Eye Controlled Simulation of Scotoma Effects on the Retina
Annual rept. (Final) 3 May 1986-2 Sep 1989
EYE RESEARCH INST OF RETINA FOUNDATION BOSTON MA
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Scotoma simulation is useful for evaluating visual loss or disruption eg from the aftereffects of accidental laser exposure or retinal disease because it allows testing the size, position and shape of scotomas in normal subjects under controlled conditions. Human eye movements, made during visual performance tasks, were used to move an obscurant or mask to display areas corresponding to the fovea. These real-time, eye controlled scotoma movements eliminated central vision and compelled the subjects to adapt by using peripheral vision and eccentric fixation. Adaptation to the simulated scotomas was evaluated by measuring changes in the eye fixation duration, saccade length and the eye position relative to instructed targets. Rapid development of eccentric eye positions, the principal means of compensating for the loss of central vision, showed that subjects are able to optimize the location of the scotoma with the higher receptor density. During and after adaptation, the presence of a simulated scotoma caused grossly distorted eye fixation patterns when compared to normal fixation control. Abnormal patterns were reduced as subjects became more experienced with the simulated visual losses, but, there were persistent drift movements, dispersion of eye fixations and error fixations with the scotoma especially under stress from accelerated pacing. Whether there is residual visual impairment after adaptation is dependent on the size of the scotoma, the length of the adaption period and the visual demands of the task.
- Anatomy and Physiology
- Medicine and Medical Research