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Soundarya B, Sachdev GS, Ramamurthy S, Kumar SK, Dandapani R. Visual outcomes of early enhancement following small incision lenticule extraction versus laser in situ keratomileusis. Indian J Ophthalmol 2023; 71:1845-1848. [PMID: 37203042 PMCID: PMC10391394 DOI: 10.4103/ijo.ijo_3209_22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/20/2023] Open
Abstract
Purpose To compare visual outcomes of early enhancement following small incision lenticule extraction (SMILE) versus laser in situ keratomileusis (LASIK). Methods Retrospective analysis of eyes (patients operated in the setting of a tertiary eye care hospital between 2014 and 2020) requiring early enhancement (within one year of primary surgery) was conducted. Stability of refractive error, corneal tomography, and anterior segment Optical Coherence Tomography (AS-OCT) for epithelial thickness was performed. The correction post regression was done using photorefractive keratectomy and flap lift in eyes, wherein the primary procedure was SMILE and LASIK, respectively. Pre- and post enhancement corrected and uncorrected distance visual acuity (CDVA and UDVA), mean refractive spherical equivalent (MRSE), and cylinder were analyzed. IBM SPSS statistical software. Results In total, 6350 and 8176 eyes post SMILE and LASIK, respectively, were analyzed. Of these, 32 eyes of 26 patients (0.5%) post SMILE and 36 eyes of 32 patients (0.44%) post-LASIK required enhancement. Post enhancement (flap lift in LASIK, and PRK in SMILE group) UDVA was logMAR 0.02 ± 0.05 and 0.09 ± 0.16 (P = 0.009), respectively. There was no significant difference between the refractive sphere (P = 0.33) and MRSE (P = 0.09). In total, 62.5% of the eyes in the SMILE group and 80.5% in the LASIK group had a UDVA of 20/20 or better (P = 0.04). Conclusion PRK post SMILE demonstrated comparable results to flap lift post LASIK and is a safe and effective approach for early enhancement post SMILE.
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Affiliation(s)
- B Soundarya
- Department Cornea and Refractive Services, The Eye Foundation, Coimbatore, Tamil Nadu, India
| | | | - Shreyas Ramamurthy
- Department Cornea and Refractive Services, The Eye Foundation, Coimbatore, Tamil Nadu, India
| | - Shreesha K Kumar
- Department Cornea and Refractive Services, The Eye Foundation, Coimbatore, Tamil Nadu, India
| | - Ramamurthy Dandapani
- Department Cornea and Refractive Services, The Eye Foundation, Coimbatore, Tamil Nadu, India
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Outcomes and Complications in Patients With Hypermobile Ehlers-Danlos Syndrome Who Have Undergone Laser In Situ Keratomileusis Surgery. Cornea 2023; 42:284-291. [PMID: 35389912 DOI: 10.1097/ico.0000000000003028] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2021] [Accepted: 02/10/2022] [Indexed: 11/25/2022]
Abstract
PURPOSE The purpose of this study was to determine the safety and outcomes of myopic laser in situ keratomileusis (LASIK) in patients who were secondarily diagnosed with hypermobile Ehlers-Danlos syndrome (EDS). METHODS We conducted a case series study on patients with hypermobile EDS who underwent myopic LASIK surgery. Visual acuity, manifest refraction, a full dilated eye examination, biometry measurements, and Scheimpflug imaging were performed in the Wilmer outpatient clinic. RESULTS There were 24 eyes of 12 patients included in this study. All participants were White women with a mean age of 46.58 years (SD 8.91 years). Participants were seen at an average of 13.83 years (SD 4.3 years, range 6-21 years) after undergoing LASIK. None of the patients in the series had a diagnosis of hypermobile EDS before LASIK surgery. Overall, 92% of patients were happy they got LASIK. The uncorrected distance visual acuity was 20/20 or better in 68% of eyes, and the best-corrected visual acuity was 20/20 or better in 92% of eyes. Manifest refraction was within 1 diopter of plano in 79% of patients. Dry eye symptoms were present in 83% of patients, and 46% of eyes had either punctate epithelial erosions or decreased tear break-up time. One of the 12 patients developed corneal ectasia in both eyes. CONCLUSIONS Patients with hypermobile EDS are generally satisfied with myopic LASIK correction, with good visual acuity outcomes and low rates of myopic regression. However, the risk of corneal ectasia may prevent laser vision correction from being a viable treatment option in these patients. Further studies are needed to make a definitive recommendation.
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Goes S, Delbeke H. Posterior chamber toric implantable collamer lenses vs LASIK for myopia and astigmatism: systematic review. J Cataract Refract Surg 2022; 48:1204-1210. [PMID: 36179351 DOI: 10.1097/j.jcrs.0000000000001007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2022] [Accepted: 07/05/2022] [Indexed: 11/26/2022]
Abstract
This systematic review compares the visual and refractive outcome of laser in situ keratomileusis with (toric) implantable collamer lens (ICL) in the treatment of myopic astigmatism. An electronic literature search led to 19 comparative articles. Refractive outcome, efficacy, safety, predictability, and stability as well as differences in contrast sensitivity and higher-order aberrations (HOAs) were analyzed for moderate (-3 to -6 diopters [D]) and high (≥-6 D) myopia. Results were either significantly in favor of (toric)-ICL or equal. Fewer HOAs and better contrast sensitivity after (toric)-ICL seem to be the largest asset in its refractive and clinical superiority. However, longer follow-up studies are indicated, specifically for systematically comparing long-term adverse effects.
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Affiliation(s)
- Stéphanie Goes
- From the Department of Ophthalmology, University Hospitals Leuven, Leuven, Belgium (Goes, Delbeke); KU Leuven, Biomedical Sciences Group, Department of Neurosciences, Research group Ophthalmology, Leuven, Belgium (Delbeke)
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Du R, Fang L, Peng W, Yang R, Nie S, Xiao H, Gong J, Dai Y, Deng J. Wave front aberrations induced from biomechanical effects after customized myopic laser refractive surgery in finite element model. Int Ophthalmol 2021; 42:81-94. [PMID: 34392473 DOI: 10.1007/s10792-021-02003-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2020] [Accepted: 08/06/2021] [Indexed: 11/28/2022]
Abstract
PURPOSE A customized myopic refractive surgery was simulated by establishing a finite element model of the human eye, after which we studied the wave front aberrations induced by biomechanical effects and ablation profile after wave front-guided LASIK surgery. METHODS Thirty myopia patients (i.e., 60 eyes) without other eye diseases were selected. Their ages, preoperative spherical equivalent, astigmatism, and wave front aberration were then obtained, in addition to the mean spherical equivalent error range - 4 to - 8D. Afterward, wave front-guided customized LASIK surgery was simulated by establishing a finite element eye model, followed by the analysis of the wave front aberrations induced by the surface displacement from corneal biomechanical effects, as well as customized ablation profile. Finally, the preoperative and induced aberrations were statistically analyzed. RESULTS Comatic aberrations were the main wave front abnormality induced by biomechanical effects, and the wave front aberrations induced by the ablation profile mainly included coma and secondary coma, as well as sphere and secondary-sphere aberrations. Overall, the total high-order aberrations (tHOAs), total coma (C31), and sphere ([Formula: see text]) increased after wave front-guided customized LASIK surgery. According to our correlation analyses, coma, sphere, and tHOAs were significantly correlated with decentration. Additionally, the material parameters of ocular tissue were found to affect the postoperative wave front aberrations. When the material parameters of the sclera remained constant but those of cornea increased, the induced wave front aberrations were reduced. CONCLUSION All biomechanical effects of cornea and ablation profile had significant effects on postoperative wave front aberrations after customized LASIK refractive surgery; however, the effects of the ablation profile were more notorious. Additionally, the characteristics of biomechanical materials have influence on the clinical correction effect.
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Affiliation(s)
- Ruirui Du
- Nanchang Hangkong University, Nanchang, 330063, China
| | - Lihua Fang
- Key Laboratory of Nondestructive Test (Ministry of Education), Nanchang Hangkong University, Nanchang, 86-18170938193, 330063, China.
| | - Weijian Peng
- Nanchang Hangkong University, Nanchang, 330063, China
| | - Ruizhi Yang
- Nanchang Hangkong University, Nanchang, 330063, China
| | - Shifeng Nie
- Nanchang Hangkong University, Nanchang, 330063, China
| | - Huirong Xiao
- Nanchang Hangkong University, Nanchang, 330063, China
| | - Jiahui Gong
- Nanchang Hangkong University, Nanchang, 330063, China
| | - Yu Dai
- Nanchang Hangkong University, Nanchang, 330063, China
| | - Jiahao Deng
- Nanchang Hangkong University, Nanchang, 330063, China
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5
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Rabina G, Mimouni M, Slomovic J, Sorkin N, Nemet A, Kaiserman I. Centration of myopic refractive ablation: should we center treatment on the pupil or the visual axis? Lasers Med Sci 2021; 36:1733-1739. [PMID: 34185167 DOI: 10.1007/s10103-021-03358-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2021] [Accepted: 06/07/2021] [Indexed: 11/30/2022]
Abstract
The purpose of this study is to compare pupil versus corneal vertex-centered ablation for myopic laser refractive surgery. This study is a retrospective case series of right eyes of consecutive myopic patients undergoing either photorefractive keratectomy (PRK) or laser-assisted in situ keratomileusis (LASIK) with pupil or corneal vertex-centered ablation from January 2018 to April 2018. Overall 258 eyes of 258 patients were included. Of the 104 that underwent LASIK, 52 were treated centered on the corneal vertex (50%), and of the 154 that underwent PRK, 77 were treated centered on the corneal vertex (50%). There were no significant differences in baseline age, gender, spherical equivalence, sphere, cylinder, or angle kappa between both groups in either LASIK or PRK. There were no significant differences between the corneal vertex-centered and pupil-centered groups in terms of efficacy index (LASIK: 1.02 ± 0.14 vs 1.01 ± 0.13, p = 0.86; PRK: 1.00 ± 0.13 vs 0.99 ± 0.15, p = 0.61), safety index (LASIK: 1.02 ± 0.12 vs 1.01 ± 0.13, p = 0.70; PRK:1.02 ± 0.12 vs 1.02 ± 0.09, p = 0.97), and residual astigmatism (LASIK: 0.26 ± 0.25 vs 0.23 ± 0.28, p = 0.65; PRK:0.37 ± 0.41 vs 0.39 ± 0.31, p = 0.78). In mixed effect models, there were no significant differences between the corneal vertex-centered and pupil-centered groups when accounting for angle kappa (p > 0.05). Patients with large angle kappa (> 300 μm) eyes yielded similar results (p > 0.05). For conclusion, in myopic refractive surgery, performing ablation centered on the corneal vertex or on the pupil leads to similar outcomes regardless of the amount of angle kappa.
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Affiliation(s)
- Gilad Rabina
- Department of Ophthalmology, Tel Aviv Sourasky Medical Center, 6 Weizmann Street, 64239, Tel-Aviv, Israel. .,Sackler School of Medicine, Tel-Aviv University, Tel-Aviv, Israel.
| | - Michael Mimouni
- Department of Ophthalmology, Rambam Health Care Campus, Haifa, Israel.,Bruce and Ruth Rappaport Faculty of Medicine, Technion-Israel Institute of Technology, Haifa, Israel.,Care-Vision Laser Centers, Tel-Aviv, Israel
| | - Jacqueline Slomovic
- Michael G. DeGroote School of Medicine, McMaster University, Hamilton, Ontario, Canada
| | - Nir Sorkin
- Department of Ophthalmology, Tel Aviv Sourasky Medical Center, 6 Weizmann Street, 64239, Tel-Aviv, Israel.,Sackler School of Medicine, Tel-Aviv University, Tel-Aviv, Israel
| | - Achia Nemet
- Sackler School of Medicine, Tel-Aviv University, Tel-Aviv, Israel
| | - Igor Kaiserman
- Care-Vision Laser Centers, Tel-Aviv, Israel.,Department of Ophthalmology, Barzilai Medical Center, Ashkelon, Israel.,Faculty of Health Sciences, Ben-Gurion University of the Negev, Beer Sheba, Israel
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[Regression and ablation profiles in corneal refractive surgery]. J Fr Ophtalmol 2021; 44:1059-1075. [PMID: 34148702 DOI: 10.1016/j.jfo.2020.08.041] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2020] [Revised: 08/16/2020] [Accepted: 08/24/2020] [Indexed: 11/21/2022]
Abstract
Regression after corneal refractive surgery is a complex phenomenon which seems inevitable. The choice of surgical technique has very little influence on regression for low myopia or myopic astigmatism. However, LASIK and SMILE are the two techniques of choice in the correction of high myopia. LASIK is also better for the correction of hyperopia, hyperopic astigmatism and mixed astigmatism. Intraoperatively, the choice of a wide optical zone and adherence to a thick residual stromal bed provide stability. Regression may also be reduced by modulating anti-inflammatory therapy, treating dry eye, and using mitomycin C in PKR. In all cases, obtaining keratometry during patient follow-up helps to identify the cause of the regression. The objective of this review is to synthesize recent data from the literature on regression in refractive surgery as a function of the ablation profiles used.
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Kim JY, Lee H, Joo CK, Hyon JY, Kim TI, Kim JH, Kim JK, Cho EY, Choi JE, Lee NR, Tchah HW. Three-Year Follow-Up of Laser In Situ Keratomileusis Treatments for Myopia: Multi-Center Cohort Study in Korean Population. J Pers Med 2021; 11:jpm11050419. [PMID: 34065718 PMCID: PMC8156820 DOI: 10.3390/jpm11050419] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2021] [Revised: 05/03/2021] [Accepted: 05/08/2021] [Indexed: 11/16/2022] Open
Abstract
This multi-center cohort study included 3401 myopic laser in situ keratomileusis (LASIK) procedures conducted in 1756 myopia patients between 2002 and 2005. Pre- and postoperative uncorrected visual acuity (UCVA), best corrected visual acuity (BCVA), and manifest refraction spherical equivalent (SE) were recorded. Factors predicting low postoperative efficacy (defined as a postoperative UCVA < 0.5) were identified using univariate and multivariate logistic regression analysis. Compared with 1 month postoperatively, logMAR UCVA at 3 months postoperatively was significantly decreased (p = 0.002) and that at 2 and 3 years was significantly increased (p < 0.001). LogMAR BCVA at 2 years postoperatively was significantly decreased compared with 1 month postoperatively (p = 0.008). Over the 3-year postoperative period, overall refractive predictability within ±1.00 D and ±0.50 D ranged from 69.0% to 86.2% and from 43.3% to 67.8%, respectively. This also decreased from 1 month to 6 months postoperatively (p < 0.005). Multivariate logistic regression analysis using generalized estimating equations, revealed that higher preoperative SE (odds ratio [OR], 2.58 and 7.23; p < 0.001) and lower preoperative BCVA (OR, 2.44; p = 0.003) were predictive of a low postoperative efficacy. In summary, myopic LASIK can be effective and safe with a high refractive predictability in a Korean population, but myopic regression occurs over time. Higher preoperative SE and lower preoperative BCVA are predictive of a low postoperative efficacy.
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Affiliation(s)
- Jae-Yong Kim
- Department of Ophthalmology, Asan Medical Center, University of Ulsan College of Medicine, Seoul 05505, Korea; (J.-Y.K.); (H.L.)
| | - Hun Lee
- Department of Ophthalmology, Asan Medical Center, University of Ulsan College of Medicine, Seoul 05505, Korea; (J.-Y.K.); (H.L.)
| | - Choun-Ki Joo
- Department of Ophthalmology and Visual Science, Kangnam St. Mary’s Hospital, College of Medicine, The Catholic University of Korea, Seoul 06591, Korea;
| | - Joon-Young Hyon
- Department of Ophthalmology, Seoul National University College of Medicine, Seoul National University Bundang Hospital, Seongnam 13620, Korea;
| | - Tae-Im Kim
- Department of Ophthalmology, Institute of Vision Research, Corneal Dystrophy Research Institute, Yonsei University College of Medicine, Seoul 03722, Korea;
| | - Jin-Hyoung Kim
- Department of Ophthalmology, Ilsan Paik Hospital, Inje University of Korea, Koyang 10380, Korea;
| | - Jin-Kuk Kim
- B&VIIT Eye Center, Seoul 06615, Korea; (J.-K.K.); (E.-Y.C.)
| | - Eun-Young Cho
- B&VIIT Eye Center, Seoul 06615, Korea; (J.-K.K.); (E.-Y.C.)
| | - Ji-Eun Choi
- National Evidence-Based Healthcare Collaborating Agency, Seoul 04554, Korea; (J.-E.C.); (N.-R.L.)
| | - Na-Rae Lee
- National Evidence-Based Healthcare Collaborating Agency, Seoul 04554, Korea; (J.-E.C.); (N.-R.L.)
| | - Hung-Won Tchah
- Department of Ophthalmology, Asan Medical Center, University of Ulsan College of Medicine, Seoul 05505, Korea; (J.-Y.K.); (H.L.)
- Correspondence:
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Brar S, Gautam M, Sute SS, Ganesh S. Refractive surgery with simultaneous collagen cross-linking for borderline corneas - A review of different techniques, their protocols and clinical outcomes. Indian J Ophthalmol 2020; 68:2744-2756. [PMID: 33229650 PMCID: PMC7856924 DOI: 10.4103/ijo.ijo_1709_20] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
Simultaneous corneal cross-linking (CXL) has been proposed as an adjunct therapy to corneal refractive procedures to prevent future ectasia, especially when performed in borderline corneas. This review analyses the currently available literature (minimum follow-up 6 months) on corneal refractive surgery and simultaneous CXL (PRK Xtra, LASIK Xtra, and SMILE Xtra) to evaluate the overall results including the safety, efficacy, and potential complications associated with these procedures. A comprehensive literature search of various electronic databases (PubMed, PubMed Central, Cochrane database, and MEDLINE) was performed up to 20th May 2020. Four relevant studies were found for PRK Xtra, 12 for LASIK Xtra, and 3 for SMILE Xtra. The total number of eyes included in this review was 1,512: 294 for PRK Xtra, 221 for PRK-only, 446 eyes for LASIK Xtra, 398 eyes for LASIK-only, 91 for SMILE Xtra and 62 for SMILE-only. Current literature suggests that refractive surgery and simultaneous CXL is generally safe and delivers comparable results in terms of visual and refractive outcomes than refractive surgery alone. However, there is no consensus on a standard cross-linking protocol, and complications such as diffuse lamellar keratitis, central toxic keratopathy, and corneal ectasia following Xtra procedures have been reported. It is therefore suggested that surgeons exercise caution in case-selection and counsel their patients regarding the potential risks and benefits with Xtra procedures. Also, further studies are required to standardize the UV-A irradiation protocols and to evaluate the long-term effect on safety, refractive predictability, and stability of these procedures.
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Affiliation(s)
- Sheetal Brar
- Nethradhama Superspeciality Eye Hospital, Bengaluru, Karnataka, India
| | - Megha Gautam
- Nethradhama Superspeciality Eye Hospital, Bengaluru, Karnataka, India
| | - Smith Snehal Sute
- Nethradhama Superspeciality Eye Hospital, Bengaluru, Karnataka, India
| | - Sri Ganesh
- Nethradhama Superspeciality Eye Hospital, Bengaluru, Karnataka, India
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Lim L, Lim EWL, Rosman M, Koh JCW, Htoon HM. Three-Year Outcomes of Simultaneous Accelerated Corneal Crosslinking and Femto-LASIK for the Treatment of High Myopia in Asian Eyes. Clin Ophthalmol 2020; 14:2865-2872. [PMID: 33061271 PMCID: PMC7526743 DOI: 10.2147/opth.s260088] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2020] [Accepted: 06/12/2020] [Indexed: 11/24/2022] Open
Abstract
Purpose To determine the long-term visual outcomes of simultaneous femtosecond laser-assisted laser in situ keratomileusis (femto-LASIK) and accelerated cross-linking (CXL) [LASIK Xtra] for the treatment of high myopia. Patients and Methods All 163 consecutive eyes of 85 patients who underwent LASIK Xtra for the treatment of high myopia and/or myopic astigmatism (spherical equivalent ≥ −6.00 D) in Singapore National Eye Centre from the years 2013 to 2017 were included in this retrospective case series. Post-operative follow-up was up to 3 years. Results Of the 163 eyes, 67 were followed up for 1 year (mean 12.9 months), 69 for 2 years (mean 24.0 months) and 43 for 3 years (mean 36.4 months). Overall mean follow-up was 22.8 months (9–46 months). The mean pre-operative spherical equivalent (SE) was −8.60 ± 1.47 D [range: −11.75 to −4.75] (n = 163) and mean attempted correction SE was −8.84 ± 1.41 D [range: −11.88 to −5.25]. Most eyes (>95%) maintained an uncorrected distance visual acuity of 6/12 or better over 3 years. Visual outcomes were predictable with ≥95% of eyes achieving a SE correction within ± 1D of attempted correction over 3 years. There was a mild regression in SE refraction over 3 years with a mean of −0.10 ± 0.45 D three years post-operatively (p = 0.03). The safety index was >1.05 at 3 years follow-up. There were no significant post-operative complications though 24 eyes had mild haze and 2 eyes had grade 1 diffuse lamellar keratitis that resolved within 1 month. Conclusion Our 3-year LASIK Xtra results show favorable safety, efficacy, predictability and stability outcomes in Asian patients with high myopia.
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Affiliation(s)
- Li Lim
- Singapore National Eye Centre, Singapore 168751, Singapore.,Singapore Eye Research Institute, Singapore 169856, Singapore.,Duke-NUS Medical School, Singapore 169857, Singapore
| | - Elizabeth Wen Ling Lim
- Yong Loo Lin School of Medicine, National University of Singapore, Singapore 119228, Singapore
| | - Mohamad Rosman
- Singapore National Eye Centre, Singapore 168751, Singapore.,Singapore Eye Research Institute, Singapore 169856, Singapore.,Duke-NUS Medical School, Singapore 169857, Singapore
| | | | - Hla Myint Htoon
- Singapore National Eye Centre, Singapore 168751, Singapore.,Duke-NUS Medical School, Singapore 169857, Singapore
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10
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Correlation and regression analysis between residual gradation and uncorrected visual acuity one year after refractive surgery with LASIK, FS-LASIK, PRK, PRK Xtra techniques and the implantation of ICL® posterior chamber phakic lens in myopic correction. PLoS One 2020; 15:e0238399. [PMID: 32915816 PMCID: PMC7485817 DOI: 10.1371/journal.pone.0238399] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2020] [Accepted: 08/15/2020] [Indexed: 11/19/2022] Open
Abstract
Purpose To analyze the influence of the final spherical equivalent (SE) in LogMAR uncorrected distance visual acuity (UDVA) one year after refractive surgery. We analysed refractive results, their predictability and efficacy, and the safety results of the different methods as secondary outcomes. Setting Refractive Surgery Unit of the Institut Català de Retina (ICR) in Barcelona, Spain. Design Retrospective, analytical observational study. Methods Retrospective and observational study of 654 eyes of 327 patients who underwent refractive surgery to treat their myopia or myopic astigmatism using LASIK, FS-LASIK, PRK, PRK Xtra or ICL-type lens implantation surgery were included. Results The correlation between the SE in absolute value was statistically significant in all techniques utilized, reaching higher values in the FS-LASIK and LASIK techniques, 0.774 and 0.706 respectively, and lesser values in PRK (0.480) and PRK Xtra (0.482). A significant adjustment via a univariate linear regression model could be implemented in all techniques, albeit the R2 coefficient of determination values were higher than those for the FS-LASIK (0.599) and LASIK (0.494) techniques. Conclusions There is a positive correlation between post-surgical SE value and post-operative LogMAR UDVA. These regression models can be adjusted to predict the final UDVA according to the final SE. The techniques that are most influenced by the final SE in terms of their visual results are FS-LASIK and LASIK.
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Bamashmus MA, Al-Akhlee HA, Al-Azani YA, Al-Kershy NA. Results of laser enhancement for residual myopia after primary laser in situ keratomileusis. Taiwan J Ophthalmol 2019; 10:264-268. [PMID: 33437599 PMCID: PMC7787091 DOI: 10.4103/tjo.tjo_32_19] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2019] [Accepted: 07/14/2019] [Indexed: 11/24/2022] Open
Abstract
PURPOSE: The purpose of the study is to evaluate and analyze the results and outcomes after laser enhancement for residual myopia after primary laser in situ keratomileusis (LASIK). MATERIALS AND METHODS: This retrospective interventional consecutive case series clinical study was performed on 112 consecutive eyes (82 patients) that had undergone primary LASIK before the enhancement procedure. The study was done in the Refractive Surgery Unit in Yemen Magrabi Hospital between 2006 and 2014. The retreatment was for residual myopia with or without astigmatism. Either the original flap was lifted or surface ablation was performed. Parameters evaluated were uncorrected visual acuity (UCVA) and best spectacle-corrected visual acuity (VA), spherical equivalent (SE) refraction, corneal topography, and pachymetry. Complications after laser enhancement were also evaluated. RESULTS: Mean age of the study group was 26.72 ± 6.89 years (range from 18 to 44 years). Males accounted for 37/82 (45.1%) and females for 45/82 (54.9%). The right eye was treated in 67/112 (59.8%) and the left eye in 45/112 (40.2%). Before primary LASIK, the mean SE (MSE) was −5.78 ± 1.89 D. Before enhancement, the MSE was −1.32 ± 0.61 D (range −3.25 D to −0.50 D), and none of the eyes had an UCVA of 20/40 or better. Twelve months after retreatment, the percentage of eyes having UCVA of 20/40 or better increased to 67.9% (76 of 112). There were no vision-threatening complications seen. CONCLUSION: Retreatment or enhancement after LASIK surgery by lifting the original flap or surface ablation is a safe and effective method for the treatment of regressed or undercorrected myopia. The risk of postoperative complications is very minimal.
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Affiliation(s)
- Mahfouth A Bamashmus
- Eye Department, Faculty of Medicine and Health Sciences, Sana'a University, Sana'a, Yemen.,Refractive Surgery Unit, Magrabi Eye Hospital, Sana'a, Yemen
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12
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Ong HS, Farook M, Tan BBC, Williams GP, Santhiago MR, Mehta JS. Corneal Ectasia Risk And Percentage Tissue Altered In Myopic Patients Presenting For Refractive Surgery. Clin Ophthalmol 2019; 13:2003-2015. [PMID: 31686775 PMCID: PMC6798818 DOI: 10.2147/opth.s215144] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2019] [Accepted: 08/13/2019] [Indexed: 01/01/2023] Open
Abstract
Purpose A percentage tissue altered (PTA) score of ≥40% has been advocated as an independent indicator of post-operative ectasia risk following laser in-situ keratomileusis (LASIK). This study was performed to test the hypothesis that refractive procedures, such as laser-assisted sub-epithelial keratectomy (LASEK) or small incision lenticule extraction (SMILE), may alter the range of PTA, within which refractive corneal surgery can be safely performed. Setting Refractive department, tertiary ophthalmic hospital. Design Retrospective observational study. Methods Review of case notes was performed for patients who presented for refractive surgeries, other than LASIK. To determine the risk of corneal ectasia for each patient prior to refractive surgery, we estimated what each patient’s PTA would have been if they had undergone LASIK. The Randleman Ectasia Risk Score System (ERSS) was also calculated. Results 114 eyes (66 patients) were included. 94 eyes underwent SMILE. 20 eyes underwent LASEK. A significant proportion of eyes had PTA ≥40% – SMILE eyes: up to 31.9%, LASEK eyes: up to 60.0% (at presumed LASIK flap of 120 μm). The maximum calculated PTA was up to 47.9% in the SMILE group and up to 51.5% in the LASEK group. Using ERSS, 12.8–16% of SMILE eyes and 15.0–80.0% of LASEK eyes would have been considered to have moderate-to-high ectasia risk. No post-surgical ectasia was observed at 3 years. Conclusion SMILE and LASEK alter the range of PTA, within which corneal refractive surgery may be performed with a lower risk of developing post-operative corneal ectasia; a safe PTA threshold needs to be determined for these procedures before recommendations for clinical practice can be made.
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Affiliation(s)
- Hon Shing Ong
- Department of Corneal and External Diseases, Singapore National Eye Centre, Singapore, Singapore.,Tissue Engineering and Stem Cell Group, Singapore Eye Research Institute, Singapore, Singapore.,SingHealth Duke-NUS Ophthalmology and Visual Sciences Academic Clinical Programme, Duke-NUS Graduate Medical School, Singapore, Singapore
| | - Mohamed Farook
- Department of Corneal and External Diseases, Singapore National Eye Centre, Singapore, Singapore
| | - Benjamin Boon Chuan Tan
- Department of Corneal and External Diseases, Singapore National Eye Centre, Singapore, Singapore
| | - Geraint P Williams
- Department of Corneal and External Diseases, Singapore National Eye Centre, Singapore, Singapore.,Tissue Engineering and Stem Cell Group, Singapore Eye Research Institute, Singapore, Singapore
| | - Marcony R Santhiago
- Department of Ophthalmology, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil.,Department of Ophthalmology, University of Sao Paulo, Sao Paulo, Brazil
| | - Jodhbir S Mehta
- Department of Corneal and External Diseases, Singapore National Eye Centre, Singapore, Singapore.,Tissue Engineering and Stem Cell Group, Singapore Eye Research Institute, Singapore, Singapore.,SingHealth Duke-NUS Ophthalmology and Visual Sciences Academic Clinical Programme, Duke-NUS Graduate Medical School, Singapore, Singapore.,School of Material Science and Engineering, Nanyang Technological University, Singapore, Singapore
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Lim EWL, Lim L. Review of Laser Vision Correction (LASIK, PRK and SMILE) with Simultaneous Accelerated Corneal Crosslinking - Long-term Results. Curr Eye Res 2019; 44:1171-1180. [PMID: 31411927 DOI: 10.1080/02713683.2019.1656749] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
Purpose: Laser in-situ keratomileusis (LASIK), photorefractive keratectomy (PRK) and small-incision lenticule extraction (SMILE) are safe and effective refractive surgical procedures. However, complications include regression of treatment and iatrogenic keratectasia which can be severe and sight-threatening. In order to reduce these complications, simultaneous corneal cross-linking (CXL) is currently being added to these refractive procedures. This review analyses current long-term literature (≥ 1 year follow-up) on refractive surgery and simultaneous CXL (LASIK Xtra, PRK Xtra and SMILE Xtra) to determine its overall safety and efficacy.Methods: A comprehensive literature search of various electronic databases (PubMed, PubMed Central and MEDLINE) was performed up to 9th February 2019. Efficacy and safety indices are calculated where possible.Results: Ten relevant studies were found for LASIK Xtra, 4 for PRK Xtra and 1 for SMILE Xtra. The total number of eyes included in this review was 1,189: 347 eyes for LASIK Xtra, 300 eyes for LASIK-only, 298 for PRK Xtra, 204 for PRK-only, 40 for SMILE Xtra and none for SMILE-only. Current studies show that refractive surgery and simultaneous CXL produces comparable or better results in terms of refractive and keratometric stability than refractive surgery alone. However, case reports of complications such as corneal ectasia, diffuse lamellar keratitis and central toxic keratopathy have also recently been published.Conclusions: Simultaneous accelerated CXL and refractive surgery is effective for the treatment of myopia. However, it is as yet unclear if the additional CXL step reduces the incidence of iatrogenic keratectasia. Further long-term comparative studies would be useful in evaluating safety and efficacy of this procedure. More research should also be performed to titrate the UV-A irradiation settings for an optimal outcome.
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Affiliation(s)
| | - Li Lim
- Department of Corneal and External Eye Disease, Singapore National Eye Centre, Singapore.,Adjunct Clinical Investigator, Singapore Eye Research Institute, Singapore.,Adjunct Associate Professor, Ophthalmology and Visual Sciences Academic Clinical Programme, Duke-NUS Medical School, Singapore
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14
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Liu M, Gao H, Shi W. Factors Affecting Myopic Regression after Laser in Situ Keratomileusis and Laser-Assisted Subepithelial Keratectomy for High Myopia. Semin Ophthalmol 2019; 34:359-364. [PMID: 31257965 DOI: 10.1080/08820538.2019.1632353] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
To evaluate the factors affecting the amount of myopic regression after laser refractive surgery for high myopia, we retrospectively reviewed medical records of 1591 eyes with high myopia treated by laser in situ keratomileusis or laser-assisted subepithelial keratectomy at Shandong Eye Hospital between January 2008 and December 2012. Thirty-five eyes suffering a postoperative myopic shift of manifest spherical equivalent (MSE) of 0.25 diopter (D) or greater were included in this study. The mean refractive error was -9.34 ± 1.89 D before surgery, and the mean regression was -1.22 ± 0.70 D. Correlation analysis and multiple regression analysis were performed to assess the factors that were associated with the refractive regression. The age displayed a negative correlation with the diopter of regression (R = -0.404, P = .016), while the optical zone diameter had a positive correlation with it (R = 0.406, P = .016). Explanatory variables relevant to the diopter of regression were age (partial regression coefficient B = -0.045, P = .016) and optical zone diameter (partial regression coefficient B = 0.979, P = .014). Advanced-age patients with small optical zones were more predisposed to a larger amplitude of regression after laser refractive surgery for high myopia.
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Affiliation(s)
- Mingna Liu
- a Refractive Surgery Department, Shandong Eye Hospital, Shandong Eye Institute, Shandong Academy of Medical Sciences , Jinan , China
| | - Hua Gao
- a Refractive Surgery Department, Shandong Eye Hospital, Shandong Eye Institute, Shandong Academy of Medical Sciences , Jinan , China
| | - Weiyun Shi
- a Refractive Surgery Department, Shandong Eye Hospital, Shandong Eye Institute, Shandong Academy of Medical Sciences , Jinan , China
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15
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Tabacaru B, Stanca HT. One year refractive outcomes of Femtosecond-LASIK in mild, moderate and high myopia. Rom J Ophthalmol 2018; 61:23-31. [PMID: 29450367 PMCID: PMC5710049 DOI: 10.22336/rjo.2017.5] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Purpose: To evaluate the safety, efficacy, predictability and stability for a cohort of myopic eyes treated by Femtosecond-LASIK procedure. Methods: 60 eyes (36 patients) with different degrees of myopia that underwent refractive surgery by using the Femtosecond-LASIK technique were prospectively evaluated for 12 months. The mean preoperative spherical equivalent value was –3.827 ± 1.410 diopters (D) (range: –8.125 to –1.375 D). VisuMax® femtosecond laser was used for cutting the corneal flap and then the Mel80® excimer laser for the stromal ablation. Results: Mean age was 30.80 ± 5.745 years (range: 21 to 46 years) with 75% female patients. Postoperative spherical equivalent at 12 months was within ±0.25 D of emmetropia in 90% of the eyes and within ±0.50 D of emmetropia in 100% of the eyes. All the eyes achieved an uncorrected distance visual acuity (UDVA) of 1.0 (decimal scale). No eye lost lines of preoperative corrected distance visual acuity (CDVA). No major intraoperative or postoperative complications were encountered. Conclusions: Femtosecond-LASIK seems to be a suitable option for the correction of mild, moderate, and high myopia, as the procedure showed to be safe, effective, and predictable for the treatment of myopic refractive errors.
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Affiliation(s)
- Bogdana Tabacaru
- "Prof. Dr. Agrippa Ionescu" Emergency Hospital, Bucharest, Romania.,"Carol Davila" University of Medicine and Pharmacy, Bucharest, Romania
| | - Horia Tudor Stanca
- "Prof. Dr. Agrippa Ionescu" Emergency Hospital, Bucharest, Romania.,"Carol Davila" University of Medicine and Pharmacy, Bucharest, Romania.,"Metropolitan" Hospital, Bucharest, Romania
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16
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Riau AK, Liu YC, Lim CHL, Lwin NC, Teo EP, Yam GH, Tan DT, Mehta JS. Retreatment strategies following Small Incision Lenticule Extraction (SMILE): In vivo tissue responses. PLoS One 2017; 12:e0180941. [PMID: 28708898 PMCID: PMC5510831 DOI: 10.1371/journal.pone.0180941] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2016] [Accepted: 06/10/2017] [Indexed: 11/30/2022] Open
Abstract
With any refractive correction, including Small Incision Lenticule Extraction (SMILE), there may be a residual refractive error that requires a retreatment. Here, we investigated the tissue responses following various retreatment procedures in a rabbit model of SMILE. All rabbits underwent a -6.00D correction with SMILE. Two weeks later, they underwent -1.00D enhancement by: (i) VisuMax Circle, followed by excimer ablation (S+C); (ii) secondary SMILE anterior to the primary procedure (S+SE); or (iii) surface ablation (S+P), and were examined for 28 days. S+P induced corneal edema and haze, and more CD11b- (23±6 cells) and TUNEL-positive (36±4 cells) cells in the central stromal superficial layers early post-operatively (p<0.001 compared to other procedures). The corneas appeared normal on day 28 after S+P, but had a lower number of keratocytes near the laser ablated plane compared to other procedures. S+SE and S+C did not induce corneal haze and resulted similar level of fibronectin. However, S+C resulted in more inflammatory (10±2 cells; p = 0.001) and apoptotic cells (25±2 cells; p<0.001) compared to S+SE (7±1 inflammatory cells and 21±3 apoptotic cells) early post-operatively. In conclusion, each SMILE retreatment method resulted in unique tissue responses. S+SE offers advantages, such as minimal inflammation and cell death, as well as maintaining a ‘flap-less’ surgery, over other procedures. However, depending on the degree of enhancement, the lenticule may become too thin to be extracted and the procedure becomes more difficult to perform than S+C and S+P. S+P can maintain corneal integrity by avoiding flap creation and is technically more simple to perform than the others, but the surgery needs to be supplemented with mitomycin-C in order to reduce inflammation and modulate better wound healing.
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Affiliation(s)
- Andri K. Riau
- Tissue Engineering and Stem Cell Group, Singapore Eye Research Institute, Singapore
| | - Yu-Chi Liu
- Tissue Engineering and Stem Cell Group, Singapore Eye Research Institute, Singapore
- Singapore National Eye Centre, Singapore
| | - Chris H. L. Lim
- Tissue Engineering and Stem Cell Group, Singapore Eye Research Institute, Singapore
- Singapore National Eye Centre, Singapore
- Royal Melbourne Hospital, Melbourne, Australia
- Department of Ophthalmology, National University Health System, Singapore
| | - Nyein C. Lwin
- Tissue Engineering and Stem Cell Group, Singapore Eye Research Institute, Singapore
| | - Ericia P. Teo
- Tissue Engineering and Stem Cell Group, Singapore Eye Research Institute, Singapore
| | - Gary H. Yam
- Tissue Engineering and Stem Cell Group, Singapore Eye Research Institute, Singapore
- Ophthalmology Academic Clinical Program, Duke-NUS Graduate Medical School, Singapore
| | - Donald T. Tan
- Tissue Engineering and Stem Cell Group, Singapore Eye Research Institute, Singapore
- Singapore National Eye Centre, Singapore
- Ophthalmology Academic Clinical Program, Duke-NUS Graduate Medical School, Singapore
| | - Jodhbir S. Mehta
- Tissue Engineering and Stem Cell Group, Singapore Eye Research Institute, Singapore
- Singapore National Eye Centre, Singapore
- Ophthalmology Academic Clinical Program, Duke-NUS Graduate Medical School, Singapore
- Department of Clinical Sciences, Duke-NUS Graduate Medical School, Singapore
- * E-mail:
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Twelve-Year Follow-Up of Laser In Situ Keratomileusis for Moderate to High Myopia. BIOMED RESEARCH INTERNATIONAL 2017; 2017:9391436. [PMID: 28596969 PMCID: PMC5449750 DOI: 10.1155/2017/9391436] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/14/2017] [Accepted: 04/09/2017] [Indexed: 11/18/2022]
Abstract
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.
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18
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Mori Y, Miyata K, Ono T, Yagi Y, Kamiya K, Amano S. Comparison of laser in situ ketatomileusis and photorefractive keratectomy for myopia using a mixed-effects model. PLoS One 2017; 12:e0174810. [PMID: 28362808 PMCID: PMC5375153 DOI: 10.1371/journal.pone.0174810] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2016] [Accepted: 03/15/2017] [Indexed: 11/18/2022] Open
Abstract
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.
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Affiliation(s)
| | | | | | | | - Kazutaka Kamiya
- Department of Ophthalmology, University of Kitasato School of Medicine, Kanagawa, Japan
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19
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Chung B, Lee H, Choi BJ, Seo KR, Kim EK, Kim DY, Kim TI. Clinical Outcomes of an Optimized Prolate Ablation Procedure for Correcting Residual Refractive Errors Following Laser Surgery. KOREAN JOURNAL OF OPHTHALMOLOGY 2017; 31:16-24. [PMID: 28243019 PMCID: PMC5327170 DOI: 10.3341/kjo.2017.31.1.16] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2015] [Accepted: 11/30/2015] [Indexed: 11/23/2022] Open
Abstract
Purpose 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. Methods 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. Results 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. Conclusions 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.
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Affiliation(s)
- Byunghoon Chung
- The Institute of Vision Research, Department of Ophthalmology, Yonsei University College of Medicine, Seoul, Korea
| | - Hun Lee
- The Institute of Vision Research, Department of Ophthalmology, Yonsei University College of Medicine, Seoul, Korea
| | | | - Kyung Ryul Seo
- The Institute of Vision Research, Department of Ophthalmology, Yonsei University College of Medicine, Seoul, Korea
| | - Eung Kwon Kim
- The Institute of Vision Research, Department of Ophthalmology, Yonsei University College of Medicine, Seoul, Korea.; Corneal Dystrophy Research Institute, Severance Biomedical Science Institute, and Brain Korea 21 Project for Medical Science, Department of Ophthalmology, Yonsei University College of Medicine, Seoul, Korea
| | | | - Tae-Im Kim
- The Institute of Vision Research, Department of Ophthalmology, Yonsei University College of Medicine, Seoul, Korea
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Moshirfar M, Jehangir N, Fenzl CR, McCaughey M. LASIK Enhancement: Clinical and Surgical Management. J Refract Surg 2017; 33:116-127. [DOI: 10.3928/1081597x-20161202-01] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2015] [Accepted: 04/26/2016] [Indexed: 11/20/2022]
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21
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Kim B, Mun S, Choi H, Yang Y, Chung Y. Comparison of the Early Clinical Outcomes between Combined SMILE and Collagen Cross-linking versus SMILE. JOURNAL OF THE KOREAN OPHTHALMOLOGICAL SOCIETY 2017. [DOI: 10.3341/jkos.2017.58.10.1122] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Affiliation(s)
- Buki Kim
- Onnuri Smile Eye Clinic, Seoul, Korea
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Ogasawara K, Onodera T. Residual stromal bed thickness correlates with regression of myopia after LASIK. Clin Ophthalmol 2016; 10:1977-1981. [PMID: 27784987 PMCID: PMC5066994 DOI: 10.2147/opth.s116498] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/02/2022] Open
Abstract
Purpose The purpose of this study was to evaluate the correlation between residual stromal bed thickness (hereinafter bed thickness) and regression of myopia after LASIK, taking into consideration the long-term outcomes. Subjects and methods A total of 177 patients (309 eyes) and 41 patients (70 eyes) were retrospectively reviewed at 5 and 10 years after surgery, respectively. These patients were also continuously examined throughout the study. All patients underwent laser in situ keratomileusis (LASIK) for myopia in our clinic and scored at least 1.0 (0 logMAR) uncorrected distance visual acuity (UCVA) 1 month after surgery. Bonferroni–Dunn method and Student’s t-test were used for statistical analyses. Results Cases with a refractive value (spherical equivalent) of less than −6.0 D (Group A) were compared to those with −6.1 D or higher (Group B). There was a statistically significant decrease in Group B UCVA of 0.04 logMAR and 0.12 logMAR at 5 and 10 years after surgery, respectively. With regard to the relationship between regression of myopia and bed thickness in the long-term, there was a significantly higher frequency of regression of myopia in cases with less than 350 μm bed thickness compared to those with 350 μm and more, in a surgical volume of more than −6.1 D (Group B). Conclusion The present study indicates that bed thickness correlates with regression of myopia after LASIK and enough bed thickness is important to maintain good UCVA in the long-term.
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Chan TCY, Yu MCY, Mak S, Jhanji V. Longitudinal comparison of femtosecond-assisted sub-Bowman keratomileusis versus photorefractive keratectomy for high myopia. Br J Ophthalmol 2016; 101:275-282. [DOI: 10.1136/bjophthalmol-2016-308642] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/29/2016] [Revised: 05/04/2016] [Accepted: 05/15/2016] [Indexed: 11/04/2022]
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Kim HW, Na KS, Kim MS. Comparison of 10-year Clinical Results between Laser in situKeratomileusis and Surface Ablation for Moderate to High Myopia. JOURNAL OF THE KOREAN OPHTHALMOLOGICAL SOCIETY 2016. [DOI: 10.3341/jkos.2016.57.3.380] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Affiliation(s)
- Hyo Won Kim
- Department of Ophthalmology and Visual Science, College of Medicine, The Catholic University of Korea, Seoul, Korea
| | - Kyung Sun Na
- Department of Ophthalmology and Visual Science, College of Medicine, The Catholic University of Korea, Seoul, Korea
| | - Man Soo Kim
- Department of Ophthalmology and Visual Science, College of Medicine, The Catholic University of Korea, Seoul, Korea
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Ayar O, Ozmen MC, Muftuoglu O, Akdemir MO, Koc M, Ozulken K. In-vivo corneal biomechanical analysis of unilateral keratoconus. Int J Ophthalmol 2015; 8:1141-5. [PMID: 26682162 DOI: 10.3980/j.issn.2222-3959.2015.06.11] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2014] [Accepted: 03/17/2015] [Indexed: 11/02/2022] Open
Abstract
AIM To evaluate and compare corneal biomechanical findings measured by ocular response analyzer, topographic and pachymetric findings in patients with unilateral keratoconus patients and healthy controls. METHODS This is an observational, case-control study. Patients with keratoconus in one eye and forme fruste keratoconus in the fellow eye were compared with sex and age matched with controls healthy subjects. All subjects were evaluated with rotating scheimpflug imaging system. The receiver-operating-characteristic curves were analyzed to evaluate the sensitivity and specificity of the parameters. RESULTS Twenty-seven patients with keratoconus in one eye and forme fruste keratoconus in the fellow eye were compared with 40 eyes of 40 normal subjects. Corneal hysteresis (CH) was 8.0±1.7 mm Hg in keratoconus group, 8.3±1.6 mm Hg in forme fruste keratoconus group, and 9.8±1.6 mm Hg in control groups (P=0.54 between keratoconus and forme fruste keratoconus groups, P<0.01 between control group and other groups). Corneal resistance factor (CRF) was 7.1±2.2 mm Hg in keratoconus group, 7.8±1.2 mm Hg in forme fruste keratoconus group and 9.9±1.5 mm Hg in control group (P<0.001 between control group and other groups). Using receiver-operating-characteristic analysis, the area under curve values of the parameters to distinguish forme fruste keratoconus from control subjects were: CH (0.768), CRF (0.866). Best cut-off points were 9.3 mm Hg and 8.8 mm Hg for CH and CRF respectively. CONCLUSION Ocular response analyzer parameters (CH and CRF) are found to be significantly lower in forme fruste keratoconus patients compared to normal control subjects.
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Affiliation(s)
- Orhan Ayar
- Department of Ophthalmology, Bulent Ecevit University, Kozlu 67600, Zonguldak, Turkey
| | | | - Orkun Muftuoglu
- Department of Ophthalmology, Medipol University, Istanbul 34214, Turkey
| | - Mehmet Orcun Akdemir
- Department of Ophthalmology, Bulent Ecevit University, Kozlu 67600, Zonguldak, Turkey
| | - Mustafa Koc
- Ulucanlar Eye Research and Education Hospital, Ankara 06340, Turkey
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Clinical Outcomes of Small Incision Lenticule Extraction with Accelerated Cross-Linking (ReLEx SMILE Xtra) in Patients with Thin Corneas and Borderline Topography. J Ophthalmol 2015. [PMID: 26221538 PMCID: PMC4499409 DOI: 10.1155/2015/263412] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Purpose. To study the safety and clinical outcomes of ReLEx SMILE with accelerated cross-linking in individuals with thinner corneas, borderline topography, and higher refractive errors. Methods. Eligible patients first underwent SMILE procedure for correction of myopic refractive error. Following the removal of lenticule, 0.25% riboflavin in saline was injected into the interface and allowed to diffuse for 60 seconds. Finally, eye was exposed to UV-A radiation of 45 mW/cm2 for 75 seconds through the cap. Total energy delivered was 3.4 J/cm2. Results. 40 eyes of 20 patients with mean age of 26.75 ± 5.99 years were treated. Mean follow-up was 12 months ± 28.12 days. Mean spherical equivalent (SE) was −5.02 ± 2.06 D preoperatively and −0.24 ± 0.18 D postoperatively. The mean central corneal thickness (CCT) and keratometry changed from 501 ± 25.90 µm to 415 ± 42.26 µm and 45.40 ± 1.40 D to 41.2 ± 2.75 D, respectively. Mean uncorrected visual acuity (UCVA) was 20/25 or better in all eyes. No eyes lost lines of corrected distant visual acuity (CDVA). There were no complications like haze, keratitis, ectasia, or regression. Conclusion. Based on the initial clinical outcome it appears that SMILE Xtra may be a safe and feasible modality to prevent corneal ectasia in susceptible individuals.
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Tan J, Lytle GE, Marshall J. Consecutive laser in situ keratomileusis and accelerated corneal crosslinking in highly myopic patients: preliminary results. Eur J Ophthalmol 2014; 25:0. [PMID: 25588591 DOI: 10.5301/ejo.5000543] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/30/2014] [Indexed: 11/20/2022]
Abstract
PURPOSE To report the preliminary results of an evaluation of the safety and predictability of Lasik Xtra, a technique combining laser in situ keratomileusis (LASIK) and accelerated corneal crosslinking, in highly myopic patients. METHODS In this consecutive comparative case series, 70 consecutive eyes undergoing LASIK for correction of high myopia (-8.00 D to -19.00 D manifest refractive spherical equivalent) were prospectively recruited and treated with Lasik Xtra and compared with a retrospective consecutive control group of 64 eyes who had undergone LASIK alone for correction of high myopia. The follow-up was 3 months. Outcome measures included uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), and refraction. RESULTS A total of 61% of LASIK only eyes achieved UDVA of 20/25 or better, compared to 98% of Lasik Xtra eyes (p<0.001) at 3 months. A greater percentage of eyes were within ±0.50 of the intended correction in the Lasik Xtra group (88%) than in the LASIK only group (65%) at 3 months (p = 0.005). Linear regression of the scatterplot of attempted versus achieved correction reveals a coefficient of determination of 0.83 in the LASIK only group vs 0.99 in the Lasik Xtra group. A trend (p = 0.051) towards greater refractive drift in the LASIK group (-0.13 D) vs the Lasik Xtra group (-0.04 D) was observed. No adverse events were observed in either group. CONCLUSIONS Lasik Xtra did not reduce the refractive accuracy of the LASIK procedure. The addition of crosslinking may induce early stabilization of the cornea after LASIK, improving the predictability of refractive outcomes in highly myopic subjects.
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Ide T, Toda I, Fukumoto T, Watanabe J, Tsubota K. Outcome of a 10-year follow-up of laser in situ laser keratomileusis for myopia and myopic astigmatism. Taiwan J Ophthalmol 2014. [DOI: 10.1016/j.tjo.2014.06.002] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
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Alió JL, Soria F, Abbouda A, Peña-García P. 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. J Cataract Refract Surg 2014; 41:33-40. [PMID: 25465210 DOI: 10.1016/j.jcrs.2014.08.029] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2013] [Revised: 08/05/2014] [Accepted: 08/19/2014] [Indexed: 10/24/2022]
Abstract
PURPOSE To evaluate the long-term outcomes of laser in situ keratomileusis (LASIK) for high myopia with or without astigmatism. SETTING Vissum Instituto Oftalmologico de Alicante and Miguel Hernandez University, Alicante, Spain. DESIGN Retrospective-prospective case series. METHODS 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. RESULTS 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. CONCLUSIONS 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. FINANCIAL DISCLOSURE No author has a financial or proprietary interest in any material or method mentioned.
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Affiliation(s)
- Jorge L Alió
- From Vissum Instituto Oftalmologico de Alicante (Alió, Soria, Abbouda) and the Division of Ophthalmology (Alió, Peña-García), Universidad Miguel Hernández, Alicante, Spain.
| | - Felipe Soria
- From Vissum Instituto Oftalmologico de Alicante (Alió, Soria, Abbouda) and the Division of Ophthalmology (Alió, Peña-García), Universidad Miguel Hernández, Alicante, Spain
| | - Alessandro Abbouda
- From Vissum Instituto Oftalmologico de Alicante (Alió, Soria, Abbouda) and the Division of Ophthalmology (Alió, Peña-García), Universidad Miguel Hernández, Alicante, Spain
| | - Pablo Peña-García
- From Vissum Instituto Oftalmologico de Alicante (Alió, Soria, Abbouda) and the Division of Ophthalmology (Alió, Peña-García), Universidad Miguel Hernández, Alicante, Spain
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Santhiago MR, Smadja D, Gomes BF, Mello GR, Monteiro ML, Wilson SE, Randleman JB. Association between the percent tissue altered and post-laser in situ keratomileusis ectasia in eyes with normal preoperative topography. Am J Ophthalmol 2014; 158:87-95.e1. [PMID: 24727263 DOI: 10.1016/j.ajo.2014.04.002] [Citation(s) in RCA: 125] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2014] [Revised: 03/29/2014] [Accepted: 04/01/2014] [Indexed: 11/26/2022]
Abstract
PURPOSE To investigate the association of a novel metric, percent tissue altered, with the occurrence of ectasia after laser in situ keratomileusis (LASIK) in eyes with normal corneal topography and to compare this metric with other recognized risk factors. DESIGN Retrospective case-control study. METHODS The study included 30 eyes from 16 patients with bilateral normal preoperative Placido-based corneal topography that developed ectasia after LASIK (ectasia group) and 174 eyes from 88 consecutive patients with uncomplicated LASIK and at least 3 years of postoperative follow-up. The following metrics were evaluated: age, preoperative central corneal thickness, residual stromal bed, Ectasia Risk Score System scores, and percent tissue altered, derived from [PTA = (FT + AD)/CCT], where FT = flap thickness, AD = ablation depth, and CCT = preoperative central corneal thickness. RESULTS In the ectasia group, percent tissue altered ≥40 was the most prevalent factor (97%), followed by age <30 years (63%), residual stromal bed ≤300 μm (57%), and ectasia risk score ≥ 3 (43%) (P < .001 for all). Percent tissue altered ≥ 40 had the highest odds ratio (223), followed by residual stromal bed ≤ 300 μm (74) and ectasia risk score ≥ 4 (8). Stepwise logistic regression revealed percent tissue altered ≥ 40 as the single most significant independent variable (P < .0001). CONCLUSIONS Percent tissue altered at the time of LASIK was significantly associated with the development of ectasia in eyes with normal preoperative topography and was a more robust indicator of risk than all other variables in this patient population.
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Igarashi A, Shimizu K, Kamiya K. Eight-year follow-up of posterior chamber phakic intraocular lens implantation for moderate to high myopia. Am J Ophthalmol 2014; 157:532-9.e1. [PMID: 24239774 DOI: 10.1016/j.ajo.2013.11.006] [Citation(s) in RCA: 158] [Impact Index Per Article: 15.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2013] [Revised: 11/04/2013] [Accepted: 11/06/2013] [Indexed: 11/17/2022]
Abstract
PURPOSE To assess the long-term clinical outcomes of Implantable Collamer Lens (Visian ICL; STAAR Surgical) implantation for moderate to high myopia. DESIGN Retrospective observational case series. METHODS This study evaluated 41 eyes of 41 patients with myopic refractive errors of -4.00 to -15.25 diopters (D) who underwent ICL implantation and routine postoperative examinations. Before surgery, and 1 and 6 months and 1, 4 and 8 years after surgery, we assessed the safety, efficacy, predictability, stability, and adverse events of the surgery. RESULTS The safety and efficacy indices were 1.13 ± 0.27 and 0.83 ± 0.36. At 8 years, 68.3% and 85.4% of the eyes were within 0.5 and 1.0 D, respectively, of the targeted correction. Manifest refraction changes of -0.32 ± 0.73 D occurred between 1 month and 8 years. The mean endothelial cell loss from preoperative levels was 6.2% at 8 years. Two eyes (4.9%) developed clinically significant symptomatic cataract during the follow-up period. Simultaneous lens extraction and phacoemulsification with IOL implantation was successfully performed in these 2 eyes. CONCLUSIONS According to our experience, ICL implantation was overall good in measures of safety, efficacy, predictability, and stability for the correction of moderate to high myopia during the 8-year observation period, suggesting its long-term viability as a surgical option for the treatment of such eyes.
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Affiliation(s)
- Akihito Igarashi
- Department of Ophthalmology, University of Kitasato School of Medicine, Kanagawa, Japan.
| | - Kimiya Shimizu
- Department of Ophthalmology, University of Kitasato School of Medicine, Kanagawa, Japan
| | - Kazutaka Kamiya
- Department of Ophthalmology, University of Kitasato School of Medicine, Kanagawa, Japan
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Abstract
PURPOSE In myopia, biometry including the axial length is important, along with the refractive data. We compared the rates of myopic regression 3 years after phakic intraocular lens (pIOL) implantation and laser in situ keratomileusis (LASIK) after matching the preoperative axial length in highly myopic eyes of Japanese patients. METHODS This retrospective nonrandomized study included 133 eyes of 84 patients with myopia exceeding -6.00 diopters (D) who underwent implantation of two iris-fixated pIOLs (pIOL group, 66 eyes/46 patients) or myopic LASIK (LASIK group, 67 eyes/38 patients) who were followed for more than 3 years postoperatively. The patient age, preoperative refraction, and preoperative axial length were matched between the study groups. RESULTS There were no significant differences preoperatively between the groups in age, intraocular pressure, refraction, keratometry, or axial length. The mean regression values after 3 years compared with the 1-month postoperative refractions were -0.12 ± 0.47 (SD) D in the pIOL group and -0.82 ± 0.69 D in the LASIK group (p < 0.001). The differences in the mean regression rates between 1 and 12 months, 12 and 24 months, and 24 and 36 months of follow-up were, respectively, 0.09 ± 0.38 D, -0.11 ± 0.35 D, and -0.11 ± 0.30 D in the pIOL group and -0.57 ± 0.84 D, -0.24 ± 0.47 D, and 0.00 ± 0.53 D in the LASIK group (p < 0.001, p = 0.07, p = 0.15, respectively). CONCLUSIONS There was a significant difference in myopic regression 3 years postoperatively between the groups matched for preoperative axial length in Japanese patients. This result has the potential to elucidate myopia in the future.
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Optical and visual simulation of standard and modified spherical aberration implantable Collamer lens post myopic LASIK surgery. Eur J Ophthalmol 2013; 24:330-7. [PMID: 24057938 DOI: 10.5301/ejo.5000372] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/05/2013] [Indexed: 11/20/2022]
Abstract
PURPOSE To evaluate the visual quality achieved in patients undergoing standard or modified implantable Collamer lens (ICL) to correct residual myopic error after laser-assisted in situ keratomileusis (LASIK) surgery. METHODS The adaptive optics visual simulator was used to simulate LASIK surgery of moderate and high myopia with a myopic regression corrected by a standard and modified ICL. Visual acuity (VA) and contrast sensitivity (CS) were measured in 14 subjects at 3- and 4.5-mm pupil. Point spread function and simulated retinal images were calculated. RESULTS Comparing LASIK plus standard ICL and LASIK plus modified ICL simulations, for moderate myopia, VA improvement was less than 1 line in all VA contrasts and both pupils evaluated. No statistically significant differences were found in CS between the simulations at any spatial frequency evaluated and for 3-mm pupil (p>0.05), but differences were significant at 4.5-mm pupil (p<0.05). For high myopia, the VA improvement was less than 1 line at 3-mm pupil, although it increased 2 or more lines at 4.5-mm pupil. Statistically significant differences were found in CS between the simulations for all spatial frequencies and both pupils evaluated (p<0.05), except for low and medium spatial frequencies at 3-mm pupil (p>0.05). CONCLUSIONS These outcomes suggest that an ICL is a good option to correct the myopic residual error after myopic LASIK. When the ICL's spherical aberration is modified, the post-LASIK eyes of high myopia are the most benefited, as these eyes are more aberrated than after moderate myopic LASIK.
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Muftuoglu O, Ayar O, Ozulken K, Ozyol E, Akıncı A. Posterior corneal elevation and back difference corneal elevation in diagnosing forme fruste keratoconus in the fellow eyes of unilateral keratoconus patients. J Cataract Refract Surg 2013; 39:1348-57. [PMID: 23820305 DOI: 10.1016/j.jcrs.2013.03.023] [Citation(s) in RCA: 86] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2012] [Revised: 03/02/2013] [Accepted: 03/09/2013] [Indexed: 10/26/2022]
Abstract
PURPOSE To evaluate posterior corneal elevation and back difference corneal elevation in patients with keratoconus in 1 eye and forme fruste keratoconus in the fellow eye. SETTING Kudret Eye Hospital, Ankara, Turkey. DESIGN Case-control study. METHODS This study retrospectively reviewed patients with keratoconus in 1 eye and forme fruste keratoconus in the fellow eye and eyes of normal subjects. All subjects were evaluated with a rotating Scheimpflug imaging system (Pentacam), including sagittal and tangential anterior curve analysis, keratometry, and posterior elevation. The back difference elevation values were extrapolated from the difference maps of the Belin-Ambrosió enhanced ectasia display of the Scheimpflug system. The receiver operating characteristic (ROC) curves were analyzed to evaluate the sensitivity and specificity of the parameters. RESULTS The corneal power, pachymetric progression index, and posterior corneal elevation (posterior elevation and back difference elevation) measurements were statistically significantly higher in eyes with keratoconus or forme fruste keratoconus than in eyes of normal control subjects (P<.05). Using ROC analysis, the area under the curve values of mean keratometry, steepest point on the tangential curve, minimum corneal thickness, pachymetric progression index, Ambrósio's relational thickness, posterior elevation, and back difference elevation to distinguish forme fruste keratoconus from control subjects were 0.51, 0.84, 0.65, 0.81, 0.72, 0.68, and 0.76, respectively. CONCLUSIONS Back difference elevation was better than posterior elevation in diagnosing forme fruste keratoconus. However, as sole parameters, both had limited sensitivity and specificity to differentiate between forme fruste keratoconus eyes and normal control eyes.
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Affiliation(s)
- Orkun Muftuoglu
- Department of Ophthalmology (Muftuoglu), Medipol University, Istanbul, Turkey.
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Sutton G, Lawless M, Hodge C. Laser in situ keratomileusis in 2012: a review. Clin Exp Optom 2013; 97:18-29. [PMID: 23786377 DOI: 10.1111/cxo.12075] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2012] [Revised: 11/08/2012] [Accepted: 12/14/2012] [Indexed: 11/25/2022] Open
Abstract
Laser in situ keratomileusis (LASIK) is a safe and effective treatment for refractive error. A combination of technological advances and increasing surgeon experience has served to further refine refractive outcomes and reduce complication rates. In this article, we review LASIK as it stands in late 2012: the procedure, indications, technology, complications and refractive outcomes.
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Affiliation(s)
- Gerard Sutton
- Vision Eye Institute, Chatswood, New South Wales, Australia; Save Sight Institute, Sydney Medical School, University of Sydney, Sydney, New South Wales, Australia.
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Abstract
Implantation of phakic intraocular lenses (pIOLs) is a reversible refractive procedure, preserving the patient's accommodative function with minimal induction of higher order aberrations compared with corneal photoablative procedures. Despite this, as an intraocular procedure, it has potential risks such as cataracts, chronic uveitis, pupil ovalization, corneal endothelial cell loss, pigmentary dispersion syndrome, pupillary block glaucoma, astigmatism, or endophthalmitis. Currently, only two models of posterior chamber pIOLs are commercially available, the implantable collammer lens (STAAR Surgical Co.) and the phakic refractive lens (PRL; Zeiss Meditec). The number of published reports on the latter is very low, and some concerns still remain about its long-term safety. The present article reviews the published literature on the outcomes after PRL implantation in order to provide a general overview and evaluate its real potential as a surgical refractive option.
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Shojaei A, Eslani M, Vali Y, Mansouri M, Dadman N, Yaseri M. Effect of timolol on refractive outcomes in eyes with myopic regression after laser in situ keratomileusis: a prospective randomized clinical trial. Am J Ophthalmol 2012; 154:790-798.e1. [PMID: 22935601 DOI: 10.1016/j.ajo.2012.05.013] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2012] [Revised: 05/15/2012] [Accepted: 05/15/2012] [Indexed: 11/26/2022]
Abstract
PURPOSE To compare the effects of timolol on refractive outcomes in eyes with myopic regression after laser in situ keratomileusis (LASIK) with a control-matched group. DESIGN Prospective, randomized, parallel-controlled, double-masked clinical trial. A computer-generated randomization list based on random block permutation (length 4 to 8) was used for treatment allocation. METHODS setting: Basir Eye Center, Tehran, Iran. PATIENT POPULATION Of 124 eyes with myopic regression after LASIK using Technolas 217-Z, 45 eyes in each group were analyzed. INTERVENTION Patients were randomly assigned into either Group 1, who received timolol 0.5% eye drops, or Group 2, who received artificial tears for 6 months. MAIN OUTCOME MEASURE Spherical equivalent (SE) at 6 months posttreatment. RESULTS In Group 1, SE improved from -1.48 ± 0.99 diopter (D) before treatment to -0.88 ± 0.91 D and -0.86 ± 0.93 D 6 months after treatment and 6 months after timolol discontinuation, respectively (P < .001). In Group 2, it was -1.57 ± 0.67 D, -1.83 ± 0.76 D, and -1.91 ± 0.70 D, respectively (P < .001). SE was significantly better in Group 1 6 months after treatment and 6 months after discontinuation of treatment (P < .001 for both comparisons). There was a 0.26 D decrease in SE improvement every 4 months after the surgery in the Group 1 (P < .001). CONCLUSIONS Timolol application is effective for the treatment of myopic regression after LASIK compared with control group. Its effects last for at least 6 months after its discontinuation.
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Igarashi A, Kamiya K, Shimizu K, Komatsu M. Time course of refractive and corneal astigmatism after laser in situ keratomileusis for moderate to high astigmatism. J Cataract Refract Surg 2012; 38:1408-13. [PMID: 22814047 DOI: 10.1016/j.jcrs.2012.03.030] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2011] [Revised: 02/11/2012] [Accepted: 03/03/2012] [Indexed: 11/30/2022]
Abstract
PURPOSE To assess the time course of refractive and corneal astigmatism after laser in situ keratomileusis (LASIK) in eyes with moderate to high astigmatism. SETTING Department of Ophthalmology, Kitasato University, Kanagawa, Japan. DESIGN Retrospective case series. METHODS Keratometric readings and corneal astigmatism were determined with an autokeratometer in consecutive patients who had LASIK for moderate to high astigmatism (≥2.00 diopters [D]). RESULTS The study enrolled 48 eyes of 35 patients with a mean age of 34.0 years ± 8.1 (SD), a mean spherical error of -5.10 ± 2.11 D, and a mean cylindrical error of -2.74 ± 0.99 D. Postoperatively, the mean spherical refraction changed significantly from 0.38 ± 0.80 D at 1 week to -0.13 ± 0.90 D at 1 year (P<.001, Wilcoxon signed-rank test). The mean cylindrical refraction showed no significant change (-0.67 ± 0.54 D at 1 week to -0.63 ± 0.63 D at 1 year) (P=.54). There were significant increases in the flattest and steepest keratometry readings at 1 week and at 1 year. However, no significant change in corneal astigmatism was found at either time point (P=.10). CONCLUSIONS After LASIK, there was significant refractive regression in the spherical component but not in the cylindrical component. This suggests that refractive regression occurs by corneal steepening in the spherical component and that astigmatic regression does not occur, even in moderately to highly astigmatic eyes. FINANCIAL DISCLOSURE No author has a financial or proprietary interest in any material or method mentioned.
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Affiliation(s)
- Akihito Igarashi
- Department of Ophthalmology, University of Kitasato School of Medicine, Kanagawa, Japan.
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Laser in situ keratomileusis application for myopia over minus 14 diopter with long-term follow-up. Int Ophthalmol 2012; 32:435-41. [DOI: 10.1007/s10792-012-9595-4] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2012] [Accepted: 05/21/2012] [Indexed: 10/28/2022]
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Knox Cartwright NE, Tyrer JR, Jaycock PD, Marshall J. Effects of Variation in Depth and Side Cut Angulations in LASIK and Thin-flap LASIK Using a Femtosecond Laser: A Biomechanical Study. J Refract Surg 2012; 28:419-25. [DOI: 10.3928/1081597x-20120518-07] [Citation(s) in RCA: 76] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2011] [Accepted: 04/24/2012] [Indexed: 11/20/2022]
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Zhang ZW, Niu WR, Ma MM, Jiang KLM, Ke BL. Time course of Q value after myopic laser-assisted in situ keratomileusis. ACTA ACUST UNITED AC 2012; 26:141-5. [PMID: 22207921 DOI: 10.1016/s1001-9294(11)60038-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
OBJECTIVE To assess the time course of Q value after myopic laser-assisted in situ keratomileusis (LASIK) and preliminarily evaluate the determinants of the difference of Q value between before and after LASIK. METHODS We performed a retrospective, longitudinal investigation on patients undergoing wavefront optimized LASIK therapy for emmetropization. A total of 418 eyes from 222 cases were examined preoperatively, and partly followed up at one week (172 eyes), one month (134 eyes) and three months (51 eyes) after surgery. The horizontal, vertical and total Q values of cornea were calculated from eccentricity measured at the central 6-mm corneal zones respectively. Potential determinants of the change of Q value were analyzed using multiple linear regressions. RESULTS The mean Q value was -0.17 +/- 0.13 preoperatively, and 0.99 +/- 0.70, 0.97 +/- 0.66, and 0.86 +/- 0.41 one week, one and three months postoperatively, respectively. One way analysis of variance (ANOVA) demonstrated significant differences between measurements made before surgery and at all postoperative times (at one week, one and three months; all P<0.0001, Bonferroni post hoc), but no significant differences were found among postoperative groups. Significant differences of Q values between horizontal and vertical meridians were found before surgery and at all postoperative times (all P<0.0001). Multiple regression analysis revealed that change of Q value significantly correlated with manifest refraction spherical equivalent (r=0.116, P<0.0001) and axial length (r=0.264, P<0.0001). CONCLUSIONS Over the study period, the primary changes in Q value occur within 1 week after surgery, and then become slightly decreased and nearly stable. Manifest refraction spherical equivalent and axial length play a significant role in the change of postoperative Q value.
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Affiliation(s)
- Zheng-Wei Zhang
- Department of Ophthalmology, First People's Hospital of Shanghai Affiliated to Shanghai Jiaotong University, Shanghai 200080, China
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Astigmatism correction: Laser in situ keratomileusis versus posterior chamber collagen copolymer toric phakic intraocular lens implantation. J Cataract Refract Surg 2012; 38:574-81. [PMID: 22321354 DOI: 10.1016/j.jcrs.2011.10.034] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2011] [Revised: 10/10/2011] [Accepted: 10/14/2011] [Indexed: 11/24/2022]
Abstract
PURPOSE To compare the stability and predictability of astigmatism correction between toric phakic intraocular lens (pIOL) implantation and laser in situ keratomileusis (LASIK). SETTING Nagoya Eye Clinic, Nagoya, Japan. DESIGN Comparative case series. METHODS Consecutive patients who had Implantable Collamer Lens pIOL implantation or LASIK were divided into 3 subgroups according to the amount of refractive cylinder correction (low, 0.00 to 1.25 diopters [D]; moderate, 1.50 to 2.75 D; high, ≥ 3.00 D). Manifest refraction was measured preoperatively and 1, 3, 6, and 12 months postoperatively. Based on these data, the predictability and stability of the refractive cylinder correction, error of the refractive cylinder correction, and error of the refractive cylinder correction axis were evaluated. RESULTS The study comprised 338 eyes (196 patients) in the toric pIOL group and 351 eyes (202 patients) in the LASIK group. In the moderate cylinder subgroup, more eyes were corrected within ± 0.50 D of the postoperative refractive cylinder in the LASIK group (132 eyes [91%]) than in the toric pIOL group (111 eyes [79%]). In the high refractive cylinder subgroup, the error of the refractive cylinder correction in the LASIK group was significantly higher than in the toric pIOL group (P=.032). The postoperative manifest refractive cylinder did not change in either group during the follow-up period. CONCLUSIONS The stability of the refractive cylinder after toric pIOL implantation was as high as after LASIK. Although predictability in the LASIK group was higher than in the toric pIOL group in eyes with moderate refractive cylinder, the toric pIOL group had higher predictability than the LASIK group in eyes with high refractive cylinder.
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Gazieva L, Beer MH, Nielsen K, Hjortdal J. A retrospective comparison of efficacy and safety of 680 consecutive lasik treatments for high myopia performed with two generations of flying-spot excimer lasers. Acta Ophthalmol 2011; 89:729-33. [PMID: 20102346 DOI: 10.1111/j.1755-3768.2009.01830.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
PURPOSE 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. METHODS 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. RESULTS 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. CONCLUSIONS 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).
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Affiliation(s)
- Lola Gazieva
- Department of Ophthalmology, Aarhus University Hospital, Aarhus, Denmark.
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Alió JL, Wolter NV, Piñero DP, Amparo F, Sari ES, Cankaya C, Laria C. Pediatric Refractive Surgery and Its Role in the Treatment of Amblyopia: Meta-Analysis of the Peer-Reviewed Literature. J Refract Surg 2011; 27:364-74. [DOI: 10.3928/1081597x-20100831-01] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2010] [Accepted: 07/15/2010] [Indexed: 11/20/2022]
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Zalentein WN, Tervo TMT, Holopainen JM. Long-term follow-up of photorefractive keratectomy for myopia: Comparative study of excimer lasers. J Cataract Refract Surg 2010; 37:138-43. [PMID: 21067894 DOI: 10.1016/j.jcrs.2010.07.025] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2009] [Revised: 07/21/2010] [Accepted: 07/21/2010] [Indexed: 11/30/2022]
Abstract
PURPOSE To compare the long-term results of photorefractive keratectomy (PRK) for low to moderate myopia performed using a broad-beam laser system or a scanning-slit laser system. SETTING Department of Ophthalmology, University of Helsinki, Helsinki, Finland. DESIGN Case-control study. METHODS This follow-up study comprised eyes with myopia (-1.25 to -7.00 diopters [D]) or myopic astigmatism (astigmatism lower than -2.50 D) corrected by PRK using a broad-beam (Visx) or scanning-slit (Nidek) laser. Follow-up included a visit at 3 months and at more than 8 years. The uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), and manifest refraction were recorded. RESULTS The broad-beam group comprised 27 eyes and the scanning-slit group, 34 eyes. At the last postoperative follow-up, the UDVA was 0.0 or better in 55% of eyes in the broad-beam group and 65% of eyes in the scanning-slit group. The CDVA was 0.0 or better in all eyes in the broad-beam group and 96% of eyes in the scanning-slit group. Regarding predictability, 48% and 73% of the eyes, respectively, were within ±0.50 D of the intended spherical equivalent refraction. There were no statistically significant differences between the 2 laser groups in any preoperative or postoperative parameter. CONCLUSION There were no significant differences in UDVA, CDVA, or SE after PRK for low to moderate myopia between the broad-beam laser system and the scanning-slit laser system. FINANCIAL DISCLOSURE No author has a financial or proprietary interest in any material or method mentioned.
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Rosman M, Alió JL, Ortiz D, Pérez-Santonja JJ. Refractive stability of LASIK with the Visx 20/20 excimer laser vs ZB5m phakic iol implantation in patients with high myopia (>-10.00 d): a 10-year retrospective study. J Refract Surg 2010; 27:279-86. [PMID: 20672763 DOI: 10.3928/1081597x-20100707-02] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2008] [Accepted: 06/17/2010] [Indexed: 11/20/2022]
Abstract
PURPOSE To compare the long-term outcomes of LASIK and ZB5M phakic intraocular lens implantation (PIOL) (Domilens) for high myopia (>-10.00 diopters [D]). METHODS This long-term (10 years) follow-up retrospective interventional case series study included 126 eyes that underwent LASIK and 52 eyes that underwent ZB5M angle-supported PIOL implantation. Both groups of eyes were similar in terms of preoperative spherical equivalent refraction (SE), corrected distance visual acuity (CDVA), and age. RESULTS Mean preoperative SE was -14.33 D in the LASIK group and -14.84 D in the PIOL group. At 10-year follow-up, mean postoperative SE was -1.47±2.00 D in the LASIK group and -1.01±1.36 D in the PIOL group (P=.21). In the LASIK group, 67% of eyes were within ±1.00 D of emmetropia at 2 years after surgery, compared to 42% at 10 years. In the PIOL group, 68% of eyes were within ±1.00 D of emmetropia 2 years after implantation compared to 53% at 10 years. In the LASIK group, 43.5% of eyes achieved UDVA of 20/40 or better 10 years after surgery compared to 67.9% in the PIOL group (P=.02). CONCLUSIONS The ZB5M angle-supported PIOL was shown to have better predictability and stability compared to LASIK over 10 years. However, reductions in endothelial cell count over time were observed in eyes with PIOLs.
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Affiliation(s)
- Mohamad Rosman
- Vissum/Instituto Oftalmológico de Alicante. Alicante, Spain
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Koshimizu J, Dhanuka R, Yamaguchi T. Ten-year follow-up of photorefractive keratectomy for myopia. Graefes Arch Clin Exp Ophthalmol 2010; 248:1817-25. [PMID: 20300767 DOI: 10.1007/s00417-010-1312-2] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2009] [Revised: 12/29/2009] [Accepted: 01/18/2010] [Indexed: 11/27/2022] Open
Abstract
BACKGROUND The aim of this study is to evaluate the long-term (10-year) outcome of excimer laser photorefractive keratectomy (PRK) on myopic eyes. METHODS This retrospective study included 42 eyes of 29 patients (13 male, 16 female; mean age 33.4 years, range 21 to 60) who were treated with myopic PRK at St. Luke's International Hospital, Tokyo, Japan, from May 1 1995 to December 31 1998, and followed up for more than 10 years. The main outcome measures were efficacy, predictability, stability, safety, and complications. We also evaluated the progress of intraocular pressure, corneal thickness, and endothelial cell density after the surgery. The cases of retreatments were excluded from this study. RESULTS Ten years after the surgery, 17 eyes (40%) had 20/20 vision or better, and 35 eyes (81%) had 20/40 or better. With regard to the refractive predictability, 55 percent of the eyes were within ± 1.0D and 76% were within ± 2.0D, 10 years after the surgery. There was myopic regression with a mean change in refraction of-0.51 ± 1.78D. Best spectacle-corrected visual acuity (BCVA) was unchanged or improved in 95%, and only two eyes lost 1 line of BCVA. The mean corneal haze score was 0.19 ± 0.40, and the decreasing rate of endothelial cell was 8.30 ± 9.94% at 10 years, which was slightly higher than the spontaneous decreasing rate with age. CONCLUSIONS PRK is safe and effective in refraction even 10 years after surgery; however, further long-term follow-up is needed to evaluate the decreasing of endothelial cells.
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Affiliation(s)
- Junko Koshimizu
- Department of Ophthalmology, Juntendo University Urayasu Hospital, 2-1-1 Tomioka, Urayasu-shi, Chiba-ken, 279-0021, Japan.
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Rosman M, Alió JL, Ortiz D, Perez-Santonja JJ. Comparison of LASIK and Photorefractive Keratectomy for Myopia From −10.00 to −18.00 Diopters 10 Years After Surgery. J Refract Surg 2010; 26:168-76. [DOI: 10.3928/1081597x-20100224-02] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2008] [Accepted: 02/18/2009] [Indexed: 11/20/2022]
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Comparison of the changes in corneal biomechanical properties after photorefractive keratectomy and laser in situ keratomileusis. Cornea 2009; 28:765-9. [PMID: 19574911 DOI: 10.1097/ico.0b013e3181967082] [Citation(s) in RCA: 83] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
PURPOSE To compare the postoperative biomechanical properties of the cornea after photorefractive keratectomy (PRK) and after laser in situ keratomileusis (LASIK) in eyes with myopia. METHODS We retrospectively examined 27 eyes of 16 patients undergoing PRK and 31 eyes of 16 patients undergoing LASIK for the correction of myopia. Corneal hysteresis (CH) and corneal resistance factor (CRF) were measured with Ocular Response Analyzer before and 3 months after surgery. We also investigated the relationship between these biomechanical changes and the amount of myopic correction. RESULTS The CH was decreased significantly from 10.8 +/- 1.3 (mean +/- SD) mmHg to 9.2 +/- 1.6 mmHg after PRK (P < 0.001), and from 10.8 +/- 1.4 mmHg to 8.6 +/- 0.9 mmHg after LASIK (P < 0.001). The CRF was also decreased significantly, from 10.3 +/- 1.5 mmHg to 8.4 +/- 1.8 mmHg after PRK (P < 0.001), and from 10.3 +/- 1.5 mmHg to 7.7 +/- 1.3 mmHg after LASIK (P < 0.001). The amount of decrease in CH and CRF was significantly larger after LASIK than after PRK (P = 0.04). There was a significant correlation between the amount of myopic correction and changes in biomechanical properties after PRK (r = -0.61, P < 0.01 for CH, r = -0.41, P < 0.05 for CRF) and LASIK (r = -0.37, P < 0.05 for CH, r = -0.45, P < 0.05 for CRF). CONCLUSIONS Both PRK and LASIK can affect the biomechanical strength of the cornea depending on the amount of myopic correction. The amount of biomechanical changes is larger after LASIK than after PRK. From a biomechanical viewpoint, PRK may be a less invasive surgical approach for the correction of myopia than LASIK.
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