Comparison of Corneal Epithelial Remodeling After Femtosecond Laser-Assisted LASIK and Small Incision Lenticule Extraction (SMILE)

PURPOSE: To comparatively investigate changes in epithelial thickness between myopic femtosecond laserassisted LASIK (FS-LASIK) and small incision lenticule extraction (SMILE). METHODS: This study compared the topographic epithelial thickness changes in 175 myopic eyes undergoing FS-LASIK (62 eyes) or SMILE (113 eyes). Epithelial thickness was obtained using spectral-domain optical coherence tomography before surgery and 1 and 3 months after surgery. Topographic epithelial thickness obtained by automatic algorithm and thickness variability (standard deviation over 17 imaged areas) was compared between two groups. Postoperative epithelial thickness changes were correlated with treatment parameters. RESULTS: For FS-LASIK, the mean epithelial thickness of the center zone (2 mm in diameter), paracenter (2 to 5 mm), and mid-periphery (5 to 6 mm) increased by 3.4, 4.3, and 2.1 mu m, respectively, at 1 month and by 4.4, 5.1, and 2.9 mu m, respectively, at 3 months. There was an increase of 2.5, 3.9, and 4.5 mu m, respectively, at 1 month and 3.0, 4.2, and 4.9 mu m, respectively, at 3 months following SMILE. The epithelial thickness did not change between 1 and 3 months postoperatively following SMILE, whereas it increased further after FS-LASIK. A larger increase of epithelial thickness was observed in the central zone at 3 months following FS-LASIK than SMILE, whereas the opposite was observed in the mid-periphery. The topographic thickness variability was greater after FS-LASIK than SMILE. Corneal epithelial thickening was proportional to the amount of myopia correction after both procedures. CONCLUSIONS: Topographic epithelial remodeling patterns differ following FS-LASIK or SMILE. Epithelial remodeling appears to stabilize more rapidly following SMILE than FS-LASIK.