Corneal Epithelial Remodeling After Hyperopic SMILE: A 4-Year Study.

Abstract

Purpose: The purpose of this study was to investigate dynamic changes in corneal epithelial thickness (ET) after hyperopic small incision lenticule extraction (SMILE).

Methods: This observational study included 18 eyes of 16 patients who were scheduled for hyperopic SMILE. High-resolution spectral-domain optical coherence tomography and a custom image segmentation algorithm were applied to measure corneal dynamic ET over a central 6 mm area. ET was analyzed among different corneal sectors (central, pericentral, and peripheral) at baseline and multiple postoperative time points (1 day, 1 month, 6 months, 2 years, and 4 years). Correlation analysis was performed between ET changes and preoperative and intraoperative parameters.

Results: The mean spherical equivalent of hyperopia correction was +2.64 ± 1.00 D, and the average age of enrolled 16 patients was 32.4 ± 10.8 years. At the last follow-up, 72% of eyes kept or improved corrected distance visual acuity, with 2 eyes that lost 2 lines. 72% of eyes were within ±1.0 D of target refraction, and 56% were within ±0.5 D. Average ET decreased by 11.0% (5.9 ± 2.3 μm) from 53.2 ± 3.5 μm to 47.4 ± 4.2 μm 4 years postoperatively (P<0.001). The ET at center 2 mm decreased most significantly by 14.5% (7.9 ± 2.9 μm), followed by the pericentral area by 10.5% (5.6 ± 2.3 μm). ET and front corneal curvature stabilized 1 month after surgery. No correlation was found between refraction regression and ET changes.

Conclusions: Hyperopic SMILE induced significant central ET thinning. ET remodeling in the 6 mm area stabilized after 1 month and did not underlie refractive changes.