Laser-induced retinal injury threshold studies with wavefront correction

Computer models of laser retinal exposure predict that the retinal injury threshold will decrease with decreasing retinal irradiance area until the beam diameter at the retina is less than 10 μm. However, a number of investigations over a range of wavelengths and exposure durations show that the incident energy required to produce a retinal injury in the eye of an anesthetized non-human primate (NHP) does not decrease for retinal irradiance diameters smaller than ∼100 μm, but reaches a minimum at that diameter and remains nearly constant for smaller diameters. A possible explanation is that uncompensated aberrations of the eye of the anesthetized NHP are larger than predicted. Focus is a dynamic process which is purposely defeated while performing measurements of retinal injury thresholds. Optical wavefront correction systems have become available which have the capability to compensate for ocular aberrations. We report on an injury threshold experiment which incorporates an adaptive optics system to compensate for the aberrations of an NHP eye during exposure to a collimated laser beam, therefore producing a near diffraction limited beam spot on the retina.