Visual Outcomes and Optical Quality After Femtosecond Laser Small Incision Lenticule Extraction: An 18-Month Prospective Study

PURPOSE: To investigate the long-term visual outcomes and optical quality after femtosecond laser small incision lenticule extraction (SMILE) for moderate to high myopia correction. METHODS: Fifty-four patients (37 women, 17 men) who underwent SMILE were enrolled in this prospective clinical study. Patient ages ranged from 18 to 40 years, with a mean spherical equivalent of -6.50 +/- 1.64 diopters. Data including refractive parameters, retinal image quality, intraocular scattering, and aberrations were collected at 6 and 18 months after surgery. Patient satisfaction was also evaluated. RESULTS: At 18 months after surgery, both the mean safety index and the efficacy index were 1.23 +/- 0.23 (range: 0.80 to 1.50); there was no significant difference with indices measured at 6 months (P > .05). No patient lost two or more lines of corrected distance visual acuity. Total higher-order aberrations (HOAs) and coma significantly increased after SMILE (P < .05), whereas total spherical aberrations and trefoil changed only slightly. The mean modulation transfer function cutoff frequency was 36.66 +/- 8.54 cycles per degree (cpd) before surgery and 37.81 +/- 6.89 cpd at 18 months postoperatively; the mean objective scatter index was 0.62 +/- 0.33 before surgery and 0.71 +/- 0.38 at 18 months postoperatively. No significant difference was found between the three time points (P > .05). Mean patient satisfaction was 9.31 +/- 0.64 (with a maximum score of 10). CONCLUSIONS: SMILE showed good safety, efficacy, and stability in correcting moderate to high myopia, and patients were highly satisfied. HOAs increased after SMILE, mainly due to the increase of coma, whereas retinal image quality and intraocular scattering barely changed.