Increased higher-order optical aberrations after laser refractive surgery: A problem of subclinical decentration

Abstract

Purpose To study the clinical and theoretical effects of subclinical decentrations on the optical performance of the eye after photorefractive laser surgery. Setting Department of Ophthalmology, University of Dresden, Dresden, Germany. Methods Ocular aberrations were determined before and 1 month after uneventful photorefractive keratectomy (PRK) with the Multiscan laser (Schwind) in 10 eyes of 8 patients. The corrections ranged from –2.5 to –6.0 diopters, and ablation zones of 6.0 mm and larger were used. The measured wavefront errors were compared to numerical simulations using the individually determined decentrations and currently used ablation profiles. Results The PRK-induced aberrations were significantly greater than the preoperative aberrations. The numerically calculated increase in the higher-order optical aberrations correlated with the clinical results, demonstrating a major increase in coma- and spherical-like aberrations. Subclinical decentration (less than 1.0 mm) was found to be a major factor in increased coma-like and spherical-like aberrations after corneal laser surgery. Conclusion To minimize higher-order optical errors, special efforts to center the ablation zone are necessary; for example, by eye-tracking systems that consider the visual axis.