Abstract
Objectives: In performing search tasks, the visual system encodes information across the visual field and deploys a saccade to place a visually interesting target upon the fovea. The process of saccadic eye movements, punctuated by periods of fixation, continues until the desired target has been located. Loss of peripheral vision restricts the available visual information with which to plan saccades, while loss of central vision restricts the ability to resolve the high spatial information of a target. We investigate visuomotor adaptations to visual field loss with gaze-contingent peripheral and central scotomas. Methods: Spatial distortions (peak frequency 2 cpd) were placed at random locations in 25deg square natural scenes, with transitions from distorted to undistorted regions smoothed by a Gaussian (sd = 2 deg). Gaze-contingent central or peripheral simulated Gaussian scotomas (sd =1 2 or 4 deg) were updated at the screen rate (75Hz) based on a 250Hz eyetracker. The observer's task was to search the natural scene for the spatial distortion and to indicate its location using a mouse-controlled cursor. Results: As the size of central or peripheral scotomas increased, so followed an increase in mean search times and the mean number of saccades and fixations. Fixation duration, saccade size and saccade duration were relatively unchanged across conditions. Conclusions: Both central and peripheral visual field loss cause functional impairment in visual search. The deficit is largely attributed to an increase in the number of saccades and fixations, with little change in visuomotor dynamics. Subjects frequently made saccades into blind areas and did not modify fixation durations to compensate for reduced acuity or change in temporal integration, suggesting that adaptations to visual impairment are not automatic and may benefit from rehabilitation training.