Far‐ultraviolet laser ablation of the cornea: Photoacoustic studies

Abstract

Wide bandwidth piezoelectric transducers made of thin (9 m̈m) polyvinylidene fluoride film have been used to make time-resolved measurements of the stress-wave generated by far-ultraviolet (193 nm) laser ablation in corneal tissue in vitro. At high fluence (∼ 250 mJ/cm²), ablation commences within 10 ns (± 5 ns) of the laser pulse and generates short acoustic impulses (∼ 30 ns). The time profile of the ablation, when coupled to the energy requirements for ablation from earlier work, allows the estimation of a temperature and a half-life for the thermal decomposition of the collagen in cornea. These values do not support a photo-thermal mechanism for the ablation under the experimental conditions.