ADVANCES IN THE PHYSICAL UNDERSTANDING OF LASER SURGERY AT 6.45 MICRONS

We previously presented a model that attributes the wavelength-dependence of FEL tissue ablation to partitioning of absorbed energy between protein and saline. This energy-partitioning subsequently influences the competition between protein denaturation and saline vaporization. The original model approximated cornea as a laminar material with a 50:50 saline-to-protein volume ratio. We have now refined the microscopic geometry of the model in two ways: (1) cornea is represented as a saline bath interpenetrated by a hexagonal array of protein fibrils; (2) the volume ratio is matched to the measured value, 85:15. With this volume fraction, the specific absorption coefficient for protein is much larger than previously reported. Thus, the fibril array model magnifies the differences between wavelengths that target saline versus protein. We will discuss: (1) the consistency of this model with previous, seemingly conflicting, experimental data; (2) predictions of the model, with a particular emphasis on the role of laser intensity; and (3) the experiments needed to test these predictions