Use of a hydrogel sealant in epithelial ingrowth removal after laser in situ keratomileusis.

PubMed

Ramsook, Sandhya S; Hersh, Peter S

2015-12-01

We describe 2 cases in which clinically significant epithelial ingrowth was removed by debridement and followed by the use of a hydrogel sealant (Resure) to seal the flap edge. In both cases, the epithelial ingrowth was seen after otherwise uneventful laser in situ keratomileusis retreatment. The visual outcomes were good with no recrudescence of interface epithelium. 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.

[Keratitis after laser in situ keratomileusis (LASIK). A different entity and treatment management].

PubMed

Ahmed, Shakil; Ahmed, Hassan Javed; Holm, Lars Morten

2014-12-15

Keratitis after laser in situ keratomileusis (LASIK) is rare and challenging as patients may present with mild symptoms and initial management differs significantly. Post-LASIK keratitis is usually due to gram-positive bacteria or opportunistic/atypical microorganisms located beneath the corneal flap. Due to relative protective interface location it is necessary to lift the corneal flap for cultures and antibiotic irrigation. The case report demonstrates that post-LASIK keratitis requires prompt referral to ophthalmology department as correct initial management is pivotal for good visual outcome.

Nd:YAG laser for epithelial ingrowth after laser in situ keratomileusis.

PubMed

Mohammed, Osama Ali; Mounir, Amr; Hassan, Amin Aboali; Alsmman, Alahmady Hamad; Mostafa, Engy Mohamed

2018-05-04

To evaluate the efficacy of neodymium:yttrium-aluminum-garnet (Nd:YAG) laser for treatment of epithelial ingrowth after laser in situ keratomileusis (LASIK). Fifty-eight patients with epithelial ingrowth presented to Sohag refractive center, Sohag, Egypt, between January 2015 and March 2017. Only 41 patients (18 females and 23 males, mean age: 33.4 years) involving 41 eyes were indicated for treatment by Nd:YAG laser as the rest of the eyes were only under observation. Patients with epithelial ingrowth were recognized at a mean of 6 months after primary LASIK procedure (range: 2-16 months). Four eyes had undergone previous LASIK enhancements. Four eyes had the epithelial ingrowth removed by flap lift and scrapping. The mean intensity of the spots used was 0.8 mJ with variable number of shots depending on the size and density of the epithelial ingrowth area. Twenty-eight eyes showed complete regression after one session, while the rest necessitated 2-3 sessions for complete resolution. Mean follow-up period was 8 months (range 5-12 months). Epithelial ingrowth was treated successfully in all 41 eyes. The uncorrected visual acuities were 20/20, and there was no evidence of recurrent epithelial ingrowth after 6 months with no complications reported. YAG laser is a simple, effective outpatient procedure for the management of epithelial ingrowth after LASIK.

Dry Eye Post-Laser-Assisted In Situ Keratomileusis: Major Review and Latest Updates

PubMed Central

Spierer, Oriel

2018-01-01

Dry eye is one of the most common complications occurring after laser-assisted in situ keratomileusis (LASIK), with virtually all patients experiencing some degree of postoperative dry eye symptoms. Enhanced understanding of the pathophysiology and mechanism of dry eye development in addition to preoperative screening of patients who are prone to dry eye is essential for better patient satisfaction and for improving short-term visual outcome postoperatively. This article reviews the latest studies published on LASIK-associated dry eye, including epidemiology, pathophysiology, risk factors, preoperative assessment, and management. PMID:29619255

Diplopia after laser in situ keratomileusis (LASIK) in a patient with a history of strabismus.

PubMed

Heinmiller, Laura J; Wasserman, Barry N

2013-02-01

In patients with a history of strabismus, refractive surgery can result in decompensation of ocular alignment, with subsequent diplopia. Refractive surgery in the management of strabismus has been described, although it remains controversial. We present a young adult with past history of strabismus surgery and new-onset diplopia after refractive surgery. Binocular diplopia was treated surgically with laser in situ keratomileusis. Copyright © 2013 American Association for Pediatric Ophthalmology and Strabismus. Published by Mosby, Inc. All rights reserved.

Femtosecond Laser Flap Creation for Laser In Situ Keratomileusis in the Setting of Previous Radial Keratotomy.

PubMed

Rush, Sloan W; Rush, Ryan B

2015-01-01

The aim of the study was to report the outcomes of laser in situ keratomileusis (LASIK) in subjects with previous radial keratotomy (RK) using a novel femtosecond laser setting on a proprietary femtosecond laser platform. This was a retrospective, consecutive chart review of patients at a single private practice institution. The medical records of 16 eyes of 8 subjects who underwent femtosecond-assisted LASIK for consecutive hyperopia after RK were retrospectively reviewed. The preoperative characteristics, intraoperative details, and postoperative outcomes were analyzed. All 16 eyes had successful femtosecond laser flap creation without significant intraoperative or postoperative complications. Uncorrected visual acuity significantly improved postoperatively (P = 0.0142) and remained stable through the final follow-up interval at 9 to 12 months postoperatively. None of the subjects lost any lines of best spectacle-corrected visual acuity in the postoperative period. The novel femtosecond laser technique described in this study can provide a safe and effective method for patients undergoing LASIK after previous RK. Future investigations are required to further validate the findings reported in this study.

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.

Fine lattice lines on the corneal surface after laser in situ keratomileusis (LASIK).

PubMed

Carpel, E F; Carlson, K H; Shannon, S

2000-03-01

To present an example of a pattern of lines resembling fine lattice on the corneal surface subsequent to laser in situ keratomileusis (LASIK). This subtle phenomenon may be relatively common and may affect visual outcome. Case report. A 41-year-old year old man with high myopia and best-corrected visual acuity of 20/20 +2 in each eye underwent laser in situ keratomileusis (LASIK). No operative or postoperative complications occurred. No striae were evident on slit-lamp examination with direct illumination and retroillumination at the time of surgery or in the postoperative period. Postoperative uncorrected visual acuity was 20/25 with a best-corrected spectacle correction of 20/25 in both eyes. Fine lines in a lattice pattern were seen only with fluorescein dye in the precorneal tear film as areas of "negative stain" within the LASIK flap. With tear film supplementation, the lines were less evident and visual acuity improved. One year postoperatively, his uncorrected visual acuity was 20/25 in both eyes. The best-corrected spectacle visual acuity was RE: 20/20 -2, LE: 20/25. The fine lines were still present within the flap. A soft contact lens improved visual acuity to 20/20 in both eyes. Although all four puncta were occluded, he had no epiphora. Fine lines in a lattice pattern that may represent folds in the epithelium or Bowman layer may be present within the flap after LASIK and may adversely affect visual acuity. They may be visible as areas of negative stain with fluorescein dye in the precorneal tear film in the absence of any striae visible in the flap. These superficial lines have been seen more in patients with high degrees of correction and in patients with dry eye. If visual acuity is affected, it may be improved with punctal occlusion, tear supplements, or a contact lens.

Activation of Cytomegalovirus corneal endotheliitis following laser in situ keratomileusis.

PubMed

Tan, Tien-En; Cheung, Chui Ming Gemmy; Mehta, Jodhbir S

2016-11-29

A case of Cytomegalovirus (CMV) corneal endotheliitis following laser in-situ keratomileusis (LASIK) is presented. A 32-year-old man presented 3 weeks after uncomplicated myopic LASIK with unilateral LASIK flap oedema, interface fluid accumulation, keratic precipitates, anterior uveitis and raised intraocular pressure. Despite treatment with topical corticosteroids, he had 3 further recurrent episodes. Specular microscopy showed decreased endothelial cell density and aqueous humour. Polymerase chain reaction (PCR) testing was positive for CMV DNA. He was treated with topical ganciclovir and ketorolac, and the inflammation and oedema resolved. Repeat aqueous humour PCR testing was negative for CMV DNA, and he remained well at last follow-up (3 months after stopping all medications). CMV corneal endotheliitis can be reactivated after LASIK, and CMV DNA PCR of aqueous humour samples can help in definitive diagnosis. Early recognition and treatment of this condition is important to prevent permanent endothelial cell loss and corneal decompensation. 2016 BMJ Publishing Group Ltd.

Night firing range performance following photorefractive keratectomy and laser in situ keratomileusis.

PubMed

Bower, Kraig S; Burka, Jenna M; Subramanian, Prem S; Stutzman, Richard D; Mines, Michael J; Rabin, Jeff C

2006-06-01

To investigate the effect of laser refractive surgery on night weapons firing. Firing range performance was measured at baseline and postoperatively following photorefractive keratectomy and laser in situ keratomileusis. Subjects fired the M-16A2 rifle with night vision goggles (NVG) at starlight, and with iron sight (simulated dusk). Scores, before and after surgery, were compared for both conditions. No subject was able to acquire the target using iron sight without correction before surgery. After surgery, the scores without correction (95.9 +/- 4.7) matched the preoperative scores with correction (94.3 +/- 4.0; p = 0.324). Uncorrected NVG scores after surgery (96.4 +/- 3.1) exceeded the corrected scores before surgery (91.4 +/- 10.2), but this trend was not statistically significant (p = 0.063). Night weapon firing with both the iron sight and the NVG sight improved after surgery. This study supports the operational benefits of refractive surgery in the military.

Femtosecond Laser in situ Keratomileusis Flap Creation in Narrow Palpebral Fissure Eyes without Suction.

PubMed

Chang, John S M; Law, Antony K P; Ng, Jack C M; Cheng, May S Y

2017-01-01

To evaluate a surgical technique used in eyes with narrow palpebral fissure undergoing femtosecond laser flap creation without suction during laser in situ keratomileusis (LASIK). All data of 2 patient groups were collected through chart review. Group 1 consisted of 6 eyes with narrow palpebral fissure in which the suction ring was manually fixated and femtosecond laser was applied accordingly. Thirty comparison cases were randomly drawn from among eyes that underwent a standard LASIK procedure matched for age and preoperative refraction (group 2). Only 1 eye of each patient was selected to compare the refractive and visual outcomes between groups. In all group 1 eyes, the flaps were created successfully with manual fixation of the suction ring without suction. No eyes lost 2 or more lines of vision. No significant difference was found in the safety and refractive outcomes between groups. Manual fixation of the suction ring in eyes with narrow palpebral fissure without suction was feasible for flap creation during LASIK.

Peripheral Ulcerative Keratitis following Laser in situ Keratomileusis.

PubMed

Burkholder, Bryn M; Kuo, Irene C

2016-01-01

We report a case of a patient with a history of glomerulonephropathy, not disclosed prior to laser in situ keratomileusis (LASIK), who developed severe postoperative peripheral ulcerative keratitis (PUK) soon after surgery. Case report. Within a week of surgery, the patient, who had no blepharitis or ocular surface disease, also developed diffuse lamellar keratitis (DLK) that was not contiguous with the PUK. Microbiologic evaluation of the flap interface disclosed no organisms, and no epithelial ingrowth was found. Both PUK and DLK resolved with topical and oral steroid therapy, and the patient's induced refractive error improved over the 12 months following LASIK. Necrotizing keratitis has been described after LASIK surgery in patients with or without autoimmune disease. However, to our knowledge, there has been no case of PUK following LASIK. As shown by our patient's clinical course and the typical association of PUK with systemic conditions, patients with a history of atypical postinfectious sequelae may require additional preoperative counseling, vigilant postoperative monitoring, and possibly additional intervention. Because patients do not always divulge medical details, especially if an extraocular site was involved or illness occurred many years prior, this case demonstrates the importance of performing a diligent history that excludes autoimmune disorders or atypical postinfectious sequelae prior to proceeding with keratorefractive intervention.

Tear menisci after laser in situ keratomileusis with mechanical microkeratome and femtosecond laser.

PubMed

Xie, Wenjia; Zhang, Dong; Chen, Jia; Liu, Jing; Yu, Ye; Hu, Liang

2014-08-21

To investigate the effect on tear menisci after laser in situ keratomileusis (LASIK) with flap creation by either microkeratome or femtosecond laser. Sixty eyes of 30 myopes were analyzed. Fifteen patients underwent LASIK with Moria II microkeratome, and the other 15 patients with 60-KHz IntraLase femtosecond laser. Upper and lower tear meniscus parameters of height (UTMH, LTMH) and area (UTMA, LTMA) were measured by SD-OCT preoperatively and 1 week, 1 month, and 3 months postoperatively. Compared with the baseline values, all tear meniscus parameters decreased significantly at each postoperative time point (all P < 0.01) in both groups. LTMH increased significantly between 1 week and 1 month and between 1 and 3 months after surgery in the microkeratome (both P < 0.01) and femtosecond laser groups (P < 0.01, P = 0.012, respectively). There were significant increases in LTMA between 1 week and 1 month after surgery in the microkeratome group (P < 0.01) and in the femtosecond laser group (P = 0.028). There were no significant differences in UTMH, UTMA, LTMH, or LTMA between two groups. The depth of ablation was negatively correlated with the LTMA at 1 week after surgery (R = -0.256, P = 0.049) for all patients. There were no significant differences in the tear meniscus parameters between the microkeratome and femtosecond laser groups. The depth of ablation was significantly correlated with the LTMA only at 1 week after surgery. Copyright 2014 The Association for Research in Vision and Ophthalmology, Inc.

Stereoacuity changes after laser in situ keratomileusis.

PubMed

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

2015-02-01

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

Laser in situ keratomileusis for high hyperopia with corneal vertex centration and asymmetric offset.

PubMed

de Ortueta, Diego; Arba-Mosquera, Sam

2017-03-10

To investigate refractive outcomes and induction of corneal higher order aberrations (HOA) in eyes that underwent laser-assisted in situ keratomileusis (LASIK) for high hyperopia correction using an aberration neutral profile with corneal vertex centration and asymmetric offset. A total of 24 consecutive patients (38 eyes) who underwent LASIK by one surgeon using AMARIS 750S excimer laser and a Carriazo-Pendular microkeratome for flap creation were retrospectively analyzed. Eyes targeted for plano and with correction in the maximum hyperopic meridian strictly higher than +4D were included in the retrospective analysis. Patients were reviewed at 1, 3, and 6 months postoperatively. Postoperative monocular corrected distance visual acuity (CDVA) and uncorrected distance visual acuity (UDVA), manifest refraction, and corneal wavefront aberrations were compared with respective preoperative metrics. Mean preoperative spherical equivalent and refractive astigmatism was +4.07 ± 0.90 D and 1.37 ± 1.26 D, respectively, reducing to +0.28 ± 0.58D (p<0.0001) and 0.49 ± 0.47 D (p = 0.0001) at the last postoperative visit. Six months postoperatively, 78% of eyes achieved a UDVA of 20/25 or better. No eye lost more than 2 Snellen lines of CDVA at any follow-up. There was a statistically significant induction of vertical trefoil (+0.104 ± 0.299 µm, p<0.05), vertical coma (-0.181 ± 0.463 µm, p<0.01), horizontal coma (+0.198 ± 0.663 µm, p<0.05), spherical aberration (-0.324 ± 0.281 µm, p<0.0001), secondary vertical trefoil (+0.018 ± 0.044 µm, p<0.01), and secondary horizontal coma (+0.026 ± 0.083 µm, p<0.05). Laser-assisted in situ keratomileusis for high hyperopia using corneal vertex centration with asymmetric offset results in significant improvement in refraction and visual acuity although affected by significant induction of some higher order aberrations.

Laser in situ keratomileusis surgery is not safe for military personnel.

PubMed

Xiao, Jian-He; Zhang, Mao-Nian; Jiang, Cai-Hui; Zhang, Ying; Qiu, Huai-Yu

2012-01-01

To investigate the relationship between eye injury and laser in-situ keratomileusis (LASIK) surgery in military personnel. This retrospective study collected the data from 27 evacuation hospitals of Chinese army. All medical records of eye injuries in military personnel admitted to the 27 hospitals between January 2006 and December 2010 were reviewed. Patients'detailed information was analyzed, including the injury time, place, type, cause, as well as examination, treatment and outcome. There were 72 eye-injured patients who had been treated by LASIK before. The incidence was rising year by year. Among them, 69 patients were diagnosed with mechanical ocular injury and 3 with non-mechanical ocular injury; 29 patients had traumatic flap-related complications and 21 patients need surgery. There was statistical difference when compared with those having no refractive surgery history. Visual acuity recovered well at discharge. There is a high risk of potential traumatic flap problems after LASIK and it is not recommended in army service.

Femtosecond Laser in situ Keratomileusis Flap Creation in Narrow Palpebral Fissure Eyes without Suction

PubMed Central

Chang, John S.M.; Law, Antony K.P.; Ng, Jack C.M.; Cheng, May S.Y.

2017-01-01

Purpose To evaluate a surgical technique used in eyes with narrow palpebral fissure undergoing femtosecond laser flap creation without suction during laser in situ keratomileusis (LASIK). Methods All data of 2 patient groups were collected through chart review. Group 1 consisted of 6 eyes with narrow palpebral fissure in which the suction ring was manually fixated and femtosecond laser was applied accordingly. Thirty comparison cases were randomly drawn from among eyes that underwent a standard LASIK procedure matched for age and preoperative refraction (group 2). Only 1 eye of each patient was selected to compare the refractive and visual outcomes between groups. Results In all group 1 eyes, the flaps were created successfully with manual fixation of the suction ring without suction. No eyes lost 2 or more lines of vision. No significant difference was found in the safety and refractive outcomes between groups. Conclusion Manual fixation of the suction ring in eyes with narrow palpebral fissure without suction was feasible for flap creation during LASIK. PMID:28690535

Peripheral Ulcerative Keratitis following Laser in situ Keratomileusis

PubMed Central

Burkholder, Bryn M.; Kuo, Irene C.

2016-01-01

Purpose We report a case of a patient with a history of glomerulonephropathy, not disclosed prior to laser in situ keratomileusis (LASIK), who developed severe postoperative peripheral ulcerative keratitis (PUK) soon after surgery. Method Case report. Results Within a week of surgery, the patient, who had no blepharitis or ocular surface disease, also developed diffuse lamellar keratitis (DLK) that was not contiguous with the PUK. Microbiologic evaluation of the flap interface disclosed no organisms, and no epithelial ingrowth was found. Both PUK and DLK resolved with topical and oral steroid therapy, and the patient's induced refractive error improved over the 12 months following LASIK. Conclusions Necrotizing keratitis has been described after LASIK surgery in patients with or without autoimmune disease. However, to our knowledge, there has been no case of PUK following LASIK. As shown by our patient's clinical course and the typical association of PUK with systemic conditions, patients with a history of atypical postinfectious sequelae may require additional preoperative counseling, vigilant postoperative monitoring, and possibly additional intervention. Because patients do not always divulge medical details, especially if an extraocular site was involved or illness occurred many years prior, this case demonstrates the importance of performing a diligent history that excludes autoimmune disorders or atypical postinfectious sequelae prior to proceeding with keratorefractive intervention. PMID:26889153

Review of current indications for combined very high fluence collagen cross-linking and laser in situ keratomileusis surgery

PubMed Central

Kanellopoulos, Anastasios John; Pamel, Gregory J

2013-01-01

In this brief review we will discuss the reasoning and evolution of our current use of combined very high-fluence collagen crosslinking and laser in situ keratomileusis. Several presentations and pertinent publications are reviewed, along with the key steps of the enhanced LASIK procedure. Long term outcome data support the safety and efficacy of LASIK Xtra in stabilizing myopic but also hyperopic LASIK results. In conclusion, we have compelling evidence that LASIK Xtra is a safe and effective adjunct. PMID:23925331

Endophthalmitis due to inadvertent globe penetration during retrobulbar injection of saline solution for laser in situ keratomileusis.

PubMed

Han, Ying; Lam, Har Hiu; Stewart, Jay M

2009-06-01

A 31-year-old woman presented with visual acuity of counting fingers and presumed bacterial endophthalmitis in the left eye 10 days after refractive surgery. During the procedure, a retrobulbar injection of balanced salt solution had been performed to assist with globe suction by the microkeratome. A perforation site was identified in the inferonasal retina. Following intravitreal antibiotic injection and surgical intervention, the visual acuity returned to 20/20. Retrobulbar injection to facilitate laser in situ keratomileusis carries risks. Careful monitoring for signs of infection is recommended if globe perforation is recognized.

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

PubMed

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

2013-01-01

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

Retinal Detachment After Laser In Situ Keratomileusis

PubMed Central

Al-Rashaed, Saba; Al-Halafi, Ali M

2011-01-01

Purpose: To report characteristics and outcome of rhegmatogenous retinal detachment (RRD) after laser in situ keratomileusis (LASIK) for myopia. Materials and Methods: A retrospective chart review of patients who presented with RRD after myopic LASIK over a 10-year period. Results: Fourteen eyes were identified with RRD. Of these, two of 6112 LASIK procedures were from our center. The mean age of patients with RRD was 35.43 years. The mean interval of RRD after LASIK was 37.71 months (range, 4 months to 10 years). The macula was involved in eight eyes and spared in six eyes. Retinal breaks included a macular hole in two eyes, and giant tear in two eyes. Multiple breaks (>2 breaks) occurred in 6 cases. Pars plana vitrectomy (PPV) was performed in 3 (21.4%) eyes, a scleral buckle (SB) was performed in 4 (28.5%) eyes and 7 (50%) eyes underwent combined PPV and SB. Mean follow-up was 15.18 months (range, 1 month to 7 years). The retina was successfully attached in all cases. The final visual acuity was 20/40 or better in 7 (50%) eyes, 20/40 to 20/60 in 4 (28.5%) eyes, and 20/200 or less in 3 (21.4%) eyes. Poor visual outcome was secondary to proliferative vitreoretinopathy, epiretinal membrane, macular scar and amblyopia. Conclusion: The prevalence of RRD after LASIK was low at our institute. Anatomical and visual outcomes were acceptable in eyes that were managed promptly. Although there is no cause-effect relationship between LASIK and RRD, a dilated fundus examination is highly recommended before and after LASIK for myopia. PMID:21887078

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.

Delayed onset Mycobacterium intracellulare keratitis after laser in situ keratomileusis

PubMed Central

Ko, JaeSang; Kim, Se Kyung; Yong, Dong Eun; Kim, Tae-im; Kim, Eung Kweon

2017-01-01

Abstract Rationale: Infectious keratitis is a relatively uncommon but potentially sight-threatening complication of laser in situ keratomileusis (LASIK). Mycobacterial keratitis is usually regarded as late onset keratitis among post-LASIK keratitis. There has been no documented case of Mycobacterium intracellulare post-LASIK keratitis of a long-latent period. Patient concerns: A 36-year-old man was referred to our out-patient clinic, for persistent corneal epithelial defect with intrastromal infiltration. He had undergone uneventful bilateral LASIK procedure 4 years before. He complained decreased vision, accompanied by ocular pain, photophobia, and redness in his left eye for 7 months. Diagnosis: Lamellar keratectomy was taken using femtosecond laser. Bacterial culture with sequenced bacterial 16s ribosomal DNA confirmed the organism to be M intracellulare. Interventions: After 3 months of administration of topical clarithromycin, amikacin, and moxifloxacin, the corneal epithelial defect was resolved and the infiltration was much improved. However, newly developed diffuse haziness with surrounding granular infiltration in the central cornea was noted. Drug toxicity was suspected and topical moxifloxacin was discontinued, resulting in resolution of the diffuse haze with infiltration. Outcome: The patient was followed up regularly without medication thereafter and recurrence was not found for 7 years. Lessons: This case presents the first case of M intracellulare keratitis after LASIK. LASIK surgeons should aware that post-LASIK keratitis can develop long after the operation and careful suspicion of infectious disease with meticulous diagnostic test is needed. PMID:29390522

Laser in situ keratomileusis for -6.00 to -18.00 diopters of myopia and up to -5.00 diopters of astigmatism: 15-year follow-up.

PubMed

Alió, Jorge L; Soria, Felipe; Abbouda, Alessandro; Peña-García, Pablo

2015-01-01

To evaluate the long-term outcomes of laser in situ keratomileusis (LASIK) for high myopia with or without astigmatism. Vissum Instituto Oftalmologico de Alicante and Miguel Hernandez University, Alicante, Spain. Retrospective-prospective case series. Laser in situ keratomileusis was performed using the Visx 20/20 excimer laser. The minimum follow-up was 15 years. The main outcome measures were uncorrected (UDVA) and corrected (CDVA) distance visual acuities, manifest refraction, and corneal topography. This study included 40 patients (40 eyes) with a mean age of 51.08 years ± 6.67 (SD) (range 41 to 60 years) with high myopia (-6.00 to -18.00 diopters [D]). At 15 years, the safety index was 1.23 and the efficacy index, 0.95. During the follow-up, a significant increase in the dioptric power of all keratometric variables was detected (P≤.028, Friedman test), the most notable increase occurring between 3 months and 1 year (P≤.005). At 15 years, 46.15% of the eyes were within ±1.00 D of the attempted spherical equivalent and 64.10% were within ±2.00 D. The UDVA at 15 years was 20/25 or better in 43.59% of eyes and 20/40 or better in 64.10% of eyes. The postoperative CDVA was significantly better than preoperatively (P<.001). The postoperative complications were minor except in 1 eye in which ectasia occurred. Laser in situ keratomileusis for high myopia was safe over the long term. However, significant myopic regression with time was detected. Low preoperative pachymetry and low residual stromal bed were predictors of keratometric regression. No author has a financial or proprietary interest in any material or method mentioned. Copyright © 2015 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.

Lamina Cribrosa Changes after Laser In Situ Keratomileusis in Myopic Eyes

PubMed Central

Lee, Soomin; Choi, Da-Ye Diana; Lim, Dong Hui; Chung, Tae Young; Han, Jong Chul

2018-01-01

Purpose To determine deep optic nerve head structure changes after transient intraocular pressure elevation during laser in situ keratomileusis (LASIK) for myopia. Methods Enhanced depth imaging-optical coherence tomography was performed in each myopic eye that underwent LASIK surgery. Enhanced depth imaging-optical coherence tomography images were created at postoperative 1 day, 1 week, 2 weeks, and 1 month. Lamina cribrosa (LC) thickness, LC depth and prelaminar thickness at the superior, middle and inferior portions of the optic nerve head were measured by two investigators. Results Forty eyes in 40 patients were included in the present study. During follow-up, there were no significant differences in prelaminar thickness or LC depth. The LC demonstrated increased thickness at postoperative 1 day at all three locations (superior, middle, and inferior) (p < 0.001, p < 0.001, p < 0.001, respectively). However, no significant changes were observed at postoperative 1 week, 2 weeks, and 1 month. Conclusions The LC thickness could increase at 1 day after LASIK surgery. However, the thickness will gradually return to baseline morphology. Temporary intraocular pressure increase during LASIK does not appear to induce irreversible LC thickness changes. PMID:29611373

Lamina Cribrosa Changes after Laser In Situ Keratomileusis in Myopic Eyes.

PubMed

Lee, Soomin; Choi, Da Ye Diana; Lim, Dong Hui; Chung, Tae Young; Han, Jong Chul; Kee, Changwon

2018-04-01

To determine deep optic nerve head structure changes after transient intraocular pressure elevation during laser in situ keratomileusis (LASIK) for myopia. Enhanced depth imaging-optical coherence tomography was performed in each myopic eye that underwent LASIK surgery. Enhanced depth imaging-optical coherence tomography images were created at postoperative 1 day, 1 week, 2 weeks, and 1 month. Lamina cribrosa (LC) thickness, LC depth and prelaminar thickness at the superior, middle and inferior portions of the optic nerve head were measured by two investigators. Forty eyes in 40 patients were included in the present study. During follow-up, there were no significant differences in prelaminar thickness or LC depth. The LC demonstrated increased thickness at postoperative 1 day at all three locations (superior, middle, and inferior) (p < 0.001, p < 0.001, p < 0.001, respectively). However, no significant changes were observed at postoperative 1 week, 2 weeks, and 1 month. The LC thickness could increase at 1 day after LASIK surgery. However, the thickness will gradually return to baseline morphology. Temporary intraocular pressure increase during LASIK does not appear to induce irreversible LC thickness changes. © 2018 The Korean Ophthalmological Society.

Comparison of 2 wavefront-guided excimer lasers for myopic laser in situ keratomileusis: one-year results.

PubMed

Yu, Charles Q; Manche, Edward E

2014-03-01

To compare laser in situ keratomileusis (LASIK) outcomes between 2 wavefront-guided excimer laser systems in the treatment of myopia. University eye clinic, Palo Alto, California, USA. Prospective comparative case series. One eye of patients was treated with the Allegretto Wave Eye-Q system (small-spot scanning laser) and the fellow eye with the Visx Star Customvue S4 IR system (variable-spot scanning laser). Evaluations included measurement of uncorrected visual acuity, corrected visual acuity, and wavefront aberrometry. One hundred eyes (50 patients) were treated. The mean preoperative spherical equivalent (SE) refraction was -3.89 diopters (D) ± 1.67 (SD) and -4.18 ± 1.73 D in the small-spot scanning laser group and variable-spot scanning laser group, respectively. There were no significant differences in preoperative higher-order aberrations (HOAs) between the groups. Twelve months postoperatively, all eyes in the small-spot scanning laser group and 92% in the variable-spot scanning laser group were within ±0.50 D of the intended correction (P = .04). At that time, the small-spot scanning laser group had significantly less spherical aberration (0.12 versus 0.15) (P = .04) and significantly less mean total higher-order root mean square (0.33 μm versus 0.40 μm) (P = .01). Subjectively, patients reported that the clarity of night and day vision was significantly better in the eye treated with the small-spot scanning laser. The predictability and self-reported clarity of vision of wavefront-guided LASIK were better with the small-spot scanning laser. Eyes treated with the small-spot scanning laser had significantly fewer HOAs. Copyright © 2014 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.

Safety, efficacy, and predictability of laser in situ keratomileusis to correct myopia or myopic astigmatism with a 750 Hz scanning-spot laser system.

PubMed

Tomita, Minoru; Watabe, Miyuki; Yukawa, Satoshi; Nakamura, Nobuo; Nakamura, Tadayuki; Magnago, Thomas

2014-02-01

To evaluate the clinical outcomes of laser in situ keratomileusis (LASIK) to correct myopia or myopic astigmatism using the Amaris 750S 750 Hz excimer laser. Private LASIK center, Tokyo, Japan. Case series. Patients with myopia or myopic astigmatism (spherical equivalent -0.50 to -11.63 diopters [D]), a corrected distance visual acuity (CDVA) of 20/20 or better, and an estimated residual bed thickness of 300 μm or more had LASIK using the aspheric aberration-free ablation profile of the 750 Hz scanning-spot laser and the Femto LDV Crystal Line femtosecond laser for flap creation. Study parameters included uncorrected distance visual acuity (UDVA), CDVA, manifest refraction, astigmatism, and higher-order aberrations (HOAs). The study included 1280 eyes (685 patients). At 3 months, 96.6% of eyes had a UDVA of 20/20 or better and 99.1% had 20/32 or better; 94.1% of eyes were within ± 0.50 D of the intended correction and 98.9% were within ± 1.00 D; 89.7% of eyes had no residual cylinder and 96.0% had a postoperative astigmatism of less than 0.50 D. All eyes had a postoperative CDVA of 20/20 or better. The HOAs increased postoperatively (P<.001), with mean total postoperative corneal and ocular HOAs of 0.66 μm ± 0.20 (SD) and 0.56 ± 0.23 μm, respectively. The efficacy index and safety index were 1.02 and 1.06, respectively. Laser in situ keratomileusis with the 750 Hz scanning-spot laser was safe, effective, and predictable. No specific clinical side effects that might be associated with a high repetition rate occurred. Mr. Magnago is an employee of Schwind eye-tech-solutions GmbH. No other author has a financial or proprietary interest in any material or method mentioned. Copyright © 2013 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.

Corneal scarring from laser in situ keratomileusis after epikeratoplasty: Clinical and histopathologic analysis

PubMed Central

Khandelwal, Sumitra S.; Randleman, J. Bradley; Grossniklaus, Hans E.

2015-01-01

A 47-year-old woman required penetrating keratoplasty in the right eye after developing delayed visually significant corneal scarring bilaterally after laser in situ keratomileusis (LASIK) in 1997 following epikeratoplasty in 1987. Spectral domain ocular coherence tomography of the left cornea showed a 100 μm lenticule with a LASIK flap posterior to the host Bowman layer at 250 μm. Histopathology and electron microscopy of the right corneal button showed a 120 μm lenticule with a LASIK flap within the lenticule at 100 μm. Clinically significant scarring was present within the LASIK flap interface, within the lenticule stroma, and within the area of the underlying host Bowman layer. There were keratocytes at the junction between the LASIK flap and lenticule stromal bed. Although epikeratoplasty is no longer practiced, post-epikeratoplasty patients may present for refractive surgical options and LASIK carries significant risks for corneal scarring in these individuals, especially when using flap-creating devices that may create thin LASIK flaps. PMID:23506924

Analysis of corneal endothelial cell density and morphology after laser in situ keratomileusis using two types of femtosecond lasers

PubMed Central

Tomita, Minoru; Waring, George O; Watabe, Miyuki

2012-01-01

Purpose To compare two different femtosecond lasers used for flap creation during laser-assisted in situ keratomileusis (LASIK) surgery in terms of their effects on the corneal endothelium. Methods We performed LASIK surgery on 254 eyes of 131 patients using IntraLase FS60 (Abbott Medical Optics, Inc, Irvine, CA; IntraLase group) and 254 eyes of 136 patients using Femto LDV (Ziemer Group AG, Port, Switzerland; LDV group) for corneal flap creation. The mean cell density, coefficient of variation, and hexagonality of the corneal endothelial cells were determined and the results were statistically compared. Results There were no statistically significant differences in the corneal morphology between pre and post LASIK results in each group, nor were there significant differences between the results of both groups at 3 months post LASIK. Conclusions Both IntraLase FS60 and Ziemer Femto LDV are able to create flaps without significant adverse effects on the corneal endothelial morphology through 3 months after LASIK surgery. PMID:23055680

Combined application of prophylactic corneal cross-linking and laser in-situ keratomileusis - a review of literature.

PubMed

Chan, Tommy C Y; Ng, Alex L K; Chan, Karen K W; Cheng, George P M; Wong, Ian Y H; Jhanji, Vishal

2017-11-01

Laser in-situ keratomileusis (LASIK) is safe and effective laser refractive procedures in treating refractive errors. However, regression of treatment and iatrogenic keratectasia remain to be a major concern, especially in treating thin cornea with high ametropia. Collagen cross-linking (CXL) is an effective method in stopping keratoconus progression through increasing the biomechanical strength of the cornea. Adjuvant cross-linking to refractive procedures can theoretically help prevent regression and reduce the risk of keratectasia development by increasing the mechanical stability of cornea. During the procedure, riboflavin is directly applied to the corneal stroma, thereby reducing the need of de-epithelialization as in the conventional protocol for keratoconus. Currently, there is still no consensus regarding the indication of CXL during refractive procedure, nor any standardized treatment protocol. This article aims to summarize the current evidence regarding the use of adjuvant CXL in LASIK. © 2016 Acta Ophthalmologica Scandinavica Foundation. Published by John Wiley & Sons Ltd.

Combined laser in-situ keratomileusis and accelerated corneal cross-linking: an update.

PubMed

Tomita, Minoru

2016-07-01

The purpose is to review the literature of combined laser in-situ keratomileusis (LASIK) and accelerated corneal collagen cross-linking (CXL) in context of its indications-contraindications, kerato-refractive, visual and safety outcomes, particularly with reference to preventing the development of post-LASIK ectasia. LASIK + accelerated CXL has been developed with the rationale that the addition of CXL after LASIK may strengthen the LASIK compromised corneal biomechanics and minimize the complications such as post-LASIK ectasia. Different clinical studies have documented the safety and efficacy of LASIK + accelerated CXL for the correction of myopia or hyperopia and in the patients with low predicted residual bed thickness. Available literature shows that refractive and keratometric outcomes of LASIK + accelerated CXL are comparable or better than LASIK alone. Less regression has been observed after LASIK + accelerated CXL compared with LASIK alone and no case of post-LASIK ectasia development has been reported among 673 eyes with the follow-up ranging from 3 months to 4.5 years. Future studies with large numbers of patients and longer postoperative follow-ups are needed to establish the efficacy of LASIK + accelerated CXL in preventing the development of post-LASIK ectasia.

Corneal Densitometry as a Tool to Measure Epithelial Ingrowth After Laser In Situ Keratomileusis.

PubMed

Adran, Daniel; Vaillancourt, Louis; Harissi-Dagher, Mona; Kruh, Jonathan N; Syed, Zeba A; Robinson, Steven; Melki, Samir

2017-04-01

This study evaluates the correlation between corneal densitometry and epithelial ingrowth (EI) after laser in situ keratomileusis (LASIK). Corneal densitometry of 3 patients who developed EI after LASIK was measured with the Oculus Pentacam. Corneal densitometry readings of each patient were obtained preoperatively and postoperatively after ingrowth was discovered. Densitometry was recorded at the central nest of opacity and at the leading edges of EI. For all patients, the most severe stages of EI observed on slit-lamp photographs correlated with the highest densitometry readings, with peak densitometry ranging from 73.3 to 95.1. These values were much higher than preoperative densitometry readings, which ranged from 21.8 to 27.2. In 2 cases, the Pentacam densitometry map revealed progression of EI toward the visual axis that was only faintly detectable or not detectable at all on the corresponding slit-lamp photographs. Corneal densitometry seems to be an objective measure of the severity and progression of EI after LASIK.

Comparison of 2 femtosecond lasers for flap creation in myopic laser in situ keratomileusis: one-year results.

PubMed

Yu, Charles Q; Manche, Edward E

2015-04-01

To compare laser in situ keratomileusis (LASIK) outcomes between 2 femtosecond lasers for flap creation in the treatment of myopia up to 1 year. University eye clinic. Prospective randomized eye-to-eye study. Consecutive myopic patients were treated with wavefront-guided LASIK. One eye had a flap created by the Intralase FS 60 kHz femtosecond laser, and the fellow eye was treated with the Intralase iFS 150 kHz femtosecond laser. Eyes were randomized according to ocular dominance. Evaluations included measurement of uncorrected distance visual acuity (UDVA), corrected distance visual acuity, contrast sensitivity and wavefront aberrometry. The study enrolled 122 eyes of 61 patients. The mean preoperative spherical equivalent refraction was -4.62 diopters (D) ± 2.32 (SD) and -4.66 ± 2.30 D in the 150 kHz group and 60 kHz group, respectively. Patients preferred the 150 kHz laser to the 60 kHz laser intraoperatively (52.5% versus 26.2%) (P = .005). One week postoperatively, UDVA was 20/16 or better in 85.2% in the 150 kHz group and 70.5% in the 60 kHz group; the difference was statistically significant (P < .05). At 12 months, there were no significant differences in refractive outcomes or higher-order aberrations between the 2 groups. Flap creation with the 150 kHz system and the 60 kHz system resulted in excellent LASIK outcomes. Intraoperatively, patients preferred the 150 kHz system, which yielded better UDVA in the early postoperative period. There were no significant differences at 1 year between the 2 laser systems. Proprietary or commercial disclosures are listed after the references. Copyright © 2015 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.

Wavefront-guided versus wavefront-optimized laser in situ keratomileusis: contralateral comparative study.

PubMed

Padmanabhan, Prema; Mrochen, Michael; Basuthkar, Subam; Viswanathan, Deepa; Joseph, Roy

2008-03-01

To compare the outcomes of wavefront-guided and wavefront-optimized treatment in fellow eyes of patients having laser in situ keratomileusis (LASIK) for myopia. Medical and Vision Research Foundation, Tamil Nadu, India. This prospective comparative study comprised 27 patients who had wavefront-guided LASIK in 1 eye and wavefront-optimized LASIK in the fellow eye. The Hansatome (Bausch & Lomb) was used to create a superior-hinged flap and the Allegretto laser (WaveLight Laser Technologie AG), for photoablation. The Allegretto wave analyzer was used to measure ocular wavefront aberrations and the Functional Acuity Contrast Test chart, to measure contrast sensitivity before and 1 month after LASIK. The refractive and visual outcomes and the changes in aberrations and contrast sensitivity were compared between the 2 treatment modalities. One month postoperatively, 92% of eyes in the wavefront-guided group and 85% in the wavefront-optimized group had uncorrected visual acuity of 20/20 or better; 93% and 89%, respectively, had a postoperative spherical equivalent refraction of +/-0.50 diopter. The differences between groups were not statistically significant. Wavefront-guided LASIK induced less change in 18 of 22 higher-order Zernike terms than wavefront-optimized LASIK, with the change in positive spherical aberration the only statistically significant one (P= .01). Contrast sensitivity improved at the low and middle spatial frequencies (not statistically significant) and worsened significantly at high spatial frequencies after wavefront-guided LASIK; there was a statistically significant worsening at all spatial frequencies after wavefront-optimized LASIK. Although both wavefront-guided and wavefront-optimized LASIK gave excellent refractive correction results, the former induced less higher-order aberrations and was associated with better contrast sensitivity.

Outcomes of laser in situ keratomileusis and photorefractive keratectomy in patients taking isotretinoin.

PubMed

Ortega-Usobiaga, Julio; Llovet-Osuna, Fernando; Djodeyre, Mohammad Reza; Bilbao-Calabuig, Rafael; González-López, Félix; Llovet-Rausell, Andrea; Druchkiv, Vasyl

2018-05-14

To determine the functional outcomes of laser in situ keratomileusis (LASIK) and photorefractive keratectomy (PRK) in patients taking isotretinoin, which is contraindicated for these procedures. Multicentre, retrospective, interventional case series METHODS: All patients taking isotretinoin who underwent LASIK or PRK from January 2003 to September 2017 were included (group 1). Patients were compared with those undergoing LASIK or PRK who had taken isotretinoin previously but not in the previous 6 months (group 2). Patients were included consecutively. A total of 113 patients (219 eyes) were included. No significant intraoperative or postoperative complications were found. There were no significant differences between the groups in terms of visual acuity, postoperative spherical equivalent, efficacy index, predictability, or safety index. When only PRK patients were taken into account, the efficacy index (p: 0.017), postoperative sphere (p: 0.041), and postoperative astigmatism (p<0.001) were better in group 2, although the difference was not clinically relevant. In our experience, LASIK and PRK can be performed effectively and safely in selected patients taking isotretinoin. The absolute exclusion of certain systemic medications should be reconsidered. Copyright © 2018 Elsevier Inc. All rights reserved.

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.

Tracker-assisted versus manual ablation zone centration in laser in situ keratomileusis for myopia and astigmatism.

PubMed

Pineros, Oscar E

2002-01-01

Eye tracker systems have been developed concomitantly with small scanning beams to theoretically reduce ablation zone decentration and for accurate registration of all the laser pulses on the cornea. The purpose of the study was to compare the tracker-assisted with the manual centration method. Twenty-five patients (48 eyes) with myopia and/or astigmatism had laser in situ keratomileusis (LASIK) between August 1998 and February 1999 with the Technolas 117C laser. Twenty patients (38 eyes, 80%) were available for follow-up at 3 months after surgery. Eyes were assigned randomly to one of two ablation zone centration methods: Group 1: Tracker-assisted (20 eyes), Group 2: Manual (18 eyes). Mean distance between the ablation zone center and the pupillary center in the tracker-assisted centration group was 0.55 +/- 0.30 mm (range, 0.10 to 1.4 mm), and in the manual centration group, 0.43 +/- 0.23 mm (range, 0.10 to 1.0 mm) (P = .177). There was no statistically significant difference in postoperative contrast sensitivity, glare, and Topographical Corneal Surface Regularity Index (SRI) between the two groups. We obtained good results with both centration methods. We did not find superiority of the tracker-assisted over manual regarding ablation zone centration, vision quality, or regularity of the ablation.

Comparison of visual acuity of the patients on the first day after sub-Bowman keratomileusis or laser in situ keratomileusis

PubMed Central

Zhao, Wei; Wu, Ting; Dong, Ze-Hong; Feng, Jie; Ren, Yu-Feng; Wang, Yu-Sheng

2016-01-01

AIM To compare recovery of the visual acuity in patients one day after sub-Bowman keratomileusis (SBK) or laser in situ keratomileusis (LASIK). METHODS Data from 5923 eyes in 2968 patients that received LASIK (2755 eyes) or SBK (3168 eyes) were retrospectively analyzed. The eyes were divided into 4 groups according to preoperative spherical equivalent: between -12.00 to -9.00 D, extremely high myopia (n=396, including 192 and 204 in SBK and LASIK groups, respectively); -9.00 to -6.00 D, high myopia (n=1822, including 991 and 831 in SBK and LASIK groups, respectively), -6.00 to -3.00 D, moderate myopia (n=3071, including 1658 and 1413 in SBK and LASIK groups, respectively), and -3.00 to 0.00 D, low myopia (n=634, including 327 and 307 in SBK and LASIK groups, respectively). Uncorrected logMAR visual acuity values of patients were assessed under standard natural light. Analysis of variance was used for comparisons among different groups. RESULTS Uncorrected visual acuity values were 0.0115±0.1051 and 0.0466±0.1477 at day 1 after operation for patients receiving SBK and LASIK, respectively (P<0.01); visual acuity values of 0.1854±0.1842, 0.0615±0.1326, -0.0033±0.0978, and -0.0164±0.0972 were obtained for patients in the extremely high, high, moderate, and low myopia groups, respectively (P<0.01). In addition, significant differences in visual acuity at day 1 after operation were found between patients receiving SBK and LASIK in each myopia subgroup. CONCLUSION Compared with LASIK, SBK is safer and more effective, with faster recovery. Therefore, SBK is more likely to be accepted by patients than LASIK for better uncorrected visual acuity the day following operation. PMID:27158619

Comparison of visual acuity of the patients on the first day after sub-Bowman keratomileusis or laser in situ keratomileusis.

PubMed

Zhao, Wei; Wu, Ting; Dong, Ze-Hong; Feng, Jie; Ren, Yu-Feng; Wang, Yu-Sheng

2016-01-01

To compare recovery of the visual acuity in patients one day after sub-Bowman keratomileusis (SBK) or laser in situ keratomileusis (LASIK). Data from 5923 eyes in 2968 patients that received LASIK (2755 eyes) or SBK (3168 eyes) were retrospectively analyzed. The eyes were divided into 4 groups according to preoperative spherical equivalent: between -12.00 to -9.00 D, extremely high myopia (n=396, including 192 and 204 in SBK and LASIK groups, respectively); -9.00 to -6.00 D, high myopia (n=1822, including 991 and 831 in SBK and LASIK groups, respectively), -6.00 to -3.00 D, moderate myopia (n=3071, including 1658 and 1413 in SBK and LASIK groups, respectively), and -3.00 to 0.00 D, low myopia (n=634, including 327 and 307 in SBK and LASIK groups, respectively). Uncorrected logMAR visual acuity values of patients were assessed under standard natural light. Analysis of variance was used for comparisons among different groups. Uncorrected visual acuity values were 0.0115±0.1051 and 0.0466±0.1477 at day 1 after operation for patients receiving SBK and LASIK, respectively (P<0.01); visual acuity values of 0.1854±0.1842, 0.0615±0.1326, -0.0033±0.0978, and -0.0164±0.0972 were obtained for patients in the extremely high, high, moderate, and low myopia groups, respectively (P<0.01). In addition, significant differences in visual acuity at day 1 after operation were found between patients receiving SBK and LASIK in each myopia subgroup. Compared with LASIK, SBK is safer and more effective, with faster recovery. Therefore, SBK is more likely to be accepted by patients than LASIK for better uncorrected visual acuity the day following operation.

Factors Influencing Intraocular Pressure Changes after Laser In Situ Keratomileusis with Flaps Created by Femtosecond Laser or Mechanical Microkeratome.

PubMed

Lin, Meng-Yin; Chang, David C K; Shen, Yun-Dun; Lin, Yen-Kuang; Lin, Chang-Ping; Wang, I-Jong

2016-01-01

The aim of this study is to describe factors that influence the measured intraocular pressure (IOP) change and to develop a predictive model after myopic laser in situ keratomileusis (LASIK) with a femtosecond (FS) laser or a microkeratome (MK). We retrospectively reviewed preoperative, intraoperative, and 12-month postoperative medical records in 2485 eyes of 1309 patients who underwent LASIK with an FS laser or an MK for myopia and myopic astigmatism. Data were extracted, such as preoperative age, sex, IOP, manifest spherical equivalent (MSE), central corneal keratometry (CCK), central corneal thickness (CCT), and intended flap thickness and postoperative IOP (postIOP) at 1, 6 and 12 months. Linear mixed model (LMM) and multivariate linear regression (MLR) method were used for data analysis. In both models, the preoperative CCT and ablation depth had significant effects on predicting IOP changes in the FS and MK groups. The intended flap thickness was a significant predictor only in the FS laser group (P < .0001 in both models). In the FS group, LMM and MLR could respectively explain 47.00% and 18.91% of the variation of postoperative IOP underestimation (R2 = 0.47 and R(2) = 0.1891). In the MK group, LMM and MLR could explain 37.79% and 19.13% of the variation of IOP underestimation (R(2) = 0.3779 and 0.1913 respectively). The best-fit model for prediction of IOP changes was the LMM in LASIK with an FS laser.

Factors Influencing Intraocular Pressure Changes after Laser In Situ Keratomileusis with Flaps Created by Femtosecond Laser or Mechanical Microkeratome

PubMed Central

Lin, Meng-Yin; Chang, David C. K.; Shen, Yun-Dun; Lin, Yen-Kuang; Lin, Chang-Ping; Wang, I-Jong

2016-01-01

The aim of this study is to describe factors that influence the measured intraocular pressure (IOP) change and to develop a predictive model after myopic laser in situ keratomileusis (LASIK) with a femtosecond (FS) laser or a microkeratome (MK). We retrospectively reviewed preoperative, intraoperative, and 12-month postoperative medical records in 2485 eyes of 1309 patients who underwent LASIK with an FS laser or an MK for myopia and myopic astigmatism. Data were extracted, such as preoperative age, sex, IOP, manifest spherical equivalent (MSE), central corneal keratometry (CCK), central corneal thickness (CCT), and intended flap thickness and postoperative IOP (postIOP) at 1, 6 and 12 months. Linear mixed model (LMM) and multivariate linear regression (MLR) method were used for data analysis. In both models, the preoperative CCT and ablation depth had significant effects on predicting IOP changes in the FS and MK groups. The intended flap thickness was a significant predictor only in the FS laser group (P < .0001 in both models). In the FS group, LMM and MLR could respectively explain 47.00% and 18.91% of the variation of postoperative IOP underestimation (R2 = 0.47 and R2 = 0.1891). In the MK group, LMM and MLR could explain 37.79% and 19.13% of the variation of IOP underestimation (R2 = 0.3779 and 0.1913 respectively). The best-fit model for prediction of IOP changes was the LMM in LASIK with an FS laser. PMID:26824754

Management of long-standing partially torn and flipped laser in situ keratomileusis flaps.

PubMed

Kim, Jin Sun; Chung, Byunghoon; Lee, Taekjune; Kim, Woon Cho; Kim, Tae-im; Kim, Eung Kweon

2015-02-01

We describe 2 cases of traumatized and torn laser in situ keratomileusis (LASIK) flaps, partially flipped anteriorly or posteriorly, fixed for 8 months or 4 months, and accompanied by epithelial ingrowth. The 2 patients had had uneventful bilateral LASIK 6 years and 1 year before the trauma. In Case 1, the anteriorly flipped flap was removed with transepithelial phototherapeutic keratectomy. Next, mitomycin-C 0.04% was applied for 30 seconds. In Case 2, the portion of the flap that was flipped posteriorly and buried under the remaining intact LASIK flap was restored to its original normal position and epithelial ingrowth was removed mechanically with a microcurette. Irrigation with 20% ethanol was performed to inhibit the recurrence of interfacial epithelial ingrowth. The stretched amniotic membrane overlay over the cornea and sclera was sutured tightly to the episclera as the biologic pressure patch for the inhibition of epithelial re-ingrowth. Good visual acuity was restored in both cases. No author has a financial or proprietary interest in any material or method mentioned. Copyright © 2015 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.

[Clinical Results of Diffractive Multifocal Intraocular Lens Implantation after Laser In Situ Keratomileusis].

PubMed

Yoshino, Mami; Minami, Keiichiro; Hirasawa, Manabu; Oki, Shinichi; Bissen-Miyajima, Hiroko

2015-09-01

To evaluate the visual performance in eyes with diffractive intraocular lenses (IOLs) after laser in situ keratomileusis (LASIK). This single-center retrospective study evaluated eyes that had diffractive multifocal IOL implantation after previous LASIK or not treated with LASIK (controls). The outcomes' measures were the visual acuities (VAs) at distance and near, spherical equivalent (SE) and contrast sensitivity at one month postoperatively. The study evaluated 40 eyes of 33 patients. The mean uncorrected logMAR VAs were -0.05 ± 0.13/0.00 ± 0.14 (LASIK group/control group) at distance and 0.10 ± 0.13/0.16 ± 0.18 at near. There was no statistically significant difference between the 2 groups at the VAs. The SE of the LASIK group was -0.06 ± 0.39 D, significantly lower than the control group (0.22 ± 0.45 D) (p < 0.05). The contrast sensitivity of the LASIK group at high spatial frequency was lower than the control group (p < 0.05). After LASIK, the diffractive multifocal IOL provided good uncorrected distance and near VAs. However, decrease in contrast sensitivity should be considered.

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.

Incidence of rainbow glare after laser in situ keratomileusis flap creation with a 60 kHz femtosecond laser.

PubMed

Bamba, Sonya; Rocha, Karolinne M; Ramos-Esteban, Jerome C; Krueger, Ronald R

2009-06-01

To report the incidence of and factors associated with rainbow glare after laser in situ keratomileusis (LASIK) flap creation with a 60 kHz femtosecond laser. Department of Refractive Surgery, Cleveland Clinic Cole Eye Institute, Cleveland, Ohio, USA. Consecutive patients having LASIK by the same surgeon were questioned during postoperative examinations or by telephone about postoperative rainbow glare (radiating colors around a white light at night). Femtosecond laser (IntraLase) settings included pulse frequency 60 kHz, flap thickness 90 to 110 mum, and spot/line separation 8 mum. Raster energy was 0.8 microJ (75% of eyes) and 1.0 to 1.1 microJ (25%). Excimer laser ablation was performed with the LADAR 4000 or 6000 platform using custom or conventional treatments. Of 260 consecutive patients, 256 (98.5%) were successfully contacted. Fifteen patients (28 eyes) reported postoperative rainbow glare (5.8%), described as 4 to 12 bands of color around a white light, with 6 bands most common. The symptom did not correlate with refractive error, age, or sex but was more frequent at 1.0 microJ or 1.1 microJ raster energy (11.6%) than at 0.8 microJ (4.1%). The incidence followed a bimodal distribution, with the first grouping due to inadequate alignment and higher energy just after laser installation and the second just before a later maintenance service call. Rainbow glare is a mild optical side effect of femtosecond LASIK. In this study, higher raster energy levels and length of time between service calls were associated with the occurrence of rainbow glare.

Higher-order aberrations after wavefront-optimized photorefractive keratectomy and laser in situ keratomileusis

PubMed Central

Randleman, J. Bradley; Perez-Straziota, Claudia E.; Hu, Michelle H.; White, Alfred J.; Loft, Evan S.; Stulting, R. Doyle

2013-01-01

PURPOSE To analyze the changes in higher-order aberrations (HOAs) that occur after wavefront-optimized photorefractive keratectomy (PRK) and laser in situ keratomileusis (LASIK). SETTING Private practice, Atlanta, Georgia, USA. METHODS This retrospective analysis comprised eyes that had PRK or LASIK from June 2004 through October 2005. Postoperative outcome measures included 3-month uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BSCVA), manifest refraction spherical equivalent (MRSE), changes in the root mean square (RMS) and grouped coefficient HOAs (microns) measured with a corneal analyzer, and subjective assessment of visual aberrations. RESULTS One hundred consecutive eyes of 54 patients had PRK, and 100 contemporaneous consecutive eyes of 71 patients had LASIK. The PRK and LASIK populations were similar in general demographics, preoperative HOAs, and postoperative UCVA and BSCVA. The mean MRSE was slightly hyperopic after PRK (mean +0.11 diopters [D]) and slightly myopic after LASIK (mean −0.19 D) (P<.0001). There were no statistically significant changes in RMS or grouped coefficient HOA values after PRK or LASIK, nor were there significant differences in postoperative RMS or grouped coefficient HOA values between PRK and LASIK. One percent of PRK and LASIK patients reported a subjective increase in postoperative visual aberrations; 5% reported a subjective improvement postoperatively. CONCLUSIONS Wavefront-optimized excimer laser surgery did not induce significant HOAs after PRK or LASIK. The 2 techniques were equally efficacious and had equivalent postoperative HOA profiles. PMID:19185240

Comparison of Sub-Bowman Keratoplasty Laser In situ Keratomileusis Flap Properties between Microkeratome and Femtosecond Laser.

PubMed

Fazel, Farhad; Ghoreishi, Mohammad; Ashtari, Alireza; Arefpour, Reza; Namgar, Mohammad

2017-01-01

Since thin and high-quality flaps produce more satisfactory surgical outcomes, flaps created by mechanical microkeratomes are more economical as compared with femtosecond lasers, and no Iranian study has concentrated laser in situ keratomileusis (LASIK) flap peculiarities between Moria Sub-Bowman keratoplasty (SBK) microkeratomes and LDV femtoseconds, the present study compares and contrasts them. This cross-sectional study was done on all patients who underwent LASIK surgery 1-month before this study. Thirty eyes were divided into per group. Flaps in the first group and second group were created, respectively, using Moria SBK microkeratome and LDV femtosecond laser. The other stages of LASIK were done equally in both groups. One month after surgery, the thickness of flaps was measured by anterior segment optical coherence tomography in five regions of flaps. Corneal anterior density was calculated and recorded 1-month after surgery using pentacam and by employing optical densitometry in a distance in the limit range of 0-6 mm from cornea center. Densitometry measurements were obtained and expressed in standardized grayscale units (GSUs). Postsurgery densitometry results reveal that anterior densities of cornea in limit range of 0-2 mm in groups of LDV femtosecond laser and Moria microkeratome are 21.35 ± 0.87 GSU and 22.85 ± 1.25 GSU, respectively. Accordingly, these two groups are significantly different in this regard ( P < 0.001). Moreover, anterior densities of the cornea in the limit range of 2-6 mm in these groups are 19.66 ± 0.99 GSU and 20.73 ± 1.24 GSU, respectively. Accordingly, these two groups are significantly different in this regard ( P = 0.04). There is a lower mean of flap thickness in the case of LDV femtosecond laser. Femtosecond laser method is greatly preferred as compared with Moria microkeratome because of greater homogeneity in flap thickness, smaller thickness, and lower density in optical zone.

Dynamic torsional misalignment of eyes during laser in-situ keratomileusis.

PubMed

Shajari, Mehdi; Bühren, Jens; Kohnen, Thomas

2016-05-01

To determine the amount and characteristics of dynamic torsional misalignment of eyes during excimer ablation in laser in-situ keratomileusis (LASIK). Retrospective trial for evaluation of dynamic intraoperative torsional misalignment of 179 eyes that underwent LASIK for correction of myopia and/or astigmatism. Patients were treated with the Keracor 217z excimer laser implementing 25 Hz dynamic eye tracker ACE 100 (both Technolas Perfect Vision, Munich, Germany). From dynamic torsional misalignments, temporal power spectra were obtained by Fourier analysis up to a frequency of 12.5 Hz and an amplitude of ±15° from initial torsional status (limited by the tracking system). The f90, f95, and f99 criteria were defined as the frequency below which 90 %, 95 %, and 99 % of misalignments occur. A Wilcoxon rank sum test was performed to detect differences of f90, f95, and f99 in groups' gender, age, and eye (if both eyes underwent surgery at same day). Multiple regression analysis (MRA) was performed to evaluate possible preoperative predictors of f90, f95, and f99. Fourier analysis showed a dominance of high-frequency, low-power dynamic torsional misalignment. Mean f95 threshold of rotational movements was 4.89±2.12 Hz (median 4.54, ranging from 0.44 to 9.23 Hz). Wilcoxon rank sum test showed no differences in f90, f95, and f99 between groups' gender, age, and eye. MRA revealed age, gender, and optical zone as preoperative predictors on intraoperative f90, f95, and f99. Dynamic intraoperative torsional misalignments of eyes undergoing LASIK are dominated by low-frequency (slow), high-power (large) movements, with 95 % being slower than 4.89Hz regarding the spectrum analyzed (0-12.5Hz, ±15°). Movements can be predicted preoperatively by eye treated, patients' gender, and age in pre-LASIK diagnostics.

Effects of laser in situ keratomileusis (LASIK) on corneal biomechanical measurements with the Corvis ST tonometer.

PubMed

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

2015-01-01

This study was initiated to evaluate biomechanical changes using the Corvis ST tonometer (CST) on the cornea after laser in situ keratomileusis (LASIK). University Medical Center Hamburg-Eppendorf, Germany, and Care Vision Refractive Centers, Germany. Retrospective cohort study. This retrospective study included 37 eyes of 37 refractive patients. All CST measurements were performed 1 day before surgery and at the 1-month follow-up examination. The LASIK procedure included mechanical flap preparation using a Moria SBK microkeratome and an Allegretto excimer laser platform. Statistically significant differences were observed for mean first applanation length, mean first and second deflection lengths, mean first and second deflection amplitudes, radius of curvature, and peak distance. Significant positive correlations were found between the change (Δ) of radius of curvature and manifest refraction spherical equivalent (MRSE), ablation depth, and Δintraocular pressure as well as between AD and ΔHC-time. Each diopter of myopic correction in MRSE resulted in an increase in Δradius of curvature of 0.2 mm. Several CST parameters were statistically significantly altered by LASIK, thereby indicating that flap creation, ablation, or both, significantly change the ability of the cornea to absorb or dissipate energy.

Posterior corneal topographic changes after partial flap during laser in situ keratomileusis

PubMed Central

Sharma, N; Rani, A; Balasubramanya, R; Vajpayee, R B; Pandey, R M

2003-01-01

Aim: To study the posterior corneal topographic changes in eyes with partial flaps during laser assisted in situ keratomileusis (LASIK). Methods: Case records of 16 patients, who had partial flap in one eye during LASIK (group 1) and uncomplicated surgery in the other eye (group 2), were studied. Following occurrence of partial flap intraoperatively, laser ablation was abandoned in all the eyes. A 160/180 μm flap was attempted during the initial procedure using the Hansatome microkeratome (Bausch & Lomb Surgicals, Munich, Germany). LASIK surgery in all cases was performed using a 180 μm plate, at the mean interval of 4.16 (SD 1.5) months following the initial procedure. None of the eyes had intraoperative complication during LASIK. Relative posterior corneal surface elevation above the best fit sphere (BFS) before the initial procedure, before, and after LASIK were compared using the Orbscan slit scanning corneal topography/pachymetry system. Results: Posterior corneal elevation was comparable in the two groups, both preoperatively (group 1; 16.4 (4.8) μm, group 2; 16.1 (4.8) μm) and after final surgery (group 1; 57.2 (15.6) μm, group 2; 54.3 (13.1) μm). In group 1 after occurrence of partial flap, the posterior corneal elevation was 16.9 (4.4) μm, and this increase was not significant statistically (p=0.4). On multiple linear regression analysis, residual bed thickness (p<0.001) was independently the significant determinant of final posterior corneal elevation in both groups. Conclusion: The inadvertent occurrence of partial flap during LASIK procedure does not contribute to the increase in posterior corneal elevation. PMID:12543743

Comparison of efficacy and safety of laser in situ keratomileusis using 2 femtosecond laser platforms in contralateral eyes.

PubMed

Rosman, Mohamad; Hall, Reece C; Chan, Cordelia; Ang, Andy; Koh, Jane; Htoon, Hla Myint; Tan, Donald T H; Mehta, Jodhbir S

2013-07-01

To compare the efficacy, predictability, and refractive outcomes of laser in situ keratomileusis (LASIK) using 2 femtosecond platforms for flap creation. Multisurgeon single center. Clinical trial. Bilateral femtosecond LASIK was performed using the Wavelight Allegretto Eye-Q 400 Hz excimer laser system. The Visumax femtosecond platform (Group 1) was used to create the LASIK flap in 1 eye, while the Intralase femtosecond platform (Group 2) was used to create the LASIK flap in the contralateral eye. The preoperative, 1-month, and 3-month postoperative visual acuities, refraction, and contrast sensitivity in the 2 groups were compared. The study enrolled 45 patients. Three months after femtosecond LASIK, 79.5% of eyes in Group 1 and 82.1% in Group 2 achieved an uncorrected distance visual acuity of 20/20 (P=.808). The mean efficacy index was 0.97 in Group 1 and 0.98 in Group 2 at 3 months (P=.735); 89.7% of eyes in Group 1 and 84.6% of eyes in Group 2 were within ± 0.50 diopter of emmetropia at 3 months (P=.498). No eye in either group lost more than 2 lines of corrected distance visual acuity. The mean safety index at 3 months was 1.11 in Group 1 and 1.10 in Group 2 (P=.570). The results of LASIK with both femtosecond lasers were similar, and both platforms produced efficacious and predictable LASIK outcomes. No author has a financial or proprietary interest in any material or method mentioned. Copyright © 2013 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.

Changes in Keratocyte Density and Visual Function Five Years After Laser In Situ Keratomileusis: Femtosecond Laser Versus Mechanical Microkeratome.

PubMed

McLaren, Jay W; Bourne, William M; Maguire, Leo J; Patel, Sanjay V

2015-07-01

To determine the effects of keratocyte loss on optical properties and vision after laser in situ keratomileusis (LASIK) with the flap created with a femtosecond laser or a mechanical microkeratome. Randomized clinical paired-eye study. Both eyes of 21 patients received LASIK for myopia or myopic astigmatism. One eye of each patient was randomized by ocular dominance to flap creation with a femtosecond laser and the other eye to flap creation with a mechanical microkeratome. Before LASIK and at 1, 3, and 6 months and 1, 3, and 5 years after LASIK, keratocyte density was measured using confocal microscopy, and high-contrast visual acuity and anterior corneal wavefront aberrations were measured by standard methods. At each visit, all variables were compared between methods of creating the flap and to the same variable before treatment using paired tests with Bonferroni correction for multiple comparisons. Keratocyte density in the flap decreased by 20% during the first year after LASIK and remained low through 5 years (P < .001). High-order wavefront aberrations increased and uncorrected visual acuity improved immediately after surgery, but these variables did not change further to 5 years. There were no differences in any variables between treatments. A sustained reduction in keratocyte density does not affect vision or optical properties of the cornea through 5 years after LASIK. The method of creating a LASIK flap does not influence the changes in keratocyte density in the flap. Copyright © 2015 Elsevier Inc. All rights reserved.

Changes in Keratocyte Density and Visual Function Five Years after Laser in situ Keratomileusis: Femtosecond Laser vs Mechanical Microkeratome

PubMed Central

McLaren, Jay W.; Bourne, William M.; Maguire, Leo J.; Patel, Sanjay V.

2015-01-01

Purpose To determine the effects of keratocyte loss on optical properties and vision after laser in situ keratomileusis (LASIK) with the flap created with a femtosecond laser or a mechanical microkeratome. Design Randomized clinical paired-eye study. Methods Both eyes of 21 patients received LASIK for myopia or myopic astigmatism. One eye of each patient was randomized by ocular dominance to flap creation with a femtosecond laser and the other eye to flap creation with a mechanical microkeratome. Before LASIK and at 1, 3, 6 months and 1, 3, and 5 years after LASIK, keratocyte density was measured by using confocal microscopy, and high-contrast visual acuity and anterior corneal wavefront aberrations were measured by standard methods. At each visit, all variables were compared between methods of creating the flap and to the same variable before treatment by using paired tests with Bonferroni correction for multiple comparisons. Results Keratocyte density in the flap decreased by 20% during the first year after LASIK and remained low through 5 years (p<0.001). High-order wavefront aberrations increased and uncorrected visual acuity improved immediately after surgery but these variables did not change further to five years. There were no differences in any variables between treatments. Conclusions A sustained reduction in keratocyte density does not affect vision or optical properties of the cornea through 5 years after LASIK. The method of creating a LASIK flap does not influence the changes in keratocyte density in the flap. PMID:25868758

Changes in ocular biomechanics after femtosecond laser creation of a laser in situ keratomileusis flap.

PubMed

Leccisotti, Antonio; Fields, Stefania V; Moore, Johnny; Shah, Sunil; Moore, Tara C B

2016-01-01

To evaluate ocular biomechanical parameters with the Corvis ST, a noncontact tonometer combined with an ultra-high-speed Scheimpflug camera, before and after creation of a femtosecond laser-created laser in situ keratomileusis (LASIK) flap. Private practice, Siena, Italy. Prospective consecutive study. Right eyes of patients having LASIK were assessed with the dynamic Scheimpflug camera before and after femtosecond laser (LDV Z4) flap creation but before mechanical flap lifting. Twenty-eight eyes of 28 patients were evaluated. Before flap creation, the mean values on the dynamic Scheimpflug camera were intraocular pressure (IOP), 15.04 mm Hg ± 3.99 (SD); central pachymetry, 550.8 ± 101.0 μm; applanation 1 length, 1.721 ± 0.134 mm; applanation 2 length, 1.674 ± 0.287 mm; applanation 1 velocity, 0.126 ± 0.031 m/s; and deflection amplitude, 1.039 ± 0.141 mm. After flap creation, the mean values were IOP, 16.10 ± 3.11 mm Hg (95% confidence interval [CI], 0.44-1.78; P < .05); central pachymetry, 561.8 ± 35.9 μm (95% CI, -28.9 to 50.9; P = .21); applanation 1 length, 1.789 ± 0.1492 mm (95% CI, 0.003-0.134; P < .05); applanation 2 length, 1.759 ± 0.259 mm (95% CI, -0.005 to 0.173; P = .08); applanation 1 velocity, 0.136 ± 0.022 m/s (95% CI, 0.001-0.017; P < .05); and deflection amplitude, 1.029 ± 0.151 mm (95% CI: -0.043 to 0.025; P = .34). The dynamic Scheimpflug camera showed changes in biomechanical properties after femtosecond creation of a LASIK flap as indicated by an increased applanation 1 length and applanation 1 velocity. 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.

Goblet cell response after photorefractive keratectomy and laser in situ keratomileusis

PubMed Central

Ryan, Denise S.; Bower, Kraig S.; Sia, Rose K.; Shatos, Marie A.; Howard, Robin S.; Mines, Michael J.; Stutzman, Richard D.; Dartt, Darlene A.

2017-01-01

PURPOSE To determine whether patients without dry eye preoperatively have an altered conjunctival goblet cell density and mucin secretion postoperatively and to explore what factors affect changes in goblet cell density and mucin secretion. SETTING The former Walter Reed Army Medical Center, Washington, DC, USA. DESIGN Prospective nonrandomized clinical study. METHODS Impression cytology was used to determine conjunctival goblet cell density before and 1 week, 1 month, and 3 months after photorefractive keratectomy (PRK) or laser in situ keratomileusis (LASIK). The McMonnies questionnaire, Schirmer test, tear breakup time, corneal sensitivity, rose bengal staining, and computerized videokeratoscopy were also performed to assess tear-film and ocular-surface health. RESULTS The ratio of goblet cell to total cells changed postoperatively from baseline in both groups (P < .001). The most significant change was a median 29% decrease 1 month postoperatively. However, there were no significant differences between groups over time (P = .772). The ratio of filled goblet cell to total goblet cell did not change significantly over the same time period (P = .128), and there were no significant differences between the PRK group and the LASIK group over time (P = .282). CONCLUSIONS Patients without apparent dry eye had altered conjunctival goblet cell population after PRK or LASIK. The conjunctival goblet cell population tended to decrease in the early postoperative period after either surgery and was most affected by preoperative goblet cell density. The changes in the tear film and ocular surface did not seem to affect goblet cell mucin secretion after either procedure. PMID:27531295

Laser-Assisted Subepithelial Keratectomy versus Laser In Situ Keratomileusis in Myopia: A Systematic Review and Meta-Analysis

PubMed Central

Zhao, Li-Quan; Zhu, Huang; Li, Liang-Mao

2014-01-01

This systematic review was to compare the clinical outcomes between laser-assisted subepithelial keratectomy (LASEK) and laser in situ keratomileusis (LASIK) for myopia. Primary parameters included mean manifest refraction spherical equivalent (MRSE), MRSE within ±0.50 diopters, uncorrected visual acuity (UCVA) ≥20/20, and loss of ≥1 line of best-corrected visual acuity (BCVA). Secondary parameters included flap complications and corneal haze. Twelve clinical controlled trials were identified and used for comparing LASEK (780 eyes) to LASIK (915 eyes). There were no significant differences in visual and refractive outcomes between the two surgeries for low to moderate myopia. The incidence of loss of ≥1 line of BCVA was significantly higher in moderate to high myopia treated by LASEK than LASIK in the mid-term and long-term followup. The efficacy (MRSE and UCVA) of LASEK appeared to be a significant worsening trend in the long-term followup. Corneal haze was more severe in moderate to high myopia treated by LASEK than LASIK in the mid-term and long-term followup. The flap-related complications still occurred in LASIK, but the incidence was not significantly higher than that in LASEK. LASEK and LASIK were safe and effective for low to moderate myopia. The advantage of LASEK was the absence of flap-related complications, and such procedure complication may occur in LASIK and affect the visual results. The increased incidence of stromal haze and regression in LASEK significantly affected the visual and refractive results for high myopia. PMID:24977054

Photorefractive keratectomy (PRK) versus laser-assisted in-situ keratomileusis (LASIK) for myopia.

PubMed

Shortt, A J; Allan, B D S

2006-04-19

Myopia (also known as short-sightedness or near-sightedness) is an ocular condition in which the refractive power of the eye is greater than is required, resulting in light from distant objects being focused in front of the retina instead of directly on it. The two most commonly used surgical techniques to permanently correct myopia are photorefractive keratectomy (PRK) and laser-assisted in-situ keratomileusis (LASIK). The aim of this review was to compare the effectiveness and safety of PRK and LASIK for correction of myopia. We searched the Cochrane Central Register of Controlled Trials (CENTRAL) in The Cochrane Library (2005, Issue 3), MEDLINE (1966 to September 2005), EMBASE (1980 to September 2005) and LILACs (1982 to 3 November 2005). We also searched the reference lists of the studies and the Science Citation Index. We included randomised controlled trials comparing PRK and LASIK for correction of any degree of myopia. We also included data on adverse events from prospective multicentre consecutive case series in the Food and Drugs Administration (FDA) trials database (http//www.fda.gov/cdrh/LASIK/lasers.htm). Two authors independently assessed trial quality and extracted data. Data were summarised using odds ratio and mean difference. Odds ratios were combined using a random-effects model after testing for heterogeneity. This review included six randomised controlled trials involving a total of 417 eyes, of which 201 were treated with PRK and 216 with LASIK. We found that although LASIK gives a faster visual recovery than PRK, the effectiveness of these two procedures is comparable. We found some evidence that LASIK may be less likely than PRK to result in loss of best spectacle-corrected visual acuity. LASIK gives a faster visual recovery than PRK but the effectiveness of these two procedures is comparable. Further trials using contemporary techniques are required to determine whether LASIK and PRK are equally safe.

Traumatic corneal flap displacement after laser in situ keratomileusis (LASIK)

PubMed Central

Tsai, Tsung-Han; Peng, Kai-Ling; Lin, Chien-Jen

2017-01-01

Background Laser in situ keratomileusis (LASIK) is the most common and popular procedure performed for the correction of refractive errors in the last two decades. We report a case of traumatic flap displacement with flap folding which occurred 3 years after LASIK was performed. Previous literature suggests that vision prognosis would be closely related to proper and prompt management of traumatic flap displacement with flap folding 3 years after LASIK. Case presentation A 23-year-old female presented to our hospital who had undergone uneventful LASIK in both eyes 3 years prior. Unfortunately, she had suffered a blunt trauma in her right eye in a car accident. A late onset of corneal flap displacement was found with upper and lower portion of the flap being folded inside the corneal bed. Surgical intervention for debridement with subsequent reposition of corneal flap was performed as soon as possible in the operating room. A bandage contact lens was placed, and topical antibiotic and corticosteroids were given postoperatively. Two days after the operation, the displaced corneal flap was found to be well attached smoothly on the corneal bed without folds. The best-corrected visual acuity was 6/6 with refraction of −0.75 D to 1.0 D ×175° in her right eye 1 month later. Literature review We reviewed a total of 19 published cases of late-onset traumatic flap dislocations or displacements after LASIK with complete data from 2000 to 2014. Conclusion Traumatic displacement of corneal flaps after LASIK may occur after blunt injury with specific direction of force to the flap margin, especially tangential one. According to the previous literature, late-onset traumatic flap displacement may happen at any time after LASIK and be caused by various types of injuries. Fortunately, good visual function could mostly be restored with immediate and proper management. PMID:28458585

Traumatic corneal flap displacement after laser in situ keratomileusis (LASIK).

PubMed

Tsai, Tsung-Han; Peng, Kai-Ling; Lin, Chien-Jen

2017-01-01

Laser in situ keratomileusis (LASIK) is the most common and popular procedure performed for the correction of refractive errors in the last two decades. We report a case of traumatic flap displacement with flap folding which occurred 3 years after LASIK was performed. Previous literature suggests that vision prognosis would be closely related to proper and prompt management of traumatic flap displacement with flap folding 3 years after LASIK. A 23-year-old female presented to our hospital who had undergone uneventful LASIK in both eyes 3 years prior. Unfortunately, she had suffered a blunt trauma in her right eye in a car accident. A late onset of corneal flap displacement was found with upper and lower portion of the flap being folded inside the corneal bed. Surgical intervention for debridement with subsequent reposition of corneal flap was performed as soon as possible in the operating room. A bandage contact lens was placed, and topical antibiotic and corticosteroids were given postoperatively. Two days after the operation, the displaced corneal flap was found to be well attached smoothly on the corneal bed without folds. The best-corrected visual acuity was 6/6 with refraction of -0.75 D to 1.0 D ×175° in her right eye 1 month later. We reviewed a total of 19 published cases of late-onset traumatic flap dislocations or displacements after LASIK with complete data from 2000 to 2014. Traumatic displacement of corneal flaps after LASIK may occur after blunt injury with specific direction of force to the flap margin, especially tangential one. According to the previous literature, late-onset traumatic flap displacement may happen at any time after LASIK and be caused by various types of injuries. Fortunately, good visual function could mostly be restored with immediate and proper management.

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

Epithelial ingrowth following laser in situ keratomileusis (LASIK): prevalence, risk factors, management and visual outcomes

PubMed Central

Srinivasan, Sathish; Danjoux, Jean-Pierre

2018-01-01

The number of laser in situ keratomileusis (LASIK) procedures is continuing to rise. Since its first application for correcting simple refractive errors over 25 years ago, the role of LASIK has extended to treat other conditions, including postkeratoplasty astigmatism/ametropia, postcataract surgery refractive error and presbyopia, among others. The long-term effectiveness, predictability and safety have been well established by many large studies. However, due to the creation of a potential interface between the flap and the underlying stroma, interface complications such as infectious keratitis, diffuse lamellar keratitis and epithelial ingrowth may occur. Post-LASIK epithelial ingrowth (PLEI) is an uncommon complication that usually arises during the early postoperative period. The reported incidence of PLEI ranged from 0%–3.9% in primary treatment to 10%–20% in retreatment cases. It can cause a wide spectrum of clinical presentations, ranging from asymptomatic interface changes to severe visual impairment and flap melt requiring keratoplasty. PLEI can usually be treated with mechanical debridement of the affected interface; however, additional interventions, such as alcohol, mitomycin C, fibrin glue, ocular hydrogel sealant, neodymium:yttriumaluminum garnet laser and amniotic membrane graft, may be required for recurrent or refractory cases. The aims of this review are to determine the prevalence and risk factors of PLEI; to describe its pathogenesis and clinical features and to summarise the therapeutic armamentarium and the visual outcome of PLEI. PMID:29657982

Epithelial ingrowth following laser in situ keratomileusis (LASIK): prevalence, risk factors, management and visual outcomes.

PubMed

Ting, Darren Shu Jeng; Srinivasan, Sathish; Danjoux, Jean-Pierre

2018-01-01

The number of laser in situ keratomileusis (LASIK) procedures is continuing to rise. Since its first application for correcting simple refractive errors over 25 years ago, the role of LASIK has extended to treat other conditions, including postkeratoplasty astigmatism/ametropia, postcataract surgery refractive error and presbyopia, among others. The long-term effectiveness, predictability and safety have been well established by many large studies. However, due to the creation of a potential interface between the flap and the underlying stroma, interface complications such as infectious keratitis, diffuse lamellar keratitis and epithelial ingrowth may occur. Post-LASIK epithelial ingrowth (PLEI) is an uncommon complication that usually arises during the early postoperative period. The reported incidence of PLEI ranged from 0%-3.9% in primary treatment to 10%-20% in retreatment cases. It can cause a wide spectrum of clinical presentations, ranging from asymptomatic interface changes to severe visual impairment and flap melt requiring keratoplasty. PLEI can usually be treated with mechanical debridement of the affected interface; however, additional interventions, such as alcohol, mitomycin C, fibrin glue, ocular hydrogel sealant, neodymium:yttriumaluminum garnet laser and amniotic membrane graft, may be required for recurrent or refractory cases. The aims of this review are to determine the prevalence and risk factors of PLEI; to describe its pathogenesis and clinical features and to summarise the therapeutic armamentarium and the visual outcome of PLEI.

Comparison of performances of femtosecond laser and microkeratome for thin-flap laser in situ keratomileusis.

PubMed

Kasetsuwan, Ngamjit; Satitpitakul, Vannarut; Puangsricharern, Vilavun; Reinprayoon, Usanee; Pariyakanok, Lalida

2016-08-01

To compare the clinical outcomes of femtosecond laser (FS) and microkeratome (MK) for thin-flap in situ keratomileusis (LASIK). Data from patients with moderate to high myopia (spherical equivalent, >-4 diopters [D]) who underwent thin-flap LASIK using FS (199 eyes/110 patients) and MK (157 eyes/86 patients) were analyzed in this retrospective study. Preoperative and postoperative data were recorded from day 1 and months 1 and 3, postoperatively. Visual and refractive outcomes were compared for efficacy, safety, predictability, stability, and the efficacy and safety indices. Three months postoperatively, more eyes in the FS group had an uncorrected distance visual acuity (UCVA) of 20/40 or better compared to MK group (relative risk [RR] 1.01, 95% confidence interval [CI], 0.97-1.05, P = 0.58); significantly more eyes in FS group had an UCVA of 20/20 or better (RR, 1.26, 95%CI, 1.08-1.48, P = 0.003). Intraoperative bleeding occurred in 5% and 36.7%, respectively, of FS and MK groups. There were no significant differences in the refractive predictability within spherical equivalents of 0.5 D (FS, 72%; MK, 63%) and 1.0 D (FS, 90%; MK, 86%). Both groups showed good stability 3 months, postoperatively. The efficacy index in FS group was 113.4%; that in MK group was 102.5% at 3 months postoperatively (P < 0.05). The safety indices for FS and MK groups at 3 months postoperatively were 116.4% and 108.2%, respectively (P < 0.05). Both methods of thin-flap created LASIK were effective, safe, predicable, and stable. FS group had significant improvements in efficacy and safety, confirmed by the efficacy and safety indices, compared to MK group. Lasers Surg. Med. 48:596-601, 2016. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

Comparison of DLK incidence after laser in situ keratomileusis associated with two femtosecond lasers: Femto LDV and IntraLase FS60

PubMed Central

Tomita, Minoru; Sotoyama, Yuko; Yukawa, Satoshi; Nakamura, Tadayuki

2013-01-01

Purpose To compare the incidence of diffuse lamellar keratitis (DLK) after laser in situ keratomileusis (LASIK) with flap creation using the Femto LDV and IntraLase™ FS60 femtosecond lasers.0 Methods A total of 818 consecutive myopic eyes had LASIK performed using either Femto LDV or IntraLase FS60 for flap creation. The same excimer laser, the Allegretto Wave® Eye-Q Laser, was used for correcting refractive errors for all patients. In the preoperative examination, uncorrected distance visual acuity, corrected distance visual acuity, and manifest refraction spherical equivalent were measured. At the postop examination, the same examinations were performed along with a slit-lamp biomicroscopic examination, and patients with DLK were classified into stages. For the statistical analysis of the DLK occurrence rate and the visual and refractive outcomes, the Mann-Whitney’s U-test was used. Results In the Femto LDV group with 514 eyes, 42 (8.17%) had DLK. In the IntraLase FS60 group with 304 eyes, 114 (37.5%) had DLK. There was a statistically significant difference in the DLK incidence rate between these groups (P < 0.0001). Both groups had excellent visual and refractive outcomes. Although low levels of DLK were observed for both groups, they did not affect visual acuity. Conclusion While there were significantly fewer incidences of low level DLK when using Femto LDV, neither femtosecond laser induced high levels of DLK, and any postoperative DLK cleared up within 1 week. Therefore, both lasers provide excellent results, with no clinical differences, and both excel at flap creation for LASIK. PMID:23874077

Patient-reported outcomes 5 years after laser in situ keratomileusis.

PubMed

Schallhorn, Steven C; Venter, Jan A; Teenan, David; Hannan, Stephen J; Hettinger, Keith A; Pelouskova, Martina; Schallhorn, Julie M

2016-06-01

To assess vision-related, quality-of-life outcomes 5 years after laser in situ keratomileusis (LASIK) and determine factors predictive of patient satisfaction. Optical Express, Glasgow, Scotland. Retrospective case series. Data from patients who had attended a clinical examination 5 years after LASIK were analyzed. All treatments were performed using the Visx Star S4 IR excimer laser. Patient-reported satisfaction, the effect of eyesight on various activities, visual phenomena, and ocular discomfort were evaluated 5 years postoperatively. Multivariate regression analysis was performed to determine factors affecting patient satisfaction. The study comprised 2530 patients (4937 eyes) who had LASIK. The mean age at the time of surgery was 42.4 years ± 12.5 (SD), and the preoperative manifest spherical equivalent ranged from -11.0 diopters (D) to +4.88 D. Five years postoperatively, 79.3% of eyes were within ±0.50 D of emmetropia and 77.7% of eyes achieved monocular uncorrected distance visual acuity (UDVA) and 90.6% of eyes achieved binocular UDVA of 20/20 or better. Of the patients, 91.0% said they were satisfied with their vision and 94.9% did not wear distance correction. Less than 2.0% of patients noticed visual phenomena, even with spectacle correction. Major predictors of patient satisfaction 5 years postoperatively were postoperative binocular UDVA (37.6% variance explained by regression model), visual phenomena (relative contribution of 15.0%), preoperative and postoperative sphere and their interactions (11.6%), and eyesight-related difficulties with various activities such as night driving, outdoor activities, and reading (10.2%). Patient-reported quality-of-life and satisfaction rates remained high 5 years after LASIK. Uncorrected vision was the strongest predictor of satisfaction. Dr. S.C. Schallhorn is a consultant to Abbott Medical Optics, Inc., Zeiss Meditec AG, and Autofocus Inc. and a global medical director for Optical Express. No other

INTACS before or after laser in situ keratomileusis: correction of thin corneas with moderately high myopia.

PubMed

Ito, Mitsutoshi; Arai, Hiroyuki; Fukumoto, Teruki; Toda, Ikuko; Tsubota, Kazuo

2004-01-01

Intrastromal corneal ring segments (INTACS Micro-Thin Prescription Inserts by Addition Technologies, Fremont, Calif) were inserted as a combined surgery with laser in situ keratomileusis (LASIK) in six eyes with thin corneas to correct moderately high myopia. INTACS were implanted before LASIK (INTACS-LASIK) in three eyes and after LASIK (LASIK-INTACS) in three eyes. Mean preoperative manifest spherical equivalent refraction was -7.88 diopters. Mean follow-up was 306 days. No intraoperative complications occurred. The LASIK-INTACS eyes were slightly more overcorrected than the INTACS-LASIK eyes because of the enhanced performance of INTACS in the thinned corneal tissue. Induced astigmatism by INTACS per se was less in the LASIK-INTACS eyes than in the INTACS-LASIK eyes. At last examination, uncorrected visual acuity was better than 20/25 in all eyes. Best spectacle-corrected visual acuity was within 1 line of the preoperative value in all eyes. Both methods resulted in significant improvement in visual acuity and refraction. Based on our limited experience, however, LASIK followed by INTACS is preferred for reasons of safety, convenience, and lower induced cylinder.

Diffuse lamellar keratitis after laser in situ keratomileusis with the Moria LSK-One and Carriazo-Barraquer microkeratomes.

PubMed

Thammano, Pavika; Rana, Azhar N; Talamo, Jonathan H

2003-10-01

To assess risk factors for and incidence of diffuse lamellar keratitis (DLK) and to investigate whether microkeratome design is associated with the incidence of DLK. The Laser Eye Consultants of Boston, Boston and Waltham, Massachusetts, USA. In a retrospective nonrandomized comparative study, 1122 consecutive primary laser in situ keratomileusis (LASIK) treatments (584 patients) were analyzed to determine the incidence of DLK using 2 different microkeratome designs (Moria LSK-One [LSK] and Moria Carriazo-Barraquer [C-B]). The incidence of DLK was as determined by clinical signs. The overall incidence of DLK was 2.23%. The incidence in the LSK and C-B groups was 1.09% and 4.38%, respectively, with a statistically significant difference in incidence between the 2 groups (P<.01). Epithelial irregularities increased the risk for DLK. There was no significant statistical difference in sex, age, operating room location, type of laser, or time of day the surgery was performed between the 2 groups or between eyes that had DLK and eyes without DLK. The incidence of DLK using the C-B microkeratome fell significantly after May 2000, when new cleaning methods for this device were introduced. Different microkeratomes and how they are maintained may influence the incidence of DLK. Diffuse lamellar keratitis is more common after LASIK in a setting of epithelial irregularities, whether or not an actual epithelial defect is created.

Contralateral eye comparison on changes in visual field following laser in situ keratomileusis vs photorefractive keratectomy for myopia: a randomized clinical trial.

PubMed

Mostafaei, A; Sedgipour, M R; Sadeghi-Bazargani, H

2009-12-01

Study purpose was to compare the changes of Visual Field (VF) during laser in situ Keratomileusis (LASIK) VS photorefractive keratectomy (PRK). This randomized, double blind, study involved 54 eyes of 27 Myopia patients who underwent LASIK or PRK procedures for contralateral eyes in each patient. Using Humphrey 30-2 SITA standard, the Mean Defect (MD) and Pattern Standard Deviation (PSD) were evaluated preoperatively and three months after surgery. At the same examination optical zone size, papillary and corneal diameters were also evaluated. There was no clinically significant difference in PSD and MD measurements between treated eyes with LASIK or PRK in any zone pre and postoperatively. VF may not be affected by corneal changes induced by LASIK or PRK three months after surgery.

Safety, efficacy, predictability and stability of laser in situ keratomileusis (LASIK) with a 1000-Hz scanning spot excimer laser.

PubMed

Khoramnia, Ramin; Salgado, Josefina P; Wuellner, Christian; Donitzky, Christof; Lohmann, Chris P; Winkler von Mohrenfels, Christoph

2012-09-01

To evaluate the safety, efficacy, predictability and stability of laser in situ keratomileusis (LASIK) with a 1000-Hz scanning spot excimer laser (Concept System 1000; WaveLight GmbH, Erlangen, Germany). LASIK was performed on twenty eyes with myopia or myopic astigmatism (mean spherical equivalent refraction: -3.97±1.72 dioptres (D); mean cylinder: -0.84±0.77 D) using a microkeratome for flap creation and the Concept System 1000 for photoablation. Patients were examined preoperatively as well as 1, 3 and 6 months after the treatment. Manifest sphere and cylinder, uncorrected (UCDVA) and best corrected (BCDVA) distance visual acuity, corneal topography and pachymetry were analysed. We observed no adverse events that might have been associated with the use of a repetition rate of 1000 Hz. All eyes maintained or had improved BCDVA at 6 months after treatment when compared to preoperative values. Six months after LASIK, UCDVA was 20/20 or better in 85% and 20/25 or better in 100% of the eyes. The spherical equivalent refraction was within ±0.50 D in 95% of the eyes at 6 months after surgery. The refraction stayed stable over time; 95% of the eyes changed<0.5 D postoperatively. LASIK with the prototype 1000-Hz excimer laser was safe, efficient and predictable. The postoperative refraction was stable over time. There were no specific clinical side-effects that might be associated with the use of such a high repetition rate. © 2011 The Authors. Acta Ophthalmologica © 2011 Acta Ophthalmologica Scandinavica Foundation.

Efficacy and perioperative timing of bromfenac in the management of ocular discomfort after femtosecond laser-assisted laser in situ keratomileusis.

PubMed

Cleaveland, Nathan A; De Mann, Derek W; Carlson, Neil E; Keil, Michael L

2017-02-01

To evaluate the safety, efficacy, and appropriate perioperative timing of the use of topical bromfenac ophthalmic solution 0.07% after femtosecond laser-assisted laser in situ keratomileusis (LASIK). Keil LASIK Vision Center, Grand Rapids, Michigan, USA. Prospective case series. Ocular discomfort was assessed 1, 2, and 5 hours postoperatively and the following morning using the Ocular Comfort Grading Assessment in patients treated with topical bromfenac 0.07% or artificial tears just before, just after, or before and after femtosecond laser-assisted LASIK. Visual outcomes and complications were noted up to 24 hours. The study enrolled 64 patients (120 eyes). Patients who were treated with bromfenac 0.07% just before or before and after femtosecond laser-assisted LASIK showed the greatest statistically significant decrease in several discomfort scores within the first few hours in comparison with the control group. Two hours after surgery, the majority of patients who were treated before and after LASIK were sleeping comfortably. There were no significant differences in visual acuity; 1 day postoperatively, the uncorrected distance visual acuity was 20/20 in 106 eyes (89%) and 20/25 or better in 116 eyes (97%). At 3 months, all patients had binocular distance visual acuity of 20/20 or better and 86% of patients had 20/15 or better. Ocular discomfort after femtosecond laser-assisted LASIK was reduced with a single dose of topical bromfenac 0.07% given immediately before surgery or given just before and after surgery and was typically minimal in all groups the morning after surgery. Copyright © 2017 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.

Clinical outcomes of wavefront-guided laser in situ keratomileusis: 6-month follow-up.

PubMed

Aizawa, Daisuke; Shimizu, Kimiya; Komatsu, Mari; Ito, Misae; Suzuki, Masanobu; Ohno, Koji; Uozato, Hiroshi

2003-08-01

To evaluate the clinical outcomes 6 months after wavefront-guided laser in situ keratomileusis (LASIK) for myopia in Japan. Department of Ophthalmology, Sanno Hospital, Tokyo, Japan. This prospective study comprised 22 eyes of 12 patients treated with wavefront-guided LASIK who were available for evaluation at 6 months. The mean patient age was 31.2 years +/- 8.4 (SD) (range 23 to 50 years), and the mean preoperative spherical equivalent refraction was -7.30 +/- 2.72 diopters (D) (range -2.75 to -11.88 D). In all cases, preoperative wavefront analysis was performed with a Hartmann-Shack aberrometer and the Technolas 217z flying-spot excimer laser system (Bausch & Lomb) was used with 1.0 mm and 2.0 mm spot sizes and an active eye tracker with a 120 Hz tracking rate. The clinical outcomes of wavefront-guided LASIK were evaluated in terms of safety, efficacy, predictability, stability, complications, and preoperative and postoperative aberrations. At 6 months, 10 eyes had no change in best spectacle-correct visual acuity and 10 gained 1 or more lines. The safety index was 1.11 and the efficacy index, 0.82. Slight undercorrections were observed in highly myopic eyes. In all eyes, the postoperative refraction tended slightly toward myopia for 3 months and stabilized after that. No complication such as epithelial ingrowth, diffuse lamellar keratitis, or infection was observed. Comparison of the preoperative and postoperative aberrations showed that 2nd-order aberrations decreased and higher-order aberrations increased. In the 3rd order, aberrations increased in the high-myopia group (-6.0 D or worse) and decreased in the low to moderate-myopia group (better than -6.0 D). Wavefront-guided LASIK was a good option for refractive surgery, although a longer follow-up in a larger study is required.

Topographically supported customized ablation for the management of decentered laser in situ keratomileusis.

PubMed

Kymionis, George D; Panagopoulou, Sophia I; Aslanides, Ioannis M; Plainis, Sotiris; Astyrakakis, Nikolaos; Pallikaris, Ioannis G

2004-05-01

To evaluate the efficacy, predictability, and safety of topographically supported customized ablations (TOSCAs) for decentered ablations following laser in situ keratomileusis (LASIK). Prospective nonrandomized clinical trial. Nine patients (11 eyes) with LASIK-induced decentered ablations underwent TOSCA following flap lifting. Topographically supported customized ablation was performed using a corneal topographer to obtain a customized ablation profile, combined with a flying spot laser. Mean follow-up was 9.22 +/- 2.82 months (range 6-12 months). No intra- or postoperative complications were observed. Manifest refraction (spherical equivalent) did not change significantly (pre-TOSCA: -0.14 +/- 1.58 diopters [range, -1.75 to +3.00 diopters] to +0.46 +/- 1.02 diopters [range, -1.00 to +1.75 diopters]; P =.76), whereas there was a statistically significant reduction in the refractive astigmatism (pre-TOSCA: -1.55 +/- 0.60 diopters [range, -3.00 to -0.75 diopters] to -0.70 +/- 0.56 diopters [range, -2.00 to -0.25 diopters]; P =.003). Mean uncorrected visual acuity improved significantly (P <.001) from 0.45 +/- 0.16 (range, 0.2-0.7) to 0.76 +/- 0.29 (range, 0.2-1.2) at last follow-up. Mean best-corrected visual acuity improved from 0.74 +/- 0.22 (range, 0.4-1.0) to 0.95 +/- 0.20 (range, 0.6-1.2; P =.002). Eccentricity showed a statistically significant reduction after TOSCA treatment (pre-TOSCA: 1.59 +/- 0.46 mm [range, 0.88-2.23 mm]; post-TOSCA: 0.29 +/- 0.09 mm [range, 0.18-0.44 mm]; P <.001). In our small sample, enhancement LASIK procedures with TOSCA appear to improve uncorrected and best-corrected visual acuity as well as eccentricity in patients with LASIK-induced decentered ablation.

Laser Eye Surgery: MedlinePlus Health Topic

MedlinePlus

... types of laser eye surgery. LASIK - laser-assisted in situ keratomileusis - is one of the most common. Many ... Laser (National Institutes of Health) ClinicalTrials.gov: Laser In Situ Keratomileusis (LASIK) (National Institutes of Health) ClinicalTrials.gov: ...

Interface Fluid Syndrome After Laser In Situ Keratomileusis (LASIK) Because of Fuchs Endothelial Dystrophy Reversed by Descemet Membrane Endothelial Keratoplasty (DMEK).

PubMed

Luceri, Salvatore; Baksoellah, Zainab; Ilyas, Abbas; Baydoun, Lamis; Melles, Gerrit R J

2016-12-01

To describe a case that developed "interface fluid syndrome" after previous laser in situ keratomileusis (LASIK) because of Fuchs endothelial dystrophy (FED), which was reversed by Descemet membrane endothelial keratoplasty (DMEK). A 58-year-old male patient presented with bilateral visual impairment owing to FED and visually significant cataract. Cataract surgery was carried out in both eyes followed by DMEK in his left eye. After cataract surgery, visual acuity did not improve sufficiently because corneal thickness increased and a fine cleft with interface fluid developed between the LASIK-flap and the residual stromal bed. After uneventful DMEK in his left eye, the fluid resolved within a week and visual acuity improved rapidly. This case demonstrates that "interface fluid syndrome" after LASIK caused by concomitant endothelial dysfunction may be reversed by DMEK allowing fast visual recovery.

Twelve-Year Follow-Up of Laser In Situ Keratomileusis for Moderate to High Myopia.

PubMed

Ikeda, Tetsuya; Shimizu, Kimiya; Igarashi, Akihito; Kasahara, Sumie; Kamiya, Kazutaka

2017-01-01

To assess the long-term clinical outcomes of conventional laser in situ keratomileusis (LASIK) for moderate to high myopia. We retrospectively examined sixty-eight eyes of 37 consecutive patients who underwent conventional LASIK for the correction of myopia (-3.00 to -12.75 diopters (D)). At 3 months and 1, 4, 8, and 12 years postoperatively, we assessed the safety, efficacy, predictability, stability, mean keratometry, central corneal thickness, and adverse events. The safety and efficacy indices were 0.82 ± 0.29 and 0.67 ± 0.37, respectively, 12 years postoperatively. At 12 years, 53% and 75% of the eyes were within 0.5 and 1.0 D, respectively, of the targeted correction. Manifest refraction changes of -0.74 ± 0.99 D occurred from 3 months to 12 years after LASIK ( p < 0.001). We found a significant correlation of refractive regression with the changes in keratometric readings from 3 months to 12 years postoperatively (Pearson correlation coefficient, r = -0.28, p = 0.02), but not with the changes in central corneal thickness ( r = -0.08, p = 0.63). No vision-threatening complications occurred in any case. Conventional LASIK offered good safety outcomes during the 12-year observation period. However, the efficacy and the predictability gradually decreased with time owing to myopic regression in relation to corneal steepening.

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

Defining the content of patient questionnaires: reasons for seeking laser in situ keratomileusis for myopia.

PubMed

Khan-Lim, Doreen; Craig, Jennifer P; McGhee, Charles N J

2002-05-01

To determine the relative importance of patients' motives for having laser in situ keratomileusis (LASIK) for myopia. The Corneal Diseases and Excimer Laser Research Unit, University of Dundee, Ninewells Hospital and Medical School, Dundee, Scotland. Twenty-one cards printed with potential reasons for having LASIK and 3 blank cards for respondents to include additional motives were posted to 71 patients who had myopic LASIK. The cards were ranked by each respondent in order of personal importance and returned for analysis. The response rate was 77.5%. The mean age of the 19 male and 37 female respondents was 41.7 years +/- 9.3 (SD) and the mean preoperative spherical equivalent, -9.26 +/- 4.58 diopters. The primary reasons for seeking treatment (percentage of respondents ranking topic within the top 5) were improvement of unaided social vision (69.1%), intolerance to spectacles/contact lenses (65.5%), and freedom from spectacles/contact lenses (61.8%). Almost 70% of respondents ranked 1 of these reasons as the most important. General inconvenience of spectacles/contact lenses and the desire to pursue sports and leisure activities also ranked high (52.7% and 36.4%, respectively). Consistent with previous work, better unaided vision, combined with the inconvenience of or intolerance to spectacles or contact lenses, provided the main incentives to have LASIK for myopia, while improved cosmesis was relatively unimportant (29.1%). The results of this study will allow the design of satisfaction questionnaires that are better directed toward establishing satisfaction of specific, relevant functional and psychological aspects of refractive surgery that are important to patients.

Delayed onset Mycobacterium intracellulare keratitis after laser in situ keratomileusis: A case report and literature review.

PubMed

Ko, JaeSang; Kim, Se Kyung; Yong, Dong Eun; Kim, Tae-Im; Kim, Eung Kweon

2017-12-01

Infectious keratitis is a relatively uncommon but potentially sight-threatening complication of laser in situ keratomileusis (LASIK). Mycobacterial keratitis is usually regarded as late onset keratitis among post-LASIK keratitis. There has been no documented case of Mycobacterium intracellulare post-LASIK keratitis of a long-latent period. A 36-year-old man was referred to our out-patient clinic, for persistent corneal epithelial defect with intrastromal infiltration. He had undergone uneventful bilateral LASIK procedure 4 years before. He complained decreased vision, accompanied by ocular pain, photophobia, and redness in his left eye for 7 months. Lamellar keratectomy was taken using femtosecond laser. Bacterial culture with sequenced bacterial 16s ribosomal DNA confirmed the organism to be M intracellulare. After 3 months of administration of topical clarithromycin, amikacin, and moxifloxacin, the corneal epithelial defect was resolved and the infiltration was much improved. However, newly developed diffuse haziness with surrounding granular infiltration in the central cornea was noted. Drug toxicity was suspected and topical moxifloxacin was discontinued, resulting in resolution of the diffuse haze with infiltration. The patient was followed up regularly without medication thereafter and recurrence was not found for 7 years. This case presents the first case of M intracellulare keratitis after LASIK. LASIK surgeons should aware that post-LASIK keratitis can develop long after the operation and careful suspicion of infectious disease with meticulous diagnostic test is needed. Copyright © 2017 The Authors. Published by Wolters Kluwer Health, Inc. All rights reserved.

Myopic keratomileusis by excimer laser on a lathe.

PubMed

Ganem, S; Aron-Rosa, D; Gross, M; Rosolen, S

1994-01-01

We designed an excimer laser keratomileusis delivery system to increase the regularity of the refractive cut surface and allow greater precision in the level and shape of the ablated zone. A parallel faced corneal disc was produced by microkeratectomy from six human eyes and surgical keratectomy in 12 beagle corneas. A 193-nanometer excimer laser that was used to project an oval beam onto the corneal disc was rotated on a flat surface to ensure overlapping of the ovally ablated areas between pulses. Electron microscopy of eye bank lenticules demonstrated a circular smooth regularly concave ablation zone. Histological examination of nine clear corneas confirmed thinning of the stroma without fibroblastic reaction and no epithelial hypertrophy. Mean preoperative corneal power of 43.15 +/- 2.18 decreased postoperatively to 33.61 +/- 2.34. The new technique of excimer laser keratomileusis has the advantage of a cut surface smoother and the clear zone is devoid of the stepwise concavity and irregularity seen in diaphragm based photoablation delivery systems.

Twelve-Year Follow-Up of Laser In Situ Keratomileusis for Moderate to High Myopia

PubMed Central

Ikeda, Tetsuya; Igarashi, Akihito; Kasahara, Sumie

2017-01-01

Purpose To assess the long-term clinical outcomes of conventional laser in situ keratomileusis (LASIK) for moderate to high myopia. Methods We retrospectively examined sixty-eight eyes of 37 consecutive patients who underwent conventional LASIK for the correction of myopia (−3.00 to −12.75 diopters (D)). At 3 months and 1, 4, 8, and 12 years postoperatively, we assessed the safety, efficacy, predictability, stability, mean keratometry, central corneal thickness, and adverse events. Results The safety and efficacy indices were 0.82 ± 0.29 and 0.67 ± 0.37, respectively, 12 years postoperatively. At 12 years, 53% and 75% of the eyes were within 0.5 and 1.0 D, respectively, of the targeted correction. Manifest refraction changes of −0.74 ± 0.99 D occurred from 3 months to 12 years after LASIK (p < 0.001). We found a significant correlation of refractive regression with the changes in keratometric readings from 3 months to 12 years postoperatively (Pearson correlation coefficient, r = −0.28, p = 0.02), but not with the changes in central corneal thickness (r = −0.08, p = 0.63). No vision-threatening complications occurred in any case. Conclusions Conventional LASIK offered good safety outcomes during the 12-year observation period. However, the efficacy and the predictability gradually decreased with time owing to myopic regression in relation to corneal steepening. PMID:28596969

Evaluation of iris recognition system for wavefront-guided laser in situ keratomileusis for myopic astigmatism.

PubMed

Ghosh, Sudipta; Couper, Terry A; Lamoureux, Ecosse; Jhanji, Vishal; Taylor, Hugh R; Vajpayee, Rasik B

2008-02-01

To evaluate the visual and refractive outcomes of wavefront-guided laser in situ keratomileusis (LASIK) using an iris recognition system for the correction of myopic astigmatism. Centre for Eye Research Australia, Melbourne Excimer Laser Research Group, and Royal Victorian Eye and Ear Hospital, East Melbourne, Victoria, Australia. A comparative analysis of wavefront-guided LASIK was performed with an iris recognition system (iris recognition group) and without iris recognition (control group). The main parameters were uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity, amount of residual cylinder, manifest spherical equivalent (SE), and the index of success using the Alpins method of astigmatism analysis 1 and 3 months postoperatively. A P value less than 0.05 was considered statistically significant. Preoperatively, the mean SE was -4.32 diopters (D) +/- 1.59 (SD) in the iris recognition group (100 eyes) and -4.55 +/- 1.87 D in the control group (98 eyes) (P = .84). At 3 months, the mean SE was -0.05 +/- 0.21 D and -0.20 +/- 0.40 D, respectively (P = .001), and an SE within +/-0.50 D of emmetropia was achieved in 92.0% and 85.7% of eyes, respectively (P = .07). At 3 months, the UCVA was 20/20 or better in 90.0% and 76.5% of eyes, respectively. A statistically significant difference in the amount of astigmatic correction was seen between the 2 groups (P = .00 and P = .01 at 1 and 3 months, respectively). The index of success was 98.0% in the iris recognition group and 81.6% in the control group (P = .03). Iris recognition software may achieve better visual and refractive outcomes in wavefront-guided LASIK for myopic astigmatism.

Gauging interest of the general public in laser-assisted in situ keratomileusis eye surgery.

PubMed

Stein, Joshua D; Childers, David M; Nan, Bin; Mian, Shahzad I

2013-07-01

To assess interest among members of the general public in laser-assisted in situ keratomileusis (LASIK) surgery and how levels of interest in this procedure have changed over time in the United States and other countries. Using the Google Trends Web site, we determined the weekly frequency of queries involving the term "LASIK" from January 1, 2007, through January 1, 2011, in the United States, United Kingdom, Canada, and India. We fit separate regression models for each of the countries to assess whether residents of these countries differed in their querying rates on specific dates and over time. Similar analyses were performed to compare 4 US states. Additional regression models compared general public interest in LASIK surgery before and after the release of a 2008 Food and Drug Administration report describing complaints associated with this procedure. During 2007 to 2011, the Google query rate for "LASIK" was highest among persons residing in India, followed by the United Kingdom, Canada, and the United States. During this time period, the query rate declined by 40% in the United States, 24% in India, and 22% in the United Kingdom, and it increased by 8% in Canada. In all 4 of the US states examined, the query rate declined-by 52% in Florida, 56% in New York, 54% in Texas, and 42% in California. Interest in LASIK declined further among US citizens after the Food and Drug Administration report release. Interest among the general public in LASIK surgery has been waning in recent years.

Effect of diquafosol tetrasodium eye drop for persistent dry eye after laser in situ keratomileusis.

PubMed

Mori, Yosai; Nejima, Ryohei; Masuda, Ayami; Maruyama, Yoko; Minami, Keiichiro; Miyata, Kazunori; Amano, Shiro

2014-07-01

To evaluate the effect of diquafosol tetrasodium (DQS) for the treatment of persistent dry eye after laser in situ keratomileusis (LASIK). Miyata Eye Hospital, Miyazaki, Japan. Noncomparative case series. This prospective study included 30 eyes of 15 patients in whom dry eye had persisted for over 12 months after LASIK, and the symptoms had not improved with artificial tears and sodium hyaluronate treatment. In addition, treatment with DQS 3% eye drops, 6 times a day, was performed for 12 weeks. Best-corrected visual acuity, tear secretion with the Schirmer test, tear break-up time, and fluorescein and lissamine green staining scores on the cornea and conjunctiva were examined before and at 1, 4, and 12 weeks after the addition. A subjective questionnaire of 14 symptoms was also assessed before and 12 weeks after treatment. The fluorescein and lissamine green staining scores significantly improved over 12 weeks; however, the best-corrected visual acuity and tear secretion did not change. The symptoms of fatigue, dryness, grittiness, discomfort, difficulty in reading, and discomfort within the area of dryness improved after the additional DQS treatment. The DQS treatment improved the subjective and objective symptoms of persistent dry eye after LASIK. Increased mucin production because of the addition of DQS probably improved the tear film stability and reduced the symptoms of dry eye in patients who had persistent dry eye after LASIK.

Nerve growth factor concentration and implications in photorefractive keratectomy vs laser in situ keratomileusis.

PubMed

Lee, Hyung Keun; Lee, Kyung Sub; Kim, Hyeon Chang; Lee, Sung Ho; Kim, Eung Kweon

2005-06-01

To determine whether tear nerve growth factor (NGF) concentration correlates with corneal sensation and ocular surface dryness after photorefractive keratectomy (PRK) and laser in situ keratomileusis (LASIK). Prospective, nonrandomized comparative clinical trial. Seventy eyes of 35 patients and 76 eyes of 38 patients underwent PRK and LASIK procedures to correct myopia and myopic astigmatism, respectively. Total tear protein level, tear NGF concentration, tear film breakup time (BUT) and Schirmer values were measured before and 1 day, 1 week, 1 month, 3 months, and 6 months after surgery. The postoperative mean tear NGF/total tear protein (NGF/tP) ratio increased in both PRK and LASIK patients compared with preoperative levels (P < .0001). At 1 week and 1 month postoperatively, the NGF/tP ratio was higher in PRK than in LASIK subjects (P < .0001). Before 6 months postoperatively, the mean corneal sensation after LASIK in the ablated zone was lower than the preoperative sensation (P < .0001), but this was not the case in PRK subjects. Mean BUT and Schirmer values were significantly lower in LASIK-treated eyes compared with PRK-treated eyes up to 6 months postoperatively (P < .0001). The early postoperative tear NGF/tP ratio correlated with the postoperative 6-month value of corneal sensation, BUT, and Schirmer values. The difference in the postoperative corneal sensation and ocular surface dryness between PRK-treated and LASIK-treated eyes might be related to the difference in the early postoperative levels of NGF, which is a potent nerve growth stimulator.

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

PubMed

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

2016-04-01

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

[Analysis of AC/A ratio after myopic excimer laser in situ keratomileusis].

PubMed

Wu, Xiao-ying; Liu, Shuang-zhen

2003-03-01

To study the changes of AC/A ratio of myopia after excimer laser in situ keratomileusis (LASIK). 135 myopia patients were treated by LASIK, their AC/A ratios were measured with synoptohore before surgery and 3 months after surgery. The average AC/A ratios of naked eyes or eyes wearing glasses before surgery and the naked after surgery were (0.724 +/- 0.587) (Delta)/D, (2.754 +/- 1.565) (Delta)/D, (1.618 +/- 1.027) (Delta)/D in turn. There were significant difference among those groups (P < 0.001). That also appeared in different degree of myopia naked before surgery (P < 0.01). We found no significant difference between the groups wearing glasses before surgery and naked after surgery (P > 0.05). A positive correlation was built up between postoperative AC/A ratio and AC/A ratio of wearing glasses or refractive diopter before surgery (r = 0.550, P < 0.001; r = 0.185, P < 0.005). And the postoperative AC/A ratios had a negative correlation to age or length of ocular axis (r = -0.340, P < 0.001; r = -0.192, P < 0.002). The regression equation for postoperative AC/A ratios was figured out as Y((Delta)/D) = 4.080 0 - 0.031 8X(1) - 0.097 1X(2) + 0.325 0X(3) (P < 0.001). X(1) = age (year), X(2) = length of ocular axis (mm), X(3) = preoperative AC/A ratio with weaning glasses ((Delta)/D). The naked AC/A ratios are higher than the preoperative's after LASIK, but lower than the wearing glasses's before surgery. It is influenced by the factors, such as: the preoperative AC/A ratio of wearing glasses, the length of ocular axis and the age.

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

PubMed

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

2015-08-01

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

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

PubMed

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

2010-03-01

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

A Comparison of Visual Outcomes and Patient Satisfaction Between Photorefractive Keratectomy and Femtosecond Laser-Assisted In Situ Keratomileusis

PubMed Central

Hashmani, Nauman; Hashmani, Sharif; Ramesh, Priyanka; Ahmed, Junaid; Kumar, Jaish; Kumar, Arun; Jamali, Munira

2017-01-01

Purpose To compare visual outcomes and satisfaction among patients of photorefractive keratectomy (PRK; Wavelight EX 500, Alcon, Ft Worth, TX, USA) and femtosecond laser-assisted in situ keratomileusis (FAL; Wavelight FS 200 laser and Wavelight EX 500, Alcon, Ft Worth, TX, USA). Methods We performed a retrospective study of 409 eyes in 207 patients that underwent either PRK (n=90) or FAL (n=117) at the two centers of Hashmanis Hospital, Karachi, Pakistan. The included refractive outcomes were sphere diopters (D), cylinder D, and spherical equivalent D. Additionally, visual acuities were included. All of these were assessed preoperatively and at the one-month postoperative check-up. Patient satisfaction was gauged at the time of chart review by contacting the patient. Results When looking at the postoperative outcomes, we found all values to be statistically significant (p<0.001) with superior outcomes in the FAL cohort. Additionally, 90% and 15% of eyes achieved a postoperative uncorrected visual acuity (UCVA) of 20/20 in FAL and PRK, respectively. Furthermore, the efficacy indexes of the FAL and PRK arms were 1.00 and 0.82, respectively. The predictability of the procedures were 92.1% and 64.9%, respectively. Lastly, 93.3% of patients were satisfied with FAL and 95.7% with PRK. Conclusion Our study shows superior visual outcomes in patients undergoing FAL. However, we found a higher satisfaction rate in those that underwent PRK, perhaps due to the higher cost of FAL. PMID:29119072

Outcomes of Retreatment after Aborted Laser In Situ Keratomileusis due to Flap Complications

PubMed Central

Al-Mezaine, Hani S.; Al-Amro, Saleh A.; Al-Fadda, Abdulaziz; Al-Obeidan, Saleh

2011-01-01

Purpose: To determine the refractive outcomes and complications of retreatment after aborted primary laser in situ keratomileusis (LASIK) due to flap complications. Materials and Methods: This retrospective study evaluated 50 retreated eyes that had flap complications during primary LASIK at the Eye Consultants Center in Riyadh, Saudi Arabia. Data were analyzed for patients with at least 3 months follow-up post retreatment. Results: Thirty-three eyes of 31 consecutive patients with 3 months follow-up or later post retreatment were included. The primary LASIK was aborted due to incomplete flaps in 22 eyes (66.7%), buttonhole flaps in 7 eyes (21.2%), free partial flaps in 3 eyes (9.1%), and a free complete flap in 1 eye (3.0%). Twenty-two eyes (66.7%) were retreated with LASIK, and 11 eyes (33.3%) were retreated with surface ablation. The mean spherical equivalent (SE) was –0.23 ± 0.72 D, the mean astigmatism was –0.65 ± 0.89 D, and the mean loss of the best corrected visual acuity (BCVA) was 0.78 lines at the final postoperative visit. At the last postoperative visit, 20/30 or better BCVA was achieved in 90.1% of eyes that underwent retreatment with LASIK and in 91% of eyes that were retreated with surface ablation. There was no statistical difference in postoperative SE between eyes retreated with LASIK and eyes retreated with surface ablation (P = 0.610). There was no statistical difference in postoperative BCVA between eyes retreated with LASIK and those retreated with surface ablation (P = 0.756). There were no intraoperative complications and no eyes required a second retreatment. Conclusion: Creation of a flap after a previous intraoperative flap complication was not associated with any complications. The refractive outcomes of retreatment with LASIK or surface ablation were comparable and reasonably favorable. PMID:21887080

Outcomes of Retreatment after Aborted Laser In Situ Keratomileusis due to Flap Complications.

PubMed

Al-Mezaine, Hani S; Al-Amro, Saleh A; Al-Fadda, Abdulaziz; Al-Obeidan, Saleh

2011-07-01

To determine the refractive outcomes and complications of retreatment after aborted primary laser in situ keratomileusis (LASIK) due to flap complications. This retrospective study evaluated 50 retreated eyes that had flap complications during primary LASIK at the Eye Consultants Center in Riyadh, Saudi Arabia. Data were analyzed for patients with at least 3 months follow-up post retreatment. Thirty-three eyes of 31 consecutive patients with 3 months follow-up or later post retreatment were included. The primary LASIK was aborted due to incomplete flaps in 22 eyes (66.7%), buttonhole flaps in 7 eyes (21.2%), free partial flaps in 3 eyes (9.1%), and a free complete flap in 1 eye (3.0%). Twenty-two eyes (66.7%) were retreated with LASIK, and 11 eyes (33.3%) were retreated with surface ablation. The mean spherical equivalent (SE) was -0.23 ± 0.72 D, the mean astigmatism was -0.65 ± 0.89 D, and the mean loss of the best corrected visual acuity (BCVA) was 0.78 lines at the final postoperative visit. At the last postoperative visit, 20/30 or better BCVA was achieved in 90.1% of eyes that underwent retreatment with LASIK and in 91% of eyes that were retreated with surface ablation. There was no statistical difference in postoperative SE between eyes retreated with LASIK and eyes retreated with surface ablation (P = 0.610). There was no statistical difference in postoperative BCVA between eyes retreated with LASIK and those retreated with surface ablation (P = 0.756). There were no intraoperative complications and no eyes required a second retreatment. Creation of a flap after a previous intraoperative flap complication was not associated with any complications. The refractive outcomes of retreatment with LASIK or surface ablation were comparable and reasonably favorable.

Dry eyes and corneal sensation after laser in situ keratomileusis with femtosecond laser flap creation Effect of hinge position, hinge angle, and flap thickness.

PubMed

Mian, Shahzad I; Li, Amy Y; Dutta, Satavisha; Musch, David C; Shtein, Roni M

2009-12-01

To determine whether corneal sensation and dry-eye signs and symptoms after myopic laser in situ keratomileusis (LASIK) surgery with a femtosecond laser are affected by varying hinge position, hinge angle, or flap thickness. University-based academic practice, Ann Arbor, Michigan, USA. This prospective randomized contralateral-eye study evaluated eyes after bilateral myopic LASIK with a femtosecond laser (IntraLase). Superior and temporal hinge positions, 45-degree and 90-degree hinge angles, and 100 microm and 130 microm corneal flap thicknesses were compared. Postoperative follow-up at 1 week and 1, 3, 6, and 12 months included central Cochet-Bonnet esthesiometry, the Ocular Surface Disease Index questionnaire, a Schirmer test with anesthesia, tear breakup time (TBUT), corneal fluorescein staining, and conjunctival lissamine green staining. The study evaluated 190 consecutive eyes (95 patients). Corneal sensation was reduced at all postoperative visits, with improvement over 12 months (P<.001). There was no difference in corneal sensation between the different hinge positions, angles, or flap thicknesses at any time point. The overall ocular surface disease index score was increased at 1 week, 1 month, and 3 months (P<.0001, P<.0001, and P = .046, respectively). The percentage of patients with a TBUT longer than 10 seconds was significantly lower at 1 week and 1 month (P<.0001). Dry-eye syndrome after myopic LASIK with a femtosecond laser was mild and improved after 3 months. Corneal flap hinge position, hinge angle, and thickness had no effect on corneal sensation or dry-eye syndrome.

Management of the ocular surface and tear film before, during, and after laser in situ keratomileusis.

PubMed

Albietz, Julie M; Lenton, Lee M

2004-01-01

To identify evidence-based, best practice strategies for managing the ocular surface and tear film before, during, and after laser in situ keratomileusis (LASIK). After a comprehensive review of relevant published literature, evidence-based recommendations for best practice management strategies are presented. Symptoms of ocular irritation and signs of dysfunction of the integrated lacrimal gland/ocular surface functional gland unit are common before and after LASIK. The status of the ocular surface and tear film before LASIK can impact surgical outcomes in terms of potential complications during and after surgery, refractive outcome, optical quality, patient satisfaction, and the severity and duration of dry eye after LASIK. Before LASIK, the health of the ocular surface should be optimized and patients selected appropriately. Dry eye before surgery and female gender are risk factors for developing chronic dry eye after LASIK. Management of the ocular surface during LASIK can minimize ocular surface damage and the risk of adverse outcomes. Long-term management of the tear film and ocular surface after LASIK can reduce the severity and duration of dry eye symptoms and signs. Strategies to manage the integrated ocular surface/lacrimal gland functional unit before, during, and after LASIK can optimize outcomes. As problems with the ocular surface and tear film are relatively common, attention should focus on the use and improvement of evidence-based management strategies.

Accuracy of Corneal Power Measurements for Intraocular Lens Power Calculation after Myopic Laser In situ Keratomileusis.

PubMed

Helaly, Hany A; El-Hifnawy, Mohammad A M; Shaheen, Mohamed Shafik; Abou El-Kheir, Amr F

2016-01-01

To evaluate the accuracy of corneal power measurements for intraocular lens (IOL) power calculation after myopic laser in situ keratomileusis (LASIK). The study evaluated 45 eyes with a history of myopic LASIK. Corneal power was measured using manual keratometry, automated keratometry, optical biometry, and Scheimflug tomography. Different hypothetical IOL power calculation formulas were performed for each case. The steepest mean K value was measured with manual keratometry (37.48 ± 2.86 D) followed by automated keratometry (37.31 ± 2.83 D) then optical biometry (37.06 ± 2.98 D) followed by Scheimflug tomography (36.55 ± 3.08). None of the K values generated by Scheimflug tomography were steeper than the measurements from the other 3 instruments. Using equivalent K reading (EKR) 4 mm with the Double-K SRK/T formula, the refractive outcome generated 97.8% of cases within ± 2 D, 80.0% of cases within ± 1 D, and 42.2% of cases within ± 0.5 D. The best combination of formulas was "Shammas-PL + Double-K SRK/T formula using EKR 4 mm." Scheimflug tomography imaging using the Holladay EKR 4 mm improved the accuracy of IOL power calculation in post-LASIK eyes. The best option is a combination of formulas. We recommended the use the combined "Shammas-PL ± Double-K SRK/T formula using EKR 4 mm"h for optical outcomes.

Effects of laser in situ keratomileusis on mental health-related quality of life.

PubMed

Tounaka-Fujii, Kaoru; Yuki, Kenya; Negishi, Kazuno; Toda, Ikuko; Abe, Takayuki; Kouyama, Keisuke; Tsubota, Kazuo

2016-01-01

The aims of our study were to investigate whether laser in situ keratomileusis (LASIK) improves health-related quality of life (HRQoL) and to identify factors that affect postoperative HRQoL. A total of 213 Japanese patients who underwent primary LASIK were analyzed in this study. The average age of patients was 35.0±9.4 years. The subjects were asked to answer questions regarding subjective quality of vision, satisfaction, and quality of life (using the Japanese version of 36-Item Short Form Health Survey Version 2) at three time points: before LASIK, 1 month after LASIK, and 6 months after LASIK. Longitudinal changes over 6 months in the outputs of mental component summary (MCS) score and the physical component summary (PCS) score from the 36-Item Short Form Health Survey Version 2 questionnaire were compared between time points using a linear mixed-effects model. Delta MCS and PCS were calculated by subtracting the postoperative score (1 month after LASIK) from the preoperative score. Preoperative and postoperative factors associated with a change in the MCS score or PCS score were evaluated via a linear regression model. The preoperative MCS score was 51.0±9.4 and increased to 52.0±9.8 and 51.5±9.6 at 1 month and 6 months after LASIK, respectively, and the trend for the change from baseline in MCS through 6 months was significant ( P =0.03). PCS score did not change following LASIK. Delta MCS was significantly negatively associated with preoperative spherical equivalent, axial length, and postoperative quality of vision, after adjusting for potential confounding factors. Mental HRQoL is not lost with LASIK, and LASIK may improve mental HRQoL. Preoperative axial length may predict postoperative mental HRQoL.

Effects of laser in situ keratomileusis on mental health-related quality of life

PubMed Central

Tounaka-Fujii, Kaoru; Yuki, Kenya; Negishi, Kazuno; Toda, Ikuko; Abe, Takayuki; Kouyama, Keisuke; Tsubota, Kazuo

2016-01-01

Purpose The aims of our study were to investigate whether laser in situ keratomileusis (LASIK) improves health-related quality of life (HRQoL) and to identify factors that affect postoperative HRQoL. Materials and methods A total of 213 Japanese patients who underwent primary LASIK were analyzed in this study. The average age of patients was 35.0±9.4 years. The subjects were asked to answer questions regarding subjective quality of vision, satisfaction, and quality of life (using the Japanese version of 36-Item Short Form Health Survey Version 2) at three time points: before LASIK, 1 month after LASIK, and 6 months after LASIK. Longitudinal changes over 6 months in the outputs of mental component summary (MCS) score and the physical component summary (PCS) score from the 36-Item Short Form Health Survey Version 2 questionnaire were compared between time points using a linear mixed-effects model. Delta MCS and PCS were calculated by subtracting the postoperative score (1 month after LASIK) from the preoperative score. Preoperative and postoperative factors associated with a change in the MCS score or PCS score were evaluated via a linear regression model. Results The preoperative MCS score was 51.0±9.4 and increased to 52.0±9.8 and 51.5±9.6 at 1 month and 6 months after LASIK, respectively, and the trend for the change from baseline in MCS through 6 months was significant (P=0.03). PCS score did not change following LASIK. Delta MCS was significantly negatively associated with preoperative spherical equivalent, axial length, and postoperative quality of vision, after adjusting for potential confounding factors. Conclusion Mental HRQoL is not lost with LASIK, and LASIK may improve mental HRQoL. Preoperative axial length may predict postoperative mental HRQoL. PMID:27713617

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

PubMed Central

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

2016-01-01

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

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

PubMed

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

2018-03-28

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

Temporal and Spatial Flap Variability in Laser In-Situ Keratomileusis by Optical Coherence Tomography.

PubMed

Dawood, Yousif Farhan; Al Hassany, Usama; Issa, Ammar F

2017-01-01

To study changes in flap thickness made with two different microkeratome heads across different corneal locations using anterior segment optical coherence tomography (OCT). In this prospective, non-randomized, consecutive case series, subjects who had their laser in-situ keratomileusis (LASIK) flaps made using 90 μm (MSU90) or 130 μm (MSU130) disposable M2 microkeratome heads were examined using OCT. The measurements were performed at three locations (central and 2.5 mm to either side) at 1 day, 1 week, and 1 month postoperatively. The central flap thickness was 123 ± 15, 130 ± 14, and 127 ± 13 μm, respectively, at 1 day, 1 week, and 1 month postoperatively in the MSU90 group (41 eyes) and 142 ± 20, 147 ± 19, and 143 ± 15 μm, respectively, in the MSU130 group (47 eyes). At 1 month, peripheral flap thickness was 161 ± 17 and 159 ± 13 μm, respectively, at 2.5 mm to the right and left of corneal center in the MSU90 group. The corresponding figures were 170 ± 14 and 167 ± 13 μm, respectively, in the MSU130 group. There was a statistically significant difference between the two groups at all locations ( P < 0.001). No statistically significant change in flap thickness was detected in either group at any assessment time. There was a partial positive correlation (after controlling for preoperative manifest refractive spherical equivalent) between central flap thickness and preoperative ultrasound central pachymetry ( r = 0.739, P = 0.036) in the MSU90 group but not in the MSU130 group. Using OCT, changes in flap thickness were minimal in the first month after LASIK. Flap thickness correlated strongly with central corneal thickness if a 90 μm head was used.

Effects of ablation depth and repair time on the corneal elastic modulus after laser in situ keratomileusis.

PubMed

Wang, Xiaojun; Li, Xiaona; Chen, Weiyi; He, Rui; Gao, Zhipeng; Feng, Pengfei

2017-01-17

The biomechanical properties of the cornea should be taken into account in the refractive procedure in order to perform refractive surgery more accurately. The effects of the ablation depth and repair time on the elastic modulus of the rabbit cornea after laser in situ keratomileusis (LASIK) are still unclear. In this study, LASIK was performed on New Zealand rabbits with different ablation depth (only typical LASIK flaps were created; residual stroma bed was 50 or 30% of the whole cornea thickness respectively). The animals without any treatment were served as normal controls. The corneal thickness was measured by ultrasonic pachymetry before animals were humanly killed after 7 or 28 days post-operatively. The corneal elastic modulus was measured by uniaxial tensile testing. A mathematical procedure considering the actual geometrics of the cornea was created to analyze the corneal elastic modulus. There were no obvious differences among all groups in the elastic modulus on after 7 days post-operatively. However, after 28th days post-operatively, there was a significant increase in the elastic modulus with 50 and 30% residual stroma bed; only the elastic modulus of the cornea with 30% residual stroma bed was significantly higher than that of 7 days. Changes in elastic modulus after LASIK suggest that this biomechanical effect may correlate with the ablation depth and repair time.

[Corneal subbasal nerve density changes after laser in situ keratomileusis with mechanical microkeratome and femtosecond laser].

PubMed

Hu, Liang; Xie, Wenjia; Tang, Lei; Chen, Jia; Zhang, Dong; Yu, Peng; Qu, Jia

2015-01-01

To compare the corneal subbasal nerve density (SND) changes after laser in situ keratomileusis (LASIK) with a microkeratome and a femtosecond laser. Prospective clinical study. Sixty eyes of thirty myopes were included. Fifteen patients (30 eyes) underwent LASIK with the Moria II microkeratome, and the other 15 patients (30 eyes) with the 60 k Hz IntraLase femtosecond laser. Central, temporal and nasal corneal SNDs were measured by confocal microscopy and compared before surgery, 1 month, and 3 months after surgery. Analysis of variance and t test were used for comparing the differences between different time points and two groups. Preoperatively and 1 month, 3 months postoperatively, the SNDs were (16 728.30 ± 4 300.30), (1 875.42 ± 300.50) and (1 701.55 ± 194.11) µm/mm(2) in the central cornea, (11 379.70 ± 1 833.92), (1 341.20 ± 288.68) and (1 860.87 ± 147.60) µm/mm(2) in the temporal cornea, and (8 506.79 ± 662.83), (7 428.96 ± 712.99) and (8 044.32 ± 1 077.54) µm/mm(2) in the nasal cornea, respectively, in the microkeratome group, and (16 351.59 ± 3 503.88), (1 859.38 ± 452.93) and (2 043.67 ± 377.76) in the central cornea, (12 328.22 ± 2 007.43), (1 483.85 ± 371.28) and (2 126.31 ± 279.87) µm/mm(2) in the temporal cornea, and (8 347.91 ± 789.44), (1 475.53 ± 293.98) and (2 022.10 ± 282.89) µm/mm(2) in the nasal cornea, respectively, in the femtosecond laser group. The SNDs at three positions all decreased significantly at each time point postoperatively compared to the baseline values in both groups (1 and 3 months in the microkeratome group: central t = 18.981 and 18.912, temporal t = 30.121 and 27.921, and nasal t = 6.456 and 2.126; in the femtosecond laser group: central t = 22.667 and 22.379, temporal t = 29.000 and 28.376, and nasal t = 46.329 and 41.751; all P < 0.01, except 3 months at the nasal in the microkeratome group, P = 0.042). The nasal SND increased significantly from month 1 to month 3 (t = -3.921, P < 0.01) in the

Evaluation of the effectiveness of laser in situ keratomileusis and photorefractive keratectomy for myopia: a meta-analysis.

PubMed

Yang, Xin-Jun; Yan, Hong-Tao; Nakahori, Yutaka

2003-08-01

To evaluate the effectiveness of laser in situ keratomileusis (LASIK) and photorefractive keratectomy (PRK) for correcting myopia. Study selection, data extraction, and quality assessment were performed by two of authors independently. Summary odds ratios and 95% confidence intervals were calculated by DerSimonian & Laird random-effects model and Mantel-Haenszel (fixed-effects) model. All calculations were based on an intention-to-treat and per protocol analysis. Five hundred and eighty eyes (476 patients) from 5 randomized controlled trials were included in this study. At > or = 6 months follow-up, by random-effects model, the pooled odds ratios (OR, for LASIK vs. PRK) of postoperative uncorrected visual acuity (UCVA) of 20/20 or better for all trials were 1.31 (95% CI=0.77-2.22) by per protocol analysis and 1.18 (95% CI=0.74-1.88) by intention-to-treat analysis. In the refractive outcome, the pooled OR of the postoperative spherical equivalent refraction within +/-0.5 diopter (D) of emmetropia did not show any statistical significance, for which the OR were 0.75 (95% CI=0.48-1.18) by per protocol analysis and 0.70 (95% CI=0.47-1.04) by intention-to-treat analysis. LASIK and PRK were found to be similarly effective for the correction of myopia from -1.5 to -15.0 D in a greater than 6 month follow-up.

Vision-related quality of life and visual outcomes after small-incision lenticule extraction and laser in situ keratomileusis.

PubMed

Ang, Marcus; Ho, Henrietta; Fenwick, Eva; Lamoureux, Ecosse; Htoon, Hla M; Koh, Jane; Tan, Donald; Mehta, Jodhbir S

2015-10-01

To compare vision-related quality of life (VRQoL) scores and clinical outcomes between small-incision lenticule extraction and laser in situ keratomileusis (LASIK). Singapore National Eye Centre, Singapore. Prospective study. Patients had small-incision lenticule extraction using the Visumax 500 kHz femtosecond laser; or LASIK excimer ablation with the Wavelight Allegretto 400 Hz laser. Primary outcomes were 3-month predictability, efficacy, and safety. Secondary outcomes were intraoperative experience, visual symptoms, and VRQoL (validated Quality of Life Impact of Refractive Correction [QIRC] questionnaire) in 25 a subgroup of patients in each group. Following Rasch analysis, "Functional" and "Emotional," QIRC dimensions were analysed separately. At 3 months, predictability (82.5% versus 85.3%, ±0.5 diopters attempted correction, P =.453), safety index (1.13 ± 0.19 [SD] versus 1.07 ± 0.16, P = .158), and efficacy index (0.91 ± 0.21 versus 0.97 ± 0.19; P = .002) were found when comparing small-incision lenticule extraction (172 eyes) and LASIK (matched 688 eyes). Intraoperative experience between groups was not statistically different; visual fluctuations (P = .020) and episodes of visual blurring (P = .008) were greater after small-incision lenticule extraction than after LASIK at 1 month but not at 3 months. There was no difference in "functional" (66.7 ± 15.7 versus 55.3 ± 22.2, P = .064) and "emotional" (42.7 ± 23.2 versus 37.9 ± 23.8, P = .394) QIRC dimensions between the 2 groups (25 patients in each group) at 3 months. The study, 3-month predictability, safety, and VRQL scores were not statistically different between small-incision lenticule extraction and LASIK. No author has a financial or proprietary interest in any material or method mentioned. Copyright © 2015 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.

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

PubMed

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

2015-05-01

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

Efficacy of punctal occlusion in management of dry eyes after laser in situ keratomileusis for myopia.

PubMed

Alfawaz, Abdullah M; Algehedan, Saeed; Jastaneiah, Sabah S; Al-Mansouri, Samir; Mousa, Ahmed; Al-Assiri, Abdullah

2014-03-01

To evaluate the effect of punctal plug use in preventing dry eye after laser in situ keratomileusis (LASIK). A randomized clinical trial at a tertiary eye care center, Riyadh, Saudi Arabia. Participants underwent LASIK for myopia in both eyes and a lower punctal occlusion in one eye only while the other eye served as control. Both eyes received the same postoperative medications except for lubricant duration (subject eye: four times per day for one week; control eye: four times per day for 6 months). Participants were evaluated at 1 week, 2, and 6 months after surgery for signs and symptoms of dry eye. The main outcome measures were visual acuity; ocular surface parameters; and Ocular Surface Disease Index questionnaire. Seventy-eight eyes of 39 patients were included in this study. The Ocular Surface Disease Index scores of eyes with punctal plugs were better at all follow-up visits, and the differences between both eyes were statistically significant (1 week, p < 0.0001; 2 months, p < 0.0001; 6 months, p = 0.008). At the final follow-up visit, the percentage of normal eyes was higher in eyes with punctal plugs for all ocular surface parameters (Schirmer 1 test, 94.9%; tear breakup time, 77.8%; punctate epithelial keratitis score, 71.8%) compared to eyes without occlusion (Schirmer 1 test, 92.3%; tear breakup time, 58.3%; punctate epithelial keratitis score, 53.8%); however, such differences were not statistically significant. Punctal plug insertion after LASIK surgeries may minimize the need for frequent lubricant application and hence improve patient satisfaction.

Chronic dry eye in photorefractive keratectomy and laser in situ keratomileusis: Manifestations, incidence, and predictive factors.

PubMed

Bower, Kraig S; Sia, Rose K; Ryan, Denise S; Mines, Michael J; Dartt, Darlene A

2015-12-01

To evaluate dry-eye manifestations after photorefractive keratectomy (PRK) and laser in situ keratomileusis (LASIK) and determine the incidence and predictive factors of chronic dry eye using a set of dry-eye criteria. Walter Reed Army Medical Center, Washington, DC, USA. Prospective, non-randomized clinical study. Dry-eye evaluation was performed before and after surgery. Main outcome measures included dry-eye manifestations, incidence, and predictive factors of chronic dry eye. This study comprised 143 active-duty U.S. Army personnel, ages 29.9 ± 5.2 years, with myopia or myopic astigmatism (manifest spherical equivalent -3.83 ± 1.96 diopters) having PRK or LASIK. Schirmer scores, corneal sensitivity, ocular surface staining, surface regularity index, and responses to dry-eye questionnaire significantly changed over time after PRK. After LASIK, significant changes were observed in tear breakup time, corneal sensitivity, ocular surface staining, and responses to questionnaire. Twelve months postoperatively, 5.0% of PRK and 0.8% of LASIK participants developed chronic dry eye. Regression analysis showed that pre-operatively lower Schirmer score will significantly influence development of chronic dry eye after PRK, whereas preoperatively, lower Schirmer score or higher ocular surface staining score will significantly influence the occurrence of chronic dry eye after LASIK. Chronic dry eye was uncommon after PRK and LASIK. Ocular surface and tear-film characteristics during pre-operative examination might help to predict chronic dry-eye development in PRK and LASIK. The authors have no financial interest in any product, drug, instrument, or equipment discussed in this manuscript. Copyright © 2015 ASCRS and ESCRS. All rights reserved.

Oral Omega-3 Fatty Acid Supplementation for Laser In Situ Keratomileusis-Associated Dry Eye.

PubMed

Goyal, Parul; Jain, Arun K; Malhotra, Chintan

2017-02-01

To determine the effect of oral omega-3 fatty acid (ω3FA) supplementation in laser in situ keratomileusis (LASIK)-associated dry eye. In this prospective, open-label study, patients undergoing LASIK were randomized to receive either 1.2 g/d of a triglyceride formulation of oral ω3FA (treatment group) or 400 mg/d vitamin E (control group) for 1 week before and continued for 12 weeks after surgery. Ocular surface disease index, tear breakup time, ocular surface staining, and Schirmer scores were evaluated and compared preoperatively and at 3 months after LASIK. The study included 30 patients in each group. All parameters were comparable at baseline. Ocular surface disease index scores increased comparably in both groups (1.9 ± 0.6 increase in the treatment group; 2.8 ± 0.5 in the control group) (P = 0.267). Compared with baseline levels, tear breakup time decreased significantly (P < 0.01) but comparably in both treatment (-2.3 ± 0.4 seconds decrease) and control (-3.5 ± 0.7 seconds decrease) groups (P = 0.105). More eyes in the control group (43.4%) had conjunctival staining with Lissamine green at 3 months compared with the treatment group (14%) (P = 0.009). The Schirmer score at 3 months was higher (P = 0.003) in the treatment group (30.5 ± 0.90 mm) than in the control group (25.7 ± 1.3 mm) with a increase of 5.9 ± 1.3 mm from baseline in the treatment group and a decrease of 1.5 ± 1.2 mm in the control group. Supplementation with ω3FA in patients undergoing LASIK had a positive influence on tear secretion, whereas tear film stability remained unaffected when compared with the control group.

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

PubMed

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

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

[Analysis of corneal biomechanical changes after femtosecond laser-assisted laser in situ keratomileusis in children with hyperopic anisometropia].

PubMed

Kulikova, I L; Shlenskaya, O V; Chapurin, N V

to analyze corneal hysteresis (CH) and corneal resistance factor (RF) readings obtained with the Reichert Ocular Response Analyzer (ORA) before and after hyperopic femtolaser-assisted laser in situ keratomileusis (FS-LASIK) in children with anisometropia as well as to establish factors that may cause changes in these parameters. CH and RF were evaluated before and 1.5 years after FS-LASIK performed on amblyopic eyes of 28 patients aged 6-14 years. Preoperatively, there was a correlation between CH and RF (r=0.41, p=0.03). No correlation was found between CH and age (r=-0.02, p=0.82) or between CH (r=0.00, p=0.98), RF (r=0.04, p=0.83), and cornea thickness. The mean preoperative CH was 12.56±1.21 mmHg, RF 12.31±1.57 mmHg. Postoperatively, a statistically significant change occurred to both CH (by 0.97±1.51 mmHg, p=0.002) and RF (by 1.42±1.55 mmHg, p=0.000). No correlation was found between CH before and after surgery (r=0.11, p=0.57) as well as between the ablation depth and changes in CH (r=0,04, p=0.83) and RF (r=0.21, p=0.28). Regression analysis showed that the extent of CH (r2=0.52, p=0.00) and RF (r2=0,48, p=0.00) changes was closely related to their preoperative values. The statistically significant relative change in CH and RF after hyperopic FS-LASIK was 8% and 12%, respectively. CH and RF changes correlated with their preoperative values, but not with the ablation depth or cornea thickness.

Outcomes of topography-guided versus wavefront-optimized laser in situ keratomileusis for myopia in virgin eyes.

PubMed

Jain, Arun Kumar; Malhotra, Chintan; Pasari, Anand; Kumar, Pawan; Moshirfar, Majid

2016-09-01

To compare the outcomes of topography-guided and wavefront-optimized treatment in patients having laser in situ keratomileusis (LASIK) for myopia. Advanced Eye Centre, Post Graduate Institute of Medical Education and Research, Chandigarh, India. Prospective contralateral-eye case study. Patients had topography-guided LASIK in 1 eye and wavefront-optimized LASIK in the contralateral eye using the Customized Refractive Surgery Master software and Mel 80 excimer laser. Refractive (residual manifest refraction spherical equivalent [MRSE], higher-order aberrations [HOAs]), and visual (uncorrected distance visual acuity [UDVA] and photopic and mesopic contrast sensitivity) outcomes were prospectively analyzed 6 months postoperatively. The study comprised 35 patients. The UDVA was 0.0 logMAR or better and the postoperative residual MRSE was ±0.50 diopter in 94.29% of eyes in the topography-guided group and 85.71% of eyes in the wavefront-optimized group (P = .09). More eyes in the topography-guided group than in the wavefront-optimized group had a UDVA of -0.1 logMAR or better (P = .04). Topography-guided LASIK was associated with less deterioration of mesopic contrast sensitivity at higher spatial frequencies (12 cycles per degree [cpd] and 18 cpd) and lower amounts of induced coma (P = .04) and spherical aberration (P = .04). Less stromal tissue was ablated in the topography-guided group (mean 61.57 μm ± 16.23 [SD]) than in the wavefront-optimized group (mean 79.71 ± 14.81 μm) (P < .001). Although topography-guided LASIK and wavefront-optimized LASIK gave excellent results, topography-guided LASIK was associated with better contrast sensitivity, lower induction of HOAs, and a smaller amount of tissue ablation. None of the authors has a financial or proprietary interest in any material or method mentioned. Copyright © 2016 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.

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

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

PubMed

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

2018-06-13

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

Effect of Laser in Situ Keratomileusis on Schiøtz, Goldmann, and Dynamic Contour Tonometric Measurements.

PubMed

Sales-Sanz, Marco; Arranz-Marquez, Esther; Piñero, David P; Arruabarrena, Carolina; Mikropoulos, Dimitrios G; Teus, Miguel A

2016-04-01

To assess the effect of laser in situ keratomileusis (LASIK) on ocular rigidity and compare its effect on intraocular pressure (IOP) readings with Goldmann applanation tonometry (GAT), Schiøtz indentation tonometry (ST), and dynamic contour tonometry (DCT). Prospective, observational, single-masked study. Eighty-one patients who underwent myopic LASIK and 108 unoperated myopic control patients were included in the study. The IOP was measured using GAT, DCT, and ST. The coefficient of ocular rigidity (Ko) was obtained from the regression analysis of the 3 readings obtained with each weight of the ST. Linear multiple regression analysis was performed with dummy variables to assess the effects of age, central corneal thickness (CCT), and refractive surgery on measured IOP values. Age, CCT, and previous LASIK explained 39.41% of the IOP readings with GAT, 25.31% with DCT, and 3.28% with ST. LASIK caused a mean decrease of -2.51 mm Hg in IOP readings (P=0.000) with GAT, -1.29 mm Hg (P=0.036) with DCT, and no significant change in IOP readings with ST (P=0.299). Significant differences in the Ko were observed between the LASIK and control groups. The Ko values were unrelated to age and CCT in the LASIK and control groups. ST seems to be less affected by previous LASIK procedures. There is a difference in the ocular rigidity between the unoperated and LASIK eyes that is not correlated with the CCT. Therefore, ST seems to measure changes in the biomechanical behavior of corneas that underwent LASIK surgery.

Epipolis-laser in situ keratomileusis versus photorefractive keratectomy for the correction of myopia: a meta-analysis.

PubMed

Wu, Wenjing; Wang, Yan; Xu, Lulu

2015-10-01

It is unclear whether epipolis-laser in situ keratomileusis (Epi-LASIK) has any significant advantage over photorefractive keratectomy (PRK) for correcting myopia. We undertook this meta-analysis of randomized controlled trials and cohort studies to examine possible differences in efficacy, predictability, and side effects between Epi-LASIK and PRK for correcting myopia. A system literature review was conducted in the PubMed, Cochrane Library EMBASE. The statistical analysis was performed by RevMan 5.0 software. The results included efficacy outcomes (percentage of eyes with 20/20 uncorrected visual acuity post-treatment), predictability (proportion of eyes within ±0.5 D of the target refraction), epithelial healing time, and the incidence of significant haze and pain scores after surgery. There are seven articles with total 987 eyes suitable for the meta-analysis. There is no statistical significance in the predictability between Epi-LASIK and PRK, the risk ratio (RR) is 1.03, 95% confidence interval (CI) [0.92, 1.16], p = 0.18; with respect to efficacy, the odds ratio is 1.43, 95% CI = [0.85, 2.40], p = 0.56 between Epi-LASIK and PRK, there is no statistical significance either. The epithelial cell layer healing time and the pain scores and the incidence of significant haze showed no significance between these two techniques although more pains can be found in Epi-LASIK than PRK at the early-stage post-operation. According to the above analysis, Epi-LASIK has good efficacy and predictability as PRK. In addition, both techniques have low pain scores and low incidence of significant haze.

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.

Management of epithelial ingrowth after laser in situ keratomileusis on a tertiary care cornea service.

PubMed

Rapuano, Christopher J

2010-03-01

To review the management of epithelial ingrowth after laser in situ keratomileusis (LASIK) on the Wills Eye Institute Cornea Service from 1996 through 2007. Data of all patients referred to the Wills Eye Cornea Service after having undergone LASIK were reviewed. Charts of all patients with the diagnosis of epithelial ingrowth were analyzed. Data included patient demographics, previous ocular history, visual acuity, size and location of the ingrowth, and management. Additional data on eyes that underwent removal of the ingrowth at Wills were obtained. Three hundred five patients (153 female and 152 male, mean age: 44.7 years) were referred for eye problems after LASIK during the study period. Epithelial ingrowth was confirmed in 46 patients (15%) (19 female and 27 male, mean age: 47.4 years) involving 55 eyes (27 right and 28 left). Patients with epithelial ingrowth were seen at a mean of 26 months after LASIK (range: 0.5-108 months). Twenty-four eyes had undergone previous enhancements, 2 twice. Fourteen eyes had undergone previous removal of epithelial ingrowth, 8 more than once (range: 2-8). In 35 eyes, simple observation was recommended. In 7 eyes, epithelial removal was recommended to the referring physician. Thirteen eyes underwent flap lift and epithelial removal at Wills Eye; 9 included flap suturing. One eye required repeat treatment with flap suturing and fibrin glue, after which no recurrence was found. In the other 12 eyes, there was no recurrence in 9, small recurrences in 2, and a large recurrence in 1 eye (mean follow-up: 16 months). Epithelial ingrowth after LASIK is not rare in our referral practice. Mild ingrowth can be observed, whereas significant ingrowth can respond well to removal with a low chance of significant recurrence.

[Static and dynamic contrast sensitivity of myopic eyes before and after laser in situ keratomileusis].

PubMed

Liu, Xiao-wei; Pang, Guo-xiang; Liu, Xi-pu; Jiang, Ru-xin; Jin, Yu-mei; Sun, Yu-min; Wang, Zhong-hai

2003-10-01

To evaluate the static and dynamic contrast sensitivity changes in myopic patients before and after laser in situ keratomileusis (LASIK). Seventy-three eyes in 37 patients with myopia (with or without astigmatism) who received LASIK were tested for static and dynamic contrast sensitivities using the METRO VISION MON ELEC I system at 0.7, 1.4, 2.7, 5.5, 11, and 22 cpd and cps prior to LASIK, and at one-, three-, and six-month intervals after LASIK. All eyes gained naked visual acuity of more than 0.5 after LASIK. The contrast sensitivity was depressed at all frequencies 1 month after LASIK, as compared to one week prior to LASIK. The depression at 2.7, 5.5, 11 (P < 0.01) and 22 cpd (P < 0.05) was statistically significant for static contrast sensitivity, and also at 5.5 (P < 0.01) and 11 cps (P < 0.05) for dynamic contrast sensitivity. Myopic eyes between 6.25 D and 14.0 D, and astigmatic eyes 2 DC and more, suffered more static and dynamic contrast sensitivity depression than the myopic eyes between 1.25 D and 6.00 D and astigmatic eyes less than 2 DC. Contrast sensitivities were improved and exceeded preoperative levels 3 months after LASIK, and improved even more 6 months after LASIK. All sequences were statistically significant for static contrast sensitivity (P < 0.01), while only 2.7, 5.5, and 11 cps were statistically significant for dynamic contrast sensitivity (P < 0.01). The astigmatic eyes 2 DC and more showed less improvement, even below the preoperative level at 1.4 cps of dynamic contrast sensitivity. While temporary depression of contrast sensitivity for myopic eyes after LASIK was seen, contrast sensitivity soon returned to exceed preoperative levels at 3 months after LASIK, while improving even more 6 months after LASIK.

Early corneal nerve damage and recovery following small incision lenticule extraction (SMILE) and laser in situ keratomileusis (LASIK).

PubMed

Mohamed-Noriega, Karim; Riau, Andri K; Lwin, Nyein C; Chaurasia, Shyam S; Tan, Donald T; Mehta, Jodhbir S

2014-03-25

We compared early corneal nerve changes after small incision lenticule extraction (SMILE) and laser in situ keratomileusis (LASIK). A total of 12 rabbits underwent LASIK in one eye and SMILE in the fellow eye. Baseline and follow-up evaluations at 1, 2, and 4 weeks postoperatively were performed with in vivo confocal microscopy to evaluate 5 different areas within the treated zone: center, superior, inferior, nasal, and temporal. Cryosections of the corneas and whole mount of the extracted SMILE lenticules were analyzed with immunostaining of βIII-tubulin. One week after SMILE and LASIK, a decrease in nerve length and density was observed in all evaluated areas. A trend toward greater subbasal nerve length and density (SLD), more eyes with subbasal nerves (ESN), more eyes with subbasal nerves longer than 200 μm (SNL), and higher mean number of subbasal nerves by frame (NSN) in SMILE than in LASIK groups was observed at subsequent follow-up time points. Only the SMILE group showed a recovery of SLD, ESN, and NSN by week 4 (P > 0.05). A trend toward more eyes with sprouting subbasal nerves and greater mean number of sprouting nerves was observed in LASIK than in SMILE, indicating that more subbasal nerves were disrupted and undergoing regeneration after LASIK. Immunostaining at postoperative week 4 revealed a faster stromal nerve recovery in post-SMILE eyes compared to post-LASIK eyes. Our findings suggest that SMILE results in less nerve damage and faster nerve recovery than LASIK.

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

PubMed

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

2015-08-01

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

Identification of the Infection Source of an Outbreak of Mycobacterium Chelonae Keratitis After Laser in Situ Keratomileusis.

PubMed

Nascimento, Heloisa; Viana-Niero, Cristina; Nogueira, Christiane Lourenço; Martins Bispo, Paulo José; Pinto, Fernando; de Paula Pereira Uzam, Camila; Matsumoto, Cristianne Kayoko; Oliveira Machado, Antônia Maria; Leão, Sylvia Cardoso; Höfling-Lima, Ana Luisa; de Freitas, Denise

2018-01-01

Nontuberculous mycobacteria keratitis is a rare but challenging complication of laser in situ keratomileusis (LASIK). This study was conducted to determine the source(s) of infection in a cluster of cases of keratitis after LASIK and to describe this outbreak and patients' outcomes. In this retrospective, case series, single-center study, 86 patients were included who underwent LASIK or photorefractive keratectomy between December 2011 and February 2012. Corneal scrapes from the affected eyes, samples of tap and distilled water, water from the reservoir of the distilling equipment, steamer, and autoclave cassette; antiseptic and anesthetic solutions and surgical instrument imprints were cultivated in liquid and on solid media. Gram-negative bacteria and yeasts were identified using automated systems and mycobacteria by polymerase chain reaction-restriction enzyme analysis of the hsp65 gene (PRA-hsp65) and DNA sequencing. Mycobacterial isolates were typed by pulsed-field gel electrophoresis. The cases and outcomes are described. The main outcome measure was identification of the source(s) of the mycobacterial infections. Eight (15 eyes) of 86 patients (172 eyes) who underwent LASIK developed infections postoperatively; no patients who underwent photorefractive keratectomy developed infections. Mycobacterium chelonae was isolated from 4 eyes. The distilled water collected in the surgical facility contained the same M. chelonae strain isolated from the patients' eyes. Different gram-negative bacteria and yeasts were isolated from samples collected at the clinic but not from the patients' eyes. Tap water distilled locally in surgical facilities may be a source of infection after ocular surgery and its use should be avoided.

Fibrin adhesive in conjunction with epithelial ingrowth removal after laser in situ keratomileusis: long-term results.

PubMed

Hardten, David R; Fahmy, Mona M; Vora, Gargi K; Berdahl, John P; Kim, Terry

2015-07-01

To describe the long-term results of fibrin adhesive use in the management of epithelial ingrowth after laser in situ keratomileusis (LASIK). Private practice, Minneapolis, Minnesota, and an academic medical center, Durham, North Carolina, USA. Retrospective case series. Patients with a history of LASIK had epithelial ingrowth removal with mechanical debridement and fibrin glue application. Visual outcomes and the presence or absence of epithelial ingrowth were evaluated again after 3 months and at the last follow-up. The main outcome measures were recurrence of epithelial ingrowth and visual acuity. Thirty-nine eyes of 38 patients were evaluated. After epithelial ingrowth removal and application of fibrin glue, 31 eyes (79.5%) had no recurrence of ingrowth at the final follow-up and 5 eyes (12.8%) had mild epithelial ingrowth not requiring removal. Three eyes (7.7%) had significant epithelial ingrowth at the 3-month follow-up that required subsequent removal and fibrin application. At the 3-month follow-up visit, 76.9% of eyes achieved 20/25 or better corrected distance visual acuity (CDVA) and 69.2% of eyes achieved 20/40 or better uncorrected distance visual acuity (UDVA). At the last follow-up visit (mean 26.6 ± 17.0 months [SD]), 84.6% of eyes had 20/25 or better CDVA and 74.4% of eyes had 20/40 or better UDVA. Fibrin adhesive in conjunction with manual epithelial removal prevented a clinically significant recurrence of epithelial ingrowth in the majority of eyes. Larger randomized studies are needed to compare the success of this technique with that of others. No author has a financial or proprietary interest in any material or method mentioned. Copyright © 2015 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.

Effect of Macrophage Migration Inhibitory Factor on Corneal Sensitivity after Laser In Situ Keratomileusis in Rabbit

PubMed Central

Hose, Stacey; Gongora, Celine; Sinha, Debasish; O'Brien, Terrence

2014-01-01

Purpose To investigate the effect of macrophage migration inhibitory factor (MIF) on corneal sensitivity after laser in situ keratomileusis (LASIK) surgery. Methods New Zealand white rabbits were used in this study. A hinged corneal flap (160-µm thick) was created with a microkeratome, and -3.0 diopter excimer laser ablation was performed. Expressions of MIF mRNA in the corneal epithelial cells and surrounding inflammatory cells were analyzed using reverse transcription polymerase chain reaction at 48 hours after LASIK. After LASIK surgery, the rabbits were topically given either 1) a balanced salt solution (BSS), 2) MIF (100 ng/mL) alone, or 3) a combination of nerve growth factor (NGF, 100 ug/mL), neurotrophine-3 (NT-3, 100 ng/mL), interleukin-6 (IL-6, 5 ng/mL), and leukemia inhibitory factor (LIF, 5 ng/mL) four times a day for three days. Preoperative and postoperative corneal sensitivity at two weeks and at 10 weeks were assessed using the Cochet-Bonnet esthesiometer. Results Expression of MIF mRNA was 2.5-fold upregulated in the corneal epithelium and 1.5-fold upregulated in the surrounding inflammatory cells as compared with the control eyes. Preoperative baseline corneal sensitivity was 40.56 ± 2.36 mm. At two weeks after LASIK, corneal sensitivity was 9.17 ± 5.57 mm in the BSS treated group, 21.92 ± 2.44 mm in the MIF treated group, and 22.42 ± 1.59 mm in the neuronal growth factors-treated group (MIF vs. BSS, p < 0.0001; neuronal growth factors vs. BSS, p < 0.0001; MIF vs. neuronal growth factors, p = 0.815). At 10 weeks after LASIK, corneal sensitivity was 15.00 ± 9.65, 35.00 ± 5.48, and 29.58 ± 4.31 mm respectively (MIF vs. BSS, p = 0.0001; neuronal growth factors vs. BSS, p = 0.002; MIF vs. neuronal growth factors, p = 0.192). Treatment with MIF alone could achieve as much of an effect on recovery of corneal sensation as treatment with combination of NGF, NT-3, IL-6, and LIF. Conclusions Topically administered MIF plays a significant role in the

Effect of macrophage migration inhibitory factor on corneal sensitivity after laser in situ keratomileusis in rabbit.

PubMed

Hyon, Joon Young; Hose, Stacey; Gongora, Celine; Sinha, Debasish; O'Brien, Terrence

2014-04-01

To investigate the effect of macrophage migration inhibitory factor (MIF) on corneal sensitivity after laser in situ keratomileusis (LASIK) surgery. New Zealand white rabbits were used in this study. A hinged corneal flap (160-µm thick) was created with a microkeratome, and -3.0 diopter excimer laser ablation was performed. Expressions of MIF mRNA in the corneal epithelial cells and surrounding inflammatory cells were analyzed using reverse transcription polymerase chain reaction at 48 hours after LASIK. After LASIK surgery, the rabbits were topically given either 1) a balanced salt solution (BSS), 2) MIF (100 ng/mL) alone, or 3) a combination of nerve growth factor (NGF, 100 ug/mL), neurotrophine-3 (NT-3, 100 ng/mL), interleukin-6 (IL-6, 5 ng/mL), and leukemia inhibitory factor (LIF, 5 ng/mL) four times a day for three days. Preoperative and postoperative corneal sensitivity at two weeks and at 10 weeks were assessed using the Cochet-Bonnet esthesiometer. Expression of MIF mRNA was 2.5-fold upregulated in the corneal epithelium and 1.5-fold upregulated in the surrounding inflammatory cells as compared with the control eyes. Preoperative baseline corneal sensitivity was 40.56 ± 2.36 mm. At two weeks after LASIK, corneal sensitivity was 9.17 ± 5.57 mm in the BSS treated group, 21.92 ± 2.44 mm in the MIF treated group, and 22.42 ± 1.59 mm in the neuronal growth factors-treated group (MIF vs. BSS, p < 0.0001; neuronal growth factors vs. BSS, p < 0.0001; MIF vs. neuronal growth factors, p = 0.815). At 10 weeks after LASIK, corneal sensitivity was 15.00 ± 9.65, 35.00 ± 5.48, and 29.58 ± 4.31 mm respectively (MIF vs. BSS, p = 0.0001; neuronal growth factors vs. BSS, p = 0.002; MIF vs. neuronal growth factors, p = 0.192). Treatment with MIF alone could achieve as much of an effect on recovery of corneal sensation as treatment with combination of NGF, NT-3, IL-6, and LIF. Topically administered MIF plays a significant role in the early recovery of corneal

Patient age, refractive index of the corneal stroma, and outcomes of uneventful laser in situ keratomileusis.

PubMed

Patel, Sudi; Alió, Jorge L; Walewska, Anna; Amparo, Francisco; Artola, Alberto

2013-03-01

To determine the influence of age and the corneal stromal refractive index on the difference between the predicted and actual postoperative refractive error after laser in situ keratomileusis (LASIK) and whether the precision of outcomes could be improved by considering age and the refractive index. Vissum Instituto Oftalmologico de Alicante, Alicante, Spain. Case series. Flaps were created using a mechanical microkeratome. The stromal refractive index was measured using a VCH-1 refractometer after flap lifting. Refractive data were obtained 1, 3, and 6 months postoperatively. Uneventful LASIK was performed in 133 eyes. The mean age, refractive index, and applied corrections were 33.4 years ± 9.49 (SD), 1.368 ± 0.006, and -2.43 ± 3.36 diopters (D), respectively. The difference between the predicted and actual postoperative refractive error = 2.315-0.021 age-1.106 refractive index (F = 3.647, r = 0.254, P=.029; n = 109) at 1 month and = 11.820-0.023 age-7.976 refractive index (F = 3.392, r = 0.261, P=.022, n = 106) at 3 months. A correlation between the actual and calculated postoperative refraction improved from r = -0.178 (P=.064; n = 75) to r = -0.418 (P<.001) after considering the true refractive index 6 months postoperatively. The predicted outcomes of LASIK can be improved by inputting the refractive index of the individual corneal stroma. Unexpected outcomes (>0.50 D) of LASIK could be avoided by considering patient age and the refractive index and by adjusting the applied correction accordingly. Copyright © 2012 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.

Combination therapy with diquafosol tetrasodium and sodium hyaluronate in patients with dry eye after laser in situ keratomileusis.

PubMed

Toda, Ikuko; Ide, Takeshi; Fukumoto, Teruki; Ichihashi, Yoshiyuki; Tsubota, Kazuo

2014-03-01

To evaluate the possible advantages of combination therapy with diquafosol tetrasodium and sodium hyaluronate for dry eye after laser in situ keratomileusis (LASIK). Prospective randomized comparative trial. A total of 206 eyes of 105 patients who underwent LASIK were enrolled in this study. Patients were randomly assigned to 1 of 4 treatment groups according to the postoperative treatment: artificial tears, sodium hyaluronate, diquafosol tetrasodium, and a combination of hyaluronate and diquafosol. Questionnaire responses reflecting subjective dry eye symptoms, uncorrected and corrected visual acuity, functional visual acuity, manifest refraction, tear break-up time, fluorescein corneal staining, Schirmer test, and corneal sensitivity were examined before and 1 week and 1 month after LASIK. Distance uncorrected visual acuity was significantly better in the combination group than in the hyaluronate group 1 week and 1 month after LASIK. Near uncorrected visual acuity was significantly better in the combination group than in the artificial tear and diquafosol groups 1 week and 1 month after LASIK. Distance functional visual acuity improved significantly only in the combination group 1 month after LASIK. The Schirmer value in the combination group was significantly higher than that in the hyaluronate group at 1 month after LASIK. Subjective dry eye symptoms in the combination group improved significantly compared with those in the other groups 1 week after surgery. Our results suggest that hyaluronate and diquafosol combination therapy is beneficial for early stabilization of visual performance and improvement of subjective dry eye symptoms in patients after LASIK. Copyright © 2014 Elsevier Inc. All rights reserved.

Evaluation of Biomechanical Changes in Myopia Patients with Unsatisfactory Corneas After Femto Second-Laser In Situ Keratomileusis (FS-LASIK) Concurrent with Accelerated Corneal Collagen Cross-Linking Using Corvis-ST: Two-Year Follow-Up Results.

PubMed

Xu, Weiwei; Tao, Ye; Wang, Liqiang; Huang, Yifei

2017-07-27

BACKGROUND Some myopia patients with unsatisfactory corneas consider corneal refractive surgery for different reasons. Accelerated corneal collagen crosslinking (ACXL) is an effective method to enhance the resistance of the cornea. The present investigation was designed to evaluate the changes of biomechanical properties in patients with myopia and thin corneas after femtosecond-laser in situ keratomileusis (FS-LASIK) concurrent with ACXL. MATERIAL AND METHODS A prospective study was designed. A total of 22 eyes of 11 myopia astigmatism patients with unsatisfactory corneas were enrolled. The patients were assigned to femtosecond-laser in situ keratomileusis concurrent with accelerated corneal collagen crosslinking (FS-LASIK-ACXL). The follow-up duration was 24 months. Manifest refraction, uncorrected (UDVA), and corrected distance visual acuity (CDVA), ultra-high-speed camera (Corvis-ST), corneal topography, anterior segment OCT (AS-OCT), Pentacam, and endothelial cell density (ECD) were examined before and after the operation. The corneal biomechanical and refractive data was analyzed using SAS9.3. Data were analyzed through normal distribution test and variance of analysis. The difference was considered as statistically significant when p<0.05. RESULTS The steep K (Ks) values, flat K (Kf) values, average keratometry values (Avek) values, and central corneal thickness (CCT) declined significantly after FS-LASIK-ACXL operation. The values of first applanation length (A1L), the second applanation length (A2L), the first applanation velocity (A1V), the second applanation velocity (A2V), deformation amplitude (DA), highest concavity peak distance (PD), and radius of curvature at the time of highest concavity (HCR) did not show significant difference after the operation. CONCLUSIONS FS-LASIK-ACXL is an effective and safe surgery for improving visual acuity for myopic patients with thin corneas, and it does not increase the risk of iatrogenic keratectasia.

Early changes in ocular surface and tear inflammatory mediators after small-incision lenticule extraction and femtosecond laser-assisted laser in situ keratomileusis.

PubMed

Gao, Shaohui; Li, Saiqun; Liu, Liangping; Wang, Yong; Ding, Hui; Li, Lili; Zhong, Xingwu

2014-01-01

To characterize the early ocular-surface changes or tear inflammatory-mediators levels following small-incision lenticule extraction (ReLEx smile) and femtosecond laser-assisted laser in situ keratomileusis (FS-LASIK). Forty-seven myopic subjects were recruited for this prospective study. Fifteen underwent ReLEx smile and thirty-two underwent FS-LASIK. Corneal fluorescein (FL) staining, tear break-up time (TBUT), Schirmer I test (SIT), ocular surface disease index (OSDI) and central corneal sensitivity were evaluated in all participants. Tears were collected and analyzed for interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), nerve growth factor (NGF) and intercellular adhesion molecule-1 (ICAM-1) levels using multiplex magnetic beads. All measurements were preformed preoperatively and 1 day, 1 week, 1 month and 3 months postoperatively. FL scores in ReLEx smile group were lower than those of FS-LASIK group 1 week postoperatively (P = 0.010). Compared to the FS-LASIK group, longer TBUT were observed in ReLEx smile group 1 month (P = 0.029) and 3 months (P = 0.045) postoperatively. No significant differences were found in tear secretion for the two groups (P>0.05). OSDI scores were higher in FS-LASIK group 1 month after surgery (P = 0.020). Higher central corneal sensitivity was observed in ReLEx smile group 1 week, 1 month and 3 months (P<0.05) postoperatively. Compared to FS-LASIK group, lower and faster recovery of IL-6 and NGF levels in tears was observed in ReLEx smile group postoperatively (P<0.05). Tears TNF-α and ICAM-1 concentrations were not significantly different between the two groups at any follow-up time (P>0.05). Moreover, IL-6 and NGF levels correlated with ocular surface changes after ReLEx smile or FS-LASIK. In the early postoperative period, ReLEx smile results in milder ocular surface changes than FS-LASIK. Furthermore, the tear inflammatory mediators IL-6 and NGF may play a crucial role in the ocular surface healing process following Re

A sample predictive model for intraocular pressure following laser in situ keratomileusis for myopia and an "intraocular pressure constant".

PubMed

Bahadir Kilavuzoglu, Ayse Ebru; Bozkurt, Tahir Kansu; Cosar, Cemile Banu; Sener, Asım Bozkurt

2017-06-24

To describe a sample predictive model for intraocular pressure (IOP) following laser in situ keratomileusis (LASIK) for myopia and an IOP constant. The records of patients that underwent LASIK for myopia and myopic astigmatism via WaveLight Allegretto Wave Eye-Q 400 Hz excimer laser and Hansatome XP microkeratome were retrospectively reviewed. Patients with no systemic or ocular disease other than myopia or myopic astigmatism were included in the study. Preoperative and postoperative month 1 data and intraoperative data were used to build the predictive model for IOP after LASIK. The IOP constant was calculated by subtracting the predicted IOP from preoperative IOP. The paired samples t test, Pearson's correlation analysis, curve estimation analysis, and linear regression analysis were used to evaluate the study data. The study included 425 eyes in 214 patients with a mean age of 32 ± 7.8 years. Mean spherical equivalent of the attempted correction (SE-ac) was -3.7 ± 1.7 diopters. Mean post-LASIK decrease in IOP was 4.6 ± 2.3 mmHg. The difference between preoperative and postoperative IOP was statistically significant (P < 0.001). SE-ac, preoperative IOP, and central corneal thickness had highly significant effects on postoperative IOP, based on linear regression analysis (P < 0.001 and R 2  = 0.043, P < 0.001 and R 2  = 0.370, and P < 0.001 and R 2  = 0.132, respectively). Regression model was created (F = 127.733, P < 0.001), and the adjusted R 2 value was 0.548. Evaluation of IOP after LASIK is important in myopic patients. The present study described a practical formula for predicting the true IOP with the aid of an IOP constant value in myopic eyes following LASIK.

Effect of Myopic Defocus on Visual Acuity after Phakic Intraocular Lens Implantation and Wavefront-guided Laser in Situ Keratomileusis

PubMed Central

Kamiya, Kazutaka; Shimizu, Kimiya; Igarashi, Akihito; Kawamorita, Takushi

2015-01-01

This study aimed to investigate the effect of myopic defocus on visual acuity after phakic intraocular lens (IOL) implantation and wavefront-guided laser in situ keratomileusis (wfg-LASIK). Our prospective study comprised thirty eyes undergoing posterior chamber phakic IOL implantation and 30 eyes undergoing wfg-LASIK. We randomly measured visual acuity under myopic defocus after cycloplegic and non-cycloplegic correction. We also calculated the modulation transfer function by optical simulation and estimated visual acuity from Campbell & Green’s retinal threshold curve. Visual acuity in the phakic IOL group was significantly better than that in the wfg-LASIK group at myopic defocus levels of 0, –1, and –2 D (p < 0.001, p < 0.001, and p = 0.02, Mann-Whitney U-test), but not at a defocus of –3 D (p = 0.30). Similar results were also obtained in a cycloplegic condition. Decimal visual acuity values at a myopic defocus of 0, −1, −2, and -3 D by optical simulation were estimated to be 1.95, 1.21, 0.97, and 0.75 in the phakic IOL group, and 1.39, 1.11, 0.94, and 0.71 in the wfg-LASIK group, respectively. From clinical and optical viewpoints, phakic IOL implantation was superior to wfg-LASIK in terms of the postoperative visual performance, even in the presence of low to moderate myopic regression. PMID:25994984

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

Changes in biomechanical properties of the cornea and intraocular pressure after myopic laser in situ keratomileusis using a femtosecond laser for flap creation determined using ocular response analyzer and Goldmann applanation tonometry.

PubMed

Shin, Jonghoon; Kim, Tae Won; Park, Soo Jeong; Yoon, Min; Lee, Ji Woong

2015-03-01

To compare intraocular pressure (IOP) measurements before and after laser in situ keratomileusis (LASIK) using a femtosecond laser for flap creation, and to identify factors that may influence the preoperative and postoperative IOP, and the change in IOP after LASIK. Forty eyes from 20 patients who underwent treatment for myopia using a femtosecond laser for flap creation were enrolled in this study. The IOP and corneal biomechanical markers were prospectively measured preoperatively and 1 month after LASIK with Goldmann applanation tonometry (GAT) and the ocular response analyzer (ORA). Manifest refraction spherical equivalent, central corneal thickness, ablation depth, and mean corneal curvature (K reading) were also recorded. After LASIK, there was a significant reduction in the IOP measurement with respect to the corneal-compensated intraocular pressure (IOPcc) (Δ=-0.67±2.07 mm Hg), Goldmann-correlated pressure (IOPg) (Δ=-3.92±2.19 mm Hg), and GAT (Δ=-2.6±2.51). Multiple regression analysis revealed that the corneal hysteresis (CH) and corneal resistance factor (CRF) are statistically significant predictors of IOPcc, IOPg, and GAT (P<0.000). In this analysis, the preoperative manifest refraction spherical equivalent, CH, and CRF were significant predictors of ΔIOPcc (adjusted R²=0.401) and ΔIOPg (adjusted R²=0.386). The preoperative SE and central corneal thickness significantly predicted ΔGAT (adjusted R²=0.464). ORA provides a more complete measurement of IOP after LASIK with a femtosecond laser than GAT because ORA provides greater knowledge of the corneal biomechanics in terms of CH and CRF.

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

Effect of femtosecond and microkeratome flaps creation on the cornea biomechanics during laser in situ keratomileusis: one year follow-up

PubMed Central

Sun, Qian; Deng, Zheng-Zheng; Zhou, Yue-Hua; Zhang, Jing; Peng, Xiao-Yan

2016-01-01

AIM To compare the corneal biomechanical outcomes at one year after laser in situ keratomileusis (LASIK) with the flaps created by Ziemer and Moria M2 microkeratome with 110 head and -20 blade. METHODS Totally 100 eyes of 50 consecutive patients were enrolled in this prospective study and divided into two groups for corneal flaps created by ZiemerFemto LDV and Moria M2 microkeratome with 110 head and -20 blade. Corneal biomechanical properties including cornea resistance factor (CRF) and cornea hysteresis (CH) were measured before and 1, 3, 6, 12mo after surgery by ocular response analyzer. Central cornea thickness and corneal flap thickness were measured by optical coherence tomography. RESULTS The ablation depth (P=0.693), residual corneal thickness (P=0.453), and postoperative corneal curvature (P=0.264) were not significant different between Ziemer group and Moria 110-20 group after surgery. The residual stromal bed thickness, corneal flap thickness, CH and CRF at 12mo after surgery were significant different between Ziemer group and Moria 110-20 group (P<0.01);Ziemer group gained better corneal biomechanical results. The CRF and CH increased gradually from 1 to 12mo after surgery in Ziemer group, increased from 1 to 6mo but decreased from 6 to 12mo in Moria 110-20 group. Both CRF and CH at one year after surgery increased with the increasing of residual cornea thickness; pre-LASIK CRF, CRF also increased with residual stromal bed thickness, while CH decreased with the increasing of pre-LASIK intraocular pressure and cornea flap thickness (P<0.01). CONCLUSION In one year follow-up, femtosecond laser can provide better cornea flaps with stable cornea biomechanics than mechanical microkeratome. PMID:27803856

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

PubMed

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

2015-01-01

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

Early wound healing of laser in situ keratomileusis-like flaps after treatment with human corneal stromal stem cells.

PubMed

Morgan, Siân R; Dooley, Erin P; Kamma-Lorger, Christina; Funderburgh, James L; Funderburgh, Martha L; Meek, Keith M

2016-02-01

To use a well-established organ culture model to investigate the effects of corneal stromal stem cells on the optical and biomechanical properties of corneal wounds after laser in situ keratomileusis (LASIK)-like flap creation. School of Optometry and Vision Sciences, Cardiff University, Cardiff, Wales, United Kingdom. Experimental study. The LASIK-like flaps were produced in sheep corneas. The flap beds were treated with corneal stromal stem cells and were then replaced and allowed to heal for different periods of up to 3 weeks in organ culture. The optical transmission of the cornea, the force required to detach the flap, and the presence of myofibroblasts near the flap bed were measured. Corneal stromal stem cell-treated flap beds were statistically significantly more transparent after 3 weeks in culture than the untreated controls. At 3 weeks, the mean force necessary to detach the flap was more than twice the force required for the respective control samples. Concurrently, there were 44% activated cells immediately below the flap margin of the controls compared with 29% in the same region of the corneal stromal stem cell-treated flaps. In this system, the presence of corneal stromal stem cells at the wound margin significantly increased the adherence of LASIK-like flaps while maintaining corneal transparency. It is postulated that this is achieved by the deposition of extracellular connective tissue similar to that found in the normal cornea and by the paucity of activated keratocytes (myofibroblasts), which are known to scatter a significant amount of the incident light. No author has a financial or proprietary interest in any material or method mentioned. Copyright © 2016 The Authors. Published by Elsevier Inc. All rights reserved.

Confocal Comparison of Corneal Reinnervation after Small Incision Lenticule Extraction (SMILE) and Femtosecond Laser In Situ Keratomileusis (FS-LASIK)

PubMed Central

Qin, Bing; Zhou, Zimei; Ni, Katherine; Le, Qihua; Xiang, Jun; Wei, Anji; Ma, Weiping; Zhou, Xingtao

2013-01-01

Purpose To evaluate corneal reinnervation, and the corresponding corneal sensitivity and keratocyte density after small incision lenticule extraction (SMILE) and femtosecond laser in situ keratomileusis (FS-LASIK). Methods In this prospective, non-randomized observational study, 18 patients (32 eyes) received SMILE surgery, and 22 patients (42 eyes) received FS-LASIK surgery to correct myopia. The corneal subbasal nerve density and microscopic morphological changes in corneal architecture were evaluated by confocal microscopy prior to surgery and at 1 week, 1 month, 3 months, and 6 months after surgery. A correlation analysis was performed between subbasal corneal nerve density and the corresponding keratocyte density and corneal sensitivity. Results The decrease in subbasal nerve density was less severe in SMILE-treated eyes than in FS-LASIK-treated eyes at 1 week (P = 0.0147), 1 month (P = 0.0243), and 3 months (P = 0.0498), but no difference was detected at the 6-month visit (P = 0.5277). The subbasal nerve density correlated positively with central corneal sensitivity in both groups (r = 0.416, P<0.0001, and r = 0.2567, P = 0.0038 for SMILE group and FS-LASIK group, respectively). The SMILE-treated eyes have a lower risk of developing peripheral empty space with epithelial cells filling in (P = 0.0005). Conclusions The decrease in subbasal nerve fiber density was less severe in the SMILE group than the FS-LASIK group in the first 3 months following the surgeries. The subbasal nerve density was correlated with central corneal sensitivity. PMID:24349069

Confocal comparison of corneal reinnervation after small incision lenticule extraction (SMILE) and femtosecond laser in situ keratomileusis (FS-LASIK).

PubMed

Li, Meiyan; Niu, Lingling; Qin, Bing; Zhou, Zimei; Ni, Katherine; Le, Qihua; Xiang, Jun; Wei, Anji; Ma, Weiping; Zhou, Xingtao

2013-01-01

To evaluate corneal reinnervation, and the corresponding corneal sensitivity and keratocyte density after small incision lenticule extraction (SMILE) and femtosecond laser in situ keratomileusis (FS-LASIK). In this prospective, non-randomized observational study, 18 patients (32 eyes) received SMILE surgery, and 22 patients (42 eyes) received FS-LASIK surgery to correct myopia. The corneal subbasal nerve density and microscopic morphological changes in corneal architecture were evaluated by confocal microscopy prior to surgery and at 1 week, 1 month, 3 months, and 6 months after surgery. A correlation analysis was performed between subbasal corneal nerve density and the corresponding keratocyte density and corneal sensitivity. The decrease in subbasal nerve density was less severe in SMILE-treated eyes than in FS-LASIK-treated eyes at 1 week (P = 0.0147), 1 month (P = 0.0243), and 3 months (P = 0.0498), but no difference was detected at the 6-month visit (P = 0.5277). The subbasal nerve density correlated positively with central corneal sensitivity in both groups (r = 0.416, P<0.0001, and r = 0.2567, P = 0.0038 for SMILE group and FS-LASIK group, respectively). The SMILE-treated eyes have a lower risk of developing peripheral empty space with epithelial cells filling in (P = 0.0005). The decrease in subbasal nerve fiber density was less severe in the SMILE group than the FS-LASIK group in the first 3 months following the surgeries. The subbasal nerve density was correlated with central corneal sensitivity.

Late-onset traumatic dislocation of laser in situ keratomileusis corneal flaps: a case series with many clinical lessons.

PubMed

Ting, Darren Shu Jeng; Danjoux, Jean-Pierre

2018-05-12

To report three cases of late-onset (7-14 years postoperative) traumatic dislocation of laser in situ keratomileusis (LASIK) flaps with epithelial ingrowth that all had delayed surgical intervention. A retrospective, interventional case series of three patients who underwent flap repositioning and mechanical debridement of epithelial ingrowth, all after an initial delayed diagnosis/treatment of dislocated LASIK flap. Visual improvement was noted in all three cases following LASIK flap repositioning and debridement of epithelial ingrowth; patient 1 improved from 20/800 corrected-distance-visual-acuity (CDVA) to 20/20 uncorrected-distance-visual-acuity (UDVA) postoperative (14 years post-LASIK, 5-week interval between injury and surgery), patient 2 improved from 20/50 CDVA to 20/20 CDVA (10 years post-LASIK, 4-month interval between injury and surgery) and patient 3 improved from 20/80 CDVA to 20/60 CDVA (7 years post-LASIK, 14-month interval between injury and surgery). Flap dislocation was not suspected or diagnosed in two patients during the first ophthalmic visit. Postoperative visual outcome was not influenced by the presenting vision but might be negatively affected by the delay in surgical intervention, the presence of preoperative central epithelial ingrowth and postoperative striae. This case series reported one of the longest documented intervals between LASIK and traumatic dislocation of LASIK flap with secondary epithelial ingrowth. Delayed diagnosis and management of flap dislocation after corneal trauma may potentially increase the risk of epithelial ingrowth, recalcitrant flap striae and visual impairment. The presence of late-onset epithelial ingrowth in patients with previous LASIK mandates careful examination for occult flap displacement.

Corneal Collagen Crosslinking Combined with Phototherapeutic Keratectomy and Photorefractive Keratectomy for Corneal Ectasia after Laser in situ Keratomileusis.

PubMed

Zhu, Wei; Han, Yunfei; Cui, Changxia; Xu, Wenwen; Wang, Xuan; Dou, Xiaoxiao; Xu, Linlin; Xu, Yanyun; Mu, Guoying

2018-01-01

The aim of this study was to analyze the effects of corneal crosslinking (CXL) combined with phototherapeutic keratectomy (PTK) and photorefractive keratectomy (PRK) in halting the progression and improving the visual function of corneal ectasia after laser in situ keratomileusis (LASIK). PTK-PRK-CXL was performed on 14 eyes of 14 patients who developed corneal ectasia after LASIK. The visual acuity, spherical refraction and cylinder, corneal topography indices, thinnest corneal thickness (TCT), and endothelial cell count were evaluated at baseline and at 1, 3, 6, and 12 months postoperatively. The mean uncorrected visual acuity improved significantly from 0.64 ± 0.36 logMAR preoperatively to 0.19 ± 0.12 logMAR at 12 months of follow-up (p < 0.001), while the mean best corrected visual acuity improved from 0.21 ± 0.14 logMAR at baseline to 0.04 ± 0.10 logMAR at 12 months postoperatively (p < 0.001). A significant decrease was observed in Kmax and Kmean values from 52.51 ± 6.74 and 43.55 ± 3.37 D at baseline to 45.72 ± 5.18 (p < 0.001) and 40.60 ± 3.05 D (p < 0.001) at the 1-year follow-up. The mean TCT decreased significantly from 419.07 ± 36.56 µm before treatment to 320.93 ± 39.78 µm at 12 months of follow-up (p < 0.001), and there was no significant endothelial cell loss (p > 0.05) beyond 6 months after treatment. PTK-PRK-CXL is a promising procedure to halt the progression of post-LASIK keratectasia with significant visual quality improvement. © 2018 S. Karger AG, Basel.

Early Changes in Ocular Surface and Tear Inflammatory Mediators after Small-Incision Lenticule Extraction and Femtosecond Laser-Assisted Laser In Situ Keratomileusis

PubMed Central

Gao, Shaohui; Li, Saiqun; Liu, Liangping; Wang, Yong; Ding, Hui; Li, Lili; Zhong, Xingwu

2014-01-01

Purpose To characterize the early ocular-surface changes or tear inflammatory-mediators levels following small-incision lenticule extraction (ReLEx smile) and femtosecond laser-assisted laser in situ keratomileusis (FS-LASIK). Methods Forty-seven myopic subjects were recruited for this prospective study. Fifteen underwent ReLEx smile and thirty-two underwent FS-LASIK. Corneal fluorescein (FL) staining, tear break-up time (TBUT), Schirmer I test (SIT), ocular surface disease index (OSDI) and central corneal sensitivity were evaluated in all participants. Tears were collected and analyzed for interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), nerve growth factor (NGF) and intercellular adhesion molecule-1 (ICAM-1) levels using multiplex magnetic beads. All measurements were preformed preoperatively and 1 day, 1 week, 1 month and 3 months postoperatively. Results FL scores in ReLEx smile group were lower than those of FS-LASIK group 1 week postoperatively (P = 0.010). Compared to the FS-LASIK group, longer TBUT were observed in ReLEx smile group 1 month (P = 0.029) and 3 months (P = 0.045) postoperatively. No significant differences were found in tear secretion for the two groups (P>0.05). OSDI scores were higher in FS-LASIK group 1 month after surgery (P = 0.020). Higher central corneal sensitivity was observed in ReLEx smile group 1 week, 1 month and 3 months (P<0.05) postoperatively. Compared to FS-LASIK group, lower and faster recovery of IL-6 and NGF levels in tears was observed in ReLEx smile group postoperatively (P<0.05). Tears TNF-α and ICAM-1 concentrations were not significantly different between the two groups at any follow-up time (P>0.05). Moreover, IL-6 and NGF levels correlated with ocular surface changes after ReLEx smile or FS-LASIK. Conclusions In the early postoperative period, ReLEx smile results in milder ocular surface changes than FS-LASIK. Furthermore, the tear inflammatory mediators IL-6 and NGF may play a crucial role

Four-year follow-up of corneal aberrations and visual functions of myopic patients after laser in situ keratomileusis

PubMed Central

Liu, Tai-Xiang; Chen, Yong-Tao; Dan, Ting-Ting; Shi, Rong; Linghu, Shao-Rong; Li, Hai-Xiang

2015-01-01

Objective: To report on 4-year follow-up of corneal higher-order aberrations and daily visual functions of myopic patients after laser in situ keratomileusis (LASIK). Methods: One hundred thirty four eyes of 67 patients who underwent LASIK guided by aspherical ablation were included in this study. The vision, corneal spherical aberration (SphA) and Coma were recorded before LASIK and at 6 month and 4 year after LASIK. The evaluation of the questionnaire about daily visual functions was performed by the same physician after LASIK. Results: No eye decreased the BCVA during 4 year follow-up. The effect index and safety index were 1.08±0.16, 1.11±0.17 and 1.12±0.16, 1.13±0.14 respectively at 6 month and 4 year post-LASIK. After LASIK the corneal SphA and Coma were significantly increased, however the difference between 6 month and 4 year post-LASIK was no statistical significance. Most patients (94.3%-92.4%) felt satisfaction or high satisfaction about the ability to perform each daily visual function after LASIK. Meanwhile there was still about 7.4%-9.2% patients who complained that they could not drive at night. Further analysis showed that the score of driving at night was negative correlation with corneal SphA (r=-0.645, p=0.040; r=-0.688, p=0.040 at 6 month and 4 year post-LASIK respectively). Conclusions: Our four-year follow-up outcomes indicated that the myopic patients after LASIK had the long-term stable corneal aberration and satisfaction of daily visual functions. PMID:26870114

Femtosecond Lasers in Ophthalmology: Surgery and Imaging

NASA Astrophysics Data System (ADS)

Bille, J. F.

Ophthalmology has traditionally been the field with prevalent laser applications in medicine. The human eye is one of the most accessible human organs and its transparency for visible and near-infrared light allows optical techniques for diagnosis and treatment of almost any ocular structure. Laser vision correction (LVC) was introduced in the late 1980s. Today, the procedural ease, success rate, and lack of disturbing side-effects in laser assisted in-situ keratomileusis (LASIK) have made it the most frequently performed refractive surgical procedure (keratomileusis(greek): cornea-flap-cutting). Recently, it has been demonstrated that specific aspects of LVC can take advantage of unique light-matter interaction processes that occur with femtosecond laser pulses.

Photorefractive keratectomy versus laser in situ keratomileusis for moderate to high myopia. A randomized prospective study.

PubMed

Hersh, P S; Brint, S F; Maloney, R K; Durrie, D S; Gordon, M; Michelson, M A; Thompson, V M; Berkeley, R B; Schein, O D; Steinert, R F

1998-08-01

This report presents the results of a randomized clinical trial of photorefractive keratectomy (PRK) and laser-assisted in situ keratomileusis (LASIK). A randomized, prospective multicenter clinical trial. A total of 220 eyes of 220 patients entered the study cohort: 105 randomized to PRK and 115 to LASIK. The mean preoperative manifest refraction spherical equivalent was -9.23 diopters (D) in the PRK group and -9.30 D in the LASIK group. All patients received a one-pass, multizone excimer laser ablation as part of either a PRK or LASIK procedure using the Summit Apex excimer laser. Attempted corrections ranged from 6.00 to 15.00 D. Data on uncorrected and spectacle-corrected visual acuity, predictability,and stability of refraction, corneal haze, and flap complications were analyzed. Patients were observed for up to 6 months. One day after surgery, 0 (0.0%) and 3 (4.5%) eyes in the PRK group saw 20/20 and 20/40 or better uncorrected, respectively, while 7 (10%) and 48 (68.6%) eyes in the LASIK group saw 20/20 and 20/40 or better, respectively. At 6 months after PRK, 13 (19.1%) and 45 (66.2%) eyes saw 20/20 and 20/40 or better, respectively, while after LASIK, 16 (26.2%) and 34 (55.7%) eyes saw 20/20 and 20/40 or better, respectively (odds ratio = 0.56 for likelihood of uncorrected visual acuity < 20/40 for PRK vs. LASIK, 95% confidence interval [CI] = 0.31-1.19). After PRK, 39 eyes (57.4%) were within 1.0 D of attempted correction compared with 24 eyes (40.7%) in the LASIK group (odds ratio = 0.50 for likelihood fo undercorrection 1.0 D for PRK vs. LASIK, 95% CI = 0.24-1.04); however, the standard deviation of the predictability was similar between groups: 1.01 D for PRK and 1.22 D for LASIK. From months 1 to 6, there was an average regression of 0.89 D in the PRK group and 0.55 D in the LASIK group. After PRK, eight eyes (11.8%) had a decrease in spectacle-corrected visual acuity of two Snellen lines or more; after LASIK, two eyes (3.2%) had a decrease of two

Safety and efficacy of a hydrogel inlay with laser in situ keratomileusis to improve vision in myopic presbyopic patients: one-year results.

PubMed

Garza, Enrique Barragan; Chayet, Arturo

2015-02-01

To study the safety and efficacy of implanting a hydrogel corneal inlay (Raindrop Near Vision Inlay) concurrently with performing laser in situ keratomileusis (LASIK) to treat myopic presbyopia and to compare the results with results of the same treatment in emmetropic and hyperopic patients. Two private clinics, Tijuana and Monterrey, Mexico. Prospective nonrandomized clinical trial. Bilateral myopic LASIK was performed and a corneal inlay was concurrently implanted in the nondominant eye under a flap created using a femtosecond laser. Primary safety outcomes were the retention of corrected distance (CDVA) and near (CNVA) visual acuities. Efficacy was evaluated on the basis of uncorrected near (UNVA), intermediate (UIVA), and distance (UDVA) visual acuities. A patient questionnaire was used to assess the preoperative and postoperative incidence of visual symptoms, the ability to perform common tasks with no correction, and patient satisfaction with vision. Thirty eyes were enrolled. At each postoperative visit, the mean CDVA and CNVA were within one half line of preoperative measurements and no eye lost 2 or more lines of CDVA. The mean binocular UDVA, UIVA, and UNVA were better than 20/25 Snellen at all postoperative visits. By 6 months, 93% of patients had a binocular Snellen acuity of 20/25 or better across all visual ranges. According to patient questionnaires, 1 year after surgery, visual symptoms were at preoperative levels, 98% of all visual tasks could be easily performed without correction, and 90% of patients were satisfied or very satisfied with their overall vision. A hydrogel corneal inlay with concurrent LASIK was safe and effective for treating myopic presbyopia. Drs. Garza and Chayet are consultants to and investigators for Revision Optics, Inc. Copyright © 2015. Published by Elsevier Inc.

Increased preference of surface ablation over laser in situ keratomileusis between 2008–2011 is correlated to risk of ecatasia

PubMed Central

Moisseiev, Elad; Sela, Tzahi; Minkev, Liza; Varssano, David

2013-01-01

Purpose To evaluate the trends in corneal refractive procedure selection for the correction of myopia, focusing on the relative proportions of laser in situ keratomileusis (LASIK) and surface ablation procedures. Methods Only eyes that underwent LASIK or surface ablation for the correction of myopia between 2008–2011 were included in this retrospective study. Additional recorded parameters included patient age, preoperative manifest refraction, corneal thickness, and calculated residual corneal bed thickness. A risk score was given to each eye, based on these parameters, according to the Ectasia Risk Factor Score System (ERFSS), without the preoperative corneal topography. Results This study included 16,163 eyes, of which 38.4% underwent LASIK and 61.6% underwent surface ablation. The risk score correlated with procedure selection, with LASIK being preferred in eyes with a score of 0 and surface ablation in eyes with a score of 2 or higher. When controlling for age, preoperative manifest refraction, corneal thickness, and all parameters, the relative proportion of surface ablation compared with LASIK was found to have grown significantly during the study period. Conclusions Our results indicate that with time, surface ablation tended to be performed more often than LASIK for the correction of myopia in our cohort. Increased awareness of risk factors and preoperative risk assessment tools, such as the ERFSS, have shifted the current practice of refractive surgery from LASIK towards surface ablation despite the former’s advantages, especially in cases in which the risk for ectasia is more than minimal (risk score 2 and higher). PMID:23345963

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

PubMed Central

2014-01-01

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

Predictive factor analysis for successful performance of iris recognition-assisted dynamic rotational eye tracking during laser in situ keratomileusis.

PubMed

Prakash, Gaurav; Ashok Kumar, Dhivya; Agarwal, Amar; Jacob, Soosan; Sarvanan, Yoga; Agarwal, Athiya

2010-02-01

To analyze the predictive factors associated with success of iris recognition and dynamic rotational eye tracking on a laser in situ keratomileusis (LASIK) platform with active assessment and correction of intraoperative cyclotorsion. Interventional case series. Two hundred seventy-five eyes of 142 consecutive candidates underwent LASIK with attempted iris recognition and dynamic rotational tracking on the Technolas 217z100 platform (Techolas Perfect Vision, St Louis, Missouri, USA) at a tertiary care ophthalmic hospital. The main outcome measures were age, gender, flap creation method (femtosecond, microkeratome, epi-LASIK), success of static rotational tracking, ablation algorithm, pulses, and depth; preablation and intraablation rotational activity were analyzed and evaluated using regression models. Preablation static iris recognition was successful in 247 eyes, without difference in flap creation methods (P = .6). Age (partial correlation, -0.16; P = .014), amount of pulses (partial correlation, 0.39; P = 1.6 x 10(-8)), and gender (P = .02) were significant predictive factors for the amount of intraoperative cyclodeviation. Tracking difficulties leading to linking the ablation with a new intraoperatively acquired iris image were more with femtosecond-assisted flaps (P = 2.8 x 10(-7)) and the amount of intraoperative cyclotorsion (P = .02). However, the number of cases having nonresolvable failure of intraoperative rotational tracking was similar in the 3 flap creation methods (P = .22). Intraoperative cyclotorsional activity depends on the age, gender, and duration of ablation (pulses delivered). Femtosecond flaps do not seem to have a disadvantage over microkeratome flaps as far as iris recognition and success of intraoperative dynamic rotational tracking is concerned. Copyright (c) 2010 Elsevier Inc. All rights reserved.

Laser-assisted in-situ keratomileusis (LASIK) versus photorefractive keratectomy (PRK) for myopia.

PubMed

Shortt, Alex J; Allan, Bruce D S; Evans, Jennifer R

2013-01-31

Myopia (also known as short-sightedness or near-sightedness) is an ocular condition in which the refractive power of the eye is greater than is required, resulting in light from distant objects being focused in front of the retina instead of directly on it. The two most commonly used surgical techniques to permanently correct myopia are photorefractive keratectomy (PRK) and laser-assisted in-situ keratomileusis (LASIK). To compare the effectiveness and safety of LASIK and PRK for correction of myopia by examining post-treatment uncorrected visual acuity, refractive outcome, loss of best spectacle-corrected visual acuity, pain scores, flap complications in LASIK, subepithelial haze, adverse events, quality of life indices and higher order aberrations. We searched CENTRAL (which contains the Cochrane Eyes and Vision Group Trials Register) (The Cochrane Library 2012, Issue 11), Ovid MEDLINE, Ovid MEDLINE In-Process and Other Non-Indexed Citations, Ovid MEDLINE Daily, Ovid OLDMEDLINE (January 1946 to November 2012), EMBASE (January 1980 to November 2012), Latin American and Caribbean Literature on Health Sciences (LILACS) (January 1982 to November 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). We did not use any date or language restrictions in the electronic searches for trials. We last searched the electronic databases on 15 November 2012. We also searched the reference lists of the studies and the Science Citation Index. We included randomised controlled trials comparing LASIK and PRK for the correction of any degree of myopia. Two authors independently assessed trial quality and extracted data. We summarised data using the odds ratio and mean difference. We combined odds ratios using a random-effects model after testing for heterogeneity. We included 13 trials (1135 participants, 1923 eyes

Change in the accommodative convergence per unit of accommodation ratio after bilateral laser in situ keratomileusis for myopia in orthotropic patients: prospective evaluation.

PubMed

Prakash, Gaurav; Choudhary, Vandana; Sharma, Namrata; Titiyal, Jeewan S

2007-12-01

To analyze the effect of bilateral laser in situ keratomileusis (LASIK) on the accommodative convergence per unit of accommodation (AC/A) ratio in otherwise normal orthotropic myopic patients. Cornea and refractive services of a tertiary-care ophthalmic center. This prospective clinical trial consisted of 61 myopic patients who had bilateral LASIK. Those with manifest tropia, previous squint surgery, amblyopia, or absent or impaired binocularity or those in whom monovision was planned were excluded. The preoperative examination included visual acuity, cycloplegic refraction, assessment of binocularity, a prism cover test, and evaluation of the stimulus AC/A ratio by the gradient method. All patients had LASIK using the Zyoptix platform (Bausch & Lomb). Postoperative evaluation included uncorrected and best corrected visual acuities, residual refraction, and the AC/A ratio. All patients had a follow-up of 9 months. There was significant decrease in the mean AC/A ratio at the 1-week and 1-month follow-ups. The AC/A progressively recovered to near preoperative values between 3 months and 9 months after surgery (analysis of variance test). There was a significant reduction in the number of symptomatic patients from the first month onward (chi square = 89.23; P<.001). The AC/A ratio varied after LASIK, stabilizing between 3 months and 9 months after surgery. This suggests that the maximum variation in the accommodation-convergence relationship after LASIK occurs in the first 3 months.

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

PubMed

Kanellopoulos, Anastasios John; Asimellis, George

2015-07-01

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

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

PubMed Central

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

2015-01-01

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

Effect of insulin-like growth factor-1 on corneal surface ultrastructure and nerve regeneration of rabbit eyes after laser in situ keratomileusis.

PubMed

Wang, Chunyan; Peng, Yanli; Pan, Shuling; Li, Li

2014-01-13

To explore the effect of insulin-like growth factor-1 (IGF-1) on corneal surface ultrastructure and nerve regeneration in rabbit models after laser in situ keratomileusis (LASIK). Forty-two healthy New Zealand white rabbits were divided into two groups, the IGF-1 group and the control group, and LASIK surgery was performed. The corneal surface ultrastructure was observed by transmission electron microscopy, and the nerve regeneration was evaluated by counting the newly regenerated nerves at 1 d, 1 w, 2 w, 1 m, 3 m and 6 m after surgery. Dry eye parameters, including the Schirmer I test and tear break-up time, were examined at all time points. The examination of corneal ultrastructure showed that the number of corneal epithelial microvilli in the IGF-1 group was significantly higher than that in the normal saline (NS) group except in the second postoperative week (p<0.05). The observation of corneal nerve regeneration showed that the number of regenerated nerve fibers in the IGF-1 group was higher than the control group at all time points (p<0.05). The parameters of dry eye were significantly higher in the IGF-1 group compared to the control group at all time points except at 1d and 6m after LASIK. IGF-1 can effectively accelerate the early repair of corneal surface ultrastructure and nerve regeneration after LASIK and relieve dry eye symptoms in rabbit eyes. Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.

Comparison of photorefractive keratectomy and laser in situ keratomileusis for myopia of -6 D or less using the Nidek EC-5000 laser.

PubMed

Fernández, A P; Jaramillo, J; Jaramillo, M

2000-01-01

We compared the efficacy, predictability, and safety of photorefractive keratectomy (PRK) and laser in situ keratomileusis (LASIK) for the surgical correction of low and moderate myopia. A retrospective study was performed to evaluate uncorrected and spectacle-corrected visual acuity, and manifest refraction 1 year after PRK or LASIK. All procedures were done using an automatic microkeratome (Chiron Ophthalmic) and the Nidek EC-5000 excimer laser. PRK was performed in 75 eyes of 45 patients and LASIK in 133 eyes of 77 patients. Mean age for PRK patients was 32.8 years (range, 18 to 52 yr) and LASIK patients was 29.6 years (range, 18 to 49 yr). Mean preoperative spherical equivalent refraction for PRK patients was -3.28 D (range, -1.00 to -6.00 D) and LASIK, -3.86 D (range, -1.00 to -6.00 D). One year after surgery, mean spherical equivalent refraction for Group 1 (baseline, -1.00 to -3.00 D) PRK eyes was -0.18 +/- 0.61 D (range, -1.50 to +0.75 D) and for LASIK eyes, -0.08 +/- 0.61 D (range, -1.50 to +1.62 D), with no statistically significant difference. For Group 2 eyes (baseline, -3.25 to -6.00 D), mean spherical equivalent refraction for PRK eyes was -0.44 +/- 0.87 D (range, -2.00 to +2.12 D) and for LASIK eyes, -0.09 +/- 0.83 D (range, -1.50 to +1.75 D), with no statistically significant difference. The antilogarithm of the mean UCVA (antilogUCVA) in Group 1 for PRK was 0.79 +/- 0.21 (20/25) and for LASIK was 0.87 +/- 0.19 (20/23), with no statistically significant difference. The antilogUCVA in Group 2 for PRK eyes was 0.70 +/- 0.24 (20/28) and for LASIK eyes was 0.83 +/- 0.18 (20/24), with a statistically significant difference (0.7 vs. 0.83, P < .005). The percentage of eyes with a postoperative UCVA >20/40 in Group 1 for PRK was 91.5% (38 eyes) and for LASIK was 95% (50 eyes) (no statistically significant difference), and in Group 2 for PRK eyes, it was 82% (27 eyes) and 97.5% (78 eyes) for LASIK (statistically significant difference, P < .05). PRK and

A prospective comparison of phakic collamer lenses and wavefront-optimized laser-assisted in situ keratomileusis for correction of myopia

PubMed Central

Parkhurst, Gregory D

2016-01-01

Purpose The aim of this study was to evaluate and compare night vision and low-luminance contrast sensitivity (CS) in patients undergoing implantation of phakic collamer lenses or wavefront-optimized laser-assisted in situ keratomileusis (LASIK). Patients and methods This is a nonrandomized, prospective study, in which 48 military personnel were recruited. Rabin Super Vision Test was used to compare the visual acuity and CS of Visian implantable collamer lens (ICL) and LASIK groups under normal and low light conditions, using a filter for simulated vision through night vision goggles. Results Preoperative mean spherical equivalent was −6.10 D in the ICL group and −6.04 D in the LASIK group (P=0.863). Three months postoperatively, super vision acuity (SVa), super vision acuity with (low-luminance) goggles (SVaG), super vision contrast (SVc), and super vision contrast with (low luminance) goggles (SVcG) significantly improved in the ICL and LASIK groups (P<0.001). Mean improvement in SVaG at 3 months postoperatively was statistically significantly greater in the ICL group than in the LASIK group (mean change [logarithm of the minimum angle of resolution, LogMAR]: ICL =−0.134, LASIK =−0.085; P=0.032). Mean improvements in SVc and SVcG were also statistically significantly greater in the ICL group than in the LASIK group (SVc mean change [logarithm of the CS, LogCS]: ICL =0.356, LASIK =0.209; P=0.018 and SVcG mean change [LogCS]: ICL =0.390, LASIK =0.259; P=0.024). Mean improvement in SVa at 3 months was comparable in both groups (P=0.154). Conclusion Simulated night vision improved with both ICL implantation and wavefront-optimized LASIK, but improvements were significantly greater with ICLs. These differences may be important in a military setting and may also affect satisfaction with civilian vision correction. PMID:27418804

A prospective comparison of phakic collamer lenses and wavefront-optimized laser-assisted in situ keratomileusis for correction of myopia.

PubMed

Parkhurst, Gregory D

2016-01-01

The aim of this study was to evaluate and compare night vision and low-luminance contrast sensitivity (CS) in patients undergoing implantation of phakic collamer lenses or wavefront-optimized laser-assisted in situ keratomileusis (LASIK). This is a nonrandomized, prospective study, in which 48 military personnel were recruited. Rabin Super Vision Test was used to compare the visual acuity and CS of Visian implantable collamer lens (ICL) and LASIK groups under normal and low light conditions, using a filter for simulated vision through night vision goggles. Preoperative mean spherical equivalent was -6.10 D in the ICL group and -6.04 D in the LASIK group (P=0.863). Three months postoperatively, super vision acuity (SVa), super vision acuity with (low-luminance) goggles (SVaG), super vision contrast (SVc), and super vision contrast with (low luminance) goggles (SVcG) significantly improved in the ICL and LASIK groups (P<0.001). Mean improvement in SVaG at 3 months postoperatively was statistically significantly greater in the ICL group than in the LASIK group (mean change [logarithm of the minimum angle of resolution, LogMAR]: ICL =-0.134, LASIK =-0.085; P=0.032). Mean improvements in SVc and SVcG were also statistically significantly greater in the ICL group than in the LASIK group (SVc mean change [logarithm of the CS, LogCS]: ICL =0.356, LASIK =0.209; P=0.018 and SVcG mean change [LogCS]: ICL =0.390, LASIK =0.259; P=0.024). Mean improvement in SVa at 3 months was comparable in both groups (P=0.154). Simulated night vision improved with both ICL implantation and wavefront-optimized LASIK, but improvements were significantly greater with ICLs. These differences may be important in a military setting and may also affect satisfaction with civilian vision correction.

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

PubMed

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

2018-03-01

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

Can Opposite Clear Corneal Incisions Have a Role with Post-laser In Situ Keratomileusis Astigmatism?

PubMed Central

El-Awady, Hatem; Ghanem, Asaad A.

2012-01-01

Purpose: To evaluate the astigmatic correcting effect of paired opposite clear corneal incisions (OCCIs) on the steep axis in patients with residual astigmatism after laser in situ keratomileusis (LASIK) Materials and Methods: Thirty-one eyes of 24 patients with a mean age of 28.4 years ±2.46 (range, 19-36 years) were recruited for the study. Inclusion criteria included residual astigmatism of ≥1.5 diopter (D) after LASIK with inadequate residual stromal bed thickness that precluded ablation. The cohort was divided into two groups; group I (with astigmatism ranging from -1.5 D to -2.5 D) and group II (with astigmatism > -2.5 D). The steep axis was marked prior to surgery. Paired three-step self-sealing opposite clear corneal incisions were performed 1-mm anterior to the limbus on the steep axis with 3.2-mm keratome for group I and 4.1 mm for group II. Patients were examined 1 day, 1 week, 1 month, 3 months and 6 months, postoperatively. Visual acuity, refraction, keratometry, and corneal topography were evaluated preoperatively and postoperatively. Analysis of the difference between groups was performed with the Student t-test. P<0.05 was considered statistically significant. Results: The mean uncorrected visual acuity (UCVA) improved from 0.35±0.13 (range, 0.1-0.6) to 0.78±0.19 (range, 0.5-1) in group I and from 0.26±0.19 (range, 0.1-0.5) to 0.7±0.18 (range, 0.4-1) in group II. The increase in UCVA was statistically significant in both groups (P=0.001, both cases). The mean preoperative and postoperative keratometric astigmatism in group I was 2.0±0.48 D (range, 1.5-2.5 D) and 0.8±0.37 D (range, 0.1-1.4 D), respectively. The decrease in keratometric astigmatism was highly statistically significant in group II (P=0.001.). Mean surgically induced astigmatic reduction by vector analysis was 1.47±0.85 D and 2.21±0.97 D in groups I and II respectively. There were no incision-related complications. Conclusions: Paired OCCIs were predictable and effective in

Small incision lenticule extraction (SMILE) versus laser in-situ keratomileusis (LASIK): study protocol for a randomized, non-inferiority trial.

PubMed

Ang, Marcus; Tan, Donald; Mehta, Jodhbir S

2012-05-31

Small incision lenticule extraction or SMILE is a novel form of 'flapless' corneal refractive surgery that was adapted from refractive lenticule extraction (ReLEx). SMILE uses only one femtosecond laser to complete the refractive surgery, potentially reducing surgical time, side effects, and cost. If successful, SMILE could potentially replace the current, widely practiced laser in-situ keratomileusis or LASIK. The aim of this study is to evaluate whether SMILE is non-inferior to LASIK in terms of refractive outcomes at 3 months post-operatively. Single tertiary center, parallel group, single-masked, paired-eye design, non-inferiority, randomized controlled trial. Participants who are eligible for LASIK will be enrolled for study after informed consent. Each participant will be randomized to receive SMILE and LASIK in each eye. Our primary hypothesis (stated as null) in this non-inferiority trial would be that SMILE differs from LASIK in adults (>21 years old) with myopia (> -3.00 diopter (D)) at a tertiary eye center in terms of refractive predictability at 3 months post-operatively. Our secondary hypothesis (stated as null) in this non-inferiority trial would be that SMILE differs from LASIK in adults (>21 years old) with myopia (> -3.00 D) at a tertiary eye center in terms of other refractive outcomes (efficacy, safety, higher-order aberrations) at 3 months post-operatively. Our primary outcome is refractive predictability, which is one of several standard refractive outcomes, defined as the proportion of eyes achieving a postoperative spherical equivalent (SE) within ±0.50 D of the intended target. Randomization will be performed using random allocation sequence generated by a computer with no blocks or restrictions, and implemented by concealing the number-coded surgery within sealed envelopes until just before the procedure. In this single-masked trial, subjects and their caregivers will be masked to the assigned treatment in each eye. This novel

Small incision lenticule extraction (SMILE) versus laser in-situ keratomileusis (LASIK): study protocol for a randomized, non-inferiority trial

PubMed Central

2012-01-01

Background Small incision lenticule extraction or SMILE is a novel form of ‘flapless’ corneal refractive surgery that was adapted from refractive lenticule extraction (ReLEx). SMILE uses only one femtosecond laser to complete the refractive surgery, potentially reducing surgical time, side effects, and cost. If successful, SMILE could potentially replace the current, widely practiced laser in-situ keratomileusis or LASIK. The aim of this study is to evaluate whether SMILE is non-inferior to LASIK in terms of refractive outcomes at 3 months post-operatively. Methods/Design Single tertiary center, parallel group, single-masked, paired-eye design, non-inferiority, randomized controlled trial. Participants who are eligible for LASIK will be enrolled for study after informed consent. Each participant will be randomized to receive SMILE and LASIK in each eye. Our primary hypothesis (stated as null) in this non-inferiority trial would be that SMILE differs from LASIK in adults (>21 years old) with myopia (> −3.00 diopter (D)) at a tertiary eye center in terms of refractive predictability at 3 months post-operatively. Our secondary hypothesis (stated as null) in this non-inferiority trial would be that SMILE differs from LASIK in adults (>21 years old) with myopia (> −3.00 D) at a tertiary eye center in terms of other refractive outcomes (efficacy, safety, higher-order aberrations) at 3 months post-operatively. Our primary outcome is refractive predictability, which is one of several standard refractive outcomes, defined as the proportion of eyes achieving a postoperative spherical equivalent (SE) within ±0.50 D of the intended target. Randomization will be performed using random allocation sequence generated by a computer with no blocks or restrictions, and implemented by concealing the number-coded surgery within sealed envelopes until just before the procedure. In this single-masked trial, subjects and their caregivers will be masked to the assigned

Comparison of Moderate- to High-Astigmatism Corrections Using WaveFront-Guided Laser In Situ Keratomileusis and Small-Incision Lenticule Extraction.

PubMed

Zhang, Jiamei; Wang, Yan; Chen, Xiaoqin

2016-04-01

To evaluate and compare refractive outcomes of moderate- and high-astigmatism correction after wavefront-guided laser in situ keratomileusis (LASIK) and small-incision lenticule extraction (SMILE). This comparative study enrolled a total of 64 eyes that had undergone SMILE (42 eyes) and wavefront-guided LASIK (22 eyes). Preoperative cylindrical diopters were ≤-2.25 D in moderate- and >-2.25 D in high-astigmatism subgroups. The refractive results were analyzed based on the Alpins vector method that included target-induced astigmatism, surgically induced astigmatism, difference vector, correction index, index of success, magnitude of error, angle of error, and flattening index. All subjects completed the 3-month follow-up. No significant differences were found in the target-induced astigmatism, surgically induced astigmatism, and difference vector between SMILE and wavefront-guided LASIK. However, the average angle of error value was -1.00 ± 3.16 after wavefront-guided LASIK and 1.22 ± 3.85 after SMILE with statistical significance (P < 0.05). The absolute angle of error value was statistically correlated with difference vector and index of success after both procedures. In the moderate-astigmatism group, correction index was 1.04 ± 0.15 after wavefront-guided LASIK and 0.88 ± 0.15 after SMILE (P < 0.05). However, in the high-astigmatism group, correction index was 0.87 ± 0.13 after wavefront-guided LASIK and 0.88 ± 0.12 after SMILE (P = 0.889). Both procedures showed preferable outcomes in the correction of moderate and high astigmatism. However, high astigmatism was undercorrected after both procedures. Axial error of astigmatic correction may be one of the potential factors for the undercorrection.

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

PubMed

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

2015-05-01

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

Reliability of Pentacam HR Thickness Maps of the Entire Cornea in Normal, Post-Laser In Situ Keratomileusis, and Keratoconus Eyes.

PubMed

Xu, Zhe; Peng, Mei; Jiang, Jun; Yang, Chun; Zhu, Weigen; Lu, Fan; Shen, Meixiao

2016-02-01

To measure the repeatability and reproducibility of Pentacam HR system thickness maps for the entire cornea in normal, post-laser in situ keratomileusis (post-LASIK), and keratoconus (KC) eyes. Reliability study. Sixty normal subjects (60 eyes), 30 post-LASIK subjects (60 eyes), and 14 KC patients (27 eyes) were imaged with the Pentacam HR system by 2 well-trained operators. For pachymetry the cornea was divided into 4 zones: a central zone (2-mm diameter) and concentric pericentral zone (2-5 mm), transitional zone (5-7 mm), and peripheral zone (7-10 mm). The 3 concentric zones were subdivided into 8 sectors. Intraobserver repeatability and interobserver reproducibility of entire corneal thickness maps were tested by the repeatability and reproducibility coefficients, intraclass correlation coefficients, coefficient of variation, and 95% limits of agreement. From central to peripheral zones, the precision of corneal thickness measurements became gradually smaller. Central zone repeatability and reproducibility were the best in the normal, post-LASIK, and KC groups. The peripheral superior sectors showed poorer repeatability and reproducibility for all subjects. The intraobserver repeatability and interobserver reproducibility for all zones were ≤19.3 μm, ≤22.1 μm, and ≤20.7 μm, in the normal, post-LASIK, and KC groups, respectively. The intraobserver and interobserver coefficients of variation for all zones were ≤1.3%, ≤1.6%, and ≤1.6% for all 3 groups. Pentacam HR system pachymetry of the entire cornea provided good precision in normal, post-LASIK, and KC corneas. Thickness measurements in the peripheral cornea should be interpreted with caution in abnormal corneas after surgery or with diseases. Copyright © 2016 Elsevier Inc. All rights reserved.

The effect of flap thickness on corneal biomechanics after myopic laser in situ keratomileusis using the M-2 microkeratome.

PubMed

Goussous, Iyad A; El-Agha, Mohamed-Sameh; Awadein, Ahmed; Hosny, Mohamed H; Ghaith, Alaa A; Khattab, Ahmed L

2017-01-01

The purpose of this study was to determine the effect of flap thickness on corneal biomechanics after myopic laser in situ keratomileusis (LASIK). This is a prospective controlled non-randomized, institutional study. Patients underwent either epi-LASIK with mitomycin (advanced surface ablation [ASA]), thin-flap LASIK (90 µm head), or thick-flap LASIK (130 µm head). In ASA, the Moria Epi-K hydroseparator was used. LASIK flaps were created using the Moria M-2 mechanical microkeratome. The corneal hysteresis (CH) and corneal resistance factor (CRF) were measured preoperatively and 3 months after surgery, using the Ocular Response Analyzer ® . Ten patients (19 eyes) underwent ASA, 11 patients (16 eyes) underwent thin-flap LASIK, and 11 patients (16 eyes) underwent thick-flap LASIK. The mean preoperative CH was 10.47±0.88, 10.52±1.4, and 11.28±1.4 mmHg ( p =0.043), respectively, decreasing after surgery by 1.75±1.02, 1.66±1.00, and 2.62±1.03 mmHg ( p =0.017). The mean reduction of CH per micron of central corneal ablation was 0.031, 0.023, and 0.049 mmHg/µm ( p =0.005). Mean preoperative CRF was 10.11±1.28, 10.34±1.87, and 10.62±1.76 mmHg ( p =0.66), decreasing after surgery by 2.33±1.35, 2.77±1.03, and 2.92±1.10 mmHg ( p =0.308). The mean reduction of CRF per micron of central corneal ablation was 0.039, 0.040, and 0.051 mmHg/µm ( p =0.112). Thick-flap LASIK caused a greater reduction of CH and CRF than thin-flap LASIK and ASA, although this was statistically significant only for CH. ASA and thin-flap LASIK were found to be biomechanically similar.

Three-year results of small incision lenticule extraction and wavefront-guided femtosecond laser-assisted laser in situ keratomileusis for correction of high myopia and myopic astigmatism.

PubMed

Xia, Li-Kun; Ma, Jing; Liu, He-Nan; Shi, Ce; Huang, Qing

2018-01-01

To compare and calculate the 3-year refractive results, higher-order aberrations (HOAs), contrast sensitivity (CS) and dry eye parameters after small incision lenticule extraction (SMILE) and wavefront-guided femtosecond laser-assisted laser in situ keratomileusis (FS-LASIK) for correction of high myopia and myopic astigmatism. In this prospective, non-randomized comparative study, 78 eyes with spherical equivalent (SE) of -8.11±1.09 diopters (D) received a SMILE surgery, and 65 eyes with SE of -8.05±1.12 D received a wavefront-guided FS-LASIK surgery with the VisuMax femtosecond laser (Carl Zeiss Meditec, Jena, Germany) for flap cutting. Visual acuity, manifest refraction, CS, HOAs, ocular surface disease index (OSDI) and tear break-up time (TBUT) were evaluated during a 3-year follow-up. The difference of uncorrected distance visual acuity (UDVA) postoperatively was achieved at 1mo and at 3mo, whereas the difference of the mean UDVA between two groups at 3y were not statistically significant ( t =-1.59, P =0.13). The postoperative change of SE was 0.89 D in the FS-LASIK group ( t =5.76, P =0.00), and 0.14 D in the SMILE group ( t =0.54, P =0.59) from 1mo to 3y after surgery. At 3-year postoperatively, both HOAs and spherical aberrations in the SMILE group were obviously less than those in the FS-LASIK group ( P =0.00), but the coma root mean square (RMS) was higher in the SMILE group (0.59±0.26) than in the FS-LASIK group (0.29±0.14, P =0.00). The mesopic CS values between two groups were not statistically significant at 3y postoperatively. Compared with the FS-LASIK group, lower OSDI scores and longer TBUT values were found in the SMILE group at 1mo and 3mo postoperatively. With regard to safety, no eye lost any line of CDVA in both groups at 3y after surgery. Both SMILE and wavefront-guided FS-LASIK procedures provide good visual outcomes. Both procedures are effective and safe, but SMILE surgery achieve more stable long-term refractive outcome and better

Comparison of outcomes of conventional WaveLight® Allegretto Wave® and Technolas® excimer lasers in myopic laser in situ keratomileusis

PubMed Central

Han, Daphne CY; Chen, Jean; Htoon, Hla Myint; Tan, Donald TH; Mehta, Jodhbir S

2012-01-01

Objective To compare the results of laser in situ keratomileusis for myopia using WaveLight® Allegretto Wave® Eye-Q® and Technolas® 217z excimer lasers. Method A retrospective, comparative case series of 442 eyes matched for age and myopia: half each were treated with Allegretto’s wavefront-optimized algorithm and Technolas PlanoScan. Outcome measures were postoperative mean logarithm of the minimum angle of resolution (logMAR) uncorrected visual acuity (UCVA), manifest refraction spherical equivalent (MRSE), cylinder, safety and efficacy indices, refractive predictability, and optical zone size selection. Refractive predictability of a subgroup treated for −2.50 to −4.0 diopter (D) was analyzed separately. Results At mean follow-up of 80.5 days, mean logMAR UCVA, mean MRSE and mean postoperative cylinder were 0.02 ± 0.07 (range −0.12 to 0.30), 0.27 ± 0.36 D (range −1.25 to 1.50 D) and −0.33 ± 0.30 D (range 0.00 to −1.50 D) for Allegretto versus 0.02 ± 0.08 (range −0.12 to 0.40), 0.095 ± 0.47 D (range −1.25 to 1.13 D) and −0.44 ± 0.5 2 D (range 0.00 to −2.25 D) for Technolas (P = 0.98, 0.80 and 0.006). Mean safety and efficacy indices were 1.05 ± 0.13 (0.75–1.33) and 0.97 ± 0.13 (0.50–1.33) for Allegretto and 1.07 ± 0.14 (0.75–1.49) and 0.97 ± 0.17 (0.40–1.49) for Technolas (P = 0.23 and 0.69). Proportions of eyes achieving postoperative MRSE within ±1.0 D, ±0.5 D, and ±0.25 D were 98.2%, 91.9% and 75.6% for Allegretto and 99.1%, 97.8% and 72.4% for Technolas (P = 0.68, 0.20 and 0.51). Mean optical zone size selected was 6.48 ± 0.10 mm (range 6.0–6.5 mm) for Allegretto and 6.38 ± 0.19 mm (range 5.6–6.6 mm) for Technolas (P < 0.001). Of the subgroup with treatment between −2.5 and −4.0 D, 86.8% and 58.5% of eyes treated with Allegretto achieved postoperative MRSE within ±0.50 D and ±0.25 D versus 70.4% and 44.4% for Technolas (P = 0.006 and 0.057). Conclusion No differences were seen in postoperative mean

Femtosecond (FS) laser vision correction procedure for moderate to high myopia: a prospective study of ReLEx(®) flex and comparison with a retrospective study of FS-laser in situ keratomileusis.

PubMed

Vestergaard, Anders; Ivarsen, Anders; Asp, Sven; Hjortdal, Jesper Ø

2013-06-01

To present our initial clinical experience with ReLEx(®) flex (ReLEx) for moderate to high myopia. We compare efficacy, safety and corneal higher-order aberrations after ReLEx with femtosecond laser in situ keratomileusis (FS-LASIK). Prospective study of ReLEx compared with a retrospective study of FS-LASIK. ReLEx is a new keratorefractive procedure, where a stromal lenticule is cut by a femtosecond laser and manually extracted. Forty patients were treated with ReLEx on both eyes. A comparable group of 41 FS-LASIK patients were retrospectively identified. Visual acuity, spherical equivalent (SE) and corneal tomography were measured before and 3 months after surgery. Preoperative SE averaged -7.50 ± 1.16 D (ReLEx) and -7.32 ± 1.09 D (FS-LASIK). For all eyes, mean corrected distance visual acuity remained unchanged in both groups. For eyes with emmetropia as target refraction, 41% of ReLEx and 61% of FS-LASIK eyes had an uncorrected distance visual acuity of logMAR ≤ 0.10 at day 1 after surgery, increasing to, respectively, 88% and 69% at 3 months. Mean SE was -0.06 ± 0.35 D 3 months after ReLEx and -0.53 ± 0.60 D after FS-LASIK. The proportion of eyes within ±1.00 D after 3 months was 100% (ReLEx) and 85% (FS-LASIK). For a 6.0-mm pupil, corneal spherical aberrations increased significantly less in ReLEx than FS-LASIK eyes. ReLEx is an all-in-one femtosecond laser refractive procedure, and in this study, results were comparable to FS-LASIK. Refractive predictability and corneal aberrations at 3 months seemed better than or equal to FS-LASIK, whereas visual recovery after ReLEx was slower. © 2012 The Authors. Acta Ophthalmologica © 2012 Acta Ophthalmologica Scandinavica Foundation.

Two-years results of small-incision lenticule extraction and wavefront-guided laser in situ keratomileusis for Myopia.

PubMed

Kobashi, Hidenaga; Kamiya, Kazutaka; Igarashi, Akihito; Takahashi, Masahide; Shimizu, Kimiya

2018-03-01

To compare the 2-years visual and refractive outcomes between small-incision lenticule extraction (SMILE) and wavefront-guided laser in situ keratomileusis (LASIK) in eyes with myopia and myopic astigmatism. Our retrospective case-control study examined 30 eyes of 30 patients with the manifest refraction spherical equivalent (MRSE) of -3.71 ± 1.83 dioptres (D) who underwent SMILE and 30 eyes of 30 patients with MRSE of -3.81 ± 1.40 D who underwent wavefront-guided LASIK. We assessed the 2-years clinical outcomes. Logarithm of the minimal angle of resolution (LogMAR)-corrected distance visual acuity (CDVA) was -0.23 ± 0.07 in the SMILE group and -0.24 ± 0.07 in the wavefront-guided LASIK group 2 years postoperatively (p = 0.82). Logarithm of the minimal angle of resolution-uncorrected distance visual acuity (UDVA) was -0.18 ± 0.09 and -0.15 ± 0.11 (p = 0.30, respectively). In the SMILE and wavefront-guided LASIK groups 2 years postoperatively, 100% and 73% of eyes, respectively, were within 0.5 D of the prompted MRSE correction (p = 0.005). Changes in the MRSE of -0.10 ± 0.30 D and -0.23 ± 0.51 D occurred from 3 months to 2 years (p = 0.40, respectively). We found a significant correlation between myopic regression and the changes in the keratometric readings from 3 months to 2 years after wavefront-guided LASIK (r = -0.48, p = 0.002), but not after SMILE (r = -0.004, p = 0.90). Small-incision lenticule extraction offers better refractive outcomes than wavefront-guided LASIK during a 2-years follow-up for the correction of myopia and myopic astigmatism. © 2017 Acta Ophthalmologica Scandinavica Foundation. Published by John Wiley & Sons Ltd.

Measurement of central corneal thickness with optical low-coherence reflectometry and ultrasound pachymetry in normal and post-femtosecond laser in situ keratomileusis eyes.

PubMed

Huang, Jinhai; Liao, Na; Savini, Giacomo; Li, Yuanguang; Bao, Fangjun; Yu, Ye; Yu, Ayong; Wang, Qinmei

2015-02-01

To determine the repeatability and reproducibility of measurements of central corneal thickness (CCT) using optical low-coherence reflectometry (Lenstar LS900; Haag Streit) in normal eyes and post-femtosecond laser in situ keratomileusis (post-FS-LASIK) eyes and evaluate their agreement with ultrasound (US) pachymetry. CCT was measured using Lenstar and US pachymetry sequentially in normal and post-FS-LASIK eyes by 2 experienced observers. Intraoperator repeatability and interoperator reproducibility were assessed by within-subject standard deviation, test-retest repeatability, coefficient of variation (CoV), and intraclass correlation coefficient. Paired t-tests and Bland-Altman plots were used for analyzing agreement between the 2 devices. In this study, 55 healthy subjects and 50 post-FS-LASIK patients were recruited. Test-retest repeatability of Lenstar was within 10 μm, CoV was less than 1.0%, and intraclass correlation coefficient was more than 0.9 in both normal and post-FS-LASIK groups. Mean difference between these methods was 1.4 ± 4.2 μm and -1.7 ± 5.4 μm, respectively. Moreover, measurements of CCT showed narrow 95% limits of agreement (range, normal group: -6.8 and 9.6 μm; post-FS-LASIK group: -12.4 and 8.9 μm), which implied good agreement. Measurements of CCT using Lenstar showed excellent intraoperator repeatability and interoperator reproducibility both in normal eyes and post-FS-LASIK eyes. Measurements of CCT using Lenstar and US pachymetry showed good agreement and both can be used interchangeably.

Comparison of 5468 retreatments after laser in situ keratomileusis by lifting the flap or performing photorefractive keratectomy on the flap.

PubMed

Ortega-Usobiaga, J; Llovet-Osuna, F; Katz, T; Djodeyre, M R; Druchkiv, V; Bilbao-Calabuig, R; Baviera, J

2018-02-01

To assess visual outcomes of retreatment after laser in situ keratomileusis (LASIK) by lifting the flap or performing photorefractive keratectomy (PRK) on the flap, as well as to establish whether there was an increased risk of epithelial ingrowth (EIG) when LASIK and lifting of the flap are separated by a long time interval and to determine the incidence of corneal haze after PRK. Retrospective study of 4077 patients (5468 eyes) who underwent LASIK and subsequent retreatment were reviewed in order to study their visual results and identify cases of EIG and corneal haze. Enhancements included 5196 eyes from 3876 patients that were retreated by lifting the flap, and 272 eyes from 201 patients that were retreated by PRK on the flap. No statistically significant differences were found between the retreatments in terms of predictability, efficacy, and safety. A total of 704 cases of EIG were found after lifting the flap, for which surgical cleansing was necessary in 70. Surgical cleansing decreased the efficacy index when compared with patients with EIG who did not need cleansing (P=.01). Differences in terms of safety and predictability were not statistically significant. The incidence of corneal haze after ablation of the surface of the previous flap was 14.34%, although none of these cases were clinically relevant. Visual outcomes were similar between patients who were retreated by lifting the flap and those who underwent PRK. The incidence of EIG when the flap was lifted was 13.55%. The incidence of EIG increases with the time elapsed between the primary procedure and retreatment. Copyright © 2017 Sociedad Española de Oftalmología. Publicado por Elsevier España, S.L.U. All rights reserved.

Induced Higher-order aberrations after Laser In Situ Keratomileusis (LASIK) Performed with Wavefront-Guided IntraLase Femtosecond Laser in moderate to high Astigmatism.

PubMed

Al-Zeraid, Ferial M; Osuagwu, Uchechukwu L

2016-03-22

Wavefront-guided Laser-assisted in situ keratomileusis (LASIK) is a widespread and effective surgical treatment for myopia and astigmatic correction but whether it induces higher-order aberrations remains controversial. The study was designed to evaluate the changes in higher-order aberrations after wavefront-guided ablation with IntraLase femtosecond laser in moderate to high astigmatism. Twenty-three eyes of 15 patients with moderate to high astigmatism (mean cylinder, -3.22 ± 0.59 dioptres) aged between 19 and 35 years (mean age, 25.6 ± 4.9 years) were included in this prospective study. Subjects with cylinder ≥ 1.5 and ≤2.75 D were classified as moderate astigmatism while high astigmatism was ≥3.00 D. All patients underwent a femtosecond laser-enabled (150-kHz IntraLase iFS; Abbott Medical Optics Inc) wavefront-guided ablation. Uncorrected (UDVA), corrected (CDVA) distance visual acuity in logMAR, keratometry, central corneal thickness (CCT) and higher-order aberrations (HOAs) over a 6 mm pupil, were assessed before and 6 months, postoperatively. The relationship between postoperative change in HOA and preoperative mean spherical equivalent refraction, mean astigmatism, and postoperative CCT were tested. At the last follow-up, the mean UDVA was increased (P < 0.0001) but CDVA remained unchanged (P = 0.48) and no eyes lost ≥2 lines of CDVA. Mean spherical equivalent refraction was reduced (P < 0.0001) and was within ±0.50 D range in 61% of eyes. The average corneal curvature was flatter by 4 D and CCT was reduced by 83 μm (P < 0.0001, for all), postoperatively. Coma aberrations remained unchanged (P = 0.07) while the change in trefoil (P = 0.047) postoperatively, was not clinically significant. The 4th order HOAs (spherical aberration and secondary astigmatism) and the HOA root mean square (RMS) increased from -0.18 ± 0.07 μm, 0.04 ± 0.03 μm and 0.47 ± 0.11 μm, preoperatively, to 0.33 ± 0

[Comparison of the anterior corneal asphericity after small incision lenticule extraction and femtosecond laser in situ keratomileusis].

PubMed

Su, X L; Wang, Y; Wu, W J; Wu, Z Q; Wu, Y N; Yu, C J

2016-09-11

To evaluate and compare the anterior corneal asphericity after small incision lenticule extraction(SMILE)and femtosecond laser in situ keratomileusis(FS-LASIK). In this case-control study, 45 subjects who underwent SMILE operation comprised the study group, and 33 subjects with FS-LASIK operation comprised the control group. The asphericity coefficient Q-value of the right eyes in both groups was measured at diameters of 6, 7, 8 and 9 mm, respectively, before surgery and at 1 day, 1 week, 1 month and 6 months following surgery. The correlation between the variation of Q-value and the central cutting depth was analyzed. The Q-value of anterior corneal surface was 0.85 ± 0.31, 0.80±0.28, 0.69±0.25 and 0.51±0.23 after SMILE, and 1.13±0.56, 1.01±0.47, 0.80±0.39 and 0.51±0.31 after FS-LASIK at 1 week. In both groups, the Q-value was significantly different before and after surgery(P< 0.05); there were interaction effects between the operation method and time; the difference between the two groups at 6-mm and 7-mm diameters was statistically significant(P<0.05). The variation of the Q-value before and after operation(ΔQ)showed significant difference(P6mm=0.004, P7mm=0.014)between the two groups at 6-mm and 7-mm diameters. The cap diameter of the SMILE group was smaller than that of the FS-LASIK group, but the cutting depth was larger. There was no correlation between ΔQ and the cap/disc diameter. It showed a linear relationship(P<0.05)between ΔQ and the central cutting depth at all examined diameters in the two groups, and the relation degree in the FS-LASIK group was superior to the SMILE group. Both SMILE and FS-LASIK operations can change the negative Q-value of the anterior corneal surface to the positive. The impact of SMILE on the asphericity is smaller than that of FS-LASIK. (Chin J Ophthalmol, 2016, 52: 681-685).

Combined intrastromal astigmatic keratotomy and laser in situ keratomileusis flap followed by photoablation to correct post-penetrating keratoplasty ametropia and high astigmatism: One-year follow-up.

PubMed

Shalash, Riad B; Elshazly, Malak I; Salama, Marwa M

2015-10-01

To evaluate a new technique combining intrastromal astigmatic keratotomy (AK) with a laser in situ keratomileusis (LASIK) flap followed by excimer laser photoablation to correct post-penetrating keratoplasty (PKP) high astigmatism and ametropia. Kasr El Aini Hospital, Cairo University, Cairo, Egypt. Prospective interventional uncontrolled case series. Patients with post-PKP high astigmatism and ametropia had paired intrastromal AK with LASIK flap using the M2 microkeratome followed 2 to 3 months later by excimer laser photoablation. The main outcome measures were uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), mean refractive spherical equivalent (SE), and mean cylinder after each step and at the 1-year follow-up. The study comprised 20 eyes (20 patients). All parameters were significantly improved in all patients by the last follow-up visit. The mean UDVA improved from 1.07 logMAR ± 0.2 (SD) preoperatively to 0.23 ± 0.18 logMAR (P < .001), the mean CDVA improved from 0.79 ± 0.18 logMAR to 0.12 ± 0.12 logMAR (P < .001), the mean refractive SE improved from -5.04 ± 2.62 diopters (D) to -1.47 ± 1.32 D (P = .001), and the mean cylinder reduced from -5.39 ± 0.98 D to -1.05 ± 0.71 D (P < .001). The mean correction index was 0.84 ± 0.10, and the mean flattening index was 0.83 ± 0.10. Thirty-five percent of cases developed microperforations, and 15% developed epithelial ingrowth. This combined approach allowed for the correction of high astigmatism and ametropia following PKP; however, epithelial ingrowth requiring intervention is a complication to be considered. No author has a financial or proprietary interest in any material or method mentioned. Copyright © 2015 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.

Comparison of optical quality after implantable collamer lens implantation and wavefront-guided laser in situ keratomileusis

PubMed Central

Liu, Hong-Ting; Zhou, Zhou; Luo, Wu-Qiang; He, Wen-Jing; Agbedia, Owhofasa; Wang, Jiang-Xia; Huang, Jian-Zhong; Gao, Xin; Kong, Min; Li, Min; Li, Li

2018-01-01

AIM To compare the optical quality after implantation of implantable collamer lens (ICL) and wavefront-guided laser in situ keratomileusis (WG-LASIK). METHODS The study included 40 eyes of 22 patients with myopia who accepted ICL implantation and 40 eyes of 20 patients with myopia who received WG-LASIK. Before surgery and three months after surgery, the objective scattering index (OSI), the values of modulation transfer function (MTF) cutoff frequency, Strehl ratio, and the Optical Quality Analysis System (OQAS) values (OVs) were accessed. The higher order aberrations (HOAs) data including coma, trefoil, spherical, 2nd astigmatism and tetrafoil were also obtained. For patients with pupil size <6 mm, HOAs data were analyzed for 4 mm-pupil diameter. For patients with pupil size ≥6 mm, HOAs data were calculated for 6 mm-pupil diameter. Visual acuity, refraction, pupil size and intraocular pressures were also recorded. RESULTS In both ICL and WG-LASIK group, significant improvements in visual acuities were found postoperatively, with a significant reduction in spherical equivalent (P< 0.001). After the ICL implantation, the OSI decreased slightly from 2.34±1.92 to 2.24±1.18 with no statistical significance (P=0.62). While in WG-LASIK group, the OSI significantly increased from 0.68±0.43 preoperatively to 0.91±0.53 postoperatively (Wilcoxon signed ranks test, P=0.000). None of the mean MTF cutoff frequency, Strehl ratio, OVs showed statistically significant changes in both ICL and WG-LASIK groups. In the ICL group, there were no statistical differences in the total HOAs for either 4 mm-pupil or 6 mm-pupil. In the WG-LASIK group, the HOA parameters increased significantly at 4 mm-pupil. The total ocular HOAs, coma, spherical and 2nd astigmatism were 0.12±0.06, 0.06±0.03, 0.00±0.03, 0.02±0.01, respectively. After the operation, these values were increased into 0.16±0.07, 0.08±0.05, -0.04±0.04, 0.03±0.01 respectively (Wilcoxon signed ranks test, all P<0

Comparison of optical quality after implantable collamer lens implantation and wavefront-guided laser in situ keratomileusis.

PubMed

Liu, Hong-Ting; Zhou, Zhou; Luo, Wu-Qiang; He, Wen-Jing; Agbedia, Owhofasa; Wang, Jiang-Xia; Huang, Jian-Zhong; Gao, Xin; Kong, Min; Li, Min; Li, Li

2018-01-01

To compare the optical quality after implantation of implantable collamer lens (ICL) and wavefront-guided laser in situ keratomileusis (WG-LASIK). The study included 40 eyes of 22 patients with myopia who accepted ICL implantation and 40 eyes of 20 patients with myopia who received WG-LASIK. Before surgery and three months after surgery, the objective scattering index (OSI), the values of modulation transfer function (MTF) cutoff frequency, Strehl ratio, and the Optical Quality Analysis System (OQAS) values (OVs) were accessed. The higher order aberrations (HOAs) data including coma, trefoil, spherical, 2 nd astigmatism and tetrafoil were also obtained. For patients with pupil size <6 mm, HOAs data were analyzed for 4 mm-pupil diameter. For patients with pupil size ≥6 mm, HOAs data were calculated for 6 mm-pupil diameter. Visual acuity, refraction, pupil size and intraocular pressures were also recorded. In both ICL and WG-LASIK group, significant improvements in visual acuities were found postoperatively, with a significant reduction in spherical equivalent ( P < 0.001). After the ICL implantation, the OSI decreased slightly from 2.34±1.92 to 2.24±1.18 with no statistical significance ( P =0.62). While in WG-LASIK group, the OSI significantly increased from 0.68±0.43 preoperatively to 0.91±0.53 postoperatively (Wilcoxon signed ranks test, P =0.000). None of the mean MTF cutoff frequency, Strehl ratio, OVs showed statistically significant changes in both ICL and WG-LASIK groups. In the ICL group, there were no statistical differences in the total HOAs for either 4 mm-pupil or 6 mm-pupil. In the WG-LASIK group, the HOA parameters increased significantly at 4 mm-pupil. The total ocular HOAs, coma, spherical and 2 nd astigmatism were 0.12±0.06, 0.06±0.03, 0.00±0.03, 0.02±0.01, respectively. After the operation, these values were increased into 0.16±0.07, 0.08±0.05, -0.04±0.04, 0.03±0.01 respectively (Wilcoxon signed ranks test, all P <0.05). At 6 mm

When case report became case series: 45 cases of late traumatic flap complications after laser-assisted in situ keratomileusis and review of Chinese literature.

PubMed

Xiao, Jianhe; Jiang, Caihui; Zhang, Maonian; Jiang, Hua; Li, Shiyang; Zhang, Ying

2014-09-01

To report 45 cases of late traumatic flap complications after laser-assisted in situ keratomileusis (LASIK) and discuss the continually increasing number of cases in China. A multicentre retrospective survey of eye injuries was carried in 31 military hospitals from January 2006 to December 2011. Detailed information from the medical records of all 92 cases with a history of prior LASIK treatment were collected and summarised, with respect to visual acuity (VA), flap condition, treatment and final outcome. All Chinese publications relevant to late traumatic flap complications in Chinese patients were retrieved and summarised. 92 inpatients (92 eyes) underwent LASIK surgery; 45 of these had traumatic LASIK flap complications. Flap dislocation was the commonest and most needed surgical repair. VA after treatment was good and no statistically significant difference was observed when compared with the 47 cases without flap complications. 109 articles related to late traumatic flap complications after LASIK were retrieved from four Chinese document databases. There were 550 cases of late traumatic flap complications. From 2004, case reports became more common; 10 or more cases were reported in some case series. VA of most cases was good and there was no remarkable vision loss after treatment. Late traumatic flap complications after LASIK have become more frequent in China, although the prognosis of most cases is good. 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.

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

PubMed

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

2017-02-15

Near-sightedness, or myopia, is a condition in which light rays entering the eye along the visual axis focus in front of the retina, resulting in blurred vision. Myopia can be treated with spectacles, contact lenses, or refractive surgery. Options for refractive surgery include laser-assisted subepithelial keratectomy (LASEK) and laser-assisted in-situ keratomileusis (LASIK). Both procedures utilize a laser to shape the corneal tissue (front of the eye) to correct refractive error, and both create flaps before laser treatment of corneal stromal tissue. Whereas the flap in LASEK is more superficial and epithelial, in LASIK it is thicker and also includes some anterior stromal tissue. LASEK is considered a surface ablation procedure, much like its predecessor, photorefractive keratectomy (PRK). LASEK was developed as an alternative to PRK to address the issue of pain associated with epithelial debridement used for PRK. Assessing the relative benefits and risks/side effects of LASEK and LASIK warrants a systematic review. To assess the effects of LASEK versus LASIK for correcting myopia. We searched the Cochrane Central Register of Controlled Trials (CENTRAL), which contains the Cochrane Eyes and Vision Trials Register (2016, Issue 10); MEDLINE Ovid (1946 to 24 October 2016); Embase.com (1947 to 24 October 2016); PubMed (1948 to 24 October 2016); LILACS (Latin American and Caribbean Health Sciences Literature Database; 1982 to 24 October 2016); the metaRegister of Controlled Trials (mRCT) (www.controlled-trials.com), last searched 20 June 2014; ClinicalTrials.gov (www.clinicaltrials.gov); searched 24 October 2016; and the WHO International Clinical Trials Registry Platform (ICTRP) (www.who.int/ictrp/search/en); searched 24 October 2016. We did not use any date or language restrictions in the electronic searches for trials. We considered only randomized controlled trials (RCTs) for the purposes of this review. Eligible RCTs were those in which myopic participants were

Three-year results of small incision lenticule extraction and wavefront-guided femtosecond laser-assisted laser in situ keratomileusis for correction of high myopia and myopic astigmatism

PubMed Central

Xia, Li-Kun; Ma, Jing; Liu, He-Nan; Shi, Ce; Huang, Qing

2018-01-01

AIM To compare and calculate the 3-year refractive results, higher-order aberrations (HOAs), contrast sensitivity (CS) and dry eye parameters after small incision lenticule extraction (SMILE) and wavefront-guided femtosecond laser-assisted laser in situ keratomileusis (FS-LASIK) for correction of high myopia and myopic astigmatism. METHODS In this prospective, non-randomized comparative study, 78 eyes with spherical equivalent (SE) of -8.11±1.09 diopters (D) received a SMILE surgery, and 65 eyes with SE of -8.05±1.12 D received a wavefront-guided FS-LASIK surgery with the VisuMax femtosecond laser (Carl Zeiss Meditec, Jena, Germany) for flap cutting. Visual acuity, manifest refraction, CS, HOAs, ocular surface disease index (OSDI) and tear break-up time (TBUT) were evaluated during a 3-year follow-up. RESULTS The difference of uncorrected distance visual acuity (UDVA) postoperatively was achieved at 1mo and at 3mo, whereas the difference of the mean UDVA between two groups at 3y were not statistically significant (t=-1.59, P=0.13). The postoperative change of SE was 0.89 D in the FS-LASIK group (t=5.76, P=0.00), and 0.14 D in the SMILE group (t=0.54, P=0.59) from 1mo to 3y after surgery. At 3-year postoperatively, both HOAs and spherical aberrations in the SMILE group were obviously less than those in the FS-LASIK group (P=0.00), but the coma root mean square (RMS) was higher in the SMILE group (0.59±0.26) than in the FS-LASIK group (0.29±0.14, P=0.00). The mesopic CS values between two groups were not statistically significant at 3y postoperatively. Compared with the FS-LASIK group, lower OSDI scores and longer TBUT values were found in the SMILE group at 1mo and 3mo postoperatively. With regard to safety, no eye lost any line of CDVA in both groups at 3y after surgery. CONCLUSION Both SMILE and wavefront-guided FS-LASIK procedures provide good visual outcomes. Both procedures are effective and safe, but SMILE surgery achieve more stable long-term refractive

The effect of flap thickness on corneal biomechanics after myopic laser in situ keratomileusis using the M-2 microkeratome

PubMed Central

Goussous, Iyad A; El-Agha, Mohamed-Sameh; Awadein, Ahmed; Hosny, Mohamed H; Ghaith, Alaa A; Khattab, Ahmed L

2017-01-01

Purpose The purpose of this study was to determine the effect of flap thickness on corneal biomechanics after myopic laser in situ keratomileusis (LASIK). Methods This is a prospective controlled non-randomized, institutional study. Patients underwent either epi-LASIK with mitomycin (advanced surface ablation [ASA]), thin-flap LASIK (90 µm head), or thick-flap LASIK (130 µm head). In ASA, the Moria Epi-K hydroseparator was used. LASIK flaps were created using the Moria M-2 mechanical microkeratome. The corneal hysteresis (CH) and corneal resistance factor (CRF) were measured preoperatively and 3 months after surgery, using the Ocular Response Analyzer®. Results Ten patients (19 eyes) underwent ASA, 11 patients (16 eyes) underwent thin-flap LASIK, and 11 patients (16 eyes) underwent thick-flap LASIK. The mean preoperative CH was 10.47±0.88, 10.52±1.4, and 11.28±1.4 mmHg (p=0.043), respectively, decreasing after surgery by 1.75±1.02, 1.66±1.00, and 2.62±1.03 mmHg (p=0.017). The mean reduction of CH per micron of central corneal ablation was 0.031, 0.023, and 0.049 mmHg/µm (p=0.005). Mean preoperative CRF was 10.11±1.28, 10.34±1.87, and 10.62±1.76 mmHg (p=0.66), decreasing after surgery by 2.33±1.35, 2.77±1.03, and 2.92±1.10 mmHg (p=0.308). The mean reduction of CRF per micron of central corneal ablation was 0.039, 0.040, and 0.051 mmHg/µm (p=0.112). Conclusion Thick-flap LASIK caused a greater reduction of CH and CRF than thin-flap LASIK and ASA, although this was statistically significant only for CH. ASA and thin-flap LASIK were found to be biomechanically similar. PMID:29200820

Comparison of laser in situ keratomileusis flaps created by 2 femtosecond lasers.

PubMed

Zheng, Yan; Zhou, Yuehua; Zhang, Jing; Liu, Qian; Zhai, Changbin; Wang, Yonghua

2015-03-01

To compare flap morphology created by the WaveLight FS200 femtosecond laser and the VisuMax femtosecond laser, assessing the uniformity, accuracy, and predictability of flap creation. A total of 400 eyes had corneal flaps created with the WaveLight FS200 femtosecond laser (200 eyes) or the VisuMax femtosecond laser (200 eyes). The desired flap thickness was 110 μm. At 1 week postoperatively, all eyes were evaluated with RTVue Fourier-domain optical coherence tomography. Dimensions of the flaps were tested for their regularity, uniformity, accuracy, and predictability comparison. One week after surgery, the central flap thickness and the mean flap thickness of the FS200 group were 105.4 ± 3.4 μm and 105.7 ± 2.6 μm, respectively. They were both thinner than those of the VisuMax group, which were 110.8 ± 3.9 μm and 111.3 ± 2.3 μm, respectively. The mean deviation between the achieved and attempted flap thickness of the FS200 group (5.2 ± 1.9 μm) was greater than that of the VisuMax group (3.2 ± 1.8 μm). Flap thickness measurements at 36 points in both groups were close to the intended thickness. Morphology of the flaps in the 0-, 45-, 90-, and 135-degree lines created by the FS200 femtosecond laser and VisuMax femtosecond laser were uniform and regular. Flap dimensions created by the WaveLight FS200 femtosecond laser and VisuMax femtosecond laser were uniform and regular. Although the flap thickness created by the FS200 was less than that created by the VisuMax, measurements of both femtosecond lasers were close to the intended thickness.

Reliability of Entire Corneal Thickness Mapping in Normal Post-Laser in situ Keratomileusis and Keratoconus Eyes Using Long Scan Depth Spectral Domain Optical Coherence Tomography.

PubMed

Xu, Zhe; Chen, Sisi; Yang, Chun; Huang, Shenghai; Shen, Meixiao; Wang, Yuanyuan

2018-01-01

To investigate the repeatability and reproducibility of mapping the entire corneal thickness using spectral domain optical coherence tomography (SD-OCT). Thirty normal eyes, 30 post-laser in situ keratomileusis (LASIK) surgery eyes, and 30 keratoconus eyes were analyzed. A custom-built long scan depth SD-OCT device was used to obtain entire corneal images. Ten-millimeter-diameter corneal thickness maps were generated by an automated segmentation algorithm. Intraclass correlation coefficients of repeatability (ICC1) and reproducibility (ICC2), and coefficients of repeatability (CoR1) and reproducibility (CoR2), were calculated to quantify the precision and accuracy of corneal pachymetry measurements using the Bland-Altman method. For SD-OCT measurements in healthy subjects, CoR1 and CoR2 were less than 5.00 and 5.53 μm. ICC1 and ICC2 were more than 0.997 and 0.996. For SD-OCT measurements in LASIK patients, CoR1 and CoR2 were less than 5.09 and 5.34 μm. ICC1 and ICC2 were more than 0.997 and 0.996. For SD-OCT measurements in keratoconus patients, CoR1 and CoR2 were less than 11.57 and 10.92 μm. ICC1 and ICC2 were more than 0.995 and 0.996. The measurements of corneal pachymetric mapping by long scan depth SD-OCT can be assessed over the entire corneal area with good repeatability and reproducibility. © 2017 S. Karger AG, Basel.

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

PubMed Central

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

2017-01-01

Background Near-sightedness, or myopia, is a condition in which light rays entering the eye along the visual axis focus in front of the retina, resulting in blurred vision. Myopia can be treated with spectacles, contact lenses, or refractive surgery. Options for refractive surgery include laser-assisted subepithelial keratectomy (LASEK) and laser-assisted in-situ keratomileusis (LASIK). Both procedures utilize a laser to shape the corneal tissue (front of the eye) to correct refractive error, and both create flaps before laser treatment of corneal stromal tissue. Whereas the flap in LASEK is more superficial and epithelial, in LASIK it is thicker and also includes some anterior stromal tissue. LASEK is considered a surface ablation procedure, much like its predecessor, photorefractive keratectomy (PRK). LASEK was developed as an alternative to PRK to address the issue of pain associated with epithelial debridement used for PRK. Assessing the relative benefits and risks/side effects of LASEK and LASIK warrants a systematic review. Objectives To assess the effects of LASEK versus LASIK for correcting myopia. Search methods We searched the Cochrane Central Register of Controlled Trials (CENTRAL), which contains the Cochrane Eyes and Vision Trials Register (2016, Issue 10); MEDLINE Ovid (1946 to 24 October 2016); Embase.com (1947 to 24 October 2016); PubMed (1948 to 24 October 2016); LILACS (Latin American and Caribbean Health Sciences Literature Database; 1982 to 24 October 2016); the metaRegister of Controlled Trials (mRCT) (www.controlled-trials.com), last searched 20 June 2014; ClinicalTrials.gov (www.clinicaltrials.gov); searched 24 October 2016; and the WHO International Clinical Trials Registry Platform (ICTRP) (www.who.int/ictrp/search/en); searched 24 October 2016. We did not use any date or language restrictions in the electronic searches for trials. Selection criteria We considered only randomized controlled trials (RCTs) for the purposes of this review

Incidence of corneal infections after laser in situ keratomileusis and surface ablation when moxifloxacin and tobramycin are used as postoperative treatment.

PubMed

Ortega-Usobiaga, Julio; Llovet-Osuna, Fernando; Djodeyre, Mohammad Reza; Llovet-Rausell, Andrea; Beltran, Jaime; Baviera, Julio

2015-06-01

To assess the incidence, culture results, and visual outcomes of infectious keratitis after laser in situ keratomileusis (LASIK) and surface ablation when topical moxifloxacin was added to postoperative prophylaxis with tobramycin. Clínica Baviera, Instituto Oftalmológico Europeo, Bilbao, Spain. Retrospective case series review. The medical records of 55 255 patients (108 014 eyes) who had LASIK and surface ablation were reviewed to identify cases of infectious keratitis. The incidence, risk factors, clinical course, days to diagnosis, treatment, and final visual outcomes were recorded. These data were compared with previously published data of 221 437 eyes that received postoperative tobramycin alone. Post-LASIK infectious keratitis was diagnosed in 10 eyes (9 patients) and post-surface ablation infectious keratitis in 11 eyes (10 patients). The onset of infection was early in 40.00% of cases after LASIK and in 36.36% after surface ablation. Cultures were positive in 2 cases after surface ablation. Immediate flap lifting and irrigation with antibiotics were performed in all eyes after LASIK. The final corrected distance visual acuity was 20/20 or better in 7 cases after LASIK (70.00%) and 7 cases after surface ablation (63.64%) and 20/40 or better in all cases after LASIK or surface ablation. The incidence of infectious keratitis decreased from 0.025% to 0.011% (P < .001) per procedure after LASIK and from 0.200% to 0.066% (P < .001) after surface ablation. Infectious keratitis was less frequent after LASIK than after surface ablation. The frequency of infection, mainly early-onset infection, was lower when the postoperative treatment was tobramycin and moxifloxacin rather than tobramycin alone. No author has a financial or proprietary interest in any material or method mentioned. Copyright © 2015 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.

Inhibition of recurrence of epithelial ingrowth with an amniotic membrane pressure patch to a laser in situ keratomileusis flap with a central stellate laceration: a case report.

PubMed

Kwon, Kye Yoon; Ji, Yong Woo; Lee, Jeihoon; Kim, Eung Kweon

2016-07-18

Surgical lifting and scraping is a well-known treatment for epithelial ingrowth, but treatment for epithelial ingrowth on the centrally perforated laser in situ keratomileusis (LASIK) flap has not been well studied. We present a patient who had epithelial ingrowth to the backside of the flap through a central LASIK flap laceration with a stellate shape. The patient had undergone uncomplicated bilateral LASIK surgery 3 years before the trauma. Because the epithelial ingrowth was suspected during the first visit 2 weeks after trauma, and definite epithelial ingrowth was noted during the additional 2 week observation period, the ingrown epithelial tissue was removed mechanically with a number 15 blade after lifting of the flap 4 weeks after the trauma. An amniotic membrane overlay was applied over the cornea and was sutured tightly to the episclera to firmly press down the flap to the remaining posterior stroma, to prevent growth of the epithelium again to the backside of the flap. At the last follow-up visit, 5 months after surgery, the patient's visual acuity remained stabilized with no sign of recurrent epithelial ingrowth. These results showed that an amniotic membrane patch can be a useful adjuvant in the treatment of epithelial ingrowth, even on the central stellate laceration of the LASIK flap over the visual axis.

A Longitudinal Study on the Effects of Laser Refractive Eye Surgery in Military Aircrew

DTIC Science & Technology

2005-02-01

Photorefractive Keratectomy ( PRK ) and Laser in situ keratomileusis ( LASIK ) have been approved for all classes of licenses providing the clinical...photoréfractive ( PRK ) et la kératomileusie in-situ au laser ( LASIK ) ont été approuvées pour toutes les classes de licences à condition que les résultats...had approved PRK and LASIK for all classes of licenses in Civilian Aviation, provided that the clinical outcome was satisfactory and that minimum

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

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

Wavefront-guided laser in situ keratomileusis (Lasik) versus wavefront-guided photorefractive keratectomy (Prk): a prospective randomized eye-to-eye comparison (an American Ophthalmological Society thesis).

PubMed

Manche, Edward E; Haw, Weldon W

2011-12-01

To compare the safety and efficacy of wavefront-guided laser in situ keratomileusis (LASIK) vs photorefractive keratectomy (PRK) in a prospective randomized clinical trial. A cohort of 68 eyes of 34 patients with -0.75 to -8.13 diopters (D) of myopia (spherical equivalent) were randomized to receive either wavefront-guided PRK or LASIK in the fellow eye using the VISX CustomVue laser. Patients were evaluated at 1 day, 1 week, and months 1, 3, 6, and 12. At 1 month, uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BSCVA), 5% and 25% contrast sensitivity, induction of higher-order aberrations (HOAs), and subjective symptoms of vision clarity, vision fluctuation, ghosting, and overall self-assessment of vision were worse (P<0.05) in the PRK group. By 3 months, these differences had resolved (P>0.05). At 1 year, mean spherical equivalent was reduced 94% to -0.27 ± 0.31 D in the LASIK group and reduced 96% to -0.17 ± 0.41 D in the PRK group. At 1 year, 91% of eyes were within ±0.50 D and 97 % were within ±1.0 D in the PRK group. At 1 year, 88% of eyes were within ±0.50 D and 97% were within ±1.0 D in the LASIK group. At 1 year, 97% of eyes in the PRK group and 94% of eyes in the LASIK group achieved an UCVA of 20/20 or better (P=0.72). Refractive stability was achieved in both PRK and LASIK groups after 1 month. There were no intraoperative or postoperative flap complications in the LASIK group. There were no instances of corneal haze in the PRK group. Wavefront-guided LASIK and PRK are safe and effective at reducing myopia. At 1 month postoperatively, LASIK demonstrates an advantage over PRK in UCVA, BSCVA, low-contrast acuity, induction of total HOAs, and several subjective symptoms. At postoperative month 3, these differences between PRK and LASIK results had resolved.

Wavefront-Guided Laser in Situ Keratomileusis (Lasik) versus Wavefront-Guided Photorefractive Keratectomy (Prk): A Prospective Randomized Eye-to-Eye Comparison (An American Ophthalmological Society Thesis)

PubMed Central

Manche, Edward E.; Haw, Weldon W.

2011-01-01

Purpose To compare the safety and efficacy of wavefront-guided laser in situ keratomileusis (LASIK) vs photorefractive keratectomy (PRK) in a prospective randomized clinical trial. Methods A cohort of 68 eyes of 34 patients with −0.75 to −8.13 diopters (D) of myopia (spherical equivalent) were randomized to receive either wavefront-guided PRK or LASIK in the fellow eye using the VISX CustomVue laser. Patients were evaluated at 1 day, 1 week, and months 1, 3, 6, and 12. Results At 1 month, uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BSCVA), 5% and 25% contrast sensitivity, induction of higher-order aberrations (HOAs), and subjective symptoms of vision clarity, vision fluctuation, ghosting, and overall self-assessment of vision were worse (P<0.05) in the PRK group. By 3 months, these differences had resolved (P>0.05). At 1 year, mean spherical equivalent was reduced 94% to −0.27 ± 0.31 D in the LASIK group and reduced 96% to −0.17 ± 0.41 D in the PRK group. At 1 year, 91% of eyes were within ±0.50 D and 97 % were within ±1.0 D in the PRK group. At 1 year, 88% of eyes were within ±0.50 D and 97% were within ±1.0 D in the LASIK group. At 1 year, 97% of eyes in the PRK group and 94% of eyes in the LASIK group achieved an UCVA of 20/20 or better (P=0.72). Refractive stability was achieved in both PRK and LASIK groups after 1 month. There were no intraoperative or postoperative flap complications in the LASIK group. There were no instances of corneal haze in the PRK group. Conclusions Wavefront-guided LASIK and PRK are safe and effective at reducing myopia. At 1 month postoperatively, LASIK demonstrates an advantage over PRK in UCVA, BSCVA, low-contrast acuity, induction of total HOAs, and several subjective symptoms. At postoperative month 3, these differences between PRK and LASIK results had resolved. PMID:22253488

In vivo laser confocal microscopic analysis of corneal K-structures after keratorefractive surgery (LASIK and epi-LASIK).

PubMed

Yokogawa, Hideaki; Kobayashi, Akira; Tagawa, Kosaku; Sugiyama, Kazuhisa

2010-01-01

To demonstrate alterations of corneal K-structures (sub-Bowman's fibrous structures) after keratorefractive surgery by in vivo laser confocal microscopy and to look for association of K-structures with fluorescein-stained anterior corneal mosaic (ACM). Five patients (nine eyes) participated in this study. For four patients, one eye was evaluated after laser in situ keratomileusis (LASIK) and the other after epipolis-laser in situ keratomileusis (epi-LASIK). For one patient, the left eye was evaluated after epithelial debridement. A photograph of the ACM was obtained. Central corneal regions were scanned by Heidelberg Retina Tomograph 2 Rostock Cornea Module (Heidelberg Engineering GmbH, Heidelberg, Germany). The ACM and K-structures disappeared in all corneas after epi-LASIK, but not after LASIK and epithelial debridement cornea. The presence of K-structures and ACM may be an index to identify eyes that had a previous refractive surgical procedure (surface ablation or LASIK) and be a health index of Bowman layer and adjacent anterior stroma. Copyright 2010, SLACK Incorporated.

Visual Outcomes, Quality of Vision, and Quality of Life of Diffractive Multifocal Intraocular Lens Implantation after Myopic Laser In Situ Keratomileusis: A Prospective, Observational Case Series

PubMed Central

2017-01-01

Purpose. To report visual performance and quality of life after implantation of a bifocal diffractive multifocal intraocular lens (MIOL) in postmyopic laser in situ keratomileusis (LASIK) patients. Methods. Prospective, observational case series. Patients with prior myopic LASIK who had implantation of Tecnis ZMA00/ZMB00 MIOL (Abbott Medical Optics) at Hong Kong Sanatorium and Hospital were included. Postoperative examinations included monocular and binocular distance, intermediate and near visual acuity (VA), and contrast sensitivity; visual symptoms (0–5); satisfaction (1–5); spectacle independence rate; and quality of life. Results. Twenty-three patients (27 eyes) were included. No intraoperative complications developed. Mean monocular uncorrected VA at distance, intermediate, and near were 0.13 ± 0.15 (standard deviation), 0.22 ± 0.15, and 0.16 ± 0.15, respectively. Corresponding mean values for binocular uncorrected VA were 0.00 ± 0.10, 0.08 ± 0.13, and 0.13 ± 0.10, respectively. No eyes lost >1 line of corrected distance VA. Contrast sensitivity at different spatial frequencies between operated and unoperated eyes did not differ significantly (all P > 0.05). Mean score for halos, night glare, starbursts, and satisfaction were 1.46 ± 1.62, 1.85 ± 1.69, 0.78 ± 1.31, and 3.50 ± 1.02, respectively. Eighteen patients (78%) reported complete spectacle independence. Mean composite score of the quality-of-life questionnaire was 90.31 ± 8.50 out of 100. Conclusions. Implantation of the MIOL after myopic LASIK was safe and achieved good visual performance. PMID:28133543

Visual Outcomes, Quality of Vision, and Quality of Life of Diffractive Multifocal Intraocular Lens Implantation after Myopic Laser In Situ Keratomileusis: A Prospective, Observational Case Series.

PubMed

Chang, John S M; Ng, Jack C M; Chan, Vincent K C; Law, Antony K P

2017-01-01

Purpose . To report visual performance and quality of life after implantation of a bifocal diffractive multifocal intraocular lens (MIOL) in postmyopic laser in situ keratomileusis (LASIK) patients. Methods . Prospective, observational case series. Patients with prior myopic LASIK who had implantation of Tecnis ZMA00/ZMB00 MIOL (Abbott Medical Optics) at Hong Kong Sanatorium and Hospital were included. Postoperative examinations included monocular and binocular distance, intermediate and near visual acuity (VA), and contrast sensitivity; visual symptoms (0-5); satisfaction (1-5); spectacle independence rate; and quality of life. Results . Twenty-three patients (27 eyes) were included. No intraoperative complications developed. Mean monocular uncorrected VA at distance, intermediate, and near were 0.13 ± 0.15 (standard deviation), 0.22 ± 0.15, and 0.16 ± 0.15, respectively. Corresponding mean values for binocular uncorrected VA were 0.00 ± 0.10, 0.08 ± 0.13, and 0.13 ± 0.10, respectively. No eyes lost >1 line of corrected distance VA. Contrast sensitivity at different spatial frequencies between operated and unoperated eyes did not differ significantly (all P > 0.05). Mean score for halos, night glare, starbursts, and satisfaction were 1.46 ± 1.62, 1.85 ± 1.69, 0.78 ± 1.31, and 3.50 ± 1.02, respectively. Eighteen patients (78%) reported complete spectacle independence. Mean composite score of the quality-of-life questionnaire was 90.31 ± 8.50 out of 100. Conclusions . Implantation of the MIOL after myopic LASIK was safe and achieved good visual performance.

Excimer laser photorefractive surgery of the cornea

NASA Astrophysics Data System (ADS)

Gaster, Ronald N.

1998-09-01

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

[Comparison of the effects of different side-cut angles on corneal biomechanical properties after femtosecond laser assisted-laser in situ keratomileusis].

PubMed

Li, H; Wang, Y; Dou, R; Wang, L; Xu, L L; Li, X J; Zhang, J M

2017-01-11

Objective: To evaluate the effects of side-cut angles on corneal biomechanical properties after femtosecond laser assisted-laser in situ keratomileusis (FS-LASIK). Methods: In this clinical control study, 97 right eyes of 97 patients with myopia and myopic astigmatism undergoing FS-LASIK surgery were included randomly. Two types of side-cut angles were designed for the flap, 90° in 48 eyes and 130° in 49 eyes. The values of corneal resistance factor (CRF), cornea hysteresis (CH) and 37 biomechanical waveform parameters were measured using the ocular response analyzer preoperatively and at 1 and 3 months postoperatively. The comparison between the two groups at different follow-up time points was made with one-way analysis of variance, and the comparison among different follow-up time points in each group was performed with the repeated measures analysis of variance. Results: The mean CRF, CH, p area, h, dive1, dive2, w11 and w21 in both groups showed significant reduction at 1 month postoperatively (group 90°: CRF 10.49 vs. 6.85, CH 10.02 vs. 7.55, p1 area 3 537.54 vs. 1 918.07, h1 404.74 vs. 283.25, dive1 350.63 vs. 243.33, w11 10.50 vs. 7.58. group 130°: CRF 10.14 vs. 6.38, CH 9.93 vs. 7.13, p1 area 3 498.93 vs. 2 038.74, h1 411.93 vs. 304.49, dive1 352.51 vs. 265.12, w11 10.55 vs. 7.78. P< 0.001) . The mean CRF, CH, p area, w, h, dive1 and dive2 in both groups showed significant reduction at 3 months postoperatively (group 90°: CRF 10.49 vs. 6.60, CH 10.02 vs. 7.65, p1 area 3537.54 vs. 2042.91, h1 404.74 vs. 307.77, dive1 350.63 vs. 263.33, w11 10.50 vs. 7.58. group 130°: CRF 10.14 vs. 6.45, CH 9.93 vs. 7.67, p1 area 3 498.93 vs. 2 187.97, h1 411.93 vs. 327.39, dive1 352.51 vs. 284.26, w11 10.55 vs. 7.61. P< 0.001). The mean path in both groups showed significant increase at 1 and 3 months postoperatively (group 90°: path1 23.14 vs. 30.50 vs. 30.79. group 130°: path1 24.12 vs. 32.18 vs. 31.49. P< 0.001). The mean aplhf, bindex, dive2 and path2 between

A retrospective analysis of the postoperative use of loteprednol etabonate gel 0.5% following laser-assisted in situ keratomileusis or photorefractive keratectomy surgery.

PubMed

Salinger, Clifford L; Gordon, Michael; Jackson, Mitchell A; Perl, Theodore; Donnenfeld, Eric

2015-01-01

While loteprednol etabonate ophthalmic gel 0.5% (LE gel) is approved for treatment of postoperative ocular inflammation and pain, there have been no reported studies in patients undergoing laser-assisted in situ keratomileusis (LASIK) or photorefractive keratectomy (PRK). This was a retrospective chart review conducted at five refractive surgical centers in the USA. Data were collected from primary LASIK or PRK surgery cases in which LE gel was used postoperatively as the clinician's routine standard of care and in which patients were followed-up for up to 6 months. Data extracted from charts included patient demographics, surgical details, LE gel dosing regimen, pre- and postsurgical refractive characteristics, intraocular pressure (IOP) measurements, and visual acuity. Primary outcomes included postoperative IOP elevations, adverse events, and early discontinuations. Data were collected on 189 LASIK eyes (96 patients) and 209 PRK eyes (108 patients). Mean (standard deviation [SD]) years of age at surgery was 36.0 (11.7) and 33.9 (11.3) in LASIK and PRK patients. LE gel was prescribed most often four times daily during the first postoperative week, regardless of procedure; the most common treatment duration was 7-14 days in LASIK and ≥30 days in PRK patients. No unusual corneal findings or healing abnormalities were reported. Mean postoperative uncorrected distance visual acuity was 20/24 in LASIK and 20/30 in PRK eyes. Mild/trace corneal haze was reported in 20% of PRK patients; two PRK patients with moderate/severe corneal haze were switched to another corticosteroid. Mean postoperative IOP did not increase over time in either LASIK or PRK eyes (P≥0.331); clinically significant elevations from baseline in IOP (≥10 mmHg) were noted in only three eyes of two PRK patients. LE gel appears to have a high level of safety and tolerability when used for the management of postoperative pain and inflammation following LASIK and PRK surgery.

A retrospective analysis of the postoperative use of loteprednol etabonate gel 0.5% following laser-assisted in situ keratomileusis or photorefractive keratectomy surgery

PubMed Central

Salinger, Clifford L; Gordon, Michael; Jackson, Mitchell A; Perl, Theodore; Donnenfeld, Eric

2015-01-01

Background While loteprednol etabonate ophthalmic gel 0.5% (LE gel) is approved for treatment of postoperative ocular inflammation and pain, there have been no reported studies in patients undergoing laser-assisted in situ keratomileusis (LASIK) or photorefractive keratectomy (PRK). Methods This was a retrospective chart review conducted at five refractive surgical centers in the USA. Data were collected from primary LASIK or PRK surgery cases in which LE gel was used postoperatively as the clinician’s routine standard of care and in which patients were followed-up for up to 6 months. Data extracted from charts included patient demographics, surgical details, LE gel dosing regimen, pre- and postsurgical refractive characteristics, intraocular pressure (IOP) measurements, and visual acuity. Primary outcomes included postoperative IOP elevations, adverse events, and early discontinuations. Results Data were collected on 189 LASIK eyes (96 patients) and 209 PRK eyes (108 patients). Mean (standard deviation [SD]) years of age at surgery was 36.0 (11.7) and 33.9 (11.3) in LASIK and PRK patients. LE gel was prescribed most often four times daily during the first postoperative week, regardless of procedure; the most common treatment duration was 7–14 days in LASIK and ≥30 days in PRK patients. No unusual corneal findings or healing abnormalities were reported. Mean postoperative uncorrected distance visual acuity was 20/24 in LASIK and 20/30 in PRK eyes. Mild/trace corneal haze was reported in 20% of PRK patients; two PRK patients with moderate/severe corneal haze were switched to another corticosteroid. Mean postoperative IOP did not increase over time in either LASIK or PRK eyes (P≥0.331); clinically significant elevations from baseline in IOP (≥10 mmHg) were noted in only three eyes of two PRK patients. Conclusion LE gel appears to have a high level of safety and tolerability when used for the management of postoperative pain and inflammation following LASIK

Symptoms and Satisfaction of Patients in the Patient-Reported Outcomes With Laser In Situ Keratomileusis (PROWL) Studies.

PubMed

Eydelman, Malvina; Hilmantel, Gene; Tarver, Michelle E; Hofmeister, Elizabeth M; May, Jeanine; Hammel, Keri; Hays, Ron D; Ferris, Frederick

2017-01-01

Patient-reported outcomes should be collected using validated questionnaires prior to and following laser in situ keratomileusis (LASIK) surgery. To report the frequency of patient-reported visual symptoms, dry eye symptoms, satisfaction with vision, and satisfaction with LASIK surgery in the Patient-Reported Outcomes With LASIK (PROWL) studies. The PROWL-1 and PROWL-2 studies were prospective, observational studies conducted from September 13, 2011, to June 27, 2014. The PROWL-1 study was a single-military center study of 262 active-duty Navy personnel 21 to 52 years of age. The PROWL-2 study was a study of 312 civilians 21 to 57 years of age conducted at 5 private practice and academic centers. The LASIK surgery and the postoperative care were performed based on the usual practice and clinical judgment at the site. Participants completed a self-administered, web-based questionnaire, preoperatively and postoperatively at 1 and 3 months (the PROWL-1 and -2 studies) and at 6 months (the PROWL-2 study). Participants underwent LASIK surgery for myopia, hyperopia, and/or astigmatism. Visual symptoms (double images, glare, halos, and/or starbursts), dry eye symptoms, participant satisfaction (with vision and LASIK surgery), and clinical measures (visual acuity, refractive error, and slitlamp and posterior segment eye examination findings) were assessed preoperatively and at 1, 3, and 6 months postoperatively. A total of 262 participants were enrolled in the PROWL-1 study (mean [SD] age, 29.1 [6.1] years), and a total of 312 participants were enrolled in the PROWL-2 study (mean [SD] age, 31.5 [7.3] years). Visual symptoms and dissatisfaction with vision were common preoperatively. Overall, the prevalence of visual symptoms and dry eye symptoms decreased, although a substantial percentage of participants reported new visual symptoms after surgery (43% [95% CI, 31%-55%] from the PROWL-1 study and 46% [95% CI, 33%-58%] from the PROWL-2 study at 3 months). The percentages of

Publications and Presentations of the Ophthalmology Branch, U.S. Air Force School of Aerospace Medicine, 2006-2010

DTIC Science & Technology

2013-12-01

LASER ASSISTED IN SITU KERATOMILEUSIS ( LASIK ) EYES Aaron MT, Gooch JM, Harvey RR, Davis RE, and Tutt RC Abstract: Aviation, Space, and Environmental...AZ; 9-13 May 2010 10. EFFECT OF HIGH ALTITUDE ON LASER ASSISTED IN SITU KERATOMILEUSIS ( LASIK ) EYES Aaron MT, Gooch JM, Harvey RR, Davis RE, and

Clinical outcomes of laser in situ keratomileusis with an aberration-neutral profile centered on the corneal vertex comparing vector planning with manifest refraction planning for the treatment of myopic astigmatism.

PubMed

Arbelaez, Maria Clara; Alpins, Noel; Verma, Shwetabh; Stamatelatos, George; Arbelaez, Juan Guillermo; Arba-Mosquera, Samuel

2017-12-01

To evaluate clinical outcomes of laser in situ keratomileusis (LASIK) with an aberration-neutral profile centered on the estimated visual axis (considering 70% of the pupil offset toward the corneal vertex) comparing vector planning with manifest refraction planning for the treatment of myopic astigmatism. Muscat Eye Laser Center, Muscat, Sultanate of Oman, Muscat, Oman. Retrospective case series. The outcomes were evaluated at a 6-month follow-up in eyes showing ocular residual astigmatism (ORA) over 0.75 diopters (D) preoperatively. Eighty-five treatments were based on manifest astigmatism (preoperative sphere -2.11 D ± 1.3 [SD], cylinder -0.90 ± 1.0 D), and 79 treatments were based on vector planning (preoperative sphere -2.46 ± 1.5 D, cylinder -0.78 ± 0.79 D). At a 6-month follow-up, 128 patients (164 eyes) were evaluated and no significant differences were observed between the 2 groups in terms of difference between corrected distance visual acuity and uncorrected distance visual acuity (UDVA) (P = .1, t test and Fisher exact test Snellen lines 1 or better, P = .4) and postoperative UDVA (P = .05, t test and Fisher exact test for UDVA 20/16 or better, P = .3). Significant differences were observed between the 2 groups in terms of achieved spherical equivalent (P = .04), corneal toricity, and ORA (P < .001, t test and Fisher exact test for ORA ≤0.75 D, P < .001). Performing LASIK for myopic astigmatism with the vector planning approach resulted in comparable visual outcomes to manifest refraction planning. Copyright © 2017 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.

New Refractive Surgery Procedures and Their Implications for Aviation Safety

DTIC Science & Technology

2006-04-01

airmen with laser refractive surgery, i.e., photorefractive keratectomy ( PRK ) and laser in situ keratomileusis ( LASIK ). A reference guide on refractive...surgery was published in September of 1998 (DOT/FAA/AM-98/25); however, at that time long-term clinical data on PRK and LASIK were not available...fractive surgery procedures (Photorefractive Keratectomy [ PRK ], Laser1 in situ Keratomileusis [ LASIK ]) and to assist Aviation Medical Examiners in

Comparison of the predictability of refractive cylinder correction by laser in situ keratomileusis in eyes with low or high ocular residual astigmatism.

PubMed

Archer, Timothy J; Reinstein, Dan Z; Piñero, David P; Gobbe, Marine; Carp, Glenn I

2015-07-01

To compare the manifest refractive cylinder (MRC) predictability of myopic astigmatism laser in situ keratomileusis (LASIK) between eyes with low and high ocular residual astigmatism (ORA). London Vision Clinic, London, United Kingdom. Retrospective case study. The ORA was considered the vector difference between the MRC and the corneal astigmatism. The index of success (IoS), difference vector ÷ MRC, was analyzed for different groups as follows: stage 1, low ORA (ORA ÷ MRC <1), high ORA (ORA ÷ MRC ≥1); stage 2, low ORA group reduced to match the high ORA group for MRC; stage 3, grouped by ORA magnitude with low ORA (<0.50 diopters [D]), mid ORA (0.50 to 1.24 D), and high ORA (≥1.25 D); stage 4, high ORA group subdivided into low (<0.75 D) and high (≥0.75 D) corneal astigmatism. For stage 1, the mean preoperative MRC and mean IoS were -1.32 D ± 0.65 (SD) (range -0.55 to -3.77 D) and 0.27, respectively, for low ORA and -0.79 ± 0.20 D (range -0.56 to -2.05 D) and 0.37, respectively, for high ORA. For stage 2, the mean IoS increased to 0.32 for low ORA. For stage 3, the mean IoS was 0.28, 0.29, and 0.31 for low ORA, mid ORA, and high ORA, respectively. For stage 4, the mean IoS was 0.20 for high ORA/low corneal astigmatism and 0.35 for high ORA/high corneal astigmatism. The MRC predictability was slightly worse in eyes with high ORA when grouped by the ORA ÷ MRC. Matching for the MRC and grouping by ORA magnitude resulted in similar predictability; however, eyes with high ORA and high corneal astigmatism were less predictable. Dr. Reinstein is a consultant to Carl Zeiss Meditec AG, has a proprietary interest in the Artemis technology (Arcscan, Inc.), and is an author of patents related to very-high-frequency digital ultrasound administered by the Center for Technology Licensing at Cornell University, Ithaca, New York, USA. No other author has a financial or proprietary interest in any material or method mentioned. Copyright © 2015 ASCRS and ESCRS

Corneal subbasal nerve fiber regeneration in myopic patients after laser in situ keratomileusis★

PubMed Central

Deng, Shijing; Wang, Mengmeng; Zhang, Fengju; Sun, Xuguang; Hou, Wenbo; Guo, Ning

2012-01-01

A total of 26 myopic patients (52 eyes) underwent laser in situ keratomileusis. In vivo confocal microscopy revealed that most of the regenerated corneal subbasal nerve fibers in the corneal flap originated from the stump of corneal subbasal nerve fibers outside the ablation zone and extended towards the center of the cornea in all patients. Meanwhile, new fibers were also found to directly regenerate from deep in the stroma in some cases. Approximately 94% of regenerated corneal subbasal nerve fibers (73/78 eyes) regrew vertically into the peripheral central 6-mm circle area 1 month after surgery, 78% (28/36 eyes) grew into the central 3–6 mm area at 2 months, and 23% into the central 3-mm circle area at 3 months. In addition, there was no significant difference in corneal subbasal nerve fiber regenerative capacity between the basic fibroblast growth factor group and the 20% (v/v) deproteinized extract of calf blood group. The majority of corneal subbasal nerve fiber regeneration occurred from the stump of corneal subbasal nerve fibers outside the corneal flap, and the remaining growth occurred deep within the stroma. PMID:25657693

[Study on the change of optical zone after femtosecond laser assisted laser in situ keratomileusis].

PubMed

Li, H; Chen, M; Tian, L; Li, D W; Peng, Y S; Zhang, F F

2018-01-11

Objective: To explore the change of optical zone after femtosecond laser assisted laser in sitn keratomileusis(FS-LASIK) so as to provide the reference for measurement and design of clinical optical zone. Methods: This retrospective case series study covers 41 eyes of 24 patients (7 males and 17 females, aged from 18 to 42 years old) with myopia and myopic astigmatism who have received FS-LASIK surgery at Corneal Refractive Department of Qingdao Eye Hospital and completed over 6 months of clinical follow-up. Pentacam system (with the application of 6 corneal topographic map modes including: the pure axial curvature topographic map, the pure tangential curvature topographic map, the axial curvature difference topographic map, the tangential curvature difference topographic map, the postoperative front elevation map and the corneal thickness difference topographic map), combined with transparent concentric software (a system independently developed by Qingdao Eye Hospital) was used to measure the optical zone at 1, 3 and 6 months postoperatively, the optical zone diameters measurement results among different follow-up times in group were analyzed with the repeated measures analysis of variance, and the actual measured values and the theoretical design values of the optical zone were analyzed with independent-samples t-testing. Spearman correlation coefficient ( r(s) ) have been applied to evaluate the relationship between postoperative optical zone measurement values and the potential influencing factors. Results: The optical zone diameters measured by pure axial curvature topographic map at 1, 3 and 6 months after FS-LASIK showed (6.55±0.50)mm, (6.50±0.53)mm and (6.48±0.53)mm respectively. The differences between values are of no statistical significance ( F= 1.60, P= 0.21), the optical zone diameter measured by pure tangential curvature topographic map at 1, 3 and 6 months after FS-LASIK showed (5.44±0.46)mm, (5.46±0.52)mm and (5.44±0.50)mm respectively, the

Small Incision Lenticule Extraction (SMILE) versus Femtosecond Laser-Assisted In Situ Keratomileusis (FS-LASIK) for Myopia: A Systematic Review and Meta-Analysis

PubMed Central

Shen, Zeren; Shi, Keda; Yu, Yinhui; Yu, Xiaoning; Lin, Yuchen; Yao, Ke

2016-01-01

Purpose The goal of this study was to compare small incision lenticule extraction (SMILE) with femtosecond laser-assisted in situ keratomileusis (FS-LASIK) for treating myopia. Methods The CENTRAL, EMBASE, PubMed databases and a Chinese database (SinoMed) were searched in May of 2016. Twelve studies with 1,076 eyes, which included three randomized controlled trials (RCTs) and nine cohorts, met our inclusion criteria. The overall quality of evidence was evaluated using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) working group framework. Data were extracted and analysed at three to six months postoperatively. Primary outcome measures included a loss of one or more lines of best spectacle corrected visual acuity (BSCVA), uncorrected visual acuity (UCVA) of 20/20 or better, mean logMAR UCVA, postoperative mean spherical equivalent (SE) and postoperative refraction within ±1.0 D of the target refraction. Secondary outcome measures included ocular surface disease index (OSDI), tear breakup time (TBUT) and Schirmer’s 1 test (S1T) as dry eye parameters, along with corneal sensitivity. Results The overall quality of evidence was considered to be low to very low. Pooled results revealed no significant differences between the two groups with regard to a loss of one or more lines in the BSCVA (OR 1.71; 95% CI: 0.81, 3.63; P = 0.16), UCVA of 20/20 or better (OR 0.71; 95% CI: 0.44, 1.15; P = 0.16), logMAR UCVA (MD 0.00; 95% CI: -0.03, 0.04; P = 0.87), postoperative refractive SE (MD -0.00; 95% CI: -0.05, 0.05; P = 0.97) or postoperative refraction within ±1.0 D of the target refraction (OR 0.78; 95% CI: 0.22, 2.77; P = 0.70) within six months postoperatively. The pooled analysis also indicated that the FS-LASIK group suffered more severely from dry eye symptoms (OSDI; MD -6.68; 95% CI: -11.76, -2.00; P = 0.006) and lower corneal sensitivity (MD 12.40; 95% CI: 10.23, 14.56; P < 0.00001) at six months postoperatively. Conclusions In conclusion

Levels of the Novel Glycoprotein Lacritin in Human Tears After Laser Refractive Surgery

DTIC Science & Technology

2012-10-01

and HPSE before and after surgery as well as comparison of responses between procedures ( PRK vs . LASIK ). The primary outcome measure is tear lacritin...patients undergoing PRK (photorefractive keratectomy) and LASIK (Laser-assisted in situ keratomileusis) with the possibility of the development of...recombinant lacritin as a novel therapeutic agent for wound healing. Up to 196 patients eligible to undergo PRK or LASIK at the U.S. Army Warfighter

Assessment of the Psychometric Properties of a Questionnaire Assessing Patient-Reported Outcomes With Laser In Situ Keratomileusis (PROWL).

PubMed

Hays, Ron D; Tarver, Michelle E; Spritzer, Karen L; Reise, Steve; Hilmantel, Gene; Hofmeister, Elizabeth M; Hammel, Keri; May, Jeanine; Ferris, Frederick; Eydelman, Malvina

2017-01-01

Patient-reported outcome (PRO) measures for laser in situ keratomileusis (LASIK) are needed. To develop PRO measures to assess satisfaction, eye-related symptoms, and their effect on functioning and well-being following LASIK based on patient and expert input. The Patient-Reported Outcomes With LASIK (PROWL) studies were prospective observational studies of patients undergoing LASIK surgery for myopia, hyperopia, or astigmatism. PROWL-1 was a single-center study of active-duty US Navy personnel and PROWL-2 was a 5-center study of civilians. PROWL-1 enrolled 262 active-duty service personnel and PROWL-2 enrolled 312 civilians 21 years or older who spoke English; 241 individuals in PROWL-1 and 280 in PROWL-2 completed a baseline questionnaire before surgery. The analytic sample included those also completing 1 or more follow-up questionnaires: 240 (99.6%) of those in PROWL-1 and 271 (94.4%) of those in PROWL-2. Questionnaires were self-administered through the internet preoperatively and at 1 and 3 months postoperatively in both studies and at 6 months postoperatively in PROWL-1. PROWL-1 began in August 2011 and was completed May 30, 2014; PROWL-2 began in July 2012 and was completed June 27, 2014. Data were analyzed from June 28, 2014, to October 24, 2016. Scales assessing visual symptoms (double images, glare, halos, and starbursts), dry eye symptoms, satisfaction with vision, and satisfaction with LASIK surgery. Items from the National Eye Institute (NEI) Refractive Error Quality of Life Instrument (NEI-RQL-42), NEI Visual Function Questionnaire (NEI-VFQ), and the Ocular Surface Disease Index (OSDI) were included. All scales are scored on a 0 to 100 possible range. Construct validity and responsiveness to change were evaluated (comparing scores before and after surgery). The median age of the 240-person PROWL-1 analytic sample was 27 years (range, 21-52 years); 49 were women (20.4%). The median age of the 271-person PROWL-2 analytic sample was 30 years (range, 21

Laser Refractive Surgery

NASA Astrophysics Data System (ADS)

Wynne, James

Refractive surgery has its roots in corneal transplant surgery, first performed in 1905, where the damaged or diseased cornea of a living individual is replaced by donated corneal tissue taken from a recently deceased individual. Since the cornea has no blood supply, there is no danger of organ rejection. Recognizing the exceptional healing power of corneal tissue, ophthalmologists began to explore methods of reshaping the cornea to improve the visual acuity of patients suffering from myopia, hyperopia, and astigmatism. In 1964, a procedure known as keratomileusis was introduced. In 1974, radial keratotomy (RK) was introduced. In 1981, excimer laser surgery was discovered by the speaker and his IBM Research colleagues. In 1983, the excimer laser was used to create clean, precise incisions in the cornea of enucleated calf eyes, derived from slaughter, launching the era of laser refractive surgery, with more precise and safer techniques to correct myopia, hyperopia, and stigmatism. This talk will describe the widely practiced surgical procedures known as photorefractive keratectomy (PRK) and laser-assisted in situ keratomileusis (LASIK), which have improved the visual acuity of more than 35 million people. Most patients undergoing PRK or LASIK end up with uncorrected vision better than 20/20. In 2007, development commenced on a new procedure known as small incision lenticule extraction (SMILE), employing a femtosecond laser and no excimer laser. SMILE is promoted as minimally invasive and combining the advantages of PRK and LASIK. However, long term stability of visual acuity following SMILE surgery is yet to be determined.

Femtosecond Lasers and Corneal Surgical Procedures.

PubMed

Marino, Gustavo K; Santhiago, Marcony R; Wilson, Steven E

2017-01-01

Our purpose is to present a broad review about the principles, early history, evolution, applications, and complications of femtosecond lasers used in refractive and nonrefractive corneal surgical procedures. Femtosecond laser technology added not only safety, precision, and reproducibility to established corneal surgical procedures such as laser in situ keratomileusis (LASIK) and astigmatic keratotomy, but it also introduced new promising concepts such as the intrastromal lenticule procedures with refractive lenticule extraction (ReLEx). Over time, the refinements in laser optics and the overall design of femtosecond laser platforms led to it becoming an essential tool for corneal surgeons. In conclusion, femtosecond laser is a heavily utilized tool in refractive and nonrefractive corneal surgical procedures, and further technological advances are likely to expand its applications. Copyright 2017 Asia-Pacific Academy of Ophthalmology.

Finite element model of the temperature increase in excised porcine cadaver iris during direct illumination by femtosecond laser pulses

PubMed Central

Sun, Hui; Kurtz, Ronald M.

2012-01-01

Abstract. In order to model the thermal effect of laser exposure of the iris during laser corneal surgery, we simulated the temperature increase in porcine cadaver iris. The simulation data for the 60 kHz FS60 Laser showed that the temperature increased up to 1.23°C and 2.45°C (at laser pulse energy 1 and 2 µJ, respectively) by the 24 second procedure time. Calculated temperature profiles show good agreement with data obtained from ex vivo experiments using porcine cadaver iris. Simulation results of different types of femtosecond lasers indicate that the Laser in situ keratomileusis procedure does not present a safety hazard to the iris. PMID:22894525

Simulation of the temperature increase in human cadaver retina during direct illumination by 150-kHz femtosecond laser pulses

PubMed Central

Sun, Hui; Hosszufalusi, Nora; Mikula, Eric R.; Juhasz, Tibor

2011-01-01

We have developed a two-dimensional computer model to predict the temperature increase of the retina during femtosecond corneal laser flap cutting. Simulating a typical clinical setting for 150-kHz iFS advanced femtosecond laser (0.8- to 1-μJ laser pulse energy and 15-s procedure time at a laser wavelength of 1053 nm), the temperature increase is 0.2°C. Calculated temperature profiles show good agreement with data obtained from ex vivo experiments using human cadaver retina. Simulation results obtained for different commercial femtosecond lasers indicate that during the laser in situ keratomileusis procedure the temperature increase of the retina is insufficient to induce damage. PMID:22029369

Clinical results of the laser-assisted in situ keratomileusis (LASIK) for myopia

NASA Astrophysics Data System (ADS)

Guo, Hai-ke; Yao, Da-qing; Gui, Lu-ping

1998-11-01

To observe and analyze the refractive and complications of the LASIK for corrections of myopia. With the microlamellar keratoplasty and the excimer laser, LASIK was performed on 194 cases. According to the preoperative spherical equivalent refraction, divide the patients into three groups.

LASIK eye surgery

MedlinePlus

... Assisted In Situ Keratomileusis; Laser vision correction; Nearsightedness - Lasik; Myopia - Lasik ... cornea (curvature) and the length of the eye. LASIK uses an excimer laser (an ultraviolet laser) to ...

Laser in situ keratomileusis enhancements with the Ziemer FEMTO LDV femtosecond laser following previous LASIK treatments.

PubMed

Pietilä, Juhani; Huhtala, Anne; Mäkinen, Petri; Uusitalo, Hannu

2013-02-01

The aim of this paper is to present the accuracy, predictability, and safety outcomes of LASIK enhancements performed with the FEMTO LDV femtosecond laser (Ziemer Ophthalmic Systems, Port, Switzerland) and the Allegretto Wave Concerto 500 Hz excimer laser (Wavelight AG, Erlangen, Germany), following previous LASIK treatments. FEMTO LDV was used for flap creation in 85 previously LASIK-treated eyes of 62 patients. The intended flap thickness was 90 μm in 81 eyes and 140 μm in 4 eyes. The size of the suction ring was 9.0 mm in 72 eyes and 9.5 mm in 13 eyes. Flap dimensions were measured and correlated to preoperative characteristics. With the intended flap thickness of 90 μm in previously LASIK-treated eyes, the actual flap thickness was 90.2 ± 6.6 μm (range 80-122), and the flap diameter was 9.2 ± 0.2 mm (range 8.7-9.9). The mean hinge length was 4.0 ± 0.2 mm (range 3.0-4.8). Flap thickness correlated positively with patient age and hinge length. Complications were reported in 12 eyes (14.1 %). Most of the complications were very mild, and none of them prevented further refractive laser treatment. One eye lost two Snellen lines of best spectacle-corrected visual acuity. Femtosecond LASIK enhancement is warranted only in rare cases. Surgical experience is needed and special caution must be practiced. For cases of a primary free cap, femtosecond LASIK is not recommended.

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.

[Advantages and disadvantages of femtosecond laser assisted LASIK and SMILE].

PubMed

Zhang, F J; Sun, M S

2018-01-11

With the development of excimer laser and femtosecond laser equipment, application of diversified and customized surgical decision in modern corneal refractive surgery has been an inevitable trend. However, how to make a personalized decision with an accurate surgical design to achieve better visual quality becomes the main focus in clinical applications. Small-incision lenticule extraction (SMILE) and femtosecond assisted laser in situ keratomileusis (FS-LASIK) have been commonly acknowledged as the mainstream of corneal refractive surgery for ametropia correction nowadays. Both methods have been verified by clinical practice for many years. This article compares and elaborates the different characteristics with advantages and disadvantages of the two methods so as to provide some reasonable treatment options for refractive surgery. (Chin J Ophthalmol, 2018, 54: 7-10) .

Ten years after photorefractive keratectomy (PRK) and laser in situ keratomileusis (LASIK) for moderate to high myopia (control-matched study).

PubMed

Alió, J L; Ortiz, D; Muftuoglu, O; Garcia, M J

2009-10-01

To compare the long-term outcomes of photorefractive keratectomy (PRK) and laser in situ keratomilesis (LASIK) for myopia between -6 and -10 D. A retrospective, control-matched study including 68 eyes, 34 which underwent PRK and 34 LASIK, with myopia between -6 and -10 D, operated using the VISX 20/20 excimer laser, was performed. Optical zones of 5.5 to 6 mm were used. All PRK-treated eyes were matched with LASIK-treated eyes of the same age, spherical equivalent within +/-1.25 D, sphere within +/-1.5 D and cylinder within +/-2.5 D. All patients were evaluated 3 months, 1 year, 2 years, 5 years and 10 years after surgery. The main outcomes measures were refractive predictability and stability, safety, efficacy and re-treatment rate. At 10 years, 20 (71%) and 23 (88%) were within +/-1.00 D after PRK and LASIK respectively. The re-treatment rate was 35% and 18% respectively. No eye lost more than two lines of BSCVA in both groups. The efficacy was 0.90 for PRK and 0.95 for LASIK. Both PRK and LASIK were safe for moderate myopia. LASIK demonstrated slightly better efficacy, predictability, and less rate of re-treatment after 10 years. The technical improvements should be taken into account when comparing these results with those obtained more recently.

[Comparative results evaluation of residual myopia and astigmatism correction after radial keratotomy by photorefraction keratectomy and laser specialized keratomileusis].

PubMed

Dias-Martines, T E; Sheludchenko, V M; Kurenkov, V V

1999-01-01

The results of correction of residual myopia by photorefraction keratectomy (PRK) (51 eyes) and laser specialized keratomileusis (LASIK) (36 eyes) after radial keratotomy (RK) are compared. The patients were observed for up to 12 months. After PRK, 7.3% patients developed late fleur of the cornea, evaluated by at least 2 points. The incidence of fleur directly depended on the value of residual myopia. After LASIK none of the patients developed such fleur. The best visual acuity (0.5 and higher without correction) was attained in 70.73% after PRK and RK, vs. 100% after LASIK. The results of photorefraction operations and severity of residual myopia after RK correlated. In residual myopia of up to -3 diopters the results of correction by PRK and LASIK were virtually the same. In residual myopia higher than -3 diopters, LASIK is preferable.

A retrospective comparison of efficacy and safety of 680 consecutive lasik treatments for high myopia performed with two generations of flying-spot excimer lasers.

PubMed

Gazieva, Lola; Beer, Mette Hjuler; Nielsen, Kim; Hjortdal, Jesper

2011-12-01

To compare the visual refractive outcome and complication of laser in situ keratomileusis (LASIK) carried out with a Carl Zeiss-Meditec MEL-70 Excimer laser and a MEL-80 laser for treatment of high myopia. Journal records of 680 consecutive eyes that underwent LASIK with a Schwind Supratome microkeratome and a MEL-70 Excimer laser (Group A), or a Moria M2 microkeratome and a MEL-80 Excimer laser (Group B) were reviewed. Manifest refraction, uncorrected and best spectacle-corrected visual acuity (BSCVA), corneal topography and central corneal thickness (CCT) were recorded before and 3 months after treatment. Pre- and postoperative complications, visual and refractive outcome and frequency of retreatments were registered. Mean preoperative spherical equivalent refraction was -8.52 dioptres (-5.50- -18 dioptres), and the mean attempted laser correction was -8.02 dioptres (-5.50- -11 dioptres). Three months after LASIK, the average treatment error (difference between achieved and attempted correction) was 1.20 (SD=1.19) dioptres of under correction in Group A and 0.52 (SD=1.00) dioptres in Group B. Four eyes lost more than two lines of BSCVA (0.6%). In 110 eyes (16%), a re-LASIK procedure was performed to reduce remaining myopia after the primary procedure. Laser in situ keratomileusis treatment for high myopia can effectively reduce high degrees of myopia. Under correction was observed in both treatment groups but Group B has a slightly better predictability. Significant loss of BSCVA occurs infrequently after LASIK for even considerable grades of myopia (0.6% in each group). © 2010 The Authors. Journal compilation © 2010 Acta Ophthalmol.

In-situ laser retorting of oil shale

NASA Technical Reports Server (NTRS)

Bloomfield, H. S. (Inventor)

1977-01-01

Oil shale formations are retorted in situ and gaseous hydrocarbon products are recovered by drilling two or more wells into an oil shale formation underneath the surface of the ground. A high energy laser beam is directed into the well and fractures the region of the shale formation. A compressed gas is forced into the well that supports combustion in the flame front ignited by the laser beam, thereby retorting the oil shale. Gaseous hydrocarbon products which permeate through the fractured region are recovered from one of the wells that were not exposed to the laser system.

In situ TEM Raman spectroscopy and laser-based materials modification.

PubMed

Allen, F I; Kim, E; Andresen, N C; Grigoropoulos, C P; Minor, A M

2017-07-01

We present a modular assembly that enables both in situ Raman spectroscopy and laser-based materials processing to be performed in a transmission electron microscope. The system comprises a lensed Raman probe mounted inside the microscope column in the specimen plane and a custom specimen holder with a vacuum feedthrough for a tapered optical fiber. The Raman probe incorporates both excitation and collection optics, and localized laser processing is performed using pulsed laser light delivered to the specimen via the tapered optical fiber. Precise positioning of the fiber is achieved using a nanomanipulation stage in combination with simultaneous electron-beam imaging of the tip-to-sample distance. Materials modification is monitored in real time by transmission electron microscopy. First results obtained using the assembly are presented for in situ pulsed laser ablation of MoS 2 combined with Raman spectroscopy, complimented by electron-beam diffraction and electron energy-loss spectroscopy. Copyright © 2016 Elsevier B.V. All rights reserved.

In situ probing of pulsed laser melting and laser-induced periodic surface structures formation by dynamic reflectivity

NASA Astrophysics Data System (ADS)

Huynh, T. T. D.; Semmar, N.

2017-09-01

The melting process and nanostructure formation induced by nanosecond and picosecond laser pulses on bulk silicon and copper thin film were studied by ex situ analysis and in situ real time reflectivity. Three different probing wavelengths (633, 473 and 326 nm) were used during the pump laser processing and were correlated to the beam parameters (pulse duration, laser fluence and number of laser shots) and copper thin film thickness. On a silicon surface using a KrF laser beam (27 ns, 1 Hz, 248 nm), the melting threshold was determined close to 700 mJ cm-2 and the melting duration increased from 10 to 130 ns as the fluence increased from 700 to 1750 mJ cm-2. Nanostructures with a spatial period close to the laser wavelength were formed on both copper thin film and silicon substrate after nanosecond Nd:YAG laser (10 ns, 266 nm, 1 Hz) irradiation. In the picosecond regime, using an Nd:YAG laser (40 ps, 266 nm, 1 Hz), different nanostructures, from spikes to laser-induced periodic surface structures, were formed on 500 nm copper thin film and were analyzed with respect to the drop in dynamic reflectivity changes versus the number of laser shots.

Comparison of laser in situ ketatomileusis and photorefractive keratectomy for myopia using a mixed-effects model

PubMed Central

Mori, Yosai; Miyata, Kazunori; Ono, Takashi; Yagi, Yusuke; Kamiya, Kazutaka; Amano, Shiro

2017-01-01

Purpose To compare the results of laser in situ keratomileusis (LASIK) and photorefractive keratectomy (PRK) for myopia using a mixed-effects model. Methods This comparative retrospective study was conducted in 1,127 eyes of 579 patients after LASIK and 270 eyes of 144 patients after PRK who had two or more postoperative follow-ups after 3 months. Uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BSCVA), manifest refractive spherical equivalent (MRSE), percentage of eyes within ± 0.5 diopters (D) and ± 1.0 D of targeted refraction, and central corneal thickness were compared between PRK and LASIK groups using a mixed-effects model. Results Compared with the LASIK group, UCVA in the PRK group was significantly worse in the initial year but was significantly better after 4 years. The average BSCVA was not significantly different between the LASIK and PRK groups after 4 years. The average gain of BSCVA in the PRK group was significantly larger than that of the LASIK group after 2 years. MRSE in the LASIK and PRK groups showed a gradual myopic shift until 6 years after surgery. After 6 years, MRSE in the PRK group remained stable whereas MRSE in the LASIK group continued a myopic shift. The percentages of eyes within ± 0.5 D or ± 1.0 D in the LASIK group were significantly higher than those in the PRK group at 3 months but were significantly lower than those in the PRK group at 10 years. Conclusions PRK for myopia shows better efficacy than LASIK for myopia after 4 years. PMID:28362808

Femtosecond all-solid-state laser for refractive surgery

NASA Astrophysics Data System (ADS)

Zickler, Leander; Han, Meng; Giese, G.'nter; Loesel, Frieder H.; Bille, Josef F.

2003-06-01

Refractive surgery in the pursuit of perfect vision (e.g. 20/10) requires firstly an exact measurement of abberations induced by the eye and then a sophisticated surgical approach. A recent extension of wavefront measurement techniques and adaptive optics to ophthalmology has quantitatively characterized the quality of the human eye. The next milestone towards perfect vision is developing a more efficient and precise laser scalpel and evaluating minimal-invasive laser surgery strategies. Femtosecond all-solid-state MOPA lasers based on passive modelocking and chirped pulse amplification are excellent candidates for eye surgery due to their stability, ultra-high intensity and compact tabletop size. Furthermore, taking into account the peak emission in the near IR and diffraction limited focusing abilities, surgical laser systems performing precise intrastromal incisions for corneal flap resection and intrastromal corneal reshaping promise significant improvement over today's Photorefractive Keratectomy (PRK) and Laser Assisted In Situ Keratomileusis (LASIK) techniques which utilize UV excimer lasers. Through dispersion control and optimized regenerative amplification, a compact femtosecond all-solid-state laser with pulsed energy well above LIOB threshold and kHz repetition rate is constructed. After applying a pulse sequence to the eye, the modified corneal morphology is investigated by high resolution microscopy (Multi Photon/SHG Confocal Microscope).

Optimization of the parameters for intrastromal refractive surgery with ultrashort laser pulses

NASA Astrophysics Data System (ADS)

Heisterkamp, Alexander; Ripken, Tammo; Lubatschowski, Holger; Welling, Herbert; Dommer, Wolfgang; Luetkefels, Elke; Mamom, Thanongsak; Ertmer, Wolfgang

2001-06-01

Focussing femtosecond laser pulses into a transparent media, such as corneal tissue, leads to optical breakdown, generation of a micro-plasma and, thus, a cutting effect inside the tissue. To proof the potential of fs-lasers in refractive surgery, three-dimensional cutting within the corneal stroma was evaluated. With the use of ultrashort laser pulses within the LASIK procedure (laser in situ keratomileusis) possible complications in handling of a mechanical knife, the microkeratome, can be reduced by using the treatment laser as the keratome itself. To study woundhealing effects, animal studies were carried out in rabbit specimen. The surgical outcome was analyzed by means of histological sections, as well as light and scanning electron microscopy. Dependencies on the dispersion caused by focussing optics were evaluated and optimized. Thus, pulse energies well below 1 (mu) J were sufficient to perform the intrastromal cuts. The laser pulses with a duration of 180 fs and energies of 0.5-100 (mu) J were provided by a modelocked frequency doubled erbium fiber-laser with subsequent chirped pulse amplification in a titanium sapphire amplifier at up to 3 kHz.

Evaluation of thermal load during laser corneal refractive surgery using infrared thermography

NASA Astrophysics Data System (ADS)

Brunsmann, U.; Sauer, U.; Arba-Mosquera, S.; Magnago, T.; Triefenbach, N.

2010-09-01

Infrared thermography is used for evaluation of the mean temperature as a measure of thermal load during corneal refractive surgery. An experimental method to determine emissivity and to calibrate the thermografic system is presented. In a case study on the porcine eye two dimensional temperature distributions with lateral resolution of 170 μm and line scans with temporal resolution of 13 μs are discussed with respect to the meaning of mean temperature. Using the newest generation of surgery equipment it is shown, that the mean temperature rise can be kept below 5 °C during myopic laser in situ keratomileusis (LASIK) treatments corresponding to an aberration-free correction of -2.75 diopter.

The Recovery of Optical Quality after Laser Vision Correction

PubMed Central

Jung, Hyeong-Gi

2013-01-01

Purpose To evaluate the optical quality after laser in situ keratomileusis (LASIK) or serial photorefractive keratectomy (PRK) using a double-pass system and to follow the recovery of optical quality after laser vision correction. Methods This study measured the visual acuity, manifest refraction and optical quality before and one day, one week, one month, and three months after laser vision correction. Optical quality parameters including the modulation transfer function, Strehl ratio and intraocular scattering were evaluated with a double-pass system. Results This study included 51 eyes that underwent LASIK and 57 that underwent PRK. The optical quality three months post-surgery did not differ significantly between these laser vision correction techniques. Furthermore, the preoperative and postoperative optical quality did not differ significantly in either group. Optical quality recovered within one week after LASIK but took between one and three months to recover after PRK. The optical quality of patients in the PRK group seemed to recover slightly more slowly than their uncorrected distance visual acuity. Conclusions Optical quality recovers to the preoperative level after laser vision correction, so laser vision correction is efficacious for correcting myopia. The double-pass system is a useful tool for clinical assessment of optical quality. PMID:23908570

Investigation of the formation mechanism and morphology of the features created in the interior of cornea by femtosecond laser pulses

NASA Astrophysics Data System (ADS)

Guo, Yizang; Vukelic, Sinisa

2015-03-01

Laser assisted corneal surgeries often rely on the nonlinear absorption effect of ultrafast lasers to induce features in the interior of the cornea without affecting the surface. In particular, corneal flap formation in femtosecond assisted Laser- Assisted in situ Keratomileusis (LASIK) is based on the bubble creation. This study focuses on the interaction between the tissue and the femtosecond laser. Interior of cornea is treated with tightly focused femtosecond laser pulses. Due to the nature of the process, heating of the tissue within and around the focal volume is practically instantaneous. The affected region is subject to thermoelastic stress that arises with the steep temperature elevation. To predict the size of the region subject to the morphological changes due to the laser treatment, the temperature field is calculated. Cavitation bubble initiation and expansion process, which acts as precursor to the stress induced tissue trauma, is studied as well. Theoretical findings are compared against experimental results. High-speed camera is utilized to assess the laser treatment process, showing the temporal development of the cavitation bubbles. The results obtained in this study facilitate a better understanding of the effects of femtosecond laser assisted corneal surgeries and help in choosing optimal laser parameters.

Mechanisms of Optical Regression Following Corneal Laser Refractive Surgery: Epithelial and Stromal Responses

PubMed Central

MOSHIRFAR, Majid; DESAUTELS, Jordan D.; WALKER, Brian D.; MURRI, Michael S.; BIRDSONG, Orry C.; HOOPES, Phillip C. Sr

2018-01-01

Laser vision correction is a safe and effective method of reducing spectacle dependence. Photorefractive Keratectomy (PRK), Laser In Situ Keratomileusis (LASIK), and Small-Incision Lenticule Extraction (SMILE) can accurately correct myopia, hyperopia, and astigmatism. Although these procedures are nearing optimization in terms of their ability to produce a desired refractive target, the long term cellular responses of the cornea to these procedures can cause patients to regress from the their ideal postoperative refraction. In many cases, refractive regression requires follow up enhancement surgeries, presenting additional risks to patients. Although some risk factors underlying refractive regression have been identified, the exact mechanisms have not been elucidated. It is clear that cellular proliferation events are important mediators of optical regression. This review focused specifically on cellular changes to the corneal epithelium and stroma, which may influence postoperative visual regression following LASIK, PRK, and SMILE procedures. PMID:29644238

In-situ tomographic observation of tissue surface during laser ablation

NASA Astrophysics Data System (ADS)

Haruna, Masamitsu; Konoshita, Ryuh; Ohmi, Masato; Kunizawa, Naomi; Miyachi, Mayumi

2001-07-01

In laser ablation of tissues, tomography of the tissue surface is necessary for measurement of the crater depth and observation of damage of the surrounding tissue. We demonstrate here OCT images of craters made by UV laser ablation of different tissues. The maximum depth of a crater is found among several OCT images, and then the ablation rate is determined. The conventional OCT of the spatial resolution of 15 μm was used in our experiment, but OCT of the resolution of the order of 1 μm is required because the ablation rate is usually a few microns per pulse. Such a high-resolution OCT is also demonstrated in this paper, where the light source is a halogen lamp. Combination of laser ablation and OCT will lead to in situ tomographic observation of tissue surface during laser ablation, which should allow us to develop new laser surgeries.

Predictability of Pilot Performance from Simulated to Real Flight in the UH-60 (Black Hawk) Helicopter

DTIC Science & Technology

2008-02-01

keratectomy ( PRK ) and laser in-situ keratomileusis ( LASIK ) procedures to determine compatibility, safety, and efficacy of these procedures for rated Army...performance data. Table B- 1. Simulator and aircraft mean flight performance. LASIK PRK Simulator Aircraft Simulator Aircraft Pre-op 60.81 (2.65) 56.41...12 7. Aircraft vs . Simulator scatter plot, hover turn maneuvers

In-situ sequential laser transfer and laser reduction of graphene oxide films

NASA Astrophysics Data System (ADS)

Papazoglou, S.; Petridis, C.; Kymakis, E.; Kennou, S.; Raptis, Y. S.; Chatzandroulis, S.; Zergioti, I.

2018-04-01

Achieving high quality transfer of graphene on selected substrates is a priority in device fabrication, especially where drop-on-demand applications are involved. In this work, we report an in-situ, fast, simple, and one step process that resulted in the reduction, transfer, and fabrication of reduced graphene oxide-based humidity sensors, using picosecond laser pulses. By tuning the laser illumination parameters, we managed to implement the sequential printing and reduction of graphene oxide flakes. The overall process lasted only a few seconds compared to a few hours that our group has previously published. DC current measurements, X-Ray Photoelectron Spectroscopy, X-Ray Diffraction, and Raman Spectroscopy were employed in order to assess the efficiency of our approach. To demonstrate the applicability and the potential of the technique, laser printed reduced graphene oxide humidity sensors with a limit of detection of 1700 ppm are presented. The results demonstrated in this work provide a selective, rapid, and low-cost approach for sequential transfer and photochemical reduction of graphene oxide micro-patterns onto various substrates for flexible electronics and sensor applications.

Volume Measurements of Laser-generated Pits for in Situ Geochronology Using KArLE (Potassium-Argon Laser Experiment)

NASA Technical Reports Server (NTRS)

French, R. A.; Cohen, B. A.; Miller, J. S.

2014-01-01

KArLE (Potassium-­-Argon Laser Experiment) has been developed for in situ planetary geochronology using the K - Ar (potassium-­-argon) isotope system, where material ablated by LIBS (Laser-­-Induced Breakdown Spectroscopy) is used to calculate isotope abundances. We are determining the accuracy and precision of volume measurements of these pits using stereo and laser microscope data to better understand the ablation process for isotope abundance calculations. If a characteristic volume can be determined with sufficient accuracy and precision for specific rock types, KArLE will prove to be a useful instrument for future planetary rover missions.

Effect of marking pens on femtosecond laser-assisted flap creation.

PubMed

Ide, Takeshi; Kymionis, George D; Abbey, Ashkan M; Yoo, Sonia H; Culbertson, William W; O'Brien, Terrence P

2009-06-01

To compare the ease of the flap lift after central corneal marking with 2 types of marking pens after femtosecond laser-assisted flap creation in laser in situ keratomileusis. Bascom Palmer Eye Institute, University of Miami, Miami, Florida, USA. Porcine eyes were prepared for flap creation with a femtosecond laser (IntraLase). The eyes were assigned to 1 of 4 groups. After the femtosecond laser treatment, the difficulty of flap lifting the 4 groups was compared. Twelve porcine eyes, 3 in each group, were evaluated. In the 2 groups in which an oil-based pen was used, the corneal flap could not be lifted. In the 2 groups in which a water-based pen was used, the corneal flap was easily lifted. Oil-based ink may reduce the ability of the femtosecond laser to penetrate the cornea. The resultant corneal flap may require aggressive manipulation to be lifted. When used to mark the center of the cornea before flap creation, water-based ink provided greater ease of corneal flap lifting than oil-based ink. Because the marking is located over the center of the pupil, any alteration of the cornea in this area from aggressive flap lifting may result in substantial visual loss. Therefore, the use of an oil-based ink to mark the central cornea must be avoided to prevent traumatic irregularities of the flap stroma.

Laser annealing and in situ absorption measurement of float glass implanted with Ag ions

NASA Astrophysics Data System (ADS)

Okur, I.; Townsend, P. D.

2004-08-01

In this paper in situ pulsed laser annealing and absorption measurements results of Ag-implanted float glass are reported. A Nd:YAG laser harmonic at 266 nm was used to anneal the target area by coupling energy to the glass host, whilst an argon laser at 488 nm was used as a probe beam of changes in nanoparticle size. The equilibrium conditions show a third order power dependence on the laser pulse energy, which is attributed to the volume in which ion migration can occur during excitation.

Advancing an In situ Laser Spectrometer for Carbon Isotope Analyses in the Deep Ocean

NASA Astrophysics Data System (ADS)

Michel, A.; Wankel, S. D.; Kapit, J.; Girguis, P. R.

2016-02-01

Development of in situ chemical sensors is critical for improving our understanding of deep-ocean biogeochemistry and recent advances in chemical sensors are already expanding the breadth and depth of deep sea/seafloor exploration and research. Although initially developed for high sensitivity measurements of atmospheric gases, laser-based spectroscopic sensors are now being developed for research in the deep sea by incorporating the use of semi-permeable membranes. Here we present on recent deep-sea deployments of an in situ laser-based analyzer of carbon isotopes of methane (δ13CH4), highlighting several advances including a new capability for also measuring δ13C of DIC or CO2 by incorporating a second laser and an in line acidification module. A bubble trapping approach was designed and implemented for the collection and analysis of both CH4 and CO2 from deep-sea bubbles. The newly advanced laser spectrometer was deployed at both Kick `Em Jenny volcano off of the island of Grenada and in a brine pool in the western Gulf of Mexico ("The Jacuzzi of Despair") using the E/V Nautilus and the ROV Hercules. At Kick `Em Jenny, seafloor measurements were made of both emanating fluids and bubbles from within and around the crater - revealing high levels of magmatic CO2 with minor amounts of CH4 and hydrogen sulfide. At the brine pool, spot measurements and depth profile measurements into the brine pool were made for chemical mapping, revealing fluids that were saturated with respect to methane. New technologies such as the laser spectrometer will enable us to obtain high resolution and near real-time, in situ chemical and isotopic data and to make geochemical maps over a range of spatial and temporal scales.

Effect of laser polarization and pulse energy on therapeutic, femtosecond laser-induced second harmonic generation in corneal tissue (Conference Presentation)

NASA Astrophysics Data System (ADS)

Calhoun, William R.; Ilev, Ilko K.

2016-03-01

Some of the most commonly performed surgical operations in the world, including laser-assisted in-situ keratomileusis (LASIK), lens replacement (e.g. cataract surgery), and keratoplasty (cornea transplant), now employ therapeutic infrared femtosecond lasers (FSLs) for their extreme precision, low energy delivered into tissue and advanced ablation characteristics. Although the widely exploited applications of FSLs in medical therapeutics offer significant benefits, FSLs must generate very high intensities in order to achieve optical breakdown, the predominant tissue ablative mechanism, which can also stimulate nonlinear optical effects such as harmonic generation, an effect that generates coherent visible and UV light in the case of second- (SHG) and third-harmonic generation (THG), respectively. In order to improve the understanding of HG in corneal tissue, the effect of FSL polarization and pulse energy were investigated. FSL stimulated SHG intensity in corneal tissue was measured as the laser polarization was rotated 360 degrees. Further, the pulse energy at the SHG wavelength were measured for single FSL pulses as the pulse energy at the fundamental wavelength was varied through a range of clinically relevant values. The results of this study revealed SHG intensity oscillated with laser polarization, having a variation greater than 20%. This relationship seems to due to the intrinsic anisotropy of collagen fibril hyperpolarizability, not related to tissue birefringence. SHG pulse energy measurements showed an increase in SHG pulse energy with increasing FSL pulse energy, however conversion efficiency decreased. This may be related to the dynamic relationship between optical breakdown leading to tissue destruction and HG evolution.

Planar Laser Imaging of Scattering and Fluorescence of Zooplankton Feeding in Layers of Phytoplankton in situ

DTIC Science & Technology

2007-09-30

Planar Laser Imaging of Scattering and Fluorescence of Zooplankton Feeding in Layers of Phytoplankton in situ Peter J.S. Franks Scripps...herbivorous copepod feeding in the laboratory, and 2) to apply these methods in the field to observe the dynamics of copepod feeding in situ. In...particular we intend to test the “ feeding sorties” hypothesis vs. the “in situ feeding ” hypothesis regarding the location and timing of copepod feeding

The Aviation Accident Experience of Civilian Airmen With Refractive Surgery

DTIC Science & Technology

2002-06-01

such as photorefractive keratec- tomy (PRK) and laser-assisted in situ keratomileusis ( LASIK ), are being performed on a rapidly growing number of...stable, healing is complete, and no glare intolerance is present (4). RK, PRK, and LASIK procedures are similar only in that the goal is to improve...called photoablation, which utilizes the excimer laser to vaporize the cornea’s outer tissue. LASIK uses a specially designed surgical scalpel

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.

Towards femtosecond laser surgery guidance in the posterior eye: utilization of optical coherence tomography and adaptive optics for focus positioning and shaping

NASA Astrophysics Data System (ADS)

Krüger, Alexander; Hansen, Anja; Matthias, Ben; Ripken, Tammo

2014-02-01

Although fs-laser surgery is clinically established in the field of corneal flap cutting for laser in situ keratomileusis, surgery with fs-laser in the posterior part of the eye is impaired by focus degradation due to aberrations. Precise targeting and keeping of safety distance to the retina also relies on an intraoperative depth resolved imaging. We demonstrate a concept for image guided fs-laser surgery in the vitreous body combining adaptive optics (AO) for focus reshaping and optical coherence tomography (OCT) for focus position guidance. The setup of the laboratory system consist of an 800 nm fs-laser which is focused into a simple eye model via a closed loop adaptive optics system with Hartmann-Shack sensor and a deformable mirror to correct for wavefront aberrations. A spectral domain optical coherence tomography system is used to target phantom structures in the eye model. Both systems are set up to share the same scanner and focusing optics. The use of adaptive optics results in a lowered threshold energy for laser induced breakdown and an increased cutting precision. 3D OCT imaging of porcine retinal tissue prior and immediately after fs-laser cutting is also demonstrated. In the near future OCT and AO will be two essential assistive components in possible clinical systems for fs-laser based eye surgery beyond the cornea.

Effect of pulsed laser parameters on in-situ TiC synthesis in laser surface treatment

NASA Astrophysics Data System (ADS)

Hamedi, M. J.; Torkamany, M. J.; Sabbaghzadeh, J.

2011-04-01

Commercial titanium sheets pre-coated with 300-μm thick graphite layer were treated by employing a pulsed Nd:YAG laser in order to enhance surface properties such as wear and erosion resistance. Laser in-situ alloying method produced a composite layer by melting the titanium substrate and dissolution of graphite in the melt pool. Correlations between pulsed laser parameters, microstructure and microhardness of the synthesized composite coatings were investigated. Effects of pulse duration and overlapping factor on the microstructure and hardness of the alloyed layer were deduced from Vickers micro-indentation tests, XRD, SEM and metallographic analyses of cross sections of the generated layer. Results show that the composite cladding layer was constituted with TiC intermetallic phase between the titanium matrix in particle and dendrite forms. The dendritic morphology of composite layer was changed to cellular grain structure by increasing laser pulse duration and irradiated energy. High values of the measured hardness indicate that deposited titanium carbide increases in the conditions with more pulse duration and low process speed. This occurs due to more dissolution of carbon into liquid Ti by heat input increasing and positive influence of the Marangoni flow in the melted zone.

Scattering properties of ultrafast laser-induced refractive index shaping lenticular structures in hydrogels

NASA Astrophysics Data System (ADS)

Wozniak, Kaitlin T.; Germer, Thomas A.; Butler, Sam C.; Brooks, Daniel R.; Huxlin, Krystel R.; Ellis, Jonathan D.

2018-02-01

We present measurements of light scatter induced by a new ultrafast laser technique being developed for laser refractive correction in transparent ophthalmic materials such as cornea, contact lenses, and/or intraocular lenses. In this new technique, called intra-tissue refractive index shaping (IRIS), a 405 nm femtosecond laser is focused and scanned below the corneal surface, inducing a spatially-varying refractive index change that corrects vision errors. In contrast with traditional laser correction techniques, such as laser in-situ keratomileusis (LASIK) or photorefractive keratectomy (PRK), IRIS does not operate via photoablation, but rather changes the refractive index of transparent materials such as cornea and hydrogels. A concern with any laser eye correction technique is additional scatter induced by the process, which can adversely affect vision, especially at night. The goal of this investigation is to identify sources of scatter induced by IRIS and to mitigate possible effects on visual performance in ophthalmic applications. Preliminary light scattering measurements on patterns written into hydrogel showed four sources of scatter, differentiated by distinct behaviors: (1) scattering from scanned lines; (2) scattering from stitching errors, resulting from adjacent scanning fields not being aligned to one another; (3) diffraction from Fresnel zone discontinuities; and (4) long-period variations in the scans that created distinct diffraction peaks, likely due to inconsistent line spacing in the writing instrument. By knowing the nature of these different scattering errors, it will now be possible to modify and optimize the design of IRIS structures to mitigate potential deficits in visual performance in human clinical trials.

Concept for image-guided vitreo-retinal fs-laser surgery: adaptive optics and optical coherence tomography for laser beam shaping and positioning

NASA Astrophysics Data System (ADS)

Matthias, Ben; Brockmann, Dorothee; Hansen, Anja; Horke, Konstanze; Knoop, Gesche; Gewohn, Timo; Zabic, Miroslav; Krüger, Alexander; Ripken, Tammo

2015-03-01

Fs-lasers are well established in ophthalmic surgery as high precision tools for corneal flap cutting during laser in situ keratomileusis (LASIK) and increasingly utilized for cutting the crystalline lens, e.g. in assisting cataract surgery. For addressing eye structures beyond the cornea, an intraoperative depth resolved imaging is crucial to the safety and success of the surgical procedure due to interindividual anatomical disparities. Extending the field of application even deeper to the posterior eye segment, individual eye aberrations cannot be neglected anymore and surgery with fs-laser is impaired by focus degradation. Our demonstrated concept for image-guided vitreo-retinal fs-laser surgery combines adaptive optics (AO) for spatial beam shaping and optical coherence tomography (OCT) for focus positioning guidance. The laboratory setup comprises an adaptive optics assisted 800 nm fs-laser system and is extended by a Fourier domain optical coherence tomography system. Phantom structures are targeted, which mimic tractional epiretinal membranes in front of excised porcine retina within an eye model. AO and OCT are set up to share the same scanning and focusing optics. A Hartmann-Shack sensor is employed for aberration measurement and a deformable mirror for aberration correction. By means of adaptive optics the threshold energy for laser induced optical breakdown is lowered and cutting precision is increased. 3D OCT imaging of typical ocular tissue structures is achieved with sufficient resolution and the images can be used for orientation of the fs-laser beam. We present targeted dissection of the phantom structures and its evaluation regarding retinal damage.

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.

Aircrew Performance Cutting-Edge Technology: Emerging Human Performance Enhancement Technology Vision in Support of Operational Military Aviation Strategy

DTIC Science & Technology

2003-09-01

Refractive Surgery Origin and History, (RK, PRK , LASIK ) Refractive surgery was first considered as early as 1898 by a Dutch professor and was...34 This ejection demonstrated one extreme facet of the safety of PRK . Laser-Assisted In Situ Keratomileusis ( LASIK ) LASIK offers the greatest...refractive shift of clinical significance.35 Therefore LASIK and PRK , recipients had no significant vision changes at altitude, unlike recipients of RK

In situ stratospheric measurements of HNO3 and HCl near 30 km using the balloon-borne laser in situ sensor tunable diode laser spectrometer

NASA Technical Reports Server (NTRS)

May, R. D.; Webster, C. R.

1989-01-01

In situ stratospheric measurements of the concentrations of the reservoir species HNO3 and HCl made during two flights of the high-resolution (0.0005/cm) balloon-borne laser in situ sensor instrument from Palestine, Texas, are reported. A measured HNO3 volume mixing ratio of 4.3 parts per billion by volume (ppbv) at 31 km altitude is about 1 ppbv larger than previously reported measurements at 32 deg N. An HCl mixing ratio of 1.6 ppbv at 29 km is in agreement with values obtained from earlier remote sensing techniques within the experimental uncertainties. Upper limits at 31 km of 0.4 ppbv for H2O2 and 0.2 ppbv for HOCl are also derived from analyses of spectra recorded near 1252/cm.

Signal processing and calibration procedures for in situ diode-laser absorption spectroscopy.

PubMed

Werle, P W; Mazzinghi, P; D'Amato, F; De Rosa, M; Maurer, K; Slemr, F

2004-07-01

Gas analyzers based on tunable diode-laser spectroscopy (TDLS) provide high sensitivity, fast response and highly specific in situ measurements of several atmospheric trace gases simultaneously. Under optimum conditions even a shot noise limited performance can be obtained. For field applications outside the laboratory practical limitations are important. At ambient mixing ratios below a few parts-per-billion spectrometers become more and more sensitive towards noise, interference, drift effects and background changes associated with low level signals. It is the purpose of this review to address some of the problems which are encountered at these low levels and to describe a signal processing strategy for trace gas monitoring and a concept for in situ system calibration applicable for tunable diode-laser spectroscopy. To meet the requirement of quality assurance for field measurements and monitoring applications, procedures to check the linearity according to International Standard Organization regulations are described and some measurements of calibration functions are presented and discussed.

In situ analysis of Titan's tholins by Laser 2 steps Desorption Ionisation

NASA Astrophysics Data System (ADS)

Benilan, Y.; Carrasco, N.; Cernogora, G.; Gazeau, M.; Mahjoub, A.; Szopa, C.; Schwell, M.

2013-12-01

The main objective of the whole project developed in collaboration (LISA/LATMOS) is to provide a better understanding of the chemical composition of Titan aerosols laboratory analogs, called tholins, and thereby of their formation pathways. The tholins are produced in the PAMPRE reactor (French acronyme for Aerosols Microgravity Production by Reactives Plasmas) developed at LATMOS. These tholins are generated in levitation (wall effects are thus limited) in a low pressure radiofrequency plasma. Up to now, the determination of the physical and chemical properties of these tholins was achieved after their collection and ex-situ analysis by several methods. Their bulk composition was then determined but their insoluble part is still unknown. Other studies were performed after the transfer of the soluble part of the aerosols to different analytical instruments. Therefore, possible artifacts could have influenced the results. We present the SMARD (a French acronym for Mass Spectrometry of Aerosols by InfraRed Laser Desorption) program. A challenging issue of our work is to perform the soluble and unsoluble parts of PAMPRE tholins' analysis in real time and in situ. The coupling of the PAMPRE reactor to a unique instrument (Single Particle Laser Ablation Mass Spectrometry) developed at LISA should allow determining in real time and in situ the characteristics (chemical composition together with granulometry) of the nanometric aerosols. The later are introduced in the analytical instrument using an aerodynamic lens device. Their detection and aerodynamic diameter are determined using two continuous diode lasers operating at λ = 403 nm. Then, the L2DI (Laser 2 steps Desorption Ionisation) technique is used in order to access to the chemical composition of individual particles: they are vaporized using a 10 μm CO2 pulsed laser and the gas produced is then ionized by a 248 nm KrF Excimer laser. Finally, the molecular ions are analyzed by a 1 m linear time-of-flight mass

Optical Quality, Threshold Target Identification, and Military Target Task Performance After Advanced Keratorefractive Surgery

DTIC Science & Technology

2012-05-01

undergo wavefront-guided (WFG) photorefractive keratectomy ( PRK ), WFG laser in situ keratomileusis ( LASIK ), wavefront optimized (WFO) PRK or WFO...Military, Refractive Surgery, PRK , LASIK , Night Vision, Wavefront Optimized, Wavefront Guided, Visual Performance, Quality of Vision, Outcomes...military. In a prospective, randomized treatment trial we will enroll 224 nearsighted soldiers to WFG photorefractive keratectomy ( PRK ), WFG LASIK , WFO PRK

Review of Efforts to Develop a Low-Luminance-Level Disability Glare Tester

DTIC Science & Technology

2009-09-01

figures 1. LASIK and PRK refractive surgery. .......................................................................................... 6  2...inadequate at this time, particularly for post refractive surgery patients. Early LASIK and PRK produced a very high incidence of night vision...1999). They found that before PRK or LASER in-situ keratomileusis ( LASIK ), simulated pupil dilation from 3 to 7 mm caused a 5-6 fold increase in

Continued Development of in Situ Geochronology for Planetary Using KArLE (Potassium-Argon Laser Experiment)

NASA Technical Reports Server (NTRS)

Devismes, D.; Cohen, B. A.

2016-01-01

Geochronology is a fundamental measurement for planetary samples, providing the ability to establish an absolute chronology for geological events, including crystallization history, magmatic evolution, and alteration events, and providing global and solar system context for such events. The capability for in situ geochronology will open up the ability for geochronology to be accomplished as part of lander or rover complement, on multiple samples rather than just those returned. An in situ geochronology package can also complement sample return missions by identifying the most interesting rocks to cache or return to Earth. The K-Ar radiometric dating approach to in situ dating has been validated by the Curiosity rover on Mars as well as several laboratories on Earth. Several independent projects developing in situ rock dating for planetary samples, based on the K-Ar method, are giving promising results. Among them, the Potassium (K)-Argon Laser Experiment (KArLE) at MSFC is based on techniques already in use for in planetary exploration, specifically, Laser-induced Breakdown Spectroscopy (LIBS, used on the Curiosity Chemcam), mass spectroscopy (used on multiple planetary missions, including Curiosity, ExoMars, and Rosetta), and optical imaging (used on most missions).

The Potassium-Argon Laser Experiment (KArLE): In Situ Geochronology for Planetary Robotic Missions

NASA Technical Reports Server (NTRS)

Cohen, Barbara

2016-01-01

The Potassium (K) - Argon (Ar) Laser Experiment (KArLE) will make in situ noble-gas geochronology measurements aboard planetary robotic landers and roverss. Laser-Induced Breakdown Spectroscopy (LIBS) is used to measure the K abun-dance in a sample and to release its noble gases; the evolved Ar is measured by mass spectrometry (MS); and rela-tive K content is related to absolute Ar abundance by sample mass, determined by optical measurement of the ablated volume. KArLE measures a whole-rock K-Ar age to 10% or better for rocks 2 Ga or older, sufficient to resolve the absolute age of many planetary samples. The LIBS-MS approach is attractive because the analytical components have been flight proven, do not require further technical development, and provide complementary measurements as well as in situ geochronology.

Optical Quality and Threshold Target Identification and Military Target Task Performance after Advanced Keratorefractive Surgery

DTIC Science & Technology

2013-05-01

and Sensors Directorate. • Study participants and physicians select treatment: PRK or LASIK . WFG vs . WFO treatment modality is randomized. The...to undergo wavefront-guided (WFG) photorefractive keratectomy ( PRK ), WFG laser in situ keratomileusis ( LASIK ), wavefront optimized (WFO) PRK or WFO...TERMS Military, Refractive Surgery, PRK , LASIK , Night Vision, Wavefront Optimized, Wavefront Guided, Visual Performance, Quality of Vision, Outcomes

Quantitative Potassium Measurements with Laser-Induced Breakdown Spectroscopy Using Low-Energy Lasers: Application to In Situ K-Ar Geochronology for Planetary Exploration.

PubMed

Cho, Yuichiro; Horiuchi, Misa; Shibasaki, Kazuo; Kameda, Shingo; Sugita, Seiji

2017-08-01

In situ radiogenic isotope measurements to obtain the absolute age of geologic events on planets are of great scientific value. In particular, K-Ar isochrons are useful because of their relatively high technical readiness and high accuracy. Because this isochron method involves spot-by-spot K measurements using laser-induced breakdown spectroscopy (LIBS) and simultaneous Ar measurements with mass spectrometry, LIBS measurements are conducted under a high vacuum condition in which emission intensity decreases significantly. Furthermore, using a laser power used in previous planetary missions is preferable to examine the technical feasibility of this approach. However, there have been few LIBS measurements for K under such conditions. In this study, we measured K contents in rock samples using 30 mJ and 15 mJ energy lasers under a vacuum condition (10 -3  Pa) to assess the feasibility of in situ K-Ar dating with lasers comparable to those used in NASA's Curiosity and Mars 2020 missions. We obtained various calibration curves for K using internal normalization with the oxygen line at 777 nm and continuum emission from the laser-induced plasma. Experimental results indicate that when K 2 O < 1.1 wt%, a calibration curve using the intensity of the K emission line at 769 nm normalized with that of the oxygen line yields the best results for the 30 mJ laser energy, with a detection limit of 88 ppm and 20% of error at 2400 ppm of K 2 O. Futhermore, the calibration curve based on the K 769 nm line intensity normalized with continuum emission yielded the best result for the 15 mJ laser, giving a detection limit of 140 ppm and 20% error at 3400 ppm K 2 O. Error assessments using obtained calibration models indicate that a 4 Ga rock with 3000 ppm K 2 O would be measured with 8% (30 mJ) and 10% (15 mJ) of precision in age when combined with mass spectrometry of 40 Ar with 10% of uncertainty. These results strongly suggest that high precision

A Novel Laser Refractive Surgical Treatment for Presbyopia: Optics-Based Customization for Improved Clinical Outcome.

PubMed

Pajic, Bojan; Pajic-Eggspuehler, Brigitte; Mueller, Joerg; Cvejic, Zeljka; Studer, Harald

2017-06-13

Laser Assisted in Situ Keratomileusis (LASIK) is a proven treatment method for corneal refractive surgery. Surgically induced higher order optical aberrations were a major reason why the method was only rarely used to treat presbyopia, an age-related near-vision loss. In this study, a novel customization algorithm for designing multifocal ablation patterns, thereby minimizing induced optical aberrations, was used to treat 36 presbyopic subjects. Results showed that most candidates went from poor visual acuity to uncorrected 20/20 vision or better for near (78%), intermediate (92%), and for distance (86%) vision, six months after surgery. All subjects were at 20/25 or better for distance and intermediate vision, and a majority (94%) were also better for near vision. Even though further studies are necessary, our results suggest that the employed methodology is a safe, reliable, and predictable refractive surgical treatment for presbyopia.

Outcome of corneal and laser astigmatic axis alignment in photoastigmatic refractive keratectomy.

PubMed

Farah, S G; Olafsson, E; Gwynn, D G; Azar, D T; Brightbill, F S

2000-12-01

To compare the refractive results of laser astigmatic treatment in eyes in which the astigmatic axes of the eye and laser are aligned by limbal marking at the 6 o'clock position and in eyes that are not marked. University Hospital and Clinics, Madison, Wisconsin, USA. This retrospective study comprised 143 eyes that had photoastigmatic refractive keratectomy with the VISX Star excimer laser. The eyes were divided into marked (G1) and unmarked (G2) groups. Based on the preoperative astigmatism, each group was subdivided into low astigmatism (/=1.25 D). Early postoperative manifest refractions (1.0 to 2.5 months) were analyzed. The Alpins vector analysis method was used to calculate the target induced astigmatism, surgically induced astigmatism, difference vector (DV), magnitude of error (ME), angle of error (AE), and index of success (IS). There was no significant difference between the groups in DV, ME, and IS. When the subgroups were analyzed, the DV and ME were comparable; the IS in the G1 high astigmatism subgroup was significantly better than that in the G2 high astigmatism subgroup (0.22 +/- 0.08 and 0.29 +/- 0.04, respectively; P <.0001). There was comparable scatter of AE values; 30% and 36% in G1 and G2, respectively, had an AE of 0. Similar scatter was observed in the subgroups. Of the eyes that had an AE of 0, 90% and 43% in the high astigmatism subgroups of G1 and G2, respectively (P <.05), had full correction of astigmatism. Limbal marking and subsequent eye and laser astigmatic axis alignment improved the refractive outcome of laser astigmatic treatment of >/=1.25 D. A preliminary report of an ongoing prospective randomized study of eyes that had laser in situ keratomileusis is included.

Optical Quality, Threshold Target Identification, and Military Target Task Performance After Advanced Keratorefractive Surgery

DTIC Science & Technology

2011-05-01

WFG) photorefractive keratectomy (PRK), WFG laser in situ keratomileusis ( LASIK ), wavefront optimized (WFO) PRK or WFO LASIK (56 in each group...design will enable comparison to preoperative performance as well as comparisons between treatment groups. Military, Refractive Surgery, PRK, LASIK ...randomized treatment trial we will enroll 224 nearsighted soldiers to WFG photorefractive keratectomy (PRK), WFG LASIK , WFO PRK or WFO LASIK (56 in

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

In situ mitigation of subsurface and peripheral focused ion beam damage via simultaneous pulsed laser heating

DOE PAGES

Stanford, Michael G.; Lewis, Brett B.; Iberi, Vighter O.; ...

2016-02-16

Focused helium and neon ion (He(+)/Ne(+) ) beam processing has recently been used to push resolution limits of direct-write nanoscale synthesis. The ubiquitous insertion of focused He(+) /Ne(+) beams as the next-generation nanofabrication tool-of-choice is currently limited by deleterious subsurface and peripheral damage induced by the energetic ions in the underlying substrate. The in situ mitigation of subsurface damage induced by He(+)/Ne(+) ion exposures in silicon via a synchronized infrared pulsed laser-assisted process is demonstrated. The pulsed laser assist provides highly localized in situ photothermal energy which reduces the implantation and defect concentration by greater than 90%. The laser-assisted exposuremore » process is also shown to reduce peripheral defects in He(+) patterned graphene, which makes this process an attractive candidate for direct-write patterning of 2D materials. In conclusion, these results offer a necessary solution for the applicability of high-resolution direct-write nanoscale material processing via focused ion beams.« less

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

An in situ approach to study trace element partitioning in the laser heated diamond anvil cell

DOE Office of Scientific and Technical Information (OSTI.GOV)

Petitgirard, S.; Mezouar, M.; Borchert, M.

2012-01-15

Data on partitioning behavior of elements between different phases at in situ conditions are crucial for the understanding of element mobility especially for geochemical studies. Here, we present results of in situ partitioning of trace elements (Zr, Pd, and Ru) between silicate and iron melts, up to 50 GPa and 4200 K, using a modified laser heated diamond anvil cell (DAC). This new experimental set up allows simultaneous collection of x-ray fluorescence (XRF) and x-ray diffraction (XRD) data as a function of time using the high pressure beamline ID27 (ESRF, France). The technique enables the simultaneous detection of sample meltingmore » based to the appearance of diffuse scattering in the XRD pattern, characteristic of the structure factor of liquids, and measurements of elemental partitioning of the sample using XRF, before, during and after laser heating in the DAC. We were able to detect elements concentrations as low as a few ppm level (2-5 ppm) on standard solutions. In situ measurements are complimented by mapping of the chemical partitions of the trace elements after laser heating on the quenched samples to constrain the partitioning data. Our first results indicate a strong partitioning of Pd and Ru into the metallic phase, while Zr remains clearly incompatible with iron. This novel approach extends the pressure and temperature range of partitioning experiments derived from quenched samples from the large volume presses and could bring new insight to the early history of Earth.« less

Laser-based mass spectrometry for in situ chemical composition analysis of planetary surfaces

NASA Astrophysics Data System (ADS)

Frey, Samira; Neuland, Maike B.; Grimaudo, Valentine; Moreno-García, Pavel; Riedo, Andreas; Tulej, Marek; Broekmann, Peter; Wurz, Peter

2016-04-01

Mass spectrometry is an important analytical technique in space research. The chemical composition of planetary surface material is a key scientific question on every space mission to a planet, moon or asteroid. Chemical composition measurements of rocky material on the surface are of great importance to understand the origin and evolution of the planetary body.[1] A miniature laser ablation/ionisation reflectron- type time-of-flight mass spectrometer (instrument name LMS) was designed and built at the University of Bern for planetary research.[2] Despite its small size and light weight, the LMS instrument still maintains the same capabilities as large laboratory systems, which makes it suitable for its application on planetary space missions.[3-5] The high dynamic range of about eight orders of magnitude, high lateral (μm-level) and vertical (sub-nm level) resolution and high detection sensitivity for almost all elements (10 ppb, atomic fraction) make LMS a versatile instrument for various applications. LMS is a suitable instrument for in situ measurements of elemental and isotope composition with high precision and accuracy. Measurements of Pb- isotope abundances can be used for dating of planetary material. Measurements of bio-relevant elements allow searching for past or present life on a planetary surface. The high spatial resolution, both in lateral and vertical direction, is of considerable interest, e.g. for analysis of inhomogeneous, extraterrestrial samples as well as weathering processes of planetary material. References [1] P. Wurz, D. Abplanalp, M. Tulej, M. Iakovleva, V.A. Fernandes, A. Chumikov, and G. Managadze, "Mass Spectrometric Analysis in Planetary Science: Investigation of the Surface and the Atmosphere", Sol. Sys. Res., 2012, 46, 408. [2] U. Rohner, J.A. Whitby, P. Wurz, "A miniature laser ablation time of flight mass spectrometer for in situ planetary exploration" Meas. Sci. Tch., 2003, 14, 2159. [3] M. Tulej, A. Riedo, M.B. Neuland, S

CO2 laser and/or fluoride enamel treatment against in situ/ex vivo erosive challenge.

PubMed

Jordão, Maísa Camillo; Forti, Gustavo Manzano; Navarro, Ricardo Scarparo; Freitas, Patrícia Moreira; Honório, Heitor Marques; Rios, Daniela

2016-01-01

This in situ/ex vivo study investigated the effect of CO2 laser irradiation and acidulated phosphate fluoride gel (APF) application, separately and in combination, on enamel resistance to erosion. During 2 experimental 5-day crossover phases, 8 volunteers wore intraoral appliances containing bovine enamel blocks which were submitted to four groups: 1st phase - control, untreated and CO2 laser irradiation, 2nd phase - fluoride application and fluoride application before CO2 laser irradiation. Laser irradiation was performed at 10.6 µm wavelength, 5 µs pulse duration and 50 Hz frequency, with average power input and output of 2.3 W and 2.0 W, respectively (28.6 J/cm2). APF gel (1.23%F, pH 3.5) was applied on enamel surface with a microbrush and left on for 4 minutes. Then, the enamel blocks were fixed at the intraoral appliance level. The erosion was performed extraorally 4 times daily for 5 min in 150 mL of cola drink. Enamel loss was measured profilometrically after treatment and after the in situ phase. The data were tested using one-way Repeated Measures Anova and Tukey's test (p<0.05). CO2 laser alone (2.00±0.39 µm) did not show any significantly preventive effect against enamel erosion when compared with the control group (2.41±1.20 µm). Fluoride treated enamel, associated (1.50±0.30 µm) or not (1.47±0.63 µm) with laser irradiation, significantly differed from the control. The APF application decreased enamel wear; however, CO2 laser irradiation did not enhance fluoride ability to reduce enamel wear.

Matrix-Assisted Laser Desorption Ionization Imaging Mass Spectrometry: In Situ Molecular Mapping

PubMed Central

Angel, Peggi M.; Caprioli, Richard M.

2013-01-01

Matrix-assisted laser desorption ionization imaging mass spectrometry (IMS) is a relatively new imaging modality that allows mapping of a wide range of biomolecules within a thin tissue section. The technology uses a laser beam to directly desorb and ionize molecules from discrete locations on the tissue that are subsequently recorded in a mass spectrometer. IMS is distinguished by the ability to directly measure molecules in situ ranging from small metabolites to proteins, reporting hundreds to thousands of expression patterns from a single imaging experiment. This article reviews recent advances in IMS technology, applications, and experimental strategies that allow it to significantly aid in the discovery and understanding of molecular processes in biological and clinical samples. PMID:23259809

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

PubMed

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

2005-04-01

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

In situ diagnosis of pulsed UV laser surface ablation of tungsten carbide hardmetal by using laser-induced optical emission spectroscopy

NASA Astrophysics Data System (ADS)

Li, Tiejun; Lou, Qihong; Wei, Yunrong; Huang, Feng; Dong, Jingxing; Liu, Jingru

2001-12-01

Surface ablation of cobalt cemented tungsten carbide hardmetal with pulsed UV laser has been in situ diagnosed by using the technique of laser-induced optical emission spectroscopy. The dependence of emission intensity of cobalt lines on number of laser shots was investigated at laser fluence of 2.5 J/cm 2. As a comparison, the reliance of emission intensity of cobalt lines as a function of laser pulse number by using pure cobalt as ablation sample was also studied at the same laser condition. It was found that for surface ablation of tungsten carbide hardmetal at laser fluence of 2.5 J/cm 2, the intensities of cobalt lines fell off dramatically in the first 300 consecutive laser shots and then slowed down to a low stable level with even more shots. For surface ablation of pure cobalt at the same laser condition, the intensities of cobalt lines remained constant more or less even after 500 laser shots and then reduced very slowly with even more shots. It was concluded that selective evaporation of cobalt at this laser fluence should be responsible for the dramatic fall-off of cobalt lines with laser shots accumulation for surface ablation of tungsten carbide hardmetal. In contrast, for surface ablation of pure cobalt, the slow reduction of cobalt lines with pulse number accumulation should be due to the formation of laser-induced crater effect.

Effects of Altitude Exposure in Photorefractive Keratectomy (PRK) Subjects

DTIC Science & Technology

2006-08-01

changes in RK and early post-op Laser In-situ Keratomileusis ( LASIK ) subjects but not in PRK subjects. The Tanzer8 study evaluated 30 naval aviators...Pikes Peak. The Pikes Peak study, conducted over a three days at 14,100 feet, reported no significant change in PRK and LASIK treated subjects as...The effect of hypoxia on refraction following LASIK surgery. IOVS 1999; 40(4):S895 4. Ng JD, White LJ, Parmley VC, Hubickey W, Carter J, Mader TH

In-situ small-angle x-ray scattering study of nanoparticles in the plasma plume induced by pulsed laser irradiation of metallic targets

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lavisse, L.; Jouvard, J.-M.; Girault, M.

2012-04-16

Small angle x-ray scattering was used to probe in-situ the formation of nanoparticles in the plasma plume generated by pulsed laser irradiation of a titanium metal surface under atmospheric conditions. The size and morphology of the nanoparticles were characterized as function of laser irradiance. Two families of nanoparticles were identified with sizes on the order of 10 and 70 nm, respectively. These results were confirmed by ex-situ transmission electron microscopy experiments.

In-Situ Apatite Laser Ablation U-Th-Sm/He Dating, Methods and Challenges

NASA Astrophysics Data System (ADS)

Pickering, J. E.; Matthews, W.; Guest, B.; Hamilton, B.; Sykes, C.

2015-12-01

In-situ, laser ablation U-Th-Sm/He dating is an emerging technique in thermochronology that has been proven as a means to date zircon and monzonite1-5. In-situ U-Th-Sm/He thermochronology eliminates many of the problems and inconveniences associated with traditional, whole grain methods, including; reducing bias in grain selection based on size, shape and clarity; allowing for the use of broken grains and grains with inclusions; avoiding bad neighbour effects; and eliminating safety hazards associated with dissolution. In-situ apatite laser ablation is challenging due to low concentrations of U and Th and thus a low abundance of radiogenic He. For apatite laser ablation to be effective the ultra-high-vacuum (UHV) line must have very low and consistent background levels of He. To reduce He background, samples are mounted in a UHV stable medium. Our mounting process uses a MicroHePP (Microscope Mounted Heated Platen Press) to press samples into FEP (fluorinated ethylene propylene) bonded to an aluminum backing plate. Samples are ablated using a Resonetics 193 nm excimer laser and liberated He is measured using a quadrupole mass spectrometer on the ASI Alphachron noble gas line; collectively this system is known as the Resochron. The ablated sites are imaged using a Zygo Zescope optical profilometer and ablated pit volume measured using PitVol, a custom MatLab algorithm developed to enable precise and unbiased measurement of the ablated pit geometry. We use the well-characterized Durango apatite to demonstrate the accuracy and precision of the method. He liberated from forty-two pits, having volumes between 1700 and 9000 um3, were measured using the Resochron. The ablated sites were imaged using a Zygo Zescope optical profilometer and ablated pit volume measured using PitVol. U, Th and Sm concentrations were measured by laser ablation and the U-Th-Sm/He age calculated by standard age equation. An age of 33.8±0.31 Ma was determined and compares well with conventional

In situ X-ray imaging of defect and molten pool dynamics in laser additive manufacturing.

PubMed

Leung, Chu Lun Alex; Marussi, Sebastian; Atwood, Robert C; Towrie, Michael; Withers, Philip J; Lee, Peter D

2018-04-10

The laser-matter interaction and solidification phenomena associated with laser additive manufacturing (LAM) remain unclear, slowing its process development and optimisation. Here, through in situ and operando high-speed synchrotron X-ray imaging, we reveal the underlying physical phenomena during the deposition of the first and second layer melt tracks. We show that the laser-induced gas/vapour jet promotes the formation of melt tracks and denuded zones via spattering (at a velocity of 1 m s -1 ). We also uncover mechanisms of pore migration by Marangoni-driven flow (recirculating at a velocity of 0.4 m s -1 ), pore dissolution and dispersion by laser re-melting. We develop a mechanism map for predicting the evolution of melt features, changes in melt track morphology from a continuous hemi-cylindrical track to disconnected beads with decreasing linear energy density and improved molten pool wetting with increasing laser power. Our results clarify aspects of the physics behind LAM, which are critical for its development.

CO2 laser and/or fluoride enamel treatment against in situ/ex vivo erosive challenge

PubMed Central

JORDÃO, Maísa Camillo; FORTI, Gustavo Manzano; NAVARRO, Ricardo Scarparo; FREITAS, Patrícia Moreira; HONÓRIO, Heitor Marques; RIOS, Daniela

2016-01-01

ABSTRACT Objective This in situ/ex vivo study investigated the effect of CO2 laser irradiation and acidulated phosphate fluoride gel (APF) application, separately and in combination, on enamel resistance to erosion. Material and Methods During 2 experimental 5-day crossover phases, 8 volunteers wore intraoral appliances containing bovine enamel blocks which were submitted to four groups: 1st phase - control, untreated and CO2 laser irradiation, 2nd phase - fluoride application and fluoride application before CO2 laser irradiation. Laser irradiation was performed at 10.6 µm wavelength, 5 µs pulse duration and 50 Hz frequency, with average power input and output of 2.3 W and 2.0 W, respectively (28.6 J/cm2). APF gel (1.23%F, pH 3.5) was applied on enamel surface with a microbrush and left on for 4 minutes. Then, the enamel blocks were fixed at the intraoral appliance level. The erosion was performed extraorally 4 times daily for 5 min in 150 mL of cola drink. Enamel loss was measured profilometrically after treatment and after the in situ phase. The data were tested using one-way Repeated Measures Anova and Tukey's test (p<0.05). Results CO2 laser alone (2.00±0.39 µm) did not show any significantly preventive effect against enamel erosion when compared with the control group (2.41±1.20 µm). Fluoride treated enamel, associated (1.50±0.30 µm) or not (1.47±0.63 µm) with laser irradiation, significantly differed from the control. Conclusion The APF application decreased enamel wear; however, CO2 laser irradiation did not enhance fluoride ability to reduce enamel wear. PMID:27383703

A Novel Laser Refractive Surgical Treatment for Presbyopia: Optics-Based Customization for Improved Clinical Outcome

PubMed Central

Pajic, Bojan; Pajic-Eggspuehler, Brigitte; Mueller, Joerg; Cvejic, Zeljka; Studer, Harald

2017-01-01

Laser Assisted in Situ Keratomileusis (LASIK) is a proven treatment method for corneal refractive surgery. Surgically induced higher order optical aberrations were a major reason why the method was only rarely used to treat presbyopia, an age-related near-vision loss. In this study, a novel customization algorithm for designing multifocal ablation patterns, thereby minimizing induced optical aberrations, was used to treat 36 presbyopic subjects. Results showed that most candidates went from poor visual acuity to uncorrected 20/20 vision or better for near (78%), intermediate (92%), and for distance (86%) vision, six months after surgery. All subjects were at 20/25 or better for distance and intermediate vision, and a majority (94%) were also better for near vision. Even though further studies are necessary, our results suggest that the employed methodology is a safe, reliable, and predictable refractive surgical treatment for presbyopia. PMID:28608800

In situ surface roughness measurement using a laser scattering method

NASA Astrophysics Data System (ADS)

Tay, C. J.; Wang, S. H.; Quan, C.; Shang, H. M.

2003-03-01

In this paper, the design and development of an optical probe for in situ measurement of surface roughness are discussed. Based on this light scattering principle, the probe which consists of a laser diode, measuring lens and a linear photodiode array, is designed to capture the scattered light from a test surface with a relatively large scattering angle ϕ (=28°). This capability increases the measuring range and enhances repeatability of the results. The coaxial arrangement that incorporates a dual-laser beam and a constant compressed air stream renders the proposed system insensitive to movement or vibration of the test surface as well as surface conditions. Tests were conducted on workpieces which were mounted on a turning machine that operates with different cutting speeds. Test specimens which underwent different machining processes and of different surface finish were also studied. The results obtained demonstrate the feasibility of surface roughness measurement using the proposed method.

Influence of stromal refractive index and hydration on corneal laser refractive surgery.

PubMed

de Ortueta, Diego; von Rüden, Dennis; Magnago, Thomas; Arba Mosquera, Samuel

2014-06-01

To evaluate the influence of the stromal refractive index and hydration on postoperative outcomes in eyes that had corneal laser refractive surgery using the Amaris laser system. Augenzentrum Recklinghausen, Recklinghausen, Germany. Comparative case series. At the 6-month follow-up, right eyes were retrospectively analyzed. The effect of the stromal refractive index and hydration on refractive outcomes was assessed using univariate linear and multilinear correlations. Sixty eyes were analyzed. Univariate linear analyses showed that the stromal refractive index and hydration were correlated with the thickness of the preoperative exposed stroma and was statistically different for laser in situ keratomileusis and laser-assisted subepithelial keratectomy treatments. Univariate multilinear analyses showed that the spherical equivalent (SE) was correlated with the attempted SE and stromal refractive index (or hydration). Analyses suggest overcorrections for higher stromal refractive index values and for lower hydration values. The stromal refractive index and hydration affected postoperative outcomes in a subtle, yet significant manner. An adjustment toward greater attempted correction in highly hydrated corneas and less intended correction in low hydrated corneas might help optimize refractive outcomes. Mr. Magnago and Dr. Arba-Mosquera are employees of and Dr. Diego de Ortueta is a consultant to Schwind eye-tech-solutions GmbH & Co. KG. Mr. Rüden has no financial or proprietary interest in any material or method mentioned. Copyright © 2014 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.

In-situ characterization of nanoparticle beams focused with an aerodynamic lens by Laser-Induced Breakdown Detection

PubMed Central

Barreda, F.-A.; Nicolas, C.; Sirven, J.-B.; Ouf, F.-X.; Lacour, J.-L.; Robert, E.; Benkoula, S.; Yon, J.; Miron, C.; Sublemontier, O.

2015-01-01

The Laser-Induced Breakdown Detection technique (LIBD) was adapted to achieve fast in-situ characterization of nanoparticle beams focused under vacuum by an aerodynamic lens. The method employs a tightly focused, 21 μm, scanning laser microprobe which generates a local plasma induced by the laser interaction with a single particle. A counting mode optical detection allows the achievement of 2D mappings of the nanoparticle beams with a reduced analysis time thanks to the use of a high repetition rate infrared pulsed laser. As an example, the results obtained with Tryptophan nanoparticles are presented and the advantages of this method over existing ones are discussed. PMID:26498694

Outcomes of LASIK for Myopia or Myopic Astigmatism Correction with the FS200 Femtosecond Laser and EX500 Excimer Laser Platform

PubMed Central

Niparugs, Muanploy; Tananuvat, Napaporn; Chaidaroon, Winai; Tangmonkongvoragul, Chulaluck; Ausayakhun, Somsanguan

2018-01-01

Purpose: To evaluate the efficacy, predictability, stability and safety of laser in situ keratomileusis (LASIK) using the FS200 femtosecond laser and EX500 excimer laser platform. Methods: The outcomes of 254 eyes of 129 consecutive patients with myopia or myopic astigmatism who underwent full correction femtosecond laser-assisted LASIK at CMU LASIK Center were assessed. Pre-operative and post-operative parameters including manifest refraction, Uncorrected Distance Visual Acuity (UDVA), Best Corrected Distance Visual Acuity (BDVA), corneal topography and tomography were analyzed. The results between low to moderate myopia and high myopia were compared up to 12 months. Results: Mean pre-operative Spherical Equivalent (SE) was -5.15±2.41 Diopters (D) (range -0.50 to -11.50 D) and -0.13±0.28 D, -0.13±0.27 D, -0.13±0.28 D and -0.14±0.30 D at 1, 3, 6, and 12 months, post-operatively. At 12 months, the propor¬tion of eyes achieving UDVA ≥ 20/20 was 90.0% and ≥20/40 was 98.8%. The proportion of eyes achieving post-operative mean SE ±0.5 D, and ±1 D was 91.3%, and 98.5%. No eyes lost more than two lines of BDVA. The low to moderate myopic group had a statistically significant better UDVA at one (p=0.017) and three months (p=0.014) but no difference at six (p=0.061) and 12 months (p=0.091). The mean post-operative SE was better in low to moderate myopic group at every follow-up visit (p=0.001, 0.007, <0.001 and <0.001). Conclusion: One-year clinical results of LASIK with the FS200 femtosecond laser and EX500 excimer laser showed high efficacy, predictability, stability and safety. PMID:29872485

Remote in-situ laser-induced breakdown spectroscopy using optical fibers

NASA Astrophysics Data System (ADS)

Marquardt, Brian James

The following dissertation describes the development of methods for performing remote Laser-Induced Breakdown Spectroscopy (LIBS) using optical fibers. Studies were performed to determine the optimal excitation and collection parameters for remote LIBS measurements of glasses, soils and paint. A number of fiber-optic LIBS probes were developed and used to characterize various samples by plasma emission spectroscopy. A novel method for launching high-power laser pulses into optical fibers without causing catastrophic failure is introduced. A systematic study of a number of commercially available optical fibers was performed to determine which optical fibers were best suited for delivering high-power laser pulses. The general design of an all fiber-optic LIBS probe is described and applied to the determination of Pb in soil. A fiber-optic probe was developed for the microanalysis of solid samples remotely by LIBS, Raman spectroscopy and Raman imaging. The design of the probe allows for real-time sample imaging in-situ using coherent imaging fibers. This allows for precise atomic emission and Raman measurements to be performed remotely on samples in hostile or inaccessible environments. A novel technique was developed for collecting spectral plasma images using an acousto-optic tunable filter (AOTF). The spatial and temporal characteristics of the plasma were studied as a function of delay time. From the plasma images the distribution of Pb emission could be determined and fiber-optic designs could be optimized for signal collection. The performance of a two fiber LIBS probe is demonstrated for the determination of the amount of lead in samples of dry paint. It is shown that dry paint samples can be analyzed for their Pb content in-situ using a fiber-optic LIBS probe with detection limits well below the levels currently regulated by the Consumer Products Safety Commission. It is also shown that these measurements can be performed on both latex and enamel paints, and

Preliminary results of in situ laser-induced breakdown spectroscopy for the first wall diagnostics on EAST

NASA Astrophysics Data System (ADS)

Hu, Zhenhua; Li, Cong; Xiao, Qingmei; Liu, Ping; Fang, Ding; Mao, Hongmin; Wu, Jing; Zhao, Dongye; Ding, Hongbin; Luo, Guang-Nan; EAST Team

2017-02-01

Post-mortem methods cannot fulfill the requirement of monitoring the lifetime of the plasma facing components (PFC) and measuring the tritium inventory for the safety evaluation. Laser-induced breakdown spectroscopy (LIBS) is proposed as a promising method for the in situ study of fuel retention and impurity deposition in a tokamak. In this study, an in situ LIBS system was successfully established on EAST to investigate fuel retention and impurity deposition on the first wall without the need of removal tiles between plasma discharges. Spectral lines of D, H and impurities (Mo, Li, Si, … ) in laser-induced plasma were observed and identified within the wavelength range of 500-700 nm. Qualitative measurements such as thickness of the deposition layers, element depth profile and fuel retention on the wall are obtained by means of in situ LIBS. The results demonstrated the potential applications of LIBS for in situ characterization of fuel retention and co-deposition on the first wall of EAST. Supported by the National Magnetic Confinement Fusion Science Program of China (Nos. 2013GB105002, 2015GB109001, and 2013GB109005), National Natural Science Foundation of China (Nos. 11575243, 11605238, 11605023), Chinesisch-Deutsches Forschungs Project (GZ765), and Korea Research Council of Fundamental Science and Technology (KRCF) under the international collaboration & research in Asian countries (PG1314).

Investigation into the Use of the Concept Laser QM System as an In-Situ Research and Evaluation Tool

NASA Technical Reports Server (NTRS)

Bagg, Stacey

2014-01-01

The NASA Marshall Space Flight Center (MSFC) is using a Concept Laser Fusing (Cusing) M2 powder bed additive manufacturing system for the build of space flight prototypes and hardware. NASA MSFC is collecting and analyzing data from the M2 QM Meltpool and QM Coating systems for builds. This data is intended to aide in understanding of the powder-bed additive manufacturing process, and in the development of a thermal model for the process. The QM systems are marketed by Concept Laser GmbH as in-situ quality management modules. The QM Meltpool system uses both a high-speed near-IR camera and a photodiode to monitor the melt pool generated by the laser. The software determines from the camera images the size of the melt pool. The camera also measures the integrated intensity of the IR radiation, and the photodiode gives an intensity value based on the brightness of the melt pool. The QM coating system uses a high resolution optical camera to image the surface after each layer has been formed. The objective of this investigation was to determine the adequacy of the QM Meltpool system as a research instrument for in-situ measurement of melt pool size and temperature and its applicability to NASA's objectives in (1) Developing a process thermal model and (2) Quantifying feedback measurements with the intent of meeting quality requirements or specifications. Note that Concept Laser markets the system only as capable of giving an indication of changes between builds, not as an in-situ research and evaluation tool. A secondary objective of the investigation is to determine the adequacy of the QM Coating system as an in-situ layer-wise geometry and layer quality evaluation tool.

In situ measurements of fuel retention by laser induced desorption spectroscopy in TEXTOR

NASA Astrophysics Data System (ADS)

Zlobinski, M.; Philipps, V.; Schweer, B.; Huber, A.; Stoschus, H.; Brezinsek, S.; Samm, U.; TEXTOR Team

2011-12-01

In future fusion devices such as ITER tritium retention due to tritium co-deposition in mixed material layers can be a serious safety problem. Laser induced desorption spectroscopy (LIDS) can measure the hydrogen content of hydrogenic carbon layers locally on plasma-facing components, while hydrogen is used as a tritium substitute. For several years, this method has been applied in the TEXTOR tokamak in situ during plasma operation to monitor the hydrogen content in space and time. This work shows the LIDS signal reproducibility and studies the effects of different plasma conditions, desorption distances from the plasma and different laser energies using a dedicated sample with constant hydrogen amount. Also the LIDS signal evaluation procedure is described in detail and the detection limits for different conditions in the TEXTOR tokamak are estimated.

Development of the Potassium-Argon Laser Experiment (KArLE) Instrument for In Situ Geochronology

NASA Technical Reports Server (NTRS)

Cohen, Barbara A.; Li, Z.-H.; Miller, J. S.; Brinckerhoff, W. B.; Clegg, S. M.; Mahaffy, P. R.; Swindle, T. D.; Wiens, R. C.

2012-01-01

Absolute dating of planetary samples is an essential tool to establish the chronology of geological events, including crystallization history, magmatic evolution, and alteration. Traditionally, geochronology has only been accomplishable on samples from dedicated sample return missions or meteorites. The capability for in situ geochronology is highly desired, because it will allow one-way planetary missions to perform dating of large numbers of samples. The success of an in situ geochronology package will not only yield data on absolute ages, but can also complement sample return missions by identifying the most interesting rocks to cache and/or return to Earth. In situ dating instruments have been proposed, but none have yet reached TRL 6 because the required high-resolution isotopic measurements are very challenging. Our team is now addressing this challenge by developing the Potassium (K) - Argon Laser Experiment (KArLE) under the NASA Planetary Instrument Definition and Development Program (PIDDP), building on previous work to develop a K-Ar in situ instrument [1]. KArLE uses a combination of several flight-proven components that enable accurate K-Ar isochron dating of planetary rocks. KArLE will ablate a rock sample, determine the K in the plasma state using laser-induced breakdown spectroscopy (LIBS), measure the liberated Ar using quadrupole mass spectrometry (QMS), and relate the two by the volume of the ablated pit using an optical method such as a vertical scanning interferometer (VSI). Our preliminary work indicates that the KArLE instrument will be capable of determining the age of several kinds of planetary samples to +/-100 Myr, sufficient to address a wide range of geochronology problems in planetary science.

Femtosecond laser beam propagation through corneal tissue: Evaluation of therapeutic laser-stimulated second and third- harmonic generation

NASA Astrophysics Data System (ADS)

Calhoun, William R., III

One of the most recent advancements in laser technology is the development of ultrashort pulsed femtosecond lasers (FSLs). FSLs are improving many fields due to their unique extreme precision, low energy and ablation characteristics. In the area of laser medicine, ophthalmic surgeries have seen very promising developments. Some of the most commonly performed surgical operations in the world, including laser-assisted in-situ keratomileusis (LASIK), lens replacement (cataract surgery), and keratoplasty (cornea transplant), now employ FSLs for their unique abilities that lead to improved clinical outcome and patient satisfaction. The application of FSLs in medical therapeutics is a recent development, and although they offer many benefits, FSLs also stimulate nonlinear optical effects (NOEs), many of which were insignificant with previously developed lasers. NOEs can change the laser characteristics during propagation through a medium, which can subsequently introduce unique safety concerns for the surrounding tissues. Traditional approaches for characterizing optical effects, laser performance, safety and efficacy do not properly account for NOEs, and there remains a lack of data that describe NOEs in clinically relevant procedures and tissues. As FSL technology continues to expand towards new applications, FSL induced NOEs need to be better understood in order to ensure safety as FSL medical devices and applications continue to evolve at a rapid pace. In order to improve the understanding of FSL-tissue interactions related to NOEs stimulated during laser beam propagation though corneal tissue, research investigations were conducted to evaluate corneal optical properties and determine how corneal tissue properties including corneal layer, collagen orientation and collagen crosslinking, and laser parameters including pulse energy, repetition rate and numerical aperture affect second and third-harmonic generation (HG) intensity, duration and efficiency. The results of

In-Situ Real-Time Focus Detection during Laser Processing Using Double-Hole Masks and Advanced Image Sensor Software

PubMed Central

Hoang, Phuong Le; Ahn, Sanghoon; Kim, Jeng-o; Kang, Heeshin; Noh, Jiwhan

2017-01-01

In modern high-intensity ultrafast laser processing, detecting the focal position of the working laser beam, at which the intensity is the highest and the beam diameter is the lowest, and immediately locating the target sample at that point are challenging tasks. A system that allows in-situ real-time focus determination and fabrication using a high-power laser has been in high demand among both engineers and scientists. Conventional techniques require the complicated mathematical theory of wave optics, employing interference as well as diffraction phenomena to detect the focal position; however, these methods are ineffective and expensive for industrial application. Moreover, these techniques could not perform detection and fabrication simultaneously. In this paper, we propose an optical design capable of detecting the focal point and fabricating complex patterns on a planar sample surface simultaneously. In-situ real-time focus detection is performed using a bandpass filter, which only allows for the detection of laser transmission. The technique enables rapid, non-destructive, and precise detection of the focal point. Furthermore, it is sufficiently simple for application in both science and industry for mass production, and it is expected to contribute to the next generation of laser equipment, which can be used to fabricate micro-patterns with high complexity. PMID:28671566

IN SITU Deposition of Fe-TiC Nanocomposite on Steel by Laser Cladding

NASA Astrophysics Data System (ADS)

Razavi, Mansour; Rahimipour, Mohammad Reza; Ganji, Mojdeh; Ganjali, Mansoreh; Gangali, Monireh

The possibility of deposition of Fe-TiC nanocomposite on the surface of carbon steel substrate with the laser coating method had been investigated. Mechanical milling was used for the preparation of raw materials. The mixture of milled powders was used as a coating material on the substrate steel surface and a CO2 laser was used in continuous mode for coating. Microstructural studies were performed by scanning electron microscopy. Determinations of produced phases, crystallite size and mean strain have been done by X-ray diffraction. The hardness and wear resistance of coated samples were measured. The results showed that the in situ formation of Fe-TiC nanocomposite coating using laser method is possible. This coating has been successfully used to improve the hardness and wear resistance of the substrate so that the hardness increased by about six times. Coated iron and titanium carbide crystallite sizes were in the nanometer scale.

The Potassium-Argon Laser Experiment (KARLE): In Situ Geochronology for Planetary Robotic Missions

NASA Technical Reports Server (NTRS)

Cohen, B. A.; Devismes, D.; Miller, J. S.; Swindle, T. D.

2014-01-01

Isotopic dating is an essential tool to establish an absolute chronology for geological events, including crystallization history, magmatic evolution, and alteration events. The capability for in situ geochronology will open up the ability for geochronology to be accomplished as part of lander or rover complement, on multiple samples rather than just those returned. An in situ geochronology package can also complement sample return missions by identifying the most interesting rocks to cache or return to Earth. The K-Ar Laser Experiment (KArLE) brings together a novel combination of several flight-proven components to provide precise measurements of potassium (K) and argon (Ar) that will enable accurate isochron dating of planetary rocks. KArLE will ablate a rock sample, measure the K in the plasma state using laser-induced breakdown spectroscopy (LIBS), measure the liberated Ar using mass spectrometry (MS), and relate the two by measuring the volume of the ablated pit by optical imaging. Our work indicates that the KArLE instrument is capable of determining the age of planetary samples with sufficient accuracy to address a wide range of geochronology problems in planetary science. Additional benefits derive from the fact that each KArLE component achieves analyses useful for most planetary surface missions.

Sequential lift and suture technique for post-LASIK corneal striae.

PubMed

Mackool, Richard J; Monsanto, Vivian R

2003-04-01

We describe a surgical technique to manage persistent corneal striae after laser in situ keratomileusis (LASIK). The sequential lift and suture technique reduces the time required for LASIK, eliminates the need to fixate the flap with forceps during suturing, and increases the accuracy of suture placement. The results in 10 eyes (9 patients) showed complete resolution of striae with improvement in subjective symptoms (glare and blurred vision) and best corrected visual acuity.

In Situ Chemical Composition Measurements of Planetary Surfaces with a Laser Ablation Mass Spectrometer

NASA Astrophysics Data System (ADS)

Brigitte Neuland, Maike; Riedo, Andreas; Meyer, Stefan; Mezger, Klaus; Tulej, Marek; Wurz, Peter

2013-04-01

The knowledge of the chemical composition of moons, comets, asteroids or other planetary bodies is of particular importance for the investigation of the origin and evolution of the Solar System. For cosmochemistry, the elemental and isotopic composition of the surface material is essential information to investigate origin, differentiation and evolution processes of the body and therefore the history of our Solar System [1]. We show that the use of laser-based mass spectrometers is essential in such research because of their high sensitivity in the ppm range and their capability for quantitative elemental and isotopic analysis. A miniaturised Laser Ablation Time-of-Flight Mass Spectrometer (LMS) was developed in our group to study the elemental composition of solid samples [2]. The instrument's small size and light weight make it suitable for an application on a space mission to determine the elemental composition of a planetary surface for example [3]. Meteorites offer the excellent possibility to study extraterrestrial material in the laboratory. To demonstrate the sensitivity and functionality of the LMS instrument, a sample of the Allende meteorite has been investigated with a high spatial resolution. The LMS measurements allowed investigations of the elemental abundances in the Allende meteorite and detailed studies of the mineralogy and volatility [4]. These approaches can be of considerable interest for in situ investigation of grains and inhomogeneous materials with high sensitivity on a planetary surface. [1] Wurz, P., Whitby, J., Managadze, G., 2009, Laser Mass Spectrometry in Planetary Science, AIP Conf. Proc. CP1144, 70-75. [2] Tulej, M., Riedo, A., Iakovleva, M., Wurz, P., 2012, Int. J. Spec., On Applicability of a Miniaturized Laser Ablation Time of Flight Mass Spectrometer for Trace Element Measurements, article ID 234949. [3] Riedo, A., Bieler, A., Neuland, M., Tulej, M., Wurz, P., 2012, Performance evaluation of a miniature laser ablation time

Corrective Lens Use and Refractive Error Among United States Air Force Aircrew

DTIC Science & Technology

2010-03-01

surgery was approved for aircrew members in August 2000. Initially only photorefractive keratectomy ( PRK ) was approved, but 200 MILITARY MEDICINE, Vol...approval for laser in-situ keratomileusis ( LASIK ), although USAF policy limits CRS treatments on aircrew to no more than 8.00 D of myopia, no more than...Undergraduate Pilot Training Pass/Fail Rate of Spectacled vs . Nonspectacled Student Pilots. Report No. USAFSAM-TR-85-50. Brooks Air Eorce Base, TX, USAE

In Situ analysis of CO2 laser irradiation on controlling progression of erosive lesions on dental enamel.

PubMed

Lepri, Taísa Penazzo; Scatolin, Renata Siqueira; Colucci, Vivian; De Alexandria, Adílis Kalina; Maia, Lucianne Cople; Turssi, Cecília Pedroso; Corona, Silmara Aparecida Milori

2014-08-01

The present study aimed to evaluate in situ the effect of CO2 laser irradiation to control the progression of enamel erosive lesions. Fifty-six slabs of bovine incisors enamel (5 × 3 × 2.5 mm(3) ) were divided in four distinct areas: (1) sound (reference area), (2) initial erosion, (3) treatment (irradiated or nonirradiated with CO2 laser), (4) final erosion (after in situ phase). The initial erosive challenge was performed with 1% citric acid (pH = 2.3), for 5 min, 2×/day, for 2 days. The slabs were divided in two groups according to surface treatment: irradiated with CO2 laser (λ = 10.6 µm; 0.5 W) and nonirradiate. After a 2-day lead-in period, 14 volunteers wore an intraoral palatal appliance containing two slabs (irradiated and nonirradiated), in two intraoral phases of 5 days each. Following a cross-over design during the first intraoral phase, half of the volunteers immersed the appliance in 100 mL of citric acid for 5 min, 3×/day, while other half of the volunteers used deionized water (control). The volunteers were crossed over in the second phase. Enamel wear was determined by an optical 3D profilometer. Three-way ANOVA for repeated measures revealed that there was no significant interaction between erosive challenge and CO2 laser irradiation (P = 0.419). Erosive challenge significantly increased enamel wear (P = 0.001), regardless whether or not CO2 laser irradiation was performed. There was no difference in enamel wear between specimens CO2 -laser irradiated and non-irradiated (P = 0.513). Under intraoral conditions, CO2 laser irradiation did not control the progression of erosive lesions in enamel caused by citric acid. © 2014 Wiley Periodicals, Inc.

Correction factor for ablation algorithms used in corneal refractive surgery with gaussian-profile beams

NASA Astrophysics Data System (ADS)

Jimenez, Jose Ramón; González Anera, Rosario; Jiménez del Barco, Luis; Hita, Enrique; Pérez-Ocón, Francisco

2005-01-01

We provide a correction factor to be added in ablation algorithms when a Gaussian beam is used in photorefractive laser surgery. This factor, which quantifies the effect of pulse overlapping, depends on beam radius and spot size. We also deduce the expected post-surgical corneal radius and asphericity when considering this factor. Data on 141 eyes operated on LASIK (laser in situ keratomileusis) with a Gaussian profile show that the discrepancy between experimental and expected data on corneal power is significantly lower when using the correction factor. For an effective improvement of post-surgical visual quality, this factor should be applied in ablation algorithms that do not consider the effects of pulse overlapping with a Gaussian beam.

The Effects of Scattered Light from Optical Components on Visual Function

DTIC Science & Technology

2016-02-01

zones (e.g., 0-5° vs 5-10°) occurs, then the general distribution of scatter, uniform or not, or that some ratio of scatter between different angular...affect the sensitivity of the eye and none reported having refractive surgery within the past year (photorefractive keratectomy ( PRK ) or laser...assisted in situ keratomileusis ( LASIK )). They performed all the visual function tasks monocularly, using the right eye. 2.3 Visual Function Assessment

Evaluating Acoustic Emission Signals as an in situ process monitoring technique for Selective Laser Melting (SLM)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fisher, Karl A.; Candy, Jim V.; Guss, Gabe

2016-10-14

In situ real-time monitoring of the Selective Laser Melting (SLM) process has significant implications for the AM community. The ability to adjust the SLM process parameters during a build (in real-time) can save time, money and eliminate expensive material waste. Having a feedback loop in the process would allow the system to potentially ‘fix’ problem regions before a next powder layer is added. In this study we have investigated acoustic emission (AE) phenomena generated during the SLM process, and evaluated the results in terms of a single process parameter, of an in situ process monitoring technique.

In situ process monitoring in selective laser sintering using optical coherence tomography

NASA Astrophysics Data System (ADS)

Gardner, Michael R.; Lewis, Adam; Park, Jongwan; McElroy, Austin B.; Estrada, Arnold D.; Fish, Scott; Beaman, Joseph J.; Milner, Thomas E.

2018-04-01

Selective laser sintering (SLS) is an efficient process in additive manufacturing that enables rapid part production from computer-based designs. However, SLS is limited by its notable lack of in situ process monitoring when compared with other manufacturing processes. We report the incorporation of optical coherence tomography (OCT) into an SLS system in detail and demonstrate access to surface and subsurface features. Video frame rate cross-sectional imaging reveals areas of sintering uniformity and areas of excessive heat error with high temporal resolution. We propose a set of image processing techniques for SLS process monitoring with OCT and report the limitations and obstacles for further OCT integration with SLS systems.

Update on Development of the Potassium-Argon Laser Experiment (KArLE) Instrument for In Situ Geochronology

NASA Technical Reports Server (NTRS)

Cohen, Barbara A.; Li, Z.-H.; Miller, J. S.; Brinckerhoff, W. B.; Clegg, S. M.; Mahaffy, P. R.; Swindle, T. D.; Wiens, R. C.

2013-01-01

Absolute dating of planetary samples is an essential tool to establish the chronology of geological events, including crystallization history, magmatic evolution, and alteration. We are addressing this challenge by developing the Potassium (K) -- Argon Laser Experiment (KArLE), building on previous work to develop a K-Ar in situ instrument. KArLE ablates a rock sample, determines the K in the plasma state using laser-induced breakdown spectroscopy (LIBS), measures the liberated Ar using quadrupole mass spectrometry (QMS), and relates the two by the volume of the ablated pit using laser confocal microscopy (LCM). Our goal is for the KArLE instrument to be capable of determining the age of several kinds of planetary samples to address a wide range of geochronolgy problems in planetary science.

Superconducting magnesium diboride films with Tc≈24 K grown by pulsed laser deposition with in situ anneal

NASA Astrophysics Data System (ADS)

Christen, H. M.; Zhai, H. Y.; Cantoni, C.; Paranthaman, M.; Sales, B. C.; Rouleau, C.; Norton, D. P.; Christen, D. K.; Lowndes, D. H.

2001-05-01

Thin superconducting films of magnesium diboride (MgB 2) with T c≈24 K were prepared on various oxide substrates by pulsed laser deposition followed by an in situ anneal. A systematic study of the influence of various in situ annealing parameters shows an optimum temperature of about 600°C in a background of 0.7 atm of Ar/4%H 2 for layers consisting of a mixture of magnesium and boron. Contrary to ex situ approaches (e.g. reacting boron films with magnesium vapor at ≈900°C), these films are processed at a temperature at which MgB 2 does not decompose rapidly even in vacuum. This may prove enabling in the formation of multilayers, junctions, and epitaxial films in future work. Issues related to the improvement of these films and to the possible in situ growth of MgB 2 at elevated temperature are discussed.

New developments in laser-heated diamond anvil cell with in situ synchrotron x-ray diffraction at High Pressure Collaborative Access Team

DOE Office of Scientific and Technical Information (OSTI.GOV)

Meng, Yue; Hrubiak, Rostislav; Rod, Eric

An overview of the in situ laser heating system at the High Pressure Collaborative Access Team, with emphasis on newly developed capabilities, is presented. Since its establishment at the beamline 16-ID-B a decade ago, laser-heated diamond anvil cell coupled with in situ synchrotron x-ray diffraction has been widely used for studying the structural properties of materials under simultaneous high pressure and high temperature conditions. Recent developments in both continuous-wave and modulated heating techniques have been focusing on resolving technical issues of the most challenging research areas. Furthermore, the new capabilities have demonstrated clear benefits and provide new opportunities in researchmore » areas including high-pressure melting, pressure-temperature-volume equations of state, chemical reaction, and time resolved studies.« less

New developments in laser-heated diamond anvil cell with in situ synchrotron x-ray diffraction at High Pressure Collaborative Access Team

DOE PAGES

Meng, Yue; Hrubiak, Rostislav; Rod, Eric; ...

2015-07-17

An overview of the in situ laser heating system at the High Pressure Collaborative Access Team, with emphasis on newly developed capabilities, is presented. Since its establishment at the beamline 16-ID-B a decade ago, laser-heated diamond anvil cell coupled with in situ synchrotron x-ray diffraction has been widely used for studying the structural properties of materials under simultaneous high pressure and high temperature conditions. Recent developments in both continuous-wave and modulated heating techniques have been focusing on resolving technical issues of the most challenging research areas. Furthermore, the new capabilities have demonstrated clear benefits and provide new opportunities in researchmore » areas including high-pressure melting, pressure-temperature-volume equations of state, chemical reaction, and time resolved studies.« less

New developments in laser-heated diamond anvil cell with in situ synchrotron x-ray diffraction at High Pressure Collaborative Access Team