Determination of Excimer Laser Ablation Rates of Corneal Tissue using Wax Impressions of Ablation Craters and White-Light Interferometry

BACKGROUND AND OBJECTIVE: Efforts to better understand the processes of corneal ablation are aided by a means to precisely measure corneal tissue ablation rates. MATERIALS AND METHODS: A white-light interferometer was used to measure the depth of argon fluoride laser ablation craters and wax impressions of the ablation craters. The technique was validated using polymethylmethacrylate (PMMA), and was then used to measure the ablation rate of bovine corneal tissue. RESULTS: The ablation rate was measured as 0.47 μm/pulse from direct measurement of the PMMA ablation craters and as 0.48 μm/pulse from measurement of the corresponding wax impressions. The ablation rate of bovine corneal tissue was found to be 0.90 μm/pulse. CONCLUSIONS: Wax impressions provide a valid representation of ablation craters. The ablation depth of corneal tissue and PMMA was found to increase linearly with increasing number of laser pulses, and the slope of the regression lines provided a measure of the laser ablation rate.