Effect of flap homogeneity on higher-order aberrations induction after femtosecond LASIK for myopia

Abstract

Purpose: To assess the relevance of the homogeneity of femtosecond laser flap thickness regarding induction of higher-order aberrations (HOAs).

Setting: Clínica Rementería & Clínica Novovisión, Madrid, Spain.

Design: Prospective observational study.

Methods: Two hundred thirty-one patients underwent in situ keratomileusis using 5 different femtosecond lasers. The flap thicknesses were measured using anterior segment optical coherence tomography 3 months postoperatively. The same masked observer measured 6 symmetrical points nasally and temporally 1.0 mm, 2.0 mm, and 3.0 mm from the center of the flap in each case. HOAs induced in the cornea were measured using tomography.

Results: Positive and significant correlations were found between HOA induction and the flap thickness heterogeneity 3.0 mm from the center of the flap. Pearson correlation coefficients for the induction of HOAs were third-order 0.17112 (P = .0224), fourth-order 0.22474 (P = .0026), fifth-order 0.16449 (P = .0282), coma-like 0.17370 (P = .0204), and total HOAs 0.18182 (P = .0151).

Conclusions: The amount of flap-thickness heterogeneity at 3.0 mm from the center of the flap created using femtosecond lasers was correlated with the magnitude of the HOAs induced.