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

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 (Z 4 0 ) were compared between the two groups. Relevance between Q value changes and SEQ, HOAs, and Z 4 0 as well as between SEQ and changes of HOAs and Z 4 0 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 Z 4 0 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 (Δ Q ), HOAs change (ΔHOAs), and spherical aberration change (ΔZ 4 0 ). Conclusion The changes of corneal asphericity in patients with high myopia were greater than mild–moderate myopia, with more corneal HOAs and Z 4 0 introduced when corneal topography-guided FS-LASIK was conducted.