DYNAMICS OF ABLATION PLUME PARTICLES GENERATED DURING EXCIMER-LASER CORNEAL ABLATION

Background and Objective: Although the empirical characteristics of Ar F excimer laser corneal ablation have been well documented, the exact ablation mechanisms are not well understood. The present paper reports a quantitative analysis of corneal ablation plumes using in situ time resolved laser light scattering and Raman spectroscopy. Study Design/ Materials and Methods: Bovine corneas were used as the ArF excimer las er ablation targets. Light scattering data were recorded from the abla tion plume as a function of height above the tissue surface and as fun ction of delay time with respect to the ablative ArF laser pulse. Resu lts: Raman spectra of the ablation plume allow identification of the p articles as water. Mean plume particle diameters are found to decrease with height, while the particle volume fractions are relatively const ant. The total volume of plume particles correlates well with the tota l volume of water in the ablated corneal tissue. Conclusion: The findi ng of a non-evolving plume composed of water spherules, combined with the excellent agreement between total volume of water in the plume and the content of water in the ablated corneal tissue, support the conce pt of photodecomposition or ''cold ablation'' for corneal tissue durin g ArF excimer laser ablation. (C) 1995 Wiley-Liss, Inc.