femtosecond lasers: Femto LDV and IntraLase FS60

PubMed Central

Tomita, Minoru; Sotoyama, Yuko; Yukawa, Satoshi; Nakamura, Tadayuki

2013-01-01

Purpose To compare the incidence of diffuse lamellar keratitis (DLK) after laser in situ keratomileusis (LASIK) with flap creation using the Femto LDV and IntraLase™ FS60 femtosecond lasers.0 Methods A total of 818 consecutive myopic eyes had LASIK performed using either Femto LDV or IntraLase FS60 for flap creation. The same excimer laser, the Allegretto Wave® Eye-Q Laser, was used for correcting refractive errors for all patients. In the preoperative examination, uncorrected distance visual acuity, corrected distance visual acuity, and manifest refraction spherical equivalent were measured. At the postop examination, the same examinations were performed along with a slit-lamp biomicroscopic examination, and patients with DLK were classified into stages. For the statistical analysis of the DLK occurrence rate and the visual and refractive outcomes, the Mann-Whitney’s U-test was used. Results In the Femto LDV group with 514 eyes, 42 (8.17%) had DLK. In the IntraLase FS60 group with 304 eyes, 114 (37.5%) had DLK. There was a statistically significant difference in the DLK incidence rate between these groups (P < 0.0001). Both groups had excellent visual and refractive outcomes. Although low levels of DLK were observed for both groups, they did not affect visual acuity. Conclusion While there were significantly fewer incidences of low level DLK when using Femto LDV, neither femtosecond laser induced high levels of DLK, and any postoperative DLK cleared up within 1 week. Therefore, both lasers provide excellent results, with no clinical differences, and both excel at flap creation for LASIK. PMID:23874077

Comparison of single-step reverse transepithelial all-surface laser ablation (ASLA) to alcohol-assisted photorefractive keratectomy.

PubMed

Aslanides, Ioannis M; Padroni, Sara; Arba Mosquera, Samuel; Ioannides, Antonis; Mukherjee, Achyut

2012-01-01

To evaluate postoperative pain, corneal epithelial healing, development of corneal haze, refractive outcomes, and corneal aberrations in a novel one-step, modified transepithelial photorefractive keratectomy (PRK), termed All-surface laser ablation (ASLA), compared to conventional, alcohol-assisted PRK. Sixty eyes of 30 myopic patients were prospectively recruited to a randomized fellow eye study. Patients underwent conventional alcohol-assisted PRK in one eye (control group) and ASLA-modified transepithelial PRK in the other (30 eyes in each treatment arm). Primary endpoints were postoperative pain and haze scores at 1 day, 3 days, 1 week, and 1, 3, 6, and 12 months. Secondary endpoints included visual acuity at 1, 3, 6, and 12 months, corneal aberrations at 3, 6, and 12 months, and early and late onset haze. Refractive predictability, safety, and efficacy of the two methods were considered. The average age of the cohort was 29 years (standard deviation [SD]: 9; range: 18-46), and the average spherical equivalent refractive error was -4.18 diopters (SD: 1.9). At 3 days after surgery, the average pain score was 64% lower in the ASLA group (P < 0.0005). At this point, 96% of ASLA eyes had no epithelial defect, whereas 43% in the alcohol-assisted group did not achieve complete epithelial healing, and required replacement of bandage contact lens. The haze level was consistently lower in the ASLA group at all time points from 1 to 6 months. This study shows that the ASLA technique may have a future role in refractive surgery, due to the fact that it offers faster epithelial healing, lower pain scores, and significantly less haze formation.

Comparison of single-step reverse transepithelial all-surface laser ablation (ASLA) to alcohol-assisted photorefractive keratectomy

PubMed Central

Aslanides, Ioannis M; Padroni, Sara; Mosquera, Samuel Arba; Ioannides, Antonis; Mukherjee, Achyut

2012-01-01

Purpose To evaluate postoperative pain, corneal epithelial healing, development of corneal haze, refractive outcomes, and corneal aberrations in a novel one-step, modified transepithelial photorefractive keratectomy (PRK), termed All-surface laser ablation (ASLA), compared to conventional, alcohol-assisted PRK. Materials and methods Sixty eyes of 30 myopic patients were prospectively recruited to a randomized fellow eye study. Patients underwent conventional alcohol-assisted PRK in one eye (control group) and ASLA-modified transepithelial PRK in the other (30 eyes in each treatment arm). Primary endpoints were postoperative pain and haze scores at 1 day, 3 days, 1 week, and 1, 3, 6, and 12 months. Secondary endpoints included visual acuity at 1, 3, 6, and 12 months, corneal aberrations at 3, 6, and 12 months, and early and late onset haze. Refractive predictability, safety, and efficacy of the two methods were considered. Results The average age of the cohort was 29 years (standard deviation [SD]: 9; range: 18–46), and the average spherical equivalent refractive error was −4.18 diopters (SD: 1.9). At 3 days after surgery, the average pain score was 64% lower in the ASLA group (P < 0.0005). At this point, 96% of ASLA eyes had no epithelial defect, whereas 43% in the alcohol-assisted group did not achieve complete epithelial healing, and required replacement of bandage contact lens. The haze level was consistently lower in the ASLA group at all time points from 1 to 6 months. Conclusion This study shows that the ASLA technique may have a future role in refractive surgery, due to the fact that it offers faster epithelial healing, lower pain scores, and significantly less haze formation. PMID:22815640

Significant Axial Elongation with Minimal Change in Refraction in 3- to 6-Year-Old Chinese Preschoolers: The Shenzhen Kindergarten Eye Study.

PubMed

Guo, Xinxing; Fu, Min; Ding, Xiaohu; Morgan, Ian G; Zeng, Yangfa; He, Mingguang

2017-12-01

To document the distribution of ocular biometry and to evaluate its associations with refraction in a group of Chinese preschoolers. Population-based cross-sectional study. A total of 1133 preschoolers 3 to 6 years of age from 8 representative kindergartens. Biometric measurements including axial length (AL), anterior chamber depth (ACD), and corneal radius of curvature (CR) were obtained from partial-coherence laser interferometry (IOL Master; Carl Zeiss Meditec, Oberkochen, Germany) before cycloplegia. Lens power (LP) and AL-to-CR ratio were calculated. Cycloplegic refraction (3 drops of 1% cyclopentolate) was measured using an autorefractor (KR8800; Topcon Corp., Tokyo, Japan), and spherical equivalent refraction (SER) was calculated. Biometric and refractive parameters were assessed as a function of age and gender. Multiple regression analysis was performed to explore the associations between refraction and ocular biometry. Ocular biometric distributions and their relationships to refraction. Among the 1127 children (99.5%) with successful cycloplegic refraction, mean SER was 1.37±0.63 diopters (D). Prevalence of myopia increased from 0% at 3 years of age to 3.7% (95% confidence interval, 1.0%-6.5%) at 6 years of age. Biometric parameters followed Gaussian distributions with means of 22.39±0.68 mm for AL, 7.79±0.25 mm for CR, and 24.61±1.42 D for calculated LP; and non-Gaussian distributions with means of 3.34±0.24 mm for ACD and 2.88±0.06 for AL-to-CR ratio. Axial length, ACD, and AL-to-CR ratio increased from 3 to 6 years of age, CR remained stable, whereas LP declined. Overall, SER declined slightly. For the SER variance, AL explained 18.6% and AL-to-CR ratio explained 39.8%, whereas AL, CR, and LP accounted for 80.0% after adjusting for age and gender. Young Chinese children are predominantly mildly hyperopic, with a low prevalence of myopia by the age of 6 years. An increase of 1 mm in AL was associated with only 0.45 D of myopic change. Decreases in LP reduce the myopic shifts that normally would be associated with increases in AL, and thus play a key role in refractive development in this age group. Copyright © 2017 American Academy of Ophthalmology. Published by Elsevier Inc. All rights reserved.

Comparison of refractive development and retinal dopamine in OFF pathway mutant and C57BL/6J wild-type mice

PubMed Central

Chakraborty, Ranjay; Park, Han na; Aung, Moe H.; Tan, Christopher C.; Sidhu, Curran S.; Iuvone, P. Michael

2014-01-01

Purpose Proper visual transmission depends on the retinal ON and OFF pathways. We used Vsx1−/− mice with a retinal OFF visual pathway defect to determine the role of OFF pathway signaling in refractive development (RD) of the eye. Methods Refractive development was measured every 2 weeks in Vsx1−/−, Vsx1+/+ (both on 129S1/Sv background), and commonly used C57BL/6J mice from 4 to 12 weeks of age. Form deprivation (FD) was induced monocularly from 4 weeks of age using head-mounted diffuser goggles. Refractive state, corneal curvature, and ocular biometry were obtained weekly using photorefraction, keratometry, and 1310 nm spectral-domain optical coherence tomography. Retinal dopamine and its metabolite, 3,4-dihydroxyphenylacetate (DOPAC), were measured using high-performance liquid chromatography (HPLC). Results During normal development, the Vsx1−/− and Vsx1+/+ mice showed similar myopic refractions at younger ages (4 weeks, Vsx1−/−: −5.28±0.75 diopter (D); WT: −4.73±0.98 D) and became significantly hyperopic by 12 weeks of age (Vsx1−/−: 3.28±0.82 D; WT: 5.33±0.81 D). However, the C57BL/6J mice were relatively hyperopic at younger ages (mean refraction at 4 weeks, 3.40±0.43 D), and developed more hyperopic refractions until about 7 weeks of age (8.07±0.55 D) before stabilizing. Eight weeks of FD did not induce a myopic shift in the 129S1/Sv animals (0.16±0.85 D), as opposed to a significant shift of −4.29±0.42 D in the C57BL/6J mice. At 4 weeks of visual development, dopamine turnover (the DOPAC/dopamine ratio) was significantly greater in the 129S1/Sv mice compared to the C57BL/6J mice. FD did not alter the levels of dopamine between the goggled and opposite eyes for any genotype or strain. Conclusions OFF pathway signaling may not be critically important for normal refractive development in mice. Elevated retinal dopamine turnover in early refractive development may prevent FD myopia in 129S1/Sv mice compared to C57BL/6J mice. PMID:25352740

Types of Lamp for Homework and Myopia among Chinese School-Aged Children.

PubMed

Pan, Chen-Wei; Wu, Rong-Kun; Liu, Hu; Li, Jun; Zhong, Hua

2018-06-01

We aim to determine the association of the types of lamp for homework including incandescent lamp, fluorescent lamp, and light-emitting diode (LED) lamp with the prevalence of myopia in Chinese children. 2346 grade 7 students from ten middle schools (93.5% response rate) aged 13 to 14 years in Mojiang, a small county located in Southwestern China, participated in the study. Refractive error was measured with cycloplegia using an autorefractor by optometrists or trained technicians. An IOL Master was used to measure ocular biometric parameters including axial length (AL). Information regarding the types of lamp for homework af``ter schools was collected by questionnaires. Of all the study participants, 693 (29.5%) were affected by myopia, with the prevalence estimates being higher in girls (36.8%; 95% confidence interval [CI]: 34.0, 39.6) than in boys (22.8%; 95% CI: 20.4, 25.1) (P < 0.001). After adjusting for potential confounders such as gender, height, parental history of myopia, time on computer use, time on watching TV, time outdoors, and time on reading and writing, participants using LED lamps for homework had a more myopic refractive error and a longer AL compared with those using incandescent or fluorescent lamps. There were no significant differences in myopia prevalence between children using incandescent and fluorescent lamps for homework. The population attributable risk percentage for myopia associated with using LED lamps for homework after schools was 11.2%. Using LED lamps for homework after schools might contribute to the development of myopia among school-aged children.

Early outcomes after small incision lenticule extraction and photorefractive keratectomy for correction of high myopia

PubMed Central

Chan, Tommy C. Y.; Yu, Marco C. Y.; Ng, Alex; Wang, Zheng; Cheng, George P. M.; Jhanji, Vishal

2016-01-01

We prospectively compared visual and refractive outcomes in patients with high myopia and myopic astigmatism after small-incision lenticule extraction (SMILE) and photorefractive keratetctomy (PRK) with mitomycin C. Sixty-six eyes of 33 patients (mean age, 29.7 ± 5.6 years) were included (SMILE: 34 eyes, PRK 32 eyes). Preoperatively, no significant difference was noted in manifest spherical equivalent (p = 0.326), manifest sphere (p = 0.277), and manifest cylinder (p = 0.625) between both groups. At 1 month, there were significant differences in logMAR uncorrected distance visual acuity, efficacy index and manifest refraction spherical equivalent between SMILE and PRK (p ≤ 0.029). At 6 months, the logMAR corrected distance visual acuity (p = 0.594), logMAR uncorrected visual acuity (p = 0.452), efficacy index (p = 0.215) and safety index was (p = 0.537) was comparable between SMILE and PRK. Significant differences were observed in postoperative manifest spherical equivalent (p = 0.044) and manifest cylinder (p = 0.014) between both groups. At the end of 6 months, 100% of the eyes in SMILE group and 69% of the eyes in PRK group were within ±0.50 D of the attempted cylindrical correction. The postoperative difference vector, magnitude of error and absolute angle of error were significantly smaller after SMILE compared to PRK (p ≤ 0.040) implying a trend towards overcorrection of cylindrical correction following PRK. PMID:27601090

Clinical Outcomes of Small Incision Lenticule Extraction with Accelerated Cross-Linking (ReLEx SMILE Xtra) in Patients with Thin Corneas and Borderline Topography

PubMed Central

Ganesh, Sri; Brar, Sheetal

2015-01-01

Purpose. To study the safety and clinical outcomes of ReLEx SMILE with accelerated cross-linking in individuals with thinner corneas, borderline topography, and higher refractive errors. Methods. Eligible patients first underwent SMILE procedure for correction of myopic refractive error. Following the removal of lenticule, 0.25% riboflavin in saline was injected into the interface and allowed to diffuse for 60 seconds. Finally, eye was exposed to UV-A radiation of 45 mW/cm2 for 75 seconds through the cap. Total energy delivered was 3.4 J/cm2. Results. 40 eyes of 20 patients with mean age of 26.75 ± 5.99 years were treated. Mean follow-up was 12 months ± 28.12 days. Mean spherical equivalent (SE) was −5.02 ± 2.06 D preoperatively and −0.24 ± 0.18 D postoperatively. The mean central corneal thickness (CCT) and keratometry changed from 501 ± 25.90 µm to 415 ± 42.26 µm and 45.40 ± 1.40 D to 41.2 ± 2.75 D, respectively. Mean uncorrected visual acuity (UCVA) was 20/25 or better in all eyes. No eyes lost lines of corrected distant visual acuity (CDVA). There were no complications like haze, keratitis, ectasia, or regression. Conclusion. Based on the initial clinical outcome it appears that SMILE Xtra may be a safe and feasible modality to prevent corneal ectasia in susceptible individuals. PMID:26221538

Clinical Outcomes of Small Incision Lenticule Extraction with Accelerated Cross-Linking (ReLEx SMILE Xtra) in Patients with Thin Corneas and Borderline Topography.

PubMed

Ganesh, Sri; Brar, Sheetal

2015-01-01

Purpose. To study the safety and clinical outcomes of ReLEx SMILE with accelerated cross-linking in individuals with thinner corneas, borderline topography, and higher refractive errors. Methods. Eligible patients first underwent SMILE procedure for correction of myopic refractive error. Following the removal of lenticule, 0.25% riboflavin in saline was injected into the interface and allowed to diffuse for 60 seconds. Finally, eye was exposed to UV-A radiation of 45 mW/cm(2) for 75 seconds through the cap. Total energy delivered was 3.4 J/cm(2). Results. 40 eyes of 20 patients with mean age of 26.75 ± 5.99 years were treated. Mean follow-up was 12 months ± 28.12 days. Mean spherical equivalent (SE) was -5.02 ± 2.06 D preoperatively and -0.24 ± 0.18 D postoperatively. The mean central corneal thickness (CCT) and keratometry changed from 501 ± 25.90 µm to 415 ± 42.26 µm and 45.40 ± 1.40 D to 41.2 ± 2.75 D, respectively. Mean uncorrected visual acuity (UCVA) was 20/25 or better in all eyes. No eyes lost lines of corrected distant visual acuity (CDVA). There were no complications like haze, keratitis, ectasia, or regression. Conclusion. Based on the initial clinical outcome it appears that SMILE Xtra may be a safe and feasible modality to prevent corneal ectasia in susceptible individuals.

The opportunistic screening of refractive errors in school-going children by pediatrician using enhanced Brückner test

PubMed Central

Jain, Piyush; Kothari, Mihir T; Gode, Vaibhav

2016-01-01

Aim: The aim of this study was to compare the results of enhanced Brückner test (EBT) performed by a pediatrician and an experienced pediatric ophthalmologist. Subjects and Methods: In this prospective double-masked cohort study, a pediatrician and a pediatric ophthalmologist performed the EBT in a classroom of a school in semi-dark lighting condition using a direct ophthalmoscope. The results of the test were compared using 2 × 2 Bayesian table and kappa statistics. The findings of the pediatric ophthalmologists were considered gold standard. Results: Two hundred and thirty-six eyes of 118 subjects, mean age 6.8 ± 0.5 years (range, 5.4–7.8 years), were examined. The time taken to complete this test was <10 s per subject. The ophthalmologist identified 59 eyes as ametropic (12 hyperopic and 47 myopic eyes) and 177 as emmetropic compared to 61 eyes as ametropic and 175 emmetropic by pediatrician. The prevalence of the test positive was 25.9%. The sensitivity of the pediatrician was 90.2%, specificity was 97.7%, predictive value of the positive test was 93.2%, and predictive value of the negative test was 96.6%. The clinical agreement (kappa) between the pediatric ophthalmologist and the pediatrician was 0.9. Conclusion: The results of the EBT performed by pediatrician were comparable to that of an experienced pediatric ophthalmologist. Opportunistic screening of refractive errors using EBT by a pediatrician can be an important approach in the detection of ametropia in children. PMID:27905334

Effects of Progressive Addition Lens Wear on Digital Work in Pre-presbyopes

PubMed Central

Kee, Chea-su; Leung, Tsz Wing; Kan, Ka-hung; Lam, Christie Hang-I

2018-01-01

SIGNIFICANCE Growing popularity of handheld digital devices imposes significant challenges to our visual system and clinical management. This study aimed to determine the effects of lens design on parameters that may influence the refractive management of pre-presbyopic adult computer users. PURPOSE To determine the effects of wearing conventional single-vision lenses (SVL) versus progressive addition lenses (PAL) on the working distance and refractive status. METHODS Adult computer users, recruited from two age cohorts (18 to 25 years, n = 19; 30 to 40 years, n = 45), were prescribed SVLs and PALs designed for use with handheld digital devices. For each lens type, the working distance and refractive shift (post-task − pre-task) were measured immediately after lens delivery (T0) and after 1 month of lens wear (T1). Working distances were recorded with an automatic ultrasound device while the participants were playing a video game. Refractive status through the subjects' glasses was measured before (pre-task) and after playing the game (post-task). Questionnaires assessing the frequencies of 10 digital work–related visual symptoms were conducted for both lens types at T1. RESULTS Switching from SVL to PAL increased the working distance in both cohorts (mean ± SEM = 1.88 ± 0.60 cm; P = .002) and induced a small but significant positive refractive shift (+0.08 ± 0.04 D, P = .021) in the older cohort at T1. In the younger cohort, the changes in working distance due to the switching lens design were correlated with myopic error (r = +0.66, P = .002). In the older cohort, the changes in refractive shift due to switching lens design were correlated with amplitude of accommodation at both time points (r for T0 and T1 = −0.32 and −0.30, respectively; both P < .05). Progressive addition lens was rated as causing less “increased sensitivity to light” compared with SVL. CONCLUSIONS Switching from SVL to PAL increased the working distance and induced a positive refractive shift in the majority of pre-presbyopic adults. PMID:29683984

Children's refractions and visual activities in the school year and summer.

PubMed

Deng, Li; Gwiazda, Jane; Thorn, Frank

2010-06-01

To investigate the association of children's refractive errors with their visual activities assessed by questionnaire in the school year and summer break (June, July, and August). The parents of 147 children aged 6 to 18 years participating in a longitudinal study of refraction and visual function filled out a questionnaire in 1999 listing the number of weekly hours outside of school that the children read for pleasure, studied, watched TV, used the computer/played video games, and engaged in sports/outdoor activities. They also provided hours for these activities during the summer break. Refractions were measured annually by non-cycloplegic distance retinoscopy. Myopes refer to subjects who were myopic (spherical equivalent < -0.5 diopter) at the time of the survey and non-myopes (spherical equivalent refraction > or = -0.5 diopter) were emmetropic or in a few cases hyperopic at survey time. During the school year, myopes spent significantly fewer hours (8.25 +/- 6.24 h/week) than non-myopes (10.95 +/- 5.95 h/week) in sports/outdoor activity (p < 0.05). In addition, myopes (12.78 +/- 9.28 h/week) watched more television than non-myopes (8.91 +/- 5.95 h/week) (p = 0.02). No significant refractive group differences were found for other activities. During the summer break, no significant differences were found between refractive groups in any visual activity times. No significant correlations between sports/outdoor activity and TV time were found. Overall, the biggest differences between summer and school activity times were found in outdoor activity (21.76 +/- 13.80 vs.10.34 +/- 6.10 h/week; p < 0.001) and studying (1.69 +/- 3.71 vs. 9.51 +/- 6.96 h/week; p < 0.001). In agreement with other studies, the non-myopes had more hours of sports/outdoor activity during the school year, which may protect against myopia development. A new finding is the high number of sports/outdoor activity hours for both myopes and non-myopes during the summer break, which may contribute to slowed eye growth in all children during these 3 months.

Associations of reading posture, gaze angle and reading distance with myopia and myopic progression.

PubMed

Pärssinen, Olavi; Kauppinen, Markku

2016-12-01

To study the associations of habitual reading posture, gaze angle in reading and reading distance with myopia and changes in myopia among myopic children. A total of 240 myopic schoolchildren (mean age 10.9 years), with no previous spectacles, were recruited during 1983-1984 to a randomized 3-year clinical trial of bifocal treatment of myopia. Three annual examinations with subjective cycloplegic refraction were conducted for 237-238 subjects. A further examination was conducted at the mean age of 23.2 years for 178 subjects. Habitual reading posture was elicited by questionnaire at study outset. Reading distance was measured with a Clement Clark accommodometer and gaze angle with an angle scale at baseline and all three annual follow-ups. Height was measured by a school nurse. The connections between the variables were studied with the standard statistical methods. Higher myopia was connected with shorter reading distance among girls at follow-ups 2 and 3, but not at the other examinations. The correlation of spherical equivalent with height was non-significant at each follow-up. Myopic progression across the whole follow-up was highest among those who read sitting down at baseline (-3.58 ± 1.75 D) and lowest among those who read face up lying down (-2.35 ± 1.53 D) (p = 0.021). Reading with eyes at a more downward angle was slightly connected with greater myopic progression (r = -0.166, p = 0.028). Reading in a sitting posture at myopia onset predicted the greatest myopic progression to adulthood and reading face up on one's back the lowest. Reading with eyes on turned more downwards was slightly connected with greater myopic progression. © 2016 Acta Ophthalmologica Scandinavica Foundation. Published by John Wiley & Sons Ltd.

Small incision corneal refractive surgery using the small incision lenticule extraction (SMILE) procedure for the correction of myopia and myopic astigmatism: results of a 6 month prospective study.

PubMed

Sekundo, Walter; Kunert, Kathleen S; Blum, Marcus

2011-03-01

This 6 month prospective multi-centre study evaluated the feasibility of performing myopic femtosecond lenticule extraction (FLEx) through a small incision using the small incision lenticule extraction (SMILE) procedure. Prospective, non-randomised clinical trial. PARTICIPANTS; Ninety-one eyes of 48 patients with myopia with and without astigmatism completed the final 6 month follow-up. The patients' mean age was 35.3 years. Their preoperative mean spherical equivalent (SE) was −4.75±1.56 D. A refractive lenticule of intrastromal corneal tissue was cut utilising a prototype of the Carl Zeiss Meditec AG VisuMax femtosecond laser system. Simultaneously two opposite small ‘pocket’ incisions were created by the laser system. Thereafter, the lenticule was manually dissected with a spatula and removed through one of incisions using modified McPherson forceps. Uncorrected visual acuity (UCVA) and best spectacle corrected visual acuity (BSCVA) after 6 months, objective and manifest refraction as well as slit-lamp examination, side effects and a questionnaire. Six months postoperatively the mean SE was −0.01 D±0.49 D. Most treated eyes (95.6%) were within ±1.0 D, and 80.2% were within ±0.5 D of intended correction. Of the eyes treated, 83.5% had an UCVA of 1.0 (20/20) or better, 53% remained unchanged, 32.3% gained one line, 3.3% gained two lines of BSCVA, 8.8% lost one line and 1.1% lost ≥2 lines of BSCVA. When answering a standardised questionnaire, 93.3% of patients were satisfied with the results obtained and would undergo the procedure again. SMILE is a promising new flapless minimally invasive refractive procedure to correct myopia.

Headaches associated with refractive errors: myth or reality?

PubMed

Gil-Gouveia, R; Martins, I P

2002-04-01

Headache and refractive errors are very common conditions in the general population, and those with headache often attribute their pain to a visual problem. The International Headache Society (IHS) criteria for the classification of headache includes an entity of headache associated with refractive errors (HARE), but indicates that its importance is widely overestimated. To compare overall headache frequency and HARE frequency in healthy subjects with uncorrected or miscorrected refractive errors and a control group. We interviewed 105 individuals with uncorrected refractive errors and a control group of 71 subjects (with properly corrected or without refractive errors) regarding their headache history. We compared the occurrence of headache and its diagnosis in both groups and assessed its relation to their habits of visual effort and type of refractive errors. Headache frequency was similar in both subjects and controls. Headache associated with refractive errors was the only headache type significantly more common in subjects with refractive errors than in controls (6.7% versus 0%). It was associated with hyperopia and was unrelated to visual effort or to the severity of visual error. With adequate correction, 72.5% of the subjects with headache and refractive error reported improvement in their headaches, and 38% had complete remission of headache. Regardless of the type of headache present, headache frequency was significantly reduced in these subjects (t = 2.34, P =.02). Headache associated with refractive errors was rarely identified in individuals with refractive errors. In those with chronic headache, proper correction of refractive errors significantly improved headache complaints and did so primarily by decreasing the frequency of headache episodes.

Patterns in longitudinal growth of refraction in Southern Chinese children: cluster and principal component analysis.

PubMed

Chen, Yanxian; Chang, Billy Heung Wing; Ding, Xiaohu; He, Mingguang

2016-11-22

In the present study we attempt to use hypothesis-independent analysis in investigating the patterns in refraction growth in Chinese children, and to explore the possible risk factors affecting the different components of progression, as defined by Principal Component Analysis (PCA). A total of 637 first-born twins in Guangzhou Twin Eye Study with 6-year annual visits (baseline age 7-15 years) were available in the analysis. Cluster 1 to 3 were classified after a partitioning clustering, representing stable, slow and fast progressing groups of refraction respectively. Baseline age and refraction, paternal refraction, maternal refraction and proportion of two myopic parents showed significant differences across the three groups. Three major components of progression were extracted using PCA: "Average refraction", "Acceleration" and the combination of "Myopia stabilization" and "Late onset of refraction progress". In regression models, younger children with more severe myopia were associated with larger "Acceleration". The risk factors of "Acceleration" included change of height and weight, near work, and parental myopia, while female gender, change of height and weight were associated with "Stabilization", and increased outdoor time was related to "Late onset of refraction progress". We therefore concluded that genetic and environmental risk factors have different impacts on patterns of refraction progression.

Phakic intraocular lenses for the treatment of refractive errors: an evidence-based analysis.

PubMed

2009-01-01

The objective of this analysis is to review the effectiveness, safety, and cost-effectiveness of phakic intraocular lenses (pIOLs) for the treatment of myopia, hyperopia, and astigmatism. CONDITION AND TARGET POPULATION REFRACTIVE ERRORS: Refractive errors occur when the eye cannot focus light properly. In myopia (near- or short-sightedness), distant objects appear blurry because the axis of the eye is too long or the cornea is too steep, so light becomes focused in front of the retina. Hyperopia (far sightedness) occurs when light is focused behind the retina causing nearby objects to appear blurry. In astigmatism, blurred or distorted vision occurs when light is focused at two points rather than one due to an irregularly shaped cornea or lens. Refractive errors are common worldwide, but high refractive errors are less common. In the United States, the prevalence of high myopia (≤ -5 D) in people aged 20 to 39, 40 to 59, and 60 years and older is 7.4% (95% confidence interval [CI], 6.5% - 8.3%), 7.8% (95% CI, 6.4% - 8.6%), and 3.1% (95% CI, 2.2% - 3.9%), respectively. The prevalence of high hyperopia (≥ 3 D) is 1.0% (95% CI, .6% - 1.4%), 2.4% (95% CI, 1.7% - 3.0%), and 10.0% (95% CI, 9.1% - 10.9%) for the same age groupings. Finally, the prevalence of astigmatism (≥ 1 D cylinder) is 23.1% (95% CI, 21.6% - 24.5%), 27.6% (95% CI, 25.8% - 29.3%) and 50.1% (48.2% - 52.0%). LOW VISION: According to the Ontario Schedule of Benefits, low visual acuity is defined by a best spectacle corrected visual acuity (BSCVA) of 20/50 (6/15) or less in the better eye and not amenable to further medical and/or surgical treatment. Similarly, the Ontario Assistive Devices Program defines low vision as BSCVA in the better eye in the range of 20/70 or less that cannot be corrected medically, surgically, or with ordinary eyeglasses or contact lenses. Estimates of the prevalence of low vision vary. Using the criteria of BSCVA ranging from 20/70 to 20/160, one study estimated that 35.6 per 10,000 people in Canada have low vision. The 2001 Participation and Activity Limitation Survey (PALS) found that 594,350 (2.5%) Canadians had "difficulty seeing ordinary newsprint or clearly seeing the face of someone from 4 m," and the Canadian National Institute for the Blind (CNIB) registry classified 105,000 (.35%) Canadians as visually disabled. PHAKIC INTRAOCULAR LENSES (PIOL): A phakic intraocular lens (pIOL) is a supplementary lens that is inserted into the anterior or posterior chamber of the eye to correct refractive errors (myopia, hyperopia, and astigmatism). Unlike in cataract surgery, the eye's natural crystalline lens is not removed when the pIOL is inserted, so the eye retains its accommodative ability. In Canada and the United States, iris-fixated (anterior chamber lenses that are anchored to the iris with a claw) and posterior chamber lenses are the only types of pIOLs that are licensed by Health Canada and the Food and Drug Administration, respectively. EVIDENCE-BASED ANALYSIS METHOD: RESEARCH QUESTIONS #ENTITYSTARTX00026; What are the effectiveness, cost-effectiveness, and safety of pIOLs for the treatment of myopia, hyperopia, and astigmatism?Do certain subgroups (e.g. high myopia and low vision) benefit more from pIOLs?How do pIOLs compare with alternative surgical treatment options (LASIK, PRK, and CLE)?Using appropriate keywords, a literature search was conducted up to January 2009. Systematic reviews, meta-analyses, randomized controlled trials, and observational studies with more than 20 eyes receiving pIOLs were eligible for inclusion. The primary outcomes of interest were uncorrected visual acuity (UCVA), predictability of manifest refraction spherical equivalent (MRSE), and adverse events. The GRADE approach was used to systematically and explicitly evaluate the quality of evidence. The search identified 1,131 citations published between January 1, 2003, and January 16, 2009. Including a health technology assessment (HTA) identified in the bibliography review, 30 studies met the inclusion criteria: two HTAs; one systematic review; 20 pre-post observational studies; and seven comparative studies (five pIOL vs. LASIK, one pIOL vs. PRK, and one pIOL vs. CLE). Both HTAs concluded that there was good evidence of the short-term efficacy and safety of pIOLs, however, their conclusions regarding long-term safety differed. The 2006 HTA found convincing evidence of long-term safety, while the 2009 HTA found no long-term evidence about the risks of complications including cataract development, corneal damage, and retinal detachment. The systematic review of adverse events found that cataract development (incidence rate of 9.6% of eyes) is a substantial risk following posterior chamber pIOL implantation, while chronic endothelial cell loss is a safety concern after iris-fixated pIOL implantation. Adverse event rates varied by lens type, but they were more common in eyes that received posterior chamber pIOLs. The evidence of pIOL effectiveness is based on pre-post case series. These studies reported a variety of outcomes and different follow-up time points. It was difficult to combine the data into meaningful summary measures as many time points are based on a single study with a very small sample size. Overall, the efficacy evidence is low to very low quality based on the GRADE Working Group Criteria. For all refractive errors (low to high), most eyes experienced a substantial increase in uncorrected visual acuity (UCVA) with more than 75% of eyes achieving UCVA of 20/40 or better at all postoperative time points. The proportion of eyes that achieved postoperative UCVA 20/20 or better varied substantially according type of lens used and the type of refractive error being corrected, ranging from about 30% of eyes that received iris-fixated lenses for myopia to more than 78% of eyes that received posterior chamber toric lenses for myopic astigmatism. Predictability of manifest refraction spherical equivalent (MRSE) within ± 2.0 D was very high (≥ 90%) for all types of lenses and refractive error. At most time points, more than 50% of eyes achieved a MRSE within ± 0.5 D of emmetropia and at least 85% within ± 1.0 D. Predictability was lower for eyes with more severe preoperative refractive errors. The mean postoperative MRSE was less than 1.0 D in all but two studies. Safety, defined as a loss of two or more Snellen lines of best spectacle corrected visual acuity (BSCVA), was high for all refractive errors and lens types. Losses of two or more lines of BSCVA were uncommon, occurring in fewer than 2% of eyes that had received posterior chamber pIOLs for myopia, and less than 1% of eyes that received iris-fixated lens implantation for myopia. Most eyes did not experience a clinically significant change in BSCVA (i.e. loss of one line, no change, or gain of one line), but 10% to 20% of eyes gained two or more lines of BSCVA. The pIOL outcomes for UCVA, predictability, BSCVA, and adverse events were compared with FDA targets and safety values for refractive surgery and found to meet or exceed these targets at most follow-up time points. The results were then stratified to examine the efficacy of pIOLs for high refractive errors. There was limited data for many outcomes and time points, but overall the results were similar to those for all levels of refractive error severity. The studies that compared pIOLs with LASIK, PRK, and CLE for patients with moderate to high myopia and myopic astigmatism showed that pIOLs performed better than these alternative surgical options for the outcomes of: UCVA,predictability and stability of MRSE,postoperative MRSE,safety (measured as clinically significant loss of BSCVA), andgains in BSCVA.Correction of refractive cylinder (astigmatism) was the only outcome that favoured refractive surgery over pIOLs. This was observed for both toric and non-toric pIOLs (toric pIOLs correct for astigmatism, non-toric pIOLs do not). Common adverse events in the LASIK groups were diffuse lamellar keratitis and striae in the corneal flap. In the pIOL groups, lens repositioning and lens opacities (both asymptomatic and visually significant cataracts) were the most commonly observed adverse events. These studies were determined to be of low to very low evidence quality based on the GRADE Working Group Criteria. Eye, myopia, hyperopia, astigmatism, phakic intraocular lens, LASIK, PRK, uncorrected visual acuity, best corrected visual acuity, refractive errors, clear lens extraction.

Change in the accommodative convergence per unit of accommodation ratio after bilateral laser in situ keratomileusis for myopia in orthotropic patients: prospective evaluation.

PubMed

Prakash, Gaurav; Choudhary, Vandana; Sharma, Namrata; Titiyal, Jeewan S

2007-12-01

To analyze the effect of bilateral laser in situ keratomileusis (LASIK) on the accommodative convergence per unit of accommodation (AC/A) ratio in otherwise normal orthotropic myopic patients. Cornea and refractive services of a tertiary-care ophthalmic center. This prospective clinical trial consisted of 61 myopic patients who had bilateral LASIK. Those with manifest tropia, previous squint surgery, amblyopia, or absent or impaired binocularity or those in whom monovision was planned were excluded. The preoperative examination included visual acuity, cycloplegic refraction, assessment of binocularity, a prism cover test, and evaluation of the stimulus AC/A ratio by the gradient method. All patients had LASIK using the Zyoptix platform (Bausch & Lomb). Postoperative evaluation included uncorrected and best corrected visual acuities, residual refraction, and the AC/A ratio. All patients had a follow-up of 9 months. There was significant decrease in the mean AC/A ratio at the 1-week and 1-month follow-ups. The AC/A progressively recovered to near preoperative values between 3 months and 9 months after surgery (analysis of variance test). There was a significant reduction in the number of symptomatic patients from the first month onward (chi square = 89.23; P<.001). The AC/A ratio varied after LASIK, stabilizing between 3 months and 9 months after surgery. This suggests that the maximum variation in the accommodation-convergence relationship after LASIK occurs in the first 3 months.

The distribution of refractive errors among children attending Lumbini Eye Institute, Nepal.

PubMed

Rai, S; Thapa, H B; Sharma, M K; Dhakhwa, K; Karki, R

2012-01-01

Uncorrected refractive error is an important cause of childhood blindness and visual impairment. To describe the patterns of refractive errors among children attending the outpatient clinic at the Department of Pediatric Ophthalmology, Lumbini Eye Institute, Bhairahawa, Nepal. Records of 133 children with refractive errors aged 5 - 15 years from both the urban and rural areas of Nepal and the adjacent territory of India attending the hospital between September and November 2010 were examined for patterns of refractive errors. The SPSS statistical software was used to perform data analysis. The commonest type of refractive error among the children was astigmatism (47 %) followed by myopia (34 %) and hyperopia (15 %). The refractive error was more prevalent among children of both the genders of age group 11-15 years as compared to their younger counterparts (RR = 1.22, 95 % CI = 0.66 - 2.25). The refractive error was more common (70 %) in the rural than the urban children (26 %). The rural females had a higher (38 %) prevalence of myopia than urban females (18 %). Among the children with refractive errors, only 57 % were using spectacles at the initial presentation. Astigmatism is the commonest type of refractive error among the children of age 5 - 15 years followed by hypermetropia and myopia. Refractive error remains uncorrected in a significant number of children. © NEPjOPH.

Risk factors for incident myopia in Australian schoolchildren: the Sydney adolescent vascular and eye study.

PubMed

French, Amanda N; Morgan, Ian G; Mitchell, Paul; Rose, Kathryn A

2013-10-01

To examine the risk factors for incident myopia in Australian schoolchildren. Population-based, longitudinal cohort study. The Sydney Adolescent Vascular and Eye Study (SAVES) was a 5- to 6-year follow-up of the Sydney Myopia Study (SMS). At follow-up, 2103 children were reexamined: 892 (50.5%) from the younger cohort and 1211 (51.5%) from the older cohort. Of these, 863 in the younger cohort and 1196 in the older cohort had complete refraction data. Cycloplegic autorefraction (cyclopentolate 1%; Canon RK-F1; Canon, Tokyo, Japan) was measured at baseline and follow-up. Myopia was defined as a spherical equivalent refraction of ≤-0.50 diopters (D). Children were classified as having incident myopia if they were nonmyopic at baseline and myopic in either eye at follow-up. A comprehensive questionnaire determined the amount of time children spent outdoors and doing near work per week at baseline, as well as ethnicity, parental myopia, and socioeconomic status. Incident myopia. Children who became myopic spent less time outdoors compared with children who remained nonmyopic (younger cohort, 16.3 vs. 21.0 hours, respectively, P<0.0001; older cohort, 17.2 vs. 19.6 hours, respectively, P=0.001). Children who became myopic performed significantly more near work (19.4 vs. 17.6 hours; P=0.02) in the younger cohort, but not in the older cohort (P=0.06). Children with 1 or 2 parents who were myopic had greater odds of incident myopia (1 parent: odds ratio [OR], 3.2, 95% confidence interval [CI], 1.9-5.2; both parents: OR, 3.3, 95% CI, 1.6-6.8) in the younger but not the older cohort. Children of East Asian ethnicity had a higher incidence of myopia compared with children of European Caucasian ethnicity (both P<0.0001) and spent less time outdoors (both P<0.0001). A less hyperopic refraction at baseline was the most significant predictor of incident myopia. The addition of time outdoors, near work, parental myopia, and ethnicity to the model significantly improved the predictive power (P<0.0001) in the younger cohort but had little effect in the older cohort. Time spent outdoors was negatively associated with incident myopia in both age cohorts. Near work and parental myopia were additional significant risk factors for myopia only in the younger cohort. The author(s) have no proprietary or commercial interest in any materials discussed in this article. Copyright © 2013 American Academy of Ophthalmology. Published by Elsevier Inc. All rights reserved.

[Character of refractive errors in population study performed by the Area Military Medical Commission in Lodz].

PubMed

Nowak, Michał S; Goś, Roman; Smigielski, Janusz

2008-01-01

To determine the prevalence of refractive errors in population. A retrospective review of medical examinations for entry to the military service from The Area Military Medical Commission in Lodz. Ophthalmic examinations were performed. We used statistic analysis to review the results. Statistic analysis revealed that refractive errors occurred in 21.68% of the population. The most commen refractive error was myopia. 1) The most commen ocular diseases are refractive errors, especially myopia (21.68% in total). 2) Refractive surgery and contact lenses should be allowed as the possible correction of refractive errors for military service.

Education-Related Parameters in High Myopia: Adults versus School Children.

PubMed

Jonas, Jost B; Xu, Liang; Wang, Ya Xing; Bi, Hong Sheng; Wu, Jian Feng; Jiang, Wen Jun; Nangia, Vinay; Sinha, Ajit; Zhu, Dan; Tao, Yong; Guo, Yin; You, Qi Sheng; Wu, Li Juan; Tao, Li Xin; Guo, Xiu Hua; Ohno-Matsui, Kyoko; Panda-Jonas, Songhomitra

2016-01-01

Since high myopia in the younger generation may differ etiologically from high myopia in older generations, we examined whether education-related parameters differ between high myopia in today´s school children and high pathological myopia in today´s elderly generation. The investigation included the adult populations of the population-based Beijing Eye Study (BES) (3468 adults;mean age:64.6±9.8years;range:50-93years) and Central India Eye and Medical Study (CIEMS) (4711 adults;age:49.±13.2years;range:30-100years), and the children and teenager populations of the Shandong Children Eye Study (SCES) (6026 children;age:9.7±3.3years;range:4-18years;cycloplegic refractometry), Gobi Desert Children Eye Study (1565;age:11.9±3.5years;range:6-21 years;cycloplegic refractometry), Beijing Pediatric Eye Study (681 children;age:7.7±1.6years;range:5-13 years;non-cycloplegic refractometry,calculation of axial length to corneal curvature radius ratio), Beijing Children Eye Study (15066 children;age:13.2±3.4years;range:7-18years;non-cycloplegic refractometry), Beijing High School Teenager Eye Study (4677 children;age:16.9±0.7years;range:16-18years;non-cycloplegic refractometry). In the BES and CIEMS, educational level did not differ significantly between, or was significantly lower in the highly myopic group (myopic refractive error ≥6 diopters) than in the non-highly myopic group. In all non-adult study populations, higher prevalence of high myopia was significantly associated with higher degree of education related parameters such as attendance of high-level schools, and more time spent for indoors near work versus time spent outdoors. Comparing associations of old or genetic high myopia in adults with new or acquired high myopia in school children revealed that education-related parameters did not show a clear association with old or genetic high myopia, while in contrast, new high myopia showed strong associations with education. It confirms previous studies that the two forms of high myopia not only differed in age of onset, but also in associations with education as well. The data support the notion of two types of high myopia. Future studies may assess whether the risk of pathologic myopic maculopathy and high myopia associated open-angle glaucoma differs between both types of high myopia.

On-line pachymetry outcome of ablation in aberration free mode TransPRK.

PubMed

Adib-Moghaddam, Soheil; Arba-Mosquera, Samuel; Salmanian, Bahram; Omidvari, Amir-Houshang; Noorizadeh, Farsad

2014-01-01

There are many independent factors that influence the outcome of refractive surgeries, consisting of patient characteristics and environmental factors. We studied the accuracy of central ablation depth compared to online pachymetry results. A total of 153 eyes that underwent TransPRK at Bina Eye Hospital, Tehran, Iran, were evaluated from November 2010 to January 2012 in a retrospective cross-sectional study. The relevant data were registered and bivariate correlations and linear regression association were investigated statistically. The mean age was 29 ± 5 years. Distribution of refractive errors was as follows: compound myopic astigmatism 123 (80.4%), simple myopia 24 (15.7%), and mixed astigmatism 6 (3.9%). Mean ambient temperature and humidity levels intraoperatively were 23.49 ± 1.16°C and 28.91 ± 6.16%, respectively. There was a significant difference (p<0.001) between the preassumed central ablation depth (131.68 ± 32.72 µm) and the net level of ablation depth (measured by online pachymetry, 168.04 ± 41.47 µm). Temperature and humidity levels were not in any statistically significant correlation with the net amount of difference found. The backward linear regression was done to reveal the association between ablation depth and several variables. This study showed that there is deviation in optical coherence pachymetry online measurements done with SCHWIND AMARIS laser. Ambient temperature and humidity levels intraoperatively do not influence the outcome. However, basic structural characteristics of patients along with change in refractive index and corneal shrinkage because of corneal dehydration are associated with the differences.

Patterns in longitudinal growth of refraction in Southern Chinese children: cluster and principal component analysis

PubMed Central

Chen, Yanxian; Chang, Billy Heung Wing; Ding, Xiaohu; He, Mingguang

2016-01-01

In the present study we attempt to use hypothesis-independent analysis in investigating the patterns in refraction growth in Chinese children, and to explore the possible risk factors affecting the different components of progression, as defined by Principal Component Analysis (PCA). A total of 637 first-born twins in Guangzhou Twin Eye Study with 6-year annual visits (baseline age 7–15 years) were available in the analysis. Cluster 1 to 3 were classified after a partitioning clustering, representing stable, slow and fast progressing groups of refraction respectively. Baseline age and refraction, paternal refraction, maternal refraction and proportion of two myopic parents showed significant differences across the three groups. Three major components of progression were extracted using PCA: “Average refraction”, “Acceleration” and the combination of “Myopia stabilization” and “Late onset of refraction progress”. In regression models, younger children with more severe myopia were associated with larger “Acceleration”. The risk factors of “Acceleration” included change of height and weight, near work, and parental myopia, while female gender, change of height and weight were associated with “Stabilization”, and increased outdoor time was related to “Late onset of refraction progress”. We therefore concluded that genetic and environmental risk factors have different impacts on patterns of refraction progression. PMID:27874105

Predictability of SMILE over four years in high myopes.

PubMed

Burazovitch, J; Naguzeswski, D; Beuste, T; Guillard, M

2017-06-01

To determine whether the visual outcomes of the refractive surgery technique small incision lenticule extraction (SMILE), are stable, effective, and predictable for high myopia over a four-year period. This is a retrospective study. The data were collected between March 2012 and July 2016. Two hundred and forty-eight patients participated in the study; that is, 496 eyes: 140 eyes of 70 patients (52 women/18 men) were classified into the highly myopic group (refraction measured in spherical equivalent (RMSE)>-6 D), and 356 eyes of 178 patients (98 women/80 men) into the control group (RMSE<-6 D). Follow-up tests were conducted immediately following the procedure (D+1), after three months, after one year, and after four years. Refraction, uncorrected visual acuity (UCVA), and best visual corrected acuity (BCVA) were measured. The highly myopic group (HMG) contained more women, and astigmatism was higher for this group than for the control group (CG). These were BCVA, refractive stability, the index of safety (SI: BCVA preoperatively D+1/BCVA postoperatively), and predictability (the percentage of eyes within±0.5 D of the target). In both groups, UCVA was better after the fourth year than it was immediately after the procedure (HMG: P=0.001; CG: P=0.001). Although it differed at one year (P=0.01), the groups' refractive stability tended to converge over four years (P=0.138). The groups' SI was found to be identical in the four follow-up tests (P=0.734 at D+1; P=0.07 at M+1; P=0.160 at M3 and Y1; and P=0.274 at Y4). For the HMG, SI stability was attained after three months (1.00±0.1); whereas it was attained after one month (0.91±0.11) for the CG. Four years after the surgery, we observed that 87% of the operated-upon eyes in the HMG were within 0.5 D of the target. SMILE is a good refractive surgery technique for treating high myopia. It yields stable, safe, effective, and predictable results over four years. Copyright © 2017 Elsevier Masson SAS. All rights reserved.

Refractive errors in Aminu Kano Teaching Hospital, Kano Nigeria.

PubMed

Lawan, Abdu; Eme, Okpo

2011-12-01

The aim of the study is to retrospectively determine the pattern of refractive errors seen in the eye clinic of Aminu Kano Teaching Hospital, Kano-Nigeria from January to December, 2008. The clinic refraction register was used to retrieve the case folders of all patients refracted during the review period. Information extracted includes patient's age, sex, and types of refractive error. All patients had basic eye examination (to rule out other causes of subnormal vision) including intra ocular pressure measurement and streak retinoscopy at two third meter working distance. The final subjective refraction correction given to the patients was used to categorise the type of refractive error. Refractive errors was observed in 1584 patients and accounted for 26.9% of clinic attendance. There were more females than males (M: F=1.0: 1.2). The common types of refractive errors are presbyopia in 644 patients (40%), various types of astigmatism in 527 patients (33%), myopia in 216 patients (14%), hypermetropia in 171 patients (11%) and aphakia in 26 patients (2%). Refractive errors are common causes of presentation in the eye clinic. Identification and correction of refractive errors should be an integral part of eye care delivery.

The Optic Nerve Head in Primary Open-Angle Glaucoma Eyes With High Myopia: Characteristics and Association With Visual Field Defects.

PubMed

Chen, Li-Wei; Lan, Yu-Wen; Hsieh, Jui-Wen

2016-06-01

To evaluate the morphologic characteristics of optic neuropathy and its association with visual field (VF) defects in primary open-angle glaucoma (POAG) eyes with high myopia. In this cross-sectional study, we reviewed data from 375 Taiwanese patients (375 eyes) of POAG, ages 20 to 60 years. Optic disc photographs were used for planimetric measurements of morphologic variables. The myopic refraction was divided into high myopia (<-6.0 D) and nonhigh myopia (moderate myopia to hyperopia). The optic disc area was classified as moderate (1.59 to 2.85 mm), large, and small. Differences in characteristics between groups, correlations with the disc area, and factors associated with VF defects were determined. Of the 142 highly myopic eyes, 33 (23%) had a large disc, 26 (18%) had a small disc, and 55 (39%) had a tilted disc. Large discs had a higher cup-to-disc (C/D) area ratio and a higher tilt ratio; small discs had a smaller rim area and a lower tilt ratio (all P<0.05). Characteristics associated with high myopia included a smaller rim area, a higher C/D area ratio, and a lower tilt ratio (all P<0.001). In logistic regression, the refraction, the C/D area ratio, the rim area, and the tilt ratio (all P<0.05) were associated with VF defects. In Taiwanese individuals with POAG, our study found that tilted, large, or small discs were prevalent in highly myopic eyes. Of these characteristics, only the disc tilt and high myopia by itself were associated with the severity of glaucomatous optic neuropathy.

Evaluation of iris recognition system for wavefront-guided laser in situ keratomileusis for myopic astigmatism.

PubMed

Ghosh, Sudipta; Couper, Terry A; Lamoureux, Ecosse; Jhanji, Vishal; Taylor, Hugh R; Vajpayee, Rasik B

2008-02-01

To evaluate the visual and refractive outcomes of wavefront-guided laser in situ keratomileusis (LASIK) using an iris recognition system for the correction of myopic astigmatism. Centre for Eye Research Australia, Melbourne Excimer Laser Research Group, and Royal Victorian Eye and Ear Hospital, East Melbourne, Victoria, Australia. A comparative analysis of wavefront-guided LASIK was performed with an iris recognition system (iris recognition group) and without iris recognition (control group). The main parameters were uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity, amount of residual cylinder, manifest spherical equivalent (SE), and the index of success using the Alpins method of astigmatism analysis 1 and 3 months postoperatively. A P value less than 0.05 was considered statistically significant. Preoperatively, the mean SE was -4.32 diopters (D) +/- 1.59 (SD) in the iris recognition group (100 eyes) and -4.55 +/- 1.87 D in the control group (98 eyes) (P = .84). At 3 months, the mean SE was -0.05 +/- 0.21 D and -0.20 +/- 0.40 D, respectively (P = .001), and an SE within +/-0.50 D of emmetropia was achieved in 92.0% and 85.7% of eyes, respectively (P = .07). At 3 months, the UCVA was 20/20 or better in 90.0% and 76.5% of eyes, respectively. A statistically significant difference in the amount of astigmatic correction was seen between the 2 groups (P = .00 and P = .01 at 1 and 3 months, respectively). The index of success was 98.0% in the iris recognition group and 81.6% in the control group (P = .03). Iris recognition software may achieve better visual and refractive outcomes in wavefront-guided LASIK for myopic astigmatism.

Two-years results of small-incision lenticule extraction and wavefront-guided laser in situ keratomileusis for Myopia.

PubMed

Kobashi, Hidenaga; Kamiya, Kazutaka; Igarashi, Akihito; Takahashi, Masahide; Shimizu, Kimiya

2018-03-01

To compare the 2-years visual and refractive outcomes between small-incision lenticule extraction (SMILE) and wavefront-guided laser in situ keratomileusis (LASIK) in eyes with myopia and myopic astigmatism. Our retrospective case-control study examined 30 eyes of 30 patients with the manifest refraction spherical equivalent (MRSE) of -3.71 ± 1.83 dioptres (D) who underwent SMILE and 30 eyes of 30 patients with MRSE of -3.81 ± 1.40 D who underwent wavefront-guided LASIK. We assessed the 2-years clinical outcomes. Logarithm of the minimal angle of resolution (LogMAR)-corrected distance visual acuity (CDVA) was -0.23 ± 0.07 in the SMILE group and -0.24 ± 0.07 in the wavefront-guided LASIK group 2 years postoperatively (p = 0.82). Logarithm of the minimal angle of resolution-uncorrected distance visual acuity (UDVA) was -0.18 ± 0.09 and -0.15 ± 0.11 (p = 0.30, respectively). In the SMILE and wavefront-guided LASIK groups 2 years postoperatively, 100% and 73% of eyes, respectively, were within 0.5 D of the prompted MRSE correction (p = 0.005). Changes in the MRSE of -0.10 ± 0.30 D and -0.23 ± 0.51 D occurred from 3 months to 2 years (p = 0.40, respectively). We found a significant correlation between myopic regression and the changes in the keratometric readings from 3 months to 2 years after wavefront-guided LASIK (r = -0.48, p = 0.002), but not after SMILE (r = -0.004, p = 0.90). Small-incision lenticule extraction offers better refractive outcomes than wavefront-guided LASIK during a 2-years follow-up for the correction of myopia and myopic astigmatism. © 2017 Acta Ophthalmologica Scandinavica Foundation. Published by John Wiley & Sons Ltd.

Results of Intraoperative Manual Cyclotorsion Compensation for Myopic Astigmatism in Patients Undergoing Small Incision Lenticule Extraction (SMILE).

PubMed

Ganesh, Sri; Brar, Sheetal; Pawar, Archana

2017-08-01

To study the safety, efficacy, and outcomes of manual cyclotorsion compensation in small incision lenticule extraction (SMILE) for myopic astigmatism. Eligible patients with myopia from -1.00 to -10.00 diopters (D) spherical equivalent with a minimum astigmatism of 0.75 D undergoing SMILE were included. Intraoperative cyclotorsion compensation was performed by gently rotating the cone and aligning the 0° to 180° limbal marks with the horizontal axis of the reticule of the right eye piece of the microscope of the femtosecond laser after activating the suction. In this study, 81 left eyes from 81 patients were analyzed for vector analysis of astigmatism. The mean cyclotorsion was 5.64° ± 2.55° (range: 2° to 12°). No significant differences were found for surgically induced astigmatism, difference vector, angle of error (AE), correction index, magnitude of error, index of success (IOS), and flattening index between 2 weeks and 3 months postoperatively (P > .05). The eyes were categorized into low (≤ 1.50 D, n = 37) and high (> 1.50 D, n = 44) cylinder groups. At 3 months, intergroup analysis showed a comparable correction index of 0.97 for the low and 0.93 for the high cylinder groups, suggesting a slight undercorrection of 3% and 7%, respectively (P = .14). However, the AE and IOS were significantly lower in the high compared to the low cylinder group (P = .032 and .024 for AE and IOS, respectively), suggesting better alignment of the treatment in the high cylinder group. However, the mean uncorrected distance visual acuity of both groups was comparable (P = .21), suggesting good visual outcomes in the low cylinder group despite a less favorable IOS. Manual compensation may be a safe, feasible, and effective approach to refine the results of astigmatism with SMILE, especially in higher degrees of cylinders. [J Refract Surg. 2017;33(8):506-512.]. Copyright 2017, SLACK Incorporated.

Refractive errors in presbyopic patients in Kano, Nigeria.

PubMed

Lawan, Abdu; Okpo, Eme; Philips, Ebisike

2014-01-01

The study is a retrospective review of the pattern of refractive errors in presbyopic patients seen in the eye clinic from January to December, 2009. The clinic refraction register was used to retrieve the case folders of all patients refracted during the review period. Information extracted includes patient's age, sex, and types of refractive error. Unaided and pin hole visual acuity was done with Snellen's or "E" Charts and near vision with Jaeger's chart in English or Hausa. All patients had basic eye examination and streak retinoscopy at two third meter working distance. The final subjective refractive correction given to the patients was used to categorize the type of refractive error. There were 5893 patients, 1584 had refractive error and 644 were presbyopic. There were 289 males and 355 females (M:F= 1:1.2). Presbyopia accounted for 10.9% of clinic attendance and 40% of patients with refractive error. Presbyopia was seen in 17%, the remaining 83% required distance correction; astigmatism was seen in 41%, hypermetropia 29%, myopia 9% and aphakia 4%. Refractive error was commoner in females than males and the relationship was statistically significant (P-value = 0.017; P < 0.05 considered significant). Presbyopia is common and most of the patients had other refractive errors. Full refraction is advised for all patients.

Measurement of refractive state and deprivation myopia in two strains of mice.

PubMed

Schaeffel, Frank; Burkhardt, Eva; Howland, Howard C; Williams, Robert W

2004-02-01

The mouse eye has a bright retinal image (f/number <1) but low optical quality (visual acuity about 0.5 cpd) that may render emmetropization unnecessary. However, this species is potentially a powerful model to study eye growth and myopia because its genome can be readily manipulated and has been completely sequenced. We have investigated how precisely eyes of mice can be refracted and tested whether deprivation myopia can be induced by frosted diffusers. An automated eccentric infrared photorefractor was adapted to refract eyes of two mouse strains--C57BL/6 (B6) and DBA/2 (D2)--during Tropicamide cycloplegia without anesthesia. Axial lengths were measured in highly magnified video images of freshly excised eyes. Plastic hemispherical diffusers were applied between postnatal days and 29 and left attached for 7 or 14 days. (1) Trial lenses ranging from +10 to -10 D produced high correlations between the brightness slope in the pupil and applied lens power (r = 0.81 and r = 0.87), demonstrating reliable refraction. Five repeated measures in 12 eyes showed an average standard deviation of 3.0 D, equivalent to an axial length change <10 microm (derived from schematic eye modeling). (2) Deprivation produced a significant shift toward myopia, relative to untreated eyes, but only after 14 days and only in B6 mice (p = 0.02 with or p = 0.00038 without one outlier; N = 9). In contrast, DBA/2J were unaffected by occlusion, perhaps due to mutations that target eye, lens, or anterior segment. (3) Both eyes of untreated animals often had axial lengths that differed markedly. Surprisingly, we detected no significant correlation between refractive error and axial length after treatment. The infrared refraction technique is sufficiently sensitive to resolve equivalent changes in axial length of only +/- 10 microm in alert mice. Prolonged occlusion produces a significant myopic shift in B6 mice, but not in D2 mice. Even among isogenic B6 mice, the response is variable for reasons that presumably trace back to subtle developmental, environmental, and technical factors.

PREVALENCE OF REFRACTIVE ERRORS IN MADRASSA STUDENTS OF HARIPUR DISTRICT.

PubMed

Atta, Zoia; Arif, Abdus Salam; Ahmed, Iftikhar; Farooq, Umer

2015-01-01

Visual impairment due to refractive errors is one of the most common problems among school-age children and is the second leading cause of treatable blindness. The Right to Sight, a global initiative launched by a coalition of non-government organizations and the World Health Organization (WHO), aims to eliminate avoidable visual impairment and blindness at a global level. In order to achieve this goal it is important to know the prevalence of different refractive errors in a community. Children and teenagers are the most susceptible groups to be affected by refractive errors. So, this population needs to be screened for different types of refractive errors. The study was done with the objective to find the frequency of different types of refractive errors in students of madrassas between the ages of 5-20 years in Haripur. This cross sectional study was done with 300 students between ages of 5-20 years in Madrassas of Haripur. The students were screened for refractive errors and the types of the errors were noted. After screening for refractive errors-the glasses were prescribed to the students. Myopia being 52.6% was the most frequent refractive error in students, followed by hyperopia 28.4% and astigmatism 19%. This study showed that myopia is an important problem in madrassa population. Females and males are almost equally affected. Spectacle correction of refractive errors is the cheapest and easy solution of this problem.

Effectiveness of Toric Orthokeratology in the Treatment of Patients with Combined Myopia and Astigmatism.

PubMed

Lyu, Byul; Hwang, Kyu Yeon; Kim, Sun Young; Kim, Su Young; Na, Kyung Sun

2016-12-01

The purpose of this multi-institute, single-group clinical trial was to evaluate the effectiveness and safety of toric orthokeratology lenses for the treatment of patients with combined myopia and astigmatism. A total of 44 patients were included in this clinical trial. The patients ranged in age from 7 to 49 years, with myopia of -0.75 to -6.0 diopters (D) and astigmatism of 1.25 to 4.0 D. After excluding 21 subjects, 23 subjects (39 eyes) were analyzed after toric orthokeratology lens use. The subjects underwent ophthalmologic examination after 1 day and 1, 2, 3, and 4 weeks of wearing overnight toric orthokeratology lenses. A total of 19 subjects (31 eyes) completed the trial after five subjects (eight eyes) dropped out. In the patients who completed the study by wearing lenses for 4 weeks, the myopic refractive error decreased significantly by 2.60 ± 2.21 D ( p < 0.001), from -3.65 ± 1.62 to -1.05 ± 1.64 D. The astigmatic refractive error were also significantly decreased by 0.63 ± 0.98 D ( p = 0.001), from 2.07 ± 0.83 to 1.44 ± 0.99 D. The mean uncorrected and corrected visual acuities before wearing the lenses were 2.14 ± 0.80 logarithm of the logMAR (logMAR) and 0.05 ± 0.13 logMAR, respectively, which changed to 0.12 ± 0.30 logarithm of the logMAR ( p < 0.001) and 0.01 ± 0.04 logMAR ( p = 0.156) after 4 weeks. No serious adverse reactions were reported during the clinical trial. Our results suggest that toric orthokeratology is an effective and safe treatment for correcting visual acuity in patients with combined myopia and astigmatism.

A Critical Evaluation of Refractive Outcomes Following LASIK for Moderate to High Astigmatism Using Two Excimer Laser Platforms.

PubMed

Patel, Sudi; Bohac, Maja; Biscevic, Alma; Koncarevic, Mateja; Anticic, Marija; Gabric, Nikica

2017-02-01

To calculate the surgically induced astigmatism (SIA) following LASIK and identify any association between SIA and the target induced astigmatism (TIA) at 1 year postoperatively. The SIA was calculated using the TIA and residual astigmatism values for [A] myopic astigmatism and [B] mixed astigmatism treated with either the [I] WaveLight Allegretto EyeQ 400-Hz (Alcon Laboratories, Inc. Fort Worth, TX) or [II] Schwind Amaris 750S (Schwind eye-tech-solutions, Kleinostheim, Germany) platforms. The TIA and corresponding SIA results were analyzed using various techniques. Key findings were the negative SIA power (y 1 ) was significantly correlated with negative TIA power (x 1 ) and sine of the TIA axis (x 2 ) as follows: [A] I, y 1 = 0.829x 1 -0.403x 2 -0.325 (F = 87.76, r = 0.804, P < .001, n = 127); II, y 1 = 0.891x 1 -0.037x 2 -0.192 (F = 240.06, r = 0.901, P < .001, n = 119) and [B] I, y 1 = 1.063x 1 +0.233x 2 +0.411 (F = 990.99, r = 0.881, P < .001, n = 61); II, y 1 = 1.029x 1 -0.115x 2 +0.322 (F = 270.12, r = 0.908, P < 0.001, n = 111). The sine of negative SIA axis (y 2 ) was significantly correlated with negative TIA power (x 1 ) and TIA axis (x 2 ) as follows: [A] I, y 2 = 0.951x 2 -0.007x 1 +0.008 (F = 446.58, r = 0.950, P < .001, n = 127); II, y 2 = 0.856x 2 +0.007x 1 +0.105 (F = 277.18, r = 0.912, P< .001, n = 119) and [B] I, y 2 = 0.953x 2 +0.009x 1 +0.075 (F = 362.6, r = 0.963, P < .001, n = 61); II, y 2 = 0.977x 2 -0.004x 1 +0.002 (F = 2910.9, r = 0.990, P < .001, n = 111). The predicted SIA power was up to 12% less than expected in cases of -6.00 diopters cylinder treated for myopic astigmatism using the Allegretto platform. The mean predicted angle of error (the angle between the SIA and TIA axes) was less than 4°, increasing to 12° for against-the-rule astigmatism. The Allegretto platform tended toward a clockwise axis rotational error, whereas the Amaris platform tended toward the opposite. [J Refract Surg. 2017;33(2):104-109.]. Copyright 2017, SLACK Incorporated.

Prevalence and risk factors of undercorrected refractive errors among Singaporean Malay adults: the Singapore Malay Eye Study.

PubMed

Rosman, Mohamad; Wong, Tien Y; Tay, Wan-Ting; Tong, Louis; Saw, Seang-Mei

2009-08-01

To describe the prevalence and the risk factors of undercorrected refractive error in an adult urban Malay population. This population-based, cross-sectional study was conducted in Singapore in 3280 Malay adults, aged 40 to 80 years. All individuals were examined at a centralized clinic and underwent standardized interviews and assessment of refractive errors and presenting and best corrected visual acuities. Distance presenting visual acuity was monocularly measured by using a logarithm of the minimum angle of resolution (logMAR) number chart at a distance of 4 m, with the participants wearing their "walk-in" optical corrections (spectacles or contact lenses), if any. Refraction was determined by subjective refraction by trained, certified study optometrists. Best corrected visual acuity was monocularly assessed and recorded in logMAR scores using the same test protocol as was used for presenting visual acuity. Undercorrected refractive error was defined as an improvement of at least 0.2 logMAR (2 lines equivalent) in the best corrected visual acuity compared with the presenting visual acuity in the better eye. The mean age of the subjects included in our study was 58 +/- 11 years, and 52% of the subjects were women. The prevalence rate of undercorrected refractive error among Singaporean Malay adults in our study (n = 3115) was 20.4% (age-standardized prevalence rate, 18.3%). More of the women had undercorrected refractive error than the men (21.8% vs. 18.8%, P = 0.04). Undercorrected refractive error was also more common in subjects older than 50 years than in subjects aged 40 to 49 years (22.6% vs. 14.3%, P < 0.001). Non-spectacle wearers were more likely to have undercorrected refractive errors than were spectacle wearers (24.4% vs. 14.4%, P < 0.001). Persons with primary school education or less were 1.89 times (P = 0.03) more likely to have undercorrected refractive errors than those with post-secondary school education or higher. In contrast, persons with a history of eye disease were 0.74 times (P = 0.003) less likely to have undercorrected refractive errors. The proportion of undercorrected refractive error among the Singaporean Malay adults with refractive errors was higher than that of the Singaporean Chinese adults with refractive errors. Undercorrected refractive error is a significant cause of correctable visual impairment among Singaporean Malay adults, affecting one in five persons.

Reproducibility of manifest refraction between surgeons and optometrists in a clinical refractive surgery practice.

PubMed

Reinstein, Dan Z; Yap, Timothy E; Carp, Glenn I; Archer, Timothy J; Gobbe, Marine

2014-03-01

To measure and compare the interobserver reproducibility of manifest refraction according to a standardized protocol for normal preoperative patients in a refractive surgery practice. Private clinic, London, United Kingdom. Retrospective case series. This retrospective study comprised patients attending 2 preoperative refractions before laser vision correction. The first manifest refraction was performed by 1 of 7 optometrists and the second manifest refraction by 1 of 2 surgeons, all trained using a standard manifest refraction protocol. Spherocylindrical data were converted into power vectors for analysis. The dioptric power differences between observers were calculated and analyzed. One thousand nine hundred twenty-two consecutive eyes were stratified into a myopia group and a hyperopia group and then further stratified by each surgeon-optometrist combination. The mean surgeon-optometrist dioptric power difference was 0.21 diopter (D) (range 0.15 to 0.32 D). The mean difference in spherical equivalent refraction was 0.03 D, with 95% of all refractions within ±0.44 D for all optometrist-surgeon combinations. The severity of myopic or hyperopic ametropia did not affect the interobserver reproducibility of the manifest refraction. There was close agreement in refraction between surgeons and optometrists using a standard manifest refraction protocol of less than 0.25 D. This degree of interobserver repeatability is similar to that in intraobserver repeatability studies published to date and may represent the value of training and the use of a standard manifest refraction protocol between refraction observers in a refractive surgery practice involving co-management between surgeons and optometrists. Copyright © 2014 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.

Holographic Refraction and the Measurement of Spherical Ametropia.

PubMed

Nguyen, Nicholas Hoai Nam

2016-10-01

To evaluate the performance of a holographic logMAR chart for the subjective spherical refraction of the human eye. Bland-Altman analysis was used to assess the level of agreement between subjective spherical refraction using the holographic logMAR chart and conventional autorefraction and subjective spherical refraction. The 95% limits of agreement (LoA) were calculated between holographic refraction and the two standard methods (subjective and autorefraction). Holographic refraction has a lower mean spherical refraction when compared to conventional refraction (LoA 0.11 ± 0.65 D) and when compared to autorefraction (LoA 0.36 ± 0.77 D). After correcting for systemic bias, this is comparable between autorefraction and conventional subjective refraction (LoA 0.45 ± 0.79 D). After correcting for differences in vergence distance and chromatic aberration between holographic and conventional refraction, approximately 65% (group 1) of measurements between holography and conventional subjective refraction were similar (MD = 0.13 D, SD = 0.00 D). The remaining 35% (group 2) had a mean difference of 0.45 D (SD = 0.12 D) between the two subjective methods. Descriptive statistics showed group 2's mean age (21 years, SD = 13 years) was considerably lower than group 1's mean age (41 years, SD = 17), suggesting accommodation may have a role in the greater mean difference of group 2. Overall, holographic refraction has good agreement with conventional refraction and is a viable alternative for spherical subjective refraction. A larger bias between holographic and conventional refraction was found in younger subjects than older subjects, suggesting an association between accommodation and myopic over-correction during holographic refraction.

Safety and efficacy of overnight orthokeratology in myopic children.

PubMed

Mika, Renée; Morgan, Bruce; Cron, Michael; Lotoczky, Josh; Pole, John

2007-05-01

This prospective case series was conducted to describe the safety and efficacy of orthokeratology with the Emerald Contact Lens for Overnight Orthokeratology (Oprifocon A; Euclid Systems Corporation, Herndon, Virginia) among young myopes. Twenty subjects (ages 10 to 16) were enrolled in the 6-month pilot study. Subjects were fit empirically with overnight orthokeratology lenses and evaluated at 1 day, 1 week, 1 month, 2 months, 3 months, and 6 months. Sixteen subjects completed the study. The mean baseline spherical equivalent refraction (SER) was -2.06 diopters (D) (+/-0.75). The mean SER at 6 months was -0.16 D (+/-0.38). The mean baseline uncorrected acuity was 0.78 (+/-0.28) logarithmic minimum angle of resolution (logMAR) equivalent (20/100 Snellen). The mean logMAR equivalent at 6 months was -0.03 +/- 0.12 (<20/20 Snellen). On average, 40% of eyes showed some type of corneal staining between the 1-week and 6-month visits. No serious adverse events occurred during the study. In contrast to previously published studies that reported maximum results at 2 weeks, subjects reached maximum reduction in myopia at the 1-week visit and, on average, obtained a 92.2% reduction in spherical equivalent refractive error at 6 months. This pilot study lends to a growing body of evidence that short-term correction of mild to moderate myopia with overnight orthokeratology is safe and efficacious in children and adolescents.

Profile of refractive errors in cerebral palsy: impact of severity of motor impairment (GMFCS) and CP subtype on refractive outcome.

PubMed

Saunders, Kathryn J; Little, Julie-Anne; McClelland, Julie F; Jackson, A Jonathan

2010-06-01

To describe refractive status in children and young adults with cerebral palsy (CP) and relate refractive error to standardized measures of type and severity of CP impairment and to ocular dimensions. A population-based sample of 118 participants aged 4 to 23 years with CP (mean 11.64 +/- 4.06) and an age-appropriate control group (n = 128; age, 4-16 years; mean, 9.33 +/- 3.52) were recruited. Motor impairment was described with the Gross Motor Function Classification Scale (GMFCS), and subtype was allocated with the Surveillance of Cerebral Palsy in Europe (SCPE). Measures of refractive error were obtained from all participants and ocular biometry from a subgroup with CP. A significantly higher prevalence and magnitude of refractive error was found in the CP group compared to the control group. Axial length and spherical refractive error were strongly related. This relation did not improve with inclusion of corneal data. There was no relation between the presence or magnitude of spherical refractive errors in CP and the level of motor impairment, intellectual impairment, or the presence of communication difficulties. Higher spherical refractive errors were significantly associated with the nonspastic CP subtype. The presence and magnitude of astigmatism were greater when intellectual impairment was more severe, and astigmatic errors were explained by corneal dimensions. Conclusions. High refractive errors are common in CP, pointing to impairment of the emmetropization process. Biometric data support this In contrast to other functional vision measures, spherical refractive error is unrelated to CP severity, but those with nonspastic CP tend to demonstrate the most extreme errors in refraction.

Distribution of intraocular pressure and its determinants in an Iranian adult population.

PubMed

Hashemi, Hassan; Khabazkhoob, Mehdi; Emamian, Mohammad Hassan; Shariati, Mohammad; Yekta, Abbasali; Fotouhi, Akbar

2016-01-01

To determine the distribution of intraocular pressure (IOP) and its determinants in an Iranian population. In a cross-sectional survey, random cluster sampling was conducted from the 40-64 years old population of Shahroud, in the north of Iran. All participants had optometry and ophthalmic exams. IOP was determined using the Goldmann tonometry method and biometric components were measured. Of the 6311 people selected for the study, 5190 (82.2%) participated. The mean age of the participants was 50.9±6.2y and 58.7% of them were female. Mean IOP was 12.87±2.27 mm Hg. In this study 0.3% of the participants had an IOP higher than 21 mm Hg. The multiple linear regression model revealed that sex (Coef=-0.30; 95% CI: -0.43 to -0.17), diabetes (Coef=0.43; 95% CI: 0.19 to 0.67), high systolic blood pressure (Coef=0.02; 95% CI: 0.01 to 0.02), high body mass index (BMI) (Coef=0.03; 95% CI: 0.01 to 0.04), higher education (Coef=0.02, 95% CI: 0.01 to 0.04), thicker central corneal thickness (Coef=0.01; 95% CI: 0.01 to 0.02), and myopic shift in spherical equivalent (Coef=-0.14; 95% CI: -0.18 to -0.10) significantly correlated with high IOP. The IOP in this 40-64 years old population is low overall. In the north of Iran, average IOP is statistically significantly correlated with female sex, diabetes, higher BMI, systolic blood pressure, higher education, thicker cornea, and myopic refractive error.

Correlations between Preoperative Angle Parameters and Postoperative Unpredicted Refractive Errors after Cataract Surgery in Open Angle Glaucoma (AOD 500).

PubMed

Lee, Wonseok; Bae, Hyoung Won; Lee, Si Hyung; Kim, Chan Yun; Seong, Gong Je

2017-03-01

To assess the accuracy of intraocular lens (IOL) power prediction for cataract surgery with open angle glaucoma (OAG) and to identify preoperative angle parameters correlated with postoperative unpredicted refractive errors. This study comprised 45 eyes from 45 OAG subjects and 63 eyes from 63 non-glaucomatous cataract subjects (controls). We investigated differences in preoperative predicted refractive errors and postoperative refractive errors for each group. Preoperative predicted refractive errors were obtained by biometry (IOL-master) and compared to postoperative refractive errors measured by auto-refractometer 2 months postoperatively. Anterior angle parameters were determined using swept source optical coherence tomography. We investigated correlations between preoperative angle parameters [angle open distance (AOD); trabecular iris surface area (TISA); angle recess area (ARA); trabecular iris angle (TIA)] and postoperative unpredicted refractive errors. In patients with OAG, significant differences were noted between preoperative predicted and postoperative real refractive errors, with more myopia than predicted. No significant differences were recorded in controls. Angle parameters (AOD, ARA, TISA, and TIA) at the superior and inferior quadrant were significantly correlated with differences between predicted and postoperative refractive errors in OAG patients (-0.321 to -0.408, p<0.05). Superior quadrant AOD 500 was significantly correlated with postoperative refractive differences in multivariate linear regression analysis (β=-2.925, R²=0.404). Clinically unpredicted refractive errors after cataract surgery were more common in OAG than in controls. Certain preoperative angle parameters, especially AOD 500 at the superior quadrant, were significantly correlated with these unpredicted errors.

Correlations between Preoperative Angle Parameters and Postoperative Unpredicted Refractive Errors after Cataract Surgery in Open Angle Glaucoma (AOD 500)

PubMed Central

Lee, Wonseok; Bae, Hyoung Won; Lee, Si Hyung; Kim, Chan Yun

2017-01-01

Purpose To assess the accuracy of intraocular lens (IOL) power prediction for cataract surgery with open angle glaucoma (OAG) and to identify preoperative angle parameters correlated with postoperative unpredicted refractive errors. Materials and Methods This study comprised 45 eyes from 45 OAG subjects and 63 eyes from 63 non-glaucomatous cataract subjects (controls). We investigated differences in preoperative predicted refractive errors and postoperative refractive errors for each group. Preoperative predicted refractive errors were obtained by biometry (IOL-master) and compared to postoperative refractive errors measured by auto-refractometer 2 months postoperatively. Anterior angle parameters were determined using swept source optical coherence tomography. We investigated correlations between preoperative angle parameters [angle open distance (AOD); trabecular iris surface area (TISA); angle recess area (ARA); trabecular iris angle (TIA)] and postoperative unpredicted refractive errors. Results In patients with OAG, significant differences were noted between preoperative predicted and postoperative real refractive errors, with more myopia than predicted. No significant differences were recorded in controls. Angle parameters (AOD, ARA, TISA, and TIA) at the superior and inferior quadrant were significantly correlated with differences between predicted and postoperative refractive errors in OAG patients (-0.321 to -0.408, p<0.05). Superior quadrant AOD 500 was significantly correlated with postoperative refractive differences in multivariate linear regression analysis (β=-2.925, R2=0.404). Conclusion Clinically unpredicted refractive errors after cataract surgery were more common in OAG than in controls. Certain preoperative angle parameters, especially AOD 500 at the superior quadrant, were significantly correlated with these unpredicted errors. PMID:28120576

Survey of Radar Refraction Error Corrections

DTIC Science & Technology

2016-11-01

ELECTRONIC TRAJECTORY MEASUREMENTS GROUP RCC 266-16 SURVEY OF RADAR REFRACTION ERROR CORRECTIONS DISTRIBUTION A: Approved for...DOCUMENT 266-16 SURVEY OF RADAR REFRACTION ERROR CORRECTIONS November 2016 Prepared by Electronic...This page intentionally left blank. Survey of Radar Refraction Error Corrections, RCC 266-16 iii Table of Contents Preface

Blue Light Protects Against Temporal Frequency Sensitive Refractive Changes.

PubMed

Rucker, Frances; Britton, Stephanie; Spatcher, Molly; Hanowsky, Stephan

2015-09-01

Time spent outdoors is protective against myopia. The outdoors allows exposure to short-wavelength (blue light) rich sunlight, while indoor illuminants can be deficient at short-wavelengths. In the current experiment, we investigate the role of blue light, and temporal sensitivity, in the emmetropization response. Five-day-old chicks were exposed to sinusoidal luminance modulation of white light (with blue; N = 82) or yellow light (without blue; N = 83) at 80% contrast, at one of six temporal frequencies: 0, 0.2, 1, 2, 5, 10 Hz daily for 3 days. Mean illumination was 680 lux. Changes in ocular components and corneal curvature were measured. Refraction, eye length, and choroidal changes were dependent on the presence of blue light (P < 0.03, all) and on temporal frequency (P < 0.03, all). In the presence of blue light, refraction did not change across frequencies (mean change -0.24 [diopters] D), while in the absence of blue light, we observed a hyperopic shift (>1 D) at high frequencies, and a myopic shift (>-0.6 D) at low frequencies. With blue light there was little difference in eye growth across frequencies (77 μm), while in the absence of blue light, eyes grew more at low temporal frequencies and less at high temporal frequencies (10 vs. 0.2 Hz: 145 μm; P < 0.003). Overall, neonatal astigmatism was reduced with blue light. Illuminants rich in blue light can protect against myopic eye growth when the eye is exposed to slow changes in luminance contrast as might occur with near work.

Blue Light Protects Against Temporal Frequency Sensitive Refractive Changes

PubMed Central

Rucker, Frances; Britton, Stephanie; Spatcher, Molly; Hanowsky, Stephan

2015-01-01

Purpose Time spent outdoors is protective against myopia. The outdoors allows exposure to short-wavelength (blue light) rich sunlight, while indoor illuminants can be deficient at short-wavelengths. In the current experiment, we investigate the role of blue light, and temporal sensitivity, in the emmetropization response. Methods Five-day-old chicks were exposed to sinusoidal luminance modulation of white light (with blue; N = 82) or yellow light (without blue; N = 83) at 80% contrast, at one of six temporal frequencies: 0, 0.2, 1, 2, 5, 10 Hz daily for 3 days. Mean illumination was 680 lux. Changes in ocular components and corneal curvature were measured. Results Refraction, eye length, and choroidal changes were dependent on the presence of blue light (P < 0.03, all) and on temporal frequency (P < 0.03, all). In the presence of blue light, refraction did not change across frequencies (mean change −0.24 [diopters] D), while in the absence of blue light, we observed a hyperopic shift (>1 D) at high frequencies, and a myopic shift (>−0.6 D) at low frequencies. With blue light there was little difference in eye growth across frequencies (77 μm), while in the absence of blue light, eyes grew more at low temporal frequencies and less at high temporal frequencies (10 vs. 0.2 Hz: 145 μm; P < 0.003). Overall, neonatal astigmatism was reduced with blue light. Conclusions Illuminants rich in blue light can protect against myopic eye growth when the eye is exposed to slow changes in luminance contrast as might occur with near work. PMID:26393671

Influence of indoor and outdoor activities on progression of myopia during puberty.

PubMed

Öner, Veysi; Bulut, Asker; Oruç, Yavuz; Özgür, Gökhan

2016-02-01

The purpose of this study was to investigate whether time spent on indoor and outdoor activities or the other possible risk factors including age, gender, parental history, and initial refraction was associated with progression of myopia, during puberty. Fifty eyes of 50 myopic children aged 9-14 years were enrolled in the study. The parents were interviewed to determine the amounts of time in hours per day spent on reading and writing, using computer, watching TV, and outdoor activities (i.e., sports, games, or being outdoor with no activities) on an average day. The annual myopia progression rate (diopters per year) was calculated for each subject and was used in the statistical analyses. The mean initial age of the subjects was 10.9 ± 1.5 (ranging from 9 to 14) years. The mean follow-up period was 33.3 ± 10.3 (ranging from 17 to 55) months. There was a significant increase in the mean myopia value of the subjects after follow-up period (p < 0.001). The mean daily time spent on reading and writing and initial refraction value were independently associated with annual myopic progression rate. On the other hand, age, gender, parental myopia, and the mean daily times spent on computer use, watching TV, and outdoor activities had no correlations with annual myopia progression rate. The present study showed that myopia progression was associated with time spent on reading and writing and initial refraction value, during puberty. However, myopia progression was not associated with parental myopia, age, gender, and daily times spent on using computer, watching TV, and outdoor activities.

[Pathophysiology of myopia: nature versus nurture].

PubMed

Cassagne, M; Malecaze, F; Soler, V

2014-05-01

Myopia is the most frequent refractive disorder in the world. It has become a real Public Health problem, due to its frequency and to high myopia-related blinding complications. Myopic progression depends on genetic and environmental factors. Genetic studies have identified more than forty candidate genes that take part in pathophysiological pathways, from retinal phototransduction to axial lengthening via scleral remodelling. Environmental factors also influence scleral remodelling by way of visual perception. In the case of predominant attention to near tasks, a physiological feedback loop leads to axial growth. This phenomenon, called active emmetropization, is particularly obvious in animal models and in some human populations. To date, research has failed to identify a molecule common to all the implicated metabolic pathways which could be a target for an effective preventive treatment against myopic progression. Copyright © 2014 Elsevier Masson SAS. All rights reserved.

Myopes show increased susceptibility to nearwork aftereffects.

PubMed

Ciuffreda, K J; Wallis, D M

1998-09-01

Some aspects of accommodation may be slightly abnormal (or different) in myopes, compared with accommodation in emmetropes and hyperopes. For example, the initial magnitude of accommodative adaptation in the dark after nearwork is greatest in myopes. However, the critical test is to assess this initial accommodative aftereffect and its subsequent decay in the light under more natural viewing conditions with blur-related visual feedback present, if a possible link between this phenomenon and clinical myopia is to be considered. Subjects consisted of adult late- (n = 11) and early-onset (n = 13) myopes, emmetropes (n = 11), and hyperopes (n = 9). The distance-refractive state was assessed objectively using an autorefractor immediately before and after a 10-minute binocular near task at 20 cm (5 diopters [D]). Group results showed that myopes were most susceptible to the nearwork aftereffect. It averaged 0.35 D in initial magnitude, with considerably faster posttask decay to baseline in the early-onset (35 seconds) versus late-onset (63 seconds) myopes. There was no myopic aftereffect in the remaining two refractive groups. The myopes showed particularly striking accommodatively related nearwork aftereffect susceptibility. As has been speculated and found by many others, transient pseudomyopia may cause or be a precursor to permanent myopia or myopic progression. Time-integrated increased retinal defocus causing axial elongation is proposed as a possible mechanism.

The effect of ambient illuminance on the development of deprivation myopia in chicks.

PubMed

Ashby, Regan; Ohlendorf, Arne; Schaeffel, Frank

2009-11-01

Recent epidemiologic studies have shown that children who spend a higher proportion of time outdoors are less likely to develop myopia. This study was undertaken to investigate whether light levels may be a relevant factor in the development of myopia. METHODS; Paradigm 1: Chicks were fitted with translucent diffusers for 5 days, with the diffusers removed daily for 15 minutes under one of three lighting conditions: (1) normal laboratory lighting (500 lux), (2) intense laboratory lighting (15,000 lux), or (3) daylight (30,000 lux). A control group, which continuously wore diffusers, was also kept under an illumination of 500 lux. Paradigm 2: Chicks fitted with translucent diffusers were raised for 4 days under one of three lighting conditions: (1) low laboratory lighting (50 lux, n = 9), (2) normal laboratory lighting (500 lux, n = 18), or (3) intense laboratory lights (15,000 lux, n = 9). In groups 1 and 3, the chicks were exposed to either low or high ambient illuminances for a period of 6 hours per day (10 AM-4 PM), but were kept under 500 lux for the remaining time of the light phase. Axial length and refraction were measured at the commencement and cessation of all treatments, with corneal curvature measured additionally in paradigm 2. Paradigm 1: The chicks exposed daily to sunlight for 15 minutes had significantly shorter eyes (8.81 +/- 0.05 mm; P < 0.01) and less myopic refractions (-1.1 +/- 0.45 D; P < 0.01) than did the chicks that had their diffusers removed under normal laboratory light levels (8.98 +/- 0.03 mm, -5.3 +/- 0.5 D). If the diffusers were removed under intense laboratory lights, the chicks also developed shorter eyes (8.88 +/- 0.04 mm; P < 0.01) and less myopic refractions (-3.4 +/- 0.6D; P < 0.01). Paradigm 2: The chicks that wore diffusers continuously under high illuminance had shorter eyes (8.54 +/- 0.02 mm; P < 0.01) and less myopic refractions (+0.04 +/- 0.7D; P < 0.001) compared with those chicks reared under normal light levels (8.64 +/- 0.06 mm, -5.3 +/- 0.9 D). Low illuminance (50 lux) did not further increase deprivation myopia. Exposing chicks to high illuminances, either sunlight or intense laboratory lights, retards the development of experimental myopia. These results, in conjunction with recent epidemiologic findings, suggest that daily exposure to high light levels may have a protective effect against the development of school-age myopia in children.

Evaluation of thermal load during laser corneal refractive surgery using infrared thermography

NASA Astrophysics Data System (ADS)

Brunsmann, U.; Sauer, U.; Arba-Mosquera, S.; Magnago, T.; Triefenbach, N.

2010-09-01

Infrared thermography is used for evaluation of the mean temperature as a measure of thermal load during corneal refractive surgery. An experimental method to determine emissivity and to calibrate the thermografic system is presented. In a case study on the porcine eye two dimensional temperature distributions with lateral resolution of 170 μm and line scans with temporal resolution of 13 μs are discussed with respect to the meaning of mean temperature. Using the newest generation of surgery equipment it is shown, that the mean temperature rise can be kept below 5 °C during myopic laser in situ keratomileusis (LASIK) treatments corresponding to an aberration-free correction of -2.75 diopter.

Nature of the refractive errors in rhesus monkeys (Macaca mulatta) with experimentally induced ametropias.

PubMed

Qiao-Grider, Ying; Hung, Li-Fang; Kee, Chea-Su; Ramamirtham, Ramkumar; Smith, Earl L

2010-08-23

We analyzed the contribution of individual ocular components to vision-induced ametropias in 210 rhesus monkeys. The primary contribution to refractive-error development came from vitreous chamber depth; a minor contribution from corneal power was also detected. However, there was no systematic relationship between refractive error and anterior chamber depth or between refractive error and any crystalline lens parameter. Our results are in good agreement with previous studies in humans, suggesting that the refractive errors commonly observed in humans are created by vision-dependent mechanisms that are similar to those operating in monkeys. This concordance emphasizes the applicability of rhesus monkeys in refractive-error studies. Copyright 2010 Elsevier Ltd. All rights reserved.

Nature of the Refractive Errors in Rhesus Monkeys (Macaca mulatta) with Experimentally Induced Ametropias

PubMed Central

Qiao-Grider, Ying; Hung, Li-Fang; Kee, Chea-su; Ramamirtham, Ramkumar; Smith, Earl L.

2010-01-01

We analyzed the contribution of individual ocular components to vision-induced ametropias in 210 rhesus monkeys. The primary contribution to refractive-error development came from vitreous chamber depth; a minor contribution from corneal power was also detected. However, there was no systematic relationship between refractive error and anterior chamber depth or between refractive error and any crystalline lens parameter. Our results are in good agreement with previous studies in humans, suggesting that the refractive errors commonly observed in humans are created by vision-dependent mechanisms that are similar to those operating in monkeys. This concordance emphasizes the applicability of rhesus monkeys in refractive-error studies. PMID:20600237

Contribution of Optical Zone Decentration and Pupil Dilation on the Change of Optical Quality After Myopic Photorefractive Keratectomy in a Cat Model

PubMed Central

Bühren, Jens; Yoon, Geunyoung; MacRae, Scott; Huxlin, Krystel

2010-01-01

PURPOSE To simulate the simultaneous contribution of optical zone decentration and pupil dilation on retinal image quality using wavefront error data from a myopic photorefractive keratectomy (PRK) cat model. METHODS Wavefront error differences were obtained from five cat eyes 19±7 weeks (range: 12 to 24 weeks) after spherical myopic PRK for −6.00 diopters (D) (three eyes) and −10.00 D (two eyes). A computer model was used to simulate decentration of a 6-mm sub-aperture relative to the measured wavefront error difference. Changes in image quality (visual Strehl ratio based on the optical transfer function [VSOTF]) were computed for simulated decentrations from 0 to 1500 μm over pupil diameters of 3.5 to 6.0 mm in 0.5-mm steps. For each eye, a bivariate regression model was applied to calculate the simultaneous contribution of pupil dilation and decentration on the pre- to postoperative change of the log VSOTF. RESULTS Pupil diameter and decentration explained up to 95% of the variance of VSOTF change (adjusted R2=0.95). Pupil diameter had a higher impact on VSOTF (median β=−0.88, P<.001) than decentration (median β= −0.45, P<.001). If decentration-induced lower order aberrations were corrected, the impact of decentration further decreased (β= −0.26) compared to the influence of pupil dilation (β= −0.95). CONCLUSIONS Both pupil dilation and decentration of the optical zone affected the change of retinal image quality (VSOTF) after myopic PRK with decentration exerting a lower impact on VSOTF change. Thus, under physiological conditions pupil dilation is likely to have more effect on VSOTF change after PRK than optical zone decentration. PMID:20229950

Contribution of optical zone decentration and pupil dilation on the change of optical quality after myopic photorefractive keratectomy in a cat model.

PubMed

Bühren, Jens; Yoon, Geunyoung; MacRae, Scott; Huxlin, Krystel

2010-03-01

To simulate the simultaneous contribution of optical zone decentration and pupil dilation on retinal image quality using wavefront error data from a myopic photorefractive keratectomy (PRK) cat model. Wavefront error differences were obtained from five cat eyes 19+/-7 weeks (range: 12 to 24 weeks) after spherical myopic PRK for -6.00 diopters (D) (three eyes) and -10.00 D (two eyes). A computer model was used to simulate decentration of a 6-mm sub-aperture relative to the measured wavefront error difference. Changes in image quality (visual Strehl ratio based on the optical transfer function [VSOTF]) were computed for simulated decentrations from 0 to 1500 mum over pupil diameters of 3.5 to 6.0 mm in 0.5-mm steps. For each eye, a bivariate regression model was applied to calculate the simultaneous contribution of pupil dilation and decentration on the pre- to postoperative change of the log VSOTF. Pupil diameter and decentration explained up to 95% of the variance of VSOTF change (adjusted R(2)=0.95). Pupil diameter had a higher impact on VSOTF (median beta=-0.88, P<.001) than decentration (median beta=-0.45, P<.001). If decentration-induced lower order aberrations were corrected, the impact of decentration further decreased (beta=-0.26) compared to the influence of pupil dilation (beta=-0.95). Both pupil dilation and decentration of the optical zone affected the change of retinal image quality (VSOTF) after myopic PRK with decentration exerting a lower impact on VSOTF change. Thus, under physiological conditions pupil dilation is likely to have more effect on VSOTF change after PRK than optical zone decentration. Copyright 2010, SLACK Incorporated.

Atmospheric refraction effects on baseline error in satellite laser ranging systems

NASA Technical Reports Server (NTRS)

Im, K. E.; Gardner, C. S.

1982-01-01

Because of the mathematical complexities involved in exact analyses of baseline errors, it is not easy to isolate atmospheric refraction effects; however, by making certain simplifying assumptions about the ranging system geometry, relatively simple expressions can be derived which relate the baseline errors directly to the refraction errors. The results indicate that even in the absence of other errors, the baseline error for intercontinental baselines can be more than an order of magnitude larger than the refraction error.

Postoperative Refractive Errors Following Pediatric Cataract Extraction with Intraocular Lens Implantation.

PubMed

Indaram, Maanasa; VanderVeen, Deborah K

2018-01-01

Advances in surgical techniques allow implantation of intraocular lenses (IOL) with cataract extraction, even in young children. However, there are several challenges unique to the pediatric population that result in greater degrees of postoperative refractive error compared to adults. Literature review of the techniques and outcomes of pediatric cataract surgery with IOL implantation. Pediatric cataract surgery is associated with several sources of postoperative refractive error. These include planned refractive error based on age or fellow eye status, loss of accommodation, and unexpected refractive errors due to inaccuracies in biometry technique, use of IOL power formulas based on adult normative values, and late refractive changes due to unpredictable eye growth. Several factors can preclude the achievement of optimal refractive status following pediatric cataract extraction with IOL implantation. There is a need for new technology to reduce postoperative refractive surprises and address refractive adjustment in a growing eye.

Myopia, contact lens use and self-esteem

PubMed Central

Dias, Lynette; Manny, Ruth E; Weissberg, Erik; Fern, Karen D

2013-01-01

Purpose To evaluate whether contact lens (CL) use was associated with self-esteem in myopic children originally enrolled in the Correction of Myopia Evaluation Trial (COMET), that after five years continued as an observational study of myopia progression with CL use permitted. Methods Usable data at the six-year visit, one year after CL use was allowed (n = 423/469, age 12-17 years), included questions on CL use, refractive error measurements and self-reported self-esteem in several areas (scholastic/athletic competence, physical appearance, social acceptance, behavioural conduct and global self-worth). Self-esteem, scored from 1 (low) to 4 (high), was measured by the Self-Perception Profile for Children in participants under 14 years or the Self-Perception Profile for Adolescents, in those 14 years and older. Multiple regression analyses were used to evaluate associations between self-esteem and relevant factors identified by univariate analyses (e.g., CL use, gender, ethnicity), while adjusting for baseline self-esteem prior to CL use. Results Mean (±SD) self-esteem scores at the six-year visit (mean age=15.3±1.3 years; mean refractive error= −4.6 ±1.5D) ranged from 2.74 (± 0.76) on athletic competence to 3.33 (± 0.53) on global self-worth. CL wearers (n=224) compared to eyeglass wearers (n=199) were more likely to be female (p<0.0001). Those who chose to wear CLs had higher social acceptance, athletic competence and behavioural conduct scores (p < 0.05) at baseline compared to eyeglass users. CL users continued to report higher social acceptance scores at the six-year visit (p=0.03), after adjusting for baseline scores and other covariates. Ethnicity was also independently associated with social acceptance in the multivariable analyses (p=0.011); African-Americans had higher scores than Asians, Whites and Hispanics. Age and refractive error were not associated with self-esteem or CL use. Conclusions COMET participants who chose to wear CLs after five years of eyeglass use had higher self-esteem compared to those who remained in glasses both preceding and following CL use. This suggests that self-esteem may influence the decision to wear CLs and that CLs in turn are associated with higher self-esteem in individuals most likely to wear them. PMID:23763482

A Comparative Study to Assess the Predictability of Different IOL Power Calculation Formulas in Eyes of Short and Long Axial Length.

PubMed

Doshi, Dharmil; Limdi, Purvi; Parekh, Nilesh; Gohil, Neepa

2017-01-01

Accurate Intraocular Lens (IOL) power calculation in cataract surgery is very important for providing postoperative precise vision. Selection of most appropriate formula is difficult in high myopic and hypermetropic patients. To investigate the predictability of different IOL (Intra Ocular Lens) power calculation formulae in eyes with short and long Axial Length (AL) and to find out most accurate IOL power calculation formula in both groups. A prospective study was conducted on 80 consecutive patients who underwent phacoemulsification with monofocal IOL implantation after obtaining an informed and written consent. Preoperative keratometry was done by IOL Master. Axial length and anterior chamber depth was measured using A-scan machine ECHORULE 2 (BIOMEDIX). Patients were divided into two groups based on AL. (40 in each group). Group A with AL<22 mm and Group B with AL>24.5 mm. The IOL power calculation in each group was done by Haigis, Hoffer Q, Holladay-I, SRK/T formulae using the software of ECHORULE 2. The actual postoperative Spherical Equivalent (SE), Estimation error (E) and Absolute Error (AE) were calculated at one and half months and were used in data analysis. The predictive accuracy of each formula in each group was analyzed by comparing the Absolute Error (AE). The Kruskal Wallis test was used to compare differences in the (AE) of the formulae. A statistically significant difference was defined as p-value<0.05. In Group A, Hoffer Q, Holladay 1 and SRK/T formulae were equally accurate in predicting the postoperative refraction after cataract surgery (IOL power calculation) in eyes with AL less than 22.0 mm and accuracy of these three formulae was significantly higher than Haigis formula. Whereas in Group B, Hoffer Q, Holladay 1, SRK/T and Haigis formulae were equally accurate in predicting the postoperative refraction after cataract surgery (IOL power calculation) in eyes with AL more than 24.5 mm. Hoffer Q, Holladay 1 and SRK/T formulae were showing significantly higher accuracy than Haigis formula in predicting the postoperative refraction after cataract surgery (IOL power calculation) in eyes with AL less than 22.0 mm. In eyes with AL more than 24.5 mm Hoffer Q, Holladay 1, SRK/T and Haigis formulae were equally accurate.

A Comparative Study to Assess the Predictability of Different IOL Power Calculation Formulas in Eyes of Short and Long Axial Length

PubMed Central

Limdi, Purvi; Parekh, Nilesh; Gohil, Neepa

2017-01-01

Introduction Accurate Intraocular Lens (IOL) power calculation in cataract surgery is very important for providing postoperative precise vision. Selection of most appropriate formula is difficult in high myopic and hypermetropic patients. Aim To investigate the predictability of different IOL (Intra Ocular Lens) power calculation formulae in eyes with short and long Axial Length (AL) and to find out most accurate IOL power calculation formula in both groups. Materials and Methods A prospective study was conducted on 80 consecutive patients who underwent phacoemulsification with monofocal IOL implantation after obtaining an informed and written consent. Preoperative keratometry was done by IOL Master. Axial length and anterior chamber depth was measured using A-scan machine ECHORULE 2 (BIOMEDIX). Patients were divided into two groups based on AL. (40 in each group). Group A with AL<22 mm and Group B with AL>24.5 mm. The IOL power calculation in each group was done by Haigis, Hoffer Q, Holladay-I, SRK/T formulae using the software of ECHORULE 2. The actual postoperative Spherical Equivalent (SE), Estimation error (E) and Absolute Error (AE) were calculated at one and half months and were used in data analysis. The predictive accuracy of each formula in each group was analyzed by comparing the Absolute Error (AE). The Kruskal Wallis test was used to compare differences in the (AE) of the formulae. A statistically significant difference was defined as p-value<0.05. Results In Group A, Hoffer Q, Holladay 1 and SRK/T formulae were equally accurate in predicting the postoperative refraction after cataract surgery (IOL power calculation) in eyes with AL less than 22.0 mm and accuracy of these three formulae was significantly higher than Haigis formula. Whereas in Group B, Hoffer Q, Holladay 1, SRK/T and Haigis formulae were equally accurate in predicting the postoperative refraction after cataract surgery (IOL power calculation) in eyes with AL more than 24.5 mm. Conclusion Hoffer Q, Holladay 1 and SRK/T formulae were showing significantly higher accuracy than Haigis formula in predicting the postoperative refraction after cataract surgery (IOL power calculation) in eyes with AL less than 22.0 mm. In eyes with AL more than 24.5 mm Hoffer Q, Holladay 1, SRK/T and Haigis formulae were equally accurate. PMID:28273986

Noncycloplegic photorefractive screening in pre-school children with the "PowerRefractor" in a pediatric practice.

PubMed

Schaeffel, Frank; Mathis, Ute; Brüggemann, Gunther

2007-07-01

To provide a framework for typical refractive development, as measured without cycloplegia with a commercial infrared photorefractor. To evaluate the usefulness of the screening for refractive errors, we retrospectively analyzed the data of a large number of unselected children of different ages in a pediatric practice in Tuebingen, Germany. During the standard regular preventive examinations that are performed in 80% to 90% of the young children in Germany by a pediatrician (the German "U1 to U9" system), 736 children were also measured with the first generation PowerRefractor (made by MCS, Reutlingen, Germany, but no longer available in this version). Of those, 172 were also measured with +3 D spectacles to find out whether this helps detect hyperopia. Children with more than +2 D of hyperopia or astigmatism, more than 1.5 D of anisometropia, or more than 1 D of myopia in the second year of life were referred to an eye care specialist. The actions taken by the eye care specialist were used to evaluate the merits of the screening. The average noncycloplegic spherical refractive errors in the right eyes declined linearly from +0.93 to +0.62 D over the first 6 years (p < 0.001)-between 1.5 and 0.5 D less hyperopic than in published studies with cycloplegic retinoscopy. As expected, +3 D spectacle lenses moved the refractions into the myopic direction, but this shift was not smaller in hyperopic children. The average negative cylinder magnitudes declined from -0.89 to 0.48 D (linear regression: p < 0.001). The J0 components displayed high correlations in both eyes (p < 0.001) but the J45 components did not. The average absolute anisometropias (difference of spheres) declined from 0.37 to 0.23 (linear regression: p < 0.001). Of the 736 children, 85 (11.5%) were referred to an eye care specialist. Of these, 52 received spectacles (61.2%), 14 (16.4%) were identified as "at risk" and remained under observation, and 18 (21.2%) were considered "false-positive." Non cycloplegic photorefraction provides considerably less hyperopic readings than retinoscopy under cycloplegia. Additional refractions performed through binocular +3-D lenses did not facilitate detection of hyperopia. With the referral criteria above, 11% of the children were referred to an eye care specialist, but with a 20% false-positive rate. The screening had some power to identify children at risk but the number of false-negatives remained uncertain.

Anisometropia of spherical equivalent and astigmatism among myopes: a 23-year follow-up study of prevalence and changes from childhood to adulthood.

PubMed

Pärssinen, Olavi; Kauppinen, Markku

2017-08-01

To study anisometropia of spherical equivalent and astigmatism from the onset of myopia at school age to adulthood. A total of 240 myopic schoolchildren (mean age 10.9 years), with no previous spectacles, were recruited during 1983-1984 to a randomized 3-year clinical trial of bifocal treatment of myopia. Examinations with subjective cyclopedic refraction were repeated 3 years later (follow-up 1) for 238 subjects and thereafter at the mean ages of 23.2 (follow-up 2) and 33.9 years (follow-up 3) for 178 and 134 subjects. After exclusions, the 102 subjects who attended all three follow-ups were included in the analyses. Corneal refractive power and astigmatism and anterior chamber depth was measured with Pentacam topography and axial length with IOL master at study end. Prevalence and changes in anisometropia of spherical equivalent (AnisoSE) and astigmatism (AnisoAST) and their relationships with refractive and axial measures were studied. Mean (±SD) of spherical equivalent (SE), AnisoSE and AnisoAST increased from baseline to follow-up end from -1.44 ± 0.57 D to -5.11 ± 2.23 D, from 0.28 ± 0.30 D to 0.68 ± 0.69 D and from 0.14 ± 0.18 D to 0.37 ± 0.36 D, respectively. Prevalence of AnioSE, ≥1 D, increased from 5% to 22.6% throughout follow-up. Higher AnisoSE was associated with SE in the less myopic eye at baseline and at follow-up 1, and with SE in the more myopic eye in follow-ups 2 and 3 in adulthood. At study end, AnisoSE was associated with the interocular difference in axial length (AL) (r = 0.612, p < 0.001) but not with the interocular difference in corneal refraction (CR) (r = -0.122, p = 0.266). In cases of low AnisoSE(≤1.00 D), the negative correlation between the real interocular differences (value of right eye minus value of left eye) in CR and AL (r = -0.427, p < 0.001) decreased the influence of the interocular difference in AL on AnisoSE, causing emmetropization in AnisoSE. The interocular difference in corneal astigmatism was the main factor associated with AnisoAST (r = 0.231, p = 0.020). No significant relationship was found between AnisoAST and level of SE. Anisometropia of the spherical equivalent (AnisoSE) increased along with the myopic progression and at study end was mainly associated with the interocular difference in AL. AnisoAST was mainly explained by the interocular difference in corneal astigmatism. In cases with low AnisoSE (≤1.0 D), the interrelationship between CR and AL decreased AnisoSE causing emmetropization in AnisoSE. © 2017 Acta Ophthalmologica Scandinavica Foundation. Published by John Wiley & Sons Ltd.

Effect of visual target blurring on accommodation under distance viewing

NASA Astrophysics Data System (ADS)

Iwata, Yo; Handa, Tomoya; Ishikawa, Hitoshi

2018-04-01

Abstract Purpose To examine the effect of visual target blurring on accommodation. Methods We evaluated the objective refraction values when the visual target (asterisk; 8°) was changed from the state without Gaussian blur (15 s) to the state with Gaussian blur adapted [0(without blur) → 10, 0 → 50, 0 → 100: 15 s each]. Results In Gaussian blur 10, when blurring of the target occurred, refraction value did not change significantly. In Gaussian blur 50 and 100, when blurring of the target occurred, the refraction value became significantly myopic. Conclusion Blurring of the distant visual target results in intervention of accommodation.

Myopia is Inversely Associated With the Prevalence of Diabetic Retinopathy in the South Korean Population.

PubMed

Chao, Daniel L; Lin, Shuai-Chun; Chen, Rebecca; Lin, Shan C

2016-12-01

Diabetic retinopathy is a major cause of irreversible vision loss. Recent studies have suggested that myopia may be negatively correlated with the prevalence of diabetic retinopathy. We sought to further investigate the association between refractive error and the likelihood of having diabetic retinopathy in a cross-sectional, population-based study of the South Korean population. Cross-sectional study. Data were included from right eyes of 13 424 participants who were 40 years and older with gradable fundus photographs of the Fourth and the Fifth Korea National Health and Nutrition Examination Survey. Diabetic retinopathy was graded using standard fundus photographs. Autorefraction data were collected to calculate spherical equivalent of refraction in diopters (D) and further classified into 4 groups: hyperopia (≥1.0 D), emmetropia (-0.99 D to 0.99 D), mild myopia (-1.0 D to -2.99 D), and moderate to high myopia (≤-3.0 D). Demographic, comorbidity, and health-related behavior information was obtained via interview. A multivariate model was used to evaluate the association between the diagnosis of any diabetic retinopathy and the refractive status. Mild myopia and moderate to high myopia groups were negatively associated with development of any diabetic retinopathy (odds ratio [OR] 0.42; 95% confidence interval [CI] 0.18-0.97 and OR 0.14; 95% CI 0.02-0.88, respectively). In addition, for every 1 D increase in spherical equivalent, there was a 30% increase of having diabetic retinopathy (OR 1.30; 95% CI, 1.08-1.58). Our results from a population-based study suggest that myopic status is associated with lower odds of having diabetic retinopathy in the South Korean population. Copyright © 2016 Elsevier Inc. All rights reserved.

Effectiveness of Hyperopic Defocus, Minimal Defocus, or Myopic Defocus in Competition with a Myopiagenic Stimulus in Tree Shrew Eyes

PubMed Central

Norton, Thomas T.; Siegwart, John T.; Amedo, Angela O.

2007-01-01

Purpose To examine the ability of hyperopic defocus, minimal defocus, and myopic defocus to compete against a myopiagenic −5-D lens in juvenile tree shrew eyes. Methods Juvenile tree shrews (n ≥ 5 per group), on a 14-hour lights-on/10-hour lights-off schedule, wore a monocular −5-D lens (a myopiagenic stimulus) over the right eye in their home cages for more than 23 hours per day for 11 days. For 45 minutes each day, the animals were restrained so that all visual stimuli were >1 m away. While viewing distance was controlled, the −5-D lens was removed and another lens was substituted with one of the following spherical powers: −5 D, −3 D (hyperopic defocus); plano (minimal defocus); or +3, +4, +5, +6, or +10 D (myopic defocus). Daily noncycloplegic autorefractor measures were made on most animals. After 11 days of treatment, cycloplegic refractive state and axial component dimensions were measured. Results Eyes with the substituted −5- or −3-D-lens developed significant myopia (mean ± SEM, −4.7 ± 0.3 and −3.1 ± 0.1 D, respectively) and appropriate vitreous chamber elongation. All animals with the substituted plano lens (minimal defocus) during the 45-minute period showed no axial elongation or myopia (the plano lens competed effectively against the −5-D lens). Variable results were found among animals that wore a plus lens (myopic defocus). In 11 of 20 eyes, a +3-, +4-, or +5-D lens competed effectively against the −5-D lens (treated eye <1.5 D myopic relative to its fellow control eye). In the other eyes (9/20) myopic defocus was ineffective in blocking compensation; the treated eye became more than 2.5 D myopic relative to the control eye. The +6- and +10-D substituted lenses were ineffective in blocking compensation in all cases. Conclusions When viewing distance was limited to objects >1 m away, viewing through a plano lens for 45 minutes (minimal defocus) consistently prevented the development of axial elongation and myopia in response to a myopiagenic −5-D lens. Myopic defocus prevented compensation in some but not all animals. Thus, myopic defocus is encoded by at least some tree shrew retinas as being different from hyperopic defocus, and myopic defocus can sometimes counteract the myopiagenic effect of the −5-D lens (hyperopic defocus). However, it appears that minimal defocus is a more consistent, strong antidote to a myopiagenic stimulus in this mammal closely related to primates. PMID:17065475

Difference of refraction values between standard autorefractometry and Plusoptix.

PubMed

Bogdănici, Camelia Margareta; Săndulache, Codrina Maria; Vasiliu, Rodica; Obadă, Otilia

2016-01-01

Aim: Comparison between the objective refraction measurement results determined with Topcon KR-8900 standard autorefractometer and Plusoptix A09 photo-refractometer in children. Material and methods: A prospective transversal study was performed in the Department of Ophthalmology of "Sf. Spiridon" Hospital in Iași on 90 eyes of 45 pediatric patients, with a mean age of 8,82 ± 3,52 years, examined with noncycloplegic measurements provided by Plusoptix A09 and cycloplegic and noncycloplegic measurements provided by Topcon KR-8900 standard autorefractometer. The clinical parameters compared were the following: spherical equivalent (SE), spherical and cylindrical values, and cylinder axis. Astigmatism was recorded and evaluated with the cylindrical value on minus after transposition. The statistical calculation was performed with paired t-tests and Pearson's correlation analysis. All the data were analyzed with SPSS statistical package 19 (SPSS for Windows, Chicago, IL). Results: Plusoptix A09 noncycloplegic values were relatively equal between the eyes, with slightly lower values compared to noncycloplegic auto refractometry. Mean (± SD) measurements provided by Plusoptix AO9 were the following: spherical power 1.11 ± 1.52, cylindrical power 0.80 ± 0.80, and spherical equivalent 0.71 ± 1.39. The noncycloplegic auto refractometer mean (± SD) measurements were spherical power 1.12 ± 1.63, cylindrical power 0.79 ± 0,77 and spherical equivalent 0.71 ± 1.58. The cycloplegic auto refractometer mean (± SD) measurements were spherical power 2.08 ± 1.95, cylindrical power 0,82 ± 0.85 and spherical equivalent 1.68 ± 1.87. 32% of the eyes were hyperopic, 2.67% were myopic, 65.33% had astigmatism, and 30% eyes had amblyopia. Conclusions: Noncycloplegic objective refraction values were similar with those determined by autorefractometry. Plusoptix had an important role in the ophthalmological screening, but did not detect higher refractive errors, justifying the cycloplegic autorefractometry.

Uncorrected and corrected refractive error experiences of Nepalese adults: a qualitative study.

PubMed

Kandel, Himal; Khadka, Jyoti; Shrestha, Mohan Krishna; Sharma, Sadhana; Neupane Kandel, Sandhya; Dhungana, Purushottam; Pradhan, Kishore; Nepal, Bhagavat P; Thapa, Suman; Pesudovs, Konrad

2018-04-01

The aim of this study was to explore the impact of corrected and uncorrected refractive error (URE) on Nepalese people's quality of life (QoL), and to compare the QoL status between refractive error subgroups. Participants were recruited from Tilganga Institute of Ophthalmology and Dhulikhel Hospital, Nepal. Semi-structured in-depth interviews were conducted with 101 people with refractive error. Thematic analysis was used with matrices produced to compare the occurrence of themes and categories across participants. Themes were identified using an inductive approach. Seven major themes emerged that determined refractive error-specific QoL: activity limitation, inconvenience, health concerns, psycho-social impact, economic impact, general and ocular comfort symptoms, and visual symptoms. Activity limitation, economic impact, and symptoms were the most important themes for the participants with URE, whereas inconvenience associated with wearing glasses was the most important issue in glasses wearers. Similarly, possibilities of having side effects or complications were the major concerns for participants wearing contact lens. In general, refractive surgery addressed socio-emotional impact of wearing glasses or contact lens. However, the surgery participants had concerns such as possibility of having to wear glasses again due to relapse of refractive error. Impact of refractive error on people's QoL is multifaceted. Significance of the identified themes varies by refractive error subgroups. Refractive correction may not always address QoL impact of URE but often add unique QoL issues. This study findings also provide content for developing an item-bank for quantitatively measuring refractive error-specific QoL in developing country setting.

Refractive errors among children, adolescents and adults attending eye clinics in Mexico.

PubMed

Gomez-Salazar, Francisco; Campos-Romero, Abraham; Gomez-Campaña, Humberto; Cruz-Zamudio, Cinthia; Chaidez-Felix, Mariano; Leon-Sicairos, Nidia; Velazquez-Roman, Jorge; Flores-Villaseñor, Hector; Muro-Amador, Secundino; Guadron-Llanos, Alma Marlene; Martinez-Garcia, Javier J; Murillo-Llanes, Joel; Sanchez-Cuen, Jaime; Llausas-Vargas, Alejando; Alapizco-Castro, Gerardo; Irineo-Cabrales, Ana; Graue-Hernandez, Enrique; Ramirez-Luquin, Tito; Canizalez-Roman, Adrian

2017-01-01

To assess the proportion of refractive errors in the Mexican population that visited primary care optometry clinics in fourteen states of Mexico. Refractive data from 676 856 patients aged 6 to 90y were collected from optometry clinics in fourteen states of Mexico between 2014 and 2015. The refractive errors were classified by the spherical equivalent (SE), as follows: sphere+½ cylinder. Myopia (SE>-0.50 D), hyperopia (SE>+0.50 D), emmetropia (-0.50≤SE≤+0.50), and astigmatism alone (cylinder≥-0.25 D). A negative cylinder was selected as a notation. The proportion (95% confidence interval) among all of the subjects was hyperopia 21.0% (20.9-21.0), emmetropia 40.7% (40.5-40.8), myopia 24.8% (24.7-24.9) and astigmatism alone 13.5% (13.4-13.5). Myopia was the most common refractive error and frequency seemed to increase among the young population (10 to 29 years old), however, hyperopia increased among the aging population (40 to 79 years old), and astigmatism alone showed a decreasing trend with age (6 to 90y; from 19.7% to 10.8%). There was a relationship between age and all refractive errors (approximately 60%, aged 50 and older). The proportion of any clinically important refractive error was higher in males (61.2%) than in females (58.3%; P <0.0001). From fourteen states that collected information, the proportion of refractive error showed variability in different geographical areas of Mexico. Myopia is the most common refractive error in the population studied. This study provides the first data on refractive error in Mexico. Further programs and studies must be developed to address the refractive errors needs of the Mexican population.

Refractive errors among children, adolescents and adults attending eye clinics in Mexico

PubMed Central

Gomez-Salazar, Francisco; Campos-Romero, Abraham; Gomez-Campaña, Humberto; Cruz-Zamudio, Cinthia; Chaidez-Felix, Mariano; Leon-Sicairos, Nidia; Velazquez-Roman, Jorge; Flores-Villaseñor, Hector; Muro-Amador, Secundino; Guadron-Llanos, Alma Marlene; Martinez-Garcia, Javier J.; Murillo-Llanes, Joel; Sanchez-Cuen, Jaime; Llausas-Vargas, Alejando; Alapizco-Castro, Gerardo; Irineo-Cabrales, Ana; Graue-Hernandez, Enrique; Ramirez-Luquin, Tito; Canizalez-Roman, Adrian

2017-01-01

AIM To assess the proportion of refractive errors in the Mexican population that visited primary care optometry clinics in fourteen states of Mexico. METHODS Refractive data from 676 856 patients aged 6 to 90y were collected from optometry clinics in fourteen states of Mexico between 2014 and 2015. The refractive errors were classified by the spherical equivalent (SE), as follows: sphere+½ cylinder. Myopia (SE>-0.50 D), hyperopia (SE>+0.50 D), emmetropia (-0.50≤SE≤+0.50), and astigmatism alone (cylinder≥-0.25 D). A negative cylinder was selected as a notation. RESULTS The proportion (95% confidence interval) among all of the subjects was hyperopia 21.0% (20.9-21.0), emmetropia 40.7% (40.5-40.8), myopia 24.8% (24.7-24.9) and astigmatism alone 13.5% (13.4-13.5). Myopia was the most common refractive error and frequency seemed to increase among the young population (10 to 29 years old), however, hyperopia increased among the aging population (40 to 79 years old), and astigmatism alone showed a decreasing trend with age (6 to 90y; from 19.7% to 10.8%). There was a relationship between age and all refractive errors (approximately 60%, aged 50 and older). The proportion of any clinically important refractive error was higher in males (61.2%) than in females (58.3%; P<0.0001). From fourteen states that collected information, the proportion of refractive error showed variability in different geographical areas of Mexico. CONCLUSION Myopia is the most common refractive error in the population studied. This study provides the first data on refractive error in Mexico. Further programs and studies must be developed to address the refractive errors needs of the Mexican population. PMID:28546940

Relative axial myopia in Egr-1 (ZENK) knockout mice.

PubMed

Schippert, Ruth; Burkhardt, Eva; Feldkaemper, Marita; Schaeffel, Frank

2007-01-01

Experiments in chickens have implicated the transcription factor ZENK (also known as Egr-1, NGFI-A, zif268, tis8, cef5, and Krox24) in the feedback mechanisms for visual control of axial eye growth and myopia development. ZENK is upregulated in retinal glucagon amacrine cells when axial eye growth is inhibited by positive spectacle lens wear and is downregulated when it is enhanced by negative spectacle lens wear, suggesting that ZENK may be linked to an inhibitory signal for axial eye growth. This study was undertaken to determine whether a Egr-1(-/-) knockout mouse mutant, lacking ZENK completely, has longer eyes and more myopic refraction, than do Egr-1(+/)(-) heterozygous and Egr-1(+/+) wild-type mice with near-identical genetic backgrounds. Eye growth and refractive development were tracked from day P28 to P98. Corneal radius of curvature was measured with infrared photokeratometry, refractive state with infrared photoretinoscopy, and ocular dimensions with low-coherence interferometry. As a functional vision test, grating acuity was determined in an automated optomotor task. The abundance of ZENK protein in the retina was quantified by immunohistochemistry. Egr-1 knockout mice had longer eyes and a relative myopic shift in refraction, with additional minor effects on anterior chamber depth and corneal radius of curvature. Paraxial schematic eye modeling suggested changes in the optics of the crystalline lens as well. With increasing age, the differences between mutant and wild-type mice declined, although the differences in refraction persisted over the observation period. Grating acuity was not affected by the lack of the Egr-1 protein during development. Although it has been shown that different mouse strains may have differently large eyes, the present study shows that a specific gene knockout can produce relative myopia, compared with the wild-type with near-identical genetic background. Further experiments are needed to determine whether the observed effects of Egr-1 deletion are due to changes in function within the retina or other ocular tissues or to changes of function in other systems that may affect ocular growth from outside the eye.

Refractive Errors Affect the Vividness of Visual Mental Images

PubMed Central

Palermo, Liana; Nori, Raffaella; Piccardi, Laura; Zeri, Fabrizio; Babino, Antonio; Giusberti, Fiorella; Guariglia, Cecilia

2013-01-01

The hypothesis that visual perception and mental imagery are equivalent has never been explored in individuals with vision defects not preventing the visual perception of the world, such as refractive errors. Refractive error (i.e., myopia, hyperopia or astigmatism) is a condition where the refracting system of the eye fails to focus objects sharply on the retina. As a consequence refractive errors cause blurred vision. We subdivided 84 individuals according to their spherical equivalent refraction into Emmetropes (control individuals without refractive errors) and Ametropes (individuals with refractive errors). Participants performed a vividness task and completed a questionnaire that explored their cognitive style of thinking before their vision was checked by an ophthalmologist. Although results showed that Ametropes had less vivid mental images than Emmetropes this did not affect the development of their cognitive style of thinking; in fact, Ametropes were able to use both verbal and visual strategies to acquire and retrieve information. Present data are consistent with the hypothesis of equivalence between imagery and perception. PMID:23755186

Refractive errors affect the vividness of visual mental images.

PubMed

Palermo, Liana; Nori, Raffaella; Piccardi, Laura; Zeri, Fabrizio; Babino, Antonio; Giusberti, Fiorella; Guariglia, Cecilia

2013-01-01

The hypothesis that visual perception and mental imagery are equivalent has never been explored in individuals with vision defects not preventing the visual perception of the world, such as refractive errors. Refractive error (i.e., myopia, hyperopia or astigmatism) is a condition where the refracting system of the eye fails to focus objects sharply on the retina. As a consequence refractive errors cause blurred vision. We subdivided 84 individuals according to their spherical equivalent refraction into Emmetropes (control individuals without refractive errors) and Ametropes (individuals with refractive errors). Participants performed a vividness task and completed a questionnaire that explored their cognitive style of thinking before their vision was checked by an ophthalmologist. Although results showed that Ametropes had less vivid mental images than Emmetropes this did not affect the development of their cognitive style of thinking; in fact, Ametropes were able to use both verbal and visual strategies to acquire and retrieve information. Present data are consistent with the hypothesis of equivalence between imagery and perception.

Uncorrected refractive errors.

PubMed

Naidoo, Kovin S; Jaggernath, Jyoti

2012-01-01

Global estimates indicate that more than 2.3 billion people in the world suffer from poor vision due to refractive error; of which 670 million people are considered visually impaired because they do not have access to corrective treatment. Refractive errors, if uncorrected, results in an impaired quality of life for millions of people worldwide, irrespective of their age, sex and ethnicity. Over the past decade, a series of studies using a survey methodology, referred to as Refractive Error Study in Children (RESC), were performed in populations with different ethnic origins and cultural settings. These studies confirmed that the prevalence of uncorrected refractive errors is considerably high for children in low-and-middle-income countries. Furthermore, uncorrected refractive error has been noted to have extensive social and economic impacts, such as limiting educational and employment opportunities of economically active persons, healthy individuals and communities. The key public health challenges presented by uncorrected refractive errors, the leading cause of vision impairment across the world, require urgent attention. To address these issues, it is critical to focus on the development of human resources and sustainable methods of service delivery. This paper discusses three core pillars to addressing the challenges posed by uncorrected refractive errors: Human Resource (HR) Development, Service Development and Social Entrepreneurship.

Refractive errors and schizophrenia.

PubMed

Caspi, Asaf; Vishne, Tali; Reichenberg, Abraham; Weiser, Mark; Dishon, Ayelet; Lubin, Gadi; Shmushkevitz, Motti; Mandel, Yossi; Noy, Shlomo; Davidson, Michael

2009-02-01

Refractive errors (myopia, hyperopia and amblyopia), like schizophrenia, have a strong genetic cause, and dopamine has been proposed as a potential mediator in their pathophysiology. The present study explored the association between refractive errors in adolescence and schizophrenia, and the potential familiality of this association. The Israeli Draft Board carries a mandatory standardized visual accuracy assessment. 678,674 males consecutively assessed by the Draft Board and found to be psychiatrically healthy at age 17 were followed for psychiatric hospitalization with schizophrenia using the Israeli National Psychiatric Hospitalization Case Registry. Sib-ships were also identified within the cohort. There was a negative association between refractive errors and later hospitalization for schizophrenia. Future male schizophrenia patients were two times less likely to have refractive errors compared with never-hospitalized individuals, controlling for intelligence, years of education and socioeconomic status [adjusted Hazard Ratio=.55; 95% confidence interval .35-.85]. The non-schizophrenic male siblings of schizophrenia patients also had lower prevalence of refractive errors compared to never-hospitalized individuals. Presence of refractive errors in adolescence is related to lower risk for schizophrenia. The familiality of this association suggests that refractive errors may be associated with the genetic liability to schizophrenia.

Myopia and personality: the genes in myopia (GEM) personality study.

PubMed

van de Berg, Robert; Dirani, Mohamed; Chen, Christine Y; Haslam, Nicholas; Baird, Paul N

2008-03-01

A long-held view among the medical and broader community is that people who are short-sighted (myopic persons) have distinctive personality characteristics such as introversion and conscientiousness. However, existing research on this question is flawed, and its findings are inconsistent. The authors therefore aimed to determine whether myopia and personality are associated. The authors examined twins recruited through the Australian Twin Registry and a clinical-based family sample through a proband from a Melbourne Excimer Laser Clinic. There was no relation between family members and twins recruited in our study. Each individual underwent a full eye examination, completed a standard medical and general questionnaire, and was administered a five-factor model International Personality Item Pool (IPIP) inventory (Openness, Conscientiousness, Extroversion, Agreeableness, Neuroticism). Myopia was defined as worse than or equal to -0.50 (DS) spherical equivalent in the eye with the least refractive error. Data from 633 individual twins aged 18 to 83 years (mean, 53.04 years) and 278 family members aged 11 to 90 years (mean, 49.84 years) were analyzed. Prevalence of myopia was 35.7% for twins and 47.6% for family members. Mean spherical equivalent was +0.13 DS (95% CI, +/-0.16) for twins and -1.13 DS (95% CI, +/-0.25) for family members. Correlation and regression results for personality for both sample cohorts after multivariate analysis did not support the view that myopic persons are introverted or conscientious; however, there was a significant but small association between myopia and Agreeableness (r = 0.08, P < 0.05). In multivariate analysis with age, sex, education, and the five personality factors entered as predictors, Openness was the only significant personality predictor of myopia in both samples. This is the first multivariate study to assess links between personality and myopia using the IPIP. The long-held view that myopic persons are introverted and conscientious may reflect intelligence-related stereotypes rather than real correlations. Furthermore, the predictive characteristic of intellect, subsumed in Openness, appeared to be representative of a previously reported link between intellective abilities (IQ) and myopia rather than personality and myopia.

[Refractive errors in patients with cerebral palsy].

PubMed

Mrugacz, Małgorzata; Bandzul, Krzysztof; Kułak, Wojciech; Poppe, Ewa; Jurowski, Piotr

2013-04-01

Ocular changes are common in patients with cerebral palsy (CP) and they exist in about 50% of cases. The most common are refractive errors and strabismus disease. The aim of the paper was to estimate the relativeness between refractive errors and neurological pathologies in patients with selected types of CP. MATERIAL AND METHODS. The subject of the analysis was showing refractive errors in patients within two groups of CP: diplegia spastica and tetraparesis, with nervous system pathologies taken into account. Results. This study was proven some correlations between refractive errors and type of CP and severity of the CP classified in GMFCS scale. Refractive errors were more common in patients with tetraparesis than with diplegia spastica. In the group with diplegia spastica more common were myopia and astigmatism, however in tetraparesis - hyperopia.

Integration of Defocus by Dual Power Fresnel Lenses Inhibits Myopia in the Mammalian Eye

PubMed Central

McFadden, Sally A.; Tse, Dennis Y.; Bowrey, Hannah E.; Leotta, Amelia J.; Lam, Carly S.; Wildsoet, Christine F.; To, Chi-Ho

2014-01-01

Purpose. Eye growth compensates in opposite directions to single vision (SV) negative and positive lenses. We evaluated the response of the guinea pig eye to Fresnel-type lenses incorporating two different powers. Methods. A total of 114 guinea pigs (10 groups with 9–14 in each) wore a lens over one eye and interocular differences in refractive error and ocular dimensions were measured in each of three experiments. First, the effects of three Fresnel designs with various diopter (D) combinations (−5D/0D; +5D/0D or −5D/+5D dual power) were compared to three SV lenses (−5D, +5D, or 0D). Second, the ratio of −5D and +5D power in a Fresnel lens was varied (50:50 compared with 60:40). Third, myopia was induced by 4 days of exposure to a SV −5D lens, which was then exchanged for a Fresnel lens (−5D/+5D) or one of two SV lenses (+5D or −5D) and ocular parameters tracked for a further 3 weeks. Results. Dual power lenses induced an intermediate response between that to the two constituent powers (lenses +5D, +5D/0D, 0D, −5D/+5D, −5D/0D and −5D induced +2.1 D, +0.7 D, +0.1 D, −0.3 D, −1.6 D and −5.1 D in mean intraocular differences in refractive error, respectively), and changing the ratio of powers induced responses equal to their weighted average. In already myopic animals, continued treatment with SV negative lenses increased their myopia (from −3.3 D to −4.2 D), while switching to SV positive lenses or −5D/+5D Fresnel lenses reduced their myopia (by 2.9 D and 2.3 D, respectively). Conclusions. The mammalian eye integrates competing defocus to guide its refractive development and eye growth. Fresnel lenses, incorporating positive or plano power with negative power, can slow ocular growth, suggesting that such designs may control myopia progression in humans. PMID:24398103

Integration of defocus by dual power Fresnel lenses inhibits myopia in the mammalian eye.

PubMed

McFadden, Sally A; Tse, Dennis Y; Bowrey, Hannah E; Leotta, Amelia J; Lam, Carly S; Wildsoet, Christine F; To, Chi-Ho

2014-02-14

Eye growth compensates in opposite directions to single vision (SV) negative and positive lenses. We evaluated the response of the guinea pig eye to Fresnel-type lenses incorporating two different powers. A total of 114 guinea pigs (10 groups with 9-14 in each) wore a lens over one eye and interocular differences in refractive error and ocular dimensions were measured in each of three experiments. First, the effects of three Fresnel designs with various diopter (D) combinations (-5D/0D; +5D/0D or -5D/+5D dual power) were compared to three SV lenses (-5D, +5D, or 0D). Second, the ratio of -5D and +5D power in a Fresnel lens was varied (50:50 compared with 60:40). Third, myopia was induced by 4 days of exposure to a SV -5D lens, which was then exchanged for a Fresnel lens (-5D/+5D) or one of two SV lenses (+5D or -5D) and ocular parameters tracked for a further 3 weeks. Dual power lenses induced an intermediate response between that to the two constituent powers (lenses +5D, +5D/0D, 0D, -5D/+5D, -5D/0D and -5D induced +2.1 D, +0.7 D, +0.1 D, -0.3 D, -1.6 D and -5.1 D in mean intraocular differences in refractive error, respectively), and changing the ratio of powers induced responses equal to their weighted average. In already myopic animals, continued treatment with SV negative lenses increased their myopia (from -3.3 D to -4.2 D), while switching to SV positive lenses or -5D/+5D Fresnel lenses reduced their myopia (by 2.9 D and 2.3 D, respectively). The mammalian eye integrates competing defocus to guide its refractive development and eye growth. Fresnel lenses, incorporating positive or plano power with negative power, can slow ocular growth, suggesting that such designs may control myopia progression in humans.

Intraocular lens power calculation following LASIK: determination of the new effective index of refraction.

PubMed

Jarade, Elias F; Abi Nader, Françoise C; Tabbara, Khalid F

2006-01-01

To determine the new corneal effective index of refraction (rN) following LASIK to be used for accurate keratometry reading (K-reading). A total of 332 eyes that underwent myopic LASIK were divided into two groups (group A [n = 137] and group B [n = 1951). In each group, patients were divided into four subgroups according to the amount of spherical equivalent refraction of myopic LASIK ablation (subgroup 1 [< -4.0 D], subgroup 2 [-4.0 to < -8.0 D], subgroup 3 [-8.0 to -12.0 D], and subgroup 4 [> -12.0 D]). In each subgroup of group A, K-reading was measured by the clinical history method and the new corneal effective index (rN) was determined using paraxial formula: (K-reading = (rN-1)/Ra), where Ra is the radius of curvature of the anterior corneal surface. In group B, the anterior radius of curvature of the cornea was determined by automated K-reading, and K-reading was measured in each subgroup using the new effective index in paraxial formula, clinical history method, and automated K-reading. In group A, the new effective index of refraction was 1.3355, 1.3286, 1.3237, and 1.3172 in the four subgroups, respectively. In group B, the mean K-reading measurements using rN in paraxial formula, clinical history method, and automated K-reading were: 40.33 +/- 1.68 D, 40.33 +/- 1.67 D, and 40.54 +/- 1.69 D, respectively, in subgroup 1; 37.96 +/- 1.26 D, 38.03 +/- 1.38 D, and 38.98 +/- 1.28 D, respectively, in subgroup 2; 35.77 +/- 1.75 D, 35.84 +/- 1.85 D, and 37.29 +/- 1.83 D, respectively, in subgroup 3; and 34.03 +/- 1.49 D, 34.15 +/- 1.84 D, and 36.21 +/- 1.59 D, respectively, in subgroup 4. In all subgroups of group B, the results of K-reading obtained using the new effective index of refraction were statistically similar to the results obtained by clinical history method (P > .05). Automated K-reading statistically overestimated the K-reading values in subgroups 2, 3, and 4 of group B (P < .001). The use of the new corneal effective index of refraction allows for an accurate derivation of K-reading from the anterior radius of curvature.

A survey of the prevalence of refractive errors among children in lower primary schools in Kampala district.

PubMed

Kawuma, Medi; Mayeku, Robert

2002-08-01

Refractive errors are a known cause of visual impairment and may cause blindness worldwide. In children, refractive errors may prevent those afflicted from progressing with their studies. In Uganda, like in many developing countries, there is no established vision-screening programme for children on commencement of school, such that those with early onset of such errors will have many years of poor vision. Over all, there is limited information on refractive errors among children in Africa. To determine the prevalence of refractive errors among school children attending lower primary in Kampala district; the frequency of the various types of refractive errors, and their relationship to sexuality and ethnicity. A cross-sectional descriptive study. Kampala district, Uganda A total of 623 children aged between 6 and 9 years had a visual acuity testing done at school using the same protocol; of these 301 (48.3%) were boys and 322 (51.7%) girls. Seventy-three children had a significant refractive error of +/-0.50 or worse in one or both eyes, giving a prevalence of 11.6% and the commonest single refractive error was astigmatism, which accounted for 52% of all errors. This was followed by hypermetropia, and myopia was the least common. Significant refractive errors occur among primary school children aged 6 to 9 years at a prevalence of approximately 12%. Therefore, there is a need to have regular and simple vision testing in primary school children at least at the commencement of school so as to defect those who may suffer from these disabilities.

Headache and refractive errors in children.

PubMed

Roth, Zachary; Pandolfo, Katie R; Simon, John; Zobal-Ratner, Jitka

2014-01-01

To investigate the association between uncorrected or miscorrected refractive errors in children and headache, and to determine whether correction of refractive errors contributes to headache resolution. Results of ophthalmic examination, including refractive error, were recorded at initial visit for headache. If resolution of headache on subsequent visits was not documented, a telephone call was placed to their caregivers to inquire whether headache had resolved. Of the 158 patients, 75.3% had normal or unchanged eye examinations, including refractions.Follow-up data were available for 110 patients. Among those, 32 received new or changed spectacle correction and 78 did not require a change in refraction.Headaches improved in 76.4% of all patients, whether with (71.9%) or without (78.2%) a change in refractive correction. The difference between these two groups was not statistically significant (P = .38). Headaches in children usually do not appear to be caused by ophthalmic disease, including refractive error. The prognosis for improvement is favorable, regardless of whether refractive correction is required. Copyright 2014, SLACK Incorporated.

Refractive Errors

MedlinePlus

... and lens of your eye helps you focus. Refractive errors are vision problems that happen when the shape ... cornea, or aging of the lens. Four common refractive errors are Myopia, or nearsightedness - clear vision close up ...

Education-Related Parameters in High Myopia: Adults versus School Children

PubMed Central

Xu, Liang; Wang, Ya Xing; Bi, Hong Sheng; Wu, Jian Feng; Jiang, Wen Jun; Nangia, Vinay; Sinha, Ajit; Zhu, Dan; Tao, Yong; Guo, Yin; You, Qi Sheng; Wu, Li Juan; Tao, Li Xin; Guo, Xiu Hua; Ohno-Matsui, Kyoko; Panda-Jonas, Songhomitra

2016-01-01

Purpose Since high myopia in the younger generation may differ etiologically from high myopia in older generations, we examined whether education-related parameters differ between high myopia in today´s school children and high pathological myopia in today´s elderly generation. Methods The investigation included the adult populations of the population-based Beijing Eye Study (BES) (3468 adults;mean age:64.6±9.8years;range:50–93years) and Central India Eye and Medical Study (CIEMS) (4711 adults;age:49.±13.2years;range:30–100years), and the children and teenager populations of the Shandong Children Eye Study (SCES) (6026 children;age:9.7±3.3years;range:4–18years;cycloplegic refractometry), Gobi Desert Children Eye Study (1565;age:11.9±3.5years;range:6–21 years;cycloplegic refractometry), Beijing Pediatric Eye Study (681 children;age:7.7±1.6years;range:5–13 years;non-cycloplegic refractometry,calculation of axial length to corneal curvature radius ratio), Beijing Children Eye Study (15066 children;age:13.2±3.4years;range:7–18years;non-cycloplegic refractometry), Beijing High School Teenager Eye Study (4677 children;age:16.9±0.7years;range:16–18years;non-cycloplegic refractometry). Results In the BES and CIEMS, educational level did not differ significantly between, or was significantly lower in the highly myopic group (myopic refractive error ≥6 diopters) than in the non-highly myopic group. In all non-adult study populations, higher prevalence of high myopia was significantly associated with higher degree of education related parameters such as attendance of high-level schools, and more time spent for indoors near work versus time spent outdoors. Conclusions Comparing associations of old or genetic high myopia in adults with new or acquired high myopia in school children revealed that education-related parameters did not show a clear association with old or genetic high myopia, while in contrast, new high myopia showed strong associations with education. It confirms previous studies that the two forms of high myopia not only differed in age of onset, but also in associations with education as well. The data support the notion of two types of high myopia. Future studies may assess whether the risk of pathologic myopic maculopathy and high myopia associated open-angle glaucoma differs between both types of high myopia. PMID:27152764

Can partial coherence interferometry be used to determine retinal shape?

PubMed

Atchison, David A; Charman, W Neil

2011-05-01

To determine likely errors in estimating retinal shape using partial coherence interferometric instruments when no allowance is made for optical distortion. Errors were estimated using Gullstrand no. 1 schematic eye and variants which included a 10 diopter (D) axial myopic eye, an emmetropic eye with a gradient-index lens, and a 10.9 D accommodating eye with a gradient-index lens. Performance was simulated for two commercial instruments, the IOLMaster (Carl Zeiss Meditec) and the Lenstar LS 900 (Haag-Streit AG). The incident beam was directed toward either the center of curvature of the anterior cornea (corneal-direction method) or the center of the entrance pupil (pupil-direction method). Simple trigonometry was used with the corneal intercept and the incident beam angle to estimate retinal contour. Conics were fitted to the estimated contours. The pupil-direction method gave estimates of retinal contour that were much too flat. The cornea-direction method gave similar results for IOLMaster and Lenstar approaches. The steepness of the retinal contour was slightly overestimated, the exact effects varying with the refractive error, gradient index, and accommodation. These theoretical results suggest that, for field angles ≤30°, partial coherence interferometric instruments are of use in estimating retinal shape by the corneal-direction method with the assumptions of a regular retinal shape and no optical distortion. It may be possible to improve on these estimates out to larger field angles by using optical modeling to correct for distortion.

Population-based assessment of sensitivity and specificity of a pinhole for detection of significant refractive errors in the community.

PubMed

Marmamula, Srinivas; Keeffe, Jill E; Narsaiah, Saggam; Khanna, Rohit C; Rao, Gullapalli N

2014-11-01

Measurements of refractive errors through subjective or automated refraction are not always possible in rapid assessment studies and community vision screening programs; however, measurements of vision with habitual correction and with a pinhole can easily be made. Although improvements in vision with a pinhole are assumed to mean that a refractive error is present, no studies have investigated the magnitude of improvement in vision with pinhole that is predictive of refractive error. The aim was to measure the sensitivity and specificity of 'vision improvement with pinhole' in predicting the presence of refractive error in a community setting. Vision and vision with pinhole were measured using a logMAR chart for 488 of 582 individuals aged 15 to 50 years. Refractive errors were measured using non-cycloplegic autorefraction and subjective refraction. The presence of refractive error was defined using spherical equivalent refraction (SER) at two levels: SER greater than ± 0.50 D sphere (DS) and SER greater than ±1.00 DS. Three definitions for significant improvement in vision with a pinhole were used: 1. Presenting vision less than 6/12 and improving to 6/12 or better, 2. Improvement in vision of more than one logMAR line and 3. Improvement in vision of more than two logMAR lines. For refractive error defined as spherical equivalent refraction greater than ± 0.50 DS, the sensitivities and specificities for the pinhole test predicting the presence of refractive error were 83.9 per cent (95% CI: 74.5 to 90.9) and 98.8 per cent (95% CI: 97.1 to 99.6), respectively for definition 1. Definition 2 had a sensitivity 89.7 per cent (95% CI: 81.3 to 95.2) and specificity 88.0 per cent (95% CI: 4.4 to 91.0). Definition 3 had a sensitivity of 75.9 per cent (95% CI: 65.5 to 84.4) and specificity of 97.8 per cent (95% CI: 95.8 to 99.0). Similar results were found with spherical equivalent refraction greater than ±1.00 DS, when tested against the three pinhole-based definitions. Refractive error definitions based on improvement in vision with the pinhole shows good sensitivity and specificity at predicting the presence of significant refractive errors. These definitions can be used in rapid assessment surveys and community-based vision screenings. © 2014 The Authors. Clinical and Experimental Optometry © 2014 Optometrists Association Australia.

A clinic-based study of refractive errors, strabismus, and amblyopia in pediatric age-group.

PubMed

Al-Tamimi, Elham R; Shakeel, Ayisha; Yassin, Sanaa A; Ali, Syed I; Khan, Umar A

2015-01-01

The purpose of this cross-sectional observational study was to determine the distribution and patterns of refractive errors, strabismus, and amblyopia in children seen at a pediatric eye care. The study was conducted in a Private Hospital in Dammam, Kingdom of Saudi Arabia, from March to July 2013. During this period, a total of 1350 children, aged 1-15 years were seen at this Center's Pediatric Ophthalmology Unit. All the children underwent complete ophthalmic examination with cycloplegic refraction. Refractive errors accounted for 44.4% of the cases, the predominant refractive error being hypermetropia which represented 83%. Strabismus and amblyopia were present in 38% and 9.1% of children, respectively. In this clinic-based study, the focus was on the frequency of refractive errors, strabismus, and amblyopia which were considerably high. Hypermetropia was the predominant refractive error in contrast to other studies in which myopia was more common. This could be attributed to the criteria for sample selection since it was clinic-based rather than a population-based study. However, it is important to promote public education on the significance of early detection of refractive errors, and have periodic screening in schools.

Uncorrected refractive errors

PubMed Central

Naidoo, Kovin S; Jaggernath, Jyoti

2012-01-01

Global estimates indicate that more than 2.3 billion people in the world suffer from poor vision due to refractive error; of which 670 million people are considered visually impaired because they do not have access to corrective treatment. Refractive errors, if uncorrected, results in an impaired quality of life for millions of people worldwide, irrespective of their age, sex and ethnicity. Over the past decade, a series of studies using a survey methodology, referred to as Refractive Error Study in Children (RESC), were performed in populations with different ethnic origins and cultural settings. These studies confirmed that the prevalence of uncorrected refractive errors is considerably high for children in low-and-middle-income countries. Furthermore, uncorrected refractive error has been noted to have extensive social and economic impacts, such as limiting educational and employment opportunities of economically active persons, healthy individuals and communities. The key public health challenges presented by uncorrected refractive errors, the leading cause of vision impairment across the world, require urgent attention. To address these issues, it is critical to focus on the development of human resources and sustainable methods of service delivery. This paper discusses three core pillars to addressing the challenges posed by uncorrected refractive errors: Human Resource (HR) Development, Service Development and Social Entrepreneurship. PMID:22944755

Generalized ray tracing method for the calculation of the peripheral refraction induced by an ophthalmic lens

NASA Astrophysics Data System (ADS)

Rojo, Pilar; Royo, Santiago; Caum, Jesus; Ramírez, Jorge; Madariaga, Ines

2015-02-01

Peripheral refraction, the refractive error present outside the main direction of gaze, has lately attracted interest due to its alleged relationship with the progression of myopia. The ray tracing procedures involved in its calculation need to follow an approach different from those used in conventional ophthalmic lens design, where refractive errors are compensated only in the main direction of gaze. We present a methodology for the evaluation of the peripheral refractive error in ophthalmic lenses, adapting the conventional generalized ray tracing approach to the requirements of the evaluation of peripheral refraction. The nodal point of the eye and a retinal conjugate surface will be used to evaluate the three-dimensional distribution of refractive error around the fovea. The proposed approach enables us to calculate the three-dimensional peripheral refraction induced by any ophthalmic lens at any direction of gaze and to personalize the lens design to the requirements of the user. The complete evaluation process for a given user prescribed with a -5.76D ophthalmic lens for foveal vision is detailed, and comparative results obtained when the geometry of the lens is modified and when the central refractive error is over- or undercorrected. The methodology is also applied for an emmetropic eye to show its application for refractive errors other than myopia.

Comparisons of refractive errors between twins and singletons in Chinese school-age samples.

PubMed

Hur, Yoon-Mi; Zheng, Yingfeng; Huang, Wenyong; Ding, Xiaohu; He, Mingguang

2009-02-01

Studies have reported that refractive errors are associated with premature births. As twins have higher prevalence of prematurity than singletons, it is important to assess similarity of the prevalence of refractive errors in twins and singletons for proper interpretations and generalizations of the findings from twin studies. We compared refractive errors and diopter hours between 561 pairs of twins and 3757 singletons who are representative of school-age children (7-15 years) residing in an urban area of southern China. We found that the means and variances of the continuous measurement of spherical equivalent refractive error and diopter hours were not significantly different between twins and singletons. Although the prevalence of myopia was comparable between twins and singletons, that of hyperopia and astigmatism was slightly but significantly higher in twins than in singletons. These results are inconsistent with those of adult studies that showed no differences in refractive errors between twins and singletons. Given that the sample size of twins is relatively small and that this study is the first to demonstrate minor differences in refractive errors between twins and singletons, future replications are necessary to determine whether the slightly higher prevalence of refractive errors in twins than in singletons found in this study was due to a sampling error or to the developmental delay often observed in twins in childhood.

The GEnes in Myopia (GEM) study in understanding the aetiology of refractive errors.

PubMed

Baird, Paul N; Schäche, Maria; Dirani, Mohamed

2010-11-01

Refractive errors represent the leading cause of correctable vision impairment and blindness in the world with an estimated 2 billion people affected. Refractive error refers to a group of refractive conditions including hypermetropia, myopia, astigmatism and presbyopia but relatively little is known about their aetiology. In order to explore the potential role of genetic determinants in refractive error the "GEnes in Myopia (GEM) study" was established in 2004. The findings that have resulted from this study have not only provided greater insight into the role of genes and other factors involved in myopia but have also gone some way to uncovering the aetiology of other refractive errors. This review will describe some of the major findings of the GEM study and their relative contribution to the literature, illuminate where the deficiencies are in our understanding of the development of refractive errors and how we will advance this field in the future. Copyright © 2010 Elsevier Ltd. All rights reserved.

Refractive errors among students occupying rooms lighted with incandescent or fluorescent lamps.

PubMed

Czepita, Damian; Gosławski, Wojciech; Mojsa, Artur

2004-01-01

The purpose of the study was to determine whether the development of refractive errors could be associated with exposure to light emitted by incandescent or fluorescent lamps. 3636 students were examined (1638 boys and 1998 girls, aged 6-18 years, mean age 12.1, SD 3.4). The examination included retinoscopy with cycloplegia. Myopia was defined as refractive error < or = -0.5 D, hyperopia as refractive error > or = +1.5 D, astigmatism as refractive error > 0.5 DC. Anisometropia was diagnosed when the difference in the refraction of both eyes was > 1.0 D. The children and their parents completed a questionnaire on exposure to light at home. Data were analyzed statistically with the chi2 test. P values of less than 0.05 were considered statistically significant. It was found that the use of fluorescent lamps was associated with an increase in the occurrence of hyperopia (P < 0.01). There was no association between sleeping with the light turned on and prevalence of refractive errors.

Double-pass measurement of human eye aberrations: limitations and practical realization

NASA Astrophysics Data System (ADS)

Letfullin, Renat R.; Belyakov, Alexey I.; Cherezova, Tatyana Y.; Kudryashov, Alexis V.

2004-11-01

The problem of correct eye aberrations measurement is very important with the rising widespread of a surgical procedure for reducing refractive error in the eye, so called, LASIK (laser-assisted in situ keratomileusis). The double-pass technique commonly used for measuring aberrations of a human eye involves some uncertainties. One of them is loosing the information about odd human eye aberrations. We report about investigations of the applicability limit of the double-pass measurements depending upon the aberrations status introduced by human eye and actual size of the entrance pupil. We evaluate the double-pass effects for various aberrations and different pupil diameters. It is shown that for small pupils the double-pass effects are negligible. The testing and alignment of aberrometer was performed using the schematic eye, developed in our lab. We also introduced a model of human eye based on bimorph flexible mirror. We perform calculations to demonstrate that our schematic eye is capable of reproducing spatial-temporal statistics of aberrations of living eye with normal vision or even myopic or hypermetropic or with high aberrations ones.

PREVALENCE OF UNCORRECTED REFRACTIVE ERRORS IN ADULTS AGED 30 YEARS AND ABOVE IN A RURAL POPULATION IN PAKISTAN.

PubMed

Abdullah, Ayesha S; Jadoon, Milhammad Zahid; Akram, Mohammad; Awan, Zahid Hussain; Azam, Mohammad; Safdar, Mohammad; Nigar, Mohammad

2015-01-01

Uncorrected refractive errors are a leading cause of visual disability globally. This population-based study was done to estimate the prevalence of uncorrected refractive errors in adults aged 30 years and above of village Pawakah, Khyber Pakhtunkhwa (KPK), Pakistan. It was a cross-sectional survey in which 1000 individuals were included randomly. All the individuals were screened for uncorrected refractive errors and those whose visual acuity (VA) was found to be less than 6/6 were refracted. In whom refraction was found to be unsatisfactory (i.e., a best corrected visual acuity of <6/6) further examination was done to establish the cause for the subnormal vision. A total of 917 subjects participated in the survey (response rate 92%). The prevalence of uncorrected refractive errors was found to be 23.97% among males and 20% among females. The prevalence of visually disabling refractive errors was 6.89% in males and 5.71% in females. The prevalence was seen to increase with age, with maximum prevalence in 51-60 years age group. Hypermetropia (10.14%) was found to be the commonest refractive error followed by Myopia (6.00%) and Astigmatism (5.6%). The prevalence of Presbyopia was 57.5% (60.45% in males and 55.23% in females). Poor affordability was the commonest barrier to the use of spectacles, followed by unawareness. Cataract was the commonest reason for impaired vision after refractive correction. The prevalence of blindness was 1.96% (1.53% in males and 2.28% in females) in this community with cataract as the commonest cause. Despite being the most easily avoidable cause of subnormal vision uncorrected refractive errors still account for a major proportion of the burden of decreased vision in this area. Effective measures for the screening and affordable correction of uncorrected refractive errors need to be incorpora'ted into the health care delivery system.

Prevalence and pattern of refractive errors among primary school children in Al Hassa , Saudi Arabia.

PubMed

Al Wadaani, Fahd Abdullah; Amin, Tarek Tawfik; Ali, Ayub; Khan, Atuar Rahman

2012-11-11

Some 12.8 million in the age group 5-15 years are visually impaired from uncorrected or inadequately corrected refractive errors. In Saudi Arabia, the size of this public health problem is not well defined especially among primary schoolchildren. The purpose of this cross-sectional study was to assess the prevalence and pattern of refractive errors among primary school children in Al Hassa, Saudi Arabia.  A total of 2246 Saudi primary school children aged 6 to 14 years of both genders were selected using multistage sampling method form 30 primary schools located in the three different areas of Al Hassa. School children were interviewed to collect demographics and vision data using a special data collection form followed by screening for refractive errors by trained optometrists within the school premises using a standardized protocol. Assessment of visual acuity and ocular motility evaluation were carried out and cover-uncover test was performed. Children detected with defective vision were referred for further examination employing subjective refraction with auto refractometer and objective refraction using streak retinoscopy after 1% cyclopentolate. Of the screened school children (N=2002), the overall prevalence of refractive errors was 13.7% (n=274), higher among females (Odds ratio, OR=1.39, P=0.012) and significantly more among students of rural residence (OR=2.40, P=0.001). The prevalence of refractive errors was disproportionately more among those aged 12-14 years (OR=9.02, P=0.001). Only 9.4% of students with poor vision were wore spectacles for correction. Myopia was the most commonly encountered refractive error among both genders (65.7% of the total errors encountered). Uncorrected refractive errors affected a sizable portion of primary school children in Al Hassa, Saudi Arabia. Primary schoolchildren especially females, rural and older children represents high risk group for refractive errors for which the included children were unaware.

Prevalence and Pattern of Refractive Errors among Primary School Children in Al Hassa, Saudi Arabia

PubMed Central

Wadaani, Fahd Abdullah Al; Amin, Tarek Tawfik; Ali, Ayub; Khan, Ataur Rahman

2013-01-01

Some 12.8 million in the age group 5–15 years are visually impaired from uncorrected or inadequately corrected refractive errors. In Saudi Arabia, the size of this public health problem is not well defined especially among primary schoolchildren. The purpose of this cross-sectional study was to assess the prevalence and pattern of refractive errors among primary school children in Al Hassa, Saudi Arabia. A total of 2246 Saudi primary school children aged 6 to 14 years of both genders were selected using multistage sampling method form 30 primary schools located in the three different areas of Al Hassa. School children were interviewed to collect demographics and vision data using a special data collection form followed by screening for refractive errors by trained optometrists within the school premises using a standardized protocol. Assessment of visual acuity and ocular motility evaluation were carried out and cover-uncover test was performed. Children detected with defective vision were referred for further examination employing subjective refraction with auto refractometer and objective refraction using streak retinoscopy after 1% cyclopentolate. Of the screened school children (N=2002), the overall prevalence of refractive errors was 13.7% (n=274), higher among females (Odds ratio, OR=1.39, P=0.012) and significantly more among students of rural residence (OR=2.40, P=0.001). The prevalence of refractive errors was disproportionately more among those aged 12-14 years (OR=9.02, P=0.001). Only 9.4% of students with poor vision were wore spectacles for correction. Myopia was the most commonly encountered refractive error among both genders (65.7% of the total errors encountered). Uncorrected refractive errors affected a sizable portion of primary school children in Al Hassa, Saudi Arabia. Primary schoolchildren especially females, rural and older children represents high risk group for refractive errors for which the included children were unaware. PMID:23283044

Refractive error and presbyopia among adults in Fiji.

PubMed

Brian, Garry; Pearce, Matthew G; Ramke, Jacqueline

2011-04-01

To characterize refractive error, presbyopia and their correction among adults aged ≥ 40 years in Fiji, and contribute to a regional overview of these conditions. A population-based cross-sectional survey using multistage cluster random sampling. Presenting distance and near vision were measured and dilated slitlamp examination performed. The survey achieved 73.0% participation (n=1381). Presenting binocular distance vision ≥ 6/18 was achieved by 1223 participants. Another 79 had vision impaired by refractive error. Three of these were blind. At threshold 6/18, 204 participants had refractive error. Among these, 125 had spectacle-corrected presenting vision ≥ 6/18 ("met refractive error need"); 79 presented wearing no (n=74) or under-correcting (n=5) distance spectacles ("unmet refractive error need"). Presenting binocular near vision ≥ N8 was achieved by 833 participants. At threshold N8, 811 participants had presbyopia. Among these, 336 attained N8 with presenting near spectacles ("met presbyopia need"); 475 presented with no (n=402) or under-correcting (n=73) near spectacles ("unmet presbyopia need"). Rural residence was predictive of unmet refractive error (p=0.040) and presbyopia (p=0.016) need. Gender and household income source were not. Ethnicity-gender-age-domicile-adjusted to the Fiji population aged ≥ 40 years, "met refractive error need" was 10.3% (95% confidence interval [CI] 8.7-11.9%), "unmet refractive error need" was 4.8% (95%CI 3.6-5.9%), "refractive error correction coverage" was 68.3% (95%CI 54.4-82.2%),"met presbyopia need" was 24.6% (95%CI 22.4-26.9%), "unmet presbyopia need" was 33.8% (95%CI 31.3-36.3%), and "presbyopia correction coverage" was 42.2% (95%CI 37.6-46.8%). Fiji refraction and dispensing services should encourage uptake by rural dwellers and promote presbyopia correction. Lack of comparable data from neighbouring countries prevents a regional overview.

Crystalline lens power and refractive error.

PubMed

Iribarren, Rafael; Morgan, Ian G; Nangia, Vinay; Jonas, Jost B

2012-02-01

To study the relationships between the refractive power of the crystalline lens, overall refractive error of the eye, and degree of nuclear cataract. All phakic participants of the population-based Central India Eye and Medical Study with an age of 50+ years were included. Calculation of the refractive lens power was based on distance noncycloplegic refractive error, corneal refractive power, anterior chamber depth, lens thickness, and axial length according to Bennett's formula. The study included 1885 subjects. Mean refractive lens power was 25.5 ± 3.0 D (range, 13.9-36.6). After adjustment for age and sex, the standardized correlation coefficients (β) of the association with the ocular refractive error were highest for crystalline lens power (β = -0.41; P < 0.001) and nuclear lens opacity grade (β = -0.42; P < 0.001), followed by axial length (β = -0.35; P < 0.001). They were lowest for corneal refractive power (β = -0.08; P = 0.001) and anterior chamber depth (β = -0.05; P = 0.04). In multivariate analysis, refractive error was significantly (P < 0.001) associated with shorter axial length (β = -1.26), lower refractive lens power (β = -0.95), lower corneal refractive power (β = -0.76), higher lens thickness (β = 0.30), deeper anterior chamber (β = 0.28), and less marked nuclear lens opacity (β = -0.05). Lens thickness was significantly lower in eyes with greater nuclear opacity. Variations in refractive error in adults aged 50+ years were mostly influenced by variations in axial length and in crystalline lens refractive power, followed by variations in corneal refractive power, and, to a minor degree, by variations in lens thickness and anterior chamber depth.

Distribution of intraocular pressure and its determinants in an Iranian adult population

PubMed Central

Hashemi, Hassan; Khabazkhoob, Mehdi; Emamian, Mohammad Hassan; Shariati, Mohammad; Yekta, Abbasali; Fotouhi, Akbar

2016-01-01

AIM To determine the distribution of intraocular pressure (IOP) and its determinants in an Iranian population. METHODS In a cross-sectional survey, random cluster sampling was conducted from the 40-64 years old population of Shahroud, in the north of Iran. All participants had optometry and ophthalmic exams. IOP was determined using the Goldmann tonometry method and biometric components were measured. RESULTS Of the 6311 people selected for the study, 5190 (82.2%) participated. The mean age of the participants was 50.9±6.2y and 58.7% of them were female. Mean IOP was 12.87±2.27 mm Hg. In this study 0.3% of the participants had an IOP higher than 21 mm Hg. The multiple linear regression model revealed that sex (Coef=-0.30; 95% CI: -0.43 to -0.17), diabetes (Coef=0.43; 95% CI: 0.19 to 0.67), high systolic blood pressure (Coef=0.02; 95% CI: 0.01 to 0.02), high body mass index (BMI) (Coef=0.03; 95% CI: 0.01 to 0.04), higher education (Coef=0.02, 95% CI: 0.01 to 0.04), thicker central corneal thickness (Coef=0.01; 95% CI: 0.01 to 0.02), and myopic shift in spherical equivalent (Coef=-0.14; 95% CI: -0.18 to -0.10) significantly correlated with high IOP. CONCLUSION The IOP in this 40-64 years old population is low overall. In the north of Iran, average IOP is statistically significantly correlated with female sex, diabetes, higher BMI, systolic blood pressure, higher education, thicker cornea, and myopic refractive error. PMID:27588277

Temporal properties of the myopic response to defocus in the guinea pig.

PubMed

Leotta, Amelia J; Bowrey, Hannah E; Zeng, Guang; McFadden, Sally A

2013-05-01

Hyperopic defocus induces myopia in all species tested and is believed to underlie the progression of human myopia. We determined the temporal properties of the effects of hyperopic defocus in a mammalian eye. In Experiment 1, the rise and decay time of the responses elicited by hyperopic defocus were calculated in 111 guinea pigs by giving repeated episodes of monocular -4 D lens wear (from 5 to 6 days of age for 12 days) interspersed with various dark intervals. In Experiment 2, the decay time constant was calculated in 152 guinea pigs when repeated periods of monocular -5 D lens-wear (from 4 days of age for 7 days) were interrupted with free viewing periods of different lengths. At the end of the lens-wear period, ocular parameters were measured and time constants were calculated relative to the maximum response induced by continuous lens wear. When hyperopic defocus was experienced with dark intervals between episodes, the time required to induce 50% of the maximum achievable myopia and ocular elongation was at most 30 min. Saturated 1 h episodes took at least 22 h for refractive error and 31 h for ocular length, to decay to 50% of the maximum response. However, the decay was an order of magnitude faster when hyperopic defocus episodes were interrupted with a daily free viewing period, with only 36 min required to reduce relative myopia and ocular elongation by 50%. Hyperopic defocus causes myopia with brief exposures and is very long lasting in the absence of competing signals. However, this myopic response rapidly decays if interrupted by periods of 'normal viewing' at least 30 min in length, wherein ocular growth appears to be guided preferentially by the least amount of hyperopic defocus experienced. Ophthalmic & Physiological Optics © 2013 The College of Optometrists.

The burden of pure anisometropic amblyopia: a cross-sectional study on 2800 Iranians.

PubMed

Akbarzadeh, Siamak; Vahabi, Reihaneh; Bazzazi, Nooshin; Roshanaei, Ghodratollah; Heydarian, Samira; Fouladi, Daniel F

2018-02-01

To assess the proportion of pure anisometropic amblyopia in a sample Iranian (white) population. A total of 2800 consecutive individuals who presented at a referral eye clinic for any reason were examined for the presence of pure anisometropic amblyopia. Anisometropia was reported when a spherical equivalent refraction difference of at least 1.0 D with or without a cylinder refraction difference of at least 1.0 D was present between the two eyes. Amblyopia was defined as the best-corrected visual acuity of 20/30 or worse or a two-line interocular visual acuity difference between eyes that could not be attributed to any structural ocular pathology or visual pathway abnormality. Subjects were 1528 females and 1272 males with a mean age of 30.25 ± 14.93 years (range, 5-65). Amblyopia was diagnosed in 192 cases (6.9%), significantly more frequent among females (7.9 vs. 5.7%, p = 0.02). Pure anisometropic amblyopia was present in 6.1% of the study population, significantly more common in patients with spherical hyperopic anisometropia (37.7%) compared to patients with spherical myopic anisometropia (21.3%), cylindrical myopic anisometropia (4.1%), and cylindrical hyperopic anisometropia (15%) (p < 0.001). Pure anisometropic amblyopia is a common finding in Caucasians seeking eye care, particularly when anisometropia is of spherical hyperopic subtype.

Comparison of Visian toric collamer lens and toric acrylic intraocular lens implantation for the treatment of myopia with astigmatism

PubMed Central

Ammar, Hatem; Anbar, Mohamed; Abdellah, Marwa M

2017-01-01

Purpose To compare the efficacy and outcome of phakic toric implantable collamer lens (TICL) and refractive clear lens extraction with AcrySof Toric intraocular lens (TIOL) implantation for the treatment of myopic astigmatism. Patients and methods This study assessed eyes with myopic astigmatism >−1 D and ≤−4 D with a spherical equivalent >10 D or <10 D if the patients were unsuitable for corneal refractive surgery. These eyes were divided into group A, in which Visian Toric ICL™ Phakic TICL was implanted, and group B, which involved clear lens extraction with implantation of an AcrySof IQ toric SN60T3-9™ IOL. The outcome and complications were evaluated. Results This study enrolled 63 eyes of 38 patients with a follow-up period of at least 6 months. The mean postoperative spherical equivalent was −0.19±0.31 D in group A and −0.21±0.28 D in group B (P=0.69). The mean postoperative cylinder value was −0.46±0.53 D in group A and −0.32±0.41 D in group B (P=0.35). Postoperative cylinder was <1 D in 76.47% and 79.31% of eyes in groups A and B, respectively. The mean endothelial cell count was reduced by 4.32% in group A and by 5.32% in group B (P=0.003). The mean postoperative intraocular pressure increased insignificantly in group A (P=0.22) and reduced significantly in group B (P=0.004). The complication rate was 11.76% in group A and 6.90% in group B. Conclusion Both procedures showed predictable results and good visual results. However, the loss of accommodation and risk of retinal complications in the TIOL group suggest that the use of TICL for myopic astigmatism is a better choice in younger patients. PMID:28096654

Responses of the Ocular Anterior Segment and Refraction to 0.5% Tropicamide in Chinese School-Aged Children of Myopia, Emmetropia, and Hyperopia.

PubMed

Yuan, Ying; Zhang, Zhengwei; Zhu, Jianfeng; He, Xiangui; Du, Ergang; Jiang, Kelimu; Zheng, Wenjing; Ke, Bilian

2015-01-01

Purpose. To investigate the changes of anterior segment after cycloplegia and estimate the association of such changes with the changes of refraction in Chinese school-aged children of myopia, emmetropia, and hyperopia. Methods. 309 children were recruited and eligible subjects were assigned to three groups: hyperopia, emmetropia, or myopia. Cycloplegia was achieved with five cycles of 0.5% tropicamide. The Pentacam system was used to measure the parameters of interest before and after cycloplegia. Results. In the myopic group, the lenses were thinner and the lens position was significantly more posterior than that of the emmetropic and hyperopic groups in the cycloplegic status. The correlations between refraction and lens thickness (age adjusted; r = 0.26, P < 0.01), and lens position (age adjusted; r = -0.31, P < 0.01) were found. After cycloplegia, ACD and ACV significantly increased, while ACA significantly decreased. Changes in refraction, ACD, ACV, and ACA were significantly different among the three groups (P < 0.05, all). Changes of refraction were correlated with changes of ACD (r = 0.41, P < 0.01). Conclusions. Myopia presented thinner lenses and smaller changes of anterior segment and refraction after cycloplegia when compared to emmetropia and hyperopia. Changes of anterior chamber depth were correlated with refraction changes. This may contribute to a better understanding of the relationship between anterior segment and myopia.

Clinical magnification and residual refraction after implantation of a double intraocular lens system in patients with macular degeneration.

PubMed

Amselem, Luis; Diaz-Llopis, Manuel; Felipe, Adelina; Artigas, Jose M; Navea, Amparo; García-Delpech, Salvador

2008-09-01

To evaluate the efficacy of a standard double intraocular lens (IOL) system (IOL-Vip) in patients with low vision and central scotoma due to macular degeneration and assess the predictability of the residual refraction and magnification. Ophthalmology Department, Hospital General Universitario, Valencia, Spain. This interventional prospective noncomparative case series comprised 13 consecutive surgical procedures in 10 patients with central scotoma. Follow-up was 12 months. Evaluation included the difference between preoperative and postoperative best corrected visual acuity (BCVA), refraction, position of the IOLs, endothelial cell density, and occurrence of postoperative complications. Residual refraction and eye magnification were calculated using a theory developed in a previous study, and the values were compared with the clinical results. The mean BCVA was 1.37 logMAR preoperatively and 0.68 logMAR 1 year postoperatively. The mean best corrected clinical gain was 44%. There was no statistically significant difference between the clinically evaluated and theoretically calculated residual refractions (P = .17). No intraoperative or postoperative complications occurred. Implantation of the double IOL system improved BCVA in patients with low vision due to advanced maculopathy. The results were best in myopic patients (long eyes); patients with hyperopia (short eyes) had high residual refraction. The postoperative clinical gain and residual refraction were predictable, showing the feasibility of implanting a customized double IOL.

Prevalence of uncorrected refractive errors among school-age children in the School District of Philadelphia.

PubMed

Mayro, Eileen L; Hark, Lisa A; Shiuey, Eric; Pond, Michael; Siam, Linda; Hill-Bennett, Tamara; Tran, Judie; Khanna, Nitasha; Silverstein, Marlee; Donaghy, James; Zhan, Tingting; Murchison, Ann P; Levin, Alex V

2018-06-01

To determine the prevalence and severity of uncorrected refractive errors in school-age children attending Philadelphia public schools. The Wills Eye Vision Screening Program for Children is a community-based pediatric vision screening program designed to detect and correct refractive errors and refer those with nonrefractive eye diseases for examination by a pediatric ophthalmologist. Between January 2014 and June 2016 the program screened 18,974 children in grades K-5 in Philadelphia public schools. Children who failed the vision screening were further examined by an on-site ophthalmologist or optometrist; children whose decreased visual acuity was not amenable to spectacle correction were referred to a pediatric ophthalmologist. Of the 18,974 children screened, 2,492 (13.1%) exhibited uncorrected refractive errors: 1,776 (9.4%) children had myopia, 459 (2.4%) had hyperopia, 1,484 (7.8%) had astigmatism, and 846 (4.5%) had anisometropia. Of the 2,492 with uncorrected refractive error, 368 children (14.8%) had more than one refractive error diagnosis. In stratifying refractive error diagnoses by severity, mild myopia (spherical equivalent of -0.50 D to < -3.00 D) was the most common diagnosis, present in 1,573 (8.3%) children. In this urban population 13.1% of school-age children exhibited uncorrected refractive errors. Blurred vision may create challenges for students in the classroom; school-based vision screening programs can provide an avenue to identify and correct refractive errors. Copyright © 2018 American Association for Pediatric Ophthalmology and Strabismus. Published by Elsevier Inc. All rights reserved.

Involvement of GABA Transporters in Atropine-Treated Myopic Retina As Revealed by iTRAQ Quantitative Proteomics

PubMed Central

2015-01-01

Atropine, a muscarinic antagonist, is known to inhibit myopia progression in several animal models and humans. However, the mode of action is not established yet. In this study, we compared quantitative iTRAQ proteomic analysis in the retinas collected from control and lens-induced myopic (LIM) mouse eyes treated with atropine. The myopic group received a (−15D) spectacle lens over the right eye on postnatal day 10 with or without atropine eye drops starting on postnatal day 24. Axial length was measured by optical low coherence interferometry (OLCI), AC-Master, and refraction was measured by automated infrared photorefractor at postnatal 24, 38, and 52 days. Retinal tissue samples were pooled from six eyes for each group. The experiments were repeated twice, and technical replicates were also performed for liquid chromatography–tandem mass spectrometry (LC–MS/MS) analysis. MetaCore was used to perform protein profiling for pathway analysis. We identified a total of 3882 unique proteins with <1% FDR by analyzing the samples in replicates for two independent experiments. This is the largest number of mouse retina proteome reported to date. Thirty proteins were found to be up-regulated (ratio for myopia/control > global mean ratio + 1 standard deviation), and 28 proteins were down-regulated (ratio for myopia/control < global mean ratio - 1 standard deviation) in myopic eyes as compared with control retinas. Pathway analysis using MetaCore revealed regulation of γ-aminobutyric acid (GABA) levels in the myopic eyes. Detailed analysis of the quantitative proteomics data showed that the levels of GABA transporter 1 (GAT-1) were elevated in myopic retina and significantly reduced after atropine treatment. These results were further validated with immunohistochemistry and Western blot analysis. In conclusion, this study provides a comprehensive quantitative proteomic analysis of atropine-treated mouse retina and suggests the involvement of GABAergic signaling in the antimyopic effects of atropine in mouse eyes. The GABAergic transmission in the neural retina plays a pivotal role in the maintenance of axial eye growth in mammals. PMID:25211393

LASIK versus photorefractive keratectomy for high myopic (> 3 diopter) astigmatism.

PubMed

Katz, Toam; Wagenfeld, Lars; Galambos, Peter; Darrelmann, Benedikt Große; Richard, Gisbert; Linke, Stephan Johannes

2013-12-01

To compare the efficacy, safety, predictability, and vector analysis indices of LASIK and photorefractive keratectomy (PRK) for correction of high cylinder of greater than 3 diopters (D) in myopic eyes. The efficacy, safety, and predictability of LASIK or PRK performed in 114 consecutive randomly selected myopic eyes with an astigmatism of greater than 3 D were retrospectively analyzed at the 2- to 6-month follow-up visits. Vector analysis of the cylindrical correction was compared between the treatment groups. A total of 57 eyes receiving PRK and 57 eyes receiving LASIK of 114 refractive surgery candidates were enrolled in the study. No statistically significant difference in efficacy [efficacy index = 0.76 (±0.32) for PRK vs 0.74 (±0.19) for LASIK (P = .82)], safety [safety index = 1.10 (±0.26) for PRK vs 1.01 (±0.17) for LASIK (P = .121)], or predictability [achieved astigmatism < 1 D in 39% of PRK- and 54% of LASIK-treated eyes, and < 2 D in 88% of PRK- and 89% of LASIK-treated eyes (P = .218)] was demonstrated. Using Alpins vector analysis, the surgically induced astigmatism and difference vector were not significantly different between the surgery methods, whereas the correction index showed a slight and significant advantage of LASIK over PRK (1.25 for PRK and 1.06 for LASIK, P < .001). LASIK and PRK are comparably safe, effective, and predictable procedures for excimer laser correction of high astigmatism of greater than 3 D in myopic eyes. Predictability of the correction of the cylindrical component is lower than that of the spherical equivalent. Copyright 2013, SLACK Incorporated.

Discriminating anisometropic amblyopia from myopia based on interocular inhibition

PubMed Central

Jia, Wuli; Zhou, Jiawei; Lu, Zhong-Lin; Lesmes, Luis A.; Huang, Chang-Bing

2016-01-01

Amblyopia screening during childhood is critical for early detection and successful treatment. In the current study, we develop and evaluate a screening method that exploits the imbalanced interocular inhibition between amblyopic and fellow eyes. In nineteen subjects with anisometropic amblyopia and twenty-two age-matched subjects with myopia, we measured the area under the contrast sensitivity functions (AUCSFs) in eight monocular conditions defined by tested eye (left, right), patching of the untested eye (translucent, opaque), and refractive status (corrected, uncorrected). For each test eye, we defined the inhibition index as the ratio between AUCSF values obtained in the translucent and opaque patching conditions of the untested eye. To evaluate the screening potential of the inhibition index, we compared results from patients with amblyopia and myopia. With and without optical correction, the index was significantly lower in the amblyopic eye than in the fellow eye of the amblyopic subjects and both eyes of the myopic subjects. No significant difference was found among the two eyes of the myopic subjects and the fellow eyes of the amblyopic subjects. With the inhibition index as the predictor, a logistic regression model successfully discriminated amblyopic eyes from myopic eyes with 100% accuracy in the uncorrected condition. In the corrected condition, with the inhibition index and interocular visual acuity difference as predictors, amblyopic eyes were likewise discriminated from myopic eyes with 100% accuracy. This pattern of CSF changes, caused by the different patching modes of the untested eye, provides a potential CSF signature to discriminate anisometropic amblyopia from myopia. PMID:25701741

Patient-reported Outcomes for Assessment of Quality of Life in Refractive Error: A Systematic Review.

PubMed

Kandel, Himal; Khadka, Jyoti; Goggin, Michael; Pesudovs, Konrad

2017-12-01

This review has identified the best existing patient-reported outcome (PRO) instruments in refractive error. The article highlights the limitations of the existing instruments and discusses the way forward. A systematic review was conducted to identify the types of PROs used in refractive error, to determine the quality of the existing PRO instruments in terms of their psychometric properties, and to determine the limitations in the content of the existing PRO instruments. Articles describing a PRO instrument measuring 1 or more domains of quality of life in people with refractive error were identified by electronic searches on the MEDLINE, PubMed, Scopus, Web of Science, and Cochrane databases. The information on content development, psychometric properties, validity, reliability, and responsiveness of those PRO instruments was extracted from the selected articles. The analysis was done based on a comprehensive set of assessment criteria. One hundred forty-eight articles describing 47 PRO instruments in refractive error were included in the review. Most of the articles (99 [66.9%]) used refractive error-specific PRO instruments. The PRO instruments comprised 19 refractive, 12 vision but nonrefractive, and 16 generic PRO instruments. Only 17 PRO instruments were validated in refractive error populations; six of them were developed using Rasch analysis. None of the PRO instruments has items across all domains of quality of life. The Quality of Life Impact of Refractive Correction, the Quality of Vision, and the Contact Lens Impact on Quality of Life have comparatively better quality with some limitations, compared with the other PRO instruments. This review describes the PRO instruments and informs the choice of an appropriate measure in refractive error. We identified need of a comprehensive and scientifically robust refractive error-specific PRO instrument. Item banking and computer-adaptive testing system can be the way to provide such an instrument.

Study on the refractive errors of school going children of Pokhara city in Nepal.

PubMed

Niroula, D R; Saha, C G

Refractive errors are the one of the most common visual disorders found worldwide in school going children and also it is one of the causes of blindness. It can easily be prevented, if timely proper measures are taken. In Kathmandu valley and Mechi Zone of Nepal, the distribution of refractive errors was found to be very high. No records are available from the Western part of Nepal. Considering the importance of the refractive errors the present study had been undertaken in Pokhara city. 964 subjects (474 boys, 490 girls) were selected between age groups 10 to 19 years from 6 schools representing different region of Pokhara. After Preliminary examination: on acuity of vision with Snellen's and Jaeger's charts, the subjects were referred to the Manipal Teaching Hospital, Pokhara for confirmation of the refractive errors. Sixty two schools children (6.43%), out of 964 had refractive errors. The myopia was found to be most common (4.05%). The refractive errors were found more in Private school children (9.29%) than Government school children (4.23%), which is statistically significant (P < 0.05). More boys (7.59%) were found to have suffered from refractive errors than girls (5.31%). Further, children with vegetarian diet (10.52%) had greater number of refractive errors than non-vegetarian diet children (6.17%). In the present study, percentage distribution of myopia was found to be higher (4.05%) than the hyperopia (1.24%) and astigmatism (1.14%). Interestingly, in the present study the refractive errors were found significantly higher in Private schools children than Government schools because the children who read in Private schools have higher socioeconomic status; spend more time in home work, watching Television and Computer as compared to government schools children. These near activities of the eyes causes stress on eyes of the children and might be one of the causes of developing myopia.

Frequency of under-corrected refractive errors in elderly Chinese in Beijing.

PubMed

Xu, Liang; Li, Jianjun; Cui, Tongtong; Tong, Zhongbiao; Fan, Guizhi; Yang, Hua; Sun, Baochen; Zheng, Yuanyuan; Jonas, Jost B

2006-07-01

The aim of the study was to evaluate the prevalence of under-corrected refractive error among elderly Chinese in the Beijing area. The population-based, cross-sectional, cohort study comprised 4,439 subjects out of 5,324 subjects asked to participate (response rate 83.4%) with an age of 40+ years. It was divided into a rural part [1,973 (44.4%) subjects] and an urban part [2,466 (55.6%) subjects]. Habitual and best-corrected visual acuity was measured. Under-corrected refractive error was defined as an improvement in visual acuity of the better eye of at least two lines with best possible refractive correction. The rate of under-corrected refractive error was 19.4% (95% confidence interval, 18.2, 20.6). In a multiple regression analysis, prevalence and size of under-corrected refractive error in the better eye was significantly associated with lower level of education (P<0.001), female gender (P<0.001), and age (P=0.001). Under-correction of refractive error is relatively common among elderly Chinese in the Beijing area when compared with data from other populations.

Uncorrected refractive error and presbyopia among junior high school teachers in Jakarta, Indonesia.

PubMed

Ehrlich, Joshua R; Laoh, Alex; Kourgialis, Nick; Prasetyanti, Widya; Zakiyah, Rima; Faillace, Silvana; Friedman, David S

2013-12-01

To report on the frequency of observed refractive and accommodative errors among junior high school teachers in Jakarta, Indonesia, who participated in a Helen Keller International screening, refraction and spectacle distribution program. A total of 965 teachers from 19 schools were eligible for screening; those with uncorrected distance visual acuity (VA) ≤ 6/12-3 and teachers ≥ 35 years old with uncorrected end-point print size >Jaeger (J) 6 were referred. Autorefraction and subjective refraction were performed for teachers with confirmed decreased VA. Refractive error was considered present if sphere ≤-0.75 diopters (D), sphere ≥+0.25D or cylinder ≤-0.50 D resulted in ≥ 2 lines of improvement in VA. Presbyopia was considered present if an end-point print size >J6 improved by ≥ 1 optotype with the use of a lens ≥+1.00 D. Overall, 866 teachers were screened (89.7% of those eligible) with complete screening data available for 858 (99.0%), among whom 762 failed screening. Distance refraction data were available for 666 of 762 (87.4%) and near refraction data for 520 of 686 (75.8%) teachers who failed screening. Of those screened, 76.2 ± 9.0% of teachers had refractive and/or accommodative error and 57.1 ± 7.6% had uncorrected refractive and/or accommodative error. Overall and uncorrected distance refractive error affected 44.2 ± 3.7% and 36.0 ± 3.6%, respectively; overall and uncorrected presbyopia affected 66.4 ± 8.1% and 41.0 ± 6.6%, respectively. As defined in this program, refractive and accommodative errors were common among teachers in Jakarta.

Assessing the accuracy and feasibility of a refractive error screening program conducted by school teachers in pre-primary and primary schools in Thailand.

PubMed

Teerawattananon, Kanlaya; Myint, Chaw-Yin; Wongkittirux, Kwanjai; Teerawattananon, Yot; Chinkulkitnivat, Bunyong; Orprayoon, Surapong; Kusakul, Suwat; Tengtrisorn, Supaporn; Jenchitr, Watanee

2014-01-01

As part of the development of a system for the screening of refractive error in Thai children, this study describes the accuracy and feasibility of establishing a program conducted by teachers. To assess the accuracy and feasibility of screening by teachers. A cross-sectional descriptive and analytical study was conducted in 17 schools in four provinces representing four geographic regions in Thailand. A two-staged cluster sampling was employed to compare the detection rate of refractive error among eligible students between trained teachers and health professionals. Serial focus group discussions were held for teachers and parents in order to understand their attitude towards refractive error screening at schools and the potential success factors and barriers. The detection rate of refractive error screening by teachers among pre-primary school children is relatively low (21%) for mild visual impairment but higher for moderate visual impairment (44%). The detection rate for primary school children is high for both levels of visual impairment (52% for mild and 74% for moderate). The focus group discussions reveal that both teachers and parents would benefit from further education regarding refractive errors and that the vast majority of teachers are willing to conduct a school-based screening program. Refractive error screening by health professionals in pre-primary and primary school children is not currently implemented in Thailand due to resource limitations. However, evidence suggests that a refractive error screening program conducted in schools by teachers in the country is reasonable and feasible because the detection and treatment of refractive error in very young generations is important and the screening program can be implemented and conducted with relatively low costs.

Optic Nerve Tilt, Crescent, Ovality, and Torsion in a Multi-Ethnic Cohort of Young Adults With and Without Myopia

PubMed Central

Marsh-Tootle, Wendy L.; Harb, Elise; Hou, Wei; Zhang, Qinghua; Anderson, Heather A.; Weise, Katherine; Norton, Thomas T.; Gwiazda, Jane; Hyman, Leslie

2017-01-01

Purpose The purpose of this article is to evaluate optic nerve head (ONH) characteristics in an ethnically diverse cohort of young U.S. adults. Methods In this study, 409 myopes and 206 nonmyopes (median age 22 years) completed measures including biometry and spectral domain optical coherence tomography from enface (ovality and torsion) and cross-sectional (tilt and crescent width) scans. Associated factors were evaluated using multivariable models. Results In myopic versus nonmyopic right eyes, median tilt (6.0° vs. 2.4°; P < 0.0001) and frequency of crescents (49% vs. 10%; P < 0.0001) were higher in myopes. Right eyes with crescents had higher median tilts (8.8° [myopic], 9.0° [nonmyopic]) than those without crescent (2.5° [myopic], 2.1° [nonmyopic]), irrespective of refractive group (both P < 0.0001). Torsion was similar between groups, with a slight difference in ovality (0.89 vs. 0.91; P < 0.03). Data in the left eyes were similar, and modeling was done only for the right myopic eyes. Multivariable models showed that an increased tilt was associated with ethnicity (P < 0.001), the presence of crescent (P < 0.001), and smaller ONH diameter (P < 0.0031), with interactions between ethnicity and crescent (P = 0.002). Specifically, ONH tilt was significantly higher in Asian eyes without crescent (P < 0.0001 for all comparisons), and crescent width was associated with increased tilt in non-Asian eyes (P < 0.02). Crescent width was associated with ethnicity (greatest in Asians) and disc tilt. Interactions were observed between tilt and ethnicity, whereby tilt had a greater effect on crescent width in non-Asian eyes, and crescent width was associated with increased tilt in non-Asian eyes. Conclusions The data clarify the influence of ethnicity and myopia on ONH characteristics in young adults and may inform future studies of biomechanical properties or of retinal pathology of the myopic eye. PMID:28654981

INVOLVEMENT OF MULTIPLE MOLECULAR PATHWAYS IN THE GENETICS OF OCULAR REFRACTION AND MYOPIA.

PubMed

Wojciechowski, Robert; Cheng, Ching-Yu

2018-01-01

The prevalence of myopia has increased dramatically worldwide within the last three decades. Recent studies have shown that refractive development is influenced by environmental, behavioral, and inherited factors. This review aims to analyze recent progress in the genetics of refractive error and myopia. A comprehensive literature search of PubMed and OMIM was conducted to identify relevant articles in the genetics of refractive error. Genome-wide association and sequencing studies have increased our understanding of the genetics involved in refractive error. These studies have identified interesting candidate genes. All genetic loci discovered to date indicate that refractive development is a heterogeneous process mediated by a number of overlapping biological processes. The exact mechanisms by which these biological networks regulate eye growth are poorly understood. Although several individual genes and/or molecular pathways have been investigated in animal models, a systematic network-based approach in modeling human refractive development is necessary to understand the complex interplay between genes and environment in refractive error. New biomedical technologies and better-designed studies will continue to refine our understanding of the genetics and molecular pathways of refractive error, and may lead to preventative and therapeutic measures to combat the myopia epidemic.

Effects of dopaminergic agents on progression of naturally occurring myopia in albino guinea pigs (Cavia porcellus).

PubMed

Jiang, Liqin; Long, Keli; Schaeffel, Frank; Zhou, Xiangtian; Zheng, Yibo; Ying, Huangfang; Lu, Fan; Stell, William K; Qu, Jia

2014-09-30

Disruption of dopaminergic signaling has been implicated in the abnormalities of ocular development in albinism, and many experiments have shown that retinal dopamine is a major regulator of postnatal eye growth and myopia in animal models. Therefore, in the present study we investigated whether progressive myopia, which can occur in albino guinea pigs without experimental manipulation of visual conditions, is affected by dopaminergic agents. Two-week-old albino guinea pigs, selected for being myopic (range refractive error [RE], -2 to -10 diopters [D]), received unilateral peribulbar injections of apomorphine (nonselective dopamine receptor agonist; 0, 7.5, 25, 75, 250, 750, and 2500 ng; n = 112), SKF38393 (D1-like agonist; 0, 10, 100, 1000 ng; n = 63), SCH23390 (D1-like antagonist; 0, 2500 ng; n = 27), quinpirole (D2-like agonist; 0, 10, 100, 1000 ng; n = 58), or sulpiride (D2-like antagonist; 0, 2500 ng; n = 24) once a day for four weeks. One noninjected group (n = 19) served as untreated control. Refractive states and axial dimensions of the eyes were measured without cycloplegia or general anesthetic, using eccentric infrared photoretinoscopy and A-scan ultrasonography, respectively, before treatment, and after 2 and 4 weeks of treatment. The main drug effects were analyzed by paired t-test or 2-way repeated measures ANOVA, as required. The naturally occurring progression of myopic RE was inhibited by apomorphine at relatively high doses (250 and 750 ng), SKF38393 at 100 ng (D1-like agonist), and sulpiride at 2500 ng (D2-like antagonist), but promoted by apomorphine at a lower dose (25 ng), quinpirole at 100 ng (D2-like agonist), and SCH23390 at 2500 ng (D1-like antagonist). All drugs affected primarily vitreous chamber depth, rather than anterior segment dimensions. Our data suggest that the activation of D1-like receptors inhibits, whereas activation of D2-like receptors promotes, progressive myopia in this animal model. The robust effects of antagonists suggest that ocular dopamine receptors in these albinos may be in a chronic state of partial excitation. The precise location and identity of the receptors responsible for these effects remain to be determined. Copyright 2014 The Association for Research in Vision and Ophthalmology, Inc.

Refractive errors in Mercyland Specialist Hospital, Osogbo, Western Nigeria.

PubMed

Adeoti, C O; Egbewale, B E

2008-06-01

The study was conducted to determine the magnitude and pattern of refractive errors in order to provide facilities for its management. A prospective study of 3601 eyes of 1824 consective patients was conducted. Information obtained included age, sex, occupation, visual acuity, type and degree of refractive error. The data was analysed using Statistical Package for Social Sciences 11.0 version) Computer Software. Refractive error was found in 1824(53.71%) patients. There were 832(45.61%) males and 992(54.39%) females with a mean age of 35.55. Myopia was the commonest (1412(39.21% eyes). Others include hypermetropia (840(23.33% eyes), astigmatism (785(21.80%) and 820 patients (1640 eyes) had presbyopia. Anisometropia was present in 791(44.51%) of 1777 patients that had bilateral refractive errors. Two thousand two hundred and fifty two eyes has spherical errors. Out of 2252 eyes with spherical errors, 1308 eyes (58.08%) had errors -0.50 to +0.50 dioptres, 567 eyes (25.18%) had errors less than -0.50 dioptres of whom 63 eyes (2.80%) had errors less than -5.00 dioptres while 377 eyes (16.74%) had errors greater than +0.50 dioptres of whom 81 eyes (3.60%) had errors greater than +2.00 dioptres. The highest error was 20.00 dioptres for myopia and 18.00 dioptres for hypermetropia. Refractive error is common in this environment. Adequate provision should be made for its correction bearing in mind the common types and degrees.

[A study of refractive errors in a primary school in Cotonou, Benin].

PubMed

Sounouvou, I; Tchabi, S; Doutetien, C; Sonon, F; Yehouessi, L; Bassabi, S K

2008-10-01

Determine the epidemiologic aspects and the degree of severity of different refractive errors in primary schoolchildren. A prospective and descriptive study was conducted from 1 December 2005 to 31 March 2006 on schoolchildren ranging from 4 to 16 years of age in a public primary school in Cotonou, Benin. The refraction was evaluated for any visual acuity lower than or equal to 0.7. The study included 1057 schoolchildren. The average age of the study population was 8.5+/-2.6 years with a slight predominance of females (51.8%). The prevalence of refractive error was 10.6% and astigmatism accounted for the most frequent refractive anomaly (91.9%). Myopia and the hyperopia were associated with astigmatism in 29.4% and 16.1% of the cases, respectively. The age bracket from 6 to 11 years accounted for the majority of refractive errors (75.9%), without age and sex being risk factors (p=0.811 and p=0.321, respectively). The average vision of the ametropic eye was 0.61, with a clear predominance of slight refractive errors (89.3%) and particularly of low-level simple astigmatism (45.5%). The relatively low prevalence of refractive error observed does not obviate the need for implementing actions to improve the ocular health of schoolchildren.

Comparison of self-refraction using a simple device, USee, with manifest refraction in adults.

PubMed

Annadanam, Anvesh; Varadaraj, Varshini; Mudie, Lucy I; Liu, Alice; Plum, William G; White, J Kevin; Collins, Megan E; Friedman, David S

2018-01-01

The USee device is a new self-refraction tool that allows users to determine their own refractive error. We evaluated the ease of use of USee in adults, and compared the refractive error correction achieved with USee to clinical manifest refraction. Sixty adults with uncorrected visual acuity <20/30 and spherical equivalent between -6.00 and +6.00 diopters completed manifest refraction and self-refraction. Subjects had a mean (±SD) age of 53.1 (±18.6) years, and 27 (45.0%) were male. Mean (±SD) spherical equivalent measured by manifest refraction and self-refraction were -0.90 D (±2.53) and -1.22 diopters (±2.42), respectively (p = 0.001). The proportion of subjects correctable to ≥20/30 in the better eye was higher for manifest refraction (96.7%) than self-refraction (83.3%, p = 0.005). Failure to achieve visual acuity ≥20/30 with self-refraction in right eyes was associated with increasing age (per year, OR: 1.05; 95% CI: 1.00-1.10) and higher cylindrical power (per diopter, OR: 7.26; 95% CI: 1.88-28.1). Subjectively, 95% of participants thought USee was easy to use, 85% thought self-refraction correction was better than being uncorrected, 57% thought vision with self-refraction correction was similar to their current corrective lenses, and 53% rated their vision as "very good" or "excellent" with self-refraction. Self-refraction provides acceptable refractive error correction in the majority of adults. Programs targeting resource-poor settings could potentially use USee to provide easy on-site refractive error correction.

The patterns of refractive errors among the school children of rural and urban settings in Nepal.

PubMed

Pokharel, A; Pokharel, P K; Das, H; Adhikari, S

2010-01-01

The uncorrected refractive error is an important cause of childhood blindness and visual impairment. To study the patterns of refractive errors among the urban and rural school going children of Nepal. A total of 440 school children of urban and rural schools within the age range of 7-15 years were selected for this study using multi-stage randomization technique. The overall prevalance of refractive error in school children was 19.8 %. The commonest refractive error among the students was myopia (59.8 %), followed by hypermetropia (31.0 %). The children of age group 12-15 years had the higher prevalence of myopia as compared to the younger counterparts (42.5 % vs 17.2 %). The prevalence of myopia was 15.5 % among the urban students as compared to 8.2 % among the rural ones (RR = 1.89, 95 % CI = 1.1-3.24). The hypermetropia was more common in urban students than in rural ones (6.4 %) vs 5.9 %, RR = 1.08 (95 % CI: 0.52-2.24). The prevalence of refractive error in the school children of Nepal is 19.8 %. The students from urban settings are more likely to have refractive error than their rural counterparts. © Nepal Ophthalmic Society.

Assumption-free estimation of the genetic contribution to refractive error across childhood.

PubMed

Guggenheim, Jeremy A; St Pourcain, Beate; McMahon, George; Timpson, Nicholas J; Evans, David M; Williams, Cathy

2015-01-01

Studies in relatives have generally yielded high heritability estimates for refractive error: twins 75-90%, families 15-70%. However, because related individuals often share a common environment, these estimates are inflated (via misallocation of unique/common environment variance). We calculated a lower-bound heritability estimate for refractive error free from such bias. Between the ages 7 and 15 years, participants in the Avon Longitudinal Study of Parents and Children (ALSPAC) underwent non-cycloplegic autorefraction at regular research clinics. At each age, an estimate of the variance in refractive error explained by single nucleotide polymorphism (SNP) genetic variants was calculated using genome-wide complex trait analysis (GCTA) using high-density genome-wide SNP genotype information (minimum N at each age=3,404). The variance in refractive error explained by the SNPs ("SNP heritability") was stable over childhood: Across age 7-15 years, SNP heritability averaged 0.28 (SE=0.08, p<0.001). The genetic correlation for refractive error between visits varied from 0.77 to 1.00 (all p<0.001) demonstrating that a common set of SNPs was responsible for the genetic contribution to refractive error across this period of childhood. Simulations suggested lack of cycloplegia during autorefraction led to a small underestimation of SNP heritability (adjusted SNP heritability=0.35; SE=0.09). To put these results in context, the variance in refractive error explained (or predicted) by the time participants spent outdoors was <0.005 and by the time spent reading was <0.01, based on a parental questionnaire completed when the child was aged 8-9 years old. Genetic variation captured by common SNPs explained approximately 35% of the variation in refractive error between unrelated subjects. This value sets an upper limit for predicting refractive error using existing SNP genotyping arrays, although higher-density genotyping in larger samples and inclusion of interaction effects is expected to raise this figure toward twin- and family-based heritability estimates. The same SNPs influenced refractive error across much of childhood. Notwithstanding the strong evidence of association between time outdoors and myopia, and time reading and myopia, less than 1% of the variance in myopia at age 15 was explained by crude measures of these two risk factors, indicating that their effects may be limited, at least when averaged over the whole population.

Effects of Constant Flickering Light on Refractive Status, 5-HT and 5-HT2A Receptor in Guinea Pigs.

PubMed

Li, Bing; Luo, Xiumei; Li, Tao; Zheng, Changyue; Ji, Shunmei; Ma, Yuanyuan; Zhang, Shuangshuang; Zhou, Xiaodong

2016-01-01

To investigate the effects of constant flickering light on refractive development, the role of serotonin (i.e.5-hydroxytryptamine, 5-HT)and 5-HT2A receptor in myopia induced by flickering light in guinea pigs. Forty-five guinea pigs were randomly divided into three groups: control, form deprivation myopia (FDM) and flickering light induced myopia (FLM) groups(n = 15 for each group). The right eyes of the FDM group were covered with semitransparent hemispherical plastic shells serving as eye diffusers. Guinea pigs in FLM group were raised with illumination of a duty cycle of 50% at a flash frequency of 0.5Hz. The refractive status, axial length (AL), corneal radius of curvature(CRC) were measured by streak retinoscope, A-scan ultrasonography and keratometer, respectively. Ultramicroscopy images were taken by electron microscopy. The concentrations of 5-HTin the retina, vitreous body and retinal pigment epithelium (RPE) were assessed by high performance liquid chromatography, the retinal 5-HT2A receptor expression was evaluated by immunohistofluorescence and western blot. The refraction of FDM and FLM eyes became myopic from some time point (the 4th week and the 6th week, respectively) in the course of the experiment, which was indicated by significantly decreased refraction and longer AL when compared with the controls (p<0.05). The concentrations of 5-HT in the retina, vitreous body and RPE of FDM and FLM eyes were significantly increased in comparison with those of control eyes (both p<0.05). Similar to FDM eyes, the expression of retinal 5-HT2A receptor in FLM eyes was significantly up-regulated compared to that of control eyes (both p<0.05). Western blot analysis showed that retinal 5-HT2A receptor level elevated less in the FLM eyes than that in the FDM eyes. Moreover, the levels of norepinephrine and epinephrine in FDM and FLM groups generally decreased when compared with control groups (all p<0.05). Constant flickering light could cause progressive myopia in guinea pigs. 5-HT and 5-HT2A receptor increased both in form deprivation myopia and flickering light induced myopia, indicating that 5-HT possibly involved in myopic development via binding to5-HT2A receptor.

Effects of Constant Flickering Light on Refractive Status, 5-HT and 5-HT2A Receptor in Guinea Pigs

PubMed Central

Li, Tao; Zheng, Changyue; Ji, Shunmei; Ma, Yuanyuan; Zhang, Shuangshuang; Zhou, Xiaodong

2016-01-01

Purpose To investigate the effects of constant flickering light on refractive development, the role of serotonin (i.e.5-hydroxytryptamine, 5-HT)and 5-HT2A receptor in myopia induced by flickering light in guinea pigs. Methods Forty-five guinea pigs were randomly divided into three groups: control, form deprivation myopia (FDM) and flickering light induced myopia (FLM) groups(n = 15 for each group). The right eyes of the FDM group were covered with semitransparent hemispherical plastic shells serving as eye diffusers. Guinea pigs in FLM group were raised with illumination of a duty cycle of 50% at a flash frequency of 0.5Hz. The refractive status, axial length (AL), corneal radius of curvature(CRC) were measured by streak retinoscope, A-scan ultrasonography and keratometer, respectively. Ultramicroscopy images were taken by electron microscopy. The concentrations of 5-HTin the retina, vitreous body and retinal pigment epithelium (RPE) were assessed by high performance liquid chromatography, the retinal 5-HT2A receptor expression was evaluated by immunohistofluorescence and western blot. Results The refraction of FDM and FLM eyes became myopic from some time point (the 4th week and the 6th week, respectively) in the course of the experiment, which was indicated by significantly decreased refraction and longer AL when compared with the controls (p<0.05). The concentrations of 5-HT in the retina, vitreous body and RPE of FDM and FLM eyes were significantly increased in comparison with those of control eyes (both p<0.05). Similar to FDM eyes, the expression of retinal 5-HT2A receptor in FLM eyes was significantly up-regulated compared to that of control eyes (both p<0.05). Western blot analysis showed that retinal 5-HT2A receptor level elevated less in the FLM eyes than that in the FDM eyes. Moreover, the levels of norepinephrine and epinephrine in FDM and FLM groups generally decreased when compared with control groups (all p<0.05). Conclusions Constant flickering light could cause progressive myopia in guinea pigs. 5-HT and 5-HT2A receptor increased both in form deprivation myopia and flickering light induced myopia, indicating that 5-HT possibly involved in myopic development via binding to5-HT2A receptor. PMID:27959948

Refractive errors in 3-6 year-old Chinese children: a very low prevalence of myopia?

PubMed

Lan, Weizhong; Zhao, Feng; Lin, Lixia; Li, Zhen; Zeng, Junwen; Yang, Zhikuan; Morgan, Ian G

2013-01-01

To examine the prevalence of refractive errors in children aged 3-6 years in China. Children were recruited for a trial of a home-based amblyopia screening kit in Guangzhou preschools, during which cycloplegic refractions were measured in both eyes of 2480 children. Cycloplegic refraction (from 3 to 4 drops of 1% cyclopentolate to ensure abolition of the light reflex) was measured by both autorefraction and retinoscopy. Refractive errors were defined as followed: myopia (at least -0.50 D in the worse eye), hyperopia (at least +2.00 D in the worse eye) and astigmatism (at least 1.50 D in the worse eye). Different definitions, as specified in the text, were also used to facilitate comparison with other studies. The mean spherical equivalent refractive error was at least +1.22 D for all ages and both genders. The prevalence of myopia for any definition at any age was at most 2.5%, and lower in most cases. In contrast, the prevalence of hyperopia was generally over 20%, and declined slightly with age. The prevalence of astigmatism was between 6% and 11%. There was very little change in refractive error with age over this age range. Previous reports of less hyperopic mean spherical equivalent refractive error, and more myopia and less hyperopia in children of this age may be due to problems with achieving adequate cycloplegia in children with dark irises. Using up to 4 drops of 1% cyclopentolate may be necessary to accurately measure refractive error in paediatric studies of such children. Our results suggest that children from all ethnic groups may follow a similar pattern of early refractive development, with little myopia and a hyperopic mean spherical equivalent over +1.00 D up to the age of 5-6 years in most conditions.

Population-based survey of refractive error among school-aged children in rural northern China: the Heilongjiang eye study.

PubMed

Li, Zhijian; Xu, Keke; Wu, Shubin; Lv, Jia; Jin, Di; Song, Zhen; Wang, Zhongliang; Liu, Ping

2014-01-01

The prevalence of refractive error in the north of China is unknown. The study aimed to estimate the prevalence and associated factors of refractive error in school-aged children in a rural area of northern China. Cross-sectional study. The cluster random sampling method was used to select the sample. A total of 1700 subjects of 5 to 18 years of age were examined. All participants underwent ophthalmic evaluation. Refraction was performed under cycloplegia. Association of refractive errors with age, sex, and education was analysed. The main outcome measure was prevalence rates of refractive error among school-aged children. Of the 1700 responders, 1675 were eligible. The prevalence of uncorrected, presenting, and best-corrected visual acuity of 20/40 or worse in the better eye was 6.3%, 3.0% and 1.2%, respectively. The prevalence of myopia was 5.0% (84/1675, 95% CI, 4.8%-5.4%) and of hyperopia was 1.6% (27/1675, 95% CI, 1.0%-2.2%). Astigmatism was evident in 2.0% of the subjects. Myopia increased with increasing age, whereas hyperopia and astigmatism were associated with younger age. Myopia, hyperopia and astigmatism were more common in females. We also found that prevalence of refractive error were associated with education. Myopia and astigmatism were more common in those with higher degrees of education. This report has provided details of the refractive status in a rural school-aged population. Although the prevalence of refractive errors is lower in the population, the unmet need for spectacle correction remains a significant challenge for refractive eye-care services. © 2013 Royal Australian and New Zealand College of Ophthalmologists.

Astigmatism

MedlinePlus

... retina, at the back of your eye. A refractive error If either your cornea or lens is egg ... too close to the television or squinting. Other refractive errors Astigmatism may occur in combination with other refractive ...

Myopia, contact lens use and self-esteem.

PubMed

Dias, Lynette; Manny, Ruth E; Weissberg, Erik; Fern, Karen D

2013-09-01

To evaluate whether contact lens (CL) use was associated with self-esteem in myopic children originally enrolled in the Correction of Myopia Evaluation Trial (COMET), that after 5 years continued as an observational study of myopia progression with CL use permitted. Usable data at the 6-year visit, one year after CL use was allowed (n = 423/469, age 12-17 years), included questions on CL use, refractive error measurements and self-reported self-esteem in several areas (scholastic/athletic competence, physical appearance, social acceptance, behavioural conduct and global self-worth). Self-esteem, scored from 1 (low) to 4 (high), was measured by the Self-Perception Profile for Children in participants under 14 years or the Self-Perception Profile for Adolescents, in those 14 years and older. Multiple regression analyses were used to evaluate associations between self-esteem and relevant factors identified by univariate analyses (e.g., CL use, gender, ethnicity), while adjusting for baseline self-esteem prior to CL use. Mean (±S.D.) self-esteem scores at the 6-year visit (mean age = 15.3 ± 1.3 years; mean refractive error = -4.6 ± 1.5 D) ranged from 2.74 (± 0.76) on athletic competence to 3.33 (± 0.53) on global self-worth. CL wearers (n = 224) compared to eyeglass wearers (n = 199) were more likely to be female (p < 0.0001). Those who chose to wear CLs had higher social acceptance, athletic competence and behavioural conduct scores (p < 0.05) at baseline compared to eyeglass users. CL users continued to report higher social acceptance scores at the 6-year visit (p = 0.03), after adjusting for baseline scores and other covariates. Ethnicity was also independently associated with social acceptance in the multivariable analyses (p = 0.011); African-Americans had higher scores than Asians, Whites and Hispanics. Age and refractive error were not associated with self-esteem or CL use. COMET participants who chose to wear CLs after 5 years of eyeglass use had higher self-esteem compared to those who remained in glasses both preceding and following CL use. This suggests that self-esteem may influence the decision to wear CLs and that CLs in turn are associated with higher self-esteem in individuals most likely to wear them. © 2013 The Authors Ophthalmic & Physiological Optics © 2013 The College of Optometrists.

Refractive Errors in Patients with Migraine Headache.

PubMed

Gunes, Alime; Demirci, Seden; Tok, Levent; Tok, Ozlem; Koyuncuoglu, Hasan; Yurekli, Vedat Ali

2016-01-01

To evaluate refractive errors in patients with migraine headache and to compare with healthy subjects. This prospective case-control study includes patients with migraine and age- and sex-matched healthy subjects. Clinical and demographic characteristics of the patients were noted. Detailed ophthalmological examinations were performed containing spherical refractive error, astigmatic refractive error, spherical equivalent (SE), anisometropia, best-corrected visual acuity, intraocular pressure, slit lamp biomicroscopy, fundus examination, axial length, anterior chamber depth, and central corneal thickness. Spectacle use in migraine and control groups was compared. Also, the relationship between refractive components and migraine headache variables was investigated. Seventy-seven migraine patients with mean age of 33.27 ± 8.84 years and 71 healthy subjects with mean age of 31.15 ± 10.45 years were enrolled (p = 0.18). The migraine patients had higher degrees of astigmatic refractive error, SE, and anisometropia when compared with the control subjects (p = 0.01, p = 0.03, p = 0.02, respectively). Migraine patients may have higher degrees of astigmatism, SE, and anisometropia. Therefore, they should have ophthalmological examinations regularly to ensure that their refractive errors are appropriately corrected.

Accommodative Lag by Autorefraction and Two Dynamic Retinoscopy Methods

PubMed Central

2008-01-01

Purpose To evaluate two clinical procedures, MEM and Nott retinoscopy, for detecting accommodative lags 1.00 diopter (D) or greater in children as identified by an open-field autorefractor. Methods 168 children 8 to <12 years old with low myopia, normal visual acuity, and no strabismus participated as part of an ancillary study within the screening process for a randomized trial. Accommodative response to a 3.00 D demand was first assessed by MEM and Nott retinoscopy, viewing binocularly with spherocylindrical refractive error corrected, with testing order randomized and each performed by a different masked examiner. The response was then determined viewing monocularly with spherical equivalent refractive error corrected, using an open-field autorefractor, which was the gold standard used for eligibility for the clinical trial. Sensitivity and specificity for accommodative lags of 1.00 D or more were calculated for each retinoscopy method compared to the autorefractor. Results 116 (69%) of the 168 children had accommodative lag of 1.00 D or more by autorefraction. MEM identified 66 children identified by autorefraction for a sensitivity of 57% (95% CI = 47% to 66%) and a specificity of 63% (95% CI = 49% to 76%). Nott retinoscopy identified 35 children for a sensitivity of 30% (95% CI = 22% to 39%) and a specificity of 81% (95% CI = 67% to 90%). Analysis of receiver operating characteristic (ROC) curves constructed for MEM and for Nott retinoscopy failed to reveal alternate cut points that would improve the combination of sensitivity and specificity for identifying accommodative lag ≥ 1.00 D as defined by autorefraction. Conclusions Neither MEM nor Nott retinoscopy provided adequate sensitivity and specificity to identify myopic children with accommodative lag ≥ 1.00 D as determined by autorefraction. A variety of methodological differences between the techniques may contribute to the modest to poor agreement. PMID:19214130

Effectiveness of Toric Orthokeratology in the Treatment of Patients with Combined Myopia and Astigmatism

PubMed Central

Lyu, Byul; Hwang, Kyu Yeon; Kim, Sun Young; Kim, Su Young

2016-01-01

Purpose The purpose of this multi-institute, single-group clinical trial was to evaluate the effectiveness and safety of toric orthokeratology lenses for the treatment of patients with combined myopia and astigmatism. Methods A total of 44 patients were included in this clinical trial. The patients ranged in age from 7 to 49 years, with myopia of -0.75 to -6.0 diopters (D) and astigmatism of 1.25 to 4.0 D. After excluding 21 subjects, 23 subjects (39 eyes) were analyzed after toric orthokeratology lens use. The subjects underwent ophthalmologic examination after 1 day and 1, 2, 3, and 4 weeks of wearing overnight toric orthokeratology lenses. Results A total of 19 subjects (31 eyes) completed the trial after five subjects (eight eyes) dropped out. In the patients who completed the study by wearing lenses for 4 weeks, the myopic refractive error decreased significantly by 2.60 ± 2.21 D (p < 0.001), from -3.65 ± 1.62 to -1.05 ± 1.64 D. The astigmatic refractive error were also significantly decreased by 0.63 ± 0.98 D (p = 0.001), from 2.07 ± 0.83 to 1.44 ± 0.99 D. The mean uncorrected and corrected visual acuities before wearing the lenses were 2.14 ± 0.80 logarithm of the logMAR (logMAR) and 0.05 ± 0.13 logMAR, respectively, which changed to 0.12 ± 0.30 logarithm of the logMAR (p < 0.001) and 0.01 ± 0.04 logMAR (p = 0.156) after 4 weeks. No serious adverse reactions were reported during the clinical trial. Conclusions Our results suggest that toric orthokeratology is an effective and safe treatment for correcting visual acuity in patients with combined myopia and astigmatism. PMID:27980362

Refraction test

MedlinePlus

... purpose is to determine whether you have a refractive error (a need for glasses or contact lenses). For ... glasses or contact lenses) is normal, then the refractive error is zero (plano) and your vision should be ...

Automated refraction is stable 1 week after uncomplicated cataract surgery.

PubMed

Ostri, Christoffer; Holfort, Stig K; Fich, Marianne S; Riise, Per

2018-03-01

To compare automated refraction 1 week and 1 month after uncomplicated cataract surgery. In this prospective cohort study, we recruited patients in a 2-month period and included consecutive patients scheduled for bilateral small-incision phacoemulsification cataract surgery. The exclusion criteria were (i) corneal and/or retinal pathology that could lead to automated refraction miscalculation and (ii) surgery complications. Automated refraction was measured 1 week and 1 month after surgery. Ninety-five patients met the in- and exclusion criteria and completed follow-up. The mean refractive shift in spherical equivalent was -0.02 dioptre (D) between 1 week and 1 month after surgery and not statistical significant (p = 0.78, paired t-test). The magnitude of refractive shift in either myopic or hyperopic direction was neither correlated to age, preoperative corneal astigmatism, axial length nor phacoemulsification energy used during surgery (p > 0.05 for all variables, regression analysis). The refractive target was missed with 1.0 D or more in 11 (12%) patients. In this subgroup, the mean refractive shift in spherical equivalent was 0.49 D between 1 week and 1 month after surgery with a trend towards statistical significance (p = 0.07, paired t-test). There was no difference in age, preoperative corneal astigmatism, axial length or phacoemulsification energy used during surgery compared to the remainder of the patients (p > 0.05 for all variables, unpaired t-test). Automated refraction is stabile 1 week after uncomplicated cataract surgery, but there is a trend towards instability, if the refractive target is missed with 1.0 D or more. © 2017 Acta Ophthalmologica Scandinavica Foundation. Published by John Wiley & Sons Ltd.

Screening for refractive error among primary school children in Bayelsa state, Nigeria

PubMed Central

Opubiri, Ibeinmo; Pedro-Egbe, Chinyere

2013-01-01

Introduction Vision screening study in primary school children has not been done in Bayelsa State. This study aims to screen for refractive error among primary school children in Bayelsa State and use the data to plan for school Eye Health Program. Methods A cross sectional study on screening for refractive error in school children was carried out in Yenagoa Local Government Area of Bayelsa State in June 2009. A multistage sampling technique was used to select the study population (pupils aged between 5-15 years). Visual acuity (VA) for each eye, was assessed outside the classroom at a distance of 6 meters. Those with VA ≤6/9 were presented with a pinhole and the test repeated. Funduscopy was done inside a poorly lit classroom. An improvement of the VA with pinhole was considered refractive error. Data was analyzed with EPI INFO version 6. Results A total of 1,242 school children consisting of 658 females and 584 males were examined.About 97.7% of pupils had normal VA (VA of 6/6) while 56 eyes had VAs ≤ 6/9. Of these 56 eyes, the visual acuity in 49 eyes (87.5%) improved with pinhole. Twenty seven pupils had refractive error, giving a prevalence of 2.2%. Refractive error involved both eyes in 22 pupils (81.5%) and the 8-10 years age range had the highest proportion (40.7%) of cases of refractive error followed by the 9-13 year-old age range (37%). Conclusion The prevalence of refractive error was 2.2% and most eyes (97.7%) had normal vision. PMID:23646210

Prevalence of amblyopia and patterns of refractive error in the amblyopic children of a tertiary eye care center of Nepal.

PubMed

Sapkota, K; Pirouzian, A; Matta, N S

2013-01-01

Refractive error is a common cause of amblyopia. To determine prevalence of amblyopia and the pattern and the types of refractive error in children with amblyopia in a tertiary eye hospital of Nepal. A retrospective chart review of children diagnosed with amblyopia in the Nepal Eye Hospital (NEH) from July 2006 to June 2011 was conducted. Children of age 13+ or who had any ocular pathology were excluded. Cycloplegic refraction and an ophthalmological examination was performed for all children. The pattern of refractive error and the association between types of refractive error and types of amblyopia were determined. Amblyopia was found in 0.7 % (440) of 62,633 children examined in NEH during this period. All the amblyopic eyes of the subjects had refractive error. Fifty-six percent (248) of the patients were male and the mean age was 7.74 ± 2.97 years. Anisometropia was the most common cause of amblyopia (p less than 0.001). One third (29 %) of the subjects had bilateral amblyopia due to high ametropia. Forty percent of eyes had severe amblyopia with visual acuity of 20/120 or worse. About twothirds (59.2 %) of the eyes had astigmatism. The prevalence of amblyopia in the Nepal Eye Hospital is 0.7%. Anisometropia is the most common cause of amblyopia. Astigmatism is the most common types of refractive error in amblyopic eyes. © NEPjOPH.

Emmetropisation and the aetiology of refractive errors

PubMed Central

Flitcroft, D I

2014-01-01

The distribution of human refractive errors displays features that are not commonly seen in other biological variables. Compared with the more typical Gaussian distribution, adult refraction within a population typically has a negative skew and increased kurtosis (ie is leptokurtotic). This distribution arises from two apparently conflicting tendencies, first, the existence of a mechanism to control eye growth during infancy so as to bring refraction towards emmetropia/low hyperopia (ie emmetropisation) and second, the tendency of many human populations to develop myopia during later childhood and into adulthood. The distribution of refraction therefore changes significantly with age. Analysis of the processes involved in shaping refractive development allows for the creation of a life course model of refractive development. Monte Carlo simulations based on such a model can recreate the variation of refractive distributions seen from birth to adulthood and the impact of increasing myopia prevalence on refractive error distributions in Asia. PMID:24406411

Comparison of self-refraction using a simple device, USee, with manifest refraction in adults

PubMed Central

Annadanam, Anvesh; Mudie, Lucy I.; Liu, Alice; Plum, William G.; White, J. Kevin; Collins, Megan E.; Friedman, David S.

2018-01-01

Background The USee device is a new self-refraction tool that allows users to determine their own refractive error. We evaluated the ease of use of USee in adults, and compared the refractive error correction achieved with USee to clinical manifest refraction. Methods Sixty adults with uncorrected visual acuity <20/30 and spherical equivalent between –6.00 and +6.00 diopters completed manifest refraction and self-refraction. Results Subjects had a mean (±SD) age of 53.1 (±18.6) years, and 27 (45.0%) were male. Mean (±SD) spherical equivalent measured by manifest refraction and self-refraction were –0.90 D (±2.53) and –1.22 diopters (±2.42), respectively (p = 0.001). The proportion of subjects correctable to ≥20/30 in the better eye was higher for manifest refraction (96.7%) than self-refraction (83.3%, p = 0.005). Failure to achieve visual acuity ≥20/30 with self-refraction in right eyes was associated with increasing age (per year, OR: 1.05; 95% CI: 1.00–1.10) and higher cylindrical power (per diopter, OR: 7.26; 95% CI: 1.88–28.1). Subjectively, 95% of participants thought USee was easy to use, 85% thought self-refraction correction was better than being uncorrected, 57% thought vision with self-refraction correction was similar to their current corrective lenses, and 53% rated their vision as “very good” or “excellent” with self-refraction. Conclusion Self-refraction provides acceptable refractive error correction in the majority of adults. Programs targeting resource-poor settings could potentially use USee to provide easy on-site refractive error correction. PMID:29390026

Refraction error correction for deformation measurement by digital image correlation at elevated temperature

NASA Astrophysics Data System (ADS)

Su, Yunquan; Yao, Xuefeng; Wang, Shen; Ma, Yinji

2017-03-01

An effective correction model is proposed to eliminate the refraction error effect caused by an optical window of a furnace in digital image correlation (DIC) deformation measurement under high-temperature environment. First, a theoretical correction model with the corresponding error correction factor is established to eliminate the refraction error induced by double-deck optical glass in DIC deformation measurement. Second, a high-temperature DIC experiment using a chromium-nickel austenite stainless steel specimen is performed to verify the effectiveness of the correction model by the correlation calculation results under two different conditions (with and without the optical glass). Finally, both the full-field and the divisional displacement results with refraction influence are corrected by the theoretical model and then compared to the displacement results extracted from the images without refraction influence. The experimental results demonstrate that the proposed theoretical correction model can effectively improve the measurement accuracy of DIC method by decreasing the refraction errors from measured full-field displacements under high-temperature environment.

Intertester agreement in refractive error measurements.

PubMed

Huang, Jiayan; Maguire, Maureen G; Ciner, Elise; Kulp, Marjean T; Quinn, Graham E; Orel-Bixler, Deborah; Cyert, Lynn A; Moore, Bruce; Ying, Gui-Shuang

2013-10-01

To determine the intertester agreement of refractive error measurements between lay and nurse screeners using the Retinomax Autorefractor and the SureSight Vision Screener. Trained lay and nurse screeners measured refractive error in 1452 preschoolers (3 to 5 years old) using the Retinomax and the SureSight in a random order for screeners and instruments. Intertester agreement between lay and nurse screeners was assessed for sphere, cylinder, and spherical equivalent (SE) using the mean difference and the 95% limits of agreement. The mean intertester difference (lay minus nurse) was compared between groups defined based on the child's age, cycloplegic refractive error, and the reading's confidence number using analysis of variance. The limits of agreement were compared between groups using the Brown-Forsythe test. Intereye correlation was accounted for in all analyses. The mean intertester differences (95% limits of agreement) were -0.04 (-1.63, 1.54) diopter (D) sphere, 0.00 (-0.52, 0.51) D cylinder, and -0.04 (1.65, 1.56) D SE for the Retinomax and 0.05 (-1.48, 1.58) D sphere, 0.01 (-0.58, 0.60) D cylinder, and 0.06 (-1.45, 1.57) D SE for the SureSight. For either instrument, the mean intertester differences in sphere and SE did not differ by the child's age, cycloplegic refractive error, or the reading's confidence number. However, for both instruments, the limits of agreement were wider when eyes had significant refractive error or the reading's confidence number was below the manufacturer's recommended value. Among Head Start preschool children, trained lay and nurse screeners agree well in measuring refractive error using the Retinomax or the SureSight. Both instruments had similar intertester agreement in refractive error measurements independent of the child's age. Significant refractive error and a reading with low confidence number were associated with worse intertester agreement.

Treating presbyopia without spectacles

NASA Astrophysics Data System (ADS)

Xu, Renfeng

Both multifocal optics and small pupils can increase the depth of focus (DoF) of presbyopes. This thesis will evaluate some of the unique challenges faced by each of these two strategies. First, there is no single spherical refracting lens that can focus all parts of the pupil of an aberrated eye. What is the objective and subjective spherical refractive error (Rx) for such an eye, and does it vary with the amount of primary SA? Using both computational modeling and psychophysical methods, we found that high levels of positive Seidel SA caused both objective and subjective refractions to become myopic. Significantly, this refractive shift varied with stimulus spatial frequency and subjective criterion. Second, although secondary SA can dramatically expand DoF, we show that this is mostly due to the lower order components within this polynomial, which can also change spherical Rx. Also, the r6 term that defines secondary SA actually narrows rather than expands DoF, when in the presence of the r4 term within Z60. Finally, as retinal illuminance drops, neural thresholds are elevated due to increased problems of photon noise. We asked if the gains in near and distant vision of presbyopes anticipated at high light levels would be cancelled or even reversed at low light levels because of the additional reduction in retinal illuminance contributed by small pupils. We found that when light levels are > 2 cd/m2, a small pupil with a diameter of 2--3mm improves near image quality, near visual acuity, and near reading speed without significant loss of distance image quality and distance vision. This result gains added significance because we also showed that low light level text in the urban environment always has luminance levels > 2 cd/m2. In conclusion, both small pupils and multifocal optics face significant challenges as near vision aids for presbyopes. However, some of the confounding effects of elevated SA levels are avoided by using small pupils to expand DoF, which can provide improved near and distance vision at most light levels encountered while reading.

Performance of Spot Photoscreener in Detecting Amblyopia Risk Factors in Chinese Pre-school and School Age Children Attending an Eye Clinic

PubMed Central

Mu, Yajun; Bi, Hua; Ekure, Edgar; Ding, Gang; Wei, Nan; Hua, Ning; Qian, Xuehan; Li, Xiaorong

2016-01-01

Purpose To evaluate the effectiveness of Spot photoscreener in detecting amblyopia risk factors meeting 2013 the American Association of Pediatric Ophthalmology and Strabismus (AAPOS) criteria in Chinese preschool and school-age children. Methods One hundred and fifty-five children (310 eyes), aged between 4 to 7 years (5.74 ± 1.2 years) underwent complete ophthalmologic examination, photoscreening, and cycloplegic retinoscopy refraction. The agreement of the results obtained with the photoscreening and retinoscopy was evaluated by linear regression and Bland-Altman plots. The sensitivity and specificity of detecting amblyopia risk factors were calculated based on the AAPOS 2013 guidelines. The overall effectiveness of detecting amblyopia risk factors was analyzed with Receiver Operating Characteristic (ROC) curves. Result The mean refractive errors measured with the Spot were: spherical equivalent (SE) = 0.70 ± 1.99 D, J0 = 0.87 ± 1.01 D, J45 = 0.09 ± 0.60 D. The mean results from retinoscopy were: SE = 1.19 ± 2.22 D, J0 = 0.77 ± 1.00 D, J45 = -0.02 ± 0.45 D. There was a strong linear agreement between results obtained from those two methods (R2 = 0.88, P<0.01). Bland–Altman plot indicated a moderate agreement of cylinder values between the two methods. Based on the criteria specified by the AAPOS 2013 guidelines, the sensitivity and specificity (in respective order) for detecting hyperopia were 98.31% and 97.14%; for detecting myopia were 78.50% and 88.64%; for detecting astigmatism were 90.91% and 80.37%; for detecting anisometropia were 93.10% and 85.25%; and for detection of strabismus was 77.55% and 88.18%. Conclusion The refractive values measured from Spot photoscreener showed a moderate agreement with the results from cycloplegic retinoscopy refraction, however there was an overall myopic shift of -0.49D. The performance in detecting individual amblyopia risk factors was satisfactory, but could be further improved by optimizing criteria based on ROC curves. PMID:26882106

Comparison of Toric Foldable Iris-Fixated Phakic Intraocular Lens Implantation and Limbal Relaxing Incisions for Moderate-to-High Myopic Astigmatism

PubMed Central

Lee, Jeihoon; Lee, Hun; Kang, David Sung Yong; Choi, Jin Young; Kim, Eung Kweon

2016-01-01

Purpose To compare the effectiveness of toric foldable iris-fixated phakic intraocular lens (pIOL) implantation and non-toric foldable iris-fixated pIOL implantation with limbal relaxing incisions (LRIs) for correcting moderate-to-high astigmatism in myopic eyes. Materials and Methods The medical records of 146 patients (195 eyes) with myopic astigmatism who underwent toric foldable iris-fixated pIOL implantation (toric group; 94 eyes) or non-toric foldable iris-fixated pIOL implantation with concurrent LRIs (LRI group; 101 eyes) were retrospectively reviewed. For subgroup analysis, the two groups were subdivided according to preoperative astigmatic severity [moderate, 2.00 to <3.00 diopters (D); high, 3.00–4.00 D]. Visual and astigmatic outcomes were compared 6 months postoperatively. Results The uncorrected distance visual acuity was at least 20/25 in 100% and 98% of the toric and LRI group eyes, respectively. The toric group had lower mean residual cylindrical error (-0.67±0.39 D vs. -1.14±0.56 D; p<0.001) and greater mean cylindrical error change (2.17±0.56 D vs. 1.63±0.72 D; p<0.001) than the LRI group, regardless of the preoperative astigmatic severity. The mean correction index (1.10±0.16 vs. 0.72±0.24; p<0.001) and success index (0.24±0.14 vs. 0.42±0.21; p<0.001) also differed significantly between the groups. Conclusion Both surgical techniques considerably reduced astigmatism and had comparable visual outcomes. However, toric foldable iris-fixated pIOL implantation was more reliable for correcting moderate-to-high astigmatism in myopic eyes. PMID:27593877

Comparison of Toric Foldable Iris-Fixated Phakic Intraocular Lens Implantation and Limbal Relaxing Incisions for Moderate-to-High Myopic Astigmatism.

PubMed

Lee, Jeihoon; Lee, Hun; Kang, David Sung Yong; Choi, Jin Young; Kim, Eung Kweon; Kim, Tae Im

2016-11-01

To compare the effectiveness of toric foldable iris-fixated phakic intraocular lens (pIOL) implantation and non-toric foldable iris-fixated pIOL implantation with limbal relaxing incisions (LRIs) for correcting moderate-to-high astigmatism in myopic eyes. The medical records of 146 patients (195 eyes) with myopic astigmatism who underwent toric foldable iris-fixated pIOL implantation (toric group; 94 eyes) or non-toric foldable iris-fixated pIOL implantation with concurrent LRIs (LRI group; 101 eyes) were retrospectively reviewed. For subgroup analysis, the two groups were subdivided according to preoperative astigmatic severity [moderate, 2.00 to <3.00 diopters (D); high, 3.00-4.00 D]. Visual and astigmatic outcomes were compared 6 months postoperatively. The uncorrected distance visual acuity was at least 20/25 in 100% and 98% of the toric and LRI group eyes, respectively. The toric group had lower mean residual cylindrical error (-0.67±0.39 D vs. -1.14±0.56 D; p<0.001) and greater mean cylindrical error change (2.17±0.56 D vs. 1.63±0.72 D; p<0.001) than the LRI group, regardless of the preoperative astigmatic severity. The mean correction index (1.10±0.16 vs. 0.72±0.24; p<0.001) and success index (0.24±0.14 vs. 0.42±0.21; p<0.001) also differed significantly between the groups. Both surgical techniques considerably reduced astigmatism and had comparable visual outcomes. However, toric foldable iris-fixated pIOL implantation was more reliable for correcting moderate-to-high astigmatism in myopic eyes.

Long-Term Clinical Outcomes of Myopic Patients Having Thin Residual Corneal Thickness after Excimer Laser Surface Ablation.

PubMed

Kocamış, Sücattin İlker; Çakmak, Hasan Basri; Gerçeker, Sıdıka; Çağıl, Nurullah

2017-01-01

To investigate and compare the long-term safety, efficacy, and accuracy of PRK (photorefractive keratectomy) and LASEK (laser epithelial keratomileusis) in myopic corneas having residual corneal thickness less than 400 micron meters (µm). The medical reports of the patients who had undergone excimer laser surface ablation between 2007-2011 and had a residual corneal thickness less than 400 µm were retrospectively reviewed. Forty-two eyes of 42 patients with a mean age of 28.79±7.76 years were enrolled into the study. Twenty-two PRK and 20 LASEK procedures were performed. The mean follow-up time was 45.00±11.80 months. At the end of follow-up, no ectasia was detected. Nineteen percent of eyes had trace haze. No eyes lost any lines in corrected distance visual acuity. Eighty-one percent of the patients had an uncorrected distance visual acuity better than 20/40. The regression rate was 16.7%. Sixty-two percent of eyes were within ±1.00 D. The safety and efficacy indexes were 1.19±0.42 and 1.00±0.40, respectively. There was not any difference between LASEK and PRK regarding achieved spherical equivalent refraction, haze ratio, visual acuity, safety, efficacy, and regression. Both PRK and LASEK are safe and effective in myopic corneas having thin residual thickness.