Peripheral refraction and image blur in four meridians in emmetropes and myopes.

PubMed

Shen, Jie; Spors, Frank; Egan, Donald; Liu, Chunming

2018-01-01

The peripheral refractive error of the human eye has been hypothesized to be a major stimulus for the development of its central refractive error. The purpose of this study was to investigate the changes in the peripheral refractive error across horizontal, vertical and two diagonal meridians in emmetropic and low, moderate and high myopic adults. Thirty-four adult subjects were recruited and aberration was measured using a modified commercial aberrometer. We then computed the refractive error in power vector notation from second-order Zernike terms. Statistical analysis was performed to evaluate the statistical differences in refractive error profiles between the subject groups and across all measured visual field meridians. Small amounts of relative myopic shift were observed in emmetropic and low myopic subjects. However, moderate and high myopic subjects exhibited a relative hyperopic shift in all four meridians. Astigmatism J 0 and J 45 had quadratic or linear changes dependent on the visual field meridians. Peripheral Sphero-Cylindrical Retinal Image Blur increased in emmetropic eyes in most of the measured visual fields. The findings indicate an overall emmetropic or slightly relative myopic periphery (spherical or oblate retinal shape) formed in emmetropes and low myopes, while moderate and high myopes form relative hyperopic periphery (prolate, or less oblate, retinal shape). In general, human emmetropic eyes demonstrate higher amount of peripheral retinal image blur.

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.

Relative Peripheral Refractive Error and the Risk of Onset and Progression of Myopia in Children

PubMed Central

Sinnott, Loraine T.; Mitchell, G. Lynn; 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 investigate whether relative peripheral hyperopia is a risk factor for either the onset of myopia in children or the rate of myopic progression. Methods. The risk of myopia onset was assessed in 2043 nonmyopic third-grade children (mean age ± SD = 8.8 ± 0.52 years) participating in the Collaborative Longitudinal Evaluation of Ethnicity and Refractive Error (CLEERE) Study between 1995 and 2007, 324 of whom became myopic by the eighth grade. Progression analyses used data from 774 myopic children in grades 1 to 8. Foveal and relative peripheral refractive error 30° in the nasal visual field was measured annually by using cycloplegic autorefraction. Axial length was measured by A-scan ultrasonography. Results. The association between more hyperopic relative peripheral refractive error in the third grade and the risk of the onset of myopia by the eighth grade varied by ethnic group (Asian children odds ratio [OR] = 1.56, 95% confidence interval [CI] = 1.06–2.30; African-American children OR = 0.75, 95% CI = 0.58–0.96; Hispanics, Native Americans, and whites showed no significant association). Myopia progression was greater per diopter of more hyperopic relative peripheral refractive error, but only by a small amount (−0.024 D per year; P = 0.02). Axial elongation was unrelated to the average relative peripheral refractive error (P = 0.77), regardless of ethnicity. Conclusions. Relative peripheral hyperopia appears to exert little consistent influence on the risk of the onset of myopic refractive error, on the rate of myopia progression, or on axial elongation. PMID:20739476

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

Ocular wavefront aberration and refractive error in pre-school children

NASA Astrophysics Data System (ADS)

Thapa, Damber; Fleck, Andre; Lakshminarayanan, Vasudevan; Bobier, William R.

2011-11-01

Hartmann-Shack images taken from an archived collection of SureSight refractive measurements of pre-school children in Oxford County, Ontario, Canada were retrieved and re-analyzed. Higher-order aberrations were calculated over the age range of 3 to 6 years. These higher-order aberrations were compared with respect to magnitudes of ametropia. Subjects were classified as emmetropic (range -0.5 to + 0.5D), low hyperopic (+ 0.5 to +2D) and high hyperopic (+2D or more) based upon the resulting spherical equivalent. Higher-order aberrations were found to increase with higher levels of hyperopia (p < 0.01). The strongest effect was for children showing more than +2.00D of hyperopia. The correlation coefficients were small in all of the higher-order aberrations; however, they were significant (p < 0.01). These analyses indicate a weak association between refractive error and higher-order aberrations in pre-school 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.

Refractive Errors in 3–6 Year-Old Chinese Children: A Very Low Prevalence of Myopia?

PubMed Central

Lin, Lixia; Li, Zhen; Zeng, Junwen; Yang, Zhikuan; Morgan, Ian G.

2013-01-01

Purpose To examine the prevalence of refractive errors in children aged 3–6 years in China. Methods 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. Results 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. Conclusions 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 yearsin most conditions. PMID:24205064

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.

Adjuvant corneal crosslinking to prevent hyperopic LASIK regression.

PubMed

Aslanides, Ioannis M; Mukherjee, Achyut N

2013-01-01

To report the long term outcomes, safety, stability, and efficacy in a pilot series of simultaneous hyperopic laser assisted in situ keratomileusis (LASIK) and corneal crosslinking (CXL). A small cohort series of five eyes, with clinically suboptimal topography and/or thickness, underwent LASIK surgery with immediate riboflavin application under the flap, followed by UV light irradiation. Postoperative assessment was performed at 1, 3, 6, and 12 months, with late follow up at 4 years, and results were compared with a matched cohort that received LASIK only. The average age of the LASIK-CXL group was 39 years (26-46), and the average spherical equivalent hyperopic refractive error was +3.45 diopters (standard deviation 0.76; range 2.5 to 4.5). All eyes maintained refractive stability over the 4 years. There were no complications related to CXL, and topographic and clinical outcomes were as expected for standard LASIK. This limited series suggests that simultaneous LASIK and CXL for hyperopia is safe. Outcomes of the small cohort suggest that this technique may be promising for ameliorating hyperopic regression, presumed to be biomechanical in origin, and may also address ectasia risk.

Is an objective refraction optimised using the visual Strehl ratio better than a subjective refraction?

PubMed Central

Hastings, Gareth D.; Marsack, Jason D.; Nguyen, Lan Chi; Cheng, Han; Applegate, Raymond A.

2017-01-01

Purpose To prospectively examine whether using the visual image quality metric, visual Strehl (VSX), to optimise objective refraction from wavefront error measurements can provide equivalent or better visual performance than subjective refraction and which refraction is preferred in free viewing. Methods Subjective refractions and wavefront aberrations were measured on 40 visually-normal eyes of 20 subjects, through natural and dilated pupils. For each eye a sphere, cylinder, and axis prescription was also objectively determined that optimised visual image quality (VSX) for the measured wavefront error. High contrast (HC) and low contrast (LC) logMAR visual acuity (VA) and short-term monocular distance vision preference were recorded and compared between the VSX-objective and subjective prescriptions both undilated and dilated. Results For 36 myopic eyes, clinically equivalent (and not statistically different) HC VA was provided with both the objective and subjective refractions (undilated mean ±SD was −0.06 ±0.04 with both refractions; dilated was −0.05 ±0.04 with the objective, and −0.05 ±0.05 with the subjective refraction). LC logMAR VA provided by the objective refraction was also clinically equivalent and not statistically different to that provided by the subjective refraction through both natural and dilated pupils for myopic eyes. In free viewing the objective prescription was preferred over the subjective by 72% of myopic eyes when not dilated. For four habitually undercorrected high hyperopic eyes, the VSX-objective refraction was more positive in spherical power and VA poorer than with the subjective refraction. Conclusions A method of simultaneously optimising sphere, cylinder, and axis from wavefront error measurements, using the visual image quality metric VSX, is described. In myopic subjects, visual performance, as measured by HC and LC VA, with this VSX-objective refraction was found equivalent to that provided by subjective refraction, and was typically preferred over subjective refraction. Subjective refraction was preferred by habitually undercorrected hyperopic eyes. PMID:28370389

Effects of Long-Wavelength Lighting on Refractive Development in Infant Rhesus Monkeys

PubMed Central

Smith, Earl L.; Hung, Li-Fang; Arumugam, Baskar; Holden, Brien A.; Neitz, Maureen; Neitz, Jay

2015-01-01

Purpose Differences in the spectral composition of lighting between indoor and outdoor scenes may contribute to the higher prevalence of myopia in children who spend low amounts of time outdoors. Our goal was to determine whether environments dominated by long-wavelength light promote the development of myopia. Methods Beginning at 25 ± 2 days of age, infant monkeys were reared with long-wavelength-pass (red) filters in front of one (MRL, n = 6) or both eyes (BRL, n = 7). The filters were worn continuously until 146 ± 7 days of age. Refractive development, corneal power, and vitreous chamber depth were assessed by retinoscopy, keratometry, and ultrasonography, respectively. Control data were obtained from 6 monkeys reared with binocular neutral density (ND) filters and 33 normal monkeys reared with unrestricted vision under typical indoor lighting. Results At the end of the filter-rearing period, the median refractive error for the BRL monkeys (+4.25 diopters [D]) was significantly more hyperopic than that for the ND (+2.22 D; P = 0.003) and normal monkeys (+2.38 D; P = 0.0001). Similarly, the MRL monkeys exhibited hyperopic anisometropias that were larger than those in normal monkeys (+1.70 ± 1.55 vs. −0.013 ± 0.33 D, P < 0.0001). The relative hyperopia in the treated eyes was associated with shorter vitreous chambers. Following filter removal, the filter-reared monkeys recovered from the induced hyperopic errors. Conclusions The observed hyperopic shifts indicate that emmetropization does not necessarily target the focal plane that maximizes luminance contrast and that reducing potential chromatic cues can interfere with emmetropization. There was no evidence that environments dominated by long wavelengths necessarily promote myopia development. PMID:26447984

Evaluation of internal refraction with the optical path difference scan.

PubMed

Muftuoglu, Orkun; Erdem, Uzeyir

2008-01-01

To evaluate internal refraction and its relation to other optical properties of the eye across a large range of refractive errors, which can provide useful information for the assessment and design of intraocular lenses and corneal ablation patterns. Cohort study. Three hundred ninety-four eyes of 197 healthy subjects with a mean age of 27+/-7 years (range, 18-42). All eyes underwent optical path difference scans to evaluate corneal topography, whole and internal ocular refraction (determined by the subtraction of corneal refraction from whole ocular refraction), and total and higher-order aberrations (HOAs) were assessed. After the conversion of any spherocylindrical refractive errors to vectorial data (sphere equivalent, blurring strength; cylinder, J(0) [power of Jackson cross cylinder at 90 degrees and 180 degrees] and J45 [power of Jackson cross cylinder at 45 degrees and 135 degrees]), the distribution of internal refraction among refraction groups (high myopes, low to moderate myopes, hyperopes, mixed astigmats, and emmetropes) and relationships between internal refraction, corneal refraction, and wavefront aberrations were analyzed. The compensation relation and its rate between corneal and internal astigmatism was assessed by the compensation factor (CF). Whole ocular power and astigmatism, corneal power and astigmatism, internal power and astigmatism, CF for astigmatic data, location of the highest internal refraction zone, and wavefront aberrations. The highest refraction zone was mostly (90%) located in the center in myopes, whereas it was located at the nasal side (71%) in hyperopes. There was a significant correlation between whole ocular and internal powers (P<0.01), but no correlation was observed between corneal and internal powers (P>0.05). Internal astigmatism was mostly against the rule. The mean CF J(0) was 0.63+/-3.78 and CF J(45) was 0.57+/-2.47. The magnitude of the internal astigmatism under the 3-mm zone was correlated with the magnitude of corneal astigmatism (P<0.05). The distribution of astigmatic CF differed among refraction groups. There were significant correlations between internal power and spherical aberration (P<0.05) and internal cylinder under the 5-mm zone and HOAs (P<0.001). There is a remarkable tilt in internal refraction in hyperopes. Although there is a tendency of undercompensation of the corneal astigmatism by internal astigmatism in the entire group of eyes, the compensation differs among refraction groups.

[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.

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.

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.

Longitudinal Development of Refractive Error in Children With Accommodative Esotropia: Onset, Amblyopia, and Anisometropia

PubMed Central

Wang, Jingyun; Morale, Sarah E.; Ren, Xiaowei; Birch, Eileen E.

2016-01-01

Purpose We investigated longitudinal changes of refractive error in children with accommodative esotropia (ET) throughout the first 12 years of life, its dependence on age at onset of ET, and whether amblyopia or anisometropia are associated with defective emmetropization. Methods Longitudinal refractive errors in children with accommodative ET were analyzed retrospectively. Eligibility criteria included: initial hyperopia ≥+4.00 diopters (D), initial cycloplegic refraction before 4 years, at least 3 visits, and at least one visit between 7 and 12 years. Children were classified as having infantile (N = 30; onset ≤12 months) or late-onset (N = 78; onset at 18–48 months) accommodative ET. Cycloplegic refractions culled from medical records were converted into spherical equivalent (SEQ). Results Although the initial visit right eye SEQ was similar for the infantile and late-onset groups (+5.86 ± 1.28 and +5.67 ± 1.26 D, respectively), there were different developmental changes in refractive error. Neither group had a significant decrease in hyperopia before age 7 years, but after 7 years, the infantile group experienced a myopic shift of −0.43 D/y. The late-onset group did not experience a myopic shift at 7 to 12 years. Among amblyopic children, a slower myopic shift was observed for the amblyopic eye. Among anisometropic children, the more hyperopic eye experienced more myopic shift than the less hyperopic eye. Conclusions Children with infantile accommodative ET experienced prolonged hyperopia followed by a myopic shift after 7 years of age, consistent with dissociation between infantile emmetropization and school age myopic shift. In contrast, children with late-onset accommodative ET had little myopic shift before or after 7 years. PMID:27116548

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.

Adjuvant corneal crosslinking to prevent hyperopic LASIK regression

PubMed Central

Aslanides, Ioannis M; Mukherjee, Achyut N

2013-01-01

Purpose To report the long term outcomes, safety, stability, and efficacy in a pilot series of simultaneous hyperopic laser assisted in situ keratomileusis (LASIK) and corneal crosslinking (CXL). Method A small cohort series of five eyes, with clinically suboptimal topography and/or thickness, underwent LASIK surgery with immediate riboflavin application under the flap, followed by UV light irradiation. Postoperative assessment was performed at 1, 3, 6, and 12 months, with late follow up at 4 years, and results were compared with a matched cohort that received LASIK only. Results The average age of the LASIK-CXL group was 39 years (26–46), and the average spherical equivalent hyperopic refractive error was +3.45 diopters (standard deviation 0.76; range 2.5 to 4.5). All eyes maintained refractive stability over the 4 years. There were no complications related to CXL, and topographic and clinical outcomes were as expected for standard LASIK. Conclusion This limited series suggests that simultaneous LASIK and CXL for hyperopia is safe. Outcomes of the small cohort suggest that this technique may be promising for ameliorating hyperopic regression, presumed to be biomechanical in origin, and may also address ectasia risk. PMID:23576861

[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.

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.

Is an objective refraction optimised using the visual Strehl ratio better than a subjective refraction?

PubMed

Hastings, Gareth D; Marsack, Jason D; Nguyen, Lan Chi; Cheng, Han; Applegate, Raymond A

2017-05-01

To prospectively examine whether using the visual image quality metric, visual Strehl (VSX), to optimise objective refraction from wavefront error measurements can provide equivalent or better visual performance than subjective refraction and which refraction is preferred in free viewing. Subjective refractions and wavefront aberrations were measured on 40 visually-normal eyes of 20 subjects, through natural and dilated pupils. For each eye a sphere, cylinder, and axis prescription was also objectively determined that optimised visual image quality (VSX) for the measured wavefront error. High contrast (HC) and low contrast (LC) logMAR visual acuity (VA) and short-term monocular distance vision preference were recorded and compared between the VSX-objective and subjective prescriptions both undilated and dilated. For 36 myopic eyes, clinically equivalent (and not statistically different) HC VA was provided with both the objective and subjective refractions (undilated mean ± S.D. was -0.06 ± 0.04 with both refractions; dilated was -0.05 ± 0.04 with the objective, and -0.05 ± 0.05 with the subjective refraction). LC logMAR VA provided by the objective refraction was also clinically equivalent and not statistically different to that provided by the subjective refraction through both natural and dilated pupils for myopic eyes. In free viewing the objective prescription was preferred over the subjective by 72% of myopic eyes when not dilated. For four habitually undercorrected high hyperopic eyes, the VSX-objective refraction was more positive in spherical power and VA poorer than with the subjective refraction. A method of simultaneously optimising sphere, cylinder, and axis from wavefront error measurements, using the visual image quality metric VSX, is described. In myopic subjects, visual performance, as measured by HC and LC VA, with this VSX-objective refraction was found equivalent to that provided by subjective refraction, and was typically preferred over subjective refraction. Subjective refraction was preferred by habitually undercorrected hyperopic eyes. © 2017 The Authors Ophthalmic & Physiological Optics © 2017 The College of Optometrists.

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.

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

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.

Optimized constants for an ultraviolet light-adjustable intraocular lens.

PubMed

Conrad-Hengerer, Ina; Dick, H Burkhard; Hütz, Werner W; Haigis, Wolfgang; Hengerer, Fritz H

2011-12-01

To determine the accuracy of intraocular lens (IOL) power calculations and to suggest adjusted constants for implantation of ultraviolet light-adjustable IOLs. Center for Vision Science, Ruhr University Eye Clinic, Bochum, Germany. Cohort study. Eyes with a visually significant cataract that had phacoemulsification with implantation of a light-adjustable IOL were evaluated. IOLMaster measurements were performed before phacoemulsification and IOL implantation and 4 weeks after surgery before the first adjustment of the IOL. The difference in the expected refraction and estimation error was studied. The study evaluated 125 eyes. Using the surgical constants provided by the manufacturer of the light-adjustable IOL, the SRK/T formula gave a more hyperopic refraction than the Hoffer Q and Holladay 1 formulas. The mean error of prediction was 0.93 diopter (D) ± 0.69 (SD), 0.91 ± 0.63 D, and 0.86 ± 0.65 D, respectively. The corresponding mean absolute error of prediction was 0.98 ± 0.61 D, 0.93 ± 0.61 D, and 0.90 ± 0.59 D, respectively. With optimized constants for the formulas, the mean error of prediction was 0.00 ± 0.63 D for Hoffer Q, 0.00 ± 0.64 D for Holladay 1, and 0.00 ± 0.66 D for SRK/T. The expected refraction after phacoemulsification and implantation of a light-adjustable IOL toward the hyperopic side of the desired refraction could be considered when using the optimized constants for all formulas. Copyright © 2011 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.

Pattern of refractive errors among the Nepalese population: a retrospective study.

PubMed

Shrestha, S P; Bhat, K S; Binu, V S; Barthakur, R; Natarajan, M; Subba, S H

2010-01-01

Refractive errors are a major cause of visual impairment in the population. To find the pattern of refractive errors among patients evaluated in a tertiary care hospital in the western region of Nepal. The present hospital-based retrospective study was conducted in the Department of Ophthalmology of the Manipal Teaching Hospital, situated in Pokhara, Nepal. Patients who had refractive error of at least 0.5 D (dioptre) were included for the study. During the study period, 15,410 patients attended the outpatient department and 10.8% of the patients were identified as having refractive error. The age of the patients in the present study ranged between 5 - 90 years. Myopia was the commonest refractive error followed by hypermetropia. There was no difference in the frequency of the type of refractive errors when they were defined using right the eye, the left eye or both the eyes. Males predominated among myopics and females predominated among hypermetropics. The majority of spherical errors was less than or equal to 2 D. Astigmatic power above 1D was rarely seen with hypermetropic astigmatism and was seen in around 13 % with myopic astigmatism. "Astigmatism against the rule" was more common than "astigmatism with the rule", irrespective of age. Refractive errors progressively shift along myopia up to the third decade and change to hypermetropia till the seventh decade. Hyperopic shift in the refractive error in young adults should be well noted while planning any refractive surgery in younger patients with myopia. © Nepal Ophthalmic Society.

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.

LASIK and PRK in hyperopic astigmatic eyes: is early retreatment advisable?

PubMed

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

2016-01-01

To analyze the refractive and keratometric stability in hyperopic astigmatic laser in situ keratomileusis (LASIK) or photorefractive keratectomy (PRK) during the first 6 months after surgery. This retrospective cross-sectional study included 97 hyperopic eyes; 55 were treated with LASIK and 42 with PRK. Excimer ablation for all eyes was performed using the ALLEGRETTO excimer laser platform using a mitomycin C for PRK and a mechanical microkeratome for LASIK. Keratometric and refractive data were analyzed during three consecutive follow-up intervals (6 weeks, 3 months, and 6 months). The corneal topography was obtained using Scheimpflug topography, and subjective refractions were acquired by expert optometrists according to a standardized protocol. After 3 months, mean keratometry and spherical equivalent were stable after LASIK, whereas PRK-treated eyes presented statistically significant (P<0.001) regression of hyperopia. In eleven cases, hyperopic regression of >1 D occurred. The optical zone diameter did not correlate with the development of regression. After corneal laser refractive surgery, keratometric changes are followed by refractive changes and they occur up to 6 months after LASIK and for at least 6 months after PRK, and therefore, caution should be applied when retreatment is planned during the 1st year after surgery because hyperopic refractive regression can lead to suboptimal visual outcome. Keratometric and refractive stability is earlier achieved after LASIK, and therefore, retreatment may be independent of late regression.

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

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

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.

Eye Shape Using Partial Coherence Interferometry, Autorefraction and SD OCT

PubMed Central

Clark, Christopher A.; Elsner, Ann E.; Konynenbelt, Benjamin J.

2015-01-01

Purpose Peripheral refraction and retinal shape may influence refractive development. Peripheral refraction has been shown to have a high degree of variability and can take considerable time to perform. SD OCT and peripheral axial length measures may be more reliable, assuming that the retinal position is more important than the peripheral optics of the lens/cornea. Methods 79 subjects right eyes were imaged for this study (age range: 22 to 34 yr, refractive error: −10 to +5.00.) Thirty deg SD OCT (Spectralis, Heidleberg) images were collected in a radial pattern along with peripheral refraction with an autorefractor (Shin-Nippon Auto-refractor) and peripheral axial length measurements with partial coherence interferometry (PCI) (IOLmaster, Zeiss). Statistics were performed using repeat measures ANOVA in SPSS (IBM), Bland-Altman analyses, and regression. All measures were converted to diopters to allow direct comparison. Results SD OCT showed a retinal shape with an increased curvature for myopes compared to emmetropes/hyperopes. This retinal shape change became significant around 5 deg. The SD OCT analysis for retinal shape provides a resolution of 0.026 dipopters, which is about ten times more accurate than using autorefraction or clinical refractive techniques. Bland-Altman analyses suggest that retinal shape measured by SD OCT and the PCI method were more consistent with one another than either was with AR. Conclusions With more accurate measures of retinal shape using SD OCT, consistent differences between emmetrope/hyperopes and myopes were found nearer to the fovea than previously reported. Retinal shape may be influenced by central refractive error, and not merely peripheral optics. Partial coherence interferometry and SD OCT appear to be more accurate than autorefraction, which may be influenced other factors such as fixation and accommodation. Autorefraction does measure the optics directly, which may be a strength of that method. PMID:25437906

Why Do Only Some Hyperopes Become Strabismic?

PubMed Central

Babinsky, Erin; Candy, T. Rowan

2013-01-01

Children with hyperopia greater than +3.5 diopters (D) are at increased risk for developing refractive esotropia. However, only approximately 20% of these hyperopes develop strabismus. This review provides a systematic theoretical analysis of the accommodation and vergence oculomotor systems with a view to understanding factors that could either protect a hyperopic individual or precipitate a strabismus. The goal is to consider factors that may predict refractive esotropia in an individual and therefore help identify the subset of hyperopes who are at the highest risk for this strabismus, warranting the most consideration in a preventive effort PMID:23883788

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

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

Refractive error change and vision improvement in moderate to severe hyperopic amblyopia after spectacle correction: Restarting the emmetropization process?

PubMed

Chang, Ji Woong

2017-01-01

The aims of the study were to develop guidelines for prescribing spectacles for patients with moderate to severe hyperopic amblyopia and to demonstrate how emmetropization progresses. Children with hyperopic amblyopia who had a spherical equivalent of ≥ +4.0 diopters (D) or more were included, while those who had astigmatism of > 2.0 D or anisometropia of > 2.0 D were excluded. The patients were divided into a full correction group and an under-correction group according to the amount of hyperopia correction applied. The under-correction group was further subdivided into a fixed under-correction group and a post-cycloplegic refraction (PCR) under-correction group. The duration of amblyopia treatment and changes in initial hyperopia were compared between the groups. In total, 76 eyes of 38 patients were analyzed in this study. The full correction group and under-correction group were subjected to 5.5 months and 5.9 months of amblyopia treatment, respectively (P = 0.570). However, the PCR under-correction group showed more rapid improvement (2.9 months; P = 0.001). In the under-correction group, initial hyperopia was decreased by -0.28 D and -0.49 D at 6 months and 12 months, respectively, after initial cycloplegic refraction. Moreover, the amount of hyperopia under-correction was correlated with the amount of hyperopia reduction (P = 0.010). The under-correction of moderate to severe hyperopic amblyopia has beneficial effects for treating amblyopia and activating emmetropization. PCR under-correction can more rapidly improve visual acuity, while both fixed under-correction and PCR under-correction can induce emmetropization and effectively reduce initial hyperopia.

Wound healing profiles of hyperopic-small incision lenticule extraction (SMILE)

PubMed Central

Liu, Yu-Chi; Ang, Heng Pei; Teo, Ericia Pei Wen; Lwin, Nyein Chan; Yam, Gary Hin Fai; Mehta, Jodhbir S.

2016-01-01

Refractive surgical treatment of hyperopia still remains a challenge for refractive surgeons. A new nomogram of small incision lenticule extraction (SMILE) procedure has recently been developed for the treatment of hyperopia. In the present study, we aimed to evaluate the wound healing and inflammatory responses of this new nomogram (hyperopic-SMILE), and compared them to those of hyperopic-laser-assisted in situ keratomileusis (LASIK), using a rabbit model. A total of 26 rabbits were used, and slit lamp biomicroscopy, autorefractor/keratometer, intraocular pressure measurement, anterior segment optical coherence tomography, corneal topography, and in vivo confocal microscopy examinations were performed during the study period of 4 weeks. The corneas were then harvested and subject to immunofluorescence of markers for inflammation (CD11b), wound healing (fibronectin) and keratocyte response (HSP47). The lenticule ultrastructual changes were also analyzed by transmission electron microscopy. Out results showed that hyperopic-SMILE effectively steepened the cornea. Compared to hyperopic-LASIK, hyperopic-SMILE had less postoperative wound healing response and stromal interface reaction, especially in higher refractive correction. However, compared to myopic-SMILE, hyperopic-SMILE resulted in more central deranged collagen fibrils. These results provide more perspective into this new treatment option for hyperopia, and evidence for future laser nomogram modification. PMID:27418330

Excimer laser correction of hyperopia, hyperopic and mixed astigmatism: past, present, and future.

PubMed

Lukenda, Adrian; Martinović, Zeljka Karaman; Kalauz, Miro

2012-06-01

The broad acceptance of "spot scanning" or "flying spot" excimer lasers in the last decade has enabled the domination of corneal ablative laser surgery over other refractive surgical procedures for the correction of hyperopia, hyperopic and mixed astigmatism. This review outlines the most important reasons why the ablative laser correction of hyperopia, hyperopic and mixed astigmatism for many years lagged behind that of myopia. Most of today's scanning laser systems, used in the LASIK and PRK procedures, can safely and effectively perform low, moderate and high hyperopic and hyperopic astigmatic corrections. The introduction of these laser platforms has also significantly improved the long term refractive stability of hyperopic treatments. In the future, further improvements in femtosecond and nanosecond technology, eye-tracker systems, and the development of new customized algorithms, such as the ray-tracing method, could additionally increase the upper limit for the safe and predictable corneal ablative laser correction ofhyperopia, hyperopic and mixed astigmatism.

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.

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

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.

Receding and disparity cues aid relaxation of accommodation

PubMed Central

Horwood, Anna M; Riddell, Patricia M

2015-01-01

Purpose Accommodation can mask hyperopia and reduce the accuracy of non-cycloplegic refraction. It is therefore important to minimize accommodation to obtain as accurate a measure of hyperopia as possible. In order to characterize the parameters required to measure the maximally hyperopic error using photorefraction, we used different target types and distances to determine which target was most likely to maximally relax accommodation and thus more accurately detect hyperopia in an individual. Methods A PlusoptiX SO4 infra-red photorefractor was mounted in a remote haploscope which presented the targets. All participants were tested with targets at four fixation distances between 0.3m and 2m containing all combinations of blur, disparity and proximity/looming cues. 38 infants (6-44 wks) were studied longitudinally, and 104 children (4 -15 yrs (mean 6.4)) and 85 adults, with a range of refractive errors and binocular vision status, were tested once. Cycloplegic refraction data was available for a sub-set of 59 participants spread across the age range. Results The maximally hyperopic refraction (MHR) found at any time in the session was most frequently found when fixating the most distant targets and those containing disparity and dynamic proximity/looming cues. Presence or absence of blur was less significant, and targets in which only single cues to depth were present were also less likely to produce MHR. MHR correlated closely with cycloplegic refraction (r = 0.93,mean difference 0.07D,p=n.s.,95%CI ±<0.25D) after correction by a calibration factor. Conclusion Maximum relaxation of accommodation occurred for binocular targets receding into the distance. Proximal and disparity cues aid relaxation of accommodation to a greater extent than blur, and thus non-cycloplegic refraction targets should incorporate these cues. This is especially important in screening contexts with a brief opportunity to test for significant hyperopia. MHR in our laboratory was found to be a reliable estimation of cycloplegic refraction. PMID:19770814

Eye shape using partial coherence interferometry, autorefraction, and SD-OCT.

PubMed

Clark, Christopher A; Elsner, Ann E; Konynenbelt, Benjamin J

2015-01-01

Peripheral refraction and retinal shape may influence refractive development. Peripheral refraction has been shown to have a high degree of variability and can take considerable time to perform. Spectral domain optical coherence tomography (SD-OCT) and peripheral axial length measures may be more reliable, assuming that the retinal position is more important than the peripheral optics of the lens/cornea. Seventy-nine subjects' right eyes were imaged for this study (age range, 22 to 34 years; refractive error, -10 to +5.00). Thirty-degree SD-OCT (Spectralis, Heidelberg Engineering, Heidelberg, Germany) images were collected in a radial pattern along with peripheral refraction with an autorefractor (Shin-Nippon Autorefractor) and peripheral axial length measurements with partial coherence interferometry (IOLMaster, Zeiss). Statistics were performed using repeated-measures analysis of variance in SPSS (IBM, Armonk, NY), Bland-Altman analyses, and regression. All measures were converted to diopters to allow direct comparison. Spectral domain OCT showed a retinal shape with an increased curvature for myopes compared with emmetropes/hyperopes. This retinal shape change became significant around 5 degrees. The SD-OCT analysis for retinal shape provides a resolution of 0.026 diopters, which is about 10 times more accurate than using autorefraction (AR) or clinical refractive techniques. Bland-Altman analyses suggest that retinal shape measured by SD-OCT and the partial coherence interferometry method were more consistent with one another than either was with AR. With more accurate measures of retinal shape using SD-OCT, consistent differences between emmetropes/hyperopes and myopes were found nearer to the fovea than previously reported. Retinal shape may be influenced by central refractive error, and not merely peripheral optics. Partial coherence interferometry and SD-OCT appear to be more accurate than AR, which may be influenced by other factors such as fixation and accommodation. Autorefraction does measure the optics directly, which may be a strength of that method.

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.

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.

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.

Role of preoperative cycloplegic refraction in LASIK treatment of hyperopia.

PubMed

Frings, Andreas; Steinberg, Johannes; Druchkiv, Vasyl; Linke, Stephan J; Katz, Toam

2016-07-01

Previous studies have suggested that, to improve refractive predictability in hyperopic LASIK treatments, preoperative cycloplegic or manifest refraction, or a combination of both, could be used in the laser nomogram. We set out to investigate (1) the prevalence of a high difference between manifest and cycloplegic spherical equivalent in hyperopic eyes preoperatively, and (2) the related predictability of postoperative keratometry. Retrospective cross-sectional data analysis of consecutive treated 186 eyes from 186 consecutive hyperopic patients (mean age 42 [±12] years) were analyzed. Excimer ablation for all eyes was performed using a mechanical microkeratome (SBK, Moria, France) and an Allegretto excimer laser platform. Two groups were defined according to the difference between manifest and cycloplegic spherical equivalent which was defined as ≥1.00 diopter (D); the data was analyzed according to refractive outcome in terms of refractive predictability, efficacy, and safety. In 24 eyes (13 %), a preoperative difference of ≥1.00D between manifest spherical equivalent and cycloplegic spherical equivalent (= MCD) occurred. With increasing preoperative MCD, the postoperative achieved spherical equivalent showed hyperopic regression after 3 months. There was no statistically significant effect of age (accommodation) or optical zone size on the achieved spherical equivalent. A difference of ≥1.00D occurs in about 13 % of hyperopia cases. We suggest that hyperopic correction should be based on the manifest spherical equivalent in eyes with preoperative MCD <1.00D. If the preoperative MCD is ≥1.00D, treatment may produce manifest undercorrection, and therefore we advise that the patient should be warrned about lower predictability, and suggest basing conclusions on the arithmetic mean calculated from the preoperative manifest and cycloplegic spheres.

The Relationship between Crystalline Lens Power and Refractive Error in Older Chinese Adults: The Shanghai Eye Study.

PubMed

He, Jiangnan; Lu, Lina; He, Xiangui; Xu, Xian; Du, Xuan; Zhang, Bo; Zhao, Huijuan; Sha, Jida; Zhu, Jianfeng; Zou, Haidong; Xu, Xun

2017-01-01

To report calculated crystalline lens power and describe the distribution of ocular biometry and its association with refractive error in older Chinese adults. Random clustering sampling was used to identify adults aged 50 years and above in Xuhui and Baoshan districts of Shanghai. Refraction was determined by subjective refraction that achieved the best corrected vision based on monocular measurement. Ocular biometry was measured by IOL Master. The crystalline lens power of right eyes was calculated using modified Bennett-Rabbetts formula. We analyzed 6099 normal phakic right eyes. The mean crystalline lens power was 20.34 ± 2.24D (range: 13.40-36.08). Lens power, spherical equivalent, and anterior chamber depth changed linearly with age; however, axial length, corneal power and AL/CR ratio did not vary with age. The overall prevalence of hyperopia, myopia, and high myopia was 48.48% (95% CI: 47.23%-49.74%), 22.82% (95% CI: 21.77%-23.88%), and 4.57% (95% CI: 4.05-5.10), respectively. The prevalence of hyperopia increased linearly with age while lens power decreased with age. In multivariate models, refractive error was strongly correlated with axial length, lens power, corneal power, and anterior chamber depth; refractive error was slightly correlated with best corrected visual acuity, age and sex. Lens power, hyperopia, and spherical equivalent changed linearly with age; Moreover, the continuous loss of lens power produced hyperopic shifts in refraction in subjects aged more than 50 years.

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.

Gradients of refractive index in the crystalline lens and transient changes in refraction among patients with diabetes.

PubMed

Charman, W Neil; Adnan; Atchison, David A

2012-12-01

Transient hyperopic refractive shifts occur on a timescale of weeks in some patients after initiation of therapy for hyperglycemia, and are usually followed by recovery to the original refraction. Possible lenticular origin of these changes is considered in terms of a paraxial gradient index model. Assuming that the lens thickness and curvatures remain unchanged, as observed in practice, it appears possible to account for initial hyperopic refractive shifts of up to a few diopters by reduction in refractive index near the lens center and alteration in the rate of change between center and surface, so that most of the index change occurs closer to the lens surface. Restoration of the original refraction depends on further change in the refractive index distribution with more gradual changes in refractive index from the lens center to its surface. Modeling limitations are discussed.

Gradients of refractive index in the crystalline lens and transient changes in refraction among patients with diabetes

PubMed Central

Charman, W. Neil; Adnan; Atchison, David A.

2012-01-01

Transient hyperopic refractive shifts occur on a timescale of weeks in some patients after initiation of therapy for hyperglycemia, and are usually followed by recovery to the original refraction. Possible lenticular origin of these changes is considered in terms of a paraxial gradient index model. Assuming that the lens thickness and curvatures remain unchanged, as observed in practice, it appears possible to account for initial hyperopic refractive shifts of up to a few diopters by reduction in refractive index near the lens center and alteration in the rate of change between center and surface, so that most of the index change occurs closer to the lens surface. Restoration of the original refraction depends on further change in the refractive index distribution with more gradual changes in refractive index from the lens center to its surface. Modeling limitations are discussed. PMID:23243557

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.

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 effects of glycemic control on ophthalmic refraction in diabetic patients].

PubMed

Li, Hai-yan; Luo, Guo-chun; Guo, Jiang; Liang, Zhen

2010-10-01

To evaluate effects of glycemic control on refraction in diabetic patients. Twenty newly diagnosed diabetic patients were included in this study. The random blood glucose, glycosylated hemoglobin A1c (HbA1c) levels, fasting C-peptide and postprandial 2 h C-peptide levels were measured before treatment. The patients with random blood glucose ≥ 12.0 mmol/L and HbA1c ≥ 10.0% were selected. Refraction, intraocular pressure, radius of the anterior corneal curvature, depth of the anterior chamber, lens thickness, vitreous length, and axial length were measured on admission and at the end of week 1, 2, 3 and 4 during glycaemic control. A transient hyperopic change occurred in all the patients receiving glycemic control with a mean maximum hyperopic changes of 1.6 D (0.50 D ∼ 3.20 D). There was a positive correlation between the magnitude of the maximum hyperopic changes and the HbA1c levels on admission (r = 0.84, P < 0.05). There was a positive correlation between the magnitude of the maximum hyperopic changes and the daily rate of blood glucose reduction over the first 7 days of the treatment (r = 0.53, P < 0.05). There was no significant correlation between the magnitude of the maximum hyperopic changes and the levels of random blood glucose on admission. No significant correlation was observed between the maximum hyperopic changes and fasting C-peptide or postprandial 2 h C-peptide. There were no significant correlations between the magnitude of the maximum hyperopic changes and age, blood press, body mass index, triglyceride, total cholesterol, low-density lipoprotein or high-density lipoprotein. No significant changes were observed in the intraocular pressure, radius of the anterior corneal curvature, depth of the anterior chamber, lens thickness, vitreous length and axial length during glycemic control. Transient hyperopic changes occur after glycemic control in diabetic patients with severe hyperglycaemia. The degrees of transient hyperopia are highly dependent on HbA1c levels before treatment and the rate of reduction of glucose level over the first 7 days of treatment. This is probably due to the decrease of refractive power by lens hydration, not morphological change of lens.

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.

The Relationship between Crystalline Lens Power and Refractive Error in Older Chinese Adults: The Shanghai Eye Study

PubMed Central

He, Jiangnan; Lu, Lina; He, Xiangui; Xu, Xian; Du, Xuan; Zhang, Bo; Zhao, Huijuan; Sha, Jida; Zhu, Jianfeng; Zou, Haidong; Xu, Xun

2017-01-01

Purpose To report calculated crystalline lens power and describe the distribution of ocular biometry and its association with refractive error in older Chinese adults. Methods Random clustering sampling was used to identify adults aged 50 years and above in Xuhui and Baoshan districts of Shanghai. Refraction was determined by subjective refraction that achieved the best corrected vision based on monocular measurement. Ocular biometry was measured by IOL Master. The crystalline lens power of right eyes was calculated using modified Bennett-Rabbetts formula. Results We analyzed 6099 normal phakic right eyes. The mean crystalline lens power was 20.34 ± 2.24D (range: 13.40–36.08). Lens power, spherical equivalent, and anterior chamber depth changed linearly with age; however, axial length, corneal power and AL/CR ratio did not vary with age. The overall prevalence of hyperopia, myopia, and high myopia was 48.48% (95% CI: 47.23%–49.74%), 22.82% (95% CI: 21.77%–23.88%), and 4.57% (95% CI: 4.05–5.10), respectively. The prevalence of hyperopia increased linearly with age while lens power decreased with age. In multivariate models, refractive error was strongly correlated with axial length, lens power, corneal power, and anterior chamber depth; refractive error was slightly correlated with best corrected visual acuity, age and sex. Conclusion Lens power, hyperopia, and spherical equivalent changed linearly with age; Moreover, the continuous loss of lens power produced hyperopic shifts in refraction in subjects aged more than 50 years. PMID:28114313

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.

Refractive ocular conditions and reasons for spectacles renewal in a resource-limited economy

PubMed Central

2010-01-01

Background Although a leading cause of visual impairment and a treatable cause of blindness globally, the pattern of refractive errors in many populations is unknown. This study determined the pattern of refractive ocular conditions, reasons for spectacles renewal and the effect of correction on refractive errors in a resource-limited community. Methods A retrospective review of case records of 1,413 consecutive patients seen in a private optometry practice, Nigeria between January 2006 and July 2007. Results A total number of 1,216 (86.1%) patients comprising of (486, 40%) males and (730, 60%) females with a mean age of 41.02 years SD 14.19 were analyzed. The age distribution peaked at peri-adolescent and the middle age years. The main ocular complaints were spectacles loss and discomfort (412, 33.9%), blurred near vision (399, 32.8%) and asthenopia (255, 20.9%). The mean duration of ocular symptoms before consultation was 2.05 years SD 1.92. The most common refractive errors include presbyopia (431, 35.3%), hyperopic astigmatism (240, 19.7%) and presbyopia with hyperopia (276, 22.7%). Only (59, 4.9%) had myopia. Following correction, there were reductions in magnitudes of the blind (VA<3/60) and visually impaired (VA<6/18-3/60) patients by (18, 58.1%) and (89, 81.7%) respectively. The main reasons for renewal of spectacles were broken lenses/frame/scratched lenses/lenses' falling off (47, 63.4%). Conclusions Adequate correction of refractive errors reduces visual impairment and avoidable blindness and to achieve optimal control of refractive errors in the community, services should be targeted at individuals in the peri-adolescent and the middle age years. PMID:20459676

Refractive ocular conditions and reasons for spectacles renewal in a resource-limited economy.

PubMed

Ayanniyi, Abdulkabir A; Folorunso, Francisca N; Adepoju, Feyisayo G

2010-05-07

Although a leading cause of visual impairment and a treatable cause of blindness globally, the pattern of refractive errors in many populations is unknown. This study determined the pattern of refractive ocular conditions, reasons for spectacles renewal and the effect of correction on refractive errors in a resource-limited community. A retrospective review of case records of 1,413 consecutive patients seen in a private optometry practice, Nigeria between January 2006 and July 2007. A total number of 1,216 (86.1%) patients comprising of (486, 40%) males and (730, 60%) females with a mean age of 41.02 years SD 14.19 were analyzed. The age distribution peaked at peri-adolescent and the middle age years. The main ocular complaints were spectacles loss and discomfort (412, 33.9%), blurred near vision (399, 32.8%) and asthenopia (255, 20.9%). The mean duration of ocular symptoms before consultation was 2.05 years SD 1.92. The most common refractive errors include presbyopia (431, 35.3%), hyperopic astigmatism (240, 19.7%) and presbyopia with hyperopia (276, 22.7%). Only (59, 4.9%) had myopia. Following correction, there were reductions in magnitudes of the blind (VA<3/60) and visually impaired (VA<6/18-3/60) patients by (18, 58.1%) and (89, 81.7%) respectively. The main reasons for renewal of spectacles were broken lenses/frame/scratched lenses/lenses' falling off (47, 63.4%). Adequate correction of refractive errors reduces visual impairment and avoidable blindness and to achieve optimal control of refractive errors in the community, services should be targeted at individuals in the peri-adolescent and the middle age years.

Refractive errors and strabismus in Down's syndrome in Korea.

PubMed

Han, Dae Heon; Kim, Kyun Hyung; Paik, Hae Jung

2012-12-01

The aims of this study were to examine the distribution of refractive errors and clinical characteristics of strabismus in Korean patients with Down's syndrome. A total of 41 Korean patients with Down's syndrome were screened for strabismus and refractive errors in 2009. A total of 41 patients with an average age of 11.9 years (range, 2 to 36 years) were screened. Eighteen patients (43.9%) had strabismus. Ten (23.4%) of 18 patients exhibited esotropia and the others had intermittent exotropia. The most frequently detected type of esotropia was acquired non-accommodative esotropia, and that of exotropia was the basic type. Fifteen patients (36.6%) had hypermetropia and 20 (48.8%) had myopia. The patients with esotropia had refractive errors of +4.89 diopters (D, ±3.73) and the patients with exotropia had refractive errors of -0.31 D (±1.78). Six of ten patients with esotropia had an accommodation weakness. Twenty one patients (63.4%) had astigmatism. Eleven (28.6%) of 21 patients had anisometropia and six (14.6%) of those had clinically significant anisometropia. In Korean patients with Down's syndrome, esotropia was more common than exotropia and hypermetropia more common than myopia. Especially, Down's syndrome patients with esotropia generally exhibit clinically significant hyperopic errors (>+3.00 D) and evidence of under-accommodation. Thus, hypermetropia and accommodation weakness could be possible factors in esotropia when it occurs in Down's syndrome patients. Based on the results of this study, eye examinations of Down's syndrome patients should routinely include a measure of accommodation at near distances, and bifocals should be considered for those with evidence of under-accommodation.

Cycloplegic Refraction in Hyperopic Children: Effectiveness of a 0.5% Tropicamide and 0.5% Phenylephrine Addition to 1% Cyclopentolate Regimen.

PubMed

Yoo, Seul Gi; Cho, Myung Jin; Kim, Ungsoo Samuel; Baek, Seung Hee

2017-06-01

To evaluate the effectiveness of a cycloplegic regimen using 0.5% tropicamide and 0.5% phenylephrine (Tropherine, Hanmi Pharm), in addition to 1% cyclopentolate, in hyperopic children. The medical records of hyperopic patients below the age of 14 years who had undergone cycloplegic retinoscopy were retrospectively reviewed. Cycloplegic refractions were performed using one of two cycloplegic regimens. Regimen 1 was a Tropherine-added regimen comprising the administration of one drop of 1% cyclopentolate followed by two to three drops of Tropherine added at 15-minute intervals. Regimen 2 was a cyclopentolate-only regimen comprising the administration of three to four drops of 1% cyclopentolate at 15-minute intervals. The mean difference between noncycloplegic and cycloplegic refraction was compared between the two regimens. A total of 308 eyes of 308 hyperopic children were included. The mean difference (±standard deviation) in the spherical equivalent (SE) between cycloplegic and noncycloplegic refraction was significantly larger in regimen 2 than in regimen 1, with values of +1.70 ± 1.03 diopters (D) and +1.25 ± 0.89 D, respectively (p=0.001). The SE change after cycloplegia was significantly different between the two regimens only in patients aged 5 years or younger (p=0.001), particularly in those with high hyperopia with an SE ≥5 D (p=0.005) or fully accommodative esotropia (p=0.009). There was no significant difference between the two regimens in patients older than 5 years, regardless of the presence of high hyperopia or fully accommodative esotropia. The Tropherine-added regimen exerted a weaker cycloplegic effect than the cyclopentolate-only regimen, particularly in children under the age of 5 years with high hyperopia or fully accommodative esotropia. However, the difference in refraction between the two regimens was small. A Tropherine-added regimen can be effective in hyperopic children, with less associated discomfort than the instillation of cyclopentolate. © 2017 The Korean Ophthalmological Society

Cycloplegic Refraction in Hyperopic Children: Effectiveness of a 0.5% Tropicamide and 0.5% Phenylephrine Addition to 1% Cyclopentolate Regimen

PubMed Central

Yoo, Seul Gi; Cho, Myung Jin; Kim, Ungsoo Samuel

2017-01-01

Purpose To evaluate the effectiveness of a cycloplegic regimen using 0.5% tropicamide and 0.5% phenylephrine (Tropherine, Hanmi Pharm), in addition to 1% cyclopentolate, in hyperopic children. Methods The medical records of hyperopic patients below the age of 14 years who had undergone cycloplegic retinoscopy were retrospectively reviewed. Cycloplegic refractions were performed using one of two cycloplegic regimens. Regimen 1 was a Tropherine-added regimen comprising the administration of one drop of 1% cyclopentolate followed by two to three drops of Tropherine added at 15-minute intervals. Regimen 2 was a cyclopentolate-only regimen comprising the administration of three to four drops of 1% cyclopentolate at 15-minute intervals. The mean difference between noncycloplegic and cycloplegic refraction was compared between the two regimens. Results A total of 308 eyes of 308 hyperopic children were included. The mean difference (±standard deviation) in the spherical equivalent (SE) between cycloplegic and noncycloplegic refraction was significantly larger in regimen 2 than in regimen 1, with values of +1.70 ± 1.03 diopters (D) and +1.25 ± 0.89 D, respectively (p=0.001). The SE change after cycloplegia was significantly different between the two regimens only in patients aged 5 years or younger (p=0.001), particularly in those with high hyperopia with an SE ≥5 D (p=0.005) or fully accommodative esotropia (p=0.009). There was no significant difference between the two regimens in patients older than 5 years, regardless of the presence of high hyperopia or fully accommodative esotropia. Conclusions The Tropherine-added regimen exerted a weaker cycloplegic effect than the cyclopentolate-only regimen, particularly in children under the age of 5 years with high hyperopia or fully accommodative esotropia. However, the difference in refraction between the two regimens was small. A Tropherine-added regimen can be effective in hyperopic children, with less associated discomfort than the instillation of cyclopentolate. PMID:28471102

The Influence of Different OK Lens Designs on Peripheral Refraction.

PubMed

Kang, Pauline; Swarbrick, Helen

2016-09-01

To compare peripheral refraction changes along the horizontal and vertical meridians induced by three different orthokeratology (OK) lens designs: BE, Paragon CRT, and Contex lenses. Nineteen subjects (6M, 13F, mean age 28 ± 7 years) were initially fitted with BE OK lenses in both eyes which were worn overnight for 14 days. Central and peripheral refraction and corneal topography were measured at baseline and after 14 nights of lens wear. After a minimum 2-week washout period, one randomly selected eye was re-fitted with a Paragon CRT lens and the other eye with a Contex OK lens. Measurements were repeated before and after 14 nights of lens wear. The three different OK lenses caused significant changes in peripheral refraction along both the horizontal and vertical visual fields (VFs). BE and Paragon CRT lenses induced a significant hyperopic shift within the central ±20° along the horizontal VF and at all positions along the vertical meridian except at 30° in the superior VF. There were no significant differences in peripheral refraction changes induced between BE and Paragon CRT lenses. When comparing BE and Contex OK lens designs, BE caused greater hyperopic shifts at 10° and 30° in the temporal VF and at center, 10°, and 20° in the superior VF along the vertical meridian. Furthermore, BE lenses caused greater reduction in Flat and Steep K values compared to Contex OK. OK lenses induced significant changes in peripheral refraction along the horizontal and vertical meridians. Despite the clinically significant difference in central corneal flattening induced by BE and Contex OK lenses, relative peripheral refraction changes differed minimally between the three OK lens designs. If the peripheral retina influences refractive error development, these results suggest that myopia control effects are likely to be similar between different OK lens designs.

Refractive errors, visual impairment, and the use of low-vision devices in albinism in Malawi.

PubMed

Schulze Schwering, M; Kumar, N; Bohrmann, D; Msukwa, G; Kalua, K; Kayange, P; Spitzer, M S

2015-04-01

This study focuses on the refractive implications of albinism in Malawi, which is mostly associated with the burden of visual impairment. The main goal was to describe the refractive errors and to analyze whether patients with albinism in Malawi, Sub-Saharan Africa, benefit from refraction. Age, sex, refractive data, uncorrected and best-corrected visual acuity (UCVA, BCVA), colour vision, contrast sensitivity, and the prescription of sunglasses and low vision devices were collected for a group of 120 albino individuals with oculocutaneous albinism (OCA). Refractive errors were evaluated objectively and subjectively by retinoscopy, and followed by cycloplegic refraction to reconfirm the results. Best-corrected visual acuity (BCVA) was also assessed binocularly. One hundred and twenty albino subjects were examined, ranging in age from 4 to 25 years (median 12 years), 71 (59 %) boys and 49 (41 %) girls. All exhibited horizontal pendular nystagmus. Mean visual acuity improved from 0.98 (0.33) logMAR to 0.77 (0.15) logMAR after refraction (p < 0.001). The best improvement of VA was achieved in patients with mild to moderate myopia. Patients with albinism who were hyperopic more than +1.5 D hardly improved from refraction. With the rule (WTR) astigmatism was more present (37.5 %) than against the rule (ATR) astigmatism (3.8 %). Patients with astigmatism less than 1.5 D improved in 15/32 of cases (47 %) by 2 lines or more. Patients with astigmatism equal to or more than 1.5 D in any axis improved in 26/54 of cases (48 %) by 2 lines or more. Refraction improves visual acuity of children with oculocutaneous albinism in a Sub-Saharan African population in Malawi. The mean improvement was 2 logMAR units.

The prevalence rates of refractive errors among children, adolescents, and adults in Germany.

PubMed

Jobke, Sandra; Kasten, Erich; Vorwerk, Christian

2008-09-01

The prevalence rates of myopia vary between 5% in Australian Aborigines to 84% in Hong Kong and Taiwan, 30% in Norwegian adults, and 49.5% in Swedish schoolchildren. The aim of this study was to determine the prevalence of refractive errors in German children, adolescents, and adults. The parents (aged 24-65 years) and their children (516 subjects aged 2-35 years) were asked to fill out a questionnaire about their refractive error and spectacle use. Emmetropia was defined as refractive status between +0.25D and -0.25D. Myopia was characterized as /=+0.5D. All information concerning refractive error were controlled by asking their opticians. The prevalence rates of myopia differed significantly between all investigated age groups: it was 0% in children aged 2-6 years, 5.5% in children aged 7-11 years, 21.0% in adolescents (aged 12-17 years) and 41.3% in adults aged 18-35 years (Pearson's Chi-square, p = 0.000). Furthermore, 9.8% of children aged 2-6 years were hyperopic, 6.4% of children aged 7-11 years, 3.7% of adolescents, and 2.9% of adults (p = 0.380). The prevalence of myopia in females (23.6%) was significantly higher than in males (14.6%, p = 0.018). The difference between the self-reported and the refractive error reported by their opticians was very small and was not significant (p = 0.850). In Germany, the prevalence of myopia seems to be somewhat lower than in Asia and Europe. There are few comparable studies concerning the prevalence rates of hyperopia.

Retinal dysfunction and refractive errors: an electrophysiological study of children

PubMed Central

Flitcroft, D I; Adams, G G W; Robson, A G; Holder, G E

2005-01-01

Aims: To evaluate the relation between refractive error and electrophysiological retinal abnormalities in children referred for investigation of reduced vision. Methods: The study group comprised 123 consecutive patients referred over a 14 month period from the paediatric service of Moorfields Eye Hospital for electrophysiological investigation of reduced vision. Subjects were divided into five refractive categories according to their spectacle correction: high myopia (⩽−6D), low myopia (>−6D and ⩽−0.75D), emmetropia (>−0.75 and <1.5D), low hyperopia (⩾1.5 and <6D), and high hyperopia (⩾6D). Patients with a specific diagnosis at the time of electrophysiological testing were excluded. Only the first member of any one family was included if more than one sibling had been tested. All tests were performed to incorporate ISCEV standards, using gold foil corneal electrodes where possible. In younger patients skin electrodes and an abbreviated protocol were employed. Results: The mean age of patients was 7.1 years with an overall incidence of abnormal electrophysiological findings of 29.3%. The incidence of abnormality was higher in high ametropes (13/25, 52%) compared to the other groups (23/98, 23.5%). This difference was statistically significant (χ2 test, p = 0.005). There was also a significant association between high astigmatism (>1.5D) and ERG abnormalities (18/35 with high astigmatism v 20/88 without, χ2 test, p = 0.002). There was no significant variation in frequency of abnormalities between low myopes, emmetropes, and low hyperopes. The rate of abnormalities was very similar in both high myopes (8/15) and high hyperopes (5/10). Conclusions: High ametropia and astigmatism in children being investigated for poor vision are associated with a higher rate of retinal electrophysiological abnormalities. An increased rate of refractive errors in the presence of retinal pathology is consistent with the hypothesis that the retina is involved in the process of emmetropisation. Electrophysiological testing should be considered in cases of high ametropia in childhood to rule out associated retinal pathology. PMID:15774929

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

Photorefractive keratectomy (PRK) versus laser assisted in situ keratomileusis (LASIK) for hyperopia correction.

PubMed

Settas, George; Settas, C; Minos, E; Yeung, Ian Y L

2009-04-15

Hyperopia, or hypermetropia (also known as long-sightedness or far-sightedness), is the condition where the unaccommodating eye brings parallel light to a focus behind the retina instead of on it. Hyperopia can be corrected with both non-surgical and surgical methods, among them photorefractive keratectomy (PRK) and laser assisted In situ keratomileusis (LASIK). There is uncertainty as to whether hyperopic-PRK or hyperopic-LASIK is the better method. The objectives of this review were to determine whether PRK or LASIK leads to more reliable, stable and safe results when correcting a hyperopic refractive error. We searched the Cochrane Central Register of Controlled Trials (The Cochrane Library Issue 4, 2008), MEDLINE (January 1950 to January 2009), EMBASE (January 1980 to January 2009) and LILACS (January 1982 to January 2009). There were no language or date restrictions in the search for trials. The electronic databases were last searched on 13 January 2009. We also searched the reference lists of the studies included in the review for information about further trials and used the Science Citation Index to search for papers that cite any studies included in this review. We did not handsearch journals or conference proceedings specifically for this review. We planned to include only randomised controlled trials (RCTs) comparing PRK against LASIK for correction of hyperopia and then perform a sensitivity analysis of pre- and post-millennial trials since this is the mid-point in the history of both PRK and LASIK. We did not identify any studies that met the inclusion criteria for this review. As no studies met the inclusion criteria for this review, we discussed the results of non-randomised trials comparing hyperopic-PRK with hyperopic-LASIK. No robust, reliable conclusions could be reached, but the non-randomised trials reviewed appear to be in agreement that hyperopic-PRK and hyperopic-LASIK are of comparable efficacy. High quality, well-planned open RCTs are needed in order to obtain a robust clinical evidence base.

Observations on the Relationship between Anisometropia, Amblyopia and Strabismus

PubMed Central

Smith, Earl L; Hung, Li-Fang; Arumugam, Baskar; Wensveen, Janice M.; Chino, Yuzo M.; Harwerth, Ronald S.

2017-01-01

We investigated the potential causal relationships between anisometropia, amblyopia and strabismus, specifically to determine whether either amblyopia or strabismus interfered with emmetropization. We analyzed data from non-human primates that were relevant to the co-existence of anisometropia, amblyopia and strabismus in children. We relied on interocular comparisons of spatial vision and refractive development in animals reared with 1) monocular form deprivation; 2) anisometropia optically imposed by either contact lenses or spectacle lenses; 3) organic amblyopia produced by laser ablation of the fovea; and 4) strabismus that was either optically imposed with prisms or produced by either surgical or pharmacological manipulation of the extraocular muscles. Hyperopic anisometropia imposed early in life produced amblyopia in a dose-dependent manner. However, when potential methodological confounds were taken into account, there was no support for the hypothesis that the presence of amblyopia interferes with emmetropization or promotes hyperopia or that the degree of image degradation determines the direction of eye growth. To the contrary, there was strong evidence that amblyopic eyes were able to detect the presence of a refractive error and alter ocular growth to eliminate the ametropia. On the other hand, early onset strabismus, both optically and surgically imposed, disrupted the emmetropization process producing anisometropia. In surgical strabismus, the deviating eyes were typically more hyperopic than their fellow fixating eyes. The results show that early hyperopic anisometropia is a significant risk factor for amblyopia. Early esotropia can trigger the onset of both anisometropia and amblyopia. However, amblyopia, in isolation, does not pose a significant risk for the development of hyperopia or anisometropia. PMID:28404522

Observations on the relationship between anisometropia, amblyopia and strabismus.

PubMed

Smith, Earl L; Hung, Li-Fang; Arumugam, Baskar; Wensveen, Janice M; Chino, Yuzo M; Harwerth, Ronald S

2017-05-01

We investigated the potential causal relationships between anisometropia, amblyopia and strabismus, specifically to determine whether either amblyopia or strabismus interfered with emmetropization. We analyzed data from non-human primates that were relevant to the co-existence of anisometropia, amblyopia and strabismus in children. We relied on interocular comparisons of spatial vision and refractive development in animals reared with 1) monocular form deprivation; 2) anisometropia optically imposed by either contact lenses or spectacle lenses; 3) organic amblyopia produced by laser ablation of the fovea; and 4) strabismus that was either optically imposed with prisms or produced by either surgical or pharmacological manipulation of the extraocular muscles. Hyperopic anisometropia imposed early in life produced amblyopia in a dose-dependent manner. However, when potential methodological confounds were taken into account, there was no support for the hypothesis that the presence of amblyopia interferes with emmetropization or promotes hyperopia or that the degree of image degradation determines the direction of eye growth. To the contrary, there was strong evidence that amblyopic eyes were able to detect the presence of a refractive error and alter ocular growth to eliminate the ametropia. On the other hand, early onset strabismus, both optically and surgically imposed, disrupted the emmetropization process producing anisometropia. In surgical strabismus, the deviating eyes were typically more hyperopic than their fellow fixating eyes. The results show that early hyperopic anisometropia is a significant risk factor for amblyopia. Early esotropia can trigger the onset of both anisometropia and amblyopia. However, amblyopia, in isolation, does not pose a significant risk for the development of hyperopia or anisometropia. Copyright © 2017 Elsevier Ltd. All rights reserved.

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.

Axial Length/Corneal Radius of Curvature Ratio and Myopia in 3-Year-Old Children

PubMed Central

Foo, Valencia Hui Xian; Verkicharla, Pavan Kumar; Ikram, Mohammad Kamran; Chua, Sharon Yu Lin; Cai, Shirong; Tan, Chuen Seng; Chong, Yap-Seng; Kwek, Kenneth; Gluckman, Peter; Wong, Tien-Yin; Ngo, Cheryl; Saw, Seang-Mei; on behalf of the GUSTO study group

2016-01-01

Purpose This study investigated the association of axial length (AL) to corneal radius of curvature (CRC) ratio with spherical equivalent (SE) in a 3-year old Asian cohort. Methods Three-hundred forty-nine 3-year old Asian children from The Growing Up in Singapore towards Healthy Outcomes (GUSTO) birth cohort study underwent AL and CRC measurements with a noncontact ocular biometer and cycloplegic refraction using an autorefractor. The ratio of AL to CRC (AL/CRC) was calculated for all the participants, and subsequently AL, CRC, and AL/CRC were analyzed in relationship to SE. Results The SE showed better correlation with AL/CRC (Spearman's correlation coefficient, ρ = −0.53; 95% confidence interval [CI]: −0.66; −0.49; P < 0.001) compared to either AL or CRC alone ([ρ = −0.36; 95% CI: −0.51 to 0.51; P = 0.01] and [ρ = 0.05; 95% CI: −0.04 to 0.17; P = 0.34], respectively). Mean AL/CRC was 2.91 ± 0.06 among myopes and decreased to 2.79 ± 0.06 among hyperopes. Axial length to corneal radius of curvature was strongly correlated with SE in myopes (ρ = −0.78; 95% CI: −3.76; −0.79; P = < 0.001), but not in emmetropes and hyperopes ([ρ = −0.39; 95% CI: −10.73; −0.57; P = 0.01] and [ρ = −0.18; 95% CI: −17.28; 12.42; P = 0.38], respectively). Linear regression adjusted for gender and ethnicity showed a 0.74-diopter shift in SE towards myopia with every 0.1 increase in AL/CRC ratio (P < 0.001, r2 = 0.33). Conclusion The correlation between SE and AL/CRC is stronger than that between AL or CRC alone. This suggests that in a research setting, when cycloplegic refraction is difficult to perform on 3-year-old children, AL/CRC may be the next best reference for refractive error. Translational Relevance In the research setting, AL/CRC may be the next best reference for refractive error over AL alone when cycloplegic refraction is unavailable in 3-year old children. PMID:26929885

Refraction and Ocular Biometry of Preschool Children in Shanghai, China

PubMed Central

He, Xiangui; You, Xiaofang; Wang, Bingjie; Tan, Hui; Zhu, Jianfeng

2018-01-01

Purpose To investigate the refraction and ocular biometry characteristics and to examine the prevalence of refractive errors in preschool children aged 3 to 6 years in Shanghai, China. Methods A school-based cross-sectional study was conducted in Jiading and Xuhui District, Shanghai, in 2013. We randomly selected 7 kindergartens in Jiading District and 10 kindergartens in Xuhui District, with a probability proportionate to size. The children underwent comprehensive eye examinations, including cycloplegic refraction and biometric measurements. Myopia, hyperopia, astigmatism were defined as spherical equivalent (SE) ≤ −0.50 D, SE ≥ +2.00 D, and cylindrical diopters ≤ −1.00 D. Results The mean SE for 3- to 6-year-old children was +1.20 D (standard deviation [SD] 1.05), and the mean axial length (AL) was 22.29 mm (SD 0.73). The overall prevalence of myopia and astigmatism was 3.7% and 18.3%, respectively. No difference in prevalence of astigmatism was found across age groups. There was a statistically significant association between lower cylindrical diopters and higher spherical diopters (Spearman's correlation: −0.21, P < 0.001). Conclusion Chinese children aged 3 to 6 years in the Shanghai area were mostly mildly hyperopic, with a low prevalence of myopia. Refractive astigmatism for children may be relatively stable throughout the preschool stage. Astigmatism was significantly associated with refractive error. PMID:29692930

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

Role of percent peripheral tissue ablated on refractive outcomes following hyperopic LASIK

PubMed Central

Stapleton, Fiona; Versace, Patrick

2017-01-01

Objectives To determine the effect of hyperopic laser in situ keratomileusis (H-LASIK) on corneal integrity, by investigating relationships between proportionate corneal tissue ablated and refractive outcomes at 3 months. Methods 18 eyes of 18 subjects treated with H-LASIK by Technolas 217c Excimer Laser were included in the study. Orbscan II Topography System was used to determine corneal volume and pachymetry 3mm temporally (3T). The volume of corneal tissue ablated was determined from the laser nomogram. Univariate associations between age, treatment, corneal volume, overall proportion of tissue removed, proportion of tissue removed at 3T, residual bed thickness at 3T and refractive outcomes 3 months post-LASIK were examined and independent factors associated with refractive outcomes determined using linear regression models. Results At 3 months post-LASIK, the mean difference to expected refractive outcome was -0.20 ± 0.64 (Range -2.00 to +1.00). In univariate analysis, difference to expected refractive outcome was associated with proportion of tissue removed at 3T (P<0.01, r = -0.605) and total number of pulses (P< 0.05, r = -0.574). In multivariable analysis, difference to expected refractive outcome was associated with the proportion of tissue removed at 3T only. Conclusion Subjects undergoing H-LASIK, may present as either over or under-corrected at 3 months. The proportion of tissue removed at 3T was the single significant determinant of this outcome, suggesting unexpected biomechanical alterations resulting in corneal steepening. Future hyperopic LASIK procedures could consider proportionate volume of corneal tissue removed at 3T in addition to laser nomograms to achieve improved refractive outcomes. PMID:28151939

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

Corneal refractive surgery: Is intracorneal the way to go and what are the needs for technology?

NASA Astrophysics Data System (ADS)

Hjortdal, Jesper; Ivarsen, Anders

2014-02-01

Corneal refractive surgery aims to reduce or eliminate refractive errors of the eye by changing the refractive power of the cornea. For the last 20 years controlled excimer laser ablation of corneal tissue, either directly from the corneal stromal surface or from the corneal interior after creation of a superficial corneal flap has become widely used to correct myopia, hyperopia, and astigmatism. Recently, an intrastromal refractive procedure whereby a tissue lenticule is cut free in the corneal stroma by a femtosecond laser and removed through a small peripheral incision has been introduced. This procedure avoids creation of a corneal flap and the potential associated risks while avoiding the slow visual recovery of surface ablation procedures. Precise intrastromal femtosecond laser cutting of the fine lenticule requires very controlled laser energy delivery in order to avoid lenticule irregularities, which would compromise the refractive result and visual acuity. This newly introduced all-femtosecond based flap-free intracorneal refractive procedure has been documented to be a predictable, efficient, and safe procedure for correction of myopia and astigmatism. Technological developments related to further improved cutting quality, hyperopic and individualized treatments are desirable.

Comparison of keratometric values and corneal eccentricity.

PubMed

Benes, Pavel; Synek, Svatopluk; Petrová, Sylvie

2013-04-01

The aim of this work is to compare the findings of keratometric values and their differences at various refractive errors. The eccentricity of the cornea in the sense compared to the possible influence of refraction of the eye is topographically observed. Groups of myopia, hyperopia and emmetropia (as a control group) are always represented in total 600 eyes. The studied cohort in total of 300 clients enrolled. Autorefraktokeratometer with Placido disc was used to measure the steepest and the flattest meridian to determine the corneal eccentricity. Group I consisted of 100 myopes, 35 men and 65 women, average age 37.3 years. Objective refraction--sphere: -2.9 D, cylinder: -0.88 D. Keratometry in this group is in the steepest meridian 7.62 mm and the flattest meridian is 7.76 mm. The eccentricity was 0.37. Group II consisting of 100 hyperopic subjects, 40 men and 60 women, average age 61.6 years. Objective refraction--sphere: +2.71 D, cylinder: -1.0 D. Keratometric measurement looks as follows: the steepest meridian is 7.67 mm, the flattest meridian then is 7.81 mm. The value of the eccentricity is 0.37. The third group III consists of 100 emetropic subjects, then clients without refractive errors who achieve without corrective aids Vmin = 1.0. This group is composed of 42 men and 58 women, mean age 41.4 years. Objective refraction--sphere: +0.32 D, cylinder: -0.28 D. The steepest meridian is 7.72 mm the flattest meridian then 7.83 mm. The eccentricity is represented by the observed values of 0.36. Keratometry as well as topography are fundamental methods of corneal anterior surface measurement. Their proportions are essential for the proper parameters selection especially in case of contact lenses as one of the possible means intended to correct refractive errors.

The prevalence of refractive conditions in Puerto Rican adults attending an eye clinic system

PubMed Central

Rodriguez, Neisha M.; Romero, Angel. F.

2014-01-01

Purpose To determine the prevalence of refractive conditions in the adult population that visited primary care optometry clinics in Puerto Rico. Methods A retrospective cross-sectional study of patients examined at the Inter American University of Puerto Rico School of Optometry Eye Institute Clinics between 2004 and 2010. Subjects considered had best corrected visual acuity by standardized subjective refraction of 20/40 or better. The refractive errors were classified by the spherical equivalent (SE): sphere+½ cylinder. Myopia was classified as a SE>−0.50 D, hyperopia as a SE>+0.50  D, and emmetropia as a SE between −0.50 and +0.50, both included. Astigmatism equal or higher than 0.25 D in minus cylinder form was used. Patients with documented history of cataract extraction (pseudophakia or aphakia), amblyopia, refractive surgery or other corneal/ocular surgery were excluded from the study. Results A total of 784 randomly selected subjects older than 40 years of age were selected. The estimated prevalence (95%, confidence interval) among all subjects was hyperopia 51.5% (48.0–55.0), emmetropia 33.8% (30.5–37.2), myopia 14.7% (12.1–17.2) and astigmatism 69.6% (68.8–73.3). Hyperopia was more common in females than males although the difference was not statistically significant. The mean spherical equivalent values was hyperopic until 70 y/o and decreased slightly as the population ages. Conclusion Hyperopia is the most common refractive error and its prevalence and seems to increase among the aging population who visited the clinics. Further programs and studies must be developed to address the refractive errors needs of the adult Puerto Rican population. PMID:25000872

Effect of Amblyopia Treatment on Choroidal Thickness in Children with Hyperopic Anisometropic Amblyopia.

PubMed

Aslan Bayhan, Seray; Bayhan, Hasan Ali

2017-09-01

To evaluate choroidal thickness (CT) in the eyes of children with hyperopic anisometropic amblyopia and to assess changes in CT during amblyopia treatment using spectral-domain optical coherence tomography (SD-OCT). This longitudinal study, initially enrolled 40 patients, aged 3-9 years with hyperopic anisometropic amblyopia. Patients underwent treatment with refractive correction alone for 16 weeks and if needed, with refractive correction and patching treatment thereafter (6 months). CT was measured perpendicularly (from the outer edge of the hyper-reflective retinal pigment epithelium to the inner sclera) at the fovea, and 1.5-mm temporal, 3.0-mm temporal, 1.5-mm nasal, and 3.0-mm nasal to the fovea using SD-OCT in amblyopic eyes and fellow eyes during treatment and in the control subjects (n = 22). The baseline subfoveal CT measurement was mean 367.9 ± 54 in the amblyopic eyes, 283.9 ± 39.6 in the fellow eyes, and 267.3 ± 41.3 µm in the control eyes. Before amblyopia treatment, the subfoveal CT and CT at 1.5-mm nasal and temporal to the fovea and 3.0-mm nasal to fovea in the amblyopic eyes were significantly thicker than those of the control subjects after adjustment for refraction and axial length by multivariate ANCOVA. CT at all locations decreased significantly after treatment in the amblyopic eyes. The final measurement of subfoveal choroid and CT at 1.5-mm nasal to the fovea of the amblyopic eyes was significantly thicker than those of the control subjects after adjusting for axial length and refraction. The findings of this study indicate that children with hyperopic anisometropic amblyopia have significant CT alterations, and these changes partially regress after amblyopia treatment.

Does the treatment of amblyopia normalise subfoveal choroidal thickness in amblyopic children?

PubMed

Öner, Veysi; Bulut, Asker

2017-03-01

Recent studies have found a choroidal thickening in amblyopic eyes and suggested that there might be a relationship between the choroid and amblyopia. The present study aimed to evaluate the effect of a six-month treatment of amblyopia on choroidal thickness in anisometropic hyperopic amblyopic children. Thirty-two anisometropic hyperopic children with unilateral amblyopia were included in this prospective study. Subfoveal choroidal thickness was measured as the distance between the retinal pigment epithelium and the chorioscleral edge, by using spectral domain enhanced depth imaging optical coherence tomography. The treatment of amblyopia was performed based on the full correction of the refractive error with eyeglasses, a refractive adaptation phase and occlusion by patching the fellow eye. The mean visual acuity of the amblyopic eyes significantly increased from 0.35 ± 0.3 to 0.16 ± 0.2 logMAR after the treatment (p < 0.001). The mean initial choroidal thickness was significantly higher in the amblyopic eyes than in the fellow eyes (p = 0.019). There were no significant differences between the pre- and post-treatment mean choroidal thickness in the amblyopic eyes (p = 0.428) and in the fellow eyes (p = 0.343). The mean choroidal thickness was still higher in the amblyopic eyes than in the fellow eyes after the treatment (p = 0.006). Although a six-month treatment of amblyopia increased the visual acuity of the anisometropic hyperopic amblyopic eyes, it could not significantly change choroidal thickness. Our results were in accordance with the conventional explanation, which suggests visual cortex and lateral geniculate nucleus abnormalities in the pathophysiology of amblyopia. © 2016 Optometry Australia.

Laser in situ keratomileusis for residual hyperopic astigmatism after conductive keratoplasty.

PubMed

Kymionis, George D; Aslanides, Ioannis M; Khoury, Aghlab N; Markomanolakis, Marinos M; Naoumidi, Tatiana; Pallikaris, loannis G

2004-01-01

To report a case of laser in situ keratomileusis (LASIK) in a patient with previous conductive keratoplasty. A 48-year-old man underwent conductive keratoplasty for low hyperopic astigmatism (manifest refraction OD: +2.25 -0.50 x 77 degrees; OS: +2.50 -0.50 x 105 degrees). Three months postoperatively, UCVA was 20/25 and BSCVA was 20/20 in both eyes; manifest refraction OD: -0.25 -0.75 x 110 degrees; OS: +0.75 -0.75 x 50 degrees. Sixteen months after the operation, regression of refractive outcome was (manifest) OD: +1.75 -1.25 x 90 degrees; OS: +2.50 -0.50 x 85 degrees; UCVA was 20/40 in the right eye and 20/63 in the left eye and BSCVA was 20/20 in both eyes. LASIK was performed for hyperopic regression in the left eye using an automated microkeratome (Alcon SKBM, 130-microm plate; Aesculap-Meditec MEL 70 excimer laser). LASIK was uneventful and no intraoperative or postoperative complications related to the previous conductive keratoplasty procedure or LASIK were observed. Three months after LASIK and 19 months after the initial conductive keratoplasty, the patient's left eye was emmetropic; UCVA was 20/20(-2), BSCVA was 20/20 and manifest refraction was +0.25 -0.25 x 35 degrees. There was a uniform increase in topographical steepening. Visual acuity, refraction and topographic findings remained unchanged at 6 months. Even though our experience is limited, treatment of hyperopia with LASIK in an eye with refractive regression following previous conductive keratoplasty resulted in a predicted refractive outcome, with no complications, and improvement in visual acuity at 6 months follow-up.

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

Two-dimensional simulation of eccentric photorefraction images for ametropes: factors influencing the measurement.

PubMed

Wu, Yifei; Thibos, Larry N; Candy, T Rowan

2018-05-07

Eccentric photorefraction and Purkinje image tracking are used to estimate refractive state and eye position simultaneously. Beyond vision screening, they provide insight into typical and atypical visual development. Systematic analysis of the effect of refractive error and spectacles on photorefraction data is needed to gauge the accuracy and precision of the technique. Simulation of two-dimensional, double-pass eccentric photorefraction was performed (Zemax). The inward pass included appropriate light sources, lenses and a single surface pupil plane eye model to create an extended retinal image that served as the source for the outward pass. Refractive state, as computed from the luminance gradient in the image of the pupil captured by the model's camera, was evaluated for a range of refractive errors (-15D to +15D), pupil sizes (3 mm to 7 mm) and two sets of higher-order monochromatic aberrations. Instrument calibration was simulated using -8D to +8D trial lenses at the spectacle plane for: (1) vertex distances from 3 mm to 23 mm, (2) uncorrected and corrected hyperopic refractive errors of +4D and +7D, and (3) uncorrected and corrected astigmatism of 4D at four different axes. Empirical calibration of a commercial photorefractor was also compared with a wavefront aberrometer for human eyes. The pupil luminance gradient varied linearly with refractive state for defocus less than approximately 4D (5 mm pupil). For larger errors, the gradient magnitude saturated and then reduced, leading to under-estimation of refractive state. Additional inaccuracy (up to 1D for 8D of defocus) resulted from spectacle magnification in the pupil image, which would reduce precision in situations where vertex distance is variable. The empirical calibration revealed a constant offset between the two clinical instruments. Computational modelling demonstrates the principles and limitations of photorefraction to help users avoid potential measurement errors. Factors that could cause clinically significant errors in photorefraction estimates include high refractive error, vertex distance and magnification effects of a spectacle lens, increased higher-order monochromatic aberrations, and changes in primary spherical aberration with accommodation. The impact of these errors increases with increasing defocus. © 2018 The Authors Ophthalmic & Physiological Optics © 2018 The College of Optometrists.

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.

Proportion of refractive errors in a Polish immigrant population in Chicago.

PubMed

Allison, Christine L

2010-08-01

This retrospective record review was conducted to investigate the proportion of patients with refractive error in a Polish immigrant population residing in an urban environment. Illinois has more than 1 million people of Polish descent as citizens, and Chicago is considered to have the second largest population of Polish descent in the world, outside of Warsaw, Poland. Six hundred seventy-five records (271 men/404 women) of Polish immigrants were reviewed from a practice with >92% Polish immigrants in the patient base. The patients ranged in age from 3 to 94 years. Refractive status for each eye, and the existence of any strabismus or amblyopia, was recorded. The proportion of myopia [spherical equivalent at least -0.75 diopter (D)] was found to be 35.1%, whereas the proportion of hyperopia (spherical equivalent > or =+0.75 D) was found to be 38.4%. Fifteen percent of the patients exhibited astigmatism > or =1.00 D. Amblyopia was present in 9% of the patients, whereas the prevalence of strabismus was found to be 3%, with 76% of the strabismics exhibiting esotropia. In the 0- to 18-year age range and the 19- to 45-year age range, the most common refractive error was low myopia (43.9 and 36.9%), whereas in the patients >45 years of age, it was low hyperopia (31.2%). Refractive error data are presented for a population base that has not been previously reported, although Polish Americans comprise 3% of the US population. Myopia is more common in young Polish patients than in the general US population. The strong hyperopic shift in older patients may either be normal aging or the product of increased near work in the young. The high rates of amblyopia call for more aggressive education and treatment.

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.

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.

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.

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.

Two-year changes in refractive error and related biometric factors in an adult Chinese population.

PubMed

He, Mingguang; Kong, Xiangbin; Chen, Qianyun; Zeng, Yangfa; Huang, Yuanzhou; Zhang, Jian; Morgan, Ian G; Meltzer, Mirjam E; Jin, Ling; Congdon, Nathan

2014-08-01

This article provides, to our knowledge, the first longitudinal population-based data on refractive error (RE) in Chinese persons. To study cohort effects and changes associated with aging in REs among Chinese adults. A 2-year, longitudinal population-based cohort study was conducted in southern China. Participants, identified using cluster random sampling, included residents of Yuexiu District, Guangzhou, China, aged 35 years or older who had undergone no previous eye surgery. Participants underwent noncycloplegic automated refraction and keratometry in December 2008 and December 2010; in a random 50% sample of the participants, anterior segment ocular coherence tomography measurement of lens thickness, as well as measurement of axial length and anterior chamber depth by partial coherence laser interferometry, were performed. Two-year change in spherical equivalent refraction (RE), lens thickness, axial length, and anterior chamber depth in the right eye. A total of 745 individuals underwent biometric testing in both 2008 and 2010 (2008 mean [SD] age, 52.2 [11.5] years; 53.7% women). Mean RE showed a 2-year hyperopic shift from -0.44 (2.21) to -0.31 (2.26) diopters (D) (difference, +0.13; 95% CI, 0.11 to 0.16). A consistent 2-year hyperopic shift of 0.09 to 0.22 D was observed among participants aged 35 to 64 years when stratifying by decade, suggesting that a substantial change in RE with aging may occur during this 30-year period. Cross-sectionally, RE increased only in the cohort younger than 50 years (0.11 D/y; 95% CI, 0.06 to 0.16). In the cross-sectional data, axial length decreased at -0.06 mm/y (95% CI, -0.09 to -0.04), although the 2-year change in axial length was positive and thus could not explain the cross-sectional difference. These latter results suggest a cohort effect, with greater myopia developing among younger persons. This first Chinese population-based longitudinal study of RE provides evidence for both important longitudinal aging changes and cohort effects, most notably greater myopia prevalence among younger persons.

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.

Pigmented striae of the anterior lens capsule and age-associated pigment dispersion of variable degree in a group of older African-Americans: an age, race, and gender matched study.

PubMed

Roberts, D K; Winters, J E; Castells, D D; Clark, C A; Teitelbaum, B A

2001-01-01

To investigate pigmented striae of the anterior lens capsule in African-Americans, a potential indicator of significant anterior segment pigment dispersion. A group of 40 African-American subjects who exhibited pigmented lens striae (PLS) were identified from a non-referred, primary eye care population in Chicago, IL, USA. These subjects were then compared to an age, race, and gender matched control group relative to refractive error and the presence or absence of diabetes and hypertension. The PLS subjects (mean age = 65.4 +/- 8.8 years, range = 50-87 years) consisted of 36 females and 4 males. PLS were bilateral in 36 (85%) of the 40 subjects. Among the eyes with PLS, 21 (55%) of 38 right eyes and 22 (61%) of 36 left eyes also had significant corneal endothelial pigment dusting, commonly in the shape of a Krukenberg's spindle. Ten (25%) of the PLS subjects had either glaucoma or ocular hypertension (7 bilateral, 3 unilateral). The presence of trabecular meshwork pigment varied from minimal to heavy. The mean +/- SD (range) refractive error of the PLS right eyes was +1.61 +/- 1.43D (-1.50 to +5.00D) and +1.77 +/- 1.37D (-1.00 to +5.00D) for the left eyes. Based on these data, the PLS right eyes were +1.63D (Student's t, p = 0.0001; 95% CI = +0.82 to +2.44D) more hyperopic on average than the control right eyes, and the PLS left eyes were +1.77D (p = 0.0001; 95% CI = +0.92 to +2.63D) more hyperopic on average than the control left eyes. Trend analysis showed a gradually increasing likelihood of PLS with increasing magnitude of hyperopia in both eyes (Mantel-Haenszel chi-square, p = 0.001). Among PLS subjects, 24 (60%) of 40 were hypertensive and 9 (23%) of 40 were diabetic. However, these proportions were not significantly different (two-tailed Fisher's exact test; hypertension: p = 0.30; diabetes: p = 0.70) from the randomly selected controls. Among our African-American group, which consisted predominately of females >50 years of age, the likelihood of PLS increased with increasing hyperopic refractive error. This finding is consistent with the possibility that PLS may, in some circumstances, indicate a significant pigment dispersal process due to iris-lens rubbing that may be associated with crowding of anterior segment structures. Additional study is warranted to further assess the nature of PLS, their precise relationship with an age-related pigment dispersal process, and their true significance as a risk factor for development of glaucoma.

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.

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.

Excimer laser delivery system for astigmatic and hyperopic photorefractive surgery

NASA Astrophysics Data System (ADS)

Beck, Rasmus; Foerster, Werner

1994-06-01

Ablation of corneal tissue with excimer laser light is an effective way to correct refractive errors of the eye. For this purpose a beam-stop (iris diaphragm or interchangeable masks) is illuminated by the laser radiation. The beam-stop is imaged onto the cornea, and circular or elliptic ablations are produced. The computer-controlled process varies the diameter of the ablation area in a way that the inner portions of the treatment zone receive more laser energy than the outer portions, thus flattening the curvature of the refractive surface. For the treatment of hyperopia, the outer portions of the ablation area receive more laser energy to steepen the surface profile of the cornea. The beam delivery system employs several sets of circular, elliptic and ring shaped masks which are etched into a stainless-steel tape.

Longitudinal Increase in Anisometropia in Older Adults

PubMed Central

Haegerstrom-Portnoy, Gunilla; Schneck, Marilyn E.; Lott, Lori A.; Hewlett, Susan E.; Brabyn, John A.

2014-01-01

Purpose Anisometropia shows an exponential increase in prevalence with increasing age based on cross-sectional studies. The purpose of this study was to evaluate longitudinal changes in anisometropia in all refractive components in older observers and to assess the influence of early cataract development. Methods Refractive error was assessed at two time points separated by ~12 years in 118 older observers (ages 67.1 and 79.3 years at the two test times). Anisometropia defined as ≥1.00 D was calculated for all refractive components. The subjects had intact ocular lenses in both eyes throughout the study. Lens evaluations were performed at the second test using LOCS III. Results All refractive components approximately doubled in prevalence of anisometropia. Spherical equivalent anisometropia changed from 16.1% to 32.2%. Similar changes were found for spherical error (17% to 38.1%), primary astigmatism (7.6% to 17.8%) and oblique astigmatism (14.4% to 29.7%). Many who did not have anisometropia at the first visit subsequently developed anisometropia (for ex. 26.3% for spherical error and 22.9% for oblique cylinder). The onset of anisometropia occurred at all ages within the studied age range with no particular preference for any one age. A small number lost anisometropia over time. Individual comparisons of refractive error changes in the two eyes in combination with nuclear lens changes showed that early changes in nuclear sclerosis in the two eyes could account for a large proportion of anisometropia (~40%) but unequal hyperopic shift in the spherical component in the two eyes was the primary cause of the anisometropia. Conclusions Anisometropia is at least 10 times more common in the elderly than in children and anisometropia develops in all refractive components in the oldest observers. Clinicians need to be aware of this common condition that could lead to binocular vision problems and potentially cause falls in the elderly. PMID:24276578

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

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.

Retinal profile and structural differences between myopes and emmetropes

NASA Astrophysics Data System (ADS)

Clark, Christopher Anderson

Refractive development has been shown to be influenced by optical defocus in the eye and the interpretation of this signal appears to be localized in the retina. Optical defocus is not uniform across the retina and has been suggested as a potential cause of myopia development. Specifically hyperopic focus, i.e. focusing light behind the retina, may signal the eye to elongate, causing myopia. This non-uniform hyperopic signal appears to be due to the retinal shape. Ultimately, these signals are detected by the retina in an as yet undetermined manner. The purpose of this thesis is to examine the retinal profile using a novel method developed at Indiana University and then to examine retinal structural changes across the retina associated with myopia. Myopes exhibited more prolate retinas than hyperopes/emmetropes using the SD OCT. Using the SD OCT, this profile difference was detectable starting at 5 degrees from the fovea, which was closer than previously reported in the literature. These results agreed significantly with results found from peripheral refraction and peripheral axial length at 10 degrees. Overall, the total retina was thinner for myopes than hyperopes/emmetropes. It was also statistically significantly thinner for the Outer Nuclear Layer (ONL), Inner Nuclear Layer (INL) and Outer Plexiform Layer (OPL) but not for other retinal layers such as the Ganglion Layer. Thinning generally occurred outside of 5 degrees. The SD OCT method provided a nearly 10 fold increase in sensitivity which allowed for detection of profile changes closer to the fovea. The location of the retinal changes may be interesting as the layers that showed significant differences in thickness are also layers that contain cells believed to be associated with refractive development (amacrine, bipolar, and photoreceptor cells.) The reason for the retinal changes cannot be determined with this study, but possible theories include stretch due to axial elongation, neural remodeling due to blur, and/or direct influence on refractive development due to neural cell densities.

Childhood myopia and parental smoking.

PubMed

Saw, S-M; Chia, K-S; Lindstrom, J M; Tan, D T H; Stone, R A

2004-07-01

To examine the relation between exposure to passive parental smoke and myopia in Chinese children in Singapore. 1334 Chinese children from three schools in Singapore were recruited, all of whom were participants in the Singapore Cohort study Of the Risk factors for Myopia (SCORM). Information on whether the father or mother smoked, number of years smoked, and the number of cigarettes smoked per day during the child's lifetime were derived. These data were correlated with contemporaneously obtained data available in SCORM. The children's cycloplegic autorefraction, corneal curvature radius, and biometry measures were compared with reported parental smoking history. There were 434 fathers (33.3%) and 23 mothers (1.7%) who smoked during their child's lifetime. There were no significant trends observed between paternal smoking and refractive error or axial length. After controlling for age, sex, school, mother's education, and mother's myopia, children with mothers who had ever smoked during their lifetime had more "positive" refractions (adjusted mean -0.28 D v -1.38 D) compared with children whose mother did not smoke (p = 0.012). The study found no consistent evidence of association between parental smoking and refractive error. There was a suggestion that children whose mothers smoked cigarettes had more hyperopic refractions, but the absence of a relation with paternal smoking and the small number of mothers who smoked in this sample preclude definite conclusions about a link between passive smoking exposure and myopia.

Visual acuity, refractive error, and endothelial cell density six months after Descemet stripping and automated endothelial keratoplasty (DSAEK).

PubMed

Koenig, Steven B; Covert, Douglas J; Dupps, William J; Meisler, David M

2007-07-01

To evaluate visual acuity, refractive outcomes, and endothelial cell density 6 months after Descemet stripping and automated endothelial keratoplasty (DSAEK). We performed an institutional review board-approved prospective study of a surgical case series of 34 patients at 2 institutions undergoing DSAEK for Fuchs endothelial dystrophy, pseudophakic bullous keratopathy, or aphakic bullous keratopathy with or without simultaneous phacoemulsification and intraocular lens implantation. Clinical outcomes, including best spectacle-corrected visual acuity (BSCVA), spherical equivalent refraction, and refractive astigmatism and topographic or keratometric astigmatism, were assessed at the 6-month postoperative examination and compared with preoperative values with paired Student t tests. The change in endothelial cell density from the eye bank examination to 6 months after transplantation was similarly evaluated. BSCVA averaged 20/99 preoperatively and 20/42 postoperatively (P < 0.0001). After DSAEK, 30 (88.2%) of 34 patients showed improved BSCVA, and 21 (61.8%) of the 34 patients achieved a BSCVA of 20/40 or better. For patients not undergoing simultaneous phacoemulsification and intraocular lens implantation, a hyperopic shift in refraction of 1.19 +/- 1.32 D was noted. Refractive astigmatism, topographic astigmatism, and keratometry showed no statistically significant change. Endothelial cell density of donor corneas averaged 2826 +/- 370 cells/mm, whereas the mean postoperative density was 1396 +/- 440 cells/mm. This finding corresponded to an average loss of 1426 cells/mm (50% loss; P = 0.0001). The first half of cases experienced an average cell loss of 1674 cells/mm (59% loss) compared with 1181 (41% loss) in the second half of cases (P = 0.005). Three (9%) of 34 grafts experienced iatrogenic graft failure and required reoperation with new donor tissue. Also, 9 (27%) of 34 grafts experienced dislocation in the early postoperative period and required repositioning. In this prospective study of DSAEK for bullous keratopathy and Fuchs endothelial corneal dystrophy, improvement of visual acuity was achieved with only a mild tendency toward hyperopic shift and without significant induced astigmatism. Endothelial cell loss was significant, however, and may be related to surgical experience.

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.

Central serous choroidopathy in the Hallermann-Streiff Syndrome.

PubMed

Blair, N P; Brockhurst, R J; Lee, W

1981-08-01

Central serous choroidopathy was observed in a young patient with the Hallermann-Streiff syndrome. Typical features of this syndrome include microphthalmos, proportionate dwarfism, dyscephaly with birdlike facies, dental abnormalities, and hypotrichosis. Exceptional aspects of this case include age of onset (11 years), high hyperopic refractive error (+ 13.00 sphere), and multiple recurrences caused by six separate documented leaks from the choroid. Fundus changes previously reported in the Hallermann-Streiff syndrome, interpreted as chorioretinal pigmentary changes, may have been secondary to previous undiagnosed central serous choroidopathy. Periodic ophthalmoscopy should be performed and may detect unrecognized episodes of central serous choroidopathy for which photocoagulation would be beneficial.

Laser-assisted in situ keratomileusis with optimized, fast-repetition, and cyclotorsion control excimer laser to treat hyperopic astigmatism with high cylinder.

PubMed

Alió Del Barrio, Jorge L; Tiveron, Mauro; Plaza-Puche, Ana B; Amesty, María A; Casanova, Laura; García, María J; Alió, Jorge L

2017-10-18

To evaluate the visual outcomes after femtosecond laser-assisted laser in situ keratomileusis (LASIK) surgery to correct primary compound hyperopic astigmatism with high cylinder using a fast repetition rate excimer laser platform with optimized aspheric profiles and cyclotorsion control. Eyes with primary simple or compound hyperopic astigmatism and a cylinder power ≥3.00 D had uneventful femtosecond laser-assisted LASIK with a fast repetition rate excimer laser ablation, aspheric profiles, and cyclotorsion control. Visual, refractive, and aberrometric results were evaluated at the 3- and 6-month follow-up. The astigmatic outcome was evaluated using the Alpins method and ASSORT software. This study enrolled 80 eyes at 3 months and 50 eyes at 6 months. The significant reduction in refractive sphere and cylinder 3 and 6 months postoperatively (p<0.01) was associated with an improved uncorrected distance visual acuity (p<0.01). A total of 23.75% required retreatment 3 months after surgery. Efficacy and safety indices at 6 months were 0.90 and 1.00, respectively. At 6 months, 80% of eyes had an SE within ±0.50 D and 96% within ±1.00 D. No significant differences were detected between the third and the sixth postoperative months in refractive parameters. A significant increase in the spherical aberration was detected, but not in coma. The correction index was 0.94 at 3 months. Laser in situ keratomileusis for primary compound hyperopic astigmatism with high cylinder (>3.00 D) using the latest excimer platforms with cyclotorsion control, fast repetition rate, and optimized aspheric profiles is safe, moderately effective, and predictable.

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.

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.

Photorefractive keratectomy (PRK) versus laser assisted in situ keratomileusis (LASIK) for hyperopia correction.

PubMed

Settas, George; Settas, Clare; Minos, Evangelos; Yeung, Ian Yl

2012-06-13

Hyperopia, or hypermetropia (also known as long-sightedness or far-sightedness), is the condition where the unaccommodating eye brings parallel light to a focus behind the retina instead of on it. Hyperopia can be corrected with both non-surgical and surgical methods, among them photorefractive keratectomy (PRK) and laser assisted In situ keratomileusis (LASIK). There is uncertainty as to whether hyperopic-PRK or hyperopic-LASIK is the better method. The objectives of this review were to determine whether PRK or LASIK leads to more reliable, stable and safe results when correcting a hyperopic refractive error. We searched CENTRAL (which contains the Cochrane Eyes and Vision Group Trials Register) (The Cochrane Library 2012, Issue 2), MEDLINE (January 1950 to February 2012), EMBASE (January 1980 to February 2012), Latin American and Caribbean Literature on Health Sciences (LILACS) (January 1982 to February 2012), the metaRegister of Controlled Trials (mRCT) (www.controlled-trials.com), ClinicalTrials.gov (www.clinicaltrials.gov) and the WHO International Clinical Trials Registry Platform (ICTRP) (www.who.int/ictrp/search/en). There were no date or language restrictions in the electronic searches for trials. The electronic databases were last searched on 17 February 2012. When trials are included in the review we will search the reference lists of the studies included in the review for information about further trials. We will use the Science Citation Index to search for papers that cite any studies included in this review. We did not handsearch journals or conference proceedings specifically for this review. We planned to include only randomised controlled trials (RCTs) comparing PRK against LASIK for correction of hyperopia and then perform a sensitivity analysis of pre- and post-millennial trials since this is the mid-point in the history of both PRK and LASIK. We did not identify any studies that met the inclusion criteria for this review. As no studies met the inclusion criteria for this review, we discussed the results of non-randomised trials comparing hyperopic-PRK with hyperopic-LASIK. No robust, reliable conclusions could be reached, but the non-randomised trials reviewed appear to be in agreement that hyperopic-PRK and hyperopic-LASIK are of comparable efficacy. High quality, well-planned open RCTs are needed in order to obtain a robust clinical evidence base.

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.

One-year eye-to-eye comparison of wavefront-guided versus wavefront-optimized laser in situ keratomileusis in hyperopes

PubMed Central

Sáles, Christopher S; Manche, Edward E

2014-01-01

Background To compare wavefront (WF)-guided and WF-optimized laser in situ keratomileusis (LASIK) in hyperopes with respect to the parameters of safety, efficacy, predictability, refractive error, uncorrected distance visual acuity, corrected distance visual acuity, contrast sensitivity, and higher order aberrations. Methods Twenty-two eyes of eleven participants with hyperopia with or without astigmatism were prospectively randomized to receive WF-guided LASIK with the VISX CustomVue S4 IR or WF-optimized LASIK with the WaveLight Allegretto Eye-Q 400 Hz. LASIK flaps were created using the 150-kHz IntraLase iFS. Evaluations included measurement of uncorrected distance visual acuity, corrected distance visual acuity, <5% and <25% contrast sensitivity, and WF aberrometry. Patients also completed a questionnaire detailing symptoms on a quantitative grading scale. Results There were no statistically significant differences between the groups for any of the variables studied after 12 months of follow-up (all P>0.05). Conclusion This comparative case series of 11 subjects with hyperopia showed that WF-guided and WF-optimized LASIK had similar clinical outcomes at 12 months. PMID:25419115

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.

Refraction and the axial length of the eyeball in patients with the optic disc drusen.

PubMed

Obuchowska, Iwona; Mariak, Zofia

2009-01-01

The aim of the study was to demonstrate the relationship between the optic disc drusen (ODD) and the axial length of the eyeball as well as refractive error. We examined prospectively 40 patients with ODD, 18 men and 22 women, age range from 34 to 69 years. All subjects underwent full ophthalmic examination, visual field testing and color-coded duplex sonography of the ocular vessels. Refraction was determined with an autorefractometer (Topcon RM-8000B) and further refined subjectively. Spherical equivalent refraction was calculated as the spherical dioptre plus one half of the cylindrical dioptre. Axial lengths were measured with a Sonomed ultrasound scanner model E-Z Scan AB5500. Clinical signs were observed in 65% of the eyes with drusen, among them, 38% had symptoms of visual acuity loss and all had visual fields defects. There were 21 eyes (18 eyes with and 3 without drusen), with a recorded refractive error. Significant differences in hyperopia were observed between the eyes with and without drusen (p = 0.048). The rate of occurrence of myopia did not differ significantly between affected and unaffected eyes (p = 0.06). The mean spherical equivalent refraction and axial dimensions of the eye differed significantly among the groups of eyes with and without drusen (p < 0.05). Significant differences in mean values of peak-systolic and end-diastolic velocities (p < 0.001) as well as in the resistivity index (p = 0.047) were observed between eyes with and without drusen. The optic disc drusen are often associated with shorter and hyperopic eyes. This anatomical conditions and vascular factors may contribute to pathogenesis of drusen.

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

Peripheral Refraction, Peripheral Eye Length, and Retinal Shape in Myopia.

PubMed

Verkicharla, Pavan K; Suheimat, Marwan; Schmid, Katrina L; Atchison, David A

2016-09-01

To investigate how peripheral refraction and peripheral eye length are related to retinal shape. Relative peripheral refraction (RPR) and relative peripheral eye length (RPEL) were determined in 36 young adults (M +0.75D to -5.25D) along horizontal and vertical visual field meridians out to ±35° and ±30°, respectively. Retinal shape was determined in terms of vertex radius of curvature Rv, asphericity Q, and equivalent radius of curvature REq using a partial coherence interferometry method involving peripheral eye lengths and model eye raytracing. Second-order polynomial fits were applied to RPR and RPEL as functions of visual field position. Linear regressions were determined for the fits' second order coefficients and for retinal shape estimates as functions of central spherical refraction. Linear regressions investigated relationships of RPR and RPEL with retinal shape estimates. Peripheral refraction, peripheral eye lengths, and retinal shapes were significantly affected by meridian and refraction. More positive (hyperopic) relative peripheral refraction, more negative RPELs, and steeper retinas were found along the horizontal than along the vertical meridian and in myopes than in emmetropes. RPR and RPEL, as represented by their second-order fit coefficients, correlated significantly with retinal shape represented by REq. Effects of meridian and refraction on RPR and RPEL patterns are consistent with effects on retinal shape. Patterns derived from one of these predict the others: more positive (hyperopic) RPR predicts more negative RPEL and steeper retinas, more negative RPEL predicts more positive relative peripheral refraction and steeper retinas, and steeper retinas derived from peripheral eye lengths predict more positive RPR.

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.

[Incidence of refractive errors with corrective aids subsequent selection].

PubMed

Benes, P; Synek, S; Petrová, S; Sokolová, Sidlová J; Forýtková, L; Holoubková, Z

2012-02-01

This study follows the occurrence of refractive errors in population and the possible selection of the appropriate type of corrective aids. Objective measurement and subsequent determination of the subjective refraction of the eye is on essential act in opotmetric practice. The file represented by 615 patients (1230 eyes) is divided according to the refractive error of myopia, hyperopia and as a control group are listed emetropic clients. The results of objective and subjective values of refraction are compared and statistically processed. The study included 615 respondents. To determine the objective refraction the autorefraktokeratometer with Placido disc was used and the values of spherical and astigmatic correction components, including the axis were recorded. These measurements were subsequently verified and tested subjectively using the trial lenses and the projection optotype to the normal investigative distance of 5 meters. After this the appropriate corrective aids were then recommended. Group I consists of 123 men and 195 women with myopia (n = 635) of clients with an average age 39 +/- 18,9 years. Objective refraction - sphere: -2,57 +/- 2,46 D, cylinder: -1,1 +/- 1,01 D, axis of: 100 degrees +/- 53,16 degrees. Subjective results are as follows--the value of sphere: -2,28 +/- 2,33 D, cylinder -0,63 +/- 0,80 D, axis of: 99,8 degrees +/- 56,64 degrees. Group II is represented hyperopic clients and consists of 67 men and 107 women (n = 348). The average age is 58,84 +/- 16,73 years. Objective refraction has values - sphere: +2,81 +/- 2,21 D, cylinder: -1,0 +/- 0,94 D; axis 95 degree +/- 45,4 degrees. Subsequent determination of subjective refraction has the following results - sphere: +2,28 +/- 2,06 D; cylinder: -0,49 +/- 0,85 D, axis of: 95,9 degrees +/- 46,4 degrees. Group III consists from emetropes whose final minimum viasual acuity was Vmin = 1,0 (5/5) or better. Overall, this control group is represented 52 males and 71 females (n = 247). The average age was 43 +/- 18,73 years. Objective refraction - sphere: +0,32 +/- 0,45 D; cylinder: -0,51 +/- 0,28 D, axis of: 94,7 degrees +/- 57,5 degrees. Values of objective refraction take higher values than the subsequent execution of the subjective examination of the refractive error and recommendation of the appropriate type of corrective aids. This all is in examined groups and in the individual components of refractive errors. It also confirmed the hypothesis that the population outweighs with-the-rule astigmatism, the deployment of resources according to the literature ranges from 90 degrees +/- 10 degrees. The values observed correction of refractive errors are then derived also offer the most common prescription ranges and products for the correction of given ametropia. In the selection and design corrective aids, we are often limited. Our task is then to manufacture high quality, functional and aesthetic corrective aids, you need to connect knowledge from the fields of optics, optometry and ophthalmology. Faster visual rehabilitation simplifies clients' rapid return to everyday life.

Uncorrected Hyperopia and Preschool Early Literacy: Results of the Vision in Preschoolers-Hyperopia in Preschoolers (VIP-HIP) Study.

PubMed

Kulp, Marjean Taylor; Ciner, Elise; Maguire, Maureen; Moore, Bruce; Pentimonti, Jill; Pistilli, Maxwell; Cyert, Lynn; Candy, T Rowan; Quinn, Graham; Ying, Gui-Shuang

2016-04-01

To compare early literacy of 4- and 5-year-old uncorrected hyperopic children with that of emmetropic children. Cross-sectional. Children attending preschool or kindergarten who had not previously worn refractive correction. Cycloplegic refraction was used to identify hyperopia (≥3.0 to ≤6.0 diopters [D] in most hyperopic meridian of at least 1 eye, astigmatism ≤1.5 D, anisometropia ≤1.0 D) or emmetropia (hyperopia ≤1.0 D; astigmatism, anisometropia, and myopia <1.0 D). Threshold visual acuity (VA) and cover testing ruled out amblyopia or strabismus. Accommodative response, binocular near VA, and near stereoacuity were measured. Trained examiners administered the Test of Preschool Early Literacy (TOPEL), composed of Print Knowledge, Definitional Vocabulary, and Phonological Awareness subtests. A total of 492 children (244 hyperopes and 248 emmetropes) participated (mean age, 58 months; mean ± standard deviation of the most hyperopic meridian, +3.78±0.81 D in hyperopes and +0.51±0.48 D in emmetropes). After adjustment for age, race/ethnicity, and parent/caregiver's education, the mean difference between hyperopes and emmetropes was -4.3 (P = 0.01) for TOPEL overall, -2.4 (P = 0.007) for Print Knowledge, -1.6 (P = 0.07) for Definitional Vocabulary, and -0.3 (P = 0.39) for Phonological Awareness. Greater deficits in TOPEL scores were observed in hyperopic children with ≥4.0 D than in emmetropes (-6.8, P = 0.01 for total score; -4.0, P = 0.003 for Print Knowledge). The largest deficits in TOPEL scores were observed in hyperopic children with binocular near VA of 20/40 or worse (-8.5, P = 0.002 for total score; -4.5, P = 0.001 for Print Knowledge; -3.1, P = 0.04 for Definitional Vocabulary) or near stereoacuity of 240 seconds of arc or worse (-8.6, P < 0.001 for total score; -5.3, P < 0.001 for Print Knowledge) compared with emmetropic children. Uncorrected hyperopia ≥4.0 D or hyperopia ≥3.0 to ≤6.0 D associated with reduced binocular near VA (20/40 or worse) or reduced near stereoacuity (240 seconds of arc or worse) in 4- and 5-year-old children enrolled in preschool or kindergarten is associated with significantly worse performance on a test of early literacy. Copyright © 2016 American Academy of Ophthalmology. Published by Elsevier Inc. All rights reserved.

The prevalence of amblyopia in 7-year-old schoolchildren in Iran.

PubMed

Hashemi, Hassan; Yekta, Abbasali; Jafarzadehpur, Ebrahim; Nirouzad, Fereidon; Ostadimoghaddam, Hadi; Eshrati, Babak; Mohazzab-Torabi, Saman; Khabazkhoob, Mehdi

2014-12-01

To determine the prevalence of amblyopia in schoolchildren aged 7 years in Iran, its relation with refractive errors, and its determinants. In this cross-sectional study, cluster sampling was done from elementary school students in 7 cities in Iran. In all schools, an optometrist conducted all tests, including measurement of uncorrected and corrected visual acuity, cycloplegic refraction, and cover test. In this study, amblyopia was defined as best corrected visual acuity 20/30 or less or a 2-line interocular optotype acuity difference with no pathology. Of the 4157 students selected for the study, 3675 participated and final analyses were done with data from 3547 children. The prevalence of amblyopia was 1.88% (95% CI: 1.24-2.52) (n=63). The prevalence was 1.91% (95% CI: 0.85-2.97) in boys and 1.85% (95% CI: 1.12-2.58) in girls (p=0.92). Among these cases, 60.30% (n=38) were unilateral. Also, 61.9% were strabismic, 27.0% were anisometropic, 9.5% were isometropic, and one case (1.6%) was due to congenital cataracts. Amblyopic individuals were more hypermetropic and the mean cylinder error was significantly higher. Necessary attention should be paid to amblyopia, although its prevalence in Iran is mid-range when compared with other countries. Amblyopia is more common in hyperopic and astigmatic individuals and therefore it is important to pay more attention to this refractive error during childhood. Since strabismus is the most common cause of amblyopia in Iran, children need to be checked for strabismus before the age of 5 years.

Assessment of refractive outcome of femtosecond-assisted LASIK for hyperopia correction

PubMed Central

El-Naggar, Mohamed Tarek; Hovaghimian, Dikran Gilbert

2017-01-01

Introduction Laser vision correction for hyperopia is challenging. The purpose of the study was to assess the refractive outcomes of femtosecond-assisted laser in situ keratomileusis (LASIK) for hyperopic correction using wavefront-optimized ablation profiles. Methods This retrospective case series study included 20 Egyptian patients (40 eyes) with hyperopia or hyperopic astigmatism with a mean manifest refraction spherical equivalent (MRSE) of +2.55D±1.17 (range from +1.00 to +6.00) who had uneventful femtosecond-a assisted LASIK with wavefront-optimized aspheric ablation profile using refractive surgery suite (WaveLight FS200 Femtosecond Laser and WaveLight EX500 Excimer Laser) performed in the Research Institute of Ophthalmology and International Eye Hospital, Giza, Egypt. Statistical analysis was done using Microsoft Excel (Microsoft Corporation, Seattle, WA, USA). Results The procedure significantly reduced the MRSE and cylinder post-operatively (95% were ± 0.50D and 100% ± 1.00 D), with stability of refraction and UDVA over the follow-up period (up to 12 months) after surgery. No eye lost any line of the CDVA, which reflects the excellent safety profile of the procedure; on the other hand, one eye (5%) gained one line and one eye (5%) even gained two lines. There were no significant complications during the procedure. Conclusions Femtosecond-assisted laser in situ keratomileusis for hyperopia showed predictable, effective, and safe refractive outcomes that were stable through 12 months. Longer follow-up period is required to detect any further regression PMID:28461870

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

Eighteen-year follow-up of hyperopic photorefractive keratectomy.

PubMed

Wagh, Vijay K; Dave, Reena; O'Brart, David P S; Lim, Wei S; Patel, Parul; Tam, Connan; Lee, Jennifer; Marshall, John

2016-02-01

To investigate the long-term efficacy of hyperopic photorefractive keratectomy (PRK). University Hospital, London, United Kingdom. Prospective case series. Patients with a follow-up of 18 years ± 0.7 (SD) attended for examination. All had spherical corrections with a 6.5 mm optical zone and 1.5 mm blend zone. Twenty-five patients (45 eyes) were included. The mean preoperative spherical equivalent (SE) refractive error was +4.11 ± 1.8 diopters (D) (range +1.125 to +7.25 D). Between 1 year and 18 years, in eyes that had no cataract surgery (n = 34), there was a +1.14 ± 1.48 D increase in the mean SE (P < .0002). The increase between 7.5 years and 18.0 years did not reach clinical significance (P = .1). Uncorrected distance visual acuity improved at 18 years (P < .02). Corrected distance visual acuity (CDVA) was reduced (P < .001). The efficacy index was 0.47, and the safety index was 0.83. Six eyes (18%) lost 2 lines of CDVA, of which 4 eyes had preexisting cataract. Keratometry remained stable between 1 year and 18 years (P = .2). Forty percent still had traces of peripheral haze, and 4 (9%) had Salzmann-like changes. Eleven eyes (24%) had cataract surgery and 4 (9%) had laser iridotomy. There was no evidence of ectasia. Hyperopic PRK showed an increase in hyperopic SE between 1.0 year and 7.5 years but was generally stable thereafter. The efficacy was limited. Peripheral haze was evident in 40% of cases with Salzmann-like changes in some. Ocular comorbidity in relationship to cataract was common and reduced CDVA. Dr. Marshall was a consultant to Summit Technology, Inc. No author has a financial or proprietary interest in any material or method mentioned. Copyright © 2016 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.

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.

Incidence, outcomes, and risk factors for retreatment after wavefront-optimized ablations with PRK and LASIK.

PubMed

Randleman, J Bradley; White, Alfred J; Lynn, Michael J; Hu, Michelle H; Stulting, R Doyle

2009-03-01

To analyze and compare retreatment rates after wavefront-optimized photorefractive keratectomy (PRK) and LASIK and determine risk factors for retreatment. A retrospective chart review was performed to identify patients undergoing PRK or LASIK with the wavefront-optimized WaveLight platform from January 2005 through December 2006 targeted for a piano outcome and to determine the rate and risk factors for retreatment surgery in this population. Eight hundred fifty-five eyes were analyzed, including 70 (8.2%) eyes with hyperopic refractions and 785 (91.8%) eyes with myopic refractions. After initial treatment, 72% of eyes were 20/20 or better and 99.5% were 20/40 or better. To improve uncorrected visual acuity, 54 (6.3%) eyes had retreatments performed. No significant differences in retreatment rates were noted based on age (P = .15), sex (P = .8), eye (P = .3), PRK versus LASIK (P = 1.0), room temperature (P = .1) or humidity (P = .9), and no correlation between retreatment rate and month or season of primary surgery (P = .4). There was no correlation between degree of myopia and retreatment rate. Eyes were significantly more likely to undergo retreatment if they were hyperopic (12.8% vs 6.0%, P = .006) or had astigmatism > or = 1.00 diopter (D) (9.1% vs 5.3%, P = .04). Retreatment rate was 6.3% with the WaveLight ALLEGRETTO WAVE excimer laser. This rate was not influenced by age, sex, corneal characteristics, or environmental factors. Eyes with hyperopic refractions or astigmatism > or = 1.00 D were more likely to undergo retreatment.

The Correlation between Angle Kappa and Ocular Biometry in Koreans

PubMed Central

Choi, Se Rang

2013-01-01

Purpose To investigate normative angle kappa data and to examine whether correlations exist between angle kappa and ocular biometric measurements (e.g., refractive error, axial length) and demographic features in Koreans. Methods Data from 436 eyes (213 males and 223 females) were analyzed in this study. The angle kappa was measured using Orbscan II. We used ocular biometric measurements, including refractive spherical equivalent, interpupillary distance and axial length, to investigate the correlations between angle kappa and ocular biometry. The IOL Master ver. 5.02 was used to obtain axial length. Results The mean patient age was 57.5 ± 12.0 years in males and 59.4 ± 12.4 years in females (p = 0.11). Angle kappa averaged 4.70 ± 2.70 degrees in men and 4.89 ± 2.14 degrees in women (p = 0.48). Axial length and spherical equivalent were correlated with angle kappa (r = -0.342 and r = 0.197, respectively). The correlation between axial length and spherical equivalent had a negative correlation (r = -0.540, p < 0.001). Conclusions Angle kappa increased with spherical equivalent and age. Thus, careful manipulation should be considered in older and hyperopic patients when planning refractive or strabismus surgery. PMID:24311927

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.

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

Chicks use changes in luminance and chromatic contrast as indicators of the sign of defocus

PubMed Central

Rucker, Frances J.; Wallman, Josh

2012-01-01

As the eye changes focus, the resulting changes in cone contrast are associated with changes in color and luminance. Color fluctuations should simulate the eye being hyperopic and make the eye grow in the myopic direction, while luminance fluctuations should simulate myopia and make the eye grow in the hyperopic direction. Chicks without lenses were exposed daily (9 a.m. to 5 p.m.) for three days on two consecutive weeks to 2 Hz sinusoidally modulated illumination (mean illuminance of 680 lux) to one of the following: in-phase modulated luminance flicker (LUM), counterphase-modulated red/green (R/G Color) or blue/yellow flicker (B/Y Color), combined color and luminance flicker (Color + LUM), reduced amplitude luminance flicker (Low LUM), or no flicker. After the three-day exposure to flicker, chicks were kept in a brooder under normal diurnal lighting for four days. Changes in the ocular components were measured with ultrasound and with a Hartinger Coincidence Refractometer (aus Jena, Jena, East Germany. After the first three-day exposure, luminance flicker produced more hyperopic refractions (LUM: 2.27 D) than did color flicker (R/G Color: 0.09 D; B/Y Color: −0.25 D). Changes in refraction were mainly due to changes in eye length, with color flicker producing much greater changes in eye length than luminance flicker (R/G Color: 102 μm; B/Y Color: 98 μm; LUM: 66 μm). Our results support the hypothesis that the eye can differentiate between hyperopic and myopic defocus on the basis of the effects of change in luminance or color contrast. PMID:22715194

Negative Lens–Induced Myopia in Infant Monkeys: Effects of High Ambient Lighting

PubMed Central

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

2013-01-01

Purpose. To determine whether high light levels, which have a protective effect against form-deprivation myopia, also retard the development of lens-induced myopia in primates. Methods. Hyperopic defocus was imposed on 27 monkeys by securing −3 diopter (D) lenses in front of one eye. The lens-rearing procedures were initiated at 24 days of age and continued for periods ranging from 50 to 123 days. Fifteen of the treated monkeys were exposed to normal laboratory light levels (∼350 lux). For the other 12 lens-reared monkeys, auxiliary lighting increased the illuminance to 25,000 lux for 6 hours during the middle of the daily 12 hour light cycle. Refractive development, corneal power, and axial dimensions were assessed by retinoscopy, keratometry, and ultrasonography, respectively. Data were also obtained from 37 control monkeys, four of which were exposed to high ambient lighting. Results. In normal- and high-light-reared monkeys, hyperopic defocus accelerated vitreous chamber elongation and produced myopic shifts in refractive error. The high light regimen did not alter the degree of myopia (high light: −1.69 ± 0.84 D versus normal light: −2.08 ± 1.12 D; P = 0.40) or the rate at which the treated eyes compensated for the imposed defocus. Following lens removal, the high light monkeys recovered from the induced myopia. The recovery process was not affected by the high lighting regimen. Conclusions. In contrast to the protective effects that high ambient lighting has against form-deprivation myopia, high artificial lighting did not alter the course of compensation to imposed defocus. These results indicate that the mechanisms responsible for form-deprivation myopia and lens-induced myopia are not identical. PMID:23557736

[Analysis of refractive status after cataract surgery in age-related cataract patients with shallow anterior chamber].

PubMed

Yang, Fei; Hou, Xianru; Wu, Huijuan; Bao, Yongzhen

2014-02-01

To evaluate the characteristics of postoperative refractive status in age-related cataract patients with shallow anterior chamber and the correlation between pre-operative anterior chamber depth and postoperative refractive status. Prospective case-control study. Sixty-eight cases (90 eyes) with age-related cataract were recruited from October 2010 to January 2012 in People's Hospital Peking University including 28 cases (34 eyes) in control group and 40 cases (56 eyes) in shallow anterior chamber group according to anterior chamber depth (ACD) measured by Pentacam system. Axial length and keratometer were measured by IOL Master and intraocular lens power was calculated using SRK/T formula. Postoperative refraction, ACD and comprehensive eye examination were performed at 1 month and 3 months after cataract surgery. Using SPSS13.0 software to establish a database, the two groups were compared with independent samples t-test and correlation analysis were performed with binary logical regression. The postoperative refractive deviation at 1 month were (-0.39 ± 0.62) D in control group and (+0.73 ± 0.26) D in shallow anterior chamber group respectively which present statistical significance between the two groups (P = 0.00, t = 3.67); the postoperative refractive deviation in 3 month was (-0.37 ± 0.62) D in control group and (+0.79 ± 0.28) D in shallow anterior chamber group operatively which present statistical significance between the two groups (P = 0.00, t = 3.33). In shallow anterior chamber group, with the shallower of ACD, the greater of refractive deviation (P = 0.00, r1 month = -0.57, r3 months = -0.61). Hyperopic shift existed in age-related cataract patients with shallow anterior chamber and the shallower of ACD was, the greater of hyperopic shift happened.

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.

Six-month clinical outcomes after hyperopic correction with the SCHWIND AMARIS Total-Tech laser

PubMed Central

Arbelaez, María Clara; Vidal, Camila; Arba Mosquera, Samuel

2011-01-01

Purpose To evaluate postoperative clinical outcomes, and corneal High Order Aberrations, among eyes with hyperopia up to +5 D of spherical equivalent, that have undergone LASIK treatments using the SCHWIND AMARIS laser system. Methods At six-month follow-up, 100 eyes with preoperative hyperopia or hyperopic astigmatism up to +5 D of spherical equivalent were retrospectively analysed. Standard examinations, pre- and postoperative wavefront analysis with a corneal-wavefront-analyzer (OPTIKON Scout) were performed. Aberration-Free aspheric treatments were planned with Custom Ablation Manager software and ablations performed using the SCHWIND AMARIS flying-spot excimer laser system (both SCHWIND eye-tech-solutions). LASIK flaps were created using a LDV femtosecond laser (Ziemer Group) in all cases. Clinical outcomes were evaluated in terms of predictability, refractive outcome, safety, and wavefront aberration. Results At six month, 90 % of eyes achieved ≥ 20/25 UCVA and 44 % achieved ≥ 20/16 UCVA. Seventy-four percent of eyes were within ± 0.25D of spherical equivalent and 89 % within ± 0.50D, with 94 % within 0.50D of astigmatism. Mean spherical equivalent was −0.12 ± 0.51D and 0.50 ± 0.51D for the astigmatism. Fifty-two percent of eyes improved BSCVA vs. only 19 % losing lines of BSCVA. Predictability slope for refraction was 1.03 and intercept +0.01 D. On average, negative corneal spherical aberrations were significantly increased by the treatments, no other aberration terms changed from pre- to postoperative values. Conclusions LASIK for hyperopia and hyperopic astigmatism with SCHWIND AMARIS yields very satisfactory visual outcomes. Preoperative refractions were postoperatively reduced to subclinical values with no clinically relevant induction of corneal HOA.

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.

[Laser thermokeratoplasty in the treatment of hyperopia in children].

PubMed

Kulikova, I L; Pashtaev, N P; Suslikov, S V

2006-01-01

The effectiveness, safety, and stability of multimodality treatment for hyperopia, hyperopic and mixed astigmatism complicated by amblyopia and anisometropia were studied in 117 patients (117 eyes) aged 9 to 16 years, by using the new laser units "Lik-100" and "Glasser" at 1.54 microm. The patients were divided into 3 groups: 1) 43 patients (43 eyes) with hyperopia, spheric anisometropia and amblyopia; 2) 38 patients (38 eyes) with hyperopia, simple and complicated hyperopic astigmatism, astigmatic anisometropia, and amblyopia; 3) 36 patients (36 eyes) with hyperopia, simple and complicated hyperopic astigmatism, mixed anisometropia, and amblyopia. All the groups underwent multimodality treatment involving laser thermokeratoplasty and drug therapy for amblyopia. In children and adolescents, the refraction effect was 2.99 and 3.61 (mean 3.37 +/- 0.60) diopters, respectively. Astigmatism diminished by 2.01 diopters (63%) in children and by 2.62 diopters (79%) in adolescents (mean 2/35 diopters). The predictability of a refraction effect in the range of +/- 0.5 diopters averaged 77% in all the groups. Anisometropia diminished by an average of 2.88 +/- 0.8 diopters, which was 85% of the baseline data (the upper range of residual refraction was not more than 1.5 diopters. In all the groups, uncorrectable visual acuity increased by an average of 0.36 diopters (0.43 and 0.4 diopters in children and adolescents, respectively); correctable visual acuity increased by an average of 0.22 diopters (0.36 and 0.31 diopters in children and adolescents, respectively). Loss of correctable visual acuity lines did not greater than 2.7% (5 eyes). That of endothelial cells was not more than 6-8%. The angle of squint strabismus could be decreased or corrected in 79% after treatment. Binocular vision restored in 57%.

Space flight-associated neuro-ocular syndrome (SANS).

PubMed

Lee, Andrew G; Mader, Thomas H; Gibson, C Robert; Brunstetter, Tyson J; Tarver, William J

2018-03-12

Interesting novel and somewhat perplexing physiologic and pathologic neuro-ocular findings have been documented in astronauts during and after long duration space flight (LDSF). These findings collectively have been termed the "space flight-associated neuro-ocular syndrome" (SANS). The National Aeronautics and Space Administration (NASA) in the United States has meticulously and prospectively documented the clinical, ultrasound, optical coherence tomography imaging, and radiographic findings of SANS including unilateral and bilateral optic disc edema, globe flattening, choroidal and retinal folds, hyperopic refractive error shifts, and nerve fiber layer infarcts (i.e., cotton wool spots). NASA and collaborating researchers continue to study SANS in preparation for future manned missions to space, including continued trips to the ISS, a return to the moon, or perhaps new voyages to the asteroid belt, or the planet, Mars.

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.

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.

Developmental compensation of imposed astigmatism is not initiated by astigmatic accommodation in chickens.

PubMed

Thomas, S; Schaeffel, F

2000-01-01

It is not clear whether emmetropization is confined to spherical refractive errors, or whether astiqmatic errors are also corrected via visual feedback. Experimental results from the animal model of the chicken are equivocal since compensation of imposed astimatic defocus was found in some but not all studies. Astigmatism could only be compensated by changes in the geometry of the cornea or lens. One has tested whether astigmatic spectacle lenses induce astigmatic accommodation as a possible first step of long-lasting compensation. Thirty-five chickens were treated with cylinder lenses (+3/0D or -3/0D) for 5 h. Refractions were determined at 1.38 m distance without cycloplegia in hand-held chicks before attaching the lenses, with the lenses on (0 h), and after 3 and 5 h, and after removal of the lenses. Spheres (S), cylinders (C) and axes (A) were determined using infrared photoretinocopy in three axes (the 'PowerRefractor', equipped with a 135 mm lens). (1) The performance of the 'PowerRefractor' was tested in the chickens with trial lenses and gave correct refractions. (2) Astigmatic trial lenses induced refractive errors as expected from their powers in the case of +3/0D lenses: (S) +3.26 +/- 0.93D, (C) -3.45 +/- 0.87D). In the case of -3/0D lenses, slightly more hyperopic spheres were induced (refractions (S) +4.5 +/- 0.48D) but the cylinders were still as expected (-3.25 +/- 0.49D). The axes of astigmatism were correctly reproduced, since rotating the lenses changed the axes of the induced cylinders as expected. (3) Neither after 3 nor after 5 h of lens wear were there significant changes in the axes or the magnitude of astigmatism. Directly after removal of the lens, the refractions did not differ from their start-up values (with +3/0D lenses: (S) +3.31 +/- 1.05D vs. +3.22 +/- 0.76D, (C) -1.19 +/- 1.77D vs. -0.65 +/- 0.94D, (A) 96 +/- 49 vs. 113 +/- 45 deg; with -3/0D lenses: (S) 2.63 +/- 1.12D vs. 2.97 +/- 0.94D, (C) -1.11 +/- 1.15D vs. -0.53 +/- 0.56D, (A) 78 +/- 24 vs. 131 +/- 35 deg). The most intuitive mechanism for compensation of astigmatic refractive errors, astigmatic accommodation, could not be demonstrated in chickens. In light of this finding, it seems unlikely that a visually controlled mechanism is operating during development to reduced astigmatism by changing corneal or lenticular growth.

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.

Comparison of Newer IOL Power Calculation Methods for Eyes With Previous Radial Keratotomy

PubMed Central

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

2016-01-01

Purpose To evaluate the accuracy of the optical coherence tomography–based (OCT formula) and Barrett True K (True K) intraocular lens (IOL) calculation formulas in eyes with previous radial keratotomy (RK). Methods In 95 eyes of 65 patients, using the actual refraction following cataract surgery as target refraction, the predicted IOL power for each method was calculated. The IOL prediction error (PE) was obtained by subtracting the predicted IOL power from the implanted IOL power. The arithmetic IOL PE and median refractive PE were calculated and compared. Results All formulas except the True K produced hyperopic IOL PEs at 1 month, which decreased at ≥4 months (all P < 0.05). For the double-K Holladay 1, OCT formula, True K, and average of these three formulas (Average), the median absolute refractive PEs were, respectively, 0.78 diopters (D), 0.74 D, 0.60 D, and 0.59 D at 1 month; 0.69 D, 0.77 D, 0.77 D, and 0.61 D at 2 to 3 months; and 0.34 D, 0.65 D, 0.69 D, and 0.46 D at ≥4 months. The Average produced significantly smaller refractive PE than did the double-K Holladay 1 at 1 month (P < 0.05). There were no significant differences in refractive PEs among formulas at 4 months. Conclusions The OCT formula and True K were comparable to the double-K Holladay 1 method on the ASCRS (American Society of Cataract and Refractive Surgery) calculator. The Average IOL power on the ASCRS calculator may be considered when selecting the IOL power. Further improvements in the accuracy of IOL power calculation in RK eyes are desirable. PMID:27409468

Astigmatism in Monkeys with Experimentally Induced Myopia or Hyperopia

PubMed Central

KEE, CHEA-SU; HUNG, LI-FANG; QIAO-GRIDER, YING; RAMAMIRTHAM, RAMKUMAR; SMITH, EARL L.

2006-01-01

Purpose Astigmatism is the most common ametropia found in humans and is often associated with large spherical ametropias. However, little is known about the etiology of astigmatism or the reason(s) for the association between spherical and astigmatic refractive errors. This study examines the frequency and characteristics of astigmatism in infant monkeys that developed axial ametropias as a result of altered early visual experience. Methods Data were obtained from 112 rhesus monkeys that experienced a variety of lens-rearing regimens that were intended to alter the normal course of emmetropization. These visual manipulations included form deprivation (n = 13); optically imposed defocus (n = 48); and continuous ambient lighting with (n = 6) or without optically imposed defocus (n = 6). In addition, data from 19 control monkeys and 39 infants reared with an optically imposed astigmatism were used for comparison purposes. The lens-rearing period started at approximately 3 weeks of age and ended by 4 to 5 months of age. Refractive development for all monkeys was assessed periodically throughout the treatment and subsequent recovery periods by retinoscopy, keratometry, and A-scan ultrasonography. Results In contrast to control monkeys, the monkeys that had experimentally induced axial ametropias frequently developed significant amounts of astigmatism (mean refractive astigmatism = 0.37 ± 0.33 D [control] vs. 1.24 ± 0.81 D [treated]; two-sample t-test, p < 0.0001), especially when their eyes exhibited relative hyperopic shifts in refractive error. The astigmatism was corneal in origin (Pearson’s r; p < 0.001 for total astigmatism and the JO and J45 components), and the axes of the astigmatism were typically oblique and bilaterally mirror symmetric. Interestingly, the astigmatism was not permanent; the majority of the monkeys exhibited substantial reductions in the amount of astigmatism at or near the end of the lens-rearing procedures. Conclusions In infant monkeys, visual conditions that alter axial growth can also alter corneal shape. Similarities between the astigmatic errors in our monkeys and some astigmatic errors in humans suggest that vision-dependent changes in eye growth may contribute to astigmatism in humans. PMID:15829845

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

Attention and Visual Motor Integration in Young Children with Uncorrected Hyperopia.

PubMed

Kulp, Marjean Taylor; Ciner, Elise; Maguire, Maureen; Pistilli, Maxwell; Candy, T Rowan; Ying, Gui-Shuang; Quinn, Graham; Cyert, Lynn; Moore, Bruce

2017-10-01

Among 4- and 5-year-old children, deficits in measures of attention, visual-motor integration (VMI) and visual perception (VP) are associated with moderate, uncorrected hyperopia (3 to 6 diopters [D]) accompanied by reduced near visual function (near visual acuity worse than 20/40 or stereoacuity worse than 240 seconds of arc). To compare attention, visual motor, and visual perceptual skills in uncorrected hyperopes and emmetropes attending preschool or kindergarten and evaluate their associations with visual function. Participants were 4 and 5 years of age with either hyperopia (≥3 to ≤6 D, astigmatism ≤1.5 D, anisometropia ≤1 D) or emmetropia (hyperopia ≤1 D; astigmatism, anisometropia, and myopia each <1 D), without amblyopia or strabismus. Examiners masked to refractive status administered tests of attention (sustained, receptive, and expressive), VMI, and VP. Binocular visual acuity, stereoacuity, and accommodative accuracy were also assessed at near. Analyses were adjusted for age, sex, race/ethnicity, and parent's/caregiver's education. Two hundred forty-four hyperopes (mean, +3.8 ± [SD] 0.8 D) and 248 emmetropes (+0.5 ± 0.5 D) completed testing. Mean sustained attention score was worse in hyperopes compared with emmetropes (mean difference, -4.1; P < .001 for 3 to 6 D). Mean Receptive Attention score was worse in 4 to 6 D hyperopes compared with emmetropes (by -2.6, P = .01). Hyperopes with reduced near visual acuity (20/40 or worse) had worse scores than emmetropes (-6.4, P < .001 for sustained attention; -3.0, P = .004 for Receptive Attention; -0.7, P = .006 for VMI; -1.3, P = .008 for VP). Hyperopes with stereoacuity of 240 seconds of arc or worse scored significantly worse than emmetropes (-6.7, P < .001 for sustained attention; -3.4, P = .03 for Expressive Attention; -2.2, P = .03 for Receptive Attention; -0.7, P = .01 for VMI; -1.7, P < .001 for VP). Overall, hyperopes with better near visual function generally performed similarly to emmetropes. Moderately hyperopic children were found to have deficits in measures of attention. Hyperopic children with reduced near visual function also had lower scores on VMI and VP than emmetropic children.

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.

Influence of fogging lenses and cycloplegia on open-field automatic refraction.

PubMed

Queirós, A; González-Méijome, J; Jorge, J

2008-07-01

To compare refractive values measured with and without cycloplegia, or with fogging lenses, using an open-field auto-refractor. One hundred and forty-two young adults were enrolled from a university population; 96 were female (67.6%) and 46 were male (32.4%), the age range was 18-26 years (mean 22.3 +/- 3.7 years). The refraction measurement was obtained for the right eye of each subject with the Grand Seiko Auto Ref/Keratometer WAM-5500 (GS) under three conditions, always in this sequence: (1) without cycloplegia (GS), (2) without cycloplegia but using a + 2.00 D fogging lens (GS_2D) and (3) with cycloplegia (GS_cycl). When the average values of spherical equivalent were compared, both accommodation control strategies were almost equally successful: GS, M = -0.85 +/- 2.21 D; GC_2D, M = -0.53 +/- 2.10 D and GS_cycl, M = -0.57 +/- 2.24 D (Kruskal-Wallis test, p < 0.001). When the results were analysed separately for different refractive groups, emmetropes and hyperopes show statistically significant differences while myopes did not. When both accommodation strategies were compared there was a trend for more myopic subjects to display more negative values under cycloplegia, while low myopes, emmetropes and hyperopes tend to display more negative values with the +2.00 D fogging lenses, suggesting this was less effective for accommodation control. Over-refraction through +2.00 D fogging lenses is useful to achieve additional relaxation of the accommodative response in a similar way to cycloplegia when open-field autorefraction is performed in young adults.

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.

Refractive Outcomes of 20 Eyes Undergoing ICL Implantation for Correction of Hyperopic Astigmatism.

PubMed

Coskunseven, Efekan; Kavadarli, Isilay; Sahin, Onurcan; Kayhan, Belma; Pallikaris, Ioannis

2017-09-01

To analyze 1-week, 1-month, and 12-month postoperative refractive outcomes of eyes that under-went ICL implantation to correct hyperopic astigmatism. The study enrolled 20 eyes of patients with an average age of 32 years (range: 21 to 40 years). The outcomes of spherical and cylindrical refraction, uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), vault, and angle parameters were evaluated 1 week, 1 month, and 12 months postoperatively. The preoperative mean UDVA was 0.15 ± 0.11 (decimal) (20/133 Snellen) and increased to 0.74 ± 0.25 (20/27 Snellen) postoperatively, with a change of 0.59 (decimal) (20/33.9 Snellen) (P < .0001), which was statistically significant. The preoperative mean CDVA was 0.74 ± 0.25 (decimal) (20/27 Snellen) and increased to 0.78 ± 0.21 (20/25 Snellen), with a change of 0.03 (decimal) (20/666 Snellen) (P < .052), which was not statistically significant. The mean preoperative sphere was 6.86 ± 1.77 diopters (D) and the mean preoperative cylinder was -1.44 ± 0.88 D. The mean 12-month postoperative sphere decreased to 0.46 ± 0.89 D (P < .001) and cylinder decreased to -0.61 ± 0.46 D (P < .001), with a change of 6.40 D, both of which were statistically significant. The mean 1-month postoperative vault was 0.65 ± 0.13 mm and decreased to 0.613 ± 0.10 mm at 1 year postoperatively, with a change of 0.44 mm (P < .003). The preoperative/12-month and 1-month/12-month trabecular-iris angle (TIA), trabecular-iris space area 500 mm from the scleral spur (TISA500), and angle opening distance 500 mm from the scleral spur (AOD500) values were analyzed nasally, temporally, and inferiorly. All differences were statistically significant between preoperative/12-month analysis. The only differences between 1- and 12-month analysis were on TISA500 inferior (P < .002) and AOD500 nasal (0.031) values. ICL hyperopic toric implantation is a safe method and provides stable refractive outcomes in patients with high hyperopia (up to 10.00 D) and astigmatism (up to 6.00 D). [J Refract Surg. 2017;33(9):604-609.]. Copyright 2017, SLACK Incorporated.

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.

Clinical study of the influence of preoperative wearing time on postoperative effects in children with partially accommodative esotropia.

PubMed

Jiang, Danni; Han, Dong; Zhang, Jiahuan; Pei, Tianxu; Zhao, Qi

2018-05-01

The aim of this study was to evaluate the influence of the preoperative wearing time on the postoperative effect in children with partially accommodative esotropia.Sixty children with partially accommodative esotropia who visited our hospital were placed in full cycloplegic refraction by using 1% Atropine eye gel and then wore full hyperopic correction glasses. Children were divided into groups A and B according to the preoperative wearing time. The visual acuity, eye position, and results of the synoptophore and Titmus stereoacuity tests were recorded before and half a year after the surgery in each group, and appropriate statistical analyses were conducted.Half a year after the operation, 54 cases achieved orthotropia when wearing full hyperopic correction glasses. One case was overcorrected. Five cases were undercorrected. The results of the synoptophore and Titmus stereoacuity test showed that there was no significant difference between postoperative outcomes for patients who wore glasses for half a year and for 1 year before the operation.For children with partially accommodative esotropia, surgery should be used to correct the eye position after wearing full hyperopic correction glasses for half a year to improve the eye position and binocular vision as early as possible. If the operation cannot be completed after the patient wears full hyperopic correction glasses for half a year due to various subjective and objective factors, a good postoperative effect can be obtained if the patients receive surgery after wearing full hyperopic correction glasses for 1 year.

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.

[Comparison of keratometric values and corneal eccentricity of myopia, hyperopia and emmetropia].

PubMed

Benes, P; Synek, S; Petrová, S

2011-01-01

The aim of this work is to compare the findings of keratometric values and their differences at various ametropias. The eccentricity of the cornea in the sense compared to the possible influence of refraction of the eye is topographically observed. Groups of myopia, hyperopia and emmetropia are always represented 100 subjects, i.e. 600 eyes. The results of these measurements are mutually compared and statistically processed. The studied cohort a total of 300 clients enrolled. To measure the steepest (r1) and flattest meridian (r2) and to determine corneal eccentricity was used autorefraktokeratometer with Placido disc (KR 8100P, Topcon, Japan). The obtained data were processed with appropriate software and statistically evaluated. Group A consisted of 100 myopes (n = 200), 35 men and 65 women, average age 37.3 +/- 18.7 years (min. 10 years, max. 87 years). Objective refractive error - sphere: - 2.9 +/- 2.27 D (min.-0.25 D, -14.5 D max), cylinder: -0.88 +/- 0.75 D (min. -0.25 D, up to -5.0 D). Keratametry in this group is as follows: radius of curvature of the cornea in the front area of the steepest meridian 7.62 +/- 0.28 mm (min. 6.96 mm, max. 8.44 mm) and the flattest meridian is 7.76 +/- 0.3 mm (min. 7.08 mm, max 8.75 mm). The mean eccentricity was 0.37 +/- 0.12 (min 0.00, max. 0.79). Group B consisting of 100 hyperopic subjects (n = 200), 40 men and 60 women, average age 61.6 +/- 15 years (min. 21 years, max 88 years). Objective refraction in this group -sphere: +2.71 +/- 1.6 D (at least +0.25 D, up to +9.0 D), cylinder: -1.0 +/- 0.9 D (min. -0.25 D, max. -5.75 D).Corneal surface curvature in two main sections according keratometric measurement looks as follows: the steepest meridian is 7.67 +/- 0.29 mm (min. 6.99 mm, max. 8.62 mm), the flattest meridian then 7.81 +/- 0.29 mm (min. 7.10 mm, max. 8.70 mm). The value of the median eccentricity for these hundred hyperopes is 0.37 +/- 0.14 (min. 0.00; max 0.86). The third group C consists of 100 emetropic subjects (n = 200), then clients without refractive errors who achieve without corrective aids Vmin = 1.0. This group is composed of 42 men and 58 women, mean age 41.4 +/- 17.8 years (min. 3 years, max. 82 years). Measured values of objective refraction - sphere: +0.32 +/- 0.47 D (at least -1.75 D, up to +1.5 D), cylinder: -0.28 +/- 0.45 D (min. -1.25 D, up to +1.25 D). Keratometry values measured at the corneal surface in two perpendicular cross-section are: steepest meridian corresponds to the radius of curvature of 7.72 +/- 0.26 mm (min. 6.91 mm, max. 8.32 mm), the flattest meridian reaches values 7.83 +/- 0.25 mm (min. 7.10 mm, max. 8.53 mm). The median eccentricity is represented by the observed values of 0.36 +/- 0.11 (min 0.00; max. 0.57). Due to the validity of the results from the groups as unsuitable respondents with corneal astigmatism greater than -1.0 D were subsequently eliminated. Keratometry as well as topography is one of the fundamental methods of measuring corneal front surface. Their proportions are essential for the proper parameters selection, especially with contact lenses as one of the possible means intended to correct refractive errors. The study subjects were not included in any load condition cornea, purulent conjunctivitis, blepharitis, after refractive surgery or other eye symptoms.

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.

Hyperopic laser in situ keratomileusis: comparison of femtosecond laser and mechanical microkeratome flap creation.

PubMed

Antonios, Rafic; Arba Mosquera, Samuel; Awwad, Shady T

2015-08-01

To evaluate and compare the refractive predictability and stability of laser in situ keratomileusis (LASIK) flap creation performed with a femtosecond laser and with a mechanical microkeratome to correct mild to moderate hyperopia. American University of Beirut Medical Center, Beirut, Lebanon. Retrospective case series. Patients who had hyperopic LASIK treatment using the Amaris excimer laser were included. Eyes in which the LDV femtosecond laser was used for flap creation were compared with eyes in which the Moria M2 microkeratome was used. The microkeratome group comprised 53 eyes and the femtosecond laser group, 72 eyes. Baseline characteristics were similar between groups (P > .05). The mean spherical equivalent (SE) deviation from target 1 week postoperatively was -0.08 diopter (D) ± 0.58 (SD) in the femtosecond laser group and -0.06 ± 0.87 D in the microkeratome group (P = .92). Thereafter, the mean SE deviation from target increased gradually and by 6 months postoperatively was +0.30 ± 0.50 D and +0.70 ± 0.71 D, respectively (P = .001). The correlation between the achieved and the attempted SE refraction was better in the femtosecond laser group (R(2) = 0.806) than the microkeratome group (R(2) = 0.671). Using the same nomogram, the short-term refractive outcomes of hyperopic LASIK with flap creation performed with the femtosecond laser were comparable to those for the microkeratome; however, the femtosecond group showed significantly better stability over the 6-month follow-up and better predictability, as reflected by a lower standard deviation and stronger Pearson correlation. Dr. Arba Mosquera is an employee of Schwind eye-tech-solutions GmbH and Co. KG. No other 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.

Application of the holmium:YAG laser for refractive surgery: an update of clinical progress

NASA Astrophysics Data System (ADS)

Thompson, Vance M.; Durrie, Daniel S.; Hunkeler, John D.; Hurt, Art C., III; Mann, P. M.; Seiler, Theo; King, Michael C.; Sacharoff, Alex C.; Muller, David F.

1993-06-01

We describe the results of a 30 patient Phase I clinical trial using the Laser Thermokeratoplasty (LTK) treatment for correction of hyperopic astigmatism. We report the results for 29 patients who have reached 2 months post-operative. The average pre-op cylinder was reduced from -3.06 Diopters (D) to -1.21 D. Average spherical equivalent (SE) refractive error was reduced from +2.28 to +1.34 D. Six patients have reached 4 months post-op; the average cylinder of these patients has been reduced from -1.92 to -0.79 D while the average SE has been reduced from +1.29 to +0.31 D. Although patients had varying degrees of astigmatism pre-op, all treatments were performed with identical parameters (intended to correct a small amount of astigmatism) to enable us to determine the effect of the procedure without the influence of other factors such as varying zone diameter or laser fluence. The predictability and stability of the LTK procedure are supported by a recent study of 20 patients treated in Germany by Seiler for low to moderate degrees (2 - 4 D) of hyperopia. After 6 months post-op, 16 of 20 patients are within +/- 1 D of the attempted correction. Longer-term follow-up will be necessary to determine the ultimate refractive stability of the LTK procedure.

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.

Space Flight-Associated Neuro-ocular Syndrome.

PubMed

Lee, Andrew G; Mader, Thomas H; Gibson, C Robert; Tarver, William

2017-09-01

New and unique physiologic and pathologic systemic and neuro-ocular responses have been documented in astronauts during and after long-duration space flight. Although the precise cause remains unknown, space flight-associated neuro-ocular syndrome (SANS) has been adopted as an appropriate descriptive term. The Space Medicine Operations Division of the US National Aeronautics and Space Administration (NASA) has documented the variable occurrence of SANS in astronauts returning from long-duration space flight on the International Space Station. These clinical findings have included unilateral and bilateral optic disc edema, globe flattening, choroidal and retinal folds, hyperopic refractive error shifts, and nerve fiber layer infarcts. The clinical findings of SANS have been correlated with structural changes on intraorbital and intracranial magnetic resonance imaging and in-flight and terrestrial ultrasonographic studies and ocular optical coherence tomography. Further study of SANS is ongoing for consideration of future manned missions to space, including a return trip to the moon or Mars.

OPTICS OF CONDUCTIVE KERATOPLASTY: IMPLICATIONS FOR PRESBYOPIA MANAGEMENT

PubMed Central

Hersh, Peter S

2005-01-01

Purpose To define the corneal optics of conductive keratoplasty (CK) and assess the clinical implications for hyperopia and presbyopia management. Methods Four analyses were done. (1) Multifocal effects: In a prospective study of CK, uncorrected visual acuity (UCVA) for a given refractive error in 72 postoperative eyes was compared to control eyes. (2) Surgically induced astigmatism (SIA): 203 eyes were analyzed for magnitude and axis of SIA. (3) Higher-order optical aberrations: Corneal higher-order optical aberrations were assessed for 36 eyes after CK and a similar patient population after hyperopic laser in situ keratomileusis (LASIK). (4) Presbyopia clinical trial: Visual acuity, refractive result, and patient questionnaires were analyzed for 150 subjects in a prospective, multicenter clinical trial of presbyopia management with CK. Results (1) 63% and 82% of eyes after CK had better UCVA at distance and near, respectively, than controls. (2) The mean SIA was 0.23 diopter (D) steepening at 175° (P < .001); mean magnitude was 0.66 D (SD, 0.43 D). (3) After CK, composite fourth- and sixth-order spherical aberration increased; change in (Z12) spherical aberration alone was not statistically significant. When compared to hyperopic LASIK, there was a statistically significant increase in composite fourth- and sixth-order spherical aberration (P < .01) and spherical aberration (Z12) alone (P < .02); spherical aberration change was more prolate after CK. (4) After the CK monovision procedure, 80% of patients had J3 or better binocular UCVA at near; 84% of patients were satisfied. Satisfaction was associated with near UCVA of J3 or better in the monovision eye (P = .001) and subjectively good postoperative depth perception (P = .038). Conclusions CK seems to produce functional corneal multifocality with definable introduction of SIA and higher-order optical aberrations, and development of a more prolate corneal contour. These optical factors may militate toward improved near vision function. PMID:17057812

Macular retinal and choroidal thickness in unilateral amblyopia using swept-source optical coherence tomography.

PubMed

Araki, Syunsuke; Miki, Atsushi; Goto, Katsutoshi; Yamashita, Tsutomu; Takizawa, Go; Haruishi, Kazuko; Ieki, Yoshiaki; Kiryu, Junichi; Yaoeda, Kiyoshi

2017-09-15

To investigate macular retinal and choroidal thickness in amblyopic eyes compared to that in fellow and normal eyes using swept-source optical coherence tomography (SS-OCT). This study examined 31 patients with hyperopic anisometropic amblyopia (6.9 ± 3.8 years, mean ± standard deviation), 15 patients with strabismic amblyopia without anisometropia (7.9 ± 4.2 years), and 24 age-matched controls (7.8 ± 3.3 years). Retinal and choroidal thickness was measured by 3D scans using SS-OCT. A 6-mm area around the fovea was automatically analyzed using the Early Treatment Diabetic Retinopathy Study map. The thickness from SS-OCT was corrected for magnification error using individual axial length, spherical refraction, cylinder refraction, and corneal radius. Retinal thickness was divided into the macular retinal nerve fiber layer (mRNFL), ganglion cell layer + inner plexiform layer (GCL+IPL), ganglion cell complex (GCC), and the inner limiting membrane to the retinal pigment epithelium (ILM-RPE) thickness. Retinal and choroidal thickness was compared among amblyopic, fellow, and normal eyes. In both amblyopia groups, there was no significant difference in the mRNFL, GCL+IPL, and GCC thicknesses among the amblyopic, fellow, and control eyes. In the anisometropic amblyopia group, choroidal thickness (subfovea, center 1 mm, nasal and inferior of the inner ring, nasal of the outer ring, and center 6 mm) of amblyopic eyes were significantly greater than that of fellow and normal eyes. In contrast, none of the choroidal thicknesses were significantly different among the investigated eyes in the strabismic amblyopia group. We found no significant difference in inner retinal thickness in patients with unilateral amblyopia. Although there were significant differences in choroidal thickness with hyperopic anisometropic amblyopia, there was no significant difference for the strabismic amblyopia. The discrepancy in choroidal thickness between the two types of amblyopia may be due to both differences in ocular size and underlying mechanism.

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.

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.

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.

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.

Prevalence of myelinated retinal nerve fibres in adult Indians: the Central India Eye and Medical Study.

PubMed

Nangia, Vinay; Jonas, Jost B; Khare, Anshu; Bhate, Karishma; Agarwal, Shubhra; Panda-Jonas, Songhomitra

2014-05-01

To determine the prevalence of myelinated retinal nerve fibers in the adult Indian population. The Central India Eye and Medical Study performed in rural Central India included 4711 participants aged 30+ years. The participants underwent a detailed ophthalmic and medical examination. Readable fundus photographs were available for 8645 eyes of 4485 (95.2%) subjects. Myelinated retinal nerve fibers were detected in 52 eyes (46 subjects) with a prevalence rate of 0.58±0.08 per 100 eyes [95% confidence interval (CI): 0.42, 0.74] and 1.03±0.15 per 100 subjects (95%CI: 0.73, 1.32). Prevalence of myelinated retinal nerve fibers was significantly associated hyperopic refractive error (p=0.008; OR: 1.31; 95%CI: 1.07, 1.59). It was not significantly associated with age (p=0.11), best corrected visual acuity (logMAR; p=0.33), intraocular pressure (p=0.09), amount of nuclear cataract (p=0.93), optic disc area (p=0.60), presence of glaucomatous optic nerve atrophy (p=0.62), and early age-related macular degeneration (p=0.53). Myelinated retinal nerve fibers are present in about 10 out of 1000 adult Indians in rural Central India, with a higher prevalence in hyperopic eyes. Prevalence of myelinated retinal nerve fibers was not associated with age, visual acuity, glaucoma and macular degeneration. © 2013 Acta Ophthalmologica Scandinavica Foundation. Published by John Wiley & Sons Ltd.

Cryopreservation of Extracted Corneal Lenticules after Small Incision Lenticule Extraction for Potential Use in Human Subjects

PubMed Central

Ganesh, Sri; Rao, Pallavi A.

2014-01-01

Purpose: To describe the technique of cryopreservation of corneal lenticules extracted after small incision refractive lenticule extraction (ReLEx SMILE) and initial results of femtosecond laser intrastromal lenticular implantation for hyperopia. Methods: Lenticules were collected from patients undergoing ReLEx SMILE for the correction of myopia and subjected to a tissue processing technique and cryopreservation. These lenticules were subsequently used to treat 8 hyperopic eyes and 1 aphakic eye. A femtosecond laser was used to create a pocket into each patient's cornea, followed by implantation of a cryopreserved lenticule. The patients were monitored through follow-up examinations for a mean 155.4 days (38–310 days). Results: The mean interval from storage of lenticules to removal from liquid nitrogen was 96 days (range, 19–178 days). Mean spherical equivalent of hyperopic eyes treated was +4.50 ± 1.1 diopter (D). Mean keratometry and pachymetry changed from preoperative 43.9 D and 531.6 μm to 47.4 D and 605.2 μm, respectively, postoperatively. Mean residual spherical equivalent for hyperopic eyes was +0.6 D and +4.1 D for the aphakic eye. None of the eyes showed evidence of rejection or loss of best-corrected visual acuity at the end of the follow-up period. Conclusions: The cryopreservation technique seems to be a safe method of long-term storage of refractive lenticules extracted after ReLEx SMILE for use in allogeneic human subjects. It may potentially be a safe and effective alternative to excimer laser ablation for hyperopia because of the low risks of regression, haze, flap-related complications, postoperative dry eye, and higher-order aberrations. Clinical Trial Registration—URL: http://www.clinicaltrials.gov. Unique identifier: CTRI/2014/01/004331. PMID:25343698

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

Phenotypic characterization of X-linked retinoschisis: Clinical, electroretinography, and optical coherence tomography variables

PubMed Central

Neriyanuri, Srividya; Dhandayuthapani, Sudha; Arunachalam, Jayamuruga Pandian; Raman, Rajiv

2016-01-01

Aims: To study the phenotypic characteristics of X-linked retinoschisis (XLRS) and report the clinical, electroretinogram (ERG), and optical coherence tomography (OCT) variables in Indian eyes. Design: A retrospective study. Materials and Methods: Medical records of 21 patients with retinoschisis who were genetically confirmed to have RS1 mutation were reviewed. The phenotype characterization included the age of onset, best-corrected visual acuity, refractive error, fundus findings, OCT, and ERG. Statistical Analysis Used: Data from both the eyes were used for analysis. A P < 0.05 was set as statistical significance. Data were not normally distributed (P < 0.05, Shapiro wilk); hence, nonparametric tests were used for statistical analysis. Results: All were males whose mean age of presentation was 9 years. Visual acuity was moderately impaired (median 0.6 logMAR, interquartile range: 0.47, 1) in these eyes with a hyperopic refractive error of median +1.75 Ds (interquartile range: +0.50 Ds, +4.25 Ds). About 54.7% of the eyes had both foveal and peripheral schisis, isolated foveal schisis was seen in 28.5% of the eyes, and schisis with retinal detachment was seen in 16.6% of the eyes. The inner nuclear layer was found to be commonly involved in the schisis, followed by outer nuclear and plexiform layers as evident on OCT. On ERG, a- and b-wave amplitudes were significantly reduced in eyes with foveal and peripheral schisis when compared to the eyes with only foveal schisis (P < 0.05). Conclusions: XLRS has phenotypic heterogeneity as evident on OCT, ERG, and clinical findings. PMID:27609164

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 influence of first near-spectacle reading correction on accommodation and its interaction with convergence.

PubMed

Vedamurthy, Indu; Harrison, Wendy W; Liu, Yue; Cox, Ian; Schor, Clifton M

2009-09-01

Accommodation and convergence can adapt to blur and disparity stimuli and to age-related changes in accommodative amplitude. Does this ability decline with age? The authors investigated short-term adaptation to first near-spectacle reading correction on the accommodative-stimulus response (ASR) function, accommodative amplitude (AA), AC/A, and CA/C ratios in a pre-presbyopic and an incipient presbyopic population and determined whether changes in these functions recovered after discontinuation of the use of near spectacles. Thirty subjects with normal vision participated; their ages ranged from 21 to 30 years (n = 15) and 38 to 44 years (n = 15). Oculomotor functions were measured before and after single-vision reading spectacles were worn for near tasks over a 2-month period and then 2 months after the use of near spectacles was discontinued. The slope of the ASR function and the AC/A and CA/C ratios did not change significantly after near spectacles were worn. There was a hyperopic shift of the ASR function that significantly reduced the near point of accommodation (NPA) and lowered the far-point refraction. These changes were age invariant and did not recover after 2 months of discontinuation of near spectacle wear. These results imply that the NPA may be enhanced normally by tonic bias of accommodation that elevates the entire ASR function and produces myopic refraction bias. When this bias relaxes after reading spectacles are worn, there is a hyperopic shift of the refractive state and a reduction of the NPA, specified from optical infinity.

The Influence of First Near-Spectacle Reading Correction on Accommodation and Its Interaction with Convergence

PubMed Central

Vedamurthy, Indu; Harrison, Wendy W.; Liu, Yue; Cox, Ian; Schor, Clifton M.

2010-01-01

PURPOSE Accommodation and convergence can adapt to blur and disparity stimuli and to age-related changes in accommodative amplitude. Does this ability decline with age? The authors investigated short-term adaptation to first near-spectacle reading correction on the accommodative-stimulus response (ASR) function, accommodative amplitude (AA), AC/A, and CA/C ratios in a pre-presbyopic and an incipient presbyopic population and determined whether changes in these functions recovered after discontinuation of the use of near spectacles. METHODS Thirty subjects with normal vision participated; their ages ranged from 21 to 30 years (n = 15) and 38 to 44 years (n = 15). Oculomotor functions were measured before and after single-vision reading spectacles were worn for near tasks over a 2-month period and then 2 months after the use of near spectacles was discontinued. RESULTS The slope of the ASR function and the AC/A and CA/C ratios did not change significantly after near spectacles were worn. There was a hyperopic shift of the ASR function that significantly reduced the near point of accommodation (NPA) and lowered the far-point refraction. These changes were age invariant and did not recover after 2 months of discontinuation of near spectacle wear. CONCLUSIONS These results imply that the NPA may be enhanced normally by tonic bias of accommodation that elevates the entire ASR function and produces myopic refraction bias. When this bias relaxes after reading spectacles are worn, there is a hyperopic shift of the refractive state and a reduction of the NPA, specified from optical infinity. PMID:19264892

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.

Combined hydrogel inlay and laser in situ keratomileusis to compensate for presbyopia in hyperopic patients: one-year safety and efficacy.

PubMed

Chayet, Arturo; Barragan Garza, Enrique

2013-11-01

To perform a feasibility study of the safety and efficacy of a corneal-contouring inlay with concurrent laser in situ keratomileusis (LASIK) to treat hyperopic presbyopia. Private clinic, Tijuana, Mexico. Prospective interventional case series. Hyperopic patients received LASIK in both eyes and a corneal inlay under the femtosecond laser flap in the nondominant eye. The inlay is designed to reshape the anterior corneal curvature, creating a near-center multifocal refractive effect. Main safety outcomes were retention of preoperative corrected distance and near visual acuities and reports of adverse events. Efficacy was determined through measurements of near, intermediate, and distance visual acuities and patient questionnaires on visual task ability and satisfaction. The study enrolled 16 patients. All eyes with an inlay achieved an uncorrected near visual acuity (UNVA) of 20/32 or better by the 1-week postoperative examination and at every visit thereafter. The mean monocular and binocular UNVA was 20/27 or better at all visits. The mean binocular uncorrected distance visual acuity improved significantly from 20/53 preoperatively to 20/19 postoperatively (P<10(-5)). One inlay was explanted during the study. At 1 year, all 14 patients analyzed were satisfied or very satisfied with their near, distance, and overall vision. The hydrogel corneal inlay with concurrent LASIK improved uncorrected near, intermediate, and distance visual acuity in hyperopic presbyopic patients with high patient satisfaction and visual task ability. This represents a new indication for this recently developed technology. Copyright © 2013 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.

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

Brief hyperopic defocus or form deprivation have varying effects on eye growth and ocular rhythms depending on the time-of-day of exposure.

PubMed

Nickla, Debora L; Jordan, Kelsey; Yang, Jane; Totonelly, Kristen

2017-08-01

It is generally accepted that myopic defocus is a more potent signal to the emmetropization system than hyperopic defocus: one hour per day of myopic defocus cancels out 11 h of hyperopic defocus. However, we have recently shown that the potency of brief episodes of myopic defocus at inhibiting eye growth depends on the time of day of exposure. We here ask if this will also be true of the responses to brief periods of hyperopic defocus: may integration of the signal depend on time of day? If so, are the rhythms in axial length and choroidal thickness altered? Hyperopic defocus: Birds had one eye exposed to hyperopic defocus by the wearing of -10D lenses for 2 or 6 h at one of 3 times of day for 5 days: Morning (7 am - 9 am: n = 13; 7 am - 1 pm: n = 6), Mid-day (12 pm - 2 pm: n = 20; 10 am - 4 pm: n = 8), or Evening (7 pm - 9 pm: n = 12; 2 pm - 8 pm: n = 11). A separate group wore monocular lenses continually as a control (n = 12). Form deprivation: Birds wore a diffuser over one eye for 2 h at one of 3 times of day for 5 days: Morning (n = 12); Mid-day (n = 19) or Evening (n = 6). For all groups, ocular dimensions were measured using high-frequency A-scan ultrasonography at noon on the first day, under inhalation anesthesia. On day 5, eye dimensions were re-measured at 12 pm, and refractive errors were measured using a Hartinger's refractometer. A subset of birds in the 2-h lens group (morning, n = 8; mid-day, n = 8; evening, n = 6), and the deprivation group (n = 6 per time point), were also measured at 6 pm, 12 am, 6 am and 12 pm on the last day of exposure, to obtain the parameters of the diurnal rhythms in axial length and choroidal thickness. The effects of 2 h of defocus depended on time of day of exposure: it stimulated eye growth when exposure was in the morning and inhibited it when it was at mid-day (change in vitreous chamber, X-C; ANOVA p < 0.0005; 120 μm vs -77 μm/5d, respectively; t-tests: p = 0.001; p = 0.01; post-hoc tests: p = 0.002). For mid-day, experimental eyes were more hyperopic (1.4 D; p < 0.0001). Similar to 2 h defocus, 6 h exposures at mid-day inhibited growth and produced hyperopia (X-C: -167 μm; t-test p = 0.005; RE: 1.8 D; p = 0.03). The effects of 2 h of FD were similar to those of hyperopic defocus in inhibiting growth for mid-day exposures, but FD inhibited growth for the morning exposures as well (Axial length: X-C: Morning: -122 μm; mid-day: -92 μm; ttests p = 0.006 and p = 0.016 respectively). Experimental eyes were more hyperopic (1.8 D; 1.0 D; p < 0.05). The rhythms in axial length were altered for the morning exposures in both conditions. Form deprivation in the morning, which caused inhibition, caused the phases of the two rhythms to shift toward one another (peaks at 6:00 am and 10:45 am for choroid and axial length respectively). Our findings imply that the retinal "integrator", and/or scleral growth regulator exhibit diurnal rhythms. Furthermore, they suggest that reading activities early in the day may be contraindicated in school children at risk of becoming myopic. Copyright © 2017 Elsevier Ltd. All rights reserved.

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.

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.

Topographic hot spot before descemet stripping automated endothelial keratoplasty is associated with postoperative hyperopic shift.

PubMed

Shimizu, Tsutomu; Yamaguchi, Takefumi; Satake, Yoshiyuki; Shimazaki, Jun

2015-03-01

The aim of this study was to investigate topographic "hot spots" on the anterior corneal surface before Descemet stripping automated endothelial keratoplasty (DSAEK) and their effects on postoperative visual acuity and hyperopic shift. Twenty-seven eyes of 27 patients with bullous keratopathy, who underwent DSAEK were studied. We defined a hot spot as a focal area with relatively high refractive power on the anterior corneal surface in eyes with bullous keratopathy. Refractive spherical equivalent, keratometric value, and corneal topography were retrospectively evaluated using anterior segment optical coherence tomography (AS-OCT). Hot spots were identified in 11 eyes (42.3%) before DSAEK and disappeared in 9 eyes of these eyes (81.8%) at 6 months after DSAEK. AS-OCT revealed focal epithelial thickening in the same areas as the hot spots. There was no significant difference in the postoperative visual acuity between eyes with and without hot spots (P > 0.05). The keratometric value of the anterior corneal surface significantly flattened from 45.7 ± 2.7 diopters (D) before DSAEK to 44.2 ± 2.7 D 1 month after DSAEK in eyes with hot spots (P = 0.01), whereas in eyes without hot spots, there were no significant differences in the keratometric values before and after DSAEK. At 6 months, the refractive change was +1.1 ± 1.3 D in eyes with hot spots and -0.2 ± 0.6 D in eyes without hot spots (P = 0.034). In eyes with focal epithelial thickening, topographic hot spots on the anterior corneal surface were observed using AS-OCT. The hot spots disappeared after DSAEK and had no influence on the postoperative visual acuity.

Inter-individual variability in the dynamics of natural accommodation in humans: relation to age and refractive errors.

PubMed Central

Schaeffel, F; Wilhelm, H; Zrenner, E

1993-01-01

1. To study the relationship between accommodation under natural viewing conditions, age and refractive errors, we have measured time courses of accommodation in thirty-nine human subjects aged 5-49 years using a newly developed technique. The technique is based on infrared photoretinoscopy and involves fully automated on-line image processing of digitized video images of the eyes with a sampling rate of 5.3 Hz. 2. The distance between the subject and the video camera was about 1.3 m. Head movements of the subject required little restriction because the eyes were automatically tracked in the video image by the computer program. All subjects were tested under binocular viewing conditions. 3. Both refraction of the right eye and pupil diameter were measured with a precision of 0.2-0.4 dioptres (D) and 0.1 mm, respectively, and were plotted on-line. The data were subsequently automatically analysed. 4. Automated infrared photoretinoscopy proved to be very convenient and easy to handle in both children and adults. 5. The maximal speed of accommodation for a target at a distance of 5 D declined in the subjects with age (from up to 21.7 D s-1 for accommodation and 32.7 D s-1 for subsequent accommodation to a distant target ('near to far accommodation') in children down to 2-18 D s-1 in adults). There was a striking inter-individual variability in the maximum possible speed of accommodation and near to far accommodation. 6. Speed of accommodation and of near to far accommodation was correlated for each subject. However, in most of the subjects, the process of near to far accommodation was faster than accommodation (P < 0.005, if averaged over all subjects). This correlation was independent of age. 7. The accommodation-induced pupillary constriction (pupillary near response) was absent in children for a 4 D target; even at 10 D, there was no reliable pupillary response. The pupillary near response increased to about 1.6 mm D-1 of accommodation at the age of 47. Since a pupillary near response could still be elicited in presbyopic subjects unable to accommodate, the ratio of pupillary constriction per dioptre of accommodation approached infinity. 8. The magnitude of the pupillary near response was highly variable even among subjects of the same age but was typical for each subject. There was a correlation (P < 0.01) to refractive error: corrected myopes had weaker pupillary near responses than emmetropes or hyperopes.(ABSTRACT TRUNCATED AT 400 WORDS) Images Fig. 2 Fig. 8 PMID:8350267

Implantation of a Multifocal Toric Intraocular Lens after Radial Keratotomy and Cross-Linking with Hyperopia and Astigmatism Residues: A Case Report.

PubMed

Nuzzi, Raffaele; Monteu, Francesca; Tridico, Federico

2017-01-01

Radial keratotomy is a refractive surgical technique, widely used in the 80s and early 90s to correct myopia and astigmatism, but now overcome by more recent laser techniques. Important consequences, often in patients with more than 45 years of age, are progressive hyperopic shift and/or an increase in corneal astigmatism, whose main cause seems to be an increase in the curvature radius of the central portion of the cornea. This seems to be due to radial keratotomy incisions - with the consequent need for cross-linking - intraocular pressure, and corneal biomechanical parameters. The authors propose phacoemulsification with a customized multifocal toric intraocular lens implantation to correct the induced shift and hyperopic astigmatism. A decent postoperative visual acuity was observed with good patient satisfaction. A specific protocol must be applied to optimize the correct diagnosis, presurgical evaluation and postsurgical outcomes that are to be maintained over time, without regressions.

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

Accommodation and age-dependent eye model based on in vivo measurements.

PubMed

Zapata-Díaz, Juan F; Radhakrishnan, Hema; Charman, W Neil; López-Gil, Norberto

2018-03-21

To develop a flexible model of the average eye that incorporates changes with age and accommodation in all optical parameters, including entrance pupil diameter, under photopic, natural, environmental conditions. We collated retrospective in vivo measurements of all optical parameters, including entrance pupil diameter. Ray-tracing was used to calculate the wavefront aberrations of the eye model as a function of age, stimulus vergence and pupil diameter. These aberrations were used to calculate objective refraction using paraxial curvature matching. This was also done for several stimulus positions to calculate the accommodation response/stimulus curve. The model predicts a hyperopic change in distance refraction as the eye ages (+0.22D every 10 years) between 20 and 65 years. The slope of the accommodation response/stimulus curve was 0.72 for a 25 years-old subject, with little change between 20 and 45 years. A trend to a more negative value of primary spherical aberration as the eye accommodates is predicted for all ages (20-50 years). When accommodation is relaxed, a slight increase in primary spherical aberration (0.008μm every 10 years) between 20 and 65 years is predicted, for an age-dependent entrance pupil diameter ranging between 3.58mm (20 years) and 3.05mm (65 years). Results match reasonably well with studies performed in real eyes, except that spherical aberration is systematically slightly negative as compared with the practical data. The proposed eye model is able to predict changes in objective refraction and accommodation response. It has the potential to be a useful design and testing tool for devices (e.g. intraocular lenses or contact lenses) designed to correct the eye's optical errors. Copyright © 2018 Spanish General Council of Optometry. Published by Elsevier España, S.L.U. All rights reserved.

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.

[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.

Space Flight-Induced Intracranial Hypertension: An Ophthalmic Review

NASA Technical Reports Server (NTRS)

Gibson, Charles Robert; Mader, Thomas H.

2010-01-01

Background: Although physiologic and pathologic changes associated with microgravity exposure have been studied extensively, the effect of this environment on the eye is largely unknown. Over the last several years, NASA s Space Medicine Division has documented astronauts presenting with varying degrees of disc edema, globe flattening, choroidal folds, cotton wool spots, and hyperopic shifts after long-duration space flight. Methods: Before and after long-duration space flight, six astronauts underwent complete eye examinations to include cycloplegic and/or manifest refraction and fundus photography. Five of these astronauts had Optical Coherence Tomography (OCT) and Magnetic Resonance Imaging (MRI) performed following their missions. Results: Following exposure to space flight of approximately 6-months duration, six astronauts had neuro-ophthalmic findings. These consisted of disc edema in four astronauts, globe flattening in four astronauts, choroidal folds in four astronauts, cotton wool spots in three astronauts, nerve fiber layer thickening by OCT in five astronauts, and decreased near vision in five astronauts. Four of the astronauts with near vision complaints had a hyperopic shift equal to or greater than + 0.50D between pre- and post-mission spherical equivalent refraction in one or both eyes (range +0.50D to +1.50D). These same four had globe flattening by MRI. Conclusions: The findings we describe may have resulted from a rise in intracranial pressure caused by microgravity fluid shifts, and could represent parts of a spectrum of ocular and cerebral responses to extended microgravity.

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.

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.

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.

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.

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.

[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.

The effect of simultaneous negative and positive defocus on eye growth and development of refractive state in marmosets.

PubMed

Benavente-Perez, Alexandra; Nour, Ann; Troilo, David

2012-09-21

We evaluated the effect of imposing negative and positive defocus simultaneously on the eye growth and refractive state of the common marmoset, a New World primate that compensates for either negative and positive defocus when they are imposed individually. Ten marmosets were reared with multizone contact lenses of alternating powers (-5 diopters [D]/+5 D), 50:50 ratio for average pupil of 2.80 mm over the right eye (experimental) and plano over the fellow eye (control) from 10 to 12 weeks. The effects on refraction (mean spherical equivalent [MSE]) and vitreous chamber depth (VC) were measured and compared to untreated, and -5 D and +5 D single vision contact lens-reared marmosets. Over the course of the treatment, pupil diameters ranged from 2.26 to 2.76 mm, leading to 1.5 times greater exposure to negative than positive power zones. Despite this, at different intervals during treatment, treated eyes were on average relatively more hyperopic and smaller than controls (experimental-control [exp-con] mean MSE ± SE +1.44 ± 0.45 D, mean VC ± SE -0.05 ± 0.02 mm) and the effects were similar to those in marmosets raised on +5 D single vision contact lenses (exp-con mean MSE ± SE +1.62 ± 0.44 D. mean VC ± SE -0.06 ± 0.03 mm). Six weeks into treatment, the interocular growth rates in multizone animals were already lower than in -5 D-treated animals (multizone -1.0 ± 0.1 μm/day, -5 D +2.1 ± 0.9 μm/day) and did not change significantly throughout treatment. Imposing hyperopic and myopic defocus simultaneously using concentric contact lenses resulted in relatively smaller and less myopic eyes, despite treated eyes being exposed to a greater percentage of negative defocus. Exposing the retina to combined dioptric powers with multifocal lenses that include positive defocus might be an effective treatment to control myopia development or progression.

The role of axial length-corneal radius of curvature ratio in refractive state categorization in a nigerian population.

PubMed

Iyamu, Eghosasere; Iyamu, Joy; Obiakor, Christian Izuchukwu

2011-01-01

The aim of this study was to investigate the association of axial length (AL)/corneal radius of curvature (CRC) ratio (AL/CRC) with spherical equivalent refractive state (SER) in young adults. A total of seventy (n = 70) subjects consisting of 31 males and 39 females participated in this study. Subjects were categorized into emmetropia, hyperopia and myopia using the spherical equivalent refraction. The axial length was measured with I-2100 A-Scan ultrasonography/Biometer (CIMA Technology, USA), the corneal radius of curvature with Bausch & Lomb H-135A (Bausch & Lomb Corp., USA), and the refractive state by static retinoscopy and subjective refraction. The mean AL, CRC and AL/CRC ratio of all subjects were 23.74 ± 0.70 mm, 7.84 ± 0.19 mm, and 3.03 ± 0.14, respectively. Myopes had significantly longer AL, steeper CRC and higher AL/CRC ratio than the emmetropes and hyperopes. There was statistically significant inverse correlation between AL and CRC (r = -0.53, P < 0.0001), SER (r = -0.64, P < 0.0001), and between SER and AL/CRC (r = -0.78, P < 0.0001). A significant positive correlation was found between CRC and SER (r = -0.69, P < 0.0001). The categorization of the refractive state of an individual is better done by using the AL/CRC ratio index.

Photorefractive keratectomy in the cat eye: biological and optical outcomes.

PubMed

Nagy, Lana J; MacRae, Scott; Yoon, Geunyoung; Wyble, Matthew; Wang, Jianhua; Cox, Ian; Huxlin, Krystel R

2007-06-01

To quantify optical and biomechanical properties of the feline cornea before and after photorefractive keratectomy (PRK) and assess the relative contribution of different biological factors to refractive outcome. Department of Ophthalmology, University of Rochester, Rochester, New York, USA. Adult cats had 6.0 diopter (D) myopic or 4.0 D hyperopic PRK over 6.0 or 8.0 mm optical zones (OZ). Preoperative and postoperative wavefront aberrations were measured, as were intraocular pressure (IOP), corneal hysteresis, the corneal resistance factor, axial length, corneal thickness, and radii of curvature. Finally, postmortem immunohistochemistry for vimentin and alpha-smooth muscle actin was performed. Photorefractive keratectomy changed ocular defocus, increased higher-order aberrations, and induced myofibroblast differentiation in cats. However, the intended defocus corrections were only achieved with 8.0 mm OZs. Long-term flattening of the epithelial and stromal surfaces was noted after myopic, but not after hyperopic, PRK. The IOP was unaltered by PRK; however, corneal hysteresis and the corneal resistance factor decreased. Over the ensuing 6 months, ocular aberrations and the IOP remained stable, while central corneal thickness, corneal hysteresis, and the corneal resistance factor increased toward normal levels. Cat corneas exhibited optical, histological, and biomechanical reactions to PRK that resembled those previously described in humans, especially when the OZ size was normalized to the total corneal area. However, cats exhibited significant stromal regeneration, causing a return to preoperative corneal thickness, corneal hysteresis and the corneal resistance factor without significant regression of optical changes induced by the surgery. Thus, the principal effects of laser refractive surgery on ocular wavefront aberrations can be achieved despite clear interspecies differences in corneal biology.

Photorefractive keratectomy in the cat eye: biological and optical outcomes

PubMed Central

Nagy, Lana J.; MacRae, Scott; Yoon, Geunyoung; Wyble, Matthew; Wang, Jianhua; Cox, Ian; Huxlin, Krystel R.

2007-01-01

PURPOSE To quantify optical and biomechanical properties of the feline cornea before and after photorefractive keratectomy (PRK) and assess the relative contribution of different biological factors to refractive outcome. SETTING Dept. Ophthalmology, University of Rochester, Rochester, New York, U.S.A. METHODS Adult cats underwent 6D myopic or 4D hyperopic PRK over 6 or 8mm optical zones (OZ). Pre- and post-operative wavefront aberrations were measured, along with intraocular pressure, corneal hysteresis (CH), corneal resistance factor (CRF), axial length, corneal thickness and radii of curvature. Finally, post-mortem imunohistochemistry for Vimentin and α-smooth muscle actin was performed. RESULTS PRK changed ocular defocus, increased higher order aberrations and induced myofibroblast differentiation in cats. However, the intended defocus corrections were only achieved with 8mm OZs. Long-term flattening of the epithelial and stromal surfaces was noted following myopic, but nor hyperopic PRKs. Feline intraocular pressure was unaltered by PRK, but CH and CRF decreased. Over the ensuing 6 months, ocular aberrations and intraocular pressure remained stable, while central corneal thickness, CH and CRF increased back towards normal levels. CONCLUSIONS Cat corneas exhibited optical, histological and biomechanical reactions to PRK that resembled those previously described in humans, especially when optical zone size was normalized to total corneal area. However, cats exhibited significant stromal regeneration, causing a return to pre-operative corneal thickness, CH and CRF without significant regression of optical changes induced by the surgery. Thus, the principal effects of laser refractive surgery on ocular wavefront aberrations can be achieved in spite of clear, inter-species differences in corneal biology. PMID:17531702

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.

Scleral gene expression during recovery from myopia compared with expression during myopia development in tree shrew.

PubMed

Guo, Lin; Frost, Michael R; Siegwart, John T; Norton, Thomas T

2014-01-01

During postnatal refractive development, the sclera receives retinally generated signals that regulate its biochemical properties. Hyperopic refractive error causes the retina to produce "GO" signals that, through the direct emmetropization pathway, cause scleral remodeling that increases the axial elongation rate of the eye, reducing the hyperopia. Myopia causes the retina to generate "STOP" signals that produce scleral remodeling, slowing the axial elongation rate and reducing the myopia. Our aim was to compare the pattern of gene expression produced in the sclera by the STOP signals with the GO gene expression signature we described previously. The GO gene expression signature was produced by monocular -5 diopter (D) lens wear for 2 days (ML-2) or 4 days (ML-4); an additional "STAY" condition was examined after eyes had fully compensated for a -5 D lens after 11 days of lens wear (ML-11). After 11 days of -5 D lens wear had produced full refractive compensation, gene expression in the STOP condition was examined during recovery (without the lens) for 2 days (REC-2) or 4 days (REC-4). The untreated contralateral eyes served as a control in all groups. Two age-matched normal groups provided a comparison with the treated groups. Quantitative real-time PCR was used to measure mRNA levels for 55 candidate genes. The STAY group compensated fully for the lens (treated eye versus control eye, -5.1±0.2 D). Wearing the lens, the hyperopic signal for elongation had dissipated (-0.3±0.3 D). In the STOP groups, the refraction in the recovering eyes became less myopic relative to the control eyes (REC-2, +1.3±0.3 D; REC-4, +2.6±0.4 D). In the STAY group, three genes showed significant downregulation. However, many genes that were significantly altered in GO showed smaller, nonsignificant, expression differences in the same direction in STAY, suggesting the gene expression signature in STAY is a greatly weakened form of the GO signature. In the STOP groups, a different gene expression pattern was observed, characterized by mostly upregulation with larger fold differences after 4 days than after 2 days of recovery. Eleven of the 55 genes examined showed significant bidirectional GO/STOP regulation in the ML-2 and REC-2 groups, and 13 genes showed bidirectional regulation in the ML-4 and REC-4 groups. Eight of these genes (NPR3, CAPNS1, NGEF, TGFB1, CTGF, NOV, TIMP1, and HS6ST1) were bidirectionally regulated at both time points in the GO and STOP conditions. An additional 15 genes showed significant regulation in either GO or STOP conditions but not in both. Many genes are involved in scleral remodeling and the control of axial length. The STOP (recovery) gene expression signature in the sclera involves some of the same genes, bidirectionally regulated, as the GO signature. However, other genes, regulated in GO, are not differentially regulated in STOP, and others show differential regulation only in STOP.

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.

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.

[Laser in situ keratomyleusis (LASIK) for correction of myopia and hypermetropia--our one year experience].

PubMed

Vukosavljević, Miroslav; Milivojević, Milorad; Resan, Mirko; Cerović, Vesna

2009-12-01

Laser in situ keratamileusis (LASIK) is the most commonly used refractive surgical method worldwide. The aim of this study was to examine the effectiveness and safety of LASIK in the correction of myopia and hyperopia. The study included myopic and hyperopic eyes with preoperative best corrected visual acuity (BCVA) = 1 (20/20), of the total number of 322 divided into 2 groups--1) myopic eyes (n = 241) which were divided into 4 subgroups according to the myopia strength: a) < or = -1.75 D (n = 23), b) from -2 to -3.75 D (n = 81), c) from -4 to -6.75 D (n = 113), d) > or = -7 D (n = 24); 2) hyperopic eyes (n = 81) which were divided into 3 subgroups according to the hyperopia strength: a) < or = +1.75D (n = 10), b) from +2 to +3.75 D (n = 46), c) > or = +4 D (n = 25). Myopic and hyperopic eyes with preoperative BCVA < or = 0.9 (eyes with ambliopia) were excluded from the study, as well as eyes with astigmatism > 1.5 D. To assess the effectiveness of LASIK we examined the percentage of eyes in the mentioned subgroups, which derived uncorrected visual acuity (UCVA) 6 month after the intervention to the following: a) UCVA = 1 (20/20) and b) UCVA > or = 0.5 (20/40). To assess the safety of LASIK we examined the frequency of intraoperative and postoperative complications. A prospective study was performed in a 6-months follow-up period. RESULTS. Refractive spherical equivalent (RSE) of myopic eyes was in the range from -0.75 D to -12 D. In the first subgroup preoperative mean value of RSE with standard deviation (mean RSE +/- SD) was -1.39 +/- 0.36 D, and 6 months after the LASIK 100% of the eyes had UCVA = 20/20. In the second subgroup preoperative mean RSE +/- SD was -2.85 +/- 0.50 D, and 6 months after LASIK 93% of the eyes had UCVA = 20/20, but 100% of the eyes had UCVA > or = 20/40. In the third subgroup preoperative mean RSE +/- SD was -5.03 +/- 0.75 D, and 6 months after the LASIK 90% of the eyes had UCVA = 20/20, but 100% of the eyes had UCVA > or = 20/40. In the fourth subgroup preoperative mean RSE +/- SD was -7.68 +/- 1.03 D, and 6 months after the LASIK 96% of the eyes had UCVA = 20/20, but 100% of eyes had UCVA > or = 20/40. Refractive spherical equivalent of hyperopic eyes was in the range from +1 D to +6 D. In the first subgroup preoperative mean RSE +/- SD was +1.50 +/- 0.30 D, and 6 months after the LASIK 90% of the eyes had UCVA = 20/20, but 100% of the eyes had UCVA > or = 20/40. In the second subgroup preoperative mean RSE +/- SD was +2.65 +/- 0.46 D, and 6 months after the LASIK 87% of the eyes had UCVA = 20/20, but 96% of the eyes had UCVA > or = 20/40. In the third subgroup preoperative mean RSE +/- SD was +4.62 +/- 0.68 D, and 6 months after the LASIK 64% of the eyes had UCVA = 20/20, but 100% of the eyes had UCVA > or = 20/40. In our study intraoperative complications appeared in 6 eyes (1.86%): thin flap in 2 eyes (0.62%) and epithelial defects in 4 eyes (1.24%), yet postoperative complications appeared in 10 eyes (3.10%): flap folds in 2 eyes (0.62%), epithelial ingrowth in 4 eyes (1.24%) and regression in 4 eyes (1.24%). LASIK is effective and safe refractive surgical method for correcting myopia up to -12 D and hyperopia up to +6 D.

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.

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.

Compensation for spectacle lenses involves changes in proteoglycan synthesis in both the sclera and choroid.

PubMed

Nickla, D L; Wildsoet, C; Wallman, J

1997-04-01

It has been demonstrated that chick eye growth compensates for defocus imposed by spectacle lenses: the eye elongates in response to hyperopic defocus imposed by negative lenses and slows its elongation in response to myopic defocus imposed by positive lenses. We ask whether the synthesis of scleral extracellular matrix, specifically glycosaminoglycans, changes in parallel with the changes in ocular elongation. In addition, there is a choroidal component to compensation for spectacle lenses; the choroid thickens in response to myopic defocus and thins in response to hyperopic defocus. We ask whether choroidal glycosaminoglycan synthesis changes in parallel with changes in choroidal thickness. Chicks wore either a +15 diopter (D) or -15 D spectacle lens over one eye, or they wore one lens of each power over each eye for 5 days. At the end of this period, we measured refractive errors and ocular dimensions by refractometry and A-scan ultrasonography, respectively. Pieces of the scleras and choroids from these eyes were put into culture and the synthesis of glycosaminoglycans was assessed by measuring the incorporation of radioactive inorganic sulfur. We here report that the compensatory modulation of the length of the eye involves changes in the synthesis of glycosaminoglycans in the sclera, with synthesis increasing in eyes wearing -15 D spectacles lenses and decreasing in eyes wearing +15 D lenses. In addition, changes in the synthesis of glycosaminoglycans in the choroid are correlated with changes in choroidal thickness: eyes wearing +15 D lenses develop thicker choroids and these choroids synthesize more glycosaminoglycans than choroids from eyes wearing -15 D lenses. Changes in scleral glycosaminoglycan synthesis accompany lens-induced changes in the length of the eye. Furthermore, changes in the thickness of the choroid are also associated with changes in the synthesis of glycosaminoglycans. These results are consistent with the regulation of the growth of the eye being bidirectional, and with the retina being able to sense the sign of defocus.

Refractive surgery for accommodative esotropia: 5-year follow-up.

PubMed

Magli, Adriano; Forte, Raimondo; Gallo, Flavio; Carelli, Roberta

2014-02-01

To assess the long-term effectiveness and safety of refractive surgery with LASIK or photorefractive keratectomy (PRK) for treating accommodative esotropia in adults. All patients with accommodative esotropia treated with LASIK or PRK until December 2007 and with a minimum follow-up of 5 years were retrospectively included. LASIK was performed on 44 eyes of 22 patients (12 women, 10 men; mean age: 22.7 ± 2.9 years). Mean postoperative follow-up was 62.1 ± 3.2 months. PRK was performed on 16 eyes of 8 patients (4 women, 4 men; mean age: 23.7 ± 1.7 years). Mean postoperative follow-up was 61.3 ± 2.8 months. At the 5-year follow-up, the mean cycloplegic refraction was more hyperopic in the PRK group (0.3 ± 0.8 vs 0.06 ± 0.3 diopters, P = .01). Correction of esotropia to esophoria or orthotropia was present in 21 patients (95.4%) treated with LASIK and in all patients treated with PRK. Both LASIK and PRK were effective in the long-term reduction of accommodative esotropia. Copyright 2014, SLACK Incorporated.

Bilateral acute angle closure glaucoma after hyperopic LASIK correction

PubMed Central

Osman, Essam A.; Alsaleh, Ahmed A.; Al Turki, Turki; AL Obeidan, Saleh A.

2009-01-01

Acute angle closure glaucoma is unexpected complication following laser in situ keratomileusis (LASIK). We are reporting a 49-years-old lady that was presented to the emergency department with acute glaucoma in both eyes soon after LASIK correction. Diagnosis was made on detailed clinical history and examination, slit lamp examination, intraocular pressure measurement and gonioscopy. Laser iridotomy in both eyes succeeded in controlling the attack and normalizing the intraocular pressure (IOP) more than 6 months of follow-up. Prophylactic laser iridotomy is essential for narrow angle patients before LASIK surgery if refractive laser surgery is indicated. PMID:23960863

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.

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

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

Subjective method of refractometry and depth of focus

PubMed Central

Sergienko, Nikolai M.; Gromova, Anastasia; Sergienko, Nikolai

2012-01-01

Purpose To study the impact of the depth of focus on subjective refraction and distribution of myopic and hyperopic refractions. Methods A total of 450 eyes of 305 subjects in the age range of 23–34 years were recruited for the study. A distribution of refractions was examined using a traditional method of the subjective refractometry on the basis of point-like posterior focus notion. Correction of the results was made on the assumption that the emmetropic eye retains high visual acuity when applying convex lenses with values which are fewer or equal to the depth of focus values. The following values of the depth of focus were used: ±0.55 D, ±0.35 D and ±0.2 D for visual acuity 1.0, 1.5 and 2.0, respectively. Results Application of the traditional method of refractometry produced the following occurrence of refractions: hypermetropia 59.3%, myopia 22% and emmetropia 18.7%. After correction of the initial results of values of the depth of focus the distribution of refractions was as follows: hypermetropia 12.7%, myopia 22% and emmetropia 65.3%. Conclusion The traditional method of subjective refractometry with application of trial lenses was developed on the basis of data of large optical aberrations and significant depth of focus which values should be taken into account during interpretation of results of subjective refractometry. Our data regarding to prevalence of emmetropic refraction falls in line with basic science provisions in respect of the physiology of the eye.

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.

Spectacle correction versus no spectacles for prevention of strabismus in hyperopic children

PubMed Central

Jones-Jordan, Lisa; Wang, Xue; Scherer, Roberta W; Mutti, Donald O

2014-01-01

Background Hyperopia (far-sightedness) in infancy requires accommodative effort to bring images into focus. Prolonged accommodative effort has been associated with an increased risk of strabismus (eye misalignment). Strabismus makes it difficult for the eyes to work together and may result in symptoms of asthenopia (eye strain) and intermittent diplopia (double vision), and makes near work tasks difficult to complete. Untreated strabismus may result in the development of amblyopia (lazy eye). The prescription of spectacles to correct hyperopic refractive error is believed to prevent the development of strabismus. Objectives To assess the effectiveness of prescription spectacles compared with no intervention for the prevention of strabismus in infants and children with hyperopia. Search methods We searched CENTRAL (which contains the Cochrane Eyes and Vision Group Trials Register) (2014, Issue 4), Ovid MEDLINE, Ovid MEDLINE In-Process and Other Non-Indexed Citations, Ovid MEDLINE Daily, Ovid OLDMEDLINE (January 1946 to April 2014), EMBASE (January 1980 to April 2014), PubMed (1966 to April 2014), the metaRegister of Controlled Trials (mRCT) (www.controlled-trials.com), ClinicalTrials.gov (www.clinicaltrials.gov) and the World Health Organization (WHO) International Clinical Trials Registry Platform (ICTRP) (www.who.int/ictrp/search/en). We did not use any date or language restrictions in the electronic searches for trials. We last searched the electronic databases on 3 April 2014. We also searched the Science Citation Index database in September 2013. Selection criteria We included randomized controlled trials and quasi-randomized trials investigating the assignment to spectacle intervention or no treatment for children with hyperopia. The definition of hyperopia remains subjective, but we required it to be at least greater than +2.00 diopters (D) of hyperopia. Data collection and analysis Two review authors independently extracted data using the standard methodologic procedures expected by The Cochrane Collaboration. One review author entered data into Review Manager and a second review author verified the data entered. The two review authors resolved discrepancies at all stages of the review process. Main results We identified three randomized controlled trials (855 children enrolled) in this review. These trials were all conducted in the UK with follow-up periods ranging from one to 3.5 years. We judged the included studies to be at high risk of bias, due to use of quasi-random methods for assigning children to treatment, no masking of outcomes assessors, and high proportions of drop-outs. None of the three trials accounted for missing data and analyses were limited to the available-case data (674 (79%) of 855 children enrolled for the primary outcome). These factors impair our ability to assess the effectiveness of treatment. Analyses incorporating the three trials we identified in this review (674 children) suggested the effect of spectacle correction initiated prior to the age of one year in hyperopic children between three and four years of age is uncertain with respect to preventing strabismus (risk ratio (RR) 0.71; 95% confidence interval (CI) 0.44 to 1.15). Based on a meta-analysis of three trials (664 children), the risk of having visual acuity worse than 20/30 at three years of age was also uncertain for children with spectacles compared with those without spectacle correction irrespective of compliance (RR 0.87; 95% CI 0.60 to 1.26). Emmetropization was reported in two trials: one trial suggested that spectacles impede emmetropization, and the second trial reported no difference in the rate of refractive error change. Authors’ conclusions Although children who were allocated to the spectacle group were less likely to develop strabismus and less likely to have visual acuity worse than 20/30 children allocated to no spectacles, these effects may have been chance findings, or due to bias. Due to the high risk of bias and poor reporting of included trials, the true effect of spectacle correction for hyperopia on strabismus is still uncertain. PMID:25133974

[Difference and distance between the central and thinnest points of the cornea: impact of refractive state, age and ocular side].

PubMed

Steinberg, J; Kohl, C; Katz, T; Richard, G; Linke, S J

2014-04-01

The aim of the study was to quantify the difference in corneal thickness between the central and thinnest points (∆PachyZ-PachyD), the distance between the center of the cornea and its thinnest point (vector length PachyD) and to explore the impact of refractive state, age and ocular side. This was a multicenter, retrospective, cross-sectional study and medical records of 16,872 eyes were reviewed. The Orbscan® (Bausch and Lomb) procedure was used for pachymetry and keratometry. The results showed that ∆PachyZ-PachyD and vector length PachyD were higher in hyperopic eyes (∆PachyZ-PachyD: 11.99 ± 12.08 µm, vector length PachyD: 0.85 ± 0.44 mm) compared to myopic eyes (∆PachyZ-PachyD: 9.2 ± 7.86 µm, vector length PachyD: 0.7 ± 0.37 mm; p < 0.001). Refractive state, age and ocular side demonstrated an independent, statistically significant impact on ∆PachyZ-PachyD and vector length PachyD. As a result of the significant impact of refractive state, age and ocular side on ∆PachyZ-PachyD and vector length PachyD, these variables should be considered in a normative data collection.

A case report of central toxic keratopathy in a patient post TransPRK (followed by corneal collagen cross-linking).

PubMed

Davey, Nicholas; Aslanides, Ioannis M; Selimis, Vasilis

2017-01-01

The purpose of this article is to report a case of central toxic keratopathy in a patient post transepithelial photorefractive keratectomy (TransPRK), followed immediately by corneal collagen cross-linking. This article describes the case of a 26-year-old male after bilateral aberration-free, TransPRK laser (Schwind Amaris 750S). The procedure was performed for compound myopic astigmatism in November 2015, followed immediately by accelerated corneal collagen cross-linking for early keratoconus. From day 3 post-op, tear film debris underneath both contact lenses with corneal haze and early, progressive central anterior stromal opacity formation only in the left eye were noted. At 2 weeks post-op, the left eye was noted to have a significant hyperopic shift with central corneal thinning in the anterior stroma. A central anterior stromal dense opacity had formed in the left eye with the surrounding superficial stromal haze. As of month 2, the opacity gradually started to improve in size and density. The hyperopic shift peaked at 2 months and continued to improve, largely due to epithelial compensation with a gradual recovery of stromal thickness. The question remains as to what provokes the typical central corneal necrosis/thinning in central toxic keratopathy. We hypothesize that the space between the contact lens and the corneal surface post TransPRK is prone to a "pseudo-interface pathology" that could mimic diffuse lamellar keratitis-like pathology. Suboptimal lid hygiene, resulting in tear film combinations of bacteria, inflammatory cells, matrix metalloproteinases and other proteolytic enzymes, contributes to the degradation of vulnerable, exposed collagen stromal tissue post TransPRK or any surface corneal ablation. Refractive surgeons should maintain a healthy lid margin and tear film, especially in contact lens wearers, to prevent potential complications in refractive surgery procedures.

High-hyperopia database, part I: clinical characterisation including morphometric (biometric) differentiation of posterior microphthalmos from nanophthalmos

PubMed Central

Relhan, N; Jalali, S; Pehre, N; Rao, H L; Manusani, U; Bodduluri, L

2016-01-01

Purpose To characterise and differentiate posterior microphthalmos (PM) and nanophthalmos (NO) using morphometric parameters. Patients and methods Consecutive case database of patients with hyperopia >+7.00 D sphere was analysed retrospectively for clinical and biometric characterisation. Thirty-eight consecutive high-hyperopic subjects (75 eyes) with axial lengths <20.5 mm underwent uniform comprehensive ocular evaluation. Twenty-five subjects were diagnosed as PM and 13 as NO based on the horizontal corneal diameter. Parameters analysed included visual acuity, refraction, horizontal corneal diameter, anterior chamber depth, lens thickness, axial length, fundus changes, and associated ocular pathology. Primary outcome measures: ocular biometry difference between PM and NO. Secondary outcome measures: differences in associated ocular pathologies between PM and NO. Results Hyperopia ranged from +7 to +17 D and was similar in the two groups. Lens thickness was statistically more in NO than in PM group (4.53±0.75 mm vs 3.82±0.48 mm, P <0.001), whereas anterior chamber depth was more in the PM than in NO group (3.26±0.36 mm, vs 2.59±0.37 mm, P<0.001). NO had higher association with angle-closure glaucoma (66.7% vs 0%) and pigmentary retinopathy (38.5 vs 8.0%) but lesser association with macular folds (0% vs 24%) as compared with PM. NO was associated with poorer visual acuity. Conclusion PM and NO have significant differences in lens thickness, anterior chamber depth, prevalence of glaucoma, pigmentary retinopathy, macular pathology, and visual acuity while being similar in hyperopic refraction. PMID:26493039

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.

Mesopic pupil size in a refractive surgery population (13,959 eyes).

PubMed

Linke, Stephan J; Baviera, Julio; Munzer, Gur; Fricke, Otto H; Richard, Gisbert; Katz, Toam

2012-08-01

To evaluate factors that may affect mesopic pupil size in refractive surgery candidates. Medical records of 13,959 eyes of 13,959 refractive surgery candidates were reviewed, and one eye per subject was selected randomly for statistical analysis. Detailed ophthalmological examination data were obtained from medical records. Preoperative measurements included uncorrected distance visual acuity, corrected distance visual acuity, manifest and cycloplegic refraction, topography, slit lamp examination, and funduscopy. Mesopic pupil size measurements were performed with Colvard pupillometer. Relationship between mesopic pupil size and age, gender, refractive state, average keratometry, and pachymetry (thinnest point) were analyzed by means of ANOVA (+ANCOVA) and multivariate regression analyses. Overall mesopic pupil size was 6.45 ± 0.82 mm, and mean age was 36.07 years. Mesopic pupil size was 5.96 ± 0.8 mm in hyperopic astigmatism, 6.36 ± 0.83 mm in high astigmatism, and 6.51 ± 0.8 mm in myopic astigmatism. The difference in mesopic pupil size between all refractive subgroups was statistically significant (p < 0.001). Age revealed the strongest correlation (r = -0.405, p < 0.001) with mesopic pupil size. Spherical equivalent showed a moderate correlation (r = -0.136), whereas keratometry (r = -0.064) and pachymetry (r = -0.057) had a weak correlation with mesopic pupil size. No statistically significant difference in mesopic pupil size was noted regarding gender and ocular side. The sum of all analyzed factors (age, refractive state, keratometry, and pachymetry) can only predict the expected pupil size in <20% (R = 0.179, p < 0.001). Our analysis confirmed that age and refractive state are determinative factors on mesopic pupil size. Average keratometry and minimal pachymetry exhibited a statistically significant, but clinically insignificant, impact on mesopic pupil size.

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.

[Changes of axial dimensions of the eye during growth in emmetropia, myopia and hyperopia].

PubMed

Katuzny, Bartłomiej J; Koszewska-Kołodziejczak, Aleksandra

2005-01-01

The aim ot this study was to evaluate changes ot axial dimensions ot the eye during growth in emmetropia, myopia and hyperopia. We examined 183 children (363 eyes) aged 4 to 19 with emmetropia, myopia and hyperopia. All measurements were performed after cycloplegia with 1% tropicamidum (Polfa Warszawa). Total and corneal refraction was examined with autokeratorefractometer (Nikon NRK-8000). Then we used ultrasound biometer Ocuscan (Alcon, USA), to measure axial length of the eye, axial length of the vitreous cavity, axial dimension of the lens and axial depth of the anterior chamber. 1. Growth of the axial length of the emmetropic eyes is finished at the age of 12, in hyperopic eyes in the age of 11 and in myopic eyes growth is proportional until the age of 14 and then significantly accelerates. 2. Growth of the axial length is mainly caused by increasing axial length of vitreous cavity. A little role in human eye growth is also played by increasing depth of the anterior chamber. 3. Between 4 and 19 years old, mean cycloplegic axial dimension of the lens is slightly decreasing in emmetropic and hyperopic eyes, whereas in myopic eyes is constant.

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

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.

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.

[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.

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 ...

Risk factors for refractive errors in primary school children (6-12 years old) in Nakhon Pathom Province.

PubMed

Yingyong, Penpimol

2010-11-01

Refractive error is one of the leading causes of visual impairment in children. An analysis of risk factors for refractive error is required to reduce and prevent this common eye disease. To identify the risk factors associated with refractive errors in primary school children (6-12 year old) in Nakhon Pathom province. A population-based cross-sectional analytic study was conducted between October 2008 and September 2009 in Nakhon Pathom. Refractive error, parental refractive status, and hours per week of near activities (studying, reading books, watching television, playing with video games, or working on the computer) were assessed in 377 children who participated in this study. The most common type of refractive error in primary school children was myopia. Myopic children were more likely to have parents with myopia. Children with myopia spend more time at near activities. The multivariate odds ratio (95% confidence interval)for two myopic parents was 6.37 (2.26-17.78) and for each diopter-hour per week of near work was 1.019 (1.005-1.033). Multivariate logistic regression models show no confounding effects between parental myopia and near work suggesting that each factor has an independent association with myopia. Statistical analysis by logistic regression revealed that family history of refractive error and hours of near-work were significantly associated with refractive error in primary school children.

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.

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.

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 of correctable visual impairment in primary school children in Qassim Province, Saudi Arabia.

PubMed

Aldebasi, Yousef H

2014-01-01

The worldwide prevalence of refractive errors (RE), which is a common cause of treatable visual impairment among children, varies widely. We assessed the prevalence of correctable visual impairment (uncorrected RE) in primary school children in Qassim, Saudi Arabia. A cross-sectional study was conducted in 21 primary schools. A total of 5176 children (mean age 9.5±1.8 years), 2573 boys (49.7%) and 2603 girls (50.3%), underwent a comprehensive eye examination. The examinations consisted of visual acuity, autorefraction, cover test, ocular motility, pupillary evaluation, anterior segment examination, cycloplegic auto-refraction and dilated fundus examination with direct ophthalmoscopy. The children were divided into groups based on their age and gender. The overall prevalence of RE in the better eye was 18.6% (n=963), and the prevalence of uncorrected RE 16.3% (n=846), with only 2.3% (n=127) of children wearing spectacles during examination. The prevalence of uncorrected myopia (5.8%) and myopic astigmatism (5.4%) was higher compared to that of hyperopic astigmatism (2.7%), mixed astigmatism (1.7%) and hyperopia (0.7%). The anisometropia prevalence was 3.6%. Risks for astigmatism, myopia and anisometropia were positively associated with age. In addition, myopia and anisometropia risks were also associated with female gender, while risk of astigmatism was correlated with male gender. Few children with vision reducing RE wore spectacles; an additional 16.3% of children could benefit from spectacle prescription. The prevalence of uncorrected RE in children is relatively high and represents an important public health problem in school-aged children in Qassim province. Performance of routine periodical vision screening throughout childhood may reverse this situation. Copyright © 2013 Spanish General Council of Optometry. Published by Elsevier Espana. All rights reserved.

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.

Familial Aggregation of Hyperopia in an Elderly Population of Siblings in Salisbury, Maryland

PubMed Central

Wojciechowski, Robert; Congdon, Nathan; Bowie, Heidi; Munoz, Beatriz; Gilbert, Donna; West, Sheila

2011-01-01

Purpose To determine whether hyperopia aggregates in families in an older mixed-race population. Design Cross-sectional familial aggregation study using sibships. Methods We recruited 759 subjects (mean age, 73.4 years) in 241 families through the population-based Salisbury Eye Evaluation study. Subjects underwent noncycloplegic refraction if best-corrected visual acuity (BCVA) was ≤20/40, had lensometry to measure their currently worn spectacles if BCVA was >20/40 with spectacles, or were considered to be plano (refraction of zero) if the BCVA was >20/40 without spectacles. Preoperative refraction from medical records was used for bilaterally pseudophakic subjects. Results Utilizing hyperopia cutoffs from 1.00 to 2.50 diopters, age-, race-, and gender-adjusted odds ratios for hyperopia with an affected sibling ranged from 2.72 (95% confidence interval [CI], 1.84–4.01) to 4.87 (95% CI, 2.54–9.30). The odds of hyperopia increased with age until 75 years, after which they remained relatively constant. Black men were significantly less likely to be hyperopic than white men, white women, or black women. Conclusions Hyperopia appears to be under strong genetic control in this older population. PMID:15629824

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.

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.

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.

Tietz/Waardenburg type 2A syndrome associated with posterior microphthalmos in two unrelated patients with novel MITF gene mutations.

PubMed

Cortés-González, Vianney; Zenteno, Juan Carlos; Guzmán-Sánchez, Martín; Giordano-Herrera, Verónica; Guadarrama-Vallejo, Dalia; Ruíz-Quintero, Narlly; Villanueva-Mendoza, Cristina

2016-12-01

Tietz syndrome and Waardenburg syndrome type 2A are allelic conditions caused by MITF mutations. Tietz syndrome is inherited in an autosomal dominant pattern and is characterized by congenital deafness and generalized skin, hair, and eye hypopigmentation, while Waardenburg syndrome type 2A typically includes variable degrees of sensorineural hearing loss and patches of de-pigmented skin, hair, and irides. In this paper, we report two unrelated families with MITF mutations. The first family showed an autosomal dominant pattern and variable expressivity. The second patient was isolated. MITF gene analysis in the first family demonstrated a c.648A>C heterozygous mutation in exon 8 c.648A>C; p. (R216S), while in the isolated patient, an apparently de novo heterozygous c.1183_1184insG truncating mutation was demonstrated in exon 10. All patients except one had bilateral reduced ocular anteroposterior axial length and a high hyperopic refractive error corresponding to posterior microphthalmos, features that have not been described as part of the disease. Our results suggest that posterior microphthalmos might be part of the clinical characteristics of Tietz/Waardenburg syndrome type 2A and expand both the clinical and molecular spectrum of the disease. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

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.

Can manipulation of orthokeratology lens parameters modify peripheral refraction?

PubMed

Kang, Pauline; Gifford, Paul; Swarbrick, Helen

2013-11-01

To investigate changes in peripheral refraction, corneal topography, and aberrations induced by changes in orthokeratology (OK) lens parameters in myopes. Subjects were fitted with standard OK lenses that were worn overnight for 2 weeks. Peripheral refraction, corneal topography, and corneal surface aberrations were measured at baseline and after 14 nights of OK lens wear. Subsequent to a 2-week washout period, subjects were refitted with another set of lenses where one eye was randomly assigned to wear an OK lens with a smaller optic zone diameter (OZD) and the other eye with a steeper peripheral tangent. Measurements were taken again at a second baseline and after 14 days of overnight wear of the second OK lens set. Standard OK lenses with a 6-mm OZD and 1/4 peripheral tangent caused significant changes in both peripheral refraction and corneal topography. Significant hyperopic shift occurred in the central visual field (VF) while a myopic shift was found at 35 degrees in the nasal VF. OK induced significant reductions in corneal power at all positions along the horizontal corneal chord except at 2.4 mm nasal where there was no significant change and at 2.8 mm nasal where there was an increase in corneal refractive power. A positive shift in spherical aberration was induced for all investigated lens designs except for the 1/2 tangent design when calculated over a 4-mm pupil. Reducing OZD and steepening the peripheral tangent did not cause significant changes in peripheral refraction or corneal topography profiles across the horizontal meridian. OK lenses caused significant changes in peripheral refraction, corneal topography, and corneal surface aberrations. Modifying OZD and peripheral tangent made no significant difference to the peripheral refraction or corneal topography profile. Attempting to customize refraction and topography changes through manipulation of OK lens parameters appears to be a difficult task.

[Peripheral refraction and retinal contour in congenital and acquired high myopia].

PubMed

Tarutta, E P; Markosyan, G A; Milash, S V

to perform a comparative study of peripheral refraction and retinal contour in patients with congenital versus acquired high myopia. A total of 30 patients (60 eyes) with high myopia aged 8 to 18 years (11.2±0.32 years on average) were examined. The patients were divided into 2 groups. Group 1 consisted of 21 patients (42 eyes) with acquired myopia of -6.0 to -10.25 diopters (-7.55±0.17 diopters on average), group 2 - of 9 patients (18 eyes) with congenital myopia of -8.75 to -28.75 diopters (-16.39±1.24 diopters on average). Using the Grand Seiko WR-5100K binocular open-field autoref/keratometer (Japan), relative peripheral refraction was assessed with account to relative peripheral eye length measured by the IOL Master partial coherent interferometer ('Carl Zeiss', Germany) at 15° and 30° nasally and temporally from the foveal center along the horizontal meridian. In acquired myopia, relative peripheral refraction and relative peripheral eye length readings evidenced the formation of peripheral hyperopic defocus in all examined zones. Congenital high myopia cases were notable for myopic defocus at 15° of the nasal retina (N15 zone): -0.67±0.33 diopters against the eye length change of -0.33±0.13 mm. The research helped identify retinal contour changes characteristic of congenital myopia and indicative of posterior pole irregularity.

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.

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

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

[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.

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.

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.

Anterior chamber depth studies.

PubMed

Hoffer, Kenneth J; Savini, Giacomo

2015-09-01

To compare the anterior chamber depth (ACD; corneal epithelium to lens) using 3 modalities and compare the change 1 day and 3 months postoperatively. Private practice, Santa Monica, California, USA. Nonrandomized prospective series. The mean optical pachymetry and immersion ultrasound (US) of the ACD and partial coherence interferometry (PCI) were measured. Optical pachymetry ACD was measured in 675 eyes postoperatively at 1 day and 3 months. The optical pachymetry ACD in 492 eyes was 3.17 mm ± 0.42 (SD); by immersion US, it was 2.99 ± 0.51 mm (0.18 mm deeper; P < .0001). In 178 eyes, the optical pachymetry ACD was 3.23 ± 0.45 mm; the PCI was 3.19 ± 0.48 mm (0.04 mm deeper), which was not statistically different (P > .05). In 675 eyes, optical pachymetry ACD preoperatively was 3.19 ± 0.40 mm. The postoperative 1-day optical pachymetry ACD was 4.35 ± 0.35 mm with a mean refractive error of -0.30 diopter (D); the final 3-month optical pachymetry ACD was 4.47 ± 0.31 mm, with a mean refractive error of -0.07 D (P < .0001). This is a mean intraocular lens (IOL) position shift of +0.12 mm posteriorly; the +0.23 D change represents a ratio of 1.92 D/mm of IOL axial movement. The PCI ACD was comparable with optical pachymetry, but careful immersion US led to a 0.18 mm shorter ACD reading that cannot be corrected by sound velocity. The posterior capsule contracted and moved the IOL posteriorly 0.12 mm, resulting in 0.23 D hyperopic shift. Dr. Hoffer owns the registered trademark name "Hoffer(®)" and receives royalties for its commercial use from Alcon Laboratories, Inc., Appasamy Associates, Carl Zeiss Meditec AG, DGH Technology, Inc., Ellex iScience, Inc., Haag-Streit AG, Nidek Co., Ltd., Tomey Corp., Topcon Medical Systems, Inc., and Ziemer USA, Inc., as well as royalties from Slack, Inc. for the textbook IOL Power. Neither 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.

PHOTOREFRACTIVE KERATECTOMY FOR ANISOMETROPIC AMBLYOPIA IN CHILDREN

PubMed Central

Paysse, Evelyn A

2004-01-01

ABSTRACT Purpose To assess the safety and efficacy of photorefractive keratectomy (PRK) in children with anisometropic amblyopia and to define the characteristics of children who may be candidates for PRK. Methods This thesis comprises four parts: (1) a retrospective analysis of risk factors predictive of amblyopia treatment failure in 104 children, (2) a prospective study of pachymetry in 198 eyes of 108 children, (3) development and implementation of a protocol to perform PRK under general anesthesia, and (4) a prospective interventional case-comparison study of PRK in 11 noncompliant children with anisometropic amblyopia to evaluate safety and long-term outcomes. Compliant and noncompliant children with anisometropic amblyopia were analyzed as controls. Results Factors associated with conventional anisometropic amblyopia treatment failure were poor compliance (P = .004), age 6 years or older (P = .01), astigmatism ≥1.5 diopters (P = .0002), and initial visual acuity of 20/200 or worse (P = .02). Central and paracentral pachymetry measurements were similar to published adult values. The general anesthesia protocol was efficient, and the laser functioned properly in all cases. All children did well with no anesthesia-related or treatment-related complications. Two years following PRK, the mean reduction in refractive error was 9.7 ± 2.6 diopters for myopes (P = .0001) and 3.4 ± 1.3 diopters for hyperopes (P = .001). The cycloplegic refractive error in 9 of 11 treated eyes was within 3 diopters of that in the fellow eye. Uncorrected visual acuity in the amblyopic eye improved by ≥2 lines in seven of nine children; best-corrected visual acuity improved by ≥2 lines in six of nine children. Stereopsis improved in five of nine children. The mean visual acuity of the PRK patients at last follow-up was significantly better than that of noncompliant controls (P = .003). The safety and efficacy indices for PRK in this study were 1.24 and 1.12, respectively. Conclusions Photorefractive keratectomy can be safely performed in children with anisometropic amblyopia. Visual acuity and stereopsis improved in most eyes, even in older children. Photorefractive keratectomy may have an important role in the management of anisometropic amblyopia in noncompliant children. PMID:15747767

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.

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 ...

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.

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 ...

Non-cycloplegic spherical equivalent refraction in adults: comparison of the double-pass system, retinoscopy, subjective refraction and a table-mounted autorefractor.

PubMed

Vilaseca, Meritxell; Arjona, Montserrat; Pujol, Jaume; Peris, Elvira; Martínez, Vanessa

2013-01-01

To evaluate the accuracy of spherical equivalent (SE) estimates of a double-pass system and to compare it with retinoscopy, subjective refraction and a table-mounted autorefractor. Non-cycloplegic refraction was performed on 125 eyes of 65 healthy adults (age 23.5±3.0 years) from October 2010 to January 2011 using retinoscopy, subjective refraction, autorefraction (Auto kerato-refractometer TOPCON KR-8100, Japan) and a double-pass system (Optical Quality Analysis System, OQAS, Visiometrics S.L., Spain). Nine consecutive measurements with the double-pass system were performed on a subgroup of 22 eyes to assess repeatability. To evaluate the trueness of the OQAS instrument, the SE laboratory bias between the double-pass system and the other techniques was calculated. The SE mean coefficient of repeatability obtained was 0.22D. Significant correlations could be established between the OQAS and the SE obtained with retinoscopy (r=0.956, P<0.001), subjective refraction (r=0.955, P<0.001) and autorefraction (r=0.957, P<0.001). The differences in SE between the double-pass system and the other techniques were significant (P<0.001), but lacked clinical relevance except for retinoscopy; Retinoscopy gave more hyperopic values than the double-pass system -0.51±0.50D as well as the subjective refraction -0.23±0.50D; More myopic values were achieved by means of autorefraction 0.24±0.49D. The double-pass system provides accurate and reliable estimates of the SE that can be used for clinical studies. This technique can determine the correct focus position to assess the ocular optical quality. However, it has a relatively small measuring range in comparison with autorefractors (-8.00 to +5.00D), and requires prior information on the refractive state of the patient.

Non-cycloplegic spherical equivalent refraction in adults: comparison of the double-pass system, retinoscopy, subjective refraction and a table-mounted autorefractor

PubMed Central

Vilaseca, Meritxell; Arjona, Montserrat; Pujol, Jaume; Peris, Elvira; Martínez, Vanessa

2013-01-01

AIM To evaluate the accuracy of spherical equivalent (SE) estimates of a double-pass system and to compare it with retinoscopy, subjective refraction and a table-mounted autorefractor. METHODS Non-cycloplegic refraction was performed on 125 eyes of 65 healthy adults (age 23.5±3.0 years) from October 2010 to January 2011 using retinoscopy, subjective refraction, autorefraction (Auto kerato-refractometer TOPCON KR-8100, Japan) and a double-pass system (Optical Quality Analysis System, OQAS, Visiometrics S.L., Spain). Nine consecutive measurements with the double-pass system were performed on a subgroup of 22 eyes to assess repeatability. To evaluate the trueness of the OQAS instrument, the SE laboratory bias between the double-pass system and the other techniques was calculated. RESULTS The SE mean coefficient of repeatability obtained was 0.22D. Significant correlations could be established between the OQAS and the SE obtained with retinoscopy (r=0.956, P<0.001), subjective refraction (r=0.955, P<0.001) and autorefraction (r=0.957, P<0.001). The differences in SE between the double-pass system and the other techniques were significant (P<0.001), but lacked clinical relevance except for retinoscopy; Retinoscopy gave more hyperopic values than the double-pass system -0.51±0.50D as well as the subjective refraction -0.23±0.50D; More myopic values were achieved by means of autorefraction 0.24±0.49D. CONCLUSION The double-pass system provides accurate and reliable estimates of the SE that can be used for clinical studies. This technique can determine the correct focus position to assess the ocular optical quality. However, it has a relatively small measuring range in comparison with autorefractors (-8.00 to +5.00D), and requires prior information on the refractive state of the patient. PMID:24195036

Refraction and visual acuity in a national Danish cohort of 4-year-old children of extremely preterm delivery.

PubMed

Fledelius, Hans C; Bangsgaard, Regitze; Slidsborg, Carina; laCour, Morten

2015-06-01

A recent threefold increase in laser treatment for advanced retinopathy of prematurity (ROP) triggered a nationwide preschool ophthalmic and developmental status among extremely preterm survivors. Here, we discuss refraction and visual acuity. Survivors (n = 178) from a national birth cohort (February 2004 to March 2006) of gestational age <28 weeks (PT) and 56 full-term (FT) controls attended for evaluation at age 4 years. Cycloplegic refraction and keratometry were achieved by Retinomax autokeratorefractor and visual acuities by symbol recognition (HOTV, logMAR). The refractive distribution presented a myopic tail (4.5%) and a hyperopic tail (11.9% ≥+2.5 D) as special preterm features, and corneas were more curved. Astigmatism and anisometropia were only marginally increased, and visual acuities were generally good. Best-corrected binocular median logMAR visual acuity was 0.1 in FT and 0.2 in PT, in Snellen equivalents 0.8 and 0.63. Snellen acuity ≤0.5 occurred across the ROP subgroups, but mainly in those with at least ROP stage 3. Two children had low vision. The overall fair outcome for refraction and function is in accordance with other recent northern Europe experience. The results differ in particular from the poorer ophthalmic outcomes reported in the pioneer US treatment studies (cryotherapy for ROP and ETROP). The diode laser ablations (n = 32) appeared effective in our series; except one child, all treated subjects had good or fair social vision at the age of 4 years. © 2015 Acta Ophthalmologica Scandinavica Foundation. Published by John Wiley & Sons Ltd.

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

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

Refractive eye surgery in treating functional amblyopia in children.

PubMed

Levenger, Samuel; Nemet, Pinhas; Hirsh, Ami; Kremer, Israel; Nemet, Arie

2006-01-01

While excimer laser refractive surgery is recommended and highly successful for correcting refractive errors in adults, its use in children has not been extensively exercised or studied. We report our experience treating children with amblyopia due to high anisometropia, high astigmatism, high myopia and with associated developmental delay. Review of patient records of our refractive clinic. A retrospective review was made of all 11 children with stable refractive errors who were unsuccessfully treated non-surgically and then underwent corneal refractive surgery and in one case, lenticular surgery. Seven had high myopic anisometropia, 2 had high astigmatism, and two had high myopia--one with Down's Syndrome and one with agenesis of the corpus callosum. The surgical refractive treatment eliminated or reduced the anisometropia, reduced the astigmatic error, improved vision and improved the daily function of the children with developmental delay. There were no complications or untoward results. Refractive surgery is safe and effective in treating children with high myopic anisometropia, high astigmatism, high myopia and developmental delay due to the resulting poor vision. Surgery can improve visual acuity in amblyopia not responding to routine treatment by correcting the refractive error and refractive aberrations.

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.

Body height and ocular dimensions in the adult population in rural Central India. The Central India Eye and Medical Study.

PubMed

Nangia, Vinay; Jonas, Jost B; Matin, Arshia; Kulkarni, Maithili; Sinha, Ajit; Gupta, Rajesh

2010-11-01

To investigate associations between anthropomorphic parameters and ocular dimensions in a typical rural society untouched by the effects of urbanization. The Central India Eye and Medical Study performed in rural Central India included 4,711 participants aged 30 or more years. The participants underwent a detailed ophthalmic and medical examination. After controlling for age, gender, level of education, and body mass index (BMI), taller subjects were more likely to have larger eyes with a longer axial length (+0.23 mm for each 10 cm increase in height), lower corneal refractive power (-0.50 diopters for each 10 cm increase in height), deeper anterior chambers (+0.03 mm for each 10 cm increase in height), and longer vitreous cavity (+0.20 mm for each 10 cm increase in height). Central corneal thickness (P = 0.97) and lens thickness (P = 0.08) were not significantly associated with body height. After controlling for age, gender, level of education and height, subjects with a higher BMI had shorter globes (-0.02 mm for each unit increase in BMI), flatter corneas (-0.03 diopters for each unit increase in BMI) and thicker corneas (+0.49 μm for each unit increase in BMI), thicker lenses and longer vitreous cavities. Body height as compared with the BMI had a stronger influence on the ocular biometric data. After correcting for age, gender, level of education and axial length, for each increase in body height by 10 cm or for each increase in BMI by one unit, the refractive error significantly increased by 0.23 diopters (P < 0.001) and by 0.40 diopters (P < 0.001) respectively. In the rural population of Central India without urbanization-associated myopization, body height and size of the eye were associated with each other: taller subjects had larger eyes with a flatter cornea. An increase in body height per 10 cm was associated with an increase in anterior chamber depth by 1% and an increase in vitreous cavity length by 1%. Subjects with a higher body mass index had shorter eyes, flatter and thicker corneas, and thicker lenses. Taller subjects and subjects with a higher BMI were more hyperopic. Since the occurrence of some ocular diseases depends on eye size and refractive error, the results may be helpful for screening examinations and for elucidating pathogenic associations.

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

Does Hofstetter's equation predict the real amplitude of accommodation in children?

PubMed

Hashemi, Hassan; Nabovati, Payam; Khabazkhoob, Mehdi; Yekta, Abbasali; Emamian, Mohammad Hassan; Fotouhi, Akbar

2018-01-01

The aim was to determine the distribution and associated factors of accommodative amplitude (AA) in six- to 12-year-old children and compare the results with those calculated using Hofstetter's formula. In a cross-sectional study in 2015, random sampling was done from urban and rural populations of Shahroud, northern Iran. Participating schoolchildren were examined for manifest, cycloplegic and subjective refraction, as well as uncorrected vision and visual acuity. The AA was measured with Donders' push-up method using a ruler. The near point of convergence (NPC) was also measured. Of the 6,624 selected children, 5,620 participated in the study and after applying the exclusion criteria, the final analyses were done on data from 5,444 schoolchildren. The mean age of the final sample was 9.24 ± 1.71 years (from six to 12 years) and 53.6 per cent (n = 2,919) were boys. Mean measured AA was 14.44 D (95 per cent confidence interval [CI]: 14.33-14.55). In all age groups, the mean measured AA was less than the predicted mean value calculated with the Hofstetter's equation. Mean measured AA was 14.44 D (95 per cent CI: 14.28-14.59) and 14.45 D (95 per cent CI: 14.29-14.6) in boys and girls, respectively (p = 0.926). AA significantly declined with age (coefficient: -0.18, 95 per cent CI: -0.23 to -0.12, p < 0.001). Mean AA in emmetropic, myopic and hyperopic children was 14.31 D, 17.30 D and 14.87 D, respectively. Older age (coefficient = -0.18), living in rural areas (coefficient = -0.48) and NPC (coefficient = 0.47) inversely related with AA and higher AA was associated with a shift of the spherical equivalent refraction toward myopia (coefficient = -0.41). The differences among groups with different types of refractive error and high AA in children with myopia are important findings of this study. The results of the present study suggest that Hofstetter's formula provides inaccurate AA estimates in children and thus, the interpretation of this index requires further population-based studies in different racial and ethnic groups. © 2017 Optometry Australia.

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.

A case report of central toxic keratopathy in a patient post TransPRK (followed by corneal collagen cross-linking)

PubMed Central

Davey, Nicholas; Aslanides, Ioannis M; Selimis, Vasilis

2017-01-01

Purpose The purpose of this article is to report a case of central toxic keratopathy in a patient post transepithelial photorefractive keratectomy (TransPRK), followed immediately by corneal collagen cross-linking. Methods This article describes the case of a 26-year-old male after bilateral aberration-free, TransPRK laser (Schwind Amaris 750S). The procedure was performed for compound myopic astigmatism in November 2015, followed immediately by accelerated corneal collagen cross-linking for early keratoconus. Results From day 3 post-op, tear film debris underneath both contact lenses with corneal haze and early, progressive central anterior stromal opacity formation only in the left eye were noted. At 2 weeks post-op, the left eye was noted to have a significant hyperopic shift with central corneal thinning in the anterior stroma. A central anterior stromal dense opacity had formed in the left eye with the surrounding superficial stromal haze. As of month 2, the opacity gradually started to improve in size and density. The hyperopic shift peaked at 2 months and continued to improve, largely due to epithelial compensation with a gradual recovery of stromal thickness. Conclusion The question remains as to what provokes the typical central corneal necrosis/thinning in central toxic keratopathy. We hypothesize that the space between the contact lens and the corneal surface post TransPRK is prone to a “pseudo-interface pathology” that could mimic diffuse lamellar keratitis-like pathology. Suboptimal lid hygiene, resulting in tear film combinations of bacteria, inflammatory cells, matrix metalloproteinases and other proteolytic enzymes, contributes to the degradation of vulnerable, exposed collagen stromal tissue post TransPRK or any surface corneal ablation. Refractive surgeons should maintain a healthy lid margin and tear film, especially in contact lens wearers, to prevent potential complications in refractive surgery procedures. PMID:28450791

Compact adaptive optic-optical coherence tomography system

DOEpatents

Olivier, Scot S [Livermore, CA; Chen, Diana C [Fremont, CA; Jones, Steven M [Danville, CA; McNary, Sean M [Stockton, CA

2012-02-28

Badal Optometer and rotating cylinders are inserted in the AO-OCT to correct large spectacle aberrations such as myopia, hyperopic and astigmatism for ease of clinical use and reduction. Spherical mirrors in the sets of the telescope are rotated orthogonally to reduce aberrations and beam displacement caused by the scanners. This produces greatly reduced AO registration errors and improved AO performance to enable high order aberration correction in a patient eyes.

Compact adaptive optic-optical coherence tomography system

DOEpatents

Olivier, Scot S [Livermore, CA; Chen, Diana C [Fremont, CA; Jones, Steven M [Danville, CA; McNary, Sean M [Stockton, CA

2011-05-17

Badal Optometer and rotating cylinders are inserted in the AO-OCT to correct large spectacle aberrations such as myopia, hyperopic and astigmatism for ease of clinical use and reduction. Spherical mirrors in the sets of the telescope are rotated orthogonally to reduce aberrations and beam displacement caused by the scanners. This produces greatly reduced AO registration errors and improved AO performance to enable high order aberration correction in a patient eyes.

Refraction-compensated motion tracking of unrestrained small animals in positron emission tomography.

PubMed

Kyme, Andre; Meikle, Steven; Baldock, Clive; Fulton, Roger

2012-08-01

Motion-compensated radiotracer imaging of fully conscious rodents represents an important paradigm shift for preclinical investigations. In such studies, if motion tracking is performed through a transparent enclosure containing the awake animal, light refraction at the interface will introduce errors in stereo pose estimation. We have performed a thorough investigation of how this impacts the accuracy of pose estimates and the resulting motion correction, and developed an efficient method to predict and correct for refraction-based error. The refraction model underlying this study was validated using a state-of-the-art motion tracking system. Refraction-based error was shown to be dependent on tracking marker size, working distance, and interface thickness and tilt. Correcting for refraction error improved the spatial resolution and quantitative accuracy of motion-corrected positron emission tomography images. Since the methods are general, they may also be useful in other contexts where data are corrupted by refraction effects. Crown Copyright © 2012. Published by Elsevier B.V. All rights reserved.

Refractive errors.

PubMed

Schiefer, Ulrich; Kraus, Christina; Baumbach, Peter; Ungewiß, Judith; Michels, Ralf

2016-10-14

All over the world, refractive errors are among the most frequently occuring treatable distur - bances of visual function. Ametropias have a prevalence of nearly 70% among adults in Germany and are thus of great epidemiologic and socio-economic relevance. In the light of their own clinical experience, the authors review pertinent articles retrieved by a selective literature search employing the terms "ametropia, "anisometropia," "refraction," "visual acuity," and epidemiology." In 2011, only 31% of persons over age 16 in Germany did not use any kind of visual aid; 63.4% wore eyeglasses and 5.3% wore contact lenses. Refractive errors were the most common reason for consulting an ophthalmologist, accounting for 21.1% of all outpatient visits. A pinhole aperture (stenopeic slit) is a suitable instrument for the basic diagnostic evaluation of impaired visual function due to optical factors. Spherical refractive errors (myopia and hyperopia), cylindrical refractive errors (astigmatism), unequal refractive errors in the two eyes (anisometropia), and the typical optical disturbance of old age (presbyopia) cause specific functional limitations and can be detected by a physician who does not need to be an ophthalmologist. Simple functional tests can be used in everyday clinical practice to determine quickly, easily, and safely whether the patient is suffering from a benign and easily correctable type of visual impairment, or whether there are other, more serious underlying causes.

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.

Surgical Options for the Refractive Correction of Keratoconus: Myth or Reality

PubMed Central

Zaldivar, R.; Aiello, F.; Madrid-Costa, D.

2017-01-01

Keratoconus provides a decrease of quality of life to the patients who suffer from it. The treatment used as well as the method to correct the refractive error of these patients may influence on the impact of the disease on their quality of life. The purpose of this review is to describe the evidence about the conservative surgical treatment for keratoconus aiming to therapeutic and refractive effect. The visual rehabilitation for keratoconic corneas requires addressing three concerns: halting the ectatic process, improving corneal shape, and minimizing the residual refractive error. Cross-linking can halt the disease progression, intrastromal corneal ring segments can improve the corneal shape and hence the visual quality and reduce the refractive error, PRK can correct mild-moderate refractive error, and intraocular lenses can correct from low to high refractive error associated with keratoconus. Any of these surgical options can be performed alone or combined with the other techniques depending on what the case requires. Although it could be considered that the surgical option for the refracto-therapeutic treatment of the keratoconus is a reality, controlled, randomized studies with larger cohorts and longer follow-up periods are needed to determine which refractive procedure and/or sequence are most suitable for each case. PMID:29403662

Prevalence of refractive errors in the European adult population: the Gutenberg Health Study (GHS).

PubMed

Wolfram, Christian; Höhn, René; Kottler, Ulrike; Wild, Philipp; Blettner, Maria; Bühren, Jens; Pfeiffer, Norbert; Mirshahi, Alireza

2014-07-01

To study the distribution of refractive errors among adults of European descent. Population-based eye study in Germany with 15010 participants aged 35-74 years. The study participants underwent a detailed ophthalmic examination according to a standardised protocol. Refractive error was determined by an automatic refraction device (Humphrey HARK 599) without cycloplegia. Definitions for the analysis were myopia <-0.5 dioptres (D), hyperopia >+0.5 D, astigmatism >0.5 cylinder D and anisometropia >1.0 D difference in the spherical equivalent between the eyes. Exclusion criterion was previous cataract or refractive surgery. 13959 subjects were eligible. Refractive errors ranged from -21.5 to +13.88 D. Myopia was present in 35.1% of this study sample, hyperopia in 31.8%, astigmatism in 32.3% and anisometropia in 13.5%. The prevalence of myopia decreased, while the prevalence of hyperopia, astigmatism and anisometropia increased with age. 3.5% of the study sample had no refractive correction for their ametropia. Refractive errors affect the majority of the population. The Gutenberg Health Study sample contains more myopes than other study cohorts in adult populations. Our findings do not support the hypothesis of a generally lower prevalence of myopia among adults in Europe as compared with East Asia.

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

[New possibilities screening of refractive errors among children].

PubMed

Ondrejková, M; Kyselová, P

2013-06-01

To establish early detection of refractive errors among children in Slovakia. Different screening methods have been evaluated and compared in this work. we have been working on a prospective study. Pre-school children in kindergardens in Central Slovakia were checked up between years 2009-2011. Effectiveness of various screening methods was compared within 2 groups, using test-type and Plusoptix Vision Screener. Parentęs of children positive to refractive errors were recommended to consult a paediatrician ophthalmologist. 3982 children were examined. As a result, 13-14.1% of children who have not been examinated by the specialist, were positive. 53.3% of them went to see the doctor afterwards. establishment of early refractive errors screening is an important method how to prevent strabismus and amblyopia. It is very important to improve parentęs knowledge about the risk of refractive errors and also to improve screening methods with collaboration with kindergarten teachers.

Atmospheric microwave refractivity and refraction

NASA Technical Reports Server (NTRS)

Yu, E.; Hodge, D. B.

1980-01-01

The atmospheric refractivity can be expressed as a function of temperature, pressure, water vapor content, and operating frequency. Based on twenty-year meteorological data, statistics of the atmospheric refractivity were obtained. These statistics were used to estimate the variation of dispersion, attenuation, and refraction effects on microwave and millimeter wave signals propagating along atmospheric paths. Bending angle, elevation angle error, and range error were also developed for an exponentially tapered, spherical atmosphere.

Visual Function of Moderately Hyperopic 4- and 5-Year-Old Children in the Vision In Preschoolers - Hyperopia In Preschoolers Study

PubMed Central

Ciner, Elise B.; Kulp, Marjean Taylor; Maguire, Maureen; Pistilli, Maxwell; Candy, T. Rowan; Moore, Bruce; Ying, Gui-shuang; Quinn, Graham; Orlansky, Gale; Cyert, Lynn

2016-01-01

Purpose To compare visual performance between emmetropic and uncorrected moderately hyperopic preschool age children without strabismus or amblyopia. Design Cross-sectional study. Methods Setting Multicenter, institutional. Patient or Study Population Children aged 4 or 5 years. Intervention or Observation Procedures Visual functions were classified as normal or reduced for each child based on the 95% confidence interval for emmetropes. Hyperopic (≥3.0 diopters [D] to ≤6.0D in the most hyperopic meridian; astigmatism≤1.50D; anisometropia≤1.0D) and emmetropic status were determined by cycloplegic autorefraction. Main Outcome Measures Uncorrected monocular distance and binocular near visual acuity (VA); accommodative response; and near random dot stereoacuity. Results Mean (±SD) LogMAR distance VA among 248 emmetropes was better than among 244 hyperopes for the better (0.05±0.10 vs. 0.14±0.11, p<.001) and worse eyes (0.10±0.11 vs. 0.19±0.10, p<.001). Mean binocular LogMAR near VA was better in emmetropes than hyperopes (0.13±0.11 vs. 0.21±0.11, p<.001). Mean accommodative response for emmetropes was lower than for hyperopes for both Monocular Estimation Method (1.03±0.51D vs. 2.03±1.03D, p<0.001) and Grand Seiko (0.46±0.45D vs. 0.99±1.0D, p<0.001). Median near stereoacuity was better in emmetropes than hyperopes (40 sec arc vs.120 sec arc, p<0.001). The average number of reduced visual functions was lower in emmetropic than in hyperopic children (.19 vs.1.0 p<0.001). Conclusions VA, accommodative response, and stereoacuity were significantly reduced in moderate uncorrected hyperopic preschool children compared to emmetropes. Higher hyperopes (≥4 to ≤6D) were at greatest risk, although more than half of children with lower magnitudes (≥3 to <4D) demonstrated one or more reductions in function. PMID:27477769

Prevalence of refractive error in Europe: the European Eye Epidemiology (E(3)) Consortium.

PubMed

Williams, Katie M; Verhoeven, Virginie J M; Cumberland, Phillippa; Bertelsen, Geir; Wolfram, Christian; Buitendijk, Gabriëlle H S; Hofman, Albert; van Duijn, Cornelia M; Vingerling, Johannes R; Kuijpers, Robert W A M; Höhn, René; Mirshahi, Alireza; Khawaja, Anthony P; Luben, Robert N; Erke, Maja Gran; von Hanno, Therese; Mahroo, Omar; Hogg, Ruth; Gieger, Christian; Cougnard-Grégoire, Audrey; Anastasopoulos, Eleftherios; Bron, Alain; Dartigues, Jean-François; Korobelnik, Jean-François; Creuzot-Garcher, Catherine; Topouzis, Fotis; Delcourt, Cécile; Rahi, Jugnoo; Meitinger, Thomas; Fletcher, Astrid; Foster, Paul J; Pfeiffer, Norbert; Klaver, Caroline C W; Hammond, Christopher J

2015-04-01

To estimate the prevalence of refractive error in adults across Europe. Refractive data (mean spherical equivalent) collected between 1990 and 2013 from fifteen population-based cohort and cross-sectional studies of the European Eye Epidemiology (E(3)) Consortium were combined in a random effects meta-analysis stratified by 5-year age intervals and gender. Participants were excluded if they were identified as having had cataract surgery, retinal detachment, refractive surgery or other factors that might influence refraction. Estimates of refractive error prevalence were obtained including the following classifications: myopia ≤-0.75 diopters (D), high myopia ≤-6D, hyperopia ≥1D and astigmatism ≥1D. Meta-analysis of refractive error was performed for 61,946 individuals from fifteen studies with median age ranging from 44 to 81 and minimal ethnic variation (98 % European ancestry). The age-standardised prevalences (using the 2010 European Standard Population, limited to those ≥25 and <90 years old) were: myopia 30.6 % [95 % confidence interval (CI) 30.4-30.9], high myopia 2.7 % (95 % CI 2.69-2.73), hyperopia 25.2 % (95 % CI 25.0-25.4) and astigmatism 23.9 % (95 % CI 23.7-24.1). Age-specific estimates revealed a high prevalence of myopia in younger participants [47.2 % (CI 41.8-52.5) in 25-29 years-olds]. Refractive error affects just over a half of European adults. The greatest burden of refractive error is due to myopia, with high prevalence rates in young adults. Using the 2010 European population estimates, we estimate there are 227.2 million people with myopia across Europe.

Refractive errors among patients attending the ophthalmology department of a medical college in North-East India

PubMed Central

Natung, Tanie; Taye, Trishna; Lyngdoh, Laura Amanda; Dkhar, Begonia; Hajong, Ranendra

2017-01-01

Purpose: To determine the magnitude and pattern of refractive errors among patients attending the ophthalmology department of a new medical college in North-East India. Materials and Methods: A prospective study of the new patients (age ≥5 years), who were phakic and whose unaided visual acuities were worse than 20/20 but improved with pinhole, was done. Complete ophthalmic examination and refraction with appropriate cycloplegia for age were done for the 4582 eligible patients. Spherical equivalents (SE) of refractive errors of the right eyes were used for analysis. Results: Of the 4582 eligible patients, 2546 patients had refractive errors (55.56%). The proportion of emmetropia (SE − 0.50–+0.50 diopter sphere [DS]), myopia (SE <−0.50 DS), high myopia (SE >−5.0 DS), and hypermetropia (>+0.50 DS for adults and >+2.0 DS for children) were 53.1%, 27.4%, 2.6%, and 16.9%, respectively. The proportion of hyperopia increased till 59 years and then decreased with age (P = 0.000). The proportion of myopia and high myopia decreased significantly with age after 39 years (P = 0.000 and P = 0.004, respectively). Of the 1510 patients with astigmatism, 17% had with-the-rule (WTR), 23.4% had against-the-rule (ATR), and 19% had oblique astigmatisms. The proportion of WTR and ATR astigmatisms significantly decreased (P = 0.000) and increased (P = 0.000) with age, respectively. Conclusions: This study has provided the magnitude and pattern of refractive errors in the study population. It will serve as the initial step for conducting community-based studies on the prevalence of refractive errors in this part of the country since such data are lacking from this region. Moreover, this study will help the primary care physicians to have an overview of the magnitude and pattern of refractive errors presenting to a health-care center as refractive error is an established and significant public health problem worldwide. PMID:29417005

Refractive errors among patients attending the ophthalmology department of a medical college in North-East India.

PubMed

Natung, Tanie; Taye, Trishna; Lyngdoh, Laura Amanda; Dkhar, Begonia; Hajong, Ranendra

2017-01-01

To determine the magnitude and pattern of refractive errors among patients attending the ophthalmology department of a new medical college in North-East India. A prospective study of the new patients (age ≥5 years), who were phakic and whose unaided visual acuities were worse than 20/20 but improved with pinhole, was done. Complete ophthalmic examination and refraction with appropriate cycloplegia for age were done for the 4582 eligible patients. Spherical equivalents (SE) of refractive errors of the right eyes were used for analysis. Of the 4582 eligible patients, 2546 patients had refractive errors (55.56%). The proportion of emmetropia (SE - 0.50-+0.50 diopter sphere [DS]), myopia (SE <-0.50 DS), high myopia (SE >-5.0 DS), and hypermetropia (>+0.50 DS for adults and >+2.0 DS for children) were 53.1%, 27.4%, 2.6%, and 16.9%, respectively. The proportion of hyperopia increased till 59 years and then decreased with age ( P = 0.000). The proportion of myopia and high myopia decreased significantly with age after 39 years ( P = 0.000 and P = 0.004, respectively). Of the 1510 patients with astigmatism, 17% had with-the-rule (WTR), 23.4% had against-the-rule (ATR), and 19% had oblique astigmatisms. The proportion of WTR and ATR astigmatisms significantly decreased ( P = 0.000) and increased ( P = 0.000) with age, respectively. This study has provided the magnitude and pattern of refractive errors in the study population. It will serve as the initial step for conducting community-based studies on the prevalence of refractive errors in this part of the country since such data are lacking from this region. Moreover, this study will help the primary care physicians to have an overview of the magnitude and pattern of refractive errors presenting to a health-care center as refractive error is an established and significant public health problem worldwide.

Profile of refractive errors in European Caucasian children with Autistic Spectrum Disorder; increased prevalence and magnitude of astigmatism.

PubMed

Anketell, Pamela M; Saunders, Kathryn J; Gallagher, Stephen; Bailey, Clare; Little, Julie-Anne

2016-07-01

Autistic Spectrum Disorder (ASD) is a common neurodevelopmental disorder characterised by impairment of communication, social interaction and repetitive behaviours. Only a small number of studies have investigated fundamental clinical measures of vision including refractive error. The aim of this study was to describe the refractive profile of a population of children with ASD compared to typically developing (TD) children. Refractive error was assessed using the Shin-Nippon NVision-K 5001 open-field autorefractor following the instillation of cyclopentolate hydrochloride 1% eye drops. A total of 128 participants with ASD (mean age 10.9 ± 3.3 years) and 206 typically developing participants (11.5 ± 3.1 years) were recruited. There was no significant difference in median refractive error, either by spherical equivalent or most ametropic meridian between the ASD and TD groups (Spherical equivalent, Mann-Whitney U307 = 1.15, p = 0.25; Most Ametropic Meridian, U305 = 0.52, p = 0.60). Median refractive astigmatism was -0.50DC (range 0.00 to -3.50DC) for the ASD group and -0.50DC (Range 0.00 to -2.25DC) for the TD group. Magnitude and prevalence of refractive astigmatism (defined as astigmatism ≥1.00DC) was significantly greater in the ASD group compared to the typically developing group (ASD 26%, TD 8%, magnitude U305 = 3.86, p = 0.0001; prevalence (χ12=17.71 , p < 0.0001). This is the first study to describe the refractive profile of a population of European Caucasian children with ASD compared to a TD population of children. Unlike other neurodevelopmental conditions, there was no increased prevalence of spherical refractive errors in ASD but astigmatic errors were significantly greater in magnitude and prevalence. This highlights the need to examine refractive errors in this population. © 2016 The Authors Ophthalmic & Physiological Optics © 2016 The College of Optometrists.

Retrospective analysis of refractive errors in children with vision impairment.

PubMed

Du, Jojo W; Schmid, Katrina L; Bevan, Jennifer D; Frater, Karen M; Ollett, Rhondelle; Hein, Bronwyn

2005-09-01

Emmetropization is the reduction in neonatal refractive errors that occurs after birth. Ocular disease may affect this process. We aimed to determine the relative frequency of ocular conditions causing vision impairment in the pediatric population and characterize the refractive anomalies present. We also compared the causes of vision impairment in children today to those between 1974 and 1981. Causes of vision impairment and refractive data of 872 children attending a pediatric low-vision clinic from 1985 to 2002 were retrospectively collated. As a result of associated impairments, refractive data were not available for 59 children. An analysis was made of the causes of vision impairment, the distribution of refractive errors in children with vision impairment, and the average type of refractive error for the most commonly seen conditions. We found that cortical or cerebral vision impairment (CVI) was the most common condition causing vision impairment, accounting for 27.6% of cases. This was followed by albinism (10.6%), retinopathy of prematurity (ROP; 7.0%), optic atrophy (6.2%), and optic nerve hypoplasia (5.3%). Vision impairment was associated with ametropia; fewer than 25% of the children had refractive errors < or = +/-1 D. The refractive error frequency plots (for 0 to 2-, 6 to 8-, and 12 to 14-year age bands) had a Gaussian distribution indicating that the emmetropization process was abnormal. The mean spherical equivalent refractive error of the children (n = 813) was +0.78 +/- 6.00 D with 0.94 +/- 1.24 D of astigmatism and 0.92 +/- 2.15 D of anisometropia. Most conditions causing vision impairment such as albinism were associated with low amounts of hyperopia. Moderate myopia was observed in children with ROP. The relative frequency of ocular conditions causing vision impairment in children has changed since the 1970s. Children with vision impairment often have an associated ametropia suggesting that the emmetropization system is also impaired.

Hyperopia and emergent literacy of young children: pilot study.

PubMed

Shankar, Sunita; Evans, Mary Ann; Bobier, William R

2007-11-01

To compare emergent literacy skills in uncorrected hyperopic and emmetropic children. "Hyperopes" (>or=2.00 D sphere along the most hyperopic meridian; n=13; aged 67+/-13 mo) and "emmetropes" (

Seven-year incidence of uncorrected refractive error among an elderly Chinese population in Shihpai, Taiwan: The Shihpai Eye Study

PubMed Central

Kuang, T-M; Tsai, S-Y; Liu, C J-L; Ko, Y-C; Lee, S-M; Chou, P

2016-01-01

Purpose To report the 7-year incidence of uncorrected refractive error in a metropolitan Chinese elderly population. Methods The Shihpai Eye Study 2006 included 460/824 (55.8%) subjects (age range 72–94 years old) of 1361 participants in the 1999 baseline survey for a follow-up eye examination. Visual acuity was assessed using a Snellen chart, uncorrected refractive error was defined as presenting visual acuity (naked eye if without spectacles and with distance spectacles if worn) in the better eye of <6/12 that improved to no impairment (≥6/12) after refractive correction. Results The 7-year incidence of uncorrected refractive error was 10.5% (95% confidence interval (CI): 7.6–13.4%). 92.7% of participants with uncorrection and 77.8% with undercorrection were able to improve at least two lines of visual acuity by refractive correction. In multivariate analysis controlling for covariates, uncorrected refractive error was significantly related to myopia (relative risk (RR): 3.15; 95% CI: 1.31–7.58) and living alone (RR: 2.94; 95% CI 1.14–7.53), whereas distance spectacles worn during examination was protective (RR: 0.35; 95% CI: 0.14–0.88). Conclusion Our study indicated that the incidence of uncorrected refractive error was high (10.5%) in this elderly Chinese population. Living alone and myopia are predisposing factors, whereas wearing distance spectacles at examination is protective. PMID:26795416

Global magnitude of visual impairment caused by uncorrected refractive errors in 2004

PubMed Central

Pascolini, Donatella; Mariotti, Silvio P; Pokharel, Gopal P

2008-01-01

Abstract Estimates of the prevalence of visual impairment caused by uncorrected refractive errors in 2004 have been determined at regional and global levels for people aged 5 years and over from recent published and unpublished surveys. The estimates were based on the prevalence of visual acuity of less than 6/18 in the better eye with the currently available refractive correction that could be improved to equal to or better than 6/18 by refraction or pinhole. A total of 153 million people (range of uncertainty: 123 million to 184 million) are estimated to be visually impaired from uncorrected refractive errors, of whom eight million are blind. This cause of visual impairment has been overlooked in previous estimates that were based on best-corrected vision. Combined with the 161 million people visually impaired estimated in 2002 according to best-corrected vision, 314 million people are visually impaired from all causes: uncorrected refractive errors become the main cause of low vision and the second cause of blindness. Uncorrected refractive errors can hamper performance at school, reduce employability and productivity, and generally impair quality of life. Yet the correction of refractive errors with appropriate spectacles is among the most cost-effective interventions in eye health care. The results presented in this paper help to unearth a formerly hidden problem of public health dimensions and promote policy development and implementation, programmatic decision-making and corrective interventions, as well as stimulate research. PMID:18235892

Dynamics of active emmetropisation in young chicks – influence of sign and magnitude of imposed defocus

PubMed Central

Hammond, David S; Wallman, Josh; Wildsoet, Christine F

2014-01-01

Purpose Young eyes compensate for the defocus imposed by spectacle lenses by changing their rate of elongation and their choroidal thickness, bringing their refractive status back to the pre-lens condition. We asked whether the initial rate of change either in the ocular components or in refraction is a function of the power of the lenses worn, a result that would be consistent with the existence of a proportional controller mechanism. Methods Two separate studies were conducted; both tracked changes in refractive errors and ocular dimensions. Study A: To study the effects of lens power and sign, young chicks were tracked for 4 days after they were fitted with positive (+5, +10 or +15 D) or negative (−5, −10, −15 D) lenses over one eye. In another experiment, biometric changes to plano, +1, +2 and +3 D lenses were tracked over a 24 h treatment period. Study B: Normal emmetropisation was tracked from hatching to 6 days of age and then a defocusing lens, either +6 D or −7 D, was fitted over one eye and additional biometric data collected after 48 h. Results In study A, animals treated with positive lenses (+5, +10 or +15 D) showed statistical similar initial choroid responses, with a mean thickening 24 μm h−1 over the first 5 h. Likewise, with the low power positive lenses, a statistically similar magnitude of choroidal thickening was observed across groups (+1 D: 46.0 ± 7.8 μm h−1; +2 D: 53.5 ± 9.9 μm h−1; +3 D 53.3 ± 24.1 μm h−1) in the first hour of lens wear compared to that of a plano control group. These similar rates of change in choroidal thickness indicate that the signalling response is binary in nature and not influenced by the magnitude of the myopic defocus. Treatments with −5, −10 and −15 D lenses induced statistically similar amounts of choroidal thinning, averaging −70 ± 15 μm after 5h and −96 ± 45 μm after 24 h. Similar rates in inner axial length changes were also seen with these lens treatments until compensation was reached, once again indicating that the signalling response is not influenced by the magnitude of hyperopic defocus. In study B, after 48 h of +6 D lens treatment, the average refractive error and choroidal changes were found to be larger in magnitude than expected if perfect compensation had taken place, with a + 2.4 D overshoot in refractive compensation. Conclusion Taken together, our results with both weak and higher power positive lenses suggest that eye growth is guided more by the sign than by the magnitude of the defocus, and our results for higher power negative lenses support a similar conclusion. These behaviour patterns and the overshoot seen in Study B are more consistent with the behaviour of a bang-bang controller than a proportional controller. PMID:23662956

Prevalence of refractive error and visual impairment among rural school-age children of Goro District, Gurage Zone, Ethiopia.

PubMed

Kedir, Jafer; Girma, Abonesh

2014-10-01

Refractive error is one of the major causes of blindness and visual impairment in children; but community based studies are scarce especially in rural parts of Ethiopia. So, this study aims to assess the prevalence of refractive error and its magnitude as a cause of visual impairment among school-age children of rural community. This community-based cross-sectional descriptive study was conducted from March 1 to April 30, 2009 in rural villages of Goro district of Gurage Zone, found south west of Addis Ababa, the capital of Ethiopia. A multistage cluster sampling method was used with simple random selection of representative villages in the district. Chi-Square and t-tests were used in the data analysis. A total of 570 school-age children (age 7-15) were evaluated, 54% boys and 46% girls. The prevalence of refractive error was 3.5% (myopia 2.6% and hyperopia 0.9%). Refractive error was the major cause of visual impairment accounting for 54% of all causes in the study group. No child was found wearing corrective spectacles during the study period. Refractive error was the commonest cause of visual impairment in children of the district, but no measures were taken to reduce the burden in the community. So, large scale community level screening for refractive error should be conducted and integrated with regular school eye screening programs. Effective strategies need to be devised to provide low cost corrective spectacles in the rural community.

Prevalence of refractive errors among school children in gondar town, northwest ethiopia.

PubMed

Yared, Assefa Wolde; Belaynew, Wasie Taye; Destaye, Shiferaw; Ayanaw, Tsegaw; Zelalem, Eshete

2012-10-01

Many children with poor vision due to refractive error remain undiagnosed and perform poorly in school. The situation is worse in the Sub-Saharan Africa, including Ethiopia, and current information is lacking. The objective of this study is to determine the prevalence of refractive error among children enrolled in elementary schools in Gondar town, Ethiopia. This was a cross-sectional study of 1852 students in 8 elementary schools. Subjects were selected by multistage random sampling. The study parameters were visual acuity (VA) evaluation and ocular examination. VA was measured by staff optometrists with the Snellen E-chart while students with subnormal vision were examined using pinhole, retinoscopy evaluation and subjective refraction by ophthalmologists. The study cohort was comprised of 45.8% males and 54.2% females from 8 randomly selected elementary schools with a response rate of 93%. Refractive errors in either eye were present in 174 (9.4%) children. Of these, myopia was diagnosed in 55 (31.6%) children in the right and left eyes followed by hyperopia in 46 (26.4%) and 39 (22.4%) in the right and left eyes respectively. Low myopia was the most common refractive error in 61 (49.2%) and 68 (50%) children for the right and left eyes respectively. Refractive error among children is a common problem in Gondar town and needs to be assessed at every health evaluation of school children for timely treatment.

Nature and Nurture: the complex genetics of myopia and refractive error

PubMed Central

Wojciechowski, Robert

2010-01-01

The refractive errors, myopia and hyperopia, are optical defects of the visual system that can cause blurred vision. Uncorrected refractive errors are the most common causes of visual impairment worldwide. It is estimated that 2.5 billion people will be affected by myopia alone with in the next decade. Experimental, epidemiological and clinical research has shown that refractive development is influenced by both environmental and genetic factors. Animal models have demonstrated that eye growth and refractive maturation during infancy are tightly regulated by visually-guided mechanisms. Observational data in human populations provide compelling evidence that environmental influences and individual behavioral factors play crucial roles in myopia susceptibility. Nevertheless, the majority of the variance of refractive error within populations is thought to be due to hereditary factors. Genetic linkage studies have mapped two dozen loci, while association studies have implicated more than 25 different genes in refractive variation. Many of these genes are involved in common biological pathways known to mediate extracellular matrix composition and regulate connective tissue remodeling. Other associated genomic regions suggest novel mechanisms in the etiology of human myopia, such as mitochondrial-mediated cell death or photoreceptor-mediated visual signal transmission. Taken together, observational and experimental studies have revealed the complex nature of human refractive variation, which likely involves variants in several genes and functional pathways. Multiway interactions between genes and/or environmental factors may also be important in determining individual risks of myopia, and may help explain the complex pattern of refractive error in human populations. PMID:21155761

Prevalence of the refractive errors by age and gender: the Mashhad eye study of Iran.

PubMed

Ostadimoghaddam, Hadi; Fotouhi, Akbar; Hashemi, Hassan; Yekta, Abbasali; Heravian, Javad; Rezvan, Farhad; Ghadimi, Hamidreza; Rezvan, Bijan; Khabazkhoob, Mehdi

2011-11-01

Refractive errors are a common eye problem. Considering the low number of population-based studies in Iran in this regard, we decided to determine the prevalence rates of myopia and hyperopia in a population in Mashhad, Iran. Cross-sectional population-based study. Random cluster sampling. Of 4453 selected individuals from the urban population of Mashhad, 70.4% participated. Refractive error was determined using manifest (age > 15 years) and cycloplegic refraction (age ≤ 15 years). Myopia was defined as a spherical equivalent of -0.5 diopter or worse. An spherical equivalent of +0.5 diopter or worse for non-cycloplegic refraction and an spherical equivalent of +2 diopter or worse for cycloplegic refraction was used to define hyperopia. Prevalence of refractive errors. The prevalence of myopia and hyperopia in individuals ≤ 15 years old was 3.64% (95% CI: 2.19-5.09) and 27.4% (95% CI: 23.72-31.09), respectively. The same measurements for subjects > 15 years of age was 22.36% (95% CI: 20.06-24.66) and 34.21% (95% CI: 31.57-36.85), respectively. Myopia was found to increase with age in individuals ≤ 15 years and decrease with age in individuals > 15 years of age. The rate of hyperopia showed a significant increase with age in individuals > 15 years. The prevalence of astigmatism was 25.64% (95% CI: 23.76-27.51). In children and the elderly, hyperopia is the most prevalent refractive error. After hyperopia, astigmatism is also of importance in older ages. Age is the most important demographic factor associated with different types of refractive errors. © 2011 The Authors. Clinical and Experimental Ophthalmology © 2011 Royal Australian and New Zealand College of Ophthalmologists.

A Novel Multi-Camera Calibration Method based on Flat Refractive Geometry

NASA Astrophysics Data System (ADS)

Huang, S.; Feng, M. C.; Zheng, T. X.; Li, F.; Wang, J. Q.; Xiao, L. F.

2018-03-01

Multi-camera calibration plays an important role in many field. In the paper, we present a novel multi-camera calibration method based on flat refractive geometry. All cameras can acquire calibration images of transparent glass calibration board (TGCB) at the same time. The application of TGCB leads to refractive phenomenon which can generate calibration error. The theory of flat refractive geometry is employed to eliminate the error. The new method can solve the refractive phenomenon of TGCB. Moreover, the bundle adjustment method is used to minimize the reprojection error and obtain optimized calibration results. Finally, the four-cameras calibration results of real data show that the mean value and standard deviation of the reprojection error of our method are 4.3411e-05 and 0.4553 pixel, respectively. The experimental results show that the proposed method is accurate and reliable.

Reduced vision and refractive errors, results from a school vision screening program in Kanchanpur District of far western Nepal.

PubMed

Awasthi, S; Pant, B P; Dhakal, H P

2010-01-01

At present there is no data available on reduced vision and refractive errors in school children of far western Nepal. So, school screening records were used to obtain data useful for planning of refractive services. Data are provided from school screening conducted by Geta Eye Hospital during February/March 2008. The cases with complete data sets on visual acuity, refractive error and age were included and analyzed using computer software. Of 1165 children (mean age 11.6 ± 2.5 years) examined, 98.8% (n = 1151) had uncorrected visual acuity of 6/9 and better in at least one eye whereas 1.2% (n = 14) had acuity 6/12 and worse in both eyes. Among them, either eye of 9 children improved to 6/9 and better with correction. However, visual acuity was 6/12 and worse in both eyes of 5 children even after correction. There were 24 children with refractive errors (myopia, 1.54%; n = 18 and hypermetropia, 0.51%; n = 6) in at least one eye. The spherical equivalent refraction was not significantly different with age and gender. The incidence of reduced vision and refractive errors among school children of this semi rural district were low.

High Prevalence of Refractive Errors in 7 Year Old Children in Iran.

PubMed

Hashemi, Hassan; Yekta, Abbasali; Jafarzadehpur, Ebrahim; Ostadimoghaddam, Hadi; Etemad, Koorosh; Asharlous, Amir; Nabovati, Payam; Khabazkhoob, Mehdi

2016-02-01

The latest WHO report indicates that refractive errors are the leading cause of visual impairment throughout the world. The aim of this study was to determine the prevalence of myopia, hyperopia, and astigmatism in 7 yr old children in Iran. In a cross-sectional study in 2013 with multistage cluster sampling, first graders were randomly selected from 8 cities in Iran. All children were tested by an optometrist for uncorrected and corrected vision, and non-cycloplegic and cycloplegic refraction. Refractive errors in this study were determined based on spherical equivalent (SE) cyloplegic refraction. From 4614 selected children, 89.0% participated in the study, and 4072 were eligible. The prevalence rates of myopia, hyperopia and astigmatism were 3.04% (95% CI: 2.30-3.78), 6.20% (95% CI: 5.27-7.14), and 17.43% (95% CI: 15.39-19.46), respectively. Prevalence of myopia (P=0.925) and astigmatism (P=0.056) were not statistically significantly different between the two genders, but the odds of hyperopia were 1.11 (95% CI: 1.01-2.05) times higher in girls (P=0.011). The prevalence of with-the-rule astigmatism was 12.59%, against-the-rule was 2.07%, and oblique 2.65%. Overall, 22.8% (95% CI: 19.7-24.9) of the schoolchildren in this study had at least one type of refractive error. One out of every 5 schoolchildren had some refractive error. Conducting multicenter studies throughout the Middle East can be very helpful in understanding the current distribution patterns and etiology of refractive errors compared to the previous decade.

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.

Comparison between refractometer and retinoscopy in determining refractive errors in children--false doubt.

PubMed

Pokupec, Rajko; Mrazovac, Danijela; Popović-Suić, Smiljka; Mrazovac, Visnja; Kordić, Rajko; Petricek, Igor

2013-04-01

Early detection of a refractive error and its correction are extremely important for the prevention of amblyopia (poor vision). The golden standard in the detection of refractive errors is retinoscopy--a method where the pupils are dilated in order to exclude accomodation. This results in a more accurate measurement of a refractive error. Automatic computer refractometer is also in use. The study included 30 patients, 15 boys, 15 girls aged 4-16. The first examination was conducted with refractometer on narrow pupils. Retinoscopy, followed by another examination with refractometer was performed on pupils dilated with mydriatic drops administered 3 times. The results obtained with three methods were compared. They indicate that in narrow pupils the autorefractometer revealed an increased diopter value in nearsightedness (myopia), the minus overcorrection, whereas findings obtained with retinoscopy and autorefractometer in mydriasis cycloplegia, were much more accurate. The results were statistically processed, which confirmed the differences between obtained measurements. These findings are consistent with the results of studies conducted by other authors. Automatic refractometry on narrow pupils has proven to be a method for detection of refractive errors in children. However, the exact value of the refractive error is obtained only in mydriasis--with retinoscopy or an automatic refractometer on dilated pupils.

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.

Prevalence of refractive errors in children in Equatorial Guinea.

PubMed

Soler, Margarita; Anera, Rosario G; Castro, José J; Jiménez, Raimundo; Jiménez, José R

2015-01-01

The aim of this work is to evaluate the epidemiological aspects of the refractive errors in school-aged children in Malabo (Island of Bioko), Equatorial Guinea (western-central Africa). A total of 425 schoolchildren (209 male subjects and 216 female subjects, aged between 6 and 16 years) were examined to evaluate their refraction errors in Malabo, Equatorial Guinea (western-central Africa). The examination included autorefraction with cycloplegia, measurement of visual acuity (VA) for far vision, and the curvature radii of the main meridians of the anterior surface of the cornea. A low prevalence of myopia was found (≤-0.50 diopters [D] spherical equivalent), with unilateral and bilateral myopia being 10.4 and 5.2%, respectively. The prevalence of unilateral and bilateral hypermetropia (≥2.0 D spherical equivalent) was 3.1 and 1.6%, respectively. Astigmatism (≤-0.75 D) was found in unilateral form in 32.5% of these children, whereas bilateral astigmatism was found in 11.8%. After excluding children having any ocular pathology, the low prevalence of high refractive errors signified good VA in these children. Significant differences were found in the distribution of the refractive errors by age and type of schooling (public or private) but not by sex. In general, the radii of the anterior of the cornea did not vary significantly with age. The mean refractive errors found were low and therefore VA was high in these children. There was a low prevalence of myopia, with significantly higher values in those who attended private schools (educationally and socioeconomically more demanding). Astigmatism was the most frequent refractive error.

Reducing visual deficits caused by refractive errors in school and preschool children: results of a pilot school program in the Andean region of Apurimac, Peru.

PubMed

Latorre-Arteaga, Sergio; Gil-González, Diana; Enciso, Olga; Phelan, Aoife; García-Muñoz, Angel; Kohler, Johannes

2014-01-01

Refractive error is defined as the inability of the eye to bring parallel rays of light into focus on the retina, resulting in nearsightedness (myopia), farsightedness (Hyperopia) or astigmatism. Uncorrected refractive error in children is associated with increased morbidity and reduced educational opportunities. Vision screening (VS) is a method for identifying children with visual impairment or eye conditions likely to lead to visual impairment. To analyze the utility of vision screening conducted by teachers and to contribute to a better estimation of the prevalence of childhood refractive errors in Apurimac, Peru. Design : A pilot vision screening program in preschool (Group I) and elementary school children (Group II) was conducted with the participation of 26 trained teachers. Children whose visual acuity was<6/9 [20/30] (Group I) and ≤ 6/9 (Group II) in one or both eyes, measured with the Snellen Tumbling E chart at 6 m, were referred for a comprehensive eye exam. Specificity and positive predictive value to detect refractive error were calculated against clinical examination. Program assessment with participants was conducted to evaluate outcomes and procedures. A total sample of 364 children aged 3-11 were screened; 45 children were examined at Centro Oftalmológico Monseñor Enrique Pelach (COMEP) Eye Hospital. Prevalence of refractive error was 6.2% (Group I) and 6.9% (Group II); specificity of teacher vision screening was 95.8% and 93.0%, while positive predictive value was 59.1% and 47.8% for each group, respectively. Aspects highlighted to improve the program included extending training, increasing parental involvement, and helping referred children to attend the hospital. Prevalence of refractive error in children is significant in the region. Vision screening performed by trained teachers is a valid intervention for early detection of refractive error, including screening of preschool children. Program sustainability and improvements in education and quality of life resulting from childhood vision screening require further research.

The Contributions of Near Work and Outdoor Activity to the Correlation Between Siblings in the Collaborative Longitudinal Evaluation of Ethnicity and Refractive Error (CLEERE) Study

PubMed Central

Jones-Jordan, Lisa A.; Sinnott, Loraine T.; Graham, Nicholas D.; Cotter, Susan A.; Kleinstein, Robert N.; Manny, Ruth E.; Mutti, Donald O.; Twelker, J. Daniel; Zadnik, Karla

2014-01-01

Purpose. We determined the correlation between sibling refractive errors adjusted for shared and unique environmental factors using data from the Collaborative Longitudinal Evaluation of Ethnicity and Refractive Error (CLEERE) Study. Methods. Refractive error from subjects' last study visits was used to estimate the intraclass correlation coefficient (ICC) between siblings. The correlation models used environmental factors (diopter-hours and outdoor/sports activity) assessed annually from parents by survey to adjust for shared and unique environmental exposures when estimating the heritability of refractive error (2*ICC). Results. Data from 700 families contributed to the between-sibling correlation for spherical equivalent refractive error. The mean age of the children at the last visit was 13.3 ± 0.90 years. Siblings engaged in similar amounts of near and outdoor activities (correlations ranged from 0.40–0.76). The ICC for spherical equivalent, controlling for age, sex, ethnicity, and site was 0.367 (95% confidence interval [CI] = 0.304, 0.420), with an estimated heritability of no more than 0.733. After controlling for these variables, and near and outdoor/sports activities, the resulting ICC was 0.364 (95% CI = 0.304, 0.420; estimated heritability no more than 0.728, 95% CI = 0.608, 0.850). The ICCs did not differ significantly between male–female and single sex pairs. Conclusions. Adjusting for shared family and unique, child-specific environmental factors only reduced the estimate of refractive error correlation between siblings by 0.5%. Consistent with a lack of association between myopia progression and either near work or outdoor/sports activity, substantial common environmental exposures had little effect on this correlation. Genetic effects appear to have the major role in determining the similarity of refractive error between siblings. PMID:25205866

Ray tracing evaluation of a technique for correcting the refraction errors in satellite tracking data

NASA Technical Reports Server (NTRS)

Gardner, C. S.; Rowlett, J. R.; Hendrickson, B. E.

1978-01-01

Errors may be introduced in satellite laser ranging data by atmospheric refractivity. Ray tracing data have indicated that horizontal refractivity gradients may introduce nearly 3-cm rms error when satellites are near 10-degree elevation. A correction formula to compensate for the horizontal gradients has been developed. Its accuracy is evaluated by comparing it to refractivity profiles. It is found that if both spherical and gradient correction formulas are employed in conjunction with meteorological measurements, a range resolution of one cm or less is feasible for satellite elevation angles above 10 degrees.

Linkage analysis of quantitative refraction and refractive errors in the Beaver Dam Eye Study.

PubMed

Klein, Alison P; Duggal, Priya; Lee, Kristine E; Cheng, Ching-Yu; Klein, Ronald; Bailey-Wilson, Joan E; Klein, Barbara E K

2011-07-13

Refraction, as measured by spherical equivalent, is the need for an external lens to focus images on the retina. While genetic factors play an important role in the development of refractive errors, few susceptibility genes have been identified. However, several regions of linkage have been reported for myopia (2q, 4q, 7q, 12q, 17q, 18p, 22q, and Xq) and for quantitative refraction (1p, 3q, 4q, 7p, 8p, and 11p). To replicate previously identified linkage peaks and to identify novel loci that influence quantitative refraction and refractive errors, linkage analysis of spherical equivalent, myopia, and hyperopia in the Beaver Dam Eye Study was performed. Nonparametric, sibling-pair, genome-wide linkage analyses of refraction (spherical equivalent adjusted for age, education, and nuclear sclerosis), myopia and hyperopia in 834 sibling pairs within 486 extended pedigrees were performed. Suggestive evidence of linkage was found for hyperopia on chromosome 3, region q26 (empiric P = 5.34 × 10(-4)), a region that had shown significant genome-wide evidence of linkage to refraction and some evidence of linkage to hyperopia. In addition, the analysis replicated previously reported genome-wide significant linkages to 22q11 of adjusted refraction and myopia (empiric P = 4.43 × 10(-3) and 1.48 × 10(-3), respectively) and to 7p15 of refraction (empiric P = 9.43 × 10(-4)). Evidence was also found of linkage to refraction on 7q36 (empiric P = 2.32 × 10(-3)), a region previously linked to high myopia. The findings provide further evidence that genes controlling refractive errors are located on 3q26, 7p15, 7p36, and 22q11.

Heritability of lenticular myopia in English Springer spaniels.

PubMed

Kubai, Melissa A; Labelle, Amber L; Hamor, Ralph E; Mutti, Donald O; Famula, Thomas R; Murphy, Christopher J

2013-11-08

We determined whether naturally-occurring lenticular myopia in English Springer spaniels (ESS) has a genetic component. Streak retinoscopy was performed on 226 related ESS 30 minutes after the onset of pharmacologic mydriasis and cycloplegia. A pedigree was constructed to determine relationships between affected offspring and parents. Estimation of heritability was done in a Bayesian analysis (facilitated by the MCMCglmm package of R) of refractive error in a model, including terms for sex and coat color. Myopia was defined as ≤-0.5 diopters (D) spherical equivalent. The median refractive error for ESS was 0.25 D (range, -3.5 to +4.5 D). Median age was 0.2 years (range, 0.1-15 years). The prevalence of myopia in related ESS was 19% (42/226). The ESS had a strong correlation (r = 0.95) for refractive error between the two eyes. Moderate heritability was present for refractive error with a mean value of 0.29 (95% highest probability density, 0.07-0.50). The distribution of refractive error, and subsequently lenticular myopia, has a moderate genetic component in ESS. Further investigation of genes responsible for regulation of the development of refractive ocular components in canines is warranted.

Myopia in secondary school students in Mwanza City, Tanzania: the need for a national screening programme

PubMed Central

Wedner, S H; Ross, D A; Todd, J; Anemona, A; Balira, R; Foster, A

2002-01-01

Background/aims: The prevalence of significant refractive errors and other eye diseases was measured in 2511 secondary school students aged 11–27 years in Mwanza City, Tanzania. Risk factors for myopia were explored. Methods: A questionnaire assessed the students’ socioeconomic background and exposure to near work followed by visual acuity assessment and a full eye examination. Non-cycloplegic objective and subjective refraction was done on all participants with visual acuity of worse than 6/12 in either eye without an obvious cause. Results: 154 (6.1%) students had significant refractive errors. Myopia was the leading refractive error (5.6%). Amblyopia (0.4%), strabismus (0.2%), and other treatable eye disorders were uncommon. Only 30.3% of students with significant refractive errors wore spectacles before the survey. Age, sex, ethnicity, father’s educational status, and a family history of siblings with spectacles were significant independent risk factors for myopia. Conclusion: The prevalence of uncorrected significant refractive errors is high enough to justify a regular school eye screening programme in secondary schools in Tanzania. Risk factors for myopia are similar to those reported in European, North-American, and Asian populations. PMID:12386067

Clinical Outcomes of an Optimized Prolate Ablation Procedure for Correcting Residual Refractive Errors Following Laser Surgery.

PubMed

Chung, Byunghoon; Lee, Hun; Choi, Bong Joon; Seo, Kyung Ryul; Kim, Eung Kwon; Kim, Dae Yune; Kim, Tae-Im

2017-02-01

The purpose of this study was to investigate the clinical efficacy of an optimized prolate ablation procedure for correcting residual refractive errors following laser surgery. We analyzed 24 eyes of 15 patients who underwent an optimized prolate ablation procedure for the correction of residual refractive errors following laser in situ keratomileusis, laser-assisted subepithelial keratectomy, or photorefractive keratectomy surgeries. Preoperative ophthalmic examinations were performed, and uncorrected distance visual acuity, corrected distance visual acuity, manifest refraction values (sphere, cylinder, and spherical equivalent), point spread function, modulation transfer function, corneal asphericity (Q value), ocular aberrations, and corneal haze measurements were obtained postoperatively at 1, 3, and 6 months. Uncorrected distance visual acuity improved and refractive errors decreased significantly at 1, 3, and 6 months postoperatively. Total coma aberration increased at 3 and 6 months postoperatively, while changes in all other aberrations were not statistically significant. Similarly, no significant changes in point spread function were detected, but modulation transfer function increased significantly at the postoperative time points measured. The optimized prolate ablation procedure was effective in terms of improving visual acuity and objective visual performance for the correction of persistent refractive errors following laser surgery.

Prevalence and predictors of refractive error and spectacle coverage in Nakuru, Kenya: a cross-sectional, population-based study.

PubMed

Bastawrous, Andrew; Mathenge, Wanjiku; Foster, Allen; Kuper, Hannah

2013-10-01

A cross-sectional study was undertaken in Nakuru, Kenya to assess the prevalence of refractive error and the spectacle coverage in a population aged ≥50 years. Of the 5,010 subjects who were eligible, 4,414 underwent examination (response rate 88.1 %). LogMAR visual acuity was assessed in all participants and refractive error was measured in both eyes using a Topcon auto refractor RM8800. Detailed interviews were undertaken and ownership of spectacles was assessed. Refractive error was responsible for 51.7 % of overall visual impairment (VI), 85.3 % (n = 191) of subjects with mild VI, 42.7 % (n = 152) of subjects with moderate VI, 16.7 % (n = 3) of subjects with severe VI and no cases of blindness. Myopia was more common than hyperopia affecting 59.5 % of those with refractive error compared to 27.4 % for hyperopia. High myopia (<-5.0 DS) was also more common than extreme hyperopia (>+5.0 DS). Of those who needed distance spectacles (spectacle coverage), 25.5 % owned spectacles. In conclusion, the oldest, most poor and least educated are most likely to have no spectacles and they should be specifically targeted when refractive services are put in place.

Prevalence of Refractive Errors Among School Children in Gondar Town, Northwest Ethiopia

PubMed Central

Yared, Assefa Wolde; Belaynew, Wasie Taye; Destaye, Shiferaw; Ayanaw, Tsegaw; Zelalem, Eshete

2012-01-01

Purpose: Many children with poor vision due to refractive error remain undiagnosed and perform poorly in school. The situation is worse in the Sub-Saharan Africa, including Ethiopia, and current information is lacking. The objective of this study is to determine the prevalence of refractive error among children enrolled in elementary schools in Gondar town, Ethiopia. Materials and Methods: This was a cross-sectional study of 1852 students in 8 elementary schools. Subjects were selected by multistage random sampling. The study parameters were visual acuity (VA) evaluation and ocular examination. VA was measured by staff optometrists with the Snellen E-chart while students with subnormal vision were examined using pinhole, retinoscopy evaluation and subjective refraction by ophthalmologists. Results: The study cohort was comprised of 45.8% males and 54.2% females from 8 randomly selected elementary schools with a response rate of 93%. Refractive errors in either eye were present in 174 (9.4%) children. Of these, myopia was diagnosed in 55 (31.6%) children in the right and left eyes followed by hyperopia in 46 (26.4%) and 39 (22.4%) in the right and left eyes respectively. Low myopia was the most common refractive error in 61 (49.2%) and 68 (50%) children for the right and left eyes respectively. Conclusions: Refractive error among children is a common problem in Gondar town and needs to be assessed at every health evaluation of school children for timely treatment. PMID:23248538

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.

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.

Accommodative insufficiency in a student population in Iran.

PubMed

Hashemi, Hassan; Khabazkhoob, Mehdi; Nabovati, Payam; Shahraki, Fatemeh Azad; Ostadimoghaddam, Hadi; Faghihi, Mohammad; Aghamirsalim, Mohamadreza; Doostdar, Asgar; Yekta, Abbasali

2018-05-22

To determine the prevalence of accommodative insufficiency (AI) and its relation with age, gender, and refractive errors in a college-age student population in Iran. The present study was conducted cross-sectionally in 2017. All students had optometric tests including measurement of visual acuity, objective and subjective refraction, as well as binocular vision and accommodative examinations. Amplitude of accommodation was measured with the Donders' push-up method using the Royal Air Force (RAF) rule. Monocular accommodative facility was measured with ±2.00diopter flipper lenses. The accommodative response was tested using dynamic retinoscopy with the monocular estimation method (MEM). The prevalence of AI in the studied population was 4.07% (95% CI: 2.61-5.52). The rate was 6.04% (95% CI: 3.58-8.50) in females and 2.01% (95% CI: 0.53-3.48) in males, and logistic regression showed a significantly higher odds of AI in females (OR=3.14, 95% CI: 1.33-7.45, p-value=0.009). The prevalence of AI was 2.59% (95% CI: 0.55-7.56) in the 18-19-year-old age group and 4.08% (95% CI: 0.09-8.07) in the 24-25-year-old group (p-value=0.848). The prevalence of AI among emmetropic, myopic, and hyperopic individuals was 3.74% (95% CI: 1.88-5.61), 4.44% (95% CI: 2.07-6.81), and 5.26% (95% CI: 4.79-16.32), respectively (p-value=0.869). In the multiple regression model, only gender showed significant relationship with AI (Odds ratio=3.14, 95% CI: 1.33-7.45; p-values=0.009). The prevalence of AI in the present study is lower than the most prevalence rates reported in previous studies. In the present study, gender and AI showed a strong association, such that AI prevalence was significantly higher in females than males. Copyright © 2018 Spanish General Council of Optometry. Published by Elsevier España, S.L.U. All rights reserved.

Relationship between visual field progression and baseline refraction in primary open-angle glaucoma.

PubMed

Naito, Tomoko; Yoshikawa, Keiji; Mizoue, Shiro; Nanno, Mami; Kimura, Tairo; Suzumura, Hirotaka; Umeda, Yuzo; Shiraga, Fumio

2016-01-01

To analyze the relationship between visual field (VF) progression and baseline refraction in Japanese patients with primary open-angle glaucoma (POAG) including normal-tension glaucoma. In this retrospective study, the subjects were patients with POAG who had undergone VF tests at least ten times with a Humphrey Field Analyzer (Swedish interactive thresholding algorithm standard, Central 30-2 program). VF progression was defined as a significantly negative value of mean deviation (MD) slope at the final VF test. Multivariate logistic regression models were applied to detect an association between MD slope deterioration and baseline refraction. A total of 156 eyes of 156 patients were included in this analysis. Significant deterioration of MD slope was observed in 70 eyes of 70 patients (44.9%), whereas no significant deterioration was evident in 86 eyes of 86 patients (55.1%). The eyes with VF progression had significantly higher baseline refraction compared to those without apparent VF progression (-1.9±3.8 diopter [D] vs -3.5±3.4 D, P=0.0048) (mean ± standard deviation). When subject eyes were classified into four groups by the level of baseline refraction applying spherical equivalent (SE): no myopia (SE > -1D), mild myopia (-1D ≥ SE > -3D), moderate myopia (-3D ≥ SE > -6D), and severe myopia (-6D ≥ SE), the Cochran-Armitage trend analysis showed a decreasing trend in the proportion of MD slope deterioration with increasing severity of myopia (P=0.0002). The multivariate analysis revealed that baseline refraction (P=0.0108, odds ratio [OR]: 1.13, 95% confidence interval [CI]: 1.03-1.25) and intraocular pressure reduction rate (P=0.0150, OR: 0.97, 95% CI: 0.94-0.99) had a significant association with MD slope deterioration. In the current analysis of Japanese patients with POAG, baseline refraction was a factor significantly associated with MD slope deterioration as well as intraocular pressure reduction rate. When baseline refraction was classified into four groups, MD slope in myopia groups was less deteriorated as compared to those in the emmetropic/hyperopic group.

Association of Body Length with Ocular Parameters in Mice

PubMed Central

Chakraborty, Ranjay; Park, Han na; Tan, Christopher C.; Weiss, Paul; Prunt, Megan C.; Pardue, Machelle T.

2017-01-01

Purpose To determine the association between changes in body length with ocular refraction, corneal radii, axial length, and lens thickness in two different mouse strains. Methods Body length, ocular refraction, corneal radii, axial length, and lens thickness were measured for two inbred mouse strains: 129S1/SvJ (n=7) and C57BL/6J (n=10) from 4 to 12 weeks of age. Body length, from tip of nose to base of tail was obtained using a digital camera. Biometric parameters, corneal radii and refractions were measured using spectral-domain optical coherence tomography, automated keratometry and infrared photorefraction, respectively. A mixed model ANOVA was performed to examine the changes in ocular parameters as a function of body length and strain in mice controlling for age, gender and weight over time. Results C57BL/6J mice had significantly longer body length (average body length at 10 weeks, 8.60 ± 0.06 cm) compared 129S1/SvJ mice (8.31 ± 0.05 cm) during development (p<0.001). C57BL/6J mice had significantly hyperopic refractions compared to 129S1/SvJ mice across age (mean refraction at 10 weeks, 129S1/SvJ: +0.99 ± 0.44 D versus C57BL/6J: +6.24 ± 0.38 D, p<0.001). Corneal radius of curvature, axial length and lens thickness (except 10 weeks lens thickness) were similar between the two strains throughout the measurement. In the mixed model ANOVA, changes in body length showed an independent and significant association with the changes in refraction (p=0.002) and corneal radii (p=0.016) for each mouse strain. No significant association was found between the changes in axial length (p=0.925) or lens thickness (p=0.973) as a function of body length and strain. Conclusions Changes in body length are significantly associated with the changes in ocular refraction and corneal radii in different mouse strains. Future studies are needed to determine if the association between body length and ocular refraction are related to changes in corneal curvature in mice. PMID:28005683

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.

High Prevalence of Refractive Errors in 7 Year Old Children in Iran

PubMed Central

HASHEMI, Hassan; YEKTA, Abbasali; JAFARZADEHPUR, Ebrahim; OSTADIMOGHADDAM, Hadi; ETEMAD, Koorosh; ASHARLOUS, Amir; NABOVATI, Payam; KHABAZKHOOB, Mehdi

2016-01-01

Background: The latest WHO report indicates that refractive errors are the leading cause of visual impairment throughout the world. The aim of this study was to determine the prevalence of myopia, hyperopia, and astigmatism in 7 yr old children in Iran. Methods: In a cross-sectional study in 2013 with multistage cluster sampling, first graders were randomly selected from 8 cities in Iran. All children were tested by an optometrist for uncorrected and corrected vision, and non-cycloplegic and cycloplegic refraction. Refractive errors in this study were determined based on spherical equivalent (SE) cyloplegic refraction. Results: From 4614 selected children, 89.0% participated in the study, and 4072 were eligible. The prevalence rates of myopia, hyperopia and astigmatism were 3.04% (95% CI: 2.30–3.78), 6.20% (95% CI: 5.27–7.14), and 17.43% (95% CI: 15.39–19.46), respectively. Prevalence of myopia (P=0.925) and astigmatism (P=0.056) were not statistically significantly different between the two genders, but the odds of hyperopia were 1.11 (95% CI: 1.01–2.05) times higher in girls (P=0.011). The prevalence of with-the-rule astigmatism was 12.59%, against-the-rule was 2.07%, and oblique 2.65%. Overall, 22.8% (95% CI: 19.7–24.9) of the schoolchildren in this study had at least one type of refractive error. Conclusion: One out of every 5 schoolchildren had some refractive error. Conducting multicenter studies throughout the Middle East can be very helpful in understanding the current distribution patterns and etiology of refractive errors compared to the previous decade. PMID:27114984

Novel Myopia Genes and Pathways Identified From Syndromic Forms of Myopia

PubMed Central

Loughman, James; Wildsoet, Christine F.; Williams, Cathy; Guggenheim, Jeremy A.

2018-01-01

Purpose To test the hypothesis that genes known to cause clinical syndromes featuring myopia also harbor polymorphisms contributing to nonsyndromic refractive errors. Methods Clinical phenotypes and syndromes that have refractive errors as a recognized feature were identified using the Online Mendelian Inheritance in Man (OMIM) database. One hundred fifty-four unique causative genes were identified, of which 119 were specifically linked with myopia and 114 represented syndromic myopia (i.e., myopia and at least one other clinical feature). Myopia was the only refractive error listed for 98 genes and hyperopia and the only refractive error noted for 28 genes, with the remaining 28 genes linked to phenotypes with multiple forms of refractive error. Pathway analysis was carried out to find biological processes overrepresented within these sets of genes. Genetic variants located within 50 kb of the 119 myopia-related genes were evaluated for involvement in refractive error by analysis of summary statistics from genome-wide association studies (GWAS) conducted by the CREAM Consortium and 23andMe, using both single-marker and gene-based tests. Results Pathway analysis identified several biological processes already implicated in refractive error development through prior GWAS analyses and animal studies, including extracellular matrix remodeling, focal adhesion, and axon guidance, supporting the research hypothesis. Novel pathways also implicated in myopia development included mannosylation, glycosylation, lens development, gliogenesis, and Schwann cell differentiation. Hyperopia was found to be linked to a different pattern of biological processes, mostly related to organogenesis. Comparison with GWAS findings further confirmed that syndromic myopia genes were enriched for genetic variants that influence refractive errors in the general population. Gene-based analyses implicated 21 novel candidate myopia genes (ADAMTS18, ADAMTS2, ADAMTSL4, AGK, ALDH18A1, ASXL1, COL4A1, COL9A2, ERBB3, FBN1, GJA1, GNPTG, IFIH1, KIF11, LTBP2, OCA2, POLR3B, POMT1, PTPN11, TFAP2A, ZNF469). Conclusions Common genetic variants within or nearby genes that cause syndromic myopia are enriched for variants that cause nonsyndromic, common myopia. Analysis of syndromic forms of refractive errors can provide new insights into the etiology of myopia and additional potential targets for therapeutic interventions. PMID:29346494

Prevalence of refractive errors in children in India: a systematic review.

PubMed

Sheeladevi, Sethu; Seelam, Bharani; Nukella, Phanindra B; Modi, Aditi; Ali, Rahul; Keay, Lisa

2018-04-22

Uncorrected refractive error is an avoidable cause of visual impairment which affects children in India. The objective of this review is to estimate the prevalence of refractive errors in children ≤ 15 years of age. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines were followed in this review. A detailed literature search was performed to include all population and school-based studies published from India between January 1990 and January 2017, using the Cochrane Library, Medline and Embase. The quality of the included studies was assessed based on a critical appraisal tool developed for systematic reviews of prevalence studies. Four population-based studies and eight school-based studies were included. The overall prevalence of refractive error per 100 children was 8.0 (CI: 7.4-8.1) and in schools it was 10.8 (CI: 10.5-11.2). The population-based prevalence of myopia, hyperopia (≥ +2.00 D) and astigmatism was 5.3 per cent, 4.0 per cent and 5.4 per cent, respectively. Combined refractive error and myopia alone were higher in urban areas compared to rural areas (odds ratio [OR]: 2.27 [CI: 2.09-2.45]) and (OR: 2.12 [CI: 1.79-2.50]), respectively. The prevalence of combined refractive errors and myopia alone in schools was higher among girls than boys (OR: 1.2 [CI: 1.1-1.3] and OR: 1.1 [CI: 1.1-1.2]), respectively. However, hyperopia was more prevalent among boys than girls in schools (OR: 2.1 [CI: 1.8-2.4]). Refractive error in children in India is a major public health problem and requires concerted efforts from various stakeholders including the health care workforce, education professionals and parents, to manage this issue. © 2018 Optometry Australia.

Effects of horizontal refractivity gradients on the accuracy of laser ranging to satellites

NASA Technical Reports Server (NTRS)

Gardner, C. S.

1976-01-01

Numerous formulas have been developed to partially correct laser ranging data for the effects of atmospheric refraction. All the formulas assume the atmospheric refractivity profile is spherically symmetric. The effects of horizontal refractivity gradients are investigated by ray tracing through spherically symmetric and three-dimensional refractivity profiles. The profiles are constructed from radiosonde data. The results indicate that the horizontal gradients introduce an rms error of approximately 3 cm when the satellite is near 10 deg elevation. The error decreases to a few millimeters near zenith.

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.

Prevalence of refractive errors in a Brazilian population: the Botucatu eye study.

PubMed

Schellini, Silvana Artioli; Durkin, Shane R; Hoyama, Erika; Hirai, Flavio; Cordeiro, Ricardo; Casson, Robert J; Selva, Dinesh; Padovani, Carlos Roberto

2009-01-01

To determine the prevalence and demographic associations of refractive error in Botucatu, Brazil. A population-based, cross-sectional prevalence study was conducted, which involved random, household cluster sampling of an urban Brazilian population in Botucatu. There were 3000 individuals aged 1 to 91 years (mean 38.3) who were eligible to participate in the study. Refractive error measurements were obtained by objective refraction. Objective refractive error examinations were performed on 2454 residents within this sample (81.8% of eligible participants). The mean age was 38 years (standard deviation (SD) 20.8 years, Range 1 to 91) and females comprised 57.5% of the study population. Myopia (spherical equivalent (SE) < -0.5 dropters (D)) was most prevalent among those aged 30-39 years (29.7%; 95% confidence interval (CI) 24.8-35.1) and least prevalent among children under 10 years (3.8%; 95% confidence interval (CI) 1.6-7.3). Conversely hypermetropia (SE > 0.5D) was most prevalent among participants under 10 years (86.9%; 95% CI 81.6-91.1) and least prevalent in the fourth decade (32.5%; 95% CI 28.2-37.0). Participants aged 70 years or older bore the largest burden of astigmatism (cylinder at least -0.5D) and anisometropia (difference in SE of > 0.5D) with a prevalence of 71.7% (95% CI 64.8-78.0) 55.0% (95% CI 47.6-62.2) respectively. Myopia and hypermetropia were significantly associated with age in a bimodal manner (P < 0.001), whereas anisometropia and astigmatism increased in line with age (P < 0.001). Multivariate modeling confirmed age-related risk factors for refractive error and revealed several gender, occupation and ethnic-related risk factors. These results represent previously unreported data on refractive error within this Brazilian population. They signal a need to continue to screen for refractive error within this population and to ensure that people have adequate access to optical correction.

The quality of systematic reviews about interventions for refractive error can be improved: a review of systematic reviews.

PubMed

Mayo-Wilson, Evan; Ng, Sueko Matsumura; Chuck, Roy S; Li, Tianjing

2017-09-05

Systematic reviews should inform American Academy of Ophthalmology (AAO) Preferred Practice Pattern® (PPP) guidelines. The quality of systematic reviews related to the forthcoming Preferred Practice Pattern® guideline (PPP) Refractive Errors & Refractive Surgery is unknown. We sought to identify reliable systematic reviews to assist the AAO Refractive Errors & Refractive Surgery PPP. Systematic reviews were eligible if they evaluated the effectiveness or safety of interventions included in the 2012 PPP Refractive Errors & Refractive Surgery. To identify potentially eligible systematic reviews, we searched the Cochrane Eyes and Vision United States Satellite database of systematic reviews. Two authors identified eligible reviews and abstracted information about the characteristics and quality of the reviews independently using the Systematic Review Data Repository. We classified systematic reviews as "reliable" when they (1) defined criteria for the selection of studies, (2) conducted comprehensive literature searches for eligible studies, (3) assessed the methodological quality (risk of bias) of the included studies, (4) used appropriate methods for meta-analyses (which we assessed only when meta-analyses were reported), (5) presented conclusions that were supported by the evidence provided in the review. We identified 124 systematic reviews related to refractive error; 39 met our eligibility criteria, of which we classified 11 to be reliable. Systematic reviews classified as unreliable did not define the criteria for selecting studies (5; 13%), did not assess methodological rigor (10; 26%), did not conduct comprehensive searches (17; 44%), or used inappropriate quantitative methods (3; 8%). The 11 reliable reviews were published between 2002 and 2016. They included 0 to 23 studies (median = 9) and analyzed 0 to 4696 participants (median = 666). Seven reliable reviews (64%) assessed surgical interventions. Most systematic reviews of interventions for refractive error are low methodological quality. Following widely accepted guidance, such as Cochrane or Institute of Medicine standards for conducting systematic reviews, would contribute to improved patient care and inform future research.

Refractive error among the elderly in rural Southern Harbin, China.

PubMed

Li, Zhijian; Sun, Dianjun; Cuj, Hao; Zhang, Liqiong; Lju, Ping; Yang, Hongbin; Baj, Jie

2009-01-01

To estimate the prevalence and associated factors of refractive errors among the elderly in a rural area of Southern Harbin, China. Five thousand and fifty seven subjects (age > or = 50 years) were enumerated for a population-based study. All participants underwent complete ophthalmic evaluation. Refraction was performed by ophthalmic personnel trained in the study procedures. Myopia was defined as spherical equivalent worse than -0.50 diopters (D) and hyperopia as spherical equivalent worse than +0.50 D. Astigmatism was defined as a cylindrical error worse than 0.75D. Association of refractive errors with age, sex, and education were analyzed. Of the 5,057 responders (91.0%), 4,979 were eligible. The mean age was 60.5 (range 50-96) years old. The prevalence of myopia was 9.5% (95% confidence interval [CI], 8.5-10.1) and of hyperopia was 8.9% (95% CI, 7.9-9.5). Astigmatism was evident in 7.6% of the subjects. Myopia, hyperopia and astigmatism increased with increasing age (p<0.001, respectively). Myopia and astigmatism were more common in males, whereas hyperopia was more common in females. We also found that prevalence of refractive error weas associated with education. Myopia was more common in those with higher degrees of education, whereas hyperopia and astigmatism were more common in those with no formal education. This report has provided details of the refractive status in a rural population of Harbin. The prevalence of refractive errors in this population is lower than those reported in other regions of the world.

Uncorrected refractive errors, presbyopia and spectacle coverage: results from a rapid assessment of refractive error survey.

PubMed

Marmamula, Srinivas; Keeffe, Jill E; Rao, Gullapalli N

2009-01-01

To investigate the prevalence of uncorrected refractive errors, presbyopia and spectacle coverage in subjects aged 15-50 years using rapid assessment methodology in the Mahabubnagar district of Andhra Pradesh, India. A population-based cross sectional study was conducted using cluster random sampling to enumerate 3,300 subjects from 55 clusters. Unaided, aided and pinhole visual acuity was assessed using a LogMAR chart at a distance of 4 meters. Near vision was assessed using N notation chart. Uncorrected refractive error was defined as presenting visual acuity worse than 6/12 but improving to at least 6/12 or better on using a pinhole. Presbyopia is defined as binocular near vision worse than N8 in subjects aged more than 35 years with binocular distance visual acuity of 6/12 or better. Of the 3,300 subjects enumerated from 55 clusters, 3,203 (97%) subjects were available for examination. Of these, 1,496 (46.7%) were females and 930 (29%) were > or = 40 years. Age and gender adjusted prevalence of uncorrected refractive errors causing visual impairment in the better eye was 2.7% (95% CI, 2.1-3.2%). Presbyopia was present in 690 (63.7%, 95% CI, 60.8-66.6%) subjects aged over 35 years. Spectacle coverage for refractive error was 29% and for presbyopia it was 19%. There is a large unmet need for refractive correction in this area in India. Rapid assessment methods are an effective means of assessing the need for services and the impact of models of care.

[Prevalence of refractive errors in 7 and 8 year-old children in the province of Western Pomerania].

PubMed

Muszyńska-Lachota, Izabela; Czepita, Damian; uczyńska, Violetta; Wysiecki, Przemysław

2005-01-01

To determine the prevalence of refractive errors in 7 and 8 year-old schoolchildren in the province of Western Pomerania. 140 pupils of elementary schools were examined. Measurements of visual acuity and retinoscopy after cycloplegia were carried out. Prevalence of hyperopia, myopia, and astigmatism was 76.1%, 3.3% and 5.1%, respectively. No statistically significant differences between 7 and 8 year-old children were found. 1. There is a relatively high prevalence of refractive errors, with hyperopia prevailing, among 7 and 8 year-old schoolchildren. 2. Myopia in young children is a cause for concern an further studies. 3. High prevalence of refractive errors in children calls for systematic examination and focused interviewing by medical professionals of the school health care system.

Occurrence of refractive errors among students who before the age of two grew up under the influence of light emitted by incandescent or fluorescent lamps.

PubMed

Czepita, Damian; Gosławski, Wojciech; Mojsa, Artur

2005-01-01

The aim 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 skiascopy 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 parents of all the students examined completed a questionnaire on the child's light exposure before the age oftwo. Data were analyzed statistically with the chi2 test. P values of less than 0.05 were considered statistically significant. It was observed that sleeping until the age of two in a room with a light turned on is associated with an increase in the occurrence of anisometropia (p < 0.02) as well as with a reduction in the prevalence of emmetropia (p < 0.05). It was also found that light emitted by fluorescent lamps leads to more frequent occurrence of astigmatism (p < 0.01).

Refractive errors in a Brazilian population: age and sex distribution.

PubMed

Ferraz, Fabio H; Corrente, José E; Opromolla, Paula; Padovani, Carlos Roberto; Schellini, Silvana A

2015-01-01

To determine the prevalence of refractive errors and their distribution according to age and sex in a Brazilian population. This population-based cross-sectional study involved 7654 Brazilian inhabitants of nine municipalities of Sao Paulo State, Brazil, between March 2004 and July 2005. Participants aged >1 year were selected using a random, stratified, household cluster sampling technique, excluding individuals with previous refractive or cataract surgery. Myopia was defined as spherical equivalent (SE) ≤-0.5D, high myopia as SE ≤-3.0D, hyperopia as SE ≥+0.5D, high hyperopia as SE ≥+3D, astigmatism as ≤-0.5DC and anisometropia as ≥1.0D difference between eyes. Age, sex, complaints and a comprehensive eye examination including cycloplegic refraction test were collected and analysed using descriptive analysis, univariate and multivariate methods. The prevalence of astigmatism was 59.7%, hyperopia 33.8% and myopia was 25.3%. Astigmatism had a progressive increase with age. With-the-rule (WTR) axes of astigmatism were more frequently observed in the young participants and the against-the-rule (ATR) axes were more frequent in the older subjects. The onset of myopia occurred more frequently between the 2nd and 3rd decades of life. Anisometropia showed a prevalence of 13.2% (95% CI 12.4-13.9; p < 0.001). There was an association between age and all types of refractive error and hyperopia was also associated with sex. Hyperopia was associated with WTR axes (odds ratio 0.73; 95% CI: 0.6-0.8; p < 0.001) and myopia with ATR axes (odds ratio 0.66; 95% CI: 0.6-0.8; p < 0.001). Astigmatism was the most prevalent refractive error in a Brazilian population. There was a strong relationship between age and all refractive errors and between hyperopia and sex. WTR astigmatism was more frequently associated with hyperopia and ATR astigmatism with myopia. The vast majority of participants had low-grade refractive error, which favours planning aimed at correction of refractive error in the population. © 2014 The Authors Ophthalmic & Physiological Optics © 2014 The College of Optometrists.

Prevalence of refractive error in malay primary school children in suburban area of Kota Bharu, Kelantan, Malaysia.

PubMed

Hashim, Syaratul-Emma; Tan, Hui-Ken; Wan-Hazabbah, W H; Ibrahim, Mohtar

2008-11-01

Refractive error remains one of the primary causes of visual impairment in children worldwide, and the prevalence of refractive error varies widely. The objective of this study was to determine the prevalence of refractive error and study the possible associated factors inducing refractive error among primary school children of Malay ethnicity in the suburban area of Kota Bharu, Kelantan, Malaysia. A school-based cross-sectional study was performed from January to July 2006 by random selection on Standard 1 to Standard 6 students of 10 primary schools in the Kota Bharu district. Visual acuity assessment was measured using logMAR ETDRS chart. Positive predictive value of uncorrected visual acuity equal or worse than 20/40, was used as a cut-off point for further evaluation by automated refraction and retinoscopic refraction. A total of 840 students were enumerated but only 705 were examined. The prevalence of uncorrected visual impairment was seen in 54 (7.7%) children. The main cause of the uncorrected visual impairment was refractive error which contributed to 90.7% of the total, and with 7.0% prevalence for the studied population. Myopia is the most common type of refractive error among children aged 6 to 12 years with prevalence of 5.4%, followed by hyperopia at 1.0% and astigmatism at 0.6%. A significant positive correlation was noted between myopia development with increasing age (P <0.005), more hours spent on reading books (P <0.005) and background history of siblings with glasses (P <0.005) and whose parents are of higher educational level (P <0.005). Malays in suburban Kelantan (5.4%) have the lowest prevalence of myopia compared with Malays in the metropolitan cities of Kuala Lumpur (9.2%) and Singapore (22.1%). The ethnicity-specific prevalence rate of myopia was the lowest among Malays in Kota Bharu, followed by Kuala Lumpur, and is the highest among Singaporean Malays. Better socio-economic factors could have contributed to higher myopia rates in the cities, since the genetic background of these ethnic Malays are similar.

The U.S. Air Force Photorefractive Keratectomy (PRK) Study: Evaluation of Residual Refractive Error and High- and Low-Contrast Visual Acuity

DTIC Science & Technology

2006-07-01

values for statistical analyses in terms of Snellen equivalent VA (Ref 44) and lines gained vs . lost after PRK . The Snellen VA values shown in the...AFRL-SA-BR-TR-2010-0011 THE U.S. AIR FORCE PHOTOREFRACTIVE KERATECTOMY ( PRK ) STUDY: Evaluation of Residual Refractive Error and High...July 2006 4. TITLE AND SUBTITLE THE U.S. AIR FORCE PHOTOREFRACTIVE KERATECTOMY ( PRK ) STUDY: Evaluation of Residual Refractive Error and High- and

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.

Visual impairment in urban school children of low-income families in Kolkata, India.

PubMed

Ghosh, Sambuddha; Mukhopadhyay, Udayaditya; Maji, Dipankar; Bhaduri, Gautam

2012-01-01

To evaluate pattern of visual impairment in school children from low-income families in Kolkata, India, an institutional cross-sectional study was conducted among 2570 children of 10 primary schools. Ocular examination including refraction was done and pattern of visual impairment and refractive error was studied. The age range was 6-14 years. Refractive error was seen in 14.7%. Only 4 children were already wearing correction. Myopia and hypermetropia was present in 307 (11.9%) and 65 (2.5%) children, respectively. Visual acuity of less than 6/12 in better eye was present in 109 (4.2%) and 5 (0.2%) children pre- and post-correction, respectively. Eighteen children had amblyopia. Although prevalence of refractive error in this group is less compared to school children of all income categories reported from other cities of India, it is more compared to school children of all income categories from the same city. Refractive error mostly remains uncorrected in this group.

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.

Reducing visual deficits caused by refractive errors in school and preschool children: results of a pilot school program in the Andean region of Apurimac, Peru

PubMed Central

Latorre-Arteaga, Sergio; Gil-González, Diana; Enciso, Olga; Phelan, Aoife; García-Muñoz, Ángel; Kohler, Johannes

2014-01-01

Background Refractive error is defined as the inability of the eye to bring parallel rays of light into focus on the retina, resulting in nearsightedness (myopia), farsightedness (Hyperopia) or astigmatism. Uncorrected refractive error in children is associated with increased morbidity and reduced educational opportunities. Vision screening (VS) is a method for identifying children with visual impairment or eye conditions likely to lead to visual impairment. Objective To analyze the utility of vision screening conducted by teachers and to contribute to a better estimation of the prevalence of childhood refractive errors in Apurimac, Peru. Design A pilot vision screening program in preschool (Group I) and elementary school children (Group II) was conducted with the participation of 26 trained teachers. Children whose visual acuity was<6/9 [20/30] (Group I) and≤6/9 (Group II) in one or both eyes, measured with the Snellen Tumbling E chart at 6 m, were referred for a comprehensive eye exam. Specificity and positive predictive value to detect refractive error were calculated against clinical examination. Program assessment with participants was conducted to evaluate outcomes and procedures. Results A total sample of 364 children aged 3–11 were screened; 45 children were examined at Centro Oftalmológico Monseñor Enrique Pelach (COMEP) Eye Hospital. Prevalence of refractive error was 6.2% (Group I) and 6.9% (Group II); specificity of teacher vision screening was 95.8% and 93.0%, while positive predictive value was 59.1% and 47.8% for each group, respectively. Aspects highlighted to improve the program included extending training, increasing parental involvement, and helping referred children to attend the hospital. Conclusion Prevalence of refractive error in children is significant in the region. Vision screening performed by trained teachers is a valid intervention for early detection of refractive error, including screening of preschool children. Program sustainability and improvements in education and quality of life resulting from childhood vision screening require further research. PMID:24560253

A variational regularization of Abel transform for GPS radio occultation

NASA Astrophysics Data System (ADS)

Wee, Tae-Kwon

2018-04-01

In the Global Positioning System (GPS) radio occultation (RO) technique, the inverse Abel transform of measured bending angle (Abel inversion, hereafter AI) is the standard means of deriving the refractivity. While concise and straightforward to apply, the AI accumulates and propagates the measurement error downward. The measurement error propagation is detrimental to the refractivity in lower altitudes. In particular, it builds up negative refractivity bias in the tropical lower troposphere. An alternative to AI is the numerical inversion of the forward Abel transform, which does not incur the integration of error-possessing measurement and thus precludes the error propagation. The variational regularization (VR) proposed in this study approximates the inversion of the forward Abel transform by an optimization problem in which the regularized solution describes the measurement as closely as possible within the measurement's considered accuracy. The optimization problem is then solved iteratively by means of the adjoint technique. VR is formulated with error covariance matrices, which permit a rigorous incorporation of prior information on measurement error characteristics and the solution's desired behavior into the regularization. VR holds the control variable in the measurement space to take advantage of the posterior height determination and to negate the measurement error due to the mismodeling of the refractional radius. The advantages of having the solution and the measurement in the same space are elaborated using a purposely corrupted synthetic sounding with a known true solution. The competency of VR relative to AI is validated with a large number of actual RO soundings. The comparison to nearby radiosonde observations shows that VR attains considerably smaller random and systematic errors compared to AI. A noteworthy finding is that in the heights and areas that the measurement bias is supposedly small, VR follows AI very closely in the mean refractivity deserting the first guess. In the lowest few kilometers that AI produces large negative refractivity bias, VR reduces the refractivity bias substantially with the aid of the background, which in this study is the operational forecasts of the European Centre for Medium-Range Weather Forecasts (ECMWF). It is concluded based on the results presented in this study that VR offers a definite advantage over AI in the quality of refractivity.

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

Relationship between lenticular power and refractive error in children with hyperopia.

PubMed

Tomomatsu, Takeshi; Kono, Shinjiro; Arimura, Shogo; Tomomatsu, Yoko; Matsumura, Takehiro; Takihara, Yuji; Inatani, Masaru; Takamura, Yoshihiro

2013-01-01

To evaluate the contribution of axial length, and lenticular and corneal power to the spherical equivalent refractive error in children with hyperopia between 3 and 13 years of age, using noncontact optical biometry. There were 62 children between 3 and 13 years of age with hyperopia (+2 diopters [D] or more) who underwent automated refraction measurement with cycloplegia, to measure spherical equivalent refractive error and corneal power. Axial length was measured using an optic biometer that does not require contact with the cornea. The refractive power of the lens was calculated using the Sanders-Retzlaff-Kraff formula. Single regression analysis was used to evaluate the correlation among the optical parameters. There was a significant positive correlation between age and axial length (P = 0.0014); however, the degree of hyperopia did not decrease with aging (P = 0.59). There was a significant negative correlation between age and the refractive power of the lens (P = 0.0001) but not that of the cornea (P = 0.43). A significant negative correlation was observed between the degree of hyperopia and lenticular power (P < 0.0001). Although this study is small scale and cross sectional, the analysis, using noncontact biometry, showed that lenticular power was negatively correlated with refractive error and age, indicating that lower lens power may contribute to the degree of hyperopia.

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.

Design and Validation of an Infrared Badal Optometer for Laser Speckle (IBOLS)

PubMed Central

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

2009-01-01

Purpose To validate the design of an infrared wavefront aberrometer with a Badal optometer employing the principle of laser speckle generated by a spinning disk and infrared light. The instrument was designed for subjective meridional refraction in infrared light by human patients. Methods Validation employed a model eye with known refractive error determined with an objective infrared wavefront aberrometer. The model eye was used to produce a speckle pattern on an artificial retina with controlled amounts of ametropia introduced with auxiliary ophthalmic lenses. A human observer performed the psychophysical task of observing the speckle pattern (with the aid of a video camera sensitive to infrared radiation) formed on the artificial retina. Refraction was performed by adjusting the vergence of incident light with the Badal optometer to nullify the motion of laser speckle. Validation of the method was performed for different levels of spherical ametropia and for various configurations of an astigmatic model eye. Results Subjective measurements of meridional refractive error over the range −4D to + 4D agreed with astigmatic refractive errors predicted by the power of the model eye in the meridian of motion of the spinning disk. Conclusions Use of a Badal optometer to control laser speckle is a valid method for determining subjective refractive error at infrared wavelengths. Such an instrument will be useful for comparing objective measures of refractive error obtained for the human eye with autorefractors and wavefront aberrometers that employ infrared radiation. PMID:18772719

Pre- and Postcycloplegic Refractions in Children and Adolescents

PubMed Central

Zhu, Dan; Wang, Yan; Yang, Xianrong; Yang, Dayong; Guo, Kai; Guo, Yuanyuan; Jing, Xinxia; Pan, Chen-Wei

2016-01-01

Purpose To determine the difference between cycloplegic and non-cycloplegic refractive error and its associated factors in Chinese children and adolescents with a high prevalence of myopia. Methods A school-based study including 1565 students aged 6 to 21 years was conducted in 2013 in Ejina, Inner Mongolia, China. Comprehensive eye examinations were performed. Pre-and postcycloplegic refractive error were measured using an auto-refractor. For cycloplegic refraction, one drop of topical 1.0% cyclopentolate was administered to each eye twice with a 5-minute interval and a third drop was administered 15 minutes after the second drop if the pupil size was less than 6 mm or if the pupillary light reflex was still present. Results Two drops of cyclopentolate were found to be sufficient in 59% of the study participants while the other 41% need an additional drop. The prevalence of myopia was 89.5% in participants aged over 12 years and 68.6% in those aged 12 years or younger (P<0.001). When myopia was defined as spherical equivalent (SE) of less than -0.5 diopter (D), the prevalence estimates were 76.7% (95% confidence interval [CI] 74.6–78.8) and 54.1% (95%CI 51.6–56.6) before and after cycloplegic refraction, respectively. When hyperopia was defined as SE of more than 0.5D, the prevalence was only 2.8% (95%CI 1.9–3.6) before cycloplegic refraction while it was 15.5% (95%CI 13.7–17.3) after cycloplegic refraction. Increased difference between cycloplegic and non-cycloplegic refractive error was associated with decreased intraocular pressures (P = 0.01). Conclusions Lack of cycloplegia in refractive error measurement was associated with significant misclassifications in both myopia and hyperopia among Chinese children and adolescents. Decreased intraocular pressure was related to a greater difference between cycloplegic and non-cycloplegic refractive error. PMID:27907165

Pre- and Postcycloplegic Refractions in Children and Adolescents.

PubMed

Zhu, Dan; Wang, Yan; Yang, Xianrong; Yang, Dayong; Guo, Kai; Guo, Yuanyuan; Jing, Xinxia; Pan, Chen-Wei

2016-01-01

To determine the difference between cycloplegic and non-cycloplegic refractive error and its associated factors in Chinese children and adolescents with a high prevalence of myopia. A school-based study including 1565 students aged 6 to 21 years was conducted in 2013 in Ejina, Inner Mongolia, China. Comprehensive eye examinations were performed. Pre-and postcycloplegic refractive error were measured using an auto-refractor. For cycloplegic refraction, one drop of topical 1.0% cyclopentolate was administered to each eye twice with a 5-minute interval and a third drop was administered 15 minutes after the second drop if the pupil size was less than 6 mm or if the pupillary light reflex was still present. Two drops of cyclopentolate were found to be sufficient in 59% of the study participants while the other 41% need an additional drop. The prevalence of myopia was 89.5% in participants aged over 12 years and 68.6% in those aged 12 years or younger (P<0.001). When myopia was defined as spherical equivalent (SE) of less than -0.5 diopter (D), the prevalence estimates were 76.7% (95% confidence interval [CI] 74.6-78.8) and 54.1% (95%CI 51.6-56.6) before and after cycloplegic refraction, respectively. When hyperopia was defined as SE of more than 0.5D, the prevalence was only 2.8% (95%CI 1.9-3.6) before cycloplegic refraction while it was 15.5% (95%CI 13.7-17.3) after cycloplegic refraction. Increased difference between cycloplegic and non-cycloplegic refractive error was associated with decreased intraocular pressures (P = 0.01). Lack of cycloplegia in refractive error measurement was associated with significant misclassifications in both myopia and hyperopia among Chinese children and adolescents. Decreased intraocular pressure was related to a greater difference between cycloplegic and non-cycloplegic refractive error.

Linkage Analysis of Quantitative Refraction and Refractive Errors in the Beaver Dam Eye Study

PubMed Central

Duggal, Priya; Lee, Kristine E.; Cheng, Ching-Yu; Klein, Ronald; Bailey-Wilson, Joan E.; Klein, Barbara E. K.

2011-01-01

Purpose. Refraction, as measured by spherical equivalent, is the need for an external lens to focus images on the retina. While genetic factors play an important role in the development of refractive errors, few susceptibility genes have been identified. However, several regions of linkage have been reported for myopia (2q, 4q, 7q, 12q, 17q, 18p, 22q, and Xq) and for quantitative refraction (1p, 3q, 4q, 7p, 8p, and 11p). To replicate previously identified linkage peaks and to identify novel loci that influence quantitative refraction and refractive errors, linkage analysis of spherical equivalent, myopia, and hyperopia in the Beaver Dam Eye Study was performed. Methods. Nonparametric, sibling-pair, genome-wide linkage analyses of refraction (spherical equivalent adjusted for age, education, and nuclear sclerosis), myopia and hyperopia in 834 sibling pairs within 486 extended pedigrees were performed. Results. Suggestive evidence of linkage was found for hyperopia on chromosome 3, region q26 (empiric P = 5.34 × 10−4), a region that had shown significant genome-wide evidence of linkage to refraction and some evidence of linkage to hyperopia. In addition, the analysis replicated previously reported genome-wide significant linkages to 22q11 of adjusted refraction and myopia (empiric P = 4.43 × 10−3 and 1.48 × 10−3, respectively) and to 7p15 of refraction (empiric P = 9.43 × 10−4). Evidence was also found of linkage to refraction on 7q36 (empiric P = 2.32 × 10−3), a region previously linked to high myopia. Conclusions. The findings provide further evidence that genes controlling refractive errors are located on 3q26, 7p15, 7p36, and 22q11. PMID:21571680

Refractive errors in low-income preschoolers.

PubMed

Brody, Barbara L; Roch-Levecq, Anne-Catherine; Klonoff-Cohen, Hillary S; Brown, Stuart I

2007-01-01

To estimate the overall prevalence of refractive errors in a study population of low-income preschoolers in San Diego County. The study sample included 507 preschool children selected from a study population of all 3-5 year-old children in Head Start and San Diego Unified School District preschools (74% Latino). The sample was examined by optometrists in the mobile clinic of the University of California, San Diego, Department of Ophthalmology with retinoscopy under cycloplegia to assess the presence of refractive errors defined as myopia >or=2D in 3-4 year-olds and >or=1D in > 4 year-olds; hyperopia >or=4D in 3-4 year-olds and >or=3D in > 4 year-olds; and astigmatism >or=1.75D in 3-4 year-olds and >or=1.5D in > 4 year-olds. Anisometropia was defined as >or=1.25D difference between the eyes. Emmetropia was defined as refractive errors below these levels. A total of 16% (n = 81 children) (95% confidence interval: 15.4-16.5) met study definitions of refractive errors in at least one eye. Myopia was found in 3%, (OD Mean Sphere = 2.4D); hyperopia in 7.5% (OD Mean Sphere = 3.8D); astigmatism in 5.5% (OD Mean Cylinder = 2.3D); and 84% were emmetropic (OD Mean Sphere = 1.3D). Hyperopia and astigmatism were the most frequent refractive errors in this sample of low-income preschoolers, most of whom were Latino.

Decision support system for determining the contact lens for refractive errors patients with classification ID3

NASA Astrophysics Data System (ADS)

Situmorang, B. H.; Setiawan, M. P.; Tosida, E. T.

2017-01-01

Refractive errors are abnormalities of the refraction of light so that the shadows do not focus precisely on the retina resulting in blurred vision [1]. Refractive errors causing the patient should wear glasses or contact lenses in order eyesight returned to normal. The use of glasses or contact lenses in a person will be different from others, it is influenced by patient age, the amount of tear production, vision prescription, and astigmatic. Because the eye is one organ of the human body is very important to see, then the accuracy in determining glasses or contact lenses which will be used is required. This research aims to develop a decision support system that can produce output on the right contact lenses for refractive errors patients with a value of 100% accuracy. Iterative Dichotomize Three (ID3) classification methods will generate gain and entropy values of attributes that include code sample data, age of the patient, astigmatic, the ratio of tear production, vision prescription, and classes that will affect the outcome of the decision tree. The eye specialist test result for the training data obtained the accuracy rate of 96.7% and an error rate of 3.3%, the result test using confusion matrix obtained the accuracy rate of 96.1% and an error rate of 3.1%; for the data testing obtained accuracy rate of 100% and an error rate of 0.

Refractive error in school children in an urban and rural setting in Cambodia.

PubMed

Gao, Zoe; Meng, Ngy; Muecke, James; Chan, Weng Onn; Piseth, Horm; Kong, Aimee; Jnguyenphamhh, Theresa; Dehghan, Yalda; Selva, Dinesh; Casson, Robert; Ang, Kim

2012-02-01

To assess the prevalence of refractive error in schoolchildren aged 12-14 years in urban and rural settings in Cambodia's Phnom Penh and Kandal provinces. Ten schools from Phnom Penh Province and 26 schools from Kandal Province were randomly selected and surveyed in October 2010. Children were examined by teams of Australian and Cambodian optometrists, ophthalmic nurses and ophthalmologists who performed visual acuity (VA) testing and cycloplegic refraction. A total of 5527 children were included in the study. The prevalence of uncorrected, presenting and best-corrected VA ≤ 6/12 in the better eye were 2.48% (95% confidence interval [CI] 2.02-2.83%), 1.90% (95% CI 1.52-2.24%) and 0.36% (95% CI 0.20-0.52%), respectively; 43 children presented with glasses whilst a total of 315 glasses were dispensed. The total prevalence of refractive error was 6.57% (95% CI 5.91-7.22%), but there was a significant difference between urban (13.7%, 95% CI 12.2-15.2%) and rural (2.5%, 95% CI 2.03-3.07%) schools (P < 0.0001). Refractive error accounted for 91.2% of visually impaired eyes, cataract for 1.7%, and other causes for 7.1%. Myopia (spherical equivalent ≤ -0.50 diopters [D] in either eye) was associated with increased age, female gender and urban schooling. The prevalence of refractive error was significantly higher in urban Phnom Penh schools than rural schools in Kandal Province. The prevalence of refractive error, particularly myopia was relatively low compared to previous reports in Asia. The majority of children did not have appropriate correction with spectacles, highlighting the need for more effective screening and optical intervention.

Frequency and Distribution of Refractive Error in Adult Life: Methodology and Findings of the UK Biobank Study

PubMed Central

Cumberland, Phillippa M.; Bao, Yanchun; Hysi, Pirro G.; Foster, Paul J.; Hammond, Christopher J.; Rahi, Jugnoo S.

2015-01-01

Purpose To report the methodology and findings of a large scale investigation of burden and distribution of refractive error, from a contemporary and ethnically diverse study of health and disease in adults, in the UK. Methods U K Biobank, a unique contemporary resource for the study of health and disease, recruited more than half a million people aged 40–69 years. A subsample of 107,452 subjects undertook an enhanced ophthalmic examination which provided autorefraction data (a measure of refractive error). Refractive error status was categorised using the mean spherical equivalent refraction measure. Information on socio-demographic factors (age, gender, ethnicity, educational qualifications and accommodation tenure) was reported at the time of recruitment by questionnaire and face-to-face interview. Results Fifty four percent of participants aged 40–69 years had refractive error. Specifically 27% had myopia (4% high myopia), which was more common amongst younger people, those of higher socio-economic status, higher educational attainment, or of White or Chinese ethnicity. The frequency of hypermetropia increased with age (7% at 40–44 years increasing to 46% at 65–69 years), was higher in women and its severity was associated with ethnicity (moderate or high hypermetropia at least 30% less likely in non-White ethnic groups compared to White). Conclusions Refractive error is a significant public health issue for the UK and this study provides contemporary data on adults for planning services, health economic modelling and monitoring of secular trends. Further investigation of risk factors is necessary to inform strategies for prevention. There is scope to do this through the planned longitudinal extension of the UK Biobank study. PMID:26430771

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.

Individual set-point and gain of emmetropization in chickens.

PubMed

Tepelus, Tudor Cosmin; Schaeffel, Frank

2010-01-01

During the developmental process of emmetropization evidence shows that visual feedback guides the eye as it approaches a refractive state close to zero, or slightly hyperopic. How this "set-point" is internally defined, in the presence of continuous shifts of the focal plane with different viewing distances and accommodation, remains unclear. Minimizing defocus blur over time should produce similar end-point refractions in different individuals. However, we found that individual chickens display considerable variability in their set-point refractive states, despite that they all had the same visual experience. This variability is not random since the refractions in both eyes were highly correlated - even though it is known that they can emmetropize independently. Furthermore, if chicks underwent a period of experimentally induced ametropia, they returned to their individual set-point refractions during recovery (correlation of the refractions before treatment versus after recovery: n=19 chicks, 38 eyes, left eyes: slope 1.01, R=0.860; right eyes: slope 0.85, R=0.610, p<0.001, linear regression). Also, the induced deprivation myopia was correlated in both eyes (n=18 chicks, 36 eyes, p<0.01, orthogonal regression). If chicks were treated with spectacle lenses, the compensatory changes in refraction were, on average, appropriate but individual chicks displayed variable responses. Again, the refractions of both eyes remained correlated (negative lenses, n=18 chicks, 36 eyes, slope 0.89, R=0.504, p<0.01, positive lenses: n=21 chicks, 42 eyes, slope 1.14, R=0.791, p<0.001). The amount of deprivation myopia that developed in two successive treatment cycles, with an intermittent period of recovery, was not correlated; only vitreous chamber growth was almost significantly correlated in both cycles (n=7 chicks, 14 eyes; p<0.05). The amounts of ametropia and vitreous chamber changes induced in two successive cycles of treatment, first with lenses and then with diffusers, were also not correlated, suggesting that the "gains of lens compensation" are different from those in deprivation myopia. In summary, (1) there appears to be an endogenous, possibly genetic, definition of the set-point of emmetropization in each individual, which is similar in both eyes, (2) visual conditions that induce ametropia produce variable changes in refractions, with high correlations between both eyes, (3) overall, the "gain of emmetropization" appears only weakly controlled by endogenous factors.

Influence of Ametropia and Its Correction on Measurement of Accommodation.

PubMed

Bernal-Molina, Paula; Vargas-Martín, Fernando; Thibos, Larry N; López-Gil, Norberto

2016-06-01

Amplitude of accommodation (AA) is reportedly greater for myopic eyes than for hyperopic eyes. We investigated potential explanations for this difference. Analytical analysis and computer ray tracing were performed on two schematic eye models of axial ametropia. Using paraxial and nonparaxial approaches, AA was specified for the naked and the corrected eye using the anterior corneal surface as the reference plane. Assuming that axial myopia is due entirely to an increase in vitreous chamber depth, AA increases with the amount of myopia for two reasons that have not always been taken into account. First is the choice of reference location for specifying refractive error and AA in diopters. When specified relative to the cornea, AA increases with the degree of myopia more than when specified relative to the eye's first Gaussian principal plane. The second factor is movement of the eye's second Gaussian principal plane toward the retina during accommodation, which has a larger dioptric effect in shorter eyes. Using the corneal plane (placed at the corneal vertex) as the reference plane for specifying accommodation, AA depends slightly on the axial length of the eye's vitreous chamber. This dependency can be reduced significantly by using a reference plane located 4 mm posterior to the corneal plane. A simple formula is provided to help clinicians and researchers obtain a value of AA that closely reflects power changes of the crystalline lens, independent of axial ametropia and its correction with lenses.

Refractive errors in patients with newly diagnosed diabetes mellitus.

PubMed

Yarbağ, Abdülhekim; Yazar, Hayrullah; Akdoğan, Mehmet; Pekgör, Ahmet; Kaleli, Suleyman

2015-01-01

Diabetes mellitus is a complex metabolic disorder that involves the small blood vessels, often causing widespread damage to tissues, including the eyes' optic refractive error. In patients with newly diagnosed diabetes mellitus who have unstable blood glucose levels, refraction may be incorrect. We aimed to investigate refraction in patients who were recently diagnosed with diabetes and treated at our centre. This prospective study was performed from February 2013 to January 2014. Patients were diagnosed with diabetes mellitus using laboratory biochemical tests and clinical examination. Venous fasting plasma glucose (fpg) levels were measured along with refractive errors. Two measurements were taken: initially and after four weeks. The last difference between the initial and end refractive measurements were evaluated. Our patients were 100 males and 30 females who had been newly diagnosed with type II DM. The refractive and fpg levels were measured twice in all patients. The average values of the initial measurements were as follows: fpg level, 415 mg/dl; average refractive value, +2.5 D (Dioptres). The average end of period measurements were fpg, 203 mg/dl; average refractive value, +0.75 D. There is a statistically significant difference between after four weeks measurements with initially measurements of fasting plasma glucose (fpg) levels (p<0.05) and there is a statistically significant relationship between changes in fpg changes with glasses ID (p<0.05) and the disappearance of blurred vision (to be greater than 50% success rate) were statistically significant (p<0.05). Also, were detected upon all these results the absence of any age and sex effects (p>0.05). Refractive error is affected in patients with newly diagnosed diabetes mellitus; therefore, plasma glucose levels should be considered in the selection of glasses.

Effects of light refraction on the accuracy of camera calibration and reconstruction in underwater motion analysis.

PubMed

Kwon, Young-Hoo; Casebolt, Jeffrey B

2006-01-01

One of the most serious obstacles to accurate quantification of the underwater motion of a swimmer's body is image deformation caused by refraction. Refraction occurs at the water-air interface plane (glass) owing to the density difference. Camera calibration-reconstruction algorithms commonly used in aquatic research do not have the capability to correct this refraction-induced nonlinear image deformation and produce large reconstruction errors. The aim of this paper is to provide a through review of: the nature of the refraction-induced image deformation and its behaviour in underwater object-space plane reconstruction; the intrinsic shortcomings of the Direct Linear Transformation (DLT) method in underwater motion analysis; experimental conditions that interact with refraction; and alternative algorithms and strategies that can be used to improve the calibration-reconstruction accuracy. Although it is impossible to remove the refraction error completely in conventional camera calibration-reconstruction methods, it is possible to improve the accuracy to some extent by manipulating experimental conditions or calibration frame characteristics. Alternative algorithms, such as the localized DLT and the double-plane method are also available for error reduction. The ultimate solution for the refraction problem is to develop underwater camera calibration and reconstruction algorithms that have the capability to correct refraction.

Effects of light refraction on the accuracy of camera calibration and reconstruction in underwater motion analysis.

PubMed

Kwon, Young-Hoo; Casebolt, Jeffrey B

2006-07-01

One of the most serious obstacles to accurate quantification of the underwater motion of a swimmer's body is image deformation caused by refraction. Refraction occurs at the water-air interface plane (glass) owing to the density difference. Camera calibration-reconstruction algorithms commonly used in aquatic research do not have the capability to correct this refraction-induced nonlinear image deformation and produce large reconstruction errors. The aim of this paper is to provide a thorough review of: the nature of the refraction-induced image deformation and its behaviour in underwater object-space plane reconstruction; the intrinsic shortcomings of the Direct Linear Transformation (DLT) method in underwater motion analysis; experimental conditions that interact with refraction; and alternative algorithms and strategies that can be used to improve the calibration-reconstruction accuracy. Although it is impossible to remove the refraction error completely in conventional camera calibration-reconstruction methods, it is possible to improve the accuracy to some extent by manipulating experimental conditions or calibration frame characteristics. Alternative algorithms, such as the localized DLT and the double-plane method are also available for error reduction. The ultimate solution for the refraction problem is to develop underwater camera calibration and reconstruction algorithms that have the capability to correct refraction.

Statistics of the residual refraction errors in laser ranging data

NASA Technical Reports Server (NTRS)

Gardner, C. S.

1977-01-01

A theoretical model for the range error covariance was derived by assuming that the residual refraction errors are due entirely to errors in the meteorological data which are used to calculate the atmospheric correction. The properties of the covariance function are illustrated by evaluating the theoretical model for the special case of a dense network of weather stations uniformly distributed within a circle.

Refractive Error and Visual Functions in Children with Special Needs Compared with the First Grade School Students in Oman

PubMed Central

Vora, Urmi; Khandekar, Rajiv; Natrajan, Sarvanan; Al-Hadrami, Khalfan

2010-01-01

Background: We evaluated the refractive status and visual function of children with special needs (other handicap) in 2010 and compared them with healthy 1st grade school students in Oman. Materials and Methods: This was a cohort study. Optometrists recorded vision using a logarithm of minimum angle of resolution (LogMAR) chart. Preferential looking method was used for testing 31 children. Cycloplegic refraction was performed on all children. Contrast sensitivity was tested using 2.5%, 10%, and 100% contrast charts. Ocular movement, alignment, and anterior segment were also assessed. A pediatrician reviewed the health records of all the children at the time of their enrollment in this study to determine if the child had been diagnosed with a systemic condition or syndromes. The visual functions were assessed by study investigators. We estimated the rates and the risk of different visual function defects in children with special needs. Result: The prevalence of refractive error in 70 children (4.7 ± 0.8 years) with special needs (group 1) and 175 normal healthy first grade students (group 2) were 58.5% and 2.9%, respectively. The risk of refractive error was significantly higher in children with special needs [relative risk, 48.1 (95% confidence interval, 17.54–131.8)]. Hyperopia (>1.00 D), myopia (≥ 1.00D) and astigmatism (≥ ±1.00 D) were found in 18.6%, 24.3%, and 27.1%, respectively, in group 1. Six children in this group had defective near vision. Sixteen (80%) children with Down syndrome had refractive error. Seven (50%) children with developmental disorder showed decreased contrast sensitivity. Conclusion: Prevalence of uncorrected refractive error was much higher in children with special needs. Prevalence of strabismus, nystagmus, and reduced contrast sensitivity was also higher in children with special needs. Early vision screening, visual function assessment, correction of refractive error, and frequent follow-up are recommended. PMID:21180428

Peripheral refraction profiles in subjects with low foveal refractive errors.

PubMed

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

2011-03-01

To study the variability of peripheral refraction in a population of 43 subjects with low foveal refractive errors. A scan of the refractive error in the vertical pupil meridian of the right eye of 43 subjects (age range, 18 to 80 years, foveal spherical equivalent, < ± 2.5 diopter) over the central ± 45° of the visual field was performed using a recently developed angular scanning photorefractor. Refraction profiles across the visual field were fitted with four different models: (1) "flat model" (refractions about constant across the visual field), (2) "parabolic model" (refractions follow about a parabolic function), (3) "bi-linear model" (linear change of refractions with eccentricity from the fovea to the periphery), and (4) "box model" ("flat" central area with a linear change in refraction from a certain peripheral angle). Based on the minimal residuals of each fit, the subjects were classified into one of the four models. The "box model" accurately described the peripheral refractions in about 50% of the subjects. Peripheral refractions in six subjects were better characterized by a "linear model," in eight subjects by a "flat model," and in eight by the "parabolic model." Even after assignment to one of the models, the variability remained strikingly large, ranging from -0.75 to 6 diopter in the temporal retina at 45° eccentricity. The most common peripheral refraction profile (observed in nearly 50% of our population) was best described by the "box model." The high variability among subjects may limit attempts to reduce myopia progression with a uniform lens design and may rather call for a customized approach.

The ipRGC-Driven Pupil Response with Light Exposure, Refractive Error, and Sleep.

PubMed

Abbott, Kaleb S; Queener, Hope M; Ostrin, Lisa A

2018-04-01

We investigated links between the intrinsically photosensitive retinal ganglion cells, light exposure, refractive error, and sleep. Results showed that morning melatonin was associated with light exposure, with modest differences in sleep quality between myopes and emmetropes. Findings suggest a complex relationship between light exposure and these physiological processes. Intrinsically photosensitive retinal ganglion cells (ipRGCs) signal environmental light, with pathways to the midbrain to control pupil size and circadian rhythm. Evidence suggests that light exposure plays a role in refractive error development. Our goal was to investigate links between light exposure, ipRGCs, refractive error, and sleep. Fifty subjects, aged 17-40, participated (19 emmetropes and 31 myopes). A subset of subjects (n = 24) wore an Actiwatch Spectrum for 1 week. The Pittsburgh Sleep Quality Index (PSQI) was administered, and saliva samples were collected for melatonin analysis. The post-illumination pupil response (PIPR) to 1 s and 5 s long- and short-wavelength stimuli was measured. Pupil metrics included the 6 s and 30 s PIPR and early and late area under the curve. Subjects spent 104.8 ± 46.6 min outdoors per day over the previous week. Morning melatonin concentration (6.9 ± 3.5 pg/ml) was significantly associated with time outdoors and objectively measured light exposure (P = .01 and .002, respectively). Pupil metrics were not significantly associated with light exposure or refractive error. PSQI scores indicated good sleep quality for emmetropes (score 4.2 ± 2.3) and poor sleep quality for myopes (5.6 ± 2.2, P = .04). We found that light exposure and time outdoors influenced morning melatonin concentration. No differences in melatonin or the ipRGC-driven pupil response were observed between refractive error groups, although myopes exhibited poor sleep quality compared to emmetropes. Findings suggest that a complex relationship between light exposure, ipRGCs, refractive error, and sleep exists.

Investigating the relationship between foveal morphology and refractive error in a population with infantile nystagmus syndrome.

PubMed

Healey, Natasha; McLoone, Eibhlin; Mahon, Gerald; Jackson, A Jonathan; Saunders, Kathryn J; McClelland, Julie F

2013-04-26

We explored associations between refractive error and foveal hypoplasia in infantile nystagmus syndrome (INS). We recruited 50 participants with INS (albinism n = 33, nonalbinism infantile nystagmus [NAIN] n = 17) aged 4 to 48 years. Cycloplegic refractive error and logMAR acuity were obtained. Spherical equivalent (SER), most ametropic meridian (MAM) refractive error, and better eye acuity (VA) were used for analyses. High resolution spectral-domain optical coherence tomography (SD-OCT) was used to obtain foveal scans, which were graded using the Foveal Hypoplasia Grading Scale. Associations between grades of severity of foveal hypoplasia, and refractive error and VA were explored. Participants with more severe foveal hypoplasia had significantly higher MAMs and SERs (Kruskal-Wallis H test P = 0.005 and P = 0.008, respectively). There were no statistically significant associations between foveal hypoplasia and cylindrical refractive error (Kruskal-Wallis H test P = 0.144). Analyses demonstrated significant differences between participants with albinism or NAIN in terms of SER and MAM (Mann-Whitney U test P = 0.001). There were no statistically significant differences between astigmatic errors between participants with albinism and NAIN. Controlling for the effects of albinism, results demonstrated no significant associations between SER, and MAM and foveal hypoplasia (partial correlation P > 0.05). Poorer visual acuity was associated statistically significantly with more severe foveal hypoplasia (Kruskal-Wallis H test P = 0.001) and with a diagnosis of albinism (Mann-Whitney U test P = 0.001). Increasing severity of foveal hypoplasia is associated with poorer VA, reflecting reduced cone density in INS. Individuals with INS also demonstrate a significant association between more severe foveal hypoplasia and increasing hyperopia. However, in the absence of albinism, there is no significant relation between refractive outcome and degree of foveal hypoplasia, suggesting that foveal maldevelopment in isolation does not impair significantly the emmetropization process. It likely is that impaired emmetropization evidenced in the albinism group may be attributed to the whole eye effect of albinism.

Refractive errors in medical students in Singapore.

PubMed

Woo, W W; Lim, K A; Yang, H; Lim, X Y; Liew, F; Lee, Y S; Saw, S M

2004-10-01

Refractive errors are becoming more of a problem in many societies, with prevalence rates of myopia in many Asian urban countries reaching epidemic proportions. This study aims to determine the prevalence rates of various refractive errors in Singapore medical students. 157 second year medical students (aged 19-23 years) in Singapore were examined. Refractive error measurements were determined using a stand-alone autorefractor. Additional demographical data was obtained via questionnaires filled in by the students. The prevalence rate of myopia in Singapore medical students was 89.8 percent (Spherical equivalence (SE) at least -0.50 D). Hyperopia was present in 1.3 percent (SE more than +0.50 D) of the participants and the overall astigmatism prevalence rate was 82.2 percent (Cylinder at least 0.50 D). Prevalence rates of myopia and astigmatism in second year Singapore medical students are one of the highest in the world.

Peripheral refractive correction and automated perimetric profiles.

PubMed

Wild, J M; Wood, J M; Crews, S J

1988-06-01

The effect of peripheral refractive error correction on the automated perimetric sensitivity profile was investigated on a sample of 10 clinically normal, experienced observers. Peripheral refractive error was determined at eccentricities of 0 degree, 20 degrees and 40 degrees along the temporal meridian of the right eye using the Canon Autoref R-1, an infra-red automated refractor, under the parametric conditions of the Octopus automated perimeter. Perimetric sensitivity was then undertaken at these eccentricities (stimulus sizes 0 and III) with and without the appropriate peripheral refractive correction using the Octopus 201 automated perimeter. Within the measurement limits of the experimental procedures employed, perimetric sensitivity was not influenced by peripheral refractive correction.

From unseen to seen: tackling the global burden of uncorrected refractive errors.

PubMed

Durr, Nicholas J; Dave, Shivang R; Lage, Eduardo; Marcos, Susana; Thorn, Frank; Lim, Daryl

2014-07-11

Worldwide, more than one billion people suffer from poor vision because they do not have the eyeglasses they need. Their uncorrected refractive errors are a major cause of global disability and drastically reduce productivity, educational opportunities, and overall quality of life. The problem persists most prevalently in low-resource settings, even though prescription eyeglasses serve as a simple, effective, and largely affordable solution. In this review, we discuss barriers to obtaining, and approaches for providing, refractive eye care. We also highlight emerging technologies that are being developed to increase the accessibility of eye care. Finally, we describe opportunities that exist for engineers to develop new solutions to positively impact the diagnosis and treatment of correctable refractive errors in low-resource settings.

Relationship between lenticular power and refractive error in children with hyperopia

PubMed Central

Tomomatsu, Takeshi; Kono, Shinjiro; Arimura, Shogo; Tomomatsu, Yoko; Matsumura, Takehiro; Takihara, Yuji; Inatani, Masaru; Takamura, Yoshihiro

2013-01-01

Objectives To evaluate the contribution of axial length, and lenticular and corneal power to the spherical equivalent refractive error in children with hyperopia between 3 and 13 years of age, using noncontact optical biometry. Methods There were 62 children between 3 and 13 years of age with hyperopia (+2 diopters [D] or more) who underwent automated refraction measurement with cycloplegia, to measure spherical equivalent refractive error and corneal power. Axial length was measured using an optic biometer that does not require contact with the cornea. The refractive power of the lens was calculated using the Sanders-Retzlaff-Kraff formula. Single regression analysis was used to evaluate the correlation among the optical parameters. Results There was a significant positive correlation between age and axial length (P = 0.0014); however, the degree of hyperopia did not decrease with aging (P = 0.59). There was a significant negative correlation between age and the refractive power of the lens (P = 0.0001) but not that of the cornea (P = 0.43). A significant negative correlation was observed between the degree of hyperopia and lenticular power (P < 0.0001). Conclusion Although this study is small scale and cross sectional, the analysis, using noncontact biometry, showed that lenticular power was negatively correlated with refractive error and age, indicating that lower lens power may contribute to the degree of hyperopia. PMID:23576859

Prevalence of refractive errors in Tibetan adolescents.

PubMed

Qian, Xuehan; Liu, Beihong; Wang, Jing; Wei, Nan; Qi, Xiaoli; Li, Xue; Li, Jing; Zhang, Ying; Hua, Ning; Ning, Yuxian; Ding, Gang; Ma, Xu; Wang, Binbin

2018-05-11

The prevalence of adolescent eye disease in remote areas of the Qinghai-Tibet Plateau has rarely been reported. To understand the prevalence of common eye diseases in Tibet, we performed ocular-disease screening on students from primary and secondary schools in Tibet, and compared the prevalence to that in the Central China Plain (referred to here as the "plains area"). The refractive status of students was evaluated with a Spot™ vision screener. The test was conducted three or fewer times for both eyes of each student and results with best correction were recorded. A total of 3246 students from primary and secondary schools in the Tibet Naidong district were screened, yielding a refractive error rate of 28.51%, which was significantly lower than that of the plains group (28.51% vs. 56.92%, p < 0.001). In both groups, the prevalence of refractive errors among females was higher than that among males. We found that Tibetan adolescents had a lower prevalence of refractive errors than did adolescents in the plains area, which may be related to less intensive schooling and greater exposure to sunlight.

Ocular manifestations of sickle cell disease and genetic susceptibility for refractive errors

PubMed Central

Shukla, Palak; Verma, Henu; Patel, Santosh; Patra, P. K.; Bhaskar, L. V. K. S.

2017-01-01

PURPOSE: Sickle cell disease (SCD) is the most common and serious form of an inherited blood disorder that lead to higher risk of early mortality. SCD patients are at high risk for developing multiorgan acute and chronic complications linked with significant morbidity and mortality. Some of the ophthalmological complications of SCD include retinal changes, refractive errors, vitreous hemorrhage, and abnormalities of the cornea. MATERIALS AND METHODS: The present study includes 96 SCD patients. A dilated comprehensive eye examination was performed to know the status of retinopathy. Refractive errors were measured in all patients. In patients with >10 years of age, cycloplegia was not performed before autorefractometry. A subset of fifty patients’ genotyping was done for NOS3 27-base pair (bp) variable number of tandem repeat (VNTR) and IL4 intron-3 VNTR polymorphisms using polymerase chain reaction-electrophoresis. Chi-square test was performed to test the association between the polymorphisms and refractive errors. RESULTS: The results of the present study revealed that 63.5% of patients have myopia followed by 19.8% hyperopia. NOS3 27-bp VNTR genotypes significantly deviated from Hardy–Weinberg equilibrium (P < 0.0001). Although IL4 70-bp VNTR increased the risk of developing refractive errors, it is not statistically significant. However, NOS3 27-bp VNTR significantly reduced the risk of development of myopia. CONCLUSION: In summary, our study documents the prevalence of refractive errors along with some retinal changes in Indian SCD patients. Further, this study demonstrates that the NOS3 VNTR contributes to the susceptibility to development of myopia in SCD cases. PMID:29018763

Increased Incidence of Visual Field Abnormalities as Determined by Frequency Doubling Technology Perimetry in High Computer Users Among Japanese Workers: A Retrospective Cohort Study.

PubMed

Nakano, Tadashi; Hayashi, Takeshi; Nakagawa, Toru; Honda, Toru; Owada, Satoshi; Endo, Hitoshi; Tatemichi, Masayuki

2018-04-05

This retrospective cohort study primarily aimed to investigate the possible association of computer use with visual field abnormalities (VFA) among Japanese workers. The study included 2,377 workers (mean age 45.7 [standard deviation, 8.3] years; 2,229 men and 148 women) who initially exhibited no VFA during frequency doubling technology perimetry (FDT) testing. Subjects then underwent annual follow-up FDT testing for 7 years, and VFA were determined using a FDT-test protocol (FDT-VFA). Subjects with FDT-VFA were examined by ophthalmologists. Baseline data about the mean duration of computer use during a 5-year period and refractive errors were obtained via self-administered questionnaire and evaluations for refractive errors (use of eyeglasses or contact lenses), respectively. A Cox proportional hazard analysis demonstrated that heavy computer users (>8 hr/day) had a significantly increased risk of FDT-VFA (hazard ratio [HR] 2.85; 95% confidence interval [CI], 1.26-6.48) relative to light users (<4 hr/day), and this association was strengthened among subjects with refractive errors (HR 4.48; 95% CI, 1.87-10.74). The computer usage history also significantly correlated with FDT-VFA among subject with refractive errors (P < 0.05), and 73.1% of subjects with FDT-VFA and refractive errors were diagnosed with glaucoma or ocular hypertension. The incidence of FDT-VFA appears to be increased among Japanese workers who are heavy computer users, particularly if they have refractive errors. Further investigations of epidemiology and causality are warranted.

Ocular manifestations of sickle cell disease and genetic susceptibility for refractive errors.

PubMed

Shukla, Palak; Verma, Henu; Patel, Santosh; Patra, P K; Bhaskar, L V K S

2017-01-01

Sickle cell disease (SCD) is the most common and serious form of an inherited blood disorder that lead to higher risk of early mortality. SCD patients are at high risk for developing multiorgan acute and chronic complications linked with significant morbidity and mortality. Some of the ophthalmological complications of SCD include retinal changes, refractive errors, vitreous hemorrhage, and abnormalities of the cornea. The present study includes 96 SCD patients. A dilated comprehensive eye examination was performed to know the status of retinopathy. Refractive errors were measured in all patients. In patients with >10 years of age, cycloplegia was not performed before autorefractometry. A subset of fifty patients' genotyping was done for NOS3 27-base pair (bp) variable number of tandem repeat (VNTR) and IL4 intron-3 VNTR polymorphisms using polymerase chain reaction-electrophoresis. Chi-square test was performed to test the association between the polymorphisms and refractive errors. The results of the present study revealed that 63.5% of patients have myopia followed by 19.8% hyperopia. NOS3 27-bp VNTR genotypes significantly deviated from Hardy-Weinberg equilibrium ( P < 0.0001). Although IL4 70-bp VNTR increased the risk of developing refractive errors, it is not statistically significant. However, NOS3 27-bp VNTR significantly reduced the risk of development of myopia. In summary, our study documents the prevalence of refractive errors along with some retinal changes in Indian SCD patients. Further, this study demonstrates that the NOS3 VNTR contributes to the susceptibility to development of myopia in SCD cases.

[Determining factors for deciding whether or not to treat refractive errors and cataract in people with a learning disability].

PubMed

van Isterdael, C E D; Stilma, J S; Bezemer, P D; Tijmes, N T

2008-05-03

A study into the treatment of refractive errors and cataract in a selected population with learning disabilities. Design. Retrospective. In the years 1993-2003, 5205 people (mean age: 39 years) were referred to the visual advisory centre of Bartiméus (one of three institutes for the visually impaired in the Netherlands) by learning disability physicians and were assessed ophthalmologically. This assessment consisted of a measurement of visual acuity and refractive error, slitlamp examination and retinoscopy, and was performed at the client's accommodation. Advised treatment for spectacle prescriptions and referral for cataract surgery were registered. Refractive errors were found in 35% (1845/5205) of the patients with learning disabilities; 49% (905/1845) already wore spectacles; another 14% (265/1845) were prescribed spectacles for the first time. Of those with presbyopia, 12% (232/1865) had reading glasses and 10% (181/1865) were given a first prescription for spectacles. The most important determinant for not prescribing spectacles was: presence of severe learning disability (odds ratio (OR): 3.7). Cataract was present in 10% (497/5205) of the population; 399 patients were advised to be referred for surgery, 55% (219/399) were referred ofwhom 26% (57/219) had surgery. Moderately severe bilateral cataract was the only determinant of cataract surgery (OR: 7.8). Refractive errors and cataract were not always treated in this group. One of the reasons for non-treatment of refractive errors was a severe learning disability. The reason for treatment or non-treatment in patients with cataract was less clear.

Keratorefractive procedures

NASA Astrophysics Data System (ADS)

Seiler, Theo

1991-11-01

Two laser types are going to find a place in refractive surgery of the cornea: the excimer laser (193 nm) and mid-infrared YAG lasers, such as Ho:YAG (2.1 micrometers ) and Er:YAG (2.94 micrometers ). Whereas the excimer laser used for photorefractive keratectomy (PRK) and phototherapeutic keratectomy (PTK) is currently studied in clinical trials, Ho:YAG and Er:YAG lasers are still in the state of preclinical evaluation. For myopic corrections excimer laser PRK has shown to be safe and effective in the range up to -7.0 D. The results compare favorably with conventional procedures such as radial keratotomy. Complications are rare. Hyperopic and astigmatic corrections using the Ho:YAG laser (HOT) are effective, but safety and stability has yet to be proven. Er:YAG laser photoablation yields a healing response in animal eyes similar to the excimer laser.

Trends in refractive surgery at an academic center: 2007-2009.

PubMed

Kuo, Irene C

2011-05-14

The United States officially entered a recession in December 2007, and it officially exited the recession in December 2009, according to the National Bureau of Economic Research. Since the economy may affect not only the volume of excimer laser refractive surgery, but also the clinical characteristics of patients undergoing surgery, our goal was to compare the characteristics of patients completing excimer laser refractive surgery and the types of procedures performed in the summer quarter in 2007 and the same quarter in 2009 at an academic center. A secondary goal was to determine whether the volume of astigmatism- or presbyopia-correcting intraocular lenses (IOLs) has concurrently changed because like laser refractive surgery, these "premium" IOLs involve out-of-pocket costs for patients. Retrospective case series. Medical records were reviewed for all patients completing surgery at the Wilmer Laser Vision Center in the summer quarter of 2007 and the summer quarter of 2009. Outcome measures were the proportions of treated refractive errors, the proportion of photorefractive keratectomy (PRK) vs. laser-assisted in-situ keratomileusis (LASIK), and the mean age of patients in each quarter. Chi-square test was used to compare the proportions of treated refractive errors and the proportions of procedures; two-tailed t-test to compare the mean age of patients; and two-tailed z-test to compare proportions of grouped refractive errors in 2007 vs. 2009; alpha = 0.05 for all tests. Refractive errors were grouped by the spherical equivalent of the manifest refraction and were considered "low myopia" for 6 diopters (D) of myopia or less, "high myopia" for more than 6 D, and "hyperopia" for any hyperopia. Billing data were reviewed to obtain the volume of premium IOLs. Volume of laser refractive procedures decreased by at least 30%. The distribution of proportions of treated refractive errors did not change (p = 0.10). The proportion of high myopes, however, decreased (p = 0.05). The proportions of types of procedure changed, with an increase in the proportion of PRK between 2007 and 2009 (p = 0.02). The mean age of patients did not change [42.4 ± 14.4 (standard deviation) years in 2007 vs. 39.6 ± 14.5 years in 2009; p = 0.4]. Astigmatism-correcting IOL and presbyopia-correcting IOL volumes increased 15-fold and three-fold, respectively, between 2007 and 2009. Volume of excimer laser refractive surgery decreased by at least 30% between 2007 and 2009. No significant change in mean age or in the distribution of refractive error was seen, although the proportion of high myopes decreased between summer quarters of 2007 and 2009. PRK gained as a proportion of total cases. Premium IOL volume increased, but still comprised a very small proportion of total IOL volume.

Trends in refractive surgery at an academic center: 2007-2009

PubMed Central

2011-01-01

Background The United States officially entered a recession in December 2007, and it officially exited the recession in December 2009, according to the National Bureau of Economic Research. Since the economy may affect not only the volume of excimer laser refractive surgery, but also the clinical characteristics of patients undergoing surgery, our goal was to compare the characteristics of patients completing excimer laser refractive surgery and the types of procedures performed in the summer quarter in 2007 and the same quarter in 2009 at an academic center. A secondary goal was to determine whether the volume of astigmatism- or presbyopia-correcting intraocular lenses (IOLs) has concurrently changed because like laser refractive surgery, these "premium" IOLs involve out-of-pocket costs for patients. Methods Retrospective case series. Medical records were reviewed for all patients completing surgery at the Wilmer Laser Vision Center in the summer quarter of 2007 and the summer quarter of 2009. Outcome measures were the proportions of treated refractive errors, the proportion of photorefractive keratectomy (PRK) vs. laser-assisted in-situ keratomileusis (LASIK), and the mean age of patients in each quarter. Chi-square test was used to compare the proportions of treated refractive errors and the proportions of procedures; two-tailed t-test to compare the mean age of patients; and two-tailed z-test to compare proportions of grouped refractive errors in 2007 vs. 2009; alpha = 0.05 for all tests. Refractive errors were grouped by the spherical equivalent of the manifest refraction and were considered "low myopia" for 6 diopters (D) of myopia or less, "high myopia" for more than 6 D, and "hyperopia" for any hyperopia. Billing data were reviewed to obtain the volume of premium IOLs. Results Volume of laser refractive procedures decreased by at least 30%. The distribution of proportions of treated refractive errors did not change (p = 0.10). The proportion of high myopes, however, decreased (p = 0.05). The proportions of types of procedure changed, with an increase in the proportion of PRK between 2007 and 2009 (p = 0.02). The mean age of patients did not change [42.4 ± 14.4 (standard deviation) years in 2007 vs. 39.6 ± 14.5 years in 2009; p = 0.4]. Astigmatism-correcting IOL and presbyopia-correcting IOL volumes increased 15-fold and three-fold, respectively, between 2007 and 2009. Conclusions Volume of excimer laser refractive surgery decreased by at least 30% between 2007 and 2009. No significant change in mean age or in the distribution of refractive error was seen, although the proportion of high myopes decreased between summer quarters of 2007 and 2009. PRK gained as a proportion of total cases. Premium IOL volume increased, but still comprised a very small proportion of total IOL volume. PMID:21569564

Refractive errors in children with autism in a developing country.

PubMed

Ezegwui, I R; Lawrence, L; Aghaji, A E; Okoye, O I; Okoye, O; Onwasigwe, E N; Ebigbo, P O

2014-01-01

In a resource-limited country visual problems of mentally challenged individuals are often neglected. The present study aims to study refractive errors in children diagnosed with autism in a developing country. Ophthalmic examination was carried out on children diagnosed with autism attending a school for the mentally challenged in Enugu, Nigeria between December 2009 and May 2010. Visual acuity was assessed using Lea symbols. Anterior and posterior segments were examined. Cycloplegic refraction was performed. Data was entered on the protocol prepared for the study and analyzed using Statistical Package for the Social Sciences version 17 (Chicago IL, USA). A total of 21 children with autism were enrolled in the school; 18 of whom were examined giving coverage of 85.7%. The age range was 5-15 years, with a mean of 10.28 years (standard deviation ± 3.20). There were 13 boys and 5 girls. One child had bilateral temporal pallor of the disc and one had bilateral maculopathy with diffuse chorioretinal atrophy. Refraction revealed 4 children (22.2%) had astigmatism and 2 children (11.1%) had hypermetropia. Significant refractive error mainly astigmatism was noted in the children with autism. Identifying refractive errors in these children early and providing appropriate corrective lenses may help optimize their visual functioning and impact their activities of daily life in a positive way.

The Relationship between Higher-order Aberrations and Amblyopia Treatment in Hyperopic Anisometropic Amblyopia

PubMed Central

Lee, Soo Han

2014-01-01

Purpose To investigate the relationship between higher-order aberrations (HOAs) and amblyopia treatment in children with hyperopic anisometropic amblyopia. Methods The medical records of hyperopic amblyopia patients with both spherical anisometropia of 1.00 diopter (D) or more and astigmatic anisometropia of less than 1.00 D were reviewed retrospectively. Based on the results of the amblyopia treatment, patients were divided into two groups: treatment successes and failures. Using the degree of spherical anisometropia, subjects were categorized into mild, moderate, or severe groups. Ocular, corneal, and internal HOAs were measured using a KR-1W aberrometer at the initial visit, and at 3-month, 6-month, and 12-month follow-ups. Results The results of the 45 (21 males and 24 females) hyperopic anisometropic amblyopia patients who completed the 12-month follow-up examinations were analyzed. The mean patient age at the initial visit was 70.3 months. In total, 28 patients (62.2%) had successful amblyopia treatments and 17 patients (37.8%) failed treatment after 12 months. Among the patient population, 24 (53.3%) had mild hyperopic anisometropia and 21 (46.7%) had moderate hyperopic anisometropia. When comparing the two groups (i.e., the success and failure groups), ocular spherical aberrations and internal spherical aberrations in the amblyopic eyes were significantly higher in the failure group at every follow-up point. There were no significant differences in any of the HOAs between mild and moderate cases of hyperopic anisometropia at any follow-up. When the amblyopic and fellow eyes were compared between the groups there were no significant differences in any of the HOAs. Conclusions HOAs, particularly ocular spherical aberrations and internal spherical aberrations, should be considered as reasons for failed amblyopia treatment. PMID:24505201

Refractive error characteristics of early and advanced presbyopic individuals.

DOT National Transportation Integrated Search

1977-07-01

The frequency and distribution of ocular refractive errors among middle-aged and older people were obtained from a nonclinical population holding a variety of blue-collar, clerical, and technical jobs. The 422 individuals ranged in age from 35 to 69 ...

Foveal retinoschisis misdiagnosed as bilateral amblyopia.

PubMed

Kyung, Sungeun E; Lee, Minsoo

2012-12-01

Juvenile foveal retinoschisis is one of the most common causes of bilateral macular degeneration in young boys. School age with accommodative esotropia may develop amblyopia due to late correction of hyperopia. Retinoschisis is hard to diagnose in patient with subtle macula change and hyperopic amblyopia. We report a case of bilateral foveal retinoschisis before and after treatment with topical dorzolamide, which was misdiagnosed as bilateral hyperopic amblyopia. Optical coherence tomography should be considered in diagnostic procedures of children with hyperopic amblyopia.

Refraction corrected calibration for aquatic locomotion research: application of Snell's law improves spatial accuracy.

PubMed

Henrion, Sebastian; Spoor, Cees W; Pieters, Remco P M; Müller, Ulrike K; van Leeuwen, Johan L

2015-07-07

Images of underwater objects are distorted by refraction at the water-glass-air interfaces and these distortions can lead to substantial errors when reconstructing the objects' position and shape. So far, aquatic locomotion studies have minimized refraction in their experimental setups and used the direct linear transform algorithm (DLT) to reconstruct position information, which does not model refraction explicitly. Here we present a refraction corrected ray-tracing algorithm (RCRT) that reconstructs position information using Snell's law. We validated this reconstruction by calculating 3D reconstruction error-the difference between actual and reconstructed position of a marker. We found that reconstruction error is small (typically less than 1%). Compared with the DLT algorithm, the RCRT has overall lower reconstruction errors, especially outside the calibration volume, and errors are essentially insensitive to camera position and orientation and the number and position of the calibration points. To demonstrate the effectiveness of the RCRT, we tracked an anatomical marker on a seahorse recorded with four cameras to reconstruct the swimming trajectory for six different camera configurations. The RCRT algorithm is accurate and robust and it allows cameras to be oriented at large angles of incidence and facilitates the development of accurate tracking algorithms to quantify aquatic manoeuvers.

Automatic diagnostic system for measuring ocular refractive errors

NASA Astrophysics Data System (ADS)

Ventura, Liliane; Chiaradia, Caio; de Sousa, Sidney J. F.; de Castro, Jarbas C.

1996-05-01

Ocular refractive errors (myopia, hyperopia and astigmatism) are automatic and objectively determined by projecting a light target onto the retina using an infra-red (850 nm) diode laser. The light vergence which emerges from the eye (light scattered from the retina) is evaluated in order to determine the corresponding ametropia. The system basically consists of projecting a target (ring) onto the retina and analyzing the scattered light with a CCD camera. The light scattered by the eye is divided into six portions (3 meridians) by using a mask and a set of six prisms. The distance between the two images provided by each of the meridians, leads to the refractive error of the referred meridian. Hence, it is possible to determine the refractive error at three different meridians, which gives the exact solution for the eye's refractive error (spherical and cylindrical components and the axis of the astigmatism). The computational basis used for the image analysis is a heuristic search, which provides satisfactory calculation times for our purposes. The peculiar shape of the target, a ring, provides a wider range of measurement and also saves parts of the retina from unnecessary laser irradiation. Measurements were done in artificial and in vivo eyes (using cicloplegics) and the results were in good agreement with the retinoscopic measurements.

The prevalence of refractive errors in 6- to 15-year-old schoolchildren in Dezful, Iran.

PubMed

Norouzirad, Reza; Hashemi, Hassan; Yekta, Abbasali; Nirouzad, Fereidon; Ostadimoghaddam, Hadi; Yazdani, Negareh; Dadbin, Nooshin; Javaherforoushzadeh, Ali; Khabazkhoob, Mehdi

2015-01-01

To determine the prevalence of refractive errors, among 6- to 15-year-old schoolchildren in the city of Dezful in western Iran. In this cross-sectional study, 1375 Dezful schoolchildren were selected through multistage cluster sampling. After obtaining written consent, participants had uncorrected and corrected visual acuity tests and cycloplegic refraction at the school site. Refractive errors were defined as myopia [spherical equivalent (SE) -0.5 diopter (D)], hyperopia (SE ≥ 2.0D), and astigmatism (cylinder error > 0.5D). 1151 (83.7%) schoolchildren participated in the study. Of these, 1130 completed their examinations. 21 individuals were excluded because of poor cooperation and contraindication for cycloplegic refraction. Prevalence of myopia, hyperopia, and astigmatism were 14.9% (95% confidence interval (CI): 10.1-19.6), 12.9% (95% CI: 7.2-18.6), and 45.3% (95% CI: 40.3-50.3), respectively. Multiple logistic regression analysis showed an age-related increase in myopia prevalence (p < 0.001) and a decrease in hyperopia prevalence (p < 0.001). There was a higher prevalence of myopia in boys (p<0.001) and hyperopia in girls (p = 0.007). This study showed a considerably high prevalence of refractive errors among the Iranian population of schoolchildren in Dezful in the west of Iran. The prevalence of myopia is considerably high compared to previous studies in Iran and increases with age.

Preventable visual impairment in children 
with nonprofound intellectual disability.

PubMed

Aslan, Lokman; Aslankurt, Murat; Aksoy, Adnan; Altun, Hatice

2013-01-01

To assess the preventable visual impairment in children with nonprofound intellectual disability (ID). 
 A total of 215 children with IDs (90 Down syndrome [DS], 125 nonprofound ID) and 116 age- and sex-matched healthy subjects were enrolled in this study. All participants underwent ophthalmologic examinations including cycloplegic refraction measurements, ocular movement evaluation, screening for strabismus (Hirschberg, Krimsky, or prism cover test), slit-lamp biomicroscopy, funduscopy, and intraocular pressure measurements. All data were recorded for statistical analysis.
 Ocular findings in decreasing prevalence were as follows: refractive errors 55 (61.1%), strabismus 30 (33.2%), cataract 7 (7.8%), and nystagmus 7 (7.8%) in children with DS; refractive errors 57 (45.6%), strabismus 19 (15.2%), cataract 7 (6.4%), nystagmus 5 (4%), and glaucoma 1 (0.8%) in children with other ID; and refractive errors 13 (11.2%) and strabismus 4 (3.5%) in controls. Cataracts, glaucoma, and nystagmus were not observed in the control group. The most common ophthalmic findings in children with DS compared with other ID and controls were with hyperopia (p<0.03 and 
p<0.001, respectively) and esotropia (p<0.01 and p<0.01, respectively).
 The pediatric population with ID has a high prevalence of preventable visual impairments, refractive errors, strabismus, and cataracts. The prevalence of strabismus and refractive errors was more frequent in children with DS. The importance of further health screenings including ophthalmic examinations should be utilized to implement appropriate care management and improve quality of life.

Cycloplegic refraction is the gold standard for epidemiological studies.

PubMed

Morgan, Ian G; Iribarren, Rafael; Fotouhi, Akbar; Grzybowski, Andrzej

2015-09-01

Many studies on children have shown that lack of cycloplegia is associated with slight overestimation of myopia and marked errors in estimates of the prevalence of emmetropia and hyperopia. Non-cycloplegic refraction is particularly problematic for studies of associations with risk factors. The consensus around the importance of cycloplegia in children left undefined at what age, if any, cycloplegia became unnecessary. It was often implicitly assumed that cycloplegia is not necessary beyond childhood or early adulthood, and thus, the protocol for the classical studies of refraction in older adults did not include cycloplegia. Now that population studies of refractive error are beginning to fill the gap between schoolchildren and older adults, whether cycloplegia is required for measuring refractive error in this age range, needs to be defined. Data from the Tehran Eye Study show that, without cycloplegia, there are errors in the estimation of myopia, emmetropia and hyperopia in the age range 20-50, just as in children. Similar results have been reported in an analysis of data from the Beaver Dam Offspring Eye Study. If the only important outcome measure of a particular study is the prevalence of myopia, then cycloplegia may not be crucial in some cases. But, without cycloplegia, measurements of other refractive categories as well as spherical equivalent are unreliable. In summary, the current evidence suggests that cycloplegic refraction should be considered as the gold standard for epidemiological studies of refraction, not only in children, but in adults up to the age of 50. © 2015 Acta Ophthalmologica Scandinavica Foundation. Published by John Wiley & Sons Ltd.

Anisometropia of ocular refractive and biometric measures among 66- to 79-year-old female twins.

PubMed

Pärssinen, Olavi; Kauppinen, Markku; Kaprio, Jaakko; Rantanen, Taina

2016-12-01

To examine the prevalence of anisometropia of spherical refraction (AnisoSR), astigmatism (AnisoAST) and spherical equivalent (AnisoSE) and their associations with spherical refraction (SR), refractive astigmatism (AST), spherical equivalent (SE) and interocular differences of ocular biometric parameters among elderly female twins. Refraction of 117 monozygotic (MZ) and 116 dizygotic (DZ) female twin subjects aged 66-79 years was assessed with an auto-refractor (Topcon AT) and controlled by subjective refraction. Corneal refraction, anterior chamber depth and axial length were measured with a Zeiss IOL Master. Participants with eyes operated for cataract or glaucoma were excluded, but the grade of nuclear opacity was not recorded. The associations between the absolute values of AnisoSR, AnisoAST and AnisoSE with SR, AST, SE, corneal refractive power (CR), corneal astigmatism (CAST), anterior chamber depth (ACD) and axial length (AL) and with their interocular differences were calculated. When calculating the interdependencies of the differences, the real and absolute differences between the right and left eye were used. Means ± standard deviations for AnisoSR, AnisoAST and AnisoSE were 0.67 ± 0.92 D, 0.42 ± 0.41 D and 0.65 ± 0.71 D, respectively. AnisoSR, AnisoAST and AnisoSE >1.0 D were present in 14.7%, 4.2% and 17.7% of cases, respectively. Anisometropia of spherical refraction (AnisoSR), AnisoAST and AnisoSE were higher the more negative the values of SR or SE. Hyperopic ametropia did not increase these anisometropia values. The correlations of AnisoSR and AnisoSE with the absolute values of interocular differences in CR and AL were non-significant. Using the real values of the interocular differences, the respective correlations were significant. The correlation between the real interocular differences in CR and AL was negative (r = -0.258, p < 0.001). Thus, the combined effect of the real interocular differences in CR and AL was a decrease in AnisoSR and AnisoSE (emmetropization). Higher AnisoSR and AnisoSE were associated with more myopic refraction and longer AL. Higher AnisoAST was associated with more negative SR and higher AST and CAST. The negative correlation between real interocular differences in CR and AL indicated their influence of emmetropization in AnisoSR and AnisoSE. © 2016 Acta Ophthalmologica Scandinavica Foundation. Published by John Wiley & Sons Ltd.

Self correction of refractive error among young people in rural China: results of cross sectional investigation

PubMed Central

Zhang, Mingzhi; Zhang, Riping; He, Mingguang; Liang, Wanling; Li, Xiaofeng; She, Lingbing; Yang, Yunli; MacKenzie, Graeme; Silver, Joshua D; Ellwein, Leon; Moore, Bruce

2011-01-01

Objective To compare outcomes between adjustable spectacles and conventional methods for refraction in young people. Design Cross sectional study. Setting Rural southern China. Participants 648 young people aged 12-18 (mean 14.9 (SD 0.98)), with uncorrected visual acuity ≤6/12 in either eye. Interventions All participants underwent self refraction without cycloplegia (paralysis of near focusing ability with topical eye drops), automated refraction without cycloplegia, and subjective refraction by an ophthalmologist with cycloplegia. Main outcome measures Uncorrected and corrected vision, improvement of vision (lines on a chart), and refractive error. Results Among the participants, 59% (384) were girls, 44% (288) wore spectacles, and 61% (393/648) had 2.00 dioptres or more of myopia in the right eye. All completed self refraction. The proportion with visual acuity ≥6/7.5 in the better eye was 5.2% (95% confidence interval 3.6% to 6.9%) for uncorrected vision, 30.2% (25.7% to 34.8%) for currently worn spectacles, 96.9% (95.5% to 98.3%) for self refraction, 98.4% (97.4% to 99.5%) for automated refraction, and 99.1% (98.3% to 99.9%) for subjective refraction (P=0.033 for self refraction v automated refraction, P=0.001 for self refraction v subjective refraction). Improvements over uncorrected vision in the better eye with self refraction and subjective refraction were within one line on the eye chart in 98% of participants. In logistic regression models, failure to achieve maximum recorded visual acuity of 6/7.5 in right eyes with self refraction was associated with greater absolute value of myopia/hyperopia (P<0.001), greater astigmatism (P=0.001), and not having previously worn spectacles (P=0.002), but not age or sex. Significant inaccuracies in power (≥1.00 dioptre) were less common in right eyes with self refraction than with automated refraction (5% v 11%, P<0.001). Conclusions Though visual acuity was slightly worse with self refraction than automated or subjective refraction, acuity was excellent in nearly all these young people with inadequately corrected refractive error at baseline. Inaccurate power was less common with self refraction than automated refraction. Self refraction could decrease the requirement for scarce trained personnel, expensive devices, and cycloplegia in children’s vision programmes in rural China. PMID:21828207

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.

[Can the scattering of differences from the target refraction be avoided?].

PubMed

Janknecht, P

2008-10-01

We wanted to check how the stochastic error is affected by two lens formulae. The power of the intraocular lens was calculated using the SRK-II formula and the Haigis formula after eye length measurement with ultrasound and the IOL Master. Both lens formulae were partially derived and Gauss error analysis was used for examination of the propagated error. 61 patients with a mean age of 73.8 years were analysed. The postoperative refraction differed from the calculated refraction after ultrasound biometry using the SRK-II formula by 0.05 D (-1.56 to + 1.31, S. D.: 0.59 D; 92 % within +/- 1.0 D), after IOL Master biometry using the SRK-II formula by -0.15 D (-1.18 to + 1.25, S. D.: 0.52 D; 97 % within +/- 1.0 D), and after IOL Master biometry using the Haigis formula by -0.11 D (-1.14 to + 1.14, S. D.: 0.48 D; 95 % within +/- 1.0 D). The results did not differ from one another. The propagated error of the Haigis formula can be calculated according to DeltaP = square root (deltaL x (-4.206))(2) + (deltaVK x 0.9496)(2) + (DeltaDC x (-1.4950))(2). (DeltaL: error measuring axial length, DeltaVK error measuring anterior chamber depth, DeltaDC error measuring corneal power), the propagated error of the SRK-II formula according to DeltaP = square root (DeltaL x (-2.5))(2) + (DeltaDC x (-0.9))(2). The propagated error of the Haigis formula is always larger than the propagated error of the SRK-II formula. Scattering of the postoperative difference from the expected refraction cannot be avoided completely. It is possible to limit the systematic error by developing complicated formulae like the Haigis formula. However, increasing the number of parameters which need to be measured increases the dispersion of the calculated postoperative refraction. A compromise has to be found, and therefore the SRK-II formula is not outdated.

Nondestructive measurement of the refractive index distribution of a glass molded lens by two-wavelength wavefronts.

PubMed

Sugimoto, Tomohiro

2016-10-01

This paper presents a nondestructive and non-exact-index-matching method for measuring the refractive index distribution of a glass molded lens with high refractivity. The method measures two-wavelength wavefronts of a test lens immersed in a liquid with a refractive index dispersion different from that of the test lens and calculates the refractive index distribution by eliminating the refractive index distribution error caused by the shape error of the test lens. The estimated uncertainties of the refractive index distributions of test lenses with n_d≈1.77 and n_d≈1.85 were 1.9×10^-5  RMS and 2.4×10^-5  RMS, respectively. I validated the proposed method by evaluating the agreement between the estimated uncertainties and experimental values.

Effects of lenses with different power profiles on eye shape in chickens.

PubMed

Tepelus, Tudor Cosmin; Vazquez, Daniel; Seidemann, Anne; Uttenweiler, Dietmar; Schaeffel, Frank

2012-02-01

Defocus imposed to the periphery of the visual field can affect the development of foveal/central refractive errors. To make use of this observation, lenses can be designed to reduce myopia progression, but it is important to know which power profiles of the lenses are most effective. We have studied this question in chickens. Sixty male white leghorn chickens were used. From day 7 after hatching, they were treated for 5 days either with full field -7D or +7D lenses, with -7D lenses with a 4mm central hole, with hemi-field lenses of the same power, or with two different types of radial refractive gradient (RRG) lenses with increasing positive power from the center to the periphery, which were designed by Rodenstock GmbH, Munich, Germany. A macro file was written for "ImageJ" to trace and average the outlines of several excised eyes after treatment. Shapes of fellow control eyes and lens-treated eyes were compared in the horizontal and vertical meridians. Refractions were determined at -45°, 0°, and 45° over the horizontal visual field, at the beginning and at the end of experiments, using automated infrared photoretinoscopy. (1) Eye length, as determined by the new automated eye shape tracing technique, was well correlated with A-scan ultrasound data. (2) The effects of previously tested lens designs were reproduced with the new tracing technique. Full field lenses were by far the most effective (-7D: external axial length +0.24mm with an increase in eye volume of about 6%, +7D: -0.08 mm, with a decrease in eye volume of about 2%). Hemi-field lenses and negative lenses with a 4mm central hole induced conspicuous local changes in eye shape. (3) The first type of RRG lenses with a plano zone of about 4mm (equivalent to about ± 12.52° in the visual field for a vertex distance of 5mm) had no apparent effect on central refractions but induced small hyperopic shifts in the periphery, more significant in the temporal retina (+1.70 ± 1.70 D, p<0.001, paired t-test to untreated fellow eyes). The second type of RRG lenses with a small plano zone of 2mm (equivalent to ± 6.34°) induced peripheral hyperopia but also changed the central refraction (temporal retina +1.50 ± 1.17D, p<0.001, central retina +0.77 ± 1.15 D, p<0.01, nasal retina +1.47±1.35D, p<0.001, paired t-test to untreated control eyes). In the afoveate chick, RRG lenses have an effect on central refraction and eye growth only if the central plano zone is small (<4mm). For the second type of RRG lens with a central plano zone of about 2mm, inhibitory effects on eye growth were detected in both the center and periphery even though the optical power of the lenses in the periphery was low. Copyright © 2011 Elsevier Ltd. All rights reserved.

Visual symptoms associated with refractive errors among Thangka artists of Kathmandu valley.

PubMed

Dhungel, Deepa; Shrestha, Gauri Shankar

2017-12-21

Prolong near work, especially among people with uncorrected refractive error is considered a potential source of visual symptoms. The present study aims to determine the visual symptoms and the association of those with refractive errors among Thangka artists. In a descriptive cross-sectional study, 242 (46.1%) participants of 525 thangka artists examined, with age ranged between 16 years to 39 years which comprised of 112 participants with significant refractive errors and 130 absolutely emmetropic participants, were enrolled from six Thangka painting schools. The visual symptoms were assessed using a structured questionnaire consisting of nine items and scoring from 0 to 6 consecutive scales. The eye examination included detailed anterior and posterior segment examination, objective and subjective refraction, and assessment of heterophoria, vergence and accommodation. Symptoms were presented in percentage and median. Variation in distribution of participants and symptoms was analysed using the Kruskal Wallis test for mean, and the correlation with the Pearson correlation coefficient. A significance level of 0.05 was applied for 95% confidence interval. The majority of participants (65.1%) among refractive error group (REG) were above the age of 30 years, with a male predominance (61.6%), compared to the participants in the normal cohort group (NCG), where majority of them (72.3%) were below 30 years of age (72.3%) and female (51.5%). Overall, the visual symptoms are high among Thangka artists. However, blurred vision (p = 0.003) and dry eye (p = 0.004) are higher among the REG than the NCG. Females have slightly higher symptoms than males. Most of the symptoms, such as sore/aching eye (p = 0.003), feeling dry (p = 0.005) and blurred vision (p = 0.02) are significantly associated with astigmatism. Thangka artists present with significant proportion of refractive error and visual symptoms, especially among females. The most commonly reported symptoms are blurred vision, dry eye and watering of the eye. The visual symptoms are more correlated with astigmatism.

Ametropias in school-age children in Fada N'Gourma (Burkina Faso, Africa).

PubMed

Jiménez, Raimundo; Soler, Margarita; Anera, Rosario G; Castro, José J; Pérez, M Angustias; Salas, Carlos

2012-01-01

To assess epidemiological aspects of refractive errors in school-age children in Burkina Faso (west-central Africa). A total of 315 school children (ranging from 6 to 16 years of age and belonging to different ethnic groups) taken at random from two urban schools in eastern Burkina Faso were examined to assess their refractive error, which was determined by non-cycloplegic retinoscopy with optical fogging. The standard Refractive Error Study in Children (RESC) definitions of refractive errors were used: myopia ≤-0.5 D spherical equivalent (SE) in at least one eye, hyperopia ≥2 D SE in at least one eye, astigmatism ≤-0.75 D cylinder in at least one eye, and anisometropia ≥1 D SE difference between the two eyes. Unilateral myopia and bilateral myopia were found in 2.5 and 1%, respectively; unilateral hyperopia in 17.1%, bilateral hyperopia in 8.6%; astigmatism in at least one eye in 11.7%. The highest prevalence value (18.4%) of astigmatism (≤-0.75 D) in at least one eye was found in the Gourmantché ethnic group. The low prevalence of large refractive errors makes visual acuity in these children very good (visual acuity logarithm of the minimum angle of resolution -0.073 ± 0.123 SD). There was a low prevalence of myopia in these African school children. Clinically significant high hyperopia (≥+2 D SE) was also uncommon. There were no significant differences between the distributions of refractive errors according to gender or ethnicity. With respect to age groups, the prevalences of hyperopia and astigmatism were significantly higher in the younger age groups.

Laser in-situ keratomileusis for refractive error following radial keratotomy

PubMed Central

Sinha, Rajesh; Sharma, Namrata; Ahuja, Rakesh; Kumar, Chandrashekhar; Vajpayee, Rasik B

2011-01-01

Aim: To evaluate the safety and efficacy of laser in-situ keratomileusis (LASIK) in eyes with residual/induced refractive error following radial keratotomy (RK). Design: Retrospective study. Materials and Methods: A retrospective analysis of data of 18 eyes of 10 patients, who had undergone LASIK for refractive error following RK, was performed. All the patients had undergone RK in both eyes at least one year before LASIK. Parameters like uncorrected visual acuity (UCVA), best-corrected visual acuity (BCVA), contrast sensitivity, glare acuity and corneal parameters were evaluated both preoperatively and postoperatively. Statistical Software: STATA-9.0. Results: The mean UCVA before LASIK was 0.16±0.16 which improved to 0.64 ± 0.22 (P < 0.001) after one year following LASIK. Fourteen eyes (out of 18) had UCVA of ≥ 20/30 on Snellen's acuity chart at one year following LASIK. The mean BCVA before LASIK was 0.75 ± 0.18. This improved to 0.87 ± 0.16 at one year following LASIK. The mean spherical refractive error at the time of LASIK and at one year after the procedure was –5.37 ± 4.83 diopters (D) and –0.22 ± 1.45D, respectively. Only three eyes had a residual spherical refractive error of ≥ 1.0D at one year follow-up. In two eyes, we noted opening up of the RK incisions. No eye developed epithelial in-growth till 1 year after LASIK. Conclusion: LASIK is effective in treating refractive error following RK. However, it carries the risk of flap-related complications like opening up of the previously placed RK incisions and splitting of the corneal flap. PMID:21666312

Prevalence of uncorrected refractive errors, presbyopia and spectacle coverage in marine fishing communities in South India: Rapid Assessment of Visual Impairment (RAVI) project.

PubMed

Marmamula, Srinivas; Madala, Sreenivas R; Rao, Gullapalli N

2012-03-01

To investigate the prevalence of uncorrected refractive errors, presbyopia and spectacle coverage in subjects aged 40 years or more using a novel Rapid Assessment of Visual Impairment (RAVI) methodology. A population-based cross-sectional study was conducted using cluster random sampling to enumerate 1700 subjects from 34 clusters predominantly inhabited by marine fishing communities in the Prakasam district of Andhra Pradesh, India. Unaided, aided and pinhole visual acuity (VA) was assessed using a Snellen chart at a distance of 6 m. Near vision was assessed using an N notation chart. Uncorrected refractive error was defined as presenting VA < 6/18 and improving to ≥6/18 with pinhole. Uncorrected presbyopia was defined as binocular near vision worse than N8 in subjects with binocular distance VA ≥ 6/18. 1560 subjects (response rate - 92%) were available for examination. Of these, 54.6% were female and 10.1% were ≥70 years of age. Refractive error was present in 250 individuals. It was uncorrected in 179 (unmet need) and corrected in 71 (met need) individuals. Among 1094 individuals with no distance visual impairment, presbyopia was present in 494 individuals. It was uncorrected in 439 (unmet need) and corrected in 55 individuals (met need). Spectacle coverage was 28.4% for refractive errors and 11.1% for presbyopia. There is a high unmet need for uncorrected refractive errors and presbyopia among marine fishing communities in the Prakasam district of South India. The data from this study can now be used as a baseline prior to the commencement of eye care services in this region. Ophthalmic & Physiological Optics © 2012 The College of Optometrists.

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.

Prevalence of refractive errors and associated risk factors in subjects with type 2 diabetes mellitus SN-DREAMS, report 18.

PubMed

Rani, Padmaja Kumari; Raman, Rajiv; Rachapalli, Sudhir R; Kulothungan, Vaitheeswaran; Kumaramanickavel, Govindasamy; Sharma, Tarun

2010-06-01

To report the prevalence of refractive errors and the associated risk factors in subjects with type 2 diabetes mellitus from an urban Indian population. Population-based, cross-sectional study. One thousand eighty participants selected from a pool of 1414 subjects with diabetes. A population-based sample of 1414 persons (age >40 years) with diabetes (identified as per the World Health Organization criteria) underwent a comprehensive eye examination, including objective and subjective refractions. One thousand eighty subjects who were phakic in the right eye with best corrected visual acuity of > or =20/40 were included in the analysis for prevalence of refractive errors. Univariate and multivariate analyses were done to find out the independent risk factors associated with the refractive errors. The mean refraction was +0.20+/-1.72, and the Median, +0.25 diopters. The prevalence of emmetropia (spherical equivalent [SE], -0.50 to +0.50 diopter sphere [DS]) was 39.26%. The prevalence of myopia (SE <-0.50 DS), high myopia (SE <-5.00 DS), hyperopia (SE >+0.50 DS), and astigmatism (SE <-0.50 cyl) was 19.4%, 1.6%, 39.7%, and 47.4%, respectively. The advancing age was an important risk factor for the three refractive errors: for myopia, odds ratio (OR; 95% confidence interval [CI] 4.06 [1.74-9.50]; for hyperopia, OR [95% CI] 5.85 [2.56-13.39]; and for astigmatism, OR [95% CI] 2.51 [1.34-4.71]). Poor glycemic control was associated with myopia (OR [95% CI] 4.15 [1.44-11.92]) and astigmatism (OR [95% CI] 2.01 [1.04-3.88]). Female gender was associated with hyperopia alone) OR [95% CI] 2.00 [1.42-2.82]. The present population-based study from urban India noted a high prevalence of refractive errors (60%) among diabetic subjects >40 years old; the prevalence of astigmatism (47%) was higher than hyperopia (40%) or myopia (20%). Copyright 2010 American Academy of Ophthalmology. Published by Elsevier Inc. All rights reserved.

Child Development and Refractive Errors in Preschool Children

PubMed Central

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

2011-01-01

Purpose Many parents are concerned about their child's development. The purpose of this study is to determine if parental concerns about overall development are associated with significant refractive errors among urban preschool children. Methods A cross-sectional population-based study was conducted to evaluate the prevalence of ocular disorders in white and African American children 6 through 71 months of age in Baltimore, Maryland, United States. A comprehensive eye examination with cycloplegic refraction was performed. Parental concerns about development were measured with the Parents' Evaluation of Developmental Status screening tool. 2381 of 2546 eligible children (93.5%) completed the refraction and the parental interview. Results Parental concerns about development were present in 510 of the 2381 children evaluated (21.4%; 95% CI: 9.8% – 23.1%). The adjusted odds ratios [OR] of parental concerns with hyperopia (≥ 3.00D) was 1.26 (95% CI: 0.90 – 1.74), with myopia (≥ 1.00D) was 1.29 (95% CI: 0.83 – 2.03), with astigmatism (≥ 1.50D) was 1.44 (95% CI: 1.08 – 1.93) irrespective of the type of astigmatism, and with anisometropia ≥ 2.00D was 2.61 (95% CI: 1.07 – 6.34). The odds of parental concerns about development significantly increased in children older than 36 months with hyperopia ≥ 3.00D, astigmatism ≥ 1.50D, or anisometropia ≥ 2.00D. Conclusions Parental concerns about general developmental problems were associated with some types of refractive error, astigmatism ≥ 1.50D and anisometropia ≥ 2.00D in children ages 6 to 71 months. Parental concerns were also more likely in children older than 36 months of age with hypermetropia, astigmatism or anisometropia. Parental concerns were not associated with myopia. Due to the potential consequences of uncorrected refractive errors, children whose parents have expressed concerns regarding development should be referred for an eye examination with cycloplegic refraction to rule out significant refractive errors. PMID:21150680

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

Genome-wide association meta-analysis highlights light-induced signaling as a driver for refractive error.

PubMed

Tedja, Milly S; Wojciechowski, Robert; Hysi, Pirro G; Eriksson, Nicholas; Furlotte, Nicholas A; Verhoeven, Virginie J M; Iglesias, Adriana I; Meester-Smoor, Magda A; Tompson, Stuart W; Fan, Qiao; Khawaja, Anthony P; Cheng, Ching-Yu; Höhn, René; Yamashiro, Kenji; Wenocur, Adam; Grazal, Clare; Haller, Toomas; Metspalu, Andres; Wedenoja, Juho; Jonas, Jost B; Wang, Ya Xing; Xie, Jing; Mitchell, Paul; Foster, Paul J; Klein, Barbara E K; Klein, Ronald; Paterson, Andrew D; Hosseini, S Mohsen; Shah, Rupal L; Williams, Cathy; Teo, Yik Ying; Tham, Yih Chung; Gupta, Preeti; Zhao, Wanting; Shi, Yuan; Saw, Woei-Yuh; Tai, E-Shyong; Sim, Xue Ling; Huffman, Jennifer E; Polašek, Ozren; Hayward, Caroline; Bencic, Goran; Rudan, Igor; Wilson, James F; Joshi, Peter K; Tsujikawa, Akitaka; Matsuda, Fumihiko; Whisenhunt, Kristina N; Zeller, Tanja; van der Spek, Peter J; Haak, Roxanna; Meijers-Heijboer, Hanne; van Leeuwen, Elisabeth M; Iyengar, Sudha K; Lass, Jonathan H; Hofman, Albert; Rivadeneira, Fernando; Uitterlinden, André G; Vingerling, Johannes R; Lehtimäki, Terho; Raitakari, Olli T; Biino, Ginevra; Concas, Maria Pina; Schwantes-An, Tae-Hwi; Igo, Robert P; Cuellar-Partida, Gabriel; Martin, Nicholas G; Craig, Jamie E; Gharahkhani, Puya; Williams, Katie M; Nag, Abhishek; Rahi, Jugnoo S; Cumberland, Phillippa M; Delcourt, Cécile; Bellenguez, Céline; Ried, Janina S; Bergen, Arthur A; Meitinger, Thomas; Gieger, Christian; Wong, Tien Yin; Hewitt, Alex W; Mackey, David A; Simpson, Claire L; Pfeiffer, Norbert; Pärssinen, Olavi; Baird, Paul N; Vitart, Veronique; Amin, Najaf; van Duijn, Cornelia M; Bailey-Wilson, Joan E; Young, Terri L; Saw, Seang-Mei; Stambolian, Dwight; MacGregor, Stuart; Guggenheim, Jeremy A; Tung, Joyce Y; Hammond, Christopher J; Klaver, Caroline C W

2018-06-01

Refractive errors, including myopia, are the most frequent eye disorders worldwide and an increasingly common cause of blindness. This genome-wide association meta-analysis in 160,420 participants and replication in 95,505 participants increased the number of established independent signals from 37 to 161 and showed high genetic correlation between Europeans and Asians (>0.78). Expression experiments and comprehensive in silico analyses identified retinal cell physiology and light processing as prominent mechanisms, and also identified functional contributions to refractive-error development in all cell types of the neurosensory retina, retinal pigment epithelium, vascular endothelium and extracellular matrix. Newly identified genes implicate novel mechanisms such as rod-and-cone bipolar synaptic neurotransmission, anterior-segment morphology and angiogenesis. Thirty-one loci resided in or near regions transcribing small RNAs, thus suggesting a role for post-transcriptional regulation. Our results support the notion that refractive errors are caused by a light-dependent retina-to-sclera signaling cascade and delineate potential pathobiological molecular drivers.

Correct consideration of the index of refraction using blackbody radiation.

PubMed

Hartmann, Jurgen

2006-09-04

The correct consideration of the index of refraction when using blackbody radiators as standard sources for optical radiation is derived and discussed. It is shown that simply using the index of refraction of air at laboratory conditions is not sufficient. A combination of the index of refraction of the media used inside the blackbody radiator and for the optical path between blackbody and detector has to be used instead. A worst case approximation for the introduced error when neglecting these effects is presented, showing that the error is below 0.1 % for wavelengths above 200 nm. Nevertheless, for the determination of the spectral radiance for the purpose of radiation temperature measurements the correct consideration of the refractive index is mandatory. The worst case estimation reveals that the introduced error in temperature at a blackbody temperature of 3000 degrees C can be as high as 400 mk at a wavelength of 650 nm and even higher at longer wavelengths.

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.

Influence of different types of astigmatism on visual acuity.

PubMed

Remón, Laura; Monsoriu, Juan A; Furlan, Walter D

To investigate the change in visual acuity (VA) produced by different types of astigmatism (on the basis of the refractive power and position of the principal meridians) on normal accommodating eyes. The lens induced method was employed to simulate a set of 28 astigmatic blur conditions on different healthy emmetropic eyes. Additionally, 24 values of spherical defocus were also simulated on the same eyes for comparison. VA was measured in each case and the results, expressed in logMAR units, were represented against of the modulus of the dioptric power vector (blur strength). LogMAR VA varies in a linear fashion with increasing astigmatic blur, being the slope of the line dependent on the accommodative demand in each type of astigmatism. However, in each case, we found no statistically significant differences between the three axes investigated (0°, 45°, 90°). Non-statistically significant differences were found either for the VA achieved with spherical myopic defocus (MD) and mixed astigmatism (MA). VA with simple hyperopic astigmatism (SHA) was higher than with simple myopic astigmatism (SMA), however, in this case non conclusive results were obtained in terms of statistical significance. The VA achieved with imposed compound hyperopic astigmatism (CHA) was highly influenced by the eye's accommodative response. VA is correlated with the blur strength in a different way for each type of astigmatism, depending on the accommodative demand. VA is better when one of the focal lines lie on the retina irrespective of the axis orientation; accommodation favors this situation. Copyright © 2016 Spanish General Council of Optometry. Published by Elsevier España, S.L.U. All rights reserved.

[Improvement of vision through perceptual learning in the case of refractive errors and presbyopia : A critical valuation].

PubMed

Heinrich, S P

2017-02-01

The idea of compensating or even rectifying refractive errors and presbyopia with the help of vision training is not new. For most approaches, however, scientific evidence is insufficient. A currently promoted method is "perceptual learning", which is assumed to improve stimulus processing in the brain. The basic phenomena of perceptual learning have been demonstrated by a multitude of studies. Some of these specifically address the case of refractive errors and presbyopia. However, many open questions remain, in particular with respect to the transfer of practice effects to every-day vision. At present, the method should therefore be judged with caution.

Determining Nanoparticle Inhalation Exposure in the Prosthetics Laboratory at Walter Reed National Military Medical Center

DTIC Science & Technology

2013-04-29

monotonic for particles sized between 500 and 1500 nm. There is also a response error for different refractive indexes of particles (59). In addition, all...accuracy when a range of refractive indexes is present. Detector response error ranges from 50-100%, depending on the refractive index present (17...Respiratory Diseases. Journal of American Medical Association 295 1127-33 13. Eftim E, Samet J, anes H, McDermott A, Dominici F. 2008. Fine

Visual Survey of Infantry Troops. Part 1. Visual Acuity, Refractive Status, Interpupillary Distance and Visual Skills

DTIC Science & Technology

1989-06-01

letters on one line and several letters on the next line, there is no accurate way to credit these extra letters for statistical analysis. The decimal and...contains the descriptive statistics of the objective refractive error components of infantrymen. Figures 8-11 show the frequency distributions for sphere...equivalents. Nonspectacle wearers Table 12 contains the idescriptive statistics for non- spectacle wearers. Based or these refractive error data, about 30

The inverse problem of refraction travel times, part II: Quantifying refraction nonuniqueness using a three-layer model

USGS Publications Warehouse

Ivanov, J.; Miller, R.D.; Xia, J.; Steeples, D.

2005-01-01

This paper is the second of a set of two papers in which we study the inverse refraction problem. The first paper, "Types of Geophysical Nonuniqueness through Minimization," studies and classifies the types of nonuniqueness that exist when solving inverse problems depending on the participation of a priori information required to obtain reliable solutions of inverse geophysical problems. In view of the classification developed, in this paper we study the type of nonuniqueness associated with the inverse refraction problem. An approach for obtaining a realistic solution to the inverse refraction problem is offered in a third paper that is in preparation. The nonuniqueness of the inverse refraction problem is examined by using a simple three-layer model. Like many other inverse geophysical problems, the inverse refraction problem does not have a unique solution. Conventionally, nonuniqueness is considered to be a result of insufficient data and/or error in the data, for any fixed number of model parameters. This study illustrates that even for overdetermined and error free data, nonlinear inverse refraction problems exhibit exact-data nonuniqueness, which further complicates the problem of nonuniqueness. By evaluating the nonuniqueness of the inverse refraction problem, this paper targets the improvement of refraction inversion algorithms, and as a result, the achievement of more realistic solutions. The nonuniqueness of the inverse refraction problem is examined initially by using a simple three-layer model. The observations and conclusions of the three-layer model nonuniqueness study are used to evaluate the nonuniqueness of more complicated n-layer models and multi-parameter cell models such as in refraction tomography. For any fixed number of model parameters, the inverse refraction problem exhibits continuous ranges of exact-data nonuniqueness. Such an unfavorable type of nonuniqueness can be uniquely solved only by providing abundant a priori information. Insufficient a priori information during the inversion is the reason why refraction methods often may not produce desired results or even fail. This work also demonstrates that the application of the smoothing constraints, typical when solving ill-posed inverse problems, has a dual and contradictory role when applied to the ill-posed inverse problem of refraction travel times. This observation indicates that smoothing constraints may play such a two-fold role when applied to other inverse problems. Other factors that contribute to inverse-refraction-problem nonuniqueness are also considered, including indeterminacy, statistical data-error distribution, numerical error and instability, finite data, and model parameters. ?? Birkha??user Verlag, Basel, 2005.

Long-term follow-up of acute isolated accommodation insufficiency.

PubMed

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

2013-04-01

To define the long-term results of accommodation insufficiency and to investigate the correlation between accommodation insufficiency and other factors including near point of convergence (NPC), age, and refractive errors. From January 2008 to December 2009, 11 patients with acute near vision disturbance and remote near point of accommodation (NPA) were evaluated. Full ophthalmologic examinations, including best corrected visual acuity, manifest refraction and prism cover tests were performed. Accommodation ability was measured by NPA using the push-up method. We compared accommodation insufficiency and factors including age, refractive errors and NPC. We also investigated the recovery from loss of accommodation in patients. Mean age of patients was 20 years (range, 9 to 34 years). Five of the 11 patients were female. Mean refractive error was -0.6 diopters (range, -3.5 to +0.25 diopters) and 8 of 11 patients (73%) had emmetropia (+0.50 to -0.50 diopters). No abnormalities were found in brain imaging tests. Refractive errors were not correlated with NPA or NPC (rho = 0.148, p = 0.511; rho = 0.319, p = 0.339; respectively). The correlation between age and NPA was not significant (rho = -395, p = 0.069). However, the correlation between age and NPC was negative (rho = -0.508, p = 0.016). Three of 11 patients were lost to follow-up, and 6 of 8 patients had permanent insufficiency of accommodation. Accommodation insufficiency is most common in emmetropia, however, refractive errors and age are not correlated with accommodation insufficiency. Dysfunction of accommodation can be permanent in the isolated accommodation insufficiency.

Long-term Follow-up of Acute Isolated Accommodation Insufficiency

PubMed Central

Lee, Jung Jin; Baek, Seung-Hee

2013-01-01

Purpose To define the long-term results of accommodation insufficiency and to investigate the correlation between accommodation insufficiency and other factors including near point of convergence (NPC), age, and refractive errors. Methods From January 2008 to December 2009, 11 patients with acute near vision disturbance and remote near point of accommodation (NPA) were evaluated. Full ophthalmologic examinations, including best corrected visual acuity, manifest refraction and prism cover tests were performed. Accommodation ability was measured by NPA using the push-up method. We compared accommodation insufficiency and factors including age, refractive errors and NPC. We also investigated the recovery from loss of accommodation in patients. Results Mean age of patients was 20 years (range, 9 to 34 years). Five of the 11 patients were female. Mean refractive error was -0.6 diopters (range, -3.5 to +0.25 diopters) and 8 of 11 patients (73%) had emmetropia (+0.50 to -0.50 diopters). No abnormalities were found in brain imaging tests. Refractive errors were not correlated with NPA or NPC (rho = 0.148, p = 0.511; rho = 0.319, p = 0.339; respectively). The correlation between age and NPA was not significant (rho = -395, p = 0.069). However, the correlation between age and NPC was negative (rho = -0.508, p = 0.016). Three of 11 patients were lost to follow-up, and 6 of 8 patients had permanent insufficiency of accommodation. Conclusions Accommodation insufficiency is most common in emmetropia, however, refractive errors and age are not correlated with accommodation insufficiency. Dysfunction of accommodation can be permanent in the isolated accommodation insufficiency. PMID:23543051

Prevalence of Refractive Errors in Students with and without Color Vision Deficiency

PubMed Central

Ostadimoghaddam, Hadi; Yekta, Abbas Ali; Heravian, Javad; Azimi, Abbas; Hosseini, Seyed Mahdi Ahmadi; Vatandoust, Sakineh; Sharifi, Fatemeh; Abolbashari, Fereshteh

2014-01-01

Purpose: To evaluate refractive errors in school age children with color vision deficiency (CVD) and those with normal color vision (NCV) in order to make a better understanding of the emmetropization process. Methods: A total of 4,400 primary school students aged 7–12 years were screened for color vision using Ishihara pseudoisochromatic color vision plate sets. Of these, 160 (3.6%) students had CVD. A total of 400 age- and sex-matched students with NCV were selected as controls. Refractive status was evaluated using objective cyclorefraction. Results: The CVD group included 136 male (85%) and 24 female (15%) subjects with mean age of 10.1 ± 1.8 years. The NCV group comprised of 336 male (84%) and 64 female (16%) subjects with mean age of 10.5 ± 1.2 years. The prevalence of myopia (7.7% vs. 13.9%, P < 0.001) and hyperopia (41% vs. 57.4%, P = 0.03) was significantly lower in the CVD group. Furthermore, subjects with CVD subjects demonstrated a lower magnitude of refractive errors as compared to the CVD group (mean refractive error: +0.54 ± 0.19 D versus + 0.74 ± 1.12 D, P < 0.001). Conclusion: Although the lower prevalence of myopia in subjects with CVD group supports the role of longitudinal chromatic aberration in the development of refractive errors; the lower prevalence of hyperopia in this group is an opposing finding. Myopia is a multifactorial disorder and longitudinal chromatic aberration is not the only factor influencing the emmetropization process. PMID:25709775

Small refractive errors--their correction and practical importance.

PubMed

Skrbek, Matej; Petrová, Sylvie

2013-04-01

Small refractive errors present a group of specifc far-sighted refractive dispositions that are compensated by enhanced accommodative exertion and aren't exhibited by loss of the visual acuity. This paper should answer a few questions about their correction, flowing from theoretical presumptions and expectations of this dilemma. The main goal of this research was to (dis)confirm the hypothesis about convenience, efficiency and frequency of the correction that do not raise the visual acuity (or if the improvement isn't noticeable). The next goal was to examine the connection between this correction and other factors (age, size of the refractive error, etc.). The last aim was to describe the subjective personal rating of the correction of these small refractive errors, and to determine the minimal improvement of the visual acuity, that is attractive enough for the client to purchase the correction (glasses, contact lenses). It was confirmed, that there's an indispensable group of subjects with good visual acuity, where the correction is applicable, although it doesn't improve the visual acuity much. The main importance is to eliminate the asthenopia. The prime reason for acceptance of the correction is typically changing during the life, so as the accommodation is declining. Young people prefer the correction on the ground of the asthenopia, caused by small refractive error or latent strabismus; elderly people acquire the correction because of improvement of the visual acuity. Generally the correction was found useful in more than 30%, if the gain of the visual acuity was at least 0,3 of the decimal row.

Calculation of Ophthalmic Viscoelastic Device–Induced Focus Shift During Femtosecond Laser–Assisted Cataract Surgery

PubMed Central

de Freitas, Carolina P.; Cabot, Florence; Manns, Fabrice; Culbertson, William; Yoo, Sonia H.; Parel, Jean-Marie

2015-01-01

Purpose. To assess if a change in refractive index of the anterior chamber during femtosecond laser-assisted cataract surgery can affect the laser beam focus position. Methods. The index of refraction and chromatic dispersion of six ophthalmic viscoelastic devices (OVDs) was measured with an Abbe refractometer. Using the Gullstrand eye model, the index values were used to predict the error in the depth of a femtosecond laser cut when the anterior chamber is filled with OVD. Two sources of error produced by the change in refractive index were evaluated: the error in anterior capsule position measured with optical coherence tomography biometry and the shift in femtosecond laser beam focus depth. Results. The refractive indices of the OVDs measured ranged from 1.335 to 1.341 in the visible light (at 587 nm). The error in depth measurement of the refilled anterior chamber ranged from −5 to +7 μm. The OVD produced a shift of the femtosecond laser focus ranging from −1 to +6 μm. Replacement of the aqueous humor with OVDs with the densest compound produced a predicted error in cut depth of 13 μm anterior to the expected cut. Conclusions. Our calculations show that the change in refractive index due to anterior chamber refilling does not sufficiently shift the laser beam focus position to cause the incomplete capsulotomies reported during femtosecond laser–assisted cataract surgery. PMID:25626971

Theoretical analyses of the refractive implications of transepithelial PRK ablations.

PubMed

Arba Mosquera, Samuel; Awwad, Shady T

2013-07-01

To analyse the refractive implications of single-step, transepithelial photorefractive keratectomy (TransPRK) ablations. A simulation for quantifying the refractive implications of TransPRK ablations has been developed. The simulation includes a simple modelling of corneal epithelial profiles, epithelial ablation profiles as well as refractive ablation profiles, and allows the analytical quantification of the refractive implications of TransPRK in terms of wasted tissue, achieved optical zone (OZ) and induced refractive error. Wasted tissue occurs whenever the actual corneal epithelial profile is thinner than the applied epithelial ablation profile, achieved OZ is reduced whenever the actual corneal epithelial profile is thicker than the applied epithelial ablation profile and additional refractive errors are induced whenever the actual difference centre-to-periphery in the corneal epithelial profile deviates from the difference in the applied epithelial ablation profile. The refractive implications of TransPRK ablations can be quantified using simple theoretical simulations. These implications can be wasted tissue (∼14 µm, if the corneal epithelial profile is thinner than the ablated one), reduced OZ (if the corneal epithelial profile is thicker than ablated one, very severe for low corrections) and additional refractive errors (∼0.66 D, if the centre-to-periphery progression of the corneal epithelial profile deviates from the progression of the ablated one). When TransPRK profiles are applied to normal, not previously treated, non-pathologic corneas, no specific refractive implications associated to the transepithelial profile can be anticipated; TransPRK would provide refractive outcomes equal to those of standard PRK. Adjustments for the planned OZ and, in the event of retreatments, for the target sphere can be easily derived.

Creeping posterior synechiae following hyperopic iris-fixated phakic implants.

PubMed

Messina, Marco; Elalfy, Mohamed; Fares, Usama; Ghoz, Noha; Mavi, Balraj; Dua, Harminder

2016-12-01

The purpose of this study was to report on the occurrence and management of posterior synechiae (PS) in three hyperopic eyes after iris-fixated anterior chamber phakic IOL implantation. This is a case report of a 55-year-old man and a 55-year-old lady who had undergone iris-fixated anterior chamber phakic IOL implantation to correct hyperopic astigmatism (one eye) and hyperopia (both eyes), respectively. The three eyes developed creeping PS and pigment dispersion within 4-6 weeks of surgery. Synechiolysis and pupil stretching in one eye did not work as the synechiae promptly recurred. Definitive management in the form of removal of the phakic implant and phacoemulsification with lens implant was successful in restoring normal vision in all three eyes. Although implantation of phakic intraocular lenses has been reported to be very effective for the correction of moderate to high degrees of ametropia, this complication can occur in hyperopic eyes. Pigment dispersion has been reported in myopic eyes also, but PS seem to be more an issue with hyperopic eyes. Age of the patient may also be a factor. This information is important in the selection and counselling of patients.

Modeling of mouse eye and errors in ocular parameters affecting refractive state

NASA Astrophysics Data System (ADS)

Bawa, Gurinder

Rodents eye are particularly used to study refractive error state of an eye and development of refractive eye. Genetic organization of rodents is similar to that of humans, which makes them interesting candidates to be researched upon. From rodents family mice models are encouraged over rats because of availability of genetically engineered models. Despite of extensive work that has been performed on mice and rat models, still no one is able to quantify an optical model, due to variability in the reported ocular parameters. In this Dissertation, we have extracted ocular parameters and generated schematics of eye from the raw data from School of Medicine, Detroit. In order to see how the rays would travel through an eye and the defects associated with an eye; ray tracing has been performed using ocular parameters. Finally we have systematically evaluated the contribution of various ocular parameters, such as radii of curvature of ocular surfaces, thicknesses of ocular components, and refractive indices of ocular refractive media, using variational analysis and a computational model of the rodent eye. Variational analysis revealed that variation in all the ocular parameters does affect the refractive status of the eye, but depending upon the magnitude of the impact those parameters are listed as critical or non critical. Variation in the depth of the vitreous chamber, thickness of the lens, radius of the anterior surface of the cornea, radius of the anterior surface of the lens, as well as refractive indices for the lens and vitreous, appears to have the largest impact on the refractive error and thus are categorized as critical ocular parameters. The radii of the posterior surfaces of the cornea and lens have much smaller contributions to the refractive state, while the radii of the anterior and posterior surfaces of the retina have no effect on the refractive error. These data provide the framework for further refinement of the optical models of the rat and mouse eye and suggest that extra efforts should be directed towards increasing the linear resolution of the rodent eye biometry and obtaining more accurate data for the refractive indices of the lens and vitreous.

Retrieving the Vertical Structure of the Effective Aerosol Complex Index of Refraction from a Combination of Aerosol in Situ and Remote Sensing Measurements During TARFOX

NASA Technical Reports Server (NTRS)

Redemann, J.; Turco, R. P.; Liou, K. N.; Russell, P. B.; Bergstrom, R. W.; Schmid, B.; Livingston, J. M.; Hobbs, P. V.; Hartley, W. S.; Ismail, S.

2000-01-01

The largest uncertainty in estimates of the effects of atmospheric aerosols on climate stems from uncertainties in the determination of their microphysical properties, including the aerosol complex index of refraction, which in turn determines their optical properties. A novel technique is used to estimate the aerosol complex index of refraction in distinct vertical layers from a combination of aerosol in situ size distribution and remote sensing measurements during the Tropospheric Aerosol Radiative Forcing Observational Experiment (TARFOX). In particular, aerosol backscatter measurements using the NASA Langley LASE (Lidar Atmospheric Sensing Experiment) instrument and in situ aerosol size distribution data are utilized to derive vertical profiles of the 'effective' aerosol complex index of refraction at 815 nm (i.e., the refractive index that would provide the same backscatter signal in a forward calculation on the basis of the measured in situ particle size distributions for homogeneous, spherical aerosols). A sensitivity study shows that this method yields small errors in the retrieved aerosol refractive indices, provided the errors in the lidar derived aerosol backscatter are less than 30% and random in nature. Absolute errors in the estimated aerosol refractive indices are generally less than 0.04 for the real part and can be as much as 0.042 for the imaginary part in the case of a 30% error in the lidar-derived aerosol backscatter. The measurements of aerosol optical depth from the NASA Ames Airborne Tracking Sunphotometer (AATS-6) are successfully incorporated into the new technique and help constrain the retrieved aerosol refractive indices. An application of the technique to two TARFOX case studies yields the occurrence of vertical layers of distinct aerosol refractive indices. Values of the estimated complex aerosol refractive index range from 1.33 to 1.45 for the real part and 0.001 to 0.008 for the imaginary part. The methodology devised in this study provides, for the first time a complete set of vertically resolved aerosol size distribution and refractive index data, yielding the vertical distribution of aerosol optical properties required for the determination of aersol-induced radiative flux changes

Retrieving the Vertical Structure of the Effective Aerosol Complex Index of Refraction from a Combination of Aerosol in Situ and Remote Sensing Measurements During TARFOX

NASA Technical Reports Server (NTRS)

Redemann, J.; Turco, R. P.; Liou, K. N.; Russell, P. B.; Bergstrom, R. W.; Schmid, B.; Livingston, J. M.; Hobbs, P. V.; Hartley, W. S.; Ismail, S.;

High prevalence of narrow angles among Filipino-American patients.

PubMed

Seider, Michael I; Sáles, Christopher S; Lee, Roland Y; Agadzi, Anthony K; Porco, Travis C; Weinreb, Robert N; Lin, Shan C

2011-03-01

To determine the prevalence of gonioscopically narrow anterior chamber angles in a Filipino-American clinic population. The records of 122 consecutive, new, self-declared Filipino-American patients examined in a comprehensive ophthalmology clinic in Vallejo, California were reviewed retrospectively. After exclusion, 222 eyes from 112 patients remained for analysis. Data were collected for anterior chamber angle grade as determined by gonioscopy (Shaffer system), age, sex, manifest refraction (spherical equivalent), intraocular pressure, and cup-to-disk ratio. Data from both eyes of patients were included and modeled using standard linear mixed-effects regression. As a comparison, data were also collected from a group of 30 consecutive White patients from the same clinic. After exclusion, 50 eyes from 25 White patients remained for comparison. At least 1 eye of 24% of Filipino-American patients had a narrow anterior chamber angle (Shaffer grade ≤ 2). Filipino-American angle grade significantly decreased with increasingly hyperopic refraction (P=0.007) and larger cup-to-disk ratio (P=0.038). Filipino-American women had significantly decreased angle grades compared with men (P=0.028), but angle grade did not vary by intraocular pressure or age (all, P≥ 0.059). Narrow anterior chamber angles are highly prevalent in Filipino-American patients in our clinic population.

Dopaminergic agonists that result in ocular growth inhibition also elicit transient increases in choroidal thickness in chicks

PubMed Central

Nickla, Debora L.; Totonelly, Kristen; Dhillon, Balprit

2010-01-01

The dopaminergic system has been implicated in ocular growth regulation in chicks and monkeys. In both, dopamine D2 agonists inhibit the development of myopia in response to form deprivation, and in chicks, to negative lenses as well. Because there is mounting evidence that the choroidal response to defocus plays a role in ocular growth regulation, we asked whether the effective agonists also elicit transient thickening of the choroid concomitant with the growth inhibition. Negative lenses mounted on velcro rings were worn on one eye starting at age 8-12 days. Intravitreal injections (20 μl; dose=10 nmole) of the agonist (dissolved in saline) or saline, were given through the superior temporal sclera using a 30G needle. Eyes were injected daily at noon, for 4 days, and the lenses immediately replaced. Agonists used were apomorphine (non-specific; n=17), quinpirole (D2; n=10), SKF-38393 (D1; n=9), and saline controls (n=22). For the antagonists, the same protocol was used, but on each day, the lenses were removed for 2 hours. Immediately prior to lens-removal, the antagonist was injected (20 μl; dose=5 nmole). Antagonists used were methylergonovine (non-specific; n=12), spiperone (D2; n=20), SCH-23390 (D1 n=6) and saline controls (n=27). Comparisons to saline (continuous lens wear) controls were from the agonist experiment. Axial dimensions were measured using high frequency A-scan ultrasonography at the start of lens wear, and on day 4 prior to the injections, and then again 3 hours later. Refractive errors were measured using a Hartinger's refractometer at the end of the experiment. Apomorphine and quinpirole inhibited the refractive response to the hyperopic defocus induced by the negative lenses (drug vs saline controls: -1.3 and 1.2 D vs -5.6 D; p<0.005 for both). This effect was axial: both drugs prevented the excessive ocular elongation (change in axial length: 233 and 205 μm vs 417 um; p<0.01 for both). Both drugs were also associated with a transient thickening of the choroid over 3 hours (41 and 32 um vs –1 um; p<0.01; p=0.059 respectively) that did not summate: choroids thinned significantly over the 4 day period in all lens-wearing eyes. Two daily hours of unrestricted vision during negative lens wear normally prevents the development of myopia. Spiperone and SCH-23390 inhibited the ameliorating effects of periods of vision on lens-induced refractive error (-2.9 and –2.8 D vs 0.6 D; p<0.0001), however, the effects on neither axial length nor choroidal thickness were significant. These data support a role for both D1 and D2 receptors in the ocular growth responses. PMID:20801115

Studies of atmospheric refraction effects on laser data

NASA Technical Reports Server (NTRS)

Dunn, P. J.; Pearce, W. A.; Johnson, T. S.

1982-01-01

The refraction effect from three perspectives was considered. An analysis of the axioms on which the accepted correction algorithms were based was the first priority. The integrity of the meteorological measurements on which the correction model is based was also considered and a large quantity of laser observations was processed in an effort to detect any serious anomalies in them. The effect of refraction errors on geodetic parameters estimated from laser data using the most recent analysis procedures was the focus of the third element of study. The results concentrate on refraction errors which were found to be critical in the eventual use of the data for measurements of crustal dynamics.

Prevention of myopia by partial correction of hyperopia: a twins study.

PubMed

Medina, Antonio

2018-04-01

To confirm the prediction of emmetropization feedback theory that myopia can be prevented by correcting the hyperopia of a child at risk of becoming myopic. We conducted such myopia prevention treatment with twins at risk. Their hyperopia was partially corrected by one half at age 7 and in subsequent years until age 16. Hyperopia progressively decreased in all eyes as expected. None of the twins developed myopia. The spherical equivalent refractions of the followed eyes were +1 and +1.25 D at age 16. Feedback theory accurately predicted these values. The treatment of the twins with partial correction of their hyperopia was successful. Prevention of myopia with this technique is relatively simple and powerful. The use of this myopia prevention treatment has no adverse effects. This prevention treatment is indicated in children with a hyperopic reserve at risk of developing myopia.

Effects of tropospheric and ionospheric refraction errors in the utilization of GEOS-C altimeter data

NASA Technical Reports Server (NTRS)

Goad, C. C.

1977-01-01

The effects of tropospheric and ionospheric refraction errors are analyzed for the GEOS-C altimeter project in terms of their resultant effects on C-band orbits and the altimeter measurement itself. Operational procedures using surface meteorological measurements at ground stations and monthly means for ocean surface conditions are assumed, with no corrections made for ionospheric effects. Effects on the orbit height due to tropospheric errors are approximately 15 cm for single pass short arcs (such as for calibration) and 10 cm for global orbits of one revolution. Orbit height errors due to neglect of the ionosphere have an amplitude of approximately 40 cm when the orbits are determined from C-band range data with predominantly daylight tracking. Altimeter measurement errors are approximately 10 cm due to residual tropospheric refraction correction errors. Ionospheric effects on the altimeter range measurement are also on the order of 10 cm during the GEOS-C launch and early operation period.

Refractive Status at Birth: Its Relation to Newborn Physical Parameters at Birth and Gestational Age

PubMed Central

Varghese, Raji Mathew; Sreenivas, Vishnubhatla; Puliyel, Jacob Mammen; Varughese, Sara

2009-01-01

Background Refractive status at birth is related to gestational age. Preterm babies have myopia which decreases as gestational age increases and term babies are known to be hypermetropic. This study looked at the correlation of refractive status with birth weight in term and preterm babies, and with physical indicators of intra-uterine growth such as the head circumference and length of the baby at birth. Methods All babies delivered at St. Stephens Hospital and admitted in the nursery were eligible for the study. Refraction was performed within the first week of life. 0.8% tropicamide with 0.5% phenylephrine was used to achieve cycloplegia and paralysis of accommodation. 599 newborn babies participated in the study. Data pertaining to the right eye is utilized for all the analyses except that for anisometropia where the two eyes were compared. Growth parameters were measured soon after birth. Simple linear regression analysis was performed to see the association of refractive status, (mean spherical equivalent (MSE), astigmatism and anisometropia) with each of the study variables, namely gestation, length, weight and head circumference. Subsequently, multiple linear regression was carried out to identify the independent predictors for each of the outcome parameters. Results Simple linear regression showed a significant relation between all 4 study variables and refractive error but in multiple regression only gestational age and weight were related to refractive error. The partial correlation of weight with MSE adjusted for gestation was 0.28 and that of gestation with MSE adjusted for weight was 0.10. Birth weight had a higher correlation to MSE than gestational age. Conclusion This is the first study to look at refractive error against all these growth parameters, in preterm and term babies at birth. It would appear from this study that birth weight rather than gestation should be used as criteria for screening for refractive error, especially in developing countries where the incidence of intrauterine malnutrition is higher. PMID:19214228

Genome-wide association study for refractive astigmatism reveals genetic co-determination with spherical equivalent refractive error: the CREAM consortium.

PubMed

Li, Qing; Wojciechowski, Robert; Simpson, Claire L; Hysi, Pirro G; Verhoeven, Virginie J M; Ikram, Mohammad Kamran; Höhn, René; Vitart, Veronique; Hewitt, Alex W; Oexle, Konrad; Mäkelä, Kari-Matti; MacGregor, Stuart; Pirastu, Mario; Fan, Qiao; Cheng, Ching-Yu; St Pourcain, Beaté; McMahon, George; Kemp, John P; Northstone, Kate; Rahi, Jugnoo S; Cumberland, Phillippa M; Martin, Nicholas G; Sanfilippo, Paul G; Lu, Yi; Wang, Ya Xing; Hayward, Caroline; Polašek, Ozren; Campbell, Harry; Bencic, Goran; Wright, Alan F; Wedenoja, Juho; Zeller, Tanja; Schillert, Arne; Mirshahi, Alireza; Lackner, Karl; Yip, Shea Ping; Yap, Maurice K H; Ried, Janina S; Gieger, Christian; Murgia, Federico; Wilson, James F; Fleck, Brian; Yazar, Seyhan; Vingerling, Johannes R; Hofman, Albert; Uitterlinden, André; Rivadeneira, Fernando; Amin, Najaf; Karssen, Lennart; Oostra, Ben A; Zhou, Xin; Teo, Yik-Ying; Tai, E Shyong; Vithana, Eranga; Barathi, Veluchamy; Zheng, Yingfeng; Siantar, Rosalynn Grace; Neelam, Kumari; Shin, Youchan; Lam, Janice; Yonova-Doing, Ekaterina; Venturini, Cristina; Hosseini, S Mohsen; Wong, Hoi-Suen; Lehtimäki, Terho; Kähönen, Mika; Raitakari, Olli; Timpson, Nicholas J; Evans, David M; Khor, Chiea-Chuen; Aung, Tin; Young, Terri L; Mitchell, Paul; Klein, Barbara; van Duijn, Cornelia M; Meitinger, Thomas; Jonas, Jost B; Baird, Paul N; Mackey, David A; Wong, Tien Yin; Saw, Seang-Mei; Pärssinen, Olavi; Stambolian, Dwight; Hammond, Christopher J; Klaver, Caroline C W; Williams, Cathy; Paterson, Andrew D; Bailey-Wilson, Joan E; Guggenheim, Jeremy A

2015-02-01

To identify genetic variants associated with refractive astigmatism in the general population, meta-analyses of genome-wide association studies were performed for: White Europeans aged at least 25 years (20 cohorts, N = 31,968); Asian subjects aged at least 25 years (7 cohorts, N = 9,295); White Europeans aged <25 years (4 cohorts, N = 5,640); and all independent individuals from the above three samples combined with a sample of Chinese subjects aged <25 years (N = 45,931). Participants were classified as cases with refractive astigmatism if the average cylinder power in their two eyes was at least 1.00 diopter and as controls otherwise. Genome-wide association analysis was carried out for each cohort separately using logistic regression. Meta-analysis was conducted using a fixed effects model. In the older European group the most strongly associated marker was downstream of the neurexin-1 (NRXN1) gene (rs1401327, P = 3.92E-8). No other region reached genome-wide significance, and association signals were lower for the younger European group and Asian group. In the meta-analysis of all cohorts, no marker reached genome-wide significance: The most strongly associated regions were, NRXN1 (rs1401327, P = 2.93E-07), TOX (rs7823467, P = 3.47E-07) and LINC00340 (rs12212674, P = 1.49E-06). For 34 markers identified in prior GWAS for spherical equivalent refractive error, the beta coefficients for genotype versus spherical equivalent, and genotype versus refractive astigmatism, were highly correlated (r = -0.59, P = 2.10E-04). This work revealed no consistent or strong genetic signals for refractive astigmatism; however, the TOX gene region previously identified in GWAS for spherical equivalent refractive error was the second most strongly associated region. Analysis of additional markers provided evidence supporting widespread genetic co-susceptibility for spherical and astigmatic refractive errors.

Opposite Effects of Glucagon and Insulin on Compensation for Spectacle Lenses in Chicks

PubMed Central

Zhu, Xiaoying; Wallman, Josh

2009-01-01

Purpose Chick eyes compensate for defocus imposed by positive or negative spectacle lenses. Glucagon may signal the sign of defocus. Do insulin (or IGF-1) and glucagon act oppositely in controlling eye growth, as they do in metabolic pathways and in control of retinal neurogenesis? Methods Chicks, wearing either lenses or diffusers or neither over both eyes, were injected with glucagon, a glucagon antagonist, insulin, or IGF-1 in one eye (saline in other eye). Alternatively, chicks without lenses received insulin plus glucagon in one eye, and either glucagon or insulin in the fellow eye. Ocular dimensions, refractive errors and glycosaminoglycan synthesis were measured over 2-4 days. Results Glucagon attenuated the myopic response to negative lenses or diffusers by slowing ocular elongation and thickening the choroid; in contrast, with positive lenses, it increased ocular elongation to normal levels and reduced choroidal thickening, as did a glucagon antagonist. Insulin prevented the hyperopic response to positive lenses by speeding ocular elongation and thinning the choroid. In eyes without lenses, both insulin and IGF-1 speeded, and glucagon slowed, ocular elongation, but either glucagon or insulin increased the rate of thickening of the crystalline lens. When injected together, insulin blocked choroidal thickening by glucagon, at a dose that did not, by itself, thin the choroid. Conclusions Glucagon and insulin (or IGF-1) cause generally opposite modulations of eye-growth, with glucagon mostly increasing choroidal thickness and insulin mostly increasing ocular elongation. These effects are mutually inhibitory and depend on the visual input. PMID:18791176

Reverse amblyopia with atropine treatment.

PubMed

Hainline, Bryan C; Sprunger, Derek C; Plager, David A; Neely, Daniel E; Guess, Matthew G

2009-01-01

Occlusion, pharmacologic pernalization and combined therapy have been documented in controlled studies to effectively treat amblyopia with few complications. However, there remain concerns about the effectiveness and complications when, as in this case, there are not standardized treatment protocols. A retrospective chart review of 133 consecutive patients in one community based ophthalmology practice treated for amblyopia was performed. Treatments evaluated were occlusion only, atropine penalization, and combination of occlusion and atropine. Reverse amblyopia was defined as having occured when the visual acuity of the sound eye was 3 LogMar units worse than visual acuity of the amblyopia eye after treatment. Improvement in vision after 6 months and 1 year of amblyopia therapy was similar among all three groups: 0.26 LogMar lines and 0.30 in the atropine group, 0.32 and 0.34 in the occlusion group, and 0.24 and 0.32 in the combined group. Eight (6%) patients demonstrated reverse amblyopia. The mean age of those who developed reverse amblyopia was 3.5 years, 1.5 years younger than the mean age of the study population, 7/8 had strabismic amblyopia, 6/8 were on daily atropine and had a mean refractive error of +4.77 diopters in the amblyopic eye and +5.06 diopters in the sound eye. Reverse amblyopia did not occur with occlusion only therapy. In this community based ophthalmology practice, atropine, patching, and combination therapy appear to be equally effective modalities to treat ambyopia. Highly hyperopic patients under 4 years of age with dense, strabismic amblyopia and on daily atropine appeared to be most at risk for development of reverse amblyopia.

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.

Determination of effective complex refractive index of a turbid liquid with surface plasmon resonance phase detection.

PubMed

Yingying, Zhang; Jiancheng, Lai; Cheng, Yin; Zhenhua, Li

2009-03-01

The dependence of the surface plasmon resonance (SPR) phase difference curve on the complex refractive index of a sample in Kretschmann configuration is discussed comprehensively, based on which a new method is proposed to measure the complex refractive index of turbid liquid. A corresponding experiment setup was constructed to measure the SPR phase difference curve, and the complex refractive index of turbid liquid was determined. By using the setup, the complex refractive indices of Intralipid solutions with concentrations of 5%, 10%, 15%, and 20% are obtained to be 1.3377+0.0005 i, 1.3427+0.0028 i, 1.3476+0.0034 i, and 1.3496+0.0038 i, respectively. Furthermore, the error analysis indicates that the root-mean-square errors of both the real and the imaginary parts of the measured complex refractive index are less than 5x10(-5).

Three-dimensional ray-tracing model for the study of advanced refractive errors in keratoconus.

PubMed

Schedin, Staffan; Hallberg, Per; Behndig, Anders

2016-01-20

We propose a numerical three-dimensional (3D) ray-tracing model for the analysis of advanced corneal refractive errors. The 3D modeling was based on measured corneal elevation data by means of Scheimpflug photography. A mathematical description of the measured corneal surfaces from a keratoconus (KC) patient was used for the 3D ray tracing, based on Snell's law of refraction. A model of a commercial intraocular lens (IOL) was included in the analysis. By modifying the posterior IOL surface, it was shown that the imaging quality could be significantly improved. The RMS values were reduced by approximately 50% close to the retina, both for on- and off-axis geometries. The 3D ray-tracing model can constitute a basis for simulation of customized IOLs that are able to correct the advanced, irregular refractive errors in KC.

Corrective lens use and refractive error among United States Air Force aircrew.

PubMed

Wright, Steve T; Ivan, Douglas J; Clark, Patrick J; Gooch, John M; Thompson, William

2010-03-01

Corrective lens use by military aviators is an important consideration in the design of head-mounted equipment. The United States Air Force (USAF) has periodically monitored lens use by aviators; however, it has been over a decade since the last study. We provide an update on the prevalence of corrective lenses and refractive error among USAF aircrew based on eyeglass orders processed through the Spectacle Request Transmission System (SRTS). Currently, 41% of active duty USAF pilots and 54% of other aircrew require corrective lenses to perform flight duties. Refractive errors are characterized by low to moderate levels of myopia with a mean spherical equivalent power of -1.01 diopters (D) for pilots and -1.68 D for others. Contact lenses, and more recently refractive surgery, reduce the number of aircrew that must rely on spectacles when flying; however, spectacle compatibility remains an important consideration in the cockpit.

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

Pattern of refractive errors among patients at a tertiary hospital in Kathmandu.

PubMed

Rizyal, A; Ghising, R; Shrestha, R K; Kansakar, I

2011-09-01

A hospital based cross sectional study was carried out to determine the pattern of refractive errors among patients attending the out patient department, Department of Ophthalmology, Nepal Medical College Teaching Hospital. A total of 1100 patients were evaluated, (male 43.67%; female 56.33%). Simple myopic astigmatism was the most prevalent type of refractive error accounting for 27.18% followed by simple myopia (21.66%) and compound myopic astigmatism (19.48%). Simple hypermetropia (15.03%) and mixed astigmatism (4.3%) were also noted. Simple myopia was prevalent among the younger age group in the first to third decades, whereas hypermetropia was seen in the older patients in the third to fifth decades.

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 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.

The Effect of Age, Accommodation and Refractive Error on the Adult Human Eye

PubMed Central

Richdale, Kathryn; Bullimore, Mark A.; Sinnott, Loraine T.; Zadnik, Karla

2015-01-01

Purpose To quantify changes in ocular dimensions associated with age, refractive error, and accommodative response, in vivo, in 30- to 50-year-old human subjects. Methods The right eyes of 91 adults were examined using ultrasonography, phakometry, keratometry, pachymetry, interferometry, anterior segment optical coherence tomography, and high resolution magnetic resonance imaging. Accommodation was measured subjectively with a push-up test and objectively using open-field autorefraction. Regression analyses were used to assess differences in ocular parameters with age, refractive error and accommodation. Results With age, crystalline lens thickness increased (0.03 mm/yr), anterior lens curvature steepened (0.11 mm/yr), anterior chamber depth decreased (0.02 mm/y) and lens equivalent refractive index decreased (0.001 /y) (all p < 0.01). With increasing myopia, there were significant increases in axial length (0.37 mm/D), vitreous chamber depth (0.34 mm/D), vitreous chamber height (0.09 mm/D) and ciliary muscle ring diameter (0.10 mm/D) (all p < 0.05). Increasing myopia was also associated with steepening of both the cornea (0.16 mm/D) and anterior lens surface (0.011 mm/D) (both p < 0.04). With accommodation, the ciliary muscle ring diameter decreased (0.08 mm/D), and the muscle thinned posteriorly (0.008 mm/D), allowing the lens to shorten equatorially (0.07 mm/D) and thicken axially (0.06 mm/D) (all p < 0.03). Conclusions Refractive error is significantly correlated with not only the axial dimensions, but the anterior equatorial dimension of the adult eye. Further testing and development of accommodating intraocular lenses should account for differences in patients’ preoperative refractive error. PMID:26703933

Prevalence and associated risk factors of undercorrected refractive errors among people with diabetes in Shanghai.

PubMed

Zhu, Mengjun; Tong, Xiaowei; Zhao, Rong; He, Xiangui; Zhao, Huijuan; Zhu, Jianfeng

2017-11-28

To investigate the prevalence and risk factors of undercorrected refractive error (URE) among people with diabetes in the Baoshan District of Shanghai, where data for undercorrected refractive error are limited. The study was a population-based survey of 649 persons (aged 60 years or older) with diabetes in Baoshan, Shanghai in 2009. One copy of the questionnaire was completed for each subject. Examinations included a standardized refraction and measurement of presenting and best-corrected visual acuity (BCVA), tonometry, slit lamp biomicroscopy, and fundus photography. The calculated age-standardized prevalence rate of URE was 16.63% (95% confidence interval [CI] 13.76-19.49). For visual impairment subjects (presenting vision worse than 20/40 in the better eye), the prevalence of URE was up to 61.11%, and 75.93% of subjects could achieve visual acuity improvement by at least one line using appropriate spectacles. Under multiple logistic regression analysis, older age, female gender, non-farmer, increasing degree of myopia, lens opacities status, diabetic retinopathy (DR), body mass index (BMI) index lower than normal, and poor glycaemic control were associated with higher URE levels. Wearing distance eyeglasses was a protective factor for URE. The undercorrected refractive error in diabetic adults was high in Shanghai. Health education and regular refractive assessment are needed for diabetic adults. Persons with diabetes should be more aware that poor vision is often correctable, especially for those with risk factors.

Genome-wide meta-analyses of multiancestry cohorts identify multiple new susceptibility loci for refractive error and myopia.

PubMed

Verhoeven, Virginie J M; Hysi, Pirro G; Wojciechowski, Robert; Fan, Qiao; Guggenheim, Jeremy A; Höhn, René; MacGregor, Stuart; Hewitt, Alex W; Nag, Abhishek; Cheng, Ching-Yu; Yonova-Doing, Ekaterina; Zhou, Xin; Ikram, M Kamran; Buitendijk, Gabriëlle H S; McMahon, George; Kemp, John P; Pourcain, Beate St; Simpson, Claire L; Mäkelä, Kari-Matti; Lehtimäki, Terho; Kähönen, Mika; Paterson, Andrew D; Hosseini, S Mohsen; Wong, Hoi Suen; Xu, Liang; Jonas, Jost B; Pärssinen, Olavi; Wedenoja, Juho; Yip, Shea Ping; Ho, Daniel W H; Pang, Chi Pui; Chen, Li Jia; Burdon, Kathryn P; Craig, Jamie E; Klein, Barbara E K; Klein, Ronald; Haller, Toomas; Metspalu, Andres; Khor, Chiea-Chuen; Tai, E-Shyong; Aung, Tin; Vithana, Eranga; Tay, Wan-Ting; Barathi, Veluchamy A; Chen, Peng; Li, Ruoying; Liao, Jiemin; Zheng, Yingfeng; Ong, Rick T; Döring, Angela; Evans, David M; Timpson, Nicholas J; Verkerk, Annemieke J M H; Meitinger, Thomas; Raitakari, Olli; Hawthorne, Felicia; Spector, Tim D; Karssen, Lennart C; Pirastu, Mario; Murgia, Federico; Ang, Wei; Mishra, Aniket; Montgomery, Grant W; Pennell, Craig E; Cumberland, Phillippa M; Cotlarciuc, Ioana; Mitchell, Paul; Wang, Jie Jin; Schache, Maria; Janmahasatian, Sarayut; Janmahasathian, Sarayut; Igo, Robert P; Lass, Jonathan H; Chew, Emily; Iyengar, Sudha K; Gorgels, Theo G M F; Rudan, Igor; Hayward, Caroline; Wright, Alan F; Polasek, Ozren; Vatavuk, Zoran; Wilson, James F; Fleck, Brian; Zeller, Tanja; Mirshahi, Alireza; Müller, Christian; Uitterlinden, André G; Rivadeneira, Fernando; Vingerling, Johannes R; Hofman, Albert; Oostra, Ben A; Amin, Najaf; Bergen, Arthur A B; Teo, Yik-Ying; Rahi, Jugnoo S; Vitart, Veronique; Williams, Cathy; Baird, Paul N; Wong, Tien-Yin; Oexle, Konrad; Pfeiffer, Norbert; Mackey, David A; Young, Terri L; van Duijn, Cornelia M; Saw, Seang-Mei; Bailey-Wilson, Joan E; Stambolian, Dwight; Klaver, Caroline C; Hammond, Christopher J

2013-03-01

Refractive error is the most common eye disorder worldwide and is a prominent cause of blindness. Myopia affects over 30% of Western populations and up to 80% of Asians. The CREAM consortium conducted genome-wide meta-analyses, including 37,382 individuals from 27 studies of European ancestry and 8,376 from 5 Asian cohorts. We identified 16 new loci for refractive error in individuals of European ancestry, of which 8 were shared with Asians. Combined analysis identified 8 additional associated loci. The new loci include candidate genes with functions in neurotransmission (GRIA4), ion transport (KCNQ5), retinoic acid metabolism (RDH5), extracellular matrix remodeling (LAMA2 and BMP2) and eye development (SIX6 and PRSS56). We also confirmed previously reported associations with GJD2 and RASGRF1. Risk score analysis using associated SNPs showed a tenfold increased risk of myopia for individuals carrying the highest genetic load. Our results, based on a large meta-analysis across independent multiancestry studies, considerably advance understanding of the mechanisms involved in refractive error and myopia.

Outcomes of LASIK and PRK in previous penetrating corneal transplant recipients.

PubMed

Kovoor, Timmy A; Mohamed, Engy; Cavanagh, H Dwight; Bowman, R Wayne

2009-09-01

To evaluate the safety and efficacy of excimer laser refractive surgery in correcting refractive error in eyes that have undergone previous penetrating keratoplasty (PK). Twenty-three keratorefractive procedures on 16 eyes from 16 consecutive subjects were evaluated between 2002 and 2008. Each patient presented a previous history of a PK with subsequent postoperative myopia and astigmatism. Keratometric value, manifest refraction, best-corrected visual acuity, uncorrected visual acuity, and complications were determined. There were a total of 14 photorefractive keratectomy (PRK) procedures performed on 11 eyes and 9 laser in situ keratomileusis (LASIK) procedures performed on 5 eyes. In the PRK group, the preoperative post-PK manifest refractive spherical equivalent and cylindrical error were -6.22 +/- 6.23 diopter and 5.23 +/- 2.26 D, respectively. The PRK postoperative manifest refractive spherical equivalent and cylindrical error were -3.61 +/- 4.23 D (P=0.25) and 3.21 +/- 1.78 D (P=0.02), respectively. In the LASIK group, the preoperative post-PK manifest refractive spherical equivalent and cylindrical error were -3.05 +/- 3.29 D and 4.11 +/- 2.38 D, respectively. The LASIK postoperative manifest refractive spherical equivalent and cylindrical error were -1.51 +/- 2.02 D (P=0.24) and 2.08 +/- 1.26 D (P=0.03), respectively. There was a 2-line or greater improvement of uncorrected visual acuity in 8 of the 14 PRK treatments and 5 of the 9 LASIK treatments. There were two episodes of acute graft rejection. One of the episodes resolved with topical and oral corticosteroids, and the other episode required a repeat corneal transplantation. PRK and LASIK are effective tools in reducing surgically induced astigmatism after penetrating corneal transplantation in most patients in this case series. The reduction of astigmatism may allow improved contact lens or spectacle fitting to achieve best-corrected binocular visual acuity.

Influence of uncorrected refractive error and unmet refractive error on visual impairment in a Brazilian population.

PubMed

Ferraz, Fabio H; Corrente, José E; Opromolla, Paula; Schellini, Silvana A

2014-06-25

The World Health Organization (WHO) definitions of blindness and visual impairment are widely based on best-corrected visual acuity excluding uncorrected refractive errors (URE) as a visual impairment cause. Recently, URE was included as a cause of visual impairment, thus emphasizing the burden of visual impairment due to refractive error (RE) worldwide is substantially higher. The purpose of the present study is to determine the reversal of visual impairment and blindness in the population correcting RE and possible associations between RE and individual characteristics. A cross-sectional study was conducted in nine counties of the western region of state of São Paulo, using systematic and random sampling of households between March 2004 and July 2005. Individuals aged more than 1 year old were included and were evaluated for demographic data, eye complaints, history, and eye exam, including no corrected visual acuity (NCVA), best corrected vision acuity (BCVA), automatic and manual refractive examination. The definition adopted for URE was applied to individuals with NCVA > 0.15 logMAR and BCVA ≤ 0.15 logMAR after refractive correction and unmet refractive error (UREN), individuals who had visual impairment or blindness (NCVA > 0.5 logMAR) and BCVA ≤ 0.5 logMAR after optical correction. A total of 70.2% of subjects had normal NCVA. URE was detected in 13.8%. Prevalence of 4.6% of optically reversible low vision and 1.8% of blindness reversible by optical correction were found. UREN was detected in 6.5% of individuals, more frequently observed in women over the age of 50 and in higher RE carriers. Visual impairment related to eye diseases is not reversible with spectacles. Using multivariate analysis, associations between URE and UREN with regard to sex, age and RE was observed. RE is an important cause of reversible blindness and low vision in the Brazilian population.

Influence of uncorrected refractive error and unmet refractive error on visual impairment in a Brazilian population

PubMed Central

2014-01-01

Background The World Health Organization (WHO) definitions of blindness and visual impairment are widely based on best-corrected visual acuity excluding uncorrected refractive errors (URE) as a visual impairment cause. Recently, URE was included as a cause of visual impairment, thus emphasizing the burden of visual impairment due to refractive error (RE) worldwide is substantially higher. The purpose of the present study is to determine the reversal of visual impairment and blindness in the population correcting RE and possible associations between RE and individual characteristics. Methods A cross-sectional study was conducted in nine counties of the western region of state of São Paulo, using systematic and random sampling of households between March 2004 and July 2005. Individuals aged more than 1 year old were included and were evaluated for demographic data, eye complaints, history, and eye exam, including no corrected visual acuity (NCVA), best corrected vision acuity (BCVA), automatic and manual refractive examination. The definition adopted for URE was applied to individuals with NCVA > 0.15 logMAR and BCVA ≤ 0.15 logMAR after refractive correction and unmet refractive error (UREN), individuals who had visual impairment or blindness (NCVA > 0.5 logMAR) and BCVA ≤ 0.5 logMAR after optical correction. Results A total of 70.2% of subjects had normal NCVA. URE was detected in 13.8%. Prevalence of 4.6% of optically reversible low vision and 1.8% of blindness reversible by optical correction were found. UREN was detected in 6.5% of individuals, more frequently observed in women over the age of 50 and in higher RE carriers. Visual impairment related to eye diseases is not reversible with spectacles. Using multivariate analysis, associations between URE and UREN with regard to sex, age and RE was observed. Conclusion RE is an important cause of reversible blindness and low vision in the Brazilian population. PMID:24965318

Screening athletes with Down syndrome for ocular disease.

PubMed

Gutstein, Walter; Sinclair, Stephen H; North, Rachel V; Bekiroglu, N

2010-02-01

Persons with Down syndrome are well known to have a high prevalence of vision and eye health problems, many of which are undetected or untreated primarily because of infrequent ocular examinations. Public screening programs, directed toward the pediatric population, have become more popular and commonly use letter or symbol charts. This study compares 2 vision screening methods, the Lea Symbol chart and a newly developed interactive computer program, the Vimetrics Central Vision Analyzer (CVA), in their ability to identify ocular disease in the Down syndrome population. Athletes with Down syndrome participating in the European Special Olympics underwent an ocular screening including history, auto-refraction, colour vision assessment, stereopsis assessment, motility assessment, pupil reactivity, and tonometry testing, as well as anterior segment and fundus examinations to evaluate for ocular disease. Visual acuity was tested with the Lea chart and CVA to evaluate these as screening tests for detecting ocular disease as well as significant, uncorrected refractive errors. Among the 91 athletes that presented to the screening, 79 (158 eyes) were sufficiently cooperative for the examination to be completed. Mean age was 26 years +/-10.8 SD. Significant, uncorrected refractive errors (>/=1.00 spherical equivalent) were detected in 28 (18%) eyes and ocular pathology in 51 (32%) eyes. The Lea chart sensitivity and specificity were 43% and 74%, respectively, for detecting ocular pathology and 58% and 100% for detecting uncorrected refractive errors. The CVA sensitivity and specificity were 70% and 86% for detecting pathology and 71% and 100% for detecting uncorrected refractive errors. This study confirmed the findings of prior studies in identifying a significant presence of uncorrected refractive errors and ocular pathology in the Down syndrome population. Screening with the Lea symbol chart found borderline sufficient sensitivity and specificity for the test to be used for screening in this population. The better sensitivity and specificity of the CVA, if adjusted normative values are utilized, appear to make this test sufficient for testing Down syndrome children for identifying both refractive errors and ocular pathology. Copyright 2010 American Optometric Association. Published by Elsevier Inc. All rights reserved.

An alternative clinical routine for subjective refraction based on power vectors with trial frames.

PubMed

María Revert, Antonia; Conversa, Maria Amparo; Albarrán Diego, César; Micó, Vicente

2017-01-01

Subjective refraction determines the final point of refractive error assessment in most clinical environments and its foundations have remained unchanged for decades. The purpose of this paper is to compare the results obtained when monocular subjective refraction is assessed in trial frames by a new clinical procedure based on a pure power vector interpretation with conventional clinical refraction procedures. An alternative clinical routine is described that uses power vector interpretation with implementation in trial frames. Refractive error is determined in terms of: (i) the spherical equivalent (M component), and (ii) a pair of Jackson Crossed Cylinder lenses oriented at 0°/90° (J 0 component) and 45°/135° (J 45 component) for determination of astigmatism. This vector subjective refraction result (VR) is compared separately for right and left eyes of 25 subjects (mean age, 35 ± 4 years) against conventional sphero-cylindrical subjective refraction (RX) using a phoropter. The VR procedure was applied with both conventional tumbling E optotypes (VR1) and modified optotypes with oblique orientation (VR2). Bland-Altman plots and intra-class correlation coefficient showed good agreement between VR, and RX (with coefficient values above 0.82) and anova showed no significant differences in any of the power vector components between RX and VR. VR1 and VR2 procedure results were similar (p ≥ 0.77). The proposed routine determines the three components of refractive error in power vector notation [M, J 0 , J 45 ], with a refraction time similar to the one used in conventional subjective procedures. The proposed routine could be helpful for inexperienced clinicians and for experienced clinicians in those cases where it is difficult to get a valid starting point for conventional RX (irregular corneas, media opacities, etc.) and for refractive situations/places with inadequate refractive facilities/equipment. © 2016 The Authors Ophthalmic & Physiological Optics © 2016 The College of Optometrists.

The prevalence of refractive errors among adults in the United States, Western Europe, and Australia.

PubMed

Kempen, John H; Mitchell, Paul; Lee, Kristine E; Tielsch, James M; Broman, Aimee T; Taylor, Hugh R; Ikram, M Kamran; Congdon, Nathan G; O'Colmain, Benita J

2004-04-01

To estimate the prevalence of refractive errors in persons 40 years and older. Counts of persons with phakic eyes with and without spherical equivalent refractive error in the worse eye of +3 diopters (D) or greater, -1 D or less, and -5 D or less were obtained from population-based eye surveys in strata of gender, race/ethnicity, and 5-year age intervals. Pooled age-, gender-, and race/ethnicity-specific rates for each refractive error were applied to the corresponding stratum-specific US, Western European, and Australian populations (years 2000 and projected 2020). Six studies provided data from 29 281 persons. In the US, Western European, and Australian year 2000 populations 40 years or older, the estimated crude prevalence for hyperopia of +3 D or greater was 9.9%, 11.6%, and 5.8%, respectively (11.8 million, 21.6 million, and 0.47 million persons). For myopia of -1 D or less, the estimated crude prevalence was 25.4%, 26.6%, and 16.4% (30.4 million, 49.6 million, and 1.3 million persons), respectively, of whom 4.5%, 4.6%, and 2.8% (5.3 million, 8.5 million, and 0.23 million persons), respectively, had myopia of -5 D or less. Projected prevalence rates in 2020 were similar. Refractive errors affect approximately one third of persons 40 years or older in the United States and Western Europe, and one fifth of Australians in this age group.

Vision-Enhancing Interventions in Nursing Home Residents and Their Short-Term Impact on Physical and Cognitive Function

PubMed Central

Elliott, Amanda F.; McGwin, Gerald; Owsley, Cynthia

2009-01-01

OBJECTIVE To evaluate the effect of vision-enhancing interventions (i.e., cataract surgery or refractive error correction) on physical function and cognitive status in nursing home residents. DESIGN Longitudinal cohort study. SETTING Seventeen nursing homes in Birmingham, AL. PARTICIPANTS A total of 187 English-speaking older adults (>55 years of age). INTERVENTION Participants took part in one of two vision-enhancing interventions: cataract surgery or refractive error correction. Each group was compared against a control group (persons eligible for but who declined cataract surgery, or who received delayed correction of refractive error). MEASUREMENTS Physical function (i.e., ability to perform activities of daily living and mobility) was assessed with a series of self-report and certified nursing assistant ratings at baseline and at 2 months for the refractive error correction group, and at 4 months for the cataract surgery group. The Mini Mental State Exam was also administered. RESULTS No significant differences existed within or between groups from baseline to follow-up on any of the measures of physical function. Mental status scores significantly declined from baseline to follow-up for both the immediate (p= 0.05) and delayed (p< 0.02) refractive error correction groups and for the cataract surgery control group (p= 0.05). CONCLUSION Vision-enhancing interventions did not lead to short-term improvements in physical functioning or cognitive status in this sample of elderly nursing home residents. PMID:19170783

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

MONOCULAR DIPLOPIA DUE TO SPHEROCYLINDRICAL REFRACTIVE ERRORS (AN AMERICAN OPHTHALMOLOGICAL SOCIETY THESIS)

PubMed Central

Archer, Steven M.

2007-01-01

Purpose Ordinary spherocylindrical refractive errors have been recognized as a cause of monocular diplopia for over a century, yet explanation of this phenomenon using geometrical optics has remained problematic. This study tests the hypothesis that the diffraction theory treatment of refractive errors will provide a more satisfactory explanation of monocular diplopia. Methods Diffraction theory calculations were carried out for modulation transfer functions, point spread functions, and line spread functions under conditions of defocus, astigmatism, and mixed spherocylindrical refractive errors. Defocused photographs of inked and projected black lines were made to demonstrate the predicted consequences of the theoretical calculations. Results For certain amounts of defocus, line spread functions resulting from spherical defocus are predicted to have a bimodal intensity distribution that could provide the basis for diplopia with line targets. Multimodal intensity distributions are predicted in point spread functions and provide a basis for diplopia or polyopia of point targets under conditions of astigmatism. The predicted doubling effect is evident in defocused photographs of black lines, but the effect is not as robust as the subjective experience of monocular diplopia. Conclusions Monocular diplopia due to ordinary refractive errors can be predicted from diffraction theory. Higher-order aberrations—such as spherical aberration—are not necessary but may, under some circumstances, enhance the features of monocular diplopia. The physical basis for monocular diplopia is relatively subtle, and enhancement by neural processing is probably needed to account for the robustness of the percept. PMID:18427616

Accuracy of noncycloplegic refraction performed at school screening camps.

PubMed

Khurana, Rolli; Tibrewal, Shailja; Ganesh, Suma; Tarkar, Rajoo; Nguyen, Phuong Thi Thanh; Siddiqui, Zeeshan; Dasgupta, Shantanu

2018-06-01

The aim of this study was to compare noncycloplegic refraction performed in school camp with that performed in eye clinic in children aged 6-16 years. A prospective study of children with unaided vision <0.2 LogMAR who underwent noncycloplegic retinoscopy (NCR) and subjective refraction (SR) in camp and subsequently in eye clinic between February and March 2017 was performed. A masked optometrist performed refractions in both settings. The agreement between refraction values obtained at both settings was compared using the Bland-Altman analysis. A total of 217 eyes were included in this study. Between the school camp and eye clinic, the mean absolute error ± standard deviation in spherical equivalent (SE) of NCR was 0.33 ± 0.4D and that of SR was 0.26 ± 0.5D. The limits of agreement for NCR were +0.91D to - 1.09D and for SR was +1.15D to -1.06D. The mean absolute error in SE was ≤0.5D in 92.62% eyes (95% confidence interval 88%-95%). A certain degree of variability exists between noncycloplegic refraction done in school camps and eye clinic. It was found to be accurate within 0.5D of SE in 92.62% eyes for refractive errors up to 4.5D of myopia, 3D of cylinder, and 1.5D of hyperopia.

Refractive and Biometric Outcomes in Patients with Retinopathy of Prematurity Treated with Intravitreal Injection of Ranibizumab as Compared with Bevacizumab: A Clinical Study of Correction at Three Years of Age.

PubMed

Chen, Yen-Chih; Chen, San-Ni; Yang, Benjamin Chi-Lan; Lee, Kun-Hsien; Chuang, Chih-Chun; Cheng, Chieh-Yin

2018-01-01

To compare refractive and biometric outcomes in patients with type 1 retinopathy of prematurity (ROP) treated with intravitreal injection of ranibizumab (IVR) versus bevacizumab (IVB), at a corrected age of 3 years. A retrospective case series compared cycloplegic refractive statuses and biometric statuses in patients who received either IVR or IVB for type 1 ROP, from April 2011 to April 2014. A total of 62 eyes (33 patients) with type 1 ROP were evaluated (26 eyes in 13 IVR patients and 36 eyes in 20 IVB patients). There were no differences in birth statuses including gestational age and birth body weight between the two groups. The prevalence of refractive error greater than 1 D was higher in the IVB group ( p = 0.03), and there was a higher prevalence of high myopia (<-5.0 D, p = 0.03) in the IVB group. Comparisons in biometric finding showed that IVB patients had shallower anterior chamber depth ( p = 0.01). Both IVR and IVB showed low refractive errors, even followed at the corrected age of 3 years. No difference was noted between the two groups in refractive statuses. However, IVB was associated with shallower anterior chamber and higher prevalence of refractive error at the corrected age of 3 years. This trial is registered with NCT03334513.

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.

Performance of the SRK/T formula using A-Scan ultrasound biometry after phacoemulsification in eyes with short and long axial lengths.

PubMed

Karabela, Yunus; Eliacik, Mustafa; Kaya, Faruk

2016-07-08

The SRK/T formula is one of the third generation IOL calculation formulas. The purpose of this study was to evaluate the performance of the SRK/T formula in predicting a target refraction ±1.0D in short and long eyes using ultrasound biometry after phacoemulsification. The present study was a retrospective analysis, which included 38 eyes with an AL < 22.0 mm (short AL), and 62 eyes ≥24.6 mm (long AL) that underwent uncomplicated phacoemulsification. Preoperative AL was measured by ultrasound biometry and SRK/T formula was used for IOL calculation. Three different IOLs were implanted in the capsular bag. The prediction error was defined as the difference between the achieved postoperative refraction, and attempted predicted target refraction. Statistical analysis was performed with SPSS V21. In short ALs, the mean age was 65.13 ± 9.49 year, the mean AL was 21.55 ± 0.45 mm, the mean K1 and K2 were 45.76 ± 1.77D and 46.09 ± 1.61D, the mean IOL power was 23.96 ± 1.92D, the mean attempted (predicted) value was 0.07 ± 0.26D, the mean achieved value was 0.07 ± 0.63 D, the mean PE was 0.01 ± 0.60D, and the MAE was 0.51 ± 0.31D. A significant positive relationship with AL and K1, K2, IOL power and a strong negative relationship with PE and achieved postoperative was found. In long ALs, the mean age was 64.05 ± 7.31 year, the mean AL was 25.77 ± 1.64 mm, the mean K1 and K2 were 42.20 ± 1.57D and 42.17 ± 1.68D, the mean IOL power was 15.79 ± 5.17D, the mean attempted value was -0.434 ± 0.315D, the mean achieved value was -0.42 ± 0.96D, the mean PE was -0.004 ± 0.93D, the MAE was 0.68 ± 0.62D. A significant positive relationship with AL and K1, K2 and a significant positive relationship with PE and achieved value, otherwise a negative relationship with AL and IOL power was found. There was a little tendency towards hyperopic for short ALs and myopic for long ALs. The majority of eyes (94.74 %) for short ALs and (70.97 %) for long ALs were within ±1 D of the predicted refractive error. No significant relationship with PE and IOL types, AL, K1, K2, IOL power, and attempted value, besides with MAE and AL, K1, K2, age, attempted, achieved value were found in both groups. The SRK/T formula performs well and shows good predictability in eyes with short and long axial lengths.

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.

Knowledge, attitude and associated factors among primary school teachers regarding refractive error in school children in Gondar city, Northwest Ethiopia.

PubMed

Alemayehu, Abiy Maru; Belete, Gizchewu Tilahun; Adimassu, Nebiyat Feleke

2018-01-01

Refractive error is an important cause of correctable visual impairment in the worldwide with a global distribution of 1.75% to 20.7% among schoolchildren. Teacher's knowledge about refractive error play an important role in encouraging students to seek treatment that helps in reducing the burden of visual impairment. To determine knowledge, attitude and associated factors among primary school teachers regarding refractive error in school children in Gondar city. Institution based cross-sectional study was conducted on 565 primary school teachers in Gondar city using pretested and structured self-administered questionnaire. For processing and analysis, SPSS version 20 was used and variables which had a P value of <0.05 in the multivariable analysis were considered as statistically significant. A total of 565 study subjects were participated in this study with a mean age of 42.05 ± 12.01 years. Of these study participants 55.9% (95% CI: 51.9, 59.8) had good knowledge and 57.2% (95% CI: 52.9, 61.4) had favorable attitude towards refractive error. History of spectacle use [AOR = 2.13 (95% CI: 1.32, 3.43)], history of eye examination [AOR = 1.67 (95% CI: 1.19, 2.34)], training on eye health [AOR = 1.94 (95% CI; 1.09, 3.43)] and 11-20 years of experience [AOR = 2.53 (95% CI: 1.18, 5.43)] were positively associated with knowledge. Whereas being male [AOR = 2.03 (95% CI: 1.37, 3.01)], older age [AOR = 3.05 (95% CI: 1.07, 8.72)], 31-40 years of experience [AOR = 0.23 (95% CI: 0.07, 0.72)], private school type [AOR = 1.76 (95% CI: 1.06, 2.93)] and 5th -8th teaching category [AOR = 1.54 (95% CI: 1.05, 2.24)] were associated with attitude. Knowledge and attitude of study subjects were low which needs training of teachers about the refractive error.

The role of luminance and chromatic cues in emmetropisation.

PubMed

Rucker, Frances J

2013-05-01

At birth most, but not all eyes, are hyperopic. Over the course of the first few years of life the refraction gradually becomes close to zero through a process called emmetropisation. This process is not thought to require accommodation, though a lag of accommodation has been implicated in myopia development, suggesting that the accuracy of accommodation is an important factor. This review will cover research on accommodation and emmetropisation that relates to the ability of the eye to use colour and luminance cues to guide the responses. There are three ways in which changes in luminance and colour contrast could provide cues: (1) The eye could maximize luminance contrast. Monochromatic light experiments have shown that the human eye can accommodate and animal eyes can emmetropise using changes in luminance contrast alone. However, by reducing the effectiveness of luminance cues in monochromatic and white light by introducing astigmatism, or by reducing light intensity, investigators have revealed that the eye also uses colour cues in emmetropisation. (2) The eye could compare relative cone contrast to derive the sign of defocus information from colour cues. Experiments involving simulations of the retinal image with defocus have shown that relative cone contrast can provide colour cues for defocus in accommodation and emmetropisation. In the myopic simulation the contrast of the red component of a sinusoidal grating was higher than that of the green and blue component and this caused relaxation of accommodation and reduced eye growth. In the hyperopic simulation the contrast of the blue component was higher than that of the green and red components and this caused increased accommodation and increased eye growth. (3) The eye could compare the change in luminance and colour contrast as the eye changes focus. An experiment has shown that changes in colour or luminance contrast can provide cues for defocus in emmetropisation. When the eye is exposed to colour flicker the eye grows almost twice as much, and becomes more myopic, compared to when the eye is exposed to luminance flicker. Neural responses of the luminance and colour mechanisms direct accommodation and emmetropisation mechanisms to different focal planes. Therefore, it is likely that the set point of refraction and accommodation is dependent on the sensitivity of the eye to changes in spatial and temporal, colour and luminance contrast. Ophthalmic & Physiological Optics © 2013 The College of Optometrists.

Spectacle wearing in children randomised to ready-made or custom spectacles, and potential cost savings to programmes: study protocol for a randomised controlled trial.

PubMed

Morjaria, Priya; Murali, Kaushik; Evans, Jennifer; Gilbert, Clare

2016-01-19

Uncorrected refractive errors are the commonest cause of visual impairment in children, with myopia being the most frequent type. Myopia usually starts around 9 years of age and progresses throughout adolescence. Hyperopia usually affects younger children, and astigmatism affects all age groups. Many children have a combination of myopia and astigmatism. To correct refractive errors, the type and degree of refractive error are measured and appropriate corrective lenses prescribed and dispensed in the spectacle frame of choice. Custom spectacles (that is, with the correction specifically required for that individual) are required if astigmatism is present, and/or the refractive error differs between eyes. Spectacles without astigmatic correction and where the refractive error is the same in both eyes are straightforward to dispense. These are known as 'ready-made' spectacles. High-quality spectacles of this type can be produced in high volume at an extremely low cost. Although spectacle correction improves visual function, a high proportion of children do not wear their spectacles for a variety of reasons. The aim of this study is to compare spectacle wear at 3-4 months amongst school children aged 11 to 15 years who have significant, simple uncorrected refractive error randomised to ready-made or custom spectacles of equivalent quality, and to evaluate cost savings to programmes. The study will take place in urban and semi-urban government schools in Bangalore, India. The hypothesis is that similar proportions of children randomised to ready-made or custom spectacles will be wearing their spectacles at 3-4 months. The trial is a randomised, non-inferiority, double masked clinical trial of children with simple uncorrected refractive errors. After screening, children will be randomised to ready-made or custom spectacles. Children will choose their preferred frame design. After 3-4 months the children will be followed up to assess spectacle wear. Ready-made spectacles have benefits for providers as well as parents and children, as a wide range of prescriptions and frame types can be taken to schools and dispensed immediately. In contrast, custom spectacles have to be individually made up in optical laboratories, and taken back to the school and given to the correct child. ISRCTN14715120 (Controlled-Trials.com) Date registered: 04 February 2015.

Screening for visual impairment: Outcome among schoolchildren in a rural area of Delhi

PubMed Central

Rustagi, Neeti; Uppal, Yogesh; Taneja, Devender K

2012-01-01

Background: Uncorrected refractive errors are the main cause of vision impairment in school-aged children. The current study focuses on the effectiveness of school eye screening in correcting refractive errors. Objectives: 1. To study the magnitude of visual impairment among school children. 2. To assess the compliance of students for refraction testing, procurement and use of spectacles. Materials and Methods: An intervention study was conducted in schools of the north- west district of Delhi, in the rural field practice area of a medical college. Students studying in five government schools in the field practice area were chosen as the study subjects. Results: Out of 1123 students enrolled, 1075 (95.7%) students were screened for refractive errors. Low vision (visual acuity < 20/60) in the better eye was observed in 31 (2.9%) children and blindness (visual acuity <20/200) in 10 (0.9%) children. Compliance with referral for refraction was very low as only 51 (41.5%) out of 123 students could be tested for refraction. Out of 48 students, 34 (70.8%) procured spectacles from family resources but its regular use was found among only 10 (29.4%) students. The poor compliance among students stems out of various myths and perceptions regarding use of spectacles prevalent in the community. Conclusion: Refractive error is an important cause of avoidable blindness among rural school children. Behavior change communication among rural masses by spreading awareness about eye health and conducting operational research at school and community level to involve parent's teachers associations and senior students to motivate students for use of spectacles may improve utilization of existing eye health services in rural areas. PMID:22569381

Piggyback intraocular lens implantation to correct pseudophakic refractive error after segmental multifocal intraocular lens implantation.

PubMed

Venter, Jan A; Oberholster, Andre; Schallhorn, Steven C; Pelouskova, Martina

2014-04-01

To evaluate refractive and visual outcomes of secondary piggyback intraocular lens implantation in patients diagnosed as having residual ametropia following segmental multifocal lens implantation. Data of 80 pseudophakic eyes with ametropia that underwent Sulcoflex aspheric 653L intraocular lens implantation (Rayner Intraocular Lenses Ltd., East Sussex, United Kingdom) to correct residual refractive error were analyzed. All eyes previously had in-the-bag zonal refractive multifocal intraocular lens implantation (Lentis Mplus MF30, models LS-312 and LS-313; Oculentis GmbH, Berlin, Germany) and required residual refractive error correction. Outcome measurements included uncorrected distance visual acuity, corrected distance visual acuity, uncorrected near visual acuity, distance-corrected near visual acuity, manifest refraction, and complications. One-year data are presented in this study. The mean spherical equivalent ranged from -1.75 to +3.25 diopters (D) preoperatively (mean: +0.58 ± 1.15 D) and reduced to -1.25 to +0.50 D (mean: -0.14 ± 0.28 D; P < .01). Postoperatively, 93.8% of eyes were within ±0.50 D and 98.8% were within ±1.00 D of emmetropia. The mean uncorrected distance visual acuity improved significantly from 0.28 ± 0.16 to 0.01 ± 0.10 logMAR and 78.8% of eyes achieved 6/6 (Snellen 20/20) or better postoperatively. The mean uncorrected near visual acuity changed from 0.43 ± 0.28 to 0.19 ± 0.15 logMAR. There was no significant change in corrected distance visual acuity or distance-corrected near visual acuity. No serious intraoperative or postoperative complications requiring secondary intraocular lens removal occurred. Sulcoflex lenses proved to be a predictable and safe option for correcting residual refractive error in patients diagnosed as having pseudophakia. Copyright 2014, SLACK Incorporated.

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

Analysis of ionospheric refraction error corrections for GRARR systems

NASA Technical Reports Server (NTRS)

Mallinckrodt, A. J.; Parker, H. C.; Berbert, J. H.

1971-01-01

A determination is presented of the ionospheric refraction correction requirements for the Goddard range and range rate (GRARR) S-band, modified S-band, very high frequency (VHF), and modified VHF systems. The relation ships within these four systems are analyzed to show that the refraction corrections are the same for all four systems and to clarify the group and phase nature of these corrections. The analysis is simplified by recognizing that the range rate is equivalent to a carrier phase range change measurement. The equation for the range errors are given.

Intelligent Planning for Laser Refractive Surgeries

NASA Astrophysics Data System (ADS)

Wang, Wei; Yue, Yong; Elsheikh, Ahmed; Bao, Fangjun

2018-02-01

Refractive error is one of leading ophthalmic diseases for both genders all over the world. Laser refractive correction surgery, e.g., laser in-situ keratomileusis (LASIK), has been commonly used worldwide. The prediction of surgical parameters, e.g., corneal ablation depth, depends on the doctor’s experience, theoretical formula and surgery reference manual in the preoperative diagnosis. The error of prediction may present a potential surgical risk and complication. Being aware of the surgery parameters is important because these can be used to estimate a patient’s post-operative visual quality and help the surgeon plan a suitable treatment. Therefore, in this paper we discuss data mining techniques that can be utilized for the prediction of laser refractive correction surgery parameters. It can provide the surgeon with a reference for possible surgical parameters and outcomes of the patient before the laser refractive correction surgery.

Decreasing Uncorrected Refractive Error in the Classroom through a Multifactorial Pilot Intervention

ERIC Educational Resources Information Center

Kodjebacheva, Gergana; Maliski, Sally; Yu, Fei; Oelrich, Faye; Coleman, Anne L.

2014-01-01

The study assessed the effectiveness of a pilot intervention to promote the use of eyeglasses in one school in California. The intervention used a one-group pretest, posttest design. Between January and June 2011, during the intervention, all first- and second-grade children received eye evaluations and the children with refractive error received…

Eye Accommodation, Personality, and Autonomic Balance.

DTIC Science & Technology

1979-11-01

Wenger and Ellington, 1943, and by a technique introduced by Porges, 1976), refractive error (measured by dark focus, near and far points using a...focus, near and far points using a polarized vernier optometer), and introversion - extraversion (Eysenck Personality Inventory introversion...Porges, 1976), refractive error (measured by dark focus, near and far points using a polarized vernier optometer), and introversion - extraversion