Interface healing and its correlation with visual recovery and quality of vision following small incision lenticule extraction.

PURPOSE: To study the time course of interface healing and its correlation with visual acuity, modulation transfer function (MTF), and aberrations after myopic small-incision lenticule extraction (SMILE) correction.

METHODS: Seventy-eight eyes of 78 patients (1 eye per patient) with a mean age of 25.7 years and mean spherical equivalent (SE) of -3.74D, undergoing bilateral SMILE procedure, were included in this study. On postoperative day 1, 2 weeks, and 3 months, dilated retroillumination photographs were taken and morphology of corneal interface was graded by comparing them with 5 standard templates representing 5 grades of interface roughness (IRG): IRG - 0 (clear), IRG - 1 (mild), IRG - 2 (moderate), IRG - 3 (severe), and IRG - 4 (severe IRG with Bowman's folds in visual axis). Pearson's correlations were computed to study correlation associations, and Wilcoxon signed-rank test was used for intragroup comparison of means. P ≤ 0.05 was considered statistically significant.

RESULTS: At 3 months, 90.70% eyes were Grade 0 while 9.30% eyes still had Grade 2 interface granularity. Mean IRG significantly improved from 2.47 ± 0.57 at day 1 to 0.62 ± 0.53 at 3 months (P = 0.00). At day 1, pre-SE showed a significant positive correlation with IRG; however, mean postoperative corrected distant visual acuity (CDVA, in decimal), corneal Strehl ratio (SR), and MTF showed weak but significant negative correlation with IRG (r2 = 0.28 for SE, -0.052 for CDVA, -0.017 for SR, and -0.39 for MTF, respectively, P < 0.05 for all correlations). At 2 weeks and 3 months, corneal MTF continued to show a significant negative correlation, whereas other parameters did not show any correlation with IRG.

CONCLUSION: Visual quality and corneal MTF may be significantly affected by the IRG in the immediate postoperative period after SMILE and may take 3 months or more for complete recovery.