Long-term refractive outcomes and corneal remodeling after the SMILE surgery in patients with moderate to extra-high myopia.

PURPOSE: To assess long-term refractive stability and corneal remodelling in patients with moderate to extra-high myopia after the small-incision lenticule extraction (SMILE) surgery. METHODS: A retrospective analysis of 196 eyes was conducted, categorising them into three groups based on preoperative myopia: Group 1 (moderate myopia, 78 eyes), Group 2 (high myopia, 72 eyes), and Group 3 (extra-high myopia, 46eyes). The predicted and actual values of key parameters, including attempted spherical equivalent (SE), thinnest corneal thickness (TCT), and keratometry (K), were measured and compared 1 day and 3 years postoperatively. Correlations were analysed to evaluate refractive stability and corneal changes over time. RESULTS: One day postoperatively, the attempted SE correction closely matched the achieved SE in Group 1 (p = 0.225) and 2 (p = 0.235), but was significantly smaller than achieved SE in Group 3 (p = 0.002). At 3 years, Group 3 showed significant undercorrection (p < 0.001) and a greater deviation in predicted versus measured TCT reduction (p < 0.001). Similarly, Group 3 showed significant deviations in flat K values from the expected values at 1 day and 3 years (p < 0.0001), indicating greater corneal changes than those in the other groups. Correlation analysis revealed a strong association among preoperative spherical equivalent, postoperative keratometric changes, and long-term refractive outcomes (p < 0.0001). CONCLUSIONS: SMILE effectively provides short-term refractive correction for all myopia groups. However, long-term refractive stability is less predictable in patients with high myopia due to increased corneal remodelling. Developing personalised, predictive models for these patients could help ensure more stable long-term outcomes.