Epithelial Thickness Profile Changes Following Small Incision Refractive Lenticule Extraction (SMILE) for Myopia and Myopic Astigmatism

PURPOSE: To evaluate the epithelial thickness profile changes following small incision refractive lenticule extraction (SMILE) and study their correlation with the amount of myopia corrected. METHODS: Epithelial thickness was measured in nine zones with spectral-domain anterior segment optical coherence tomography (SD-OCT) across a 6-mm diameter preoperatively and at 1 day, 2 weeks, and 3 months postoperatively. The observed changes were correlated with the degree of myopia corrected. RESULTS: The study included 100 eyes from 50 eligible patients (32 females, 18 males) with a mean age of 24.4 ± 2.8 years. Thirty-eight eyes underwent SMILE for low (spherical equivalent [SE] < −4.00 diopters [D]), 44 eyes for moderate (SE −4.00 to −6.00 D), and 18 eyes for high (SE > −6.00 to −10.00 D) myopia with 6.71 ± 1.65, 6.82 ± 0.21, and 6.44 ± 0.2 mm optical zones, respectively. At 3 months, a statistically significant epithelial thickness increase was observed in the central zone (6.83% for low, 9.26% for moderate, and 12.7% for high myopia, P < .05 for all groups) and superior zone (3.98% for low, 7.82% for moderate, and 9.87% for high myopia) across all three groups, which correlated positively with the degree of myopia corrected ( r 2 = 0.723 for central zone, r 2 = 0.585 for superior zone, P < .001 for both zones). None of the other zones showed any statistically significant changes at 3 months. Four eyes of two patients with high myopia (SE > −8.00 D) had regression due to significant epithelial thickening. CONCLUSIONS: Preliminary results suggest that epithelial thickness profile changes after SMILE may have an impact on the refractive outcome in the long-term postoperative period, especially in higher degrees of myopia. [ J Refract Surg. 2016;32(7):473–478.]