Abstract
PURPOSE: To compare the degree of myopic regression after myopia correction with either femtosecond laser-assisted in situ keratomileusis (FS-LASIK) or small-incision lenticule extraction (SMILE) over 18 months. METHODS: Patients undergoing FS-LASIK or SMILE surgery for myopia correction were retrospectively recruited. The propensity scores were used to match patients by age and preoperative manifest spherical equivalent (SEQ) from these 2 groups. Myopic regression was analyzed using the Cox proportional hazard model. RESULTS: A total of 416 eyes of 416 patients undergoing FS-LASIK and 416 eyes of 416 patients undergoing SMILE were matched. Using 1-month SEQ as baseline, the SEQ regression values after FS-LASIK were 0D, -0.17 ± 0.69D, -0.24 ± 0.65D, -0.31 ± 0.65D, -0.32 ± 0.63D, and -0.33 ± 0.62D and the SEQ regression values after SMILE were 0D, -0.07 ± 0.75D, -0.18 ± 0.77D, -0.23 ± 0.82 D, -0.21 ± 0.77D, and -0.24 ± 0.68D at 1, 3, 6, 9, 12, and 18 months, respectively. The Cox proportional hazard model showed that preoperative manifest SEQ ( P = 0.021) and designed optical zone ( P = 0.048) are significant predictors. The selected surgical procedure had no significant effect on predicting myopic regression ( P = 0.470). The cumulative survival rates of myopic regression were 54.74% and 42.10% in the FS-LASIK group and 58.66% and 43.83% in the SMILE group, at 12 and 18 months, respectively (log-rank test, P = 0.11). CONCLUSIONS: After matching based on age and preoperative manifest SEQ, we found that higher myopia and a smaller optical zone contribute significantly to the development of myopic regression after undergoing FS-LASIK or SMILE surgery at 18 months. The selected surgical procedure, however, does not affect the likelihood of myopic regression.