Calculation of retinal temperature distributions resulting from laser irradiation of the eye: I. Continuous lasers.

The paper develops a simple analytic expression for the maximum temperature rise attained in the retina as a function of laser power, exposure duration, retinal absorption parameters and image radius. It is assumed that the laser beam has a Gaussian intensity distribution and is absorbed, following Beer's law, in both the pigment epithelium and the choroid layers of the eye. The final expression is mathematically accurate to 1% and is valid for image radii ranging from 20 to 500 mum and for exposure times from 30 ms to infinity. Consequently, this analysis is ideally suited to the interpretation of laser threshold damage experiments using shuttered gas lasers operated in their uniphase mode. Finally, the problem of defining a safe exposure level to laser radiation is considered. However, the lack of available information on minimum retinal image diameter and maximum absorption coefficient permits only an estimate of this parameter to be made.