To assess the relevance of the homogeneity of femtosecond laser (FSL) flap thickness regarding induction of higher order aberrations (HOAs).
Clínica Rementería & Clínica Novovisión, Madrid, Spain.
Prospective, observational study.
Two hundred thirty-one patients who underwent in situ keratomileusis using five different FSLs. The flap thicknesses were measured using anterior-segment optical coherence tomography 3 months postoperatively. The same masked observer measured six symmetrical points nasally and temporally 1, 2, and 3 millimeters from the center of the flap in each case. HOAs induced in the cornea were measured using tomography.
We found positive and significant correlations between HOA induction and the flap thickness heterogeneity 3 millimeters from the center of the flap. Pearson’s correlation coefficients for the induction of HOAs were: third-order 0.17112 (P=0.0224), fourth-order 0.22474 (P=0.0026), fifth-order 0.16449 (P=0.0282), coma-like 0.17370 (P=0.0204), and total HOAs 0.18182 (P=0.0151).
The amount of flap-thickness heterogeneity at 3 millimeters from the center of the flap created using FSLs is correlated with the magnitude of the HOAs induced.