The Effect of Occlusive Patching on Visually-Directed Tasks

Purpose: Occlusive patching is used to treat a variety of ocular conditions. A paucity of literature exists regarding the effects of occlusion on functional tasks and driving performance. We investigated the immediate effects of occlusive patching on a variety of visually dependent tasks as well as driving performance on a simulator. Methods: Thirty normally sighted subjects were examined in a prospective randomized manner. All subjects underwent a complete medical history and eye examination. All subjects performed a variety of near tasks and drove a driving simulator with and without patching. The tasks included traditional clinical depth tests, tests of visual memory, scanning, and tracking, and gross and fine-motor abilities. All subjects filled out a questionnaire relating to their perception of the effects of patching on functional tasks and driving ability. Results: Visual memory, scanning, tracking, and perceptual constancy were unaffected by patching. However, there were significant differences between the patched and unpatched conditions for four of five of the three-dimensional visual coordination tasks. Eight of 19 (42%) of the fine-motor tasks and 4 of 9 gross-motor tasks (44%) showed significant differences between the patched and unpatched conditions. A greater frequency of out of lane events and more abrupt braking profiles were seen when subjects drove monocularly rather than binocularly. Conclusions: Sudden occlusion immediately changes perceptual ability by decreasing visual field and eliminating stereoacuity. This has important implications for the performance of everyday tasks.