Comparison of Forward Light Scatter Changes Between SMILE, Femtosecond Laser-assisted LASIK, and Epipolis LASIK: Results of a 1-Year Prospective Study

To investigate the characteristics of forward light scatter changes after small incision lenticule extraction (SMILE) and to compare these changes with those after femtosecond laser-assisted LASIK (femto-LASIK) and epipolis LASIK (epi-LASIK).A total of 303 eyes (SMILE group = 118 eyes, femto-LASIK group = 90 eyes, epi-LASIK group = 95) of 157 patients were included in this study. Forward straylight was measured preoperatively and 1 month, 6 months, and 1 year postoperatively using a C-Quant straylight meter (Oculus Optikgerate, Wetzlar, Germany).A significant increase in straylight was found in the femto-LASIK group only at 1 month after the procedure (P = .002), whereas significant increases were found in the epi-LASIK group at 1 month, 6 months, and 1 year after the procedure (P < .001). There were no significant increases in the straylight values after SMILE (P = .310) compared with the preoperative values, although the straylight values were slightly increased at 1 month. Significant differences in the postoperative-preoperative straylight value (Δlog[s]) changes were found between the SMILE, femto-LASIK, and epi-LASIK groups over the follow-up period (P < .001 for all). The correlations between the ablation depth/central corneal thickness ratios and the straylight values were statistically significant in the femto-LASIK and epi-LASIK groups, whereas no significant correlation between the lenticule thickness/central corneal thickness ratios and the stray-light values was found in the SMILE group.Forward straylight was slightly increased in the early stage after the femto-LASIK procedure and was significantly increased throughout the follow-up period after epi-LASIK surgery. The SMILE procedure appeared to have a smaller effect on forward light scatter within the 1-year follow-up period.