Comparison of ocular higher-order aberrations after SMILE and Wavefront-guided Femtosecond LASIK for myopia

Background: To compare changes in higher-order aberrations (HOAs) following small incision lenticule extraction (SMILE) and wavefront-guided femtosecond laser-assisted in situ keratomileusis (WFG FS-LASIK), and to investigate correlations between preoperative spherical equivalence (SE) and components of HOAs affecting visual quality. Methods: Sixty-five myopic eyes from 38 patients were enrolled in the study retrospectively, either having undergone SMILE or WFG FS-LASIK. Uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), refractive error, and individual Zernike coefficients of 3rd-to 6th-order HOAs were measured before and 3 months after the surgeries and were compared using the Mann-Whitney test or Student's t-test. Additional generalized estimating equation analyses (GEE) were used to control for within-subject biases in individual Zernike coefficients between the right and left eyes of the same patients. Results: There was no significant difference in UDVA or CDVA after WFG FS-LASIK (Mean +/- SD: -0.02 +/- 0.07 and -0.04 +/- 0.22 respectively, in logMAR) and after SMILE (-0.01 +/- 0.06 and -0.04 +/- 0.04 respectively). However, greater vertical coma aberration was found after SMILE (p = 0.036). Preoperative SE was correlated to induced horizontal coma (r = -0.608, p = 0.001) in WFG FS-LASIK, and correlated to induced vertical coma (r = -0.459, p = 0.003) in SMILE. Conclusions: Both SMILE and WFG FS-LASIK can achieve planned visual outcomes in correcting myopia and myopic astigmatism. However, higher vertical coma was shown in SMILE than WFG FS-LASIK which might be a potentially impact factor for patients' vision under certain lighting conditions and needs further investigation.