Efficacy, predictability, and safety of small incision lenticule extraction: 6-months prospective cohort study

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Abstract

Background

To report our experience with small incision lenticule extraction ("SMILE") for myopia treatment.

Methods

In this prospective clinical study, we evaluated 447 eyes from 224 patients with myopia, with and without astigmatism. We followed the patients for 6 months after SMILE.

Results

The mean (±standard deviation, SD) spherical equivalent was -6.75 ± 1.65 diopters (D) preoperatively and -0.21 ± 0.37 D at 6 months postoperatively. Our data showed that 97.9% of eyes were within ±1.0 D and 86.1% were within ±0.5 D of the intended correction. Furthermore, 79.8% had an uncorrected distance visual acuity (UDVA) of 0 logMAR or less (20/20 or better in the Snellen equivalent) 6 months after surgery. Additionally, 48.5% remained unchanged, 41% gained one line of corrected distance visual acuity (CDVA), 7.2% gained two lines of CDVA, 3.3% lost one line of CDVA, and 0.3% lost two or more lines of CDVA. Age was the only predictor for worsening UDVA at 6 months postoperatively in linear regression analyses (0.07 decrease logMAR per increased 10 years of age; P < 0.05). No predictor showed an association with error in spherical equivalent refraction at 6 months postoperatively.

Conclusions

SMILE is an effective and safe refractive surgery. Age was the only predictor that influenced visual outcome, but its effect appeared clinically insignificant. Faster visual recovery is also expected with improved surgical technique.

Related collections

Most cited references 15

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Results of small incision lenticule extraction: All-in-one femtosecond laser refractive surgery.

Samir Shah, Pankaj Shah, S Sengupta (2010)

To report the clinical results of small incision lenticule extraction to correct refractive errors using a femtosecond laser to refine the femtosecond lenticule extraction technique. Private laser center, Vadodara, India. Prospective clinical study. The VisuMax femtosecond laser system was used to perform small incision lenticule extraction to treat refractive errors. The laser was used to cut a refractive lenticule intrastromally to correct myopia and myopic astigmatism. The lenticule was then extracted from the stroma through a 3.0 to 5.0 mm incision. Outcome measures were corrected distance visual acuity (CDVA), uncorrected distance visual acuity (UDVA), and manifest refraction during 6 months of follow-up. Corneal topography and ocular wavefront aberrations were also measured. The study enrolled 51 eyes of 41 patients. The mean spherical equivalent was -4.87 diopters (D) ± 2.16 (SD) preoperatively and +0.03 ± 0.30 D 6 months postoperatively. Refractive stability was achieved within 1 month (P<.01). Six months after surgery, 79% of all full-correction cases had a UDVA of 20/25 or better. The 6-month postoperative CDVA was the same as or better than the preoperative CDVA in 95% of eyes. Two eyes lost 1 line of CDVA. All-in-one femtosecond refractive correction using a small incision technique was safe, predictable, and effective in treating myopia and myopic astigmatism. No author has a financial or proprietary interest in any material or method mentioned. Additional disclosure is found in the footnotes. Copyright © 2011 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.

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Mathematical model to compare the relative tensile strength of the cornea after PRK, LASIK, and small incision lenticule extraction.

J Bradley Randleman, T. Archer, D Reinstein (2013)

To develop a mathematical model to estimate the relative differences in postoperative stromal tensile strength following photorefractive keratectomy (PRK), LASIK, and small incision lenticule extraction (SMILE). Using previously published data where in vitro corneal stromal tensile strength was determined as a function of depth, a mathematical model was built to calculate the relative remaining tensile strength by fitting the data with a fourth order polynomial function yielding a high correlation coefficient (R(2) = 0.930). Calculating the area under this function provided a measure of total stromal tensile strength (TTS), based only on the residual stromal layer for PRK or LASIK and the residual stromal layers above and below the lenticule interface for SMILE. Postoperative TTS was greatest after SMILE, followed by PRK, then LASIK; for example, in a 550-μm cornea after 100-μm tissue removal, postoperative TTS was 75% for SMILE (130-μm cap), 68% for PRK, and 54% for LASIK (110-μm flap). The postoperative TTS decreased for thinner corneal pachymetry for all treatment types. In LASIK, the postoperative TTS decreased with increasing flap thickness by 0.22%/μm, but increased by 0.08%/μm for greater cap thickness in SMILE. The model predicted that SMILE lenticule thickness could be approximately 100 μm greater than the LASIK ablation depth and still have equivalent corneal strength (equivalent to approximately 7.75 diopters). This mathematical model predicts that the postoperative TTS is considerably higher after SMILE than both PRK and LASIK, as expected given that the strongest anterior lamellae remain intact. Consequently, SMILE should be able to correct higher levels of myopia. Copyright 2013, SLACK Incorporated.

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Small-incision lenticule extraction for moderate to high myopia: Predictability, safety, and patient satisfaction.

Anders Vestergaard, Anders R. Ivarsen, Sven Asp … (2012)

To present initial clinical experience with small-incision lenticule extraction for the treatment of moderate to high myopia. Department of Ophthalmology, Aarhus University Hospital, Aarhus, Denmark. Prospective clinical study. For small-incision lenticule extraction, an intrastromal lenticule was cut with a femtosecond laser and manually extracted without creation of a flap. Patients were treated and followed for 3 months. Only 1 randomly chosen eye of each patient was used in the statistical analyses. The study enrolled 144 patients. The mean preoperative spherical equivalent was -7.18 diopters (D) ± 1.57 (SD). Of eyes with emmetropia as target refraction, 40% had an uncorrected distance visual acuity of 0.1 logMAR or less 1 day after surgery; this increased to 73% at 3 months. The mean corrected distance visual acuity (CDVA) improved significantly from -0.01 (logMAR) preoperatively to -0.03 3 months postoperatively. None of the 127 eyes lost 2 lines or more of CDVA and 6 eyes lost 1 line of CDVA after 3 months. In contrast, 1 eye gained 2 lines and 24 eyes gained 1 line of CDVA. The achieved refraction was a mean of -0.09 ± 0.45 D from the attempted refraction. Of the eyes, 77% were within ±0.50 D and 95% were within ±1.00 D. Ninety-five percent of the patients would recommend the procedure to others. The refractive predictability, safety, and patient satisfaction 3 months after small-incision lenticule extraction were high and comparable to results in previous studies of femtosecond laser-assisted techniques. Drs. Hjortdal and Asp received travel reimbursement from Carl Zeiss Meditec AG, Jena, Germany. No other author has a financial or proprietary interest in any material or method mentioned. Copyright © 2012 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.

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Author and article information

Contributors

Jae Ryun Kim: oindiano99@gmail.com

Hyung Bin Hwang: leoanzel@catholic.ac.kr

Su Joung Mun: moons-6@daum.net

Young Taek Chung: eyegreen@eyegreen.com

Hyun Seung Kim: Sara514@catholic.ac.kr

Journal

Journal ID (nlm-ta): BMC Ophthalmol

Journal ID (iso-abbrev): BMC Ophthalmol

Title: BMC Ophthalmology

Publisher: BioMed Central (London )

ISSN (Electronic): 1471-2415

Publication date (Electronic): 3 October 2014

Publication date PMC-release: 3 October 2014

Publication date Collection: 2014

Volume: 14

Issue: 1

Electronic Location Identifier: 117

Affiliations

[ ]St. Mary’s Hospital, Department of Ophthalmology and Visual Science, College of Medicine, The Catholic University of Korea, #62 Yeouido-dong, Yeongdeungpo-gu, Seoul, 150-713 Korea

[ ]Onnuri Eye Clinic, Jeonju, Korea

Article

Publisher ID: 479

DOI: 10.1186/1471-2415-14-117

PMC ID: 4192335

PubMed ID: 25280533

SO-VID: d4d6364b-1482-475d-8325-af881e36f279

License:

This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License ( http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly credited. The Creative Commons Public Domain Dedication waiver ( http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.