Comparison of corneal biomechanics in post-smile, post-LASEK, and normal eyes with Brillouin microscopy

To characterize corneal biomechanics in post-small-incision lenticule extraction (SMILE), post-laser-assisted subepithelial keratomileusis (LASEK), and normal eyes using Brillouin microscopy.

This study included myopic patients who underwent corneal refractive surgery (SMILE or LASEK) at least 1 month prior to ensure corneal stability. A total of 177 eyes (79 post-SMILE, 24 post-LASEK, and 74 untreated normal eyes) from 177 patients were evaluated using Pentacam HR and Brillouin microscopy for morphological and biomechanical assessment, respectively. Among them, 30 eyes (20 post-SMILE and 10 post-LASEK) from 30 participants underwent both pre- and post-operative Brillouin and Pentacam examinations, enabling within-subject comparisons. Corneal biomechanics were assessed using Brillouin modulus (BM), where lower values indicate weaker biomechanical properties.

No significant differences were observed in Central BM, Mean BM, or Max BM among the groups. Compared with the normal eyes, Min BM was significantly lower in the post-SMILE and post-LASEK groups (P = 0.004 and 0.002, respectively) and Max-Min BM significantly increased after SMILE and LASEK (both P < 0.001). In post-SMILE corneas, standardized deviation BM was significantly higher than in normal corneas (P < 0.001). Within-subjects comparisons (pre- vs post-operation) further confirmed above results. Multiple linear regression analysis revealed a negative correlation between Central BM and post-operative corneal thickness in post-SMILE corneas (coefficient = -0.016, P = 0.025). In the post-LASEK group, Max-Min BM showed a positive correlation with mean corneal curvature (coefficient = 0.031, P = 0.001).

SMILE and LASEK can induce localized changes in corneal biomechanics, as observed by Brillouin microscopy, while maintaining overall corneal biomechanics.