SMILE After DALK to Reduce Residual Refraction: Two-Year Results

Purpose: To determine the two-year results of small incision lenticule extraction (SMILE) for correcting post-keratoplasty myopia and myopic astigmatism.MethodsIn this case-series study, 10 eyes of 10 patients with a 6-10-year history of successful deep lamellar keratoplasty (DALK) underwent SMILE using VisuMax laser platform. Ophthalmologic examinations and visual acuity and refraction measurement were done pre- and 1, 3, 6, 12, and 24 months postoperatively. Pentacam and Sirius imaging was done in the first and last follow-up session.ResultsThe mean age of the patients was 39.60±7.86 years. Six subjects were male. After two years, uncorrected distance visual acuity did not change in one eye and improved 1-6 lines in other eyes. Corrected distance visual acuity decreased in one eye, did not change in four eyes, and improved 1-8 lines in other eyes. The mean decrease of spherical equivalent, spherical error, and cylinder power was 1.92±1.96 diopter (D) (P=0.013), 0.70±3.05D (P=0.213), and 2.42±2.91D (P=0.024), respectively. The vector mean target induced astigmatism, surgical induced astigmatism, and difference vector was 1.30D@44˚, 1.11D@24˚, and 0.86D@73˚, respectively. Two years after surgery, vertical coma, horizontal coma, and spherical aberration increased by 0.44±0.51, 0.23±0.32, and 0.02±0.16µm respectively (all P>0.05) while trefoil reduced by 0.29±0.75µm (P=0.428).ConclusionSMILE is a successful procedure for reducing refraction and astigmatism after DALK in patients with moderate myopia and moderate to severe astigmatism and improves the visual acuity in these patients. Axis rotation during surgery may result in under-correction of astigmatism. Refinement of SMILE treatment nomogram for post-DALK cases seems necessary.