Within-cohort associations between corneal epithelial remodeling and anterior corneal higher-order aberrations after FS-LASIK and KLEx (SMILE): a two-cohort descriptive study

To describe corneal epithelial remodeling patterns after femtosecond LASIK (FS-LASIK) and keratorefractive lenticule extraction (KLEx; SMILE in this study), and to evaluate within-cohort associations between epithelial thickness changes and anterior corneal higher-order aberrations (HOAs). This study included 245 patients (138 eyes in the SMILE cohort and 107 eyes in the FS-LASIK cohort; right eyes only). Corneal epithelial thickness in the central, paracentral, and mid-peripheral zones was measured preoperatively, 1 month, and 3 months postoperatively using optical coherence tomography (OCT). Corneal HOAs were assessed using the Pentacam system with a 6 mm pupil diameter. Repeated-measures analysis of variance and Spearman correlation analyses were used to characterize postoperative changes and examine within-cohort associations between epithelial remodeling and HOAs. In both cohorts, postoperative epithelial thickening was observed in the central and paracentral zones; in the SMILE cohort, thickening was also observed in the mid-peripheral zone. The spatial distribution of epithelial thickening differed between cohorts, and the magnitude of thickening varied by zone across time points. Both cohorts demonstrated postoperative changes in HOAs. In the SMILE cohort, changes in spherical aberrations (Z40, Z60) and coma-related terms (Z3−1, Z3−3) were observed over follow-up. In the FS-LASIK cohort, HOA changes showed greater regional variability across time points. Within-cohort correlation analyses indicated that epithelial thickening in the SMILE cohort was positively associated with spherical aberrations and negatively associated with coma-related terms, whereas correlations in the FS-LASIK cohort were generally weaker and region-dependent. Across two clinical cohorts undergoing SMILE or FS-LASIK, postoperative epithelial thickening and changes in anterior corneal HOAs were observed, with measurable within-cohort associations between epithelial remodeling and HOA metrics. Because preoperative refractive status (spherical equivalent) differed markedly between cohorts, these findings should be interpreted as descriptive patterns and within-cohort associations rather than evidence of isolated procedure effects or between-procedure superiority.