CHANGES IN CORNEAL DENSITOMETRY AND HIGHER ORDER ABERRATIONS AFTER FS-LASIK AND SMILE SURGERY

Abstract

Purpose: To compare long-term postoperative changes in corneal densitometry (CD) and higher-order aberrations (HOAs) after femtosecond laser–assisted in situ keratomileusis (FS-LASIK) and small incision lenticule extraction (SMILE). Methods: This prospective comparative study included 74 patients undergoing myopic correction with FS-LASIK (n = 37) or SMILE (n = 37). Corneal densitometry and HOAs were evaluated using Pentacam HR preoperatively and at 1, 6, and 12 months postoperatively. Total full-thickness average densitometry over the central 6 mm zone was analyzed. A multivariate analysis of covariance (ANCOVA) was executed to isolate the independent effect of the surgical modalities while controlling for baseline spherical equivalent (SE) and ablation depth/lenticule thickness. Intergroup comparisons and longitudinal changes were statistically analyzed. Results: Corneal densitometry values remained relatively stable following FS-LASIK, whereas a gradual increase was observed after SMILE over the 12-month follow-up, although intergroup differences did not reach statistical significance (p > 0.05). FS-LASIK induced a significantly greater increase in HOAs compared to SMILE (p < 0.05). The multivariate ANCOVA confirmed that the higher induction of HOAs in the FS-LASIK group was statistically significant (p = 0.031) independent of baseline variations in SE and ablation profiles. Conclusion: SMILE demonstrated a gradual increase in total corneal densitometry over 12 months, whereas FS-LASIK induced significantly higher HOAs (p < 0.05), suggesting fundamental differences in subclinical structural remodeling and wavefront optical pathways.