Influence of corneal curvature on calculation of ablation patterns used in photorefractive laser surgery

PURPOSE: The aim of this work was to clarify the influence of the effective illumination area and possible reflection losses that occur during laser-tissue interaction on the modeling of profiles for customized corneal ablation, such as wavefront-guided treatments. METHODS: The changes of the ablation depth per laser pulse due to the projection of a laser spot onto the corneal front surface and reflection losses at the air-tissue interface were calculated. RESULTS: Moving with a scanning-spot from the center of the cornea toward the limbus resulted in an increase of the effective illumination area and reflection losses, which led to a decrease in the ablation depth per laser pulse. The decrease of the ablation depth was strongly related to the initial radiant exposure and the corneal curvature radius. CONCLUSIONS: The corneal front surface must be taken into consideration for ablation profile calculations, especially in customized treatments, due to the strong dependence of the ablation depth on the corneal curvature.