Corneal Remodeling After Myopic SMILE: An Optical Coherence Tomography and In Vivo Confocal Microscopy Study

PURPOSE: To study corneal remodeling during the first 6 months after myopic small incision lenticule extraction (SMILE) with a 10% overcorrection nomogram, by spectral-domain optical coherence tomography (SD-OCT) and in vivo confocal microscopy (IVCM). METHODS: This prospective non-randomized observational study included 60 eyes from 30 patients treated by SMILE for low to moderate myopia. A 10% overcorrection nomogram was applied for all eyes. Epithelial and corneal thickness maps were obtained within the central 6 mm, by SD-OCT, at each visit. Lenticule thickness was calculated by subtracting the postoperative central stromal thickness from the preoperative central stromal thickness. IVCM was performed at each visit. RESULTS: The mean surgical refractive correction was −3.99 ± 1.50 diopters (D) before and −0.09 ± 0.37 D after surgery. Central epithelial thickness increased from 53.7 ± 4.0 to 57.1 ± 4.1 µm at 6 months after SMILE ( P < .001). The measured lenticule thickness was 16 ± 6.1 µm less than the programmed lenticule thickness ( P < .001). Both central epithelial hyperplasia and the mismatch between measured and programmed lenticule thickness were positively correlated to the degree of myopia ( r 2 = 0.60, P < .001 and r 2 = 0.47, P < .001, respectively). Fibrosis at the interface was not correlated with epithelial thickening ( r 2 = 0.06, P = .29) or lenticule thickness error ( r 2 = 0.07, P = .22). CONCLUSIONS: Both epithelial thickening and the mismatch between the targeted and achieved lenticule thickness resulted in a slight undercorrection with a 10% overcorrection nomogram in low and moderate myopia. Fibrosis at the interface was not responsible for lenticule thickness error. Additional overcorrection is required to increase accuracy. [ J Refract Surg . 2020;36(9):597–605.]