Survival analysis of myopic regression after small incision lenticule extraction and femtosecond laser‑assisted laser in situ keratomileusis for low to moderate myopia

Background:To report the predictive factors of myopic regression in patients who had undergone small incision lenticular extraction(SMILE)and femtosecond laser-assisted laser in situ keratomileuses(FS-LASIK)after 3–12 months of follow-up.Methods:This retrospective case series study recruited patients with a subjective sphere of−1.00 to−6.00 D myopia.SMILE was performed in 1629 eyes of 1629 patients with a subjective refraction spherical equivalent(SEQ)of−4.57±1.20 D and 1414 eyes of 1414 patients with a subjective SEQ of−4.53±1.26 D in FS-LASIK.Refractive outcomes were recorded at 1 day,1 week,and 1,3,6,and 12 months postoperatively.Predictors affecting myopic regression and other covariates were estimated with a Cox proportional hazard(Cox PH)model for the two surgical methods.Results:At 12 months,no significant difference was evident in the efficacy(P=0.934),predictability(P=0.733),or stability(P=0.66)between FS-LASIK and SMILE.The survival rates were 83.7%in the FS-LASIK group and 88.1%in the SMILE group.Multivariate analysis by the Cox PH model revealed a similar probability of postoperative myopic regression with SMILE or FS-LASIK(P=0.630).Predictors of myopic regression included preoperative higher-order aberration root mean square with 3 mm pupil diameter(pre-HOA-RMS3)(P=0.004),anterior chamber depth(ACD)(P=0.015),pre-subjective sphere(P=0.016),corneal diameter(P=0.016),optical zone(OZ)(P=0.02),and predicted depth of ablation(DA)(P=0.003).Conclusion:SMILE and FS-LASIK had a similar risk of myopic regression for low to moderate myopia.Pre-HOA-RMS3,ACD,pre-subjective sphere,corneal diameter,OZ,and predicted DA were predictors of myopic regression.