Quantifying the impact of thermal lensing on visual function in ocular media

Abstract

Several studies have been conducted in the past which determined that some near-infrared (NIR) sources are capable of inducing a thermal lens within ocular media of rhesus and, potentially, human subjects. Typically, the role of thermal lensing in the eye was explored in terms of its influence on damage thresholds for these NIR lasers entering the eye. However, the effect of a thermal lens on visible wavefronts entering the eye has yet to be explored. In recent years military and law enforcement agencies in the United States and elsewhere have devoted considerable resources to the area of "non-lethal weapons." Devices such as tasers, spike strips and ocular interruption (OI) devices provide the user with an escalation of force while minimizing casualties and collateral damage. One particular form of OI device, the laser dazzler, employs a visible laser capable of saturating retinal receptors causing a temporary flash blindness effect. While these visible devices have proven safe and effective in the field, an inherent risk exists when any light source is used to saturate retinal tissue. By adding the use of a thermal lens, these OI devices would create significant distortions in the visible wavefront to alter vision and/or increase the diameter of a focused visible dazzler at the retina to both improve safety and effectiveness of the visible device. This dissertation describes experiments involving artificial eye, human subject, and computational modeling which were conducted to quantify the impact of thermal lensing on visual acuity.