Correction of Myopic Astigmatism With Small Incision Lenticule Extraction

PURPOSE: To evaluate the outcome after small incision refractive lenticule extraction (SMILE) in patients with myopic astigmatism. METHODS: Seven hundred seventy-five eyes from 403 patients with myopia treated with SMILE for a cylinder of 0.75 diopters (D) or more were identified from patient records. Six hundred sixty-nine eyes were defined as receiving low (< 2.5 D) and 106 eyes as receiving high (⩾ 2.5 D) astigmatic correction. Patients were examined before and 3 months after surgery. SMILE was performed with a Visumax femtosecond laser (Carl Zeiss Meditec, Jena, Germany). Preoperative and postoperative refractions were converted to polar values. Induced torsion and achieved corrections of sphere and cylinder were determined. RESULTS: In low astigmatism, the mean preoperative spherical equivalent (SE) was -7.57 ±1.67 D and the cylinder was -1.22 ± 0.49 D. Three months after surgery, SE was -0.19 ± 0.48 D from target, astigmatism was 0.17 ± 0.42 D undercorrected, and a small but significant torsion of the cylinder axis corresponding to 0.05 ± 0.37 D was found. The astigmatic undercorrection measured 13% per diopter of attempted correction. In high astigmatism, preoperative SE was -5.91 ± 2.56 D and cylinder was -3.22 ± 0.67 D. After surgery, the average astigmatic undercorrection was 0.59 ± 0.65 D, equivalent to 16% per diopter of attempted correction. No undercorrection in SE occurred and no torsion was found. CONCLUSIONS: SMILE in myopic astigmatism offers predictable correction of SE, but a small, significant undercorrection of the astigmatic error. The undercorrection increases with the attempted treatment. Only very little rotation of the cylinder axis was found.