Changes in asphericity of anterior and posterior corneal surfaces for mild-moderate and high myopia after topography-guided FS-LASIK

Abstract

Purpose: To compare changes in asphericity of anterior and posterior corneal surfaces for different myopia patients after corneal topography-guided femtosecond-assisted laser in situ keratomileuses (FS-LASIK), and to analyze correlations between asphericity of corneal surfaces and preoperative spherical equivalence (SEQ).

Methods: In this prospective study, 59 patients who underwent corneal topography-guided FS-LASIK surgery were enrolled and divided into the mild-moderate myopia group (67 eyes) and the high myopia group (44 eyes). Postoperative follow-ups were performed at 1, 3, and 6 months. Postoperative changes in aspherical coefficient (Q values), corneal higher-order aberrations (HOAs), and spherical aberrations (Z₄⁰) were compared between the two groups. Relevance between Q value changes and SEQ, HOAs, and Z₄⁰ as well as between SEQ and changes of HOAs and Z₄⁰ was analyzed.

Results: There was a significant increase in Q values of the anterior (each diameter) and posterior (6-8 mm) corneal surface in both groups than before surgery (P < 0.001). Q values of corneal anterior (each diameter) and posterior (7-9 mm) surface in the high group were considerably larger than the mild-moderate group (P < 0.05). Corneal anterior surface HOAs and Z₄⁰ values in the high group largely exceeded those of the mild-moderate group (P < 0.001). The preoperative SEQ was linearly correlated with postoperative anterior Q change (ΔQ), HOAs change (ΔHOAs), and spherical aberration change (ΔZ₄⁰).

Conclusion: The changes of corneal asphericity in patients with high myopia were greater than mild-moderate myopia, with more corneal HOAs and Z₄⁰ introduced when corneal topography-guided FS-LASIK was conducted.

Keywords: Asphericity; Corneal topography; FS-LASIK; Higher-order aberrations; Myopia; Q values.