Time-dependent changes in corneal biomechanics after small incision lenticule extraction: an in vivo study.

Background: This study aimed to investigate the in vivo temporal changes in corneal biomechanical properties following small-incision lenticule extraction (SMILE).

Methods: This retrospective study included 30 myopic patients who underwent SMILE with preoperative and postoperative ocular examinations (at 1 week, 1 month, 3 months, and 6 months) including Pentacam and corneal visualization Scheimpflug technology (Corvis ST) at 5 time points over a 6 months period. The corneal elastic modulus was calculated according to the air-puff force and corneal apical displacement from Corvis ST. All measured values, which included the corneal elastic modulus, 37 dynamic corneal response (DCR) parameters including the stiffness parameters at the first applanation (SPA1), and 15 tomographic parameters including the Belin/Ambrosio enhanced ectasia total deviation index (BAD_D), at 5 time points were compared.

Results: Compared to preoperative baseline, 14 corneal tomographic parameters and 30 DCR parameters showed statistically significant differences post-SMILE (P < 0.05). Specifically, 7 tomographic and 17 DCR parameters demonstrated increases, whereas the SPA1 and corneal stress-strain index showed decreases. All parameter changes exceeded 1% of preoperative values (P < 0.05). Over time, they exhibit a trend of initial decrease followed by a gradual stabilization: the BAD_D, anterior corneal asphericity and the corneal elastic modulus attained their maximum at 1 week postoperatively, then declined, and showed stabilization by 3 months (P < 0.05).

Conclusions: Compared with preoperative data, the corneal elastic modulus, the Belin/Ambrosio enhanced ectasia total deviation index, and anterior corneal asphericity in human corneas showed a significant increase in the short term after surgery, and gradually stabilized at a little bit higher than preoperative levels. These observations underscore the critical need for vigilant monitoring of corneal biomechanics post-SMILE to refine surgical outcomes and enhance patient care.