Temporal redistribution of cap and residual stromal thickness following small-incision lenticule extraction.

PURPOSE: To investigate corneal sublayer alterations during the postoperative period after small-incision lenticule extraction (SMILE). SETTING: Synslaser clinic, Oslo, Norway. STUDY DESIGN: Retrospective. METHODS: The right eyes of 51 patients who underwent SMILE for treating myopia were included. The thicknesses of the corneal epithelium, cap, stromal part of the cap (StromaCap), residual stromal bed (StromaRes) and total stroma (StromaTot) were measured using spectral-domain optical coherence tomography at 1 day, 1 week, 1 month, 3 months and 6 months postoperatively. Postoperative changes in the corneal sublayer thicknesses were analysed and correlated with changes in spherical equivalence and anterior and posterior keratometry (K). RESULTS: From 1 day to 6 months postoperatively, the corneal epithelium, cap, StromaCap, StromaRes and StromaTot thickness increased from 54.4±4.0 µm to 57.3±5.2 µm; 137.1±5.5 µm to 140.3±5.1 µm; 82.7±5.9 µm to 82.8±6.3 µm; 375.0±40.8 µm to 381.4±30.6 µm; and 457.6±41.1 µm to 462.1±36.7 µm, respectively. Between 1 and 6 months postoperatively, the increase in anterior K correlated significantly with the thickening of the cap (r=0.37, p=0.03) and the stromal component of the cap (r=0.36, p=0.04) within the central cornea. CONCLUSIONS: The post-SMILE remodeling behaviour between the anterior (StromaCap) and posterior (StromaRes) stroma were dissimilar. There was a significant correlation between changes in anterior K and the central cap and the stromal component of the cap. This might be the result of biomechanical changes, tissue remodeling, and wound healing or a combination of some or all of the aforementioned processes.