Calculated and measured endothelial temperature histories of excised rabbit corneas exposed to infrared radiation

Abstract

This paper reports calculation of the endothelial and epithelial temperature increases caused by exposing the cornea to radiation from three infrared laser systems: CO 2 holmium and erbium. Data are presented for a variety of exposures and beam diameters. The calculations assume that the lasers are operated with a Gaussian beam intensity profile and the radiation is absorbed according to the Beer-Lambert law. We show that the absorption lengths of some of these laser lines are sufficiently long that the endothelial temperature rise is very close to that of the epithelium. The efficacy of the theoretical model is tested by comparing the calculations with measurements on excised corneas exposed to CO 2 laser radiation. Both a liquid crystal technique and a thermocouple were used to measure the temporal and spatial variations of endothelial temperature. The experimental and theoretical values are in resonable accord which gives added confidence in the calculations for other laser systems and exposures. The results presented here show that infrared laser exposure safety standards should address the possibility of endothelial damage.