Abstract
Abstract: :
Purpose: Patients with age–related maculopathy (ARM) are often trained to use eccentric viewing (EV) to compensate for visual disturbances in their central vision. To assess the effects of EV training on the gaze behavior of ARM subjects performing activities of daily living, a good calibration, characterized in part by minimal eye–in–head movements while fixating on calibration targets, needs to be obtained in order to accurately place the eye–on–scene. The purpose of this study is to measure the variability in eye–in–head movements of normally sighted and ARM subjects fixating on five calibration targets pre and post EV training. Methods: Twelve normally sighted and twenty–four ARM patients, who were participating in a blind rehabilitation program at the Hines VA Blind Center, had eye and scene data recorded while fixating on 5 calibration targets arranged in a "plus" formation. The eye and scene data were recorded using two miniature cameras attached to a portable eye–tracker. One camera recorded images of the subject’s eye while the other camera recorded images of the calibration scene. Eye and scene data of the ARM subjects were recorded for calibrations measured pre and post EV training. The variation (standard deviation) in eye–in–head movements in the horizontal and vertical planes corresponding to fixations on each of the calibration targets was calculated. Results: Both the ARM and normally sighted subjects showed no differences in the variability in eye–in–head movements between the horizontal and vertical planes (ie. the distributions of eye–in–head movements were circular). The ARM subjects however showed greater variability in eye–in–head movements in both the horizontal and vertical planes than the normally sighted subjects. Specifically, we found that pre EV training, the ARM subjects showed 3 times greater variability in eye–in–head movements than the normally sighted subjects in both the horizontal and vertical planes. Post EV training, the ARM subjects showed a two–fold increase in the variability in eye–in–head movements compared to the normally sighted subjects in both the horizontal and vertical planes. Conclusions: Compared to normally sighted subjects, subjects with ARM show difficulty maintaining steady, non–foveal fixation on static targets. The variability in eye movements by ARM subjects during calibration has implications on the accuracy of evaluating the gaze behavior of subjects with ARM pre and post EV training during activities of daily living.
Keywords: low vision • eye movements • vision and action