AIM: To compare the changes in corneal epithelial thickness(CET)after small incision lenticule extraction(SMILE)and femtosecond laser-assisted in situ keratomileusis(FS-LASIK).METHODS: A total of 187 patients(187 eyes)who underwent either SMILE or FS-LASIK at Urumqi Aier Eye Hospital between December 2022 and November 2023 were collected. The patients were divided into SMILE group and FS-LASIK group according to surgical methods. The CET of the patients was measured by optical coherence tomography(OCT)system before surgery and at 1 wk, 1, 3, and 6 mo postoperatively.RESULTS: Changes in corneal epithelial thickness(△CET)in the central, paracentral, and mid-peripheral regions were compared at 6 mo postoperatively. The SMILE group was characterized by the most significant thickening in the central area and the least thickening in the mid-peripheral area; while the FS-LASIK group was characterized by the most significant thickening in the paracentral area and the least thickening in the mid-peripheral region. At 1 wk, 1, 3, and 6 mo postoperatively, within the 0-7 mm corneal area, the △CET for both the SMILE and FS-LASIK groups was correlated with the preoperative spherical equivalent.CONCLUSION: Within 6 mo postoperatively, both SMILE and FS-LASIK showed a similar trend in epithelial thickening but with distinct characteristics. The change in corneal epithelial thickness for both procedures was positively correlated with the preoperative diopter.