Effects of effective optical zone and decentration on visual quality after smile for different astigmatism types

To compare the refractive outcomes and visual quality among different types of astigmatism following SMILE and evaluate effective optical zone (EOZ) features, decentration and their potential effects on visual quality.

This study included 101 left eyes of 101 patients who underwent SMILE. Patients were grouped according to astigmatism types (with-the-rule [WTR], against-the-rule [ATR] and oblique astigmatism) and decentered displacement (major axis > minor axis and major axis < minor axis). We compared the refractive outcomes, visual quality, EOZ and decentration 3 months postoperatively and analyzed correlations between corneal aberrations and EOZ parameters.

The visual and refractive outcomes were favorable in different types of astigmatism. The induced corneal aberrations, EOZ and total decentration were comparable among three groups (all p >.05). There was a strong positive correlation (r =.828, p <.001) between preoperative cylinder axis and the angle of EOZ. The postoperative induced changes in spherical aberration (0.02 ± 0.15 vs. 0.08 ± 0.13, p =.037), coma (0.22 ± 0.27 vs. 0.36 ± 0.25, p =.010), total HOAs (0.28 ± 0.24 vs. 0.42 ± 0.31, p =.009) and LOAs (0.16 ± 0.62 vs. 0.49 ± 0.84, p =.023) were fewer in group with greater decentered displacement along the major axis than the minor axis.

Favorable outcomes were observed in different types of astigmatism. Postoperative refractive errors, visual acuity, and induced corneal aberrations showed no significant differences between groups with WTR, ATR, and oblique astigmatism. The angle of EOZ was closely associated with cylinder axis. EOZ provided greater tolerance to decentration, with fewer induced corneal aberrations along the major axis compared to the minor axis. The combined impacts of EOZ and decentration on visual quality should be noted.