Early visual quality outcomes after small-incision lenticule extraction surgery for correcting high myopic astigmatism

Background: To evaluate early optical quality outcomes after small-incision lenticule extraction (SMILE) surgery for correcting high myopic astigmatism. Methods: This retrospective study enrolled 55 eyes from 37 patients who had preoperative myopic astigmatism of >= 2.00 diopters (D) who had been treated with SMILE surgery. Preoperatively, the mean cylinder was - 2.41 +/- 0.54 D (range, - 2.00 D to - 4.50 D). The preoperative and postoperative visual outcomes, refraction, and higher-order aberration (HOA) at 1 and 3 months were compared. Refractive astigmatism changes were analyzed by the Alpins vector method. Results: Three months after SMILE surgery, the average cylinder was - 0.14 +/- 0.31 D, and the average astigmatism vector was - 0.09 D x 6.34 degrees. The angle of error (AofE) was limited to within +/- 10 degrees, and the magnitude of error was limited to within +/- 1.0 D in all patients. The correction index (CI) was 0.98 +/- 0.07, the index of success (IOS) was 0.08 +/- 0.13, and the flattening index (FI) was 0.97 +/- 0.07. Significant positive correlations were found between IOS and vertical bar AofE vertical bar (P = 0.000); negative correlations were found between FI and vertical bar AofE vertical bar (P = 0.000). The postoperative total HOA, spherical aberration, vertical coma aberration, and trefoil 30 degrees were increased significantly compared with preoperative measurements, and the increase in HOA was closely related to preoperative astigmatism (P < 0.05). Conclusions: SMILE has preferable outcomes for correcting high myopic astigmatism. Axis rotation during the surgery might influence the undercorrection of astigmatism. The increase of HOA after surgery is related to preoperative astigmatism.