Impact of corneal curvature on 2-year postoperative visual outcomes after small incision lenticule extraction for high myopia

Purpose High myopia requires precise surgical interventions to ensure optimal visual outcomes. Small Incision Lenticule Extraction (SMILE) has proven effective for high myopia correction, but the long-term impact of corneal curvature on refractive outcomes remains exploring. This study aimed to investigate whether preoperative low mean corneal curvature (Km) might result in refractive overcorrection, and to evaluate its influence on the refractive status of highly myopic patients 2 years post-SMILE surgery. Methods 67 patients underwent SMILE surgery were categorized into Low Corneal Curvature (n = 31) and Normal Corneal Curvature groups (n = 36) based on preoperative corneal curvature (Km <= 42.0D or 42.0D < Km < 46.0D). Corneal curvature, uncorrected distance visual acuity, and surgical parameters were analyzed over a 2-year follow-up period. Changes in corneal morphology were evaluated on Scheimpfug imaging. Results No significant differences were observed in uncorrected distance visual acuity (UDVA) or changes in UDVA (triangle UDVA) at various time points between the two groups. However, differences in spherical equivalent (SE) were identified at 1 week (0.06 +/- 0.47 vs. - 0.23 +/- 0.23, P = 0.019) and 1 month (0.04 +/- 0.41 vs. - 0.22 +/- 0.39, P = 0.007), indicating relative overcorrection in the Low Corneal Curvature group. Significant disparities in corneal curvature were consistently noted between the groups throughout the 2-year postoperative period, with the Low Corneal Curvature Group exhibiting a greater change in Km compared to the Normal Corneal Curvature Group from 1 to 2 years (0.20 +/- 0.17 vs. 0.12 +/- 0.17, P = 0.003). Conclusion Corneal curvature significantly influences the refractive status of patients with high myopia at 2 years following SMILE surgery.