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Briana C. Gapsis, Adam Ahlquist, Henry Perry, George Asimellis, A. John Kanellopoulos; Small incision lenticule extraction (SMILE) vs LASIK: an ex vivo biomechanical evaluation of low and high myopic corrections. Invest. Ophthalmol. Vis. Sci. 2016;57(12):2395.
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© ARVO (1962-2015); The Authors (2016-present)
The small-incision lenticule extraction (SMILE) procedure and laser in situ keratomileusis (LASIK) are both safe, effective, and predictable surgical techniques for the correction of myopia. SMILE presents an alternative to LASIK, which currently may be considered the most established form of laser vision correction. The purpose of this study is to evaluate corneal biomechanical changes associated with low and high myopic correction performed with small incision lenticule extraction (SMILE, employing the Visumax laser, Carl Zeiss Meditec, Jena Germany) compared to Femtosecond-laser assisted LASIK (FS200 & EX500 lasers, Alcon Surgical, Ft. Worth, TX)
Thirty human donor corneas were subjected to myopic SMILE or LASIK. These corneas were randomly allocated to one of four investigative groups (n=5 each), subjected to the following treatments: group-A -3.00 diopters (D) SMILE; group-B -8.00D SMILE; group-C -3.00D LASIK; group-D -8.00D LASIK. Additionally, two control groups (n=5 each) were formed, one for each procedure: group-E SMILE and group-F LASIK. The corneas in these control groups were subjected to the corresponding femtosecond-laser lamellar cuts but not to tissue removal. Biomechanical evaluation of tensile strength was conducted by biaxial force application. Primary outcome measures were stress at 10% and 15% strain, and Young’s modulus at 10% and 15% strain.
In SMILE, the average relative difference (Δ) of the four metrics evaluated was -35.6% between the -3.00D correction and control and -50.2% between the -8.00D correction and control. In LASIK, average Δ was -21.2% between the -3.00D correction and control, and -50.4% between the -8.00D correction and control. When evaluating the same degree of myopic correction, SMILE, compared to LASIK, appears to result in greater biomechanical reduction for the -3.00D correction (-25.9%) while the difference at -8.00D correction is not statistically significant.
Biomechanical tensile strength is reduced with increasing amounts of myopia corrected in both procedures. LASIK results in less strength reduction in smaller myopes while, in higher myopes, SMILE and LASIK appear to result in similar corneal tensile strength reduction.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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