Efficacy, predictability, and safety of small incision lenticule extraction: 6-months prospective cohort study

Background: To report our experience with small incision lenticule extraction (" SMILE") for myopia treatment. Methods: In this prospective clinical study, we evaluated 447 eyes from 224 patients with myopia, with and without astigmatism. We followed the patients for 6 months after SMILE. Results: The mean (+/- standard deviation, SD) spherical equivalent was -6.75 +/- 1.65 diopters (D) preoperatively and -0.21 +/- 0.37 D at 6 months postoperatively. Our data showed that 97.9% of eyes were within +/- 1.0 D and 86.1% were within +/- 0.5 D of the intended correction. Furthermore, 79.8% had an uncorrected distance visual acuity (UDVA) of 0 logMAR or less (20/20 or better in the Snellen equivalent) 6 months after surgery. Additionally, 48.5% remained unchanged, 41% gained one line of corrected distance visual acuity (CDVA), 7.2% gained two lines of CDVA, 3.3% lost one line of CDVA, and 0.3% lost two or more lines of CDVA. Age was the only predictor for worsening UDVA at 6 months postoperatively in linear regression analyses (0.07 decrease logMAR per increased 10 years of age; P < 0.05). No predictor showed an association with error in spherical equivalent refraction at 6 months postoperatively. Conclusions: SMILE is an effective and safe refractive surgery. Age was the only predictor that influenced visual outcome, but its effect appeared clinically insignificant. Faster visual recovery is also expected with improved surgical technique.