Abstract

While the ablation of corneal tissue by pulsed 193-nm excimer laser light has been extensively studied for various clinical uses, the underlying laser-tissue interaction remains poorly understood. We have examined the process in vitro by several methods: monitoring the photoacoustic deflection of a He-Ne laser probe beam passing tangentially above the corneal irradiation site, examining the temporal profile of excimer pulses reflected from or transmitted through corneal samples in ablation conditions, and surveying the ArF laser light scattered from the ablation target. The photoacoustic technique indicates that the corneal etch process is consistent over an initial train of pulses, implying that a cumulative incubation effect does not occur with ablation of this tissue. Reflectometry measurements reveal that the trailing portion of the reflected excimer pulse is strongly attenuated. This reflected pulse clipping becomes progressively more pronounced with increasing incident pulse fluence, indicating dynamic optical properties of the material during laser irradiation. Scattered laser light signals and transmitted pulse profiles have been acquired to assess the cause of this reflected pulse distortion.

© 1991 Optical Society of America