Impact of eye movements on thermal injury thresholds

During an exposure to a continuous-wave (CW) laser, intrinsic eye motion will cause the beam spot to move about an extended region of the retina. Because of this, the thermal damage threshold for small spot sizes will be larger than predicted if eye movements are neglected. Experimentally recorded eye movement data are input into a numerical simulation to calculate the increase in temperature occurring in the retina during an exposure to a CW laser. An Arrhenius damage integral is used to estimate the thermal damage threshold, which is then compared to the threshold estimated for a stationary eye. A Relief Factor, defined as the ratio of the damage threshold in the presence of eye movements to the threshold ignoring eye motion, is used to measure the impact of eye movements. The relief factor is found to be 1.18 for 2 second exposures, increasing to 1.38 for 50 second exposures.