Stromal remodeling and lenticule thickness accuracy in small-incision lenticule extraction: One-year results

Purpose: To prospectively characterize the stromal thickness changes during the first year after myopic small-incision lenticule extraction using spectral-domain optical coherence tomography (SD-OCT). Setting: Department of Ophthalmology, Kepler University Hospital, Linz, Austria. Design: Prospective case series. Methods: This study evaluated eyes that had small-incision lenticule extraction to treat myopia or myopic astigmatism. A high resolution SD-OCT system (RS 3000 Advance) in conjunction with a custom image-segmentation algorithm was applied to directly measure stromal thickness within the central 5.0 mm corneal zone. Measurements were obtained preoperatively and postoperatively at 1 day, 1 week, 6 weeks, 3 months, 6 months, and 1 year. Results: The study enrolled 42 eyes of 21 patients. The mean surgical refractive correction was -4.94 diopters +/- 1.75 (SD). Postoperatively, the stromal thickness showed a significant decrease during the first 6 weeks, which amounted to a mean of 10.4 +/- 6.3 mu m at the apex (P < .001). Subsequently, the central stroma thickened by a mean of 8.8 +/- 5.9 mu m up until the 1-year follow-up (P < .001). One year postoperatively, the mean observed central stromal thickness reduction was 18.7 +/- 5.7 mu m smaller than the planned lenticule thickness. This difference was smallest 6 weeks postoperatively (mean 9.8 +/- 7.8 mu m). Conclusions: Significant anatomic changes in the corneal stroma were detected during the first year after small-incision lenticule extraction. The achieved lenticule thickness was systematically lower than planned, and the mismatch was more pronounced with higher lenticule thickness. Refractive outcomes did not appear to be influenced by lenticule thickness accuracy. (C) 2017 ASCRS and ESCRS.