The influence of preoperative corneal thickness on postoperative epithelial and biomechanical responses after FS-LASIK for high myopia

PURPOSE: To investigate the influence of preoperative corneal thickness on postoperative epithelial remodeling and corneal biomechanics in eyes undergoing FS-LASIK for high myopia (spherical equivalent ≤ –6.0 D). METHODS: This prospective, longitudinal study included 287 patients stratified into thin (< 528 μm, n=150) and thick (> 552 μm, n=137) cornea groups based on central corneal thickness (CCT). Only one eye per patient was randomly selected for analysis. All patients underwent FS-LASIK. Examinations including visual acuity, refraction, corneal topography, epithelial thickness mapping (AS-OCT), and dynamic biomechanical assessment (Corvis ST) were performed preoperatively and at 1, 3, 6, and 12 months postoperatively. RESULTS: Preoperatively, the groups were comparable in all parameters except CCT (p < 0.001). Postoperatively, the thin cornea group exhibited a significantly more myopic spherical equivalent at 3, 6, and 12 months (p < 0.001). Epithelial remodeling was more pronounced in the thin cornea group, characterized by greater central epithelial thickening and a larger central-to-paracentral thickness gradient (ΔC-P, ΔC-M). Biomechanically, the thin cornea group demonstrated significantly lower stiffness (SP-A1) and higher deformation metrics (DA Ratio 2mm, IR) postoperatively (all p < 0.001), while parameters like HC-Time and SSI showed no intergroup differences. No significant correlation was found between changes in biomechanical parameters and epithelial thickness. CONCLUSIONS: Thin corneas are associated with a more pronounced myopic shift, significant epithelial hyperplasia, and greater biomechanical weakening after FS-LASIK. However, the lack of direct correlation between biomechanical and epithelial changes suggests that other factors may also contribute to epithelial remodeling.