Analysis of corneal higher-order aberrations and topographic patterns of effective optical zone at five years after FS-LASIK and SMILE for myopia

Introduction

To assess corneal higher-order aberrations (HOAs) at five years after femtosecond laser-assisted in situ keratomileusis (FS-LASIK) and small incision lenticule extraction (SMILE) for myopia, and to investigate correlative factors of myopic regression combined with morphology of effective optical zone (EOZ).

Methods

Data of 116 and 126 eyes receiving FS-LASIK and SMILE were collected in this cross-sectional study at five years postoperative, including refractive outcome, corneal topography, HOAs, epithelial thickness (ET), and Quality of Vision (QoV) questionnaire. Basing on the morphology of EOZ, curvature maps were classified into uniform, bowtie, semicircular, keyhole, and irregular patterns.

Results

FS-LASIK group demonstrated greater spherical aberration of total and anterior cornea at 4 and 6 mm than SMILE group (P < 0.050). Compared to uniform group (55.37 %), semicircular group (19.42 %) exhibited greater anterior and posterior horizontal coma at 6 mm (P < 0.050), the former was associated with horizontal decentration (r=-0.723, P < 0.050). Keyhole group (10.33 %) tended to have more negative spherical aberration of total and anterior cornea at 4 mm (P < 0.050) and more obvious focusing difficulties (P < 0.050). In high myopia patients, keyhole pattern showed a 21.323-folds probability of myopic regression compared to uniform pattern (P < 0.050). For every 1 μm increase in the discrepancy between central and pericentral ET, the possibility of myopic regression increased by 29.3 % (P < 0.050).

Conclusions

SMILE seemed to offer advantages in less HOAs than FS-LASIK. To improve visual quality for high myopia patients, it is essential to focus on centration to achieve regular EOZ, as well as monitoring epithelial remodeling to prevent myopic regression.