Predictability of Central Corneal Stromal Reduction After SMILE and FS-LASIK for High Myopia Correction: A Prospective Randomized Contralateral Eye Study.

PURPOSE: To compare small incision lenticule extraction (SMILE) and femtosecond laser-assisted in situ keratomileusis (FS-LASIK) in terms of the predictability of central stromal thickness reduction in eyes with high myopia.

METHODS

In this prospective, randomized contralateral eye trial, 42 patients received SMILE in one eye and FS-LASIK (using the Amaris 750S excimer laser [SCHWIND eye-tech-solutions]) in the fellow eye for the correction of high myopia (manifest refraction spherical equivalent: < -6.00 diopters). Spectral-domain optical coherence tomography was used to measure the central corneal and epithelial thickness. Pre-operative and postoperative values were compared to determine the amount of central stromal reduction achieved.

RESULTS

At the 6-month follow-up visit, the amount of central stromal reduction was overestimated by 20.05 ± 5.92 µm in the SMILE group (P < .0001) and underestimated by 8.21 ± 8.14 µm in the FS-LASIK group (P < .0001). The mean actual central stromal reduction achieved with SMILE was significantly less than that achieved with FS-LASIK (10.10 ± 18.01 µm, range: 1.90 to 18.29 µm, P < .001). The discrepancy between the planned and achieved central corneal stromal reduction was not associated with refractive overcorrection or undercorrection in either the SMILE group or the FS-LASIK group (P = .9743 vs P = .0777).

CONCLUSIONS

In patients with high myopia, the laser software platform may underestimate and overestimate the amount of actual corneal reduction in eyes treated with FS-LASIK and SMILE, respectively. SMILE required less corneal stroma compared to FS-LASIK in the studied cohort using the Amaris 750S excimer laser when correcting a similar spherical equivalent refraction. [J Refract Surg. 2022;38(2):90-97.].