Age-related macular degeneration affects central vision and impairs high acuity visual function. Individuals with AMD complain about difficulty with everyday tasks such as reading, recognizing faces and watching television. More recent studies report difficulty with eye-hand coordination and grasping, consistent with data showing that the majority of individuals with AMD have little depth perception. Stereopsis can be impaired when the two eyes have very disparate patterns of vision loss, particularly when the stronger eye determines binocular gaze direction, without regard to the functional status of the corresponding fixation location in the other eye. Loss of depth perception not only impacts tasks requiring eye hand coordination, but it can have serious consequences for mobility and obstacle avoidance. In this proposal we examine the potential to restore stereopsis in individuals with AMD, by encouraging individuals to use fixation loci in the two eyes that have similar function. We start by examining the potential for depth perception in Aim 1. This requires mapping the regions of residual function in the two eyes to determine if there are corresponding points in the periphery that can subserve depth perception.
In Aim 2 we determine whether observers are able to combine information from the two eyes (a necessary prerequisite for stereopsis) and whether they have any degree of depth perception.
In Aim 3 we test the hypothesis that individuals with AMD are able to use different fixation loci for different tasks. We take two approaches to encourage observers to use retinal loci that are functionally equivalent and in corresponding locations in the two eyes, so they can provide a substrate for depth perception. We first artificially equate the pattern of vision loss in the two eyes and allo observers to practice coordinated eye movements. We then determine whether they use these corresponding fixation locations in an eye-hand coordination task that benefits from depth information. If indeed the choice of fixation location is task- dependent, we expect that practice with these two tasks will improve binocular correspondence and potentially lead to a recovery of stereopsis.
Depth information is critical to the safe execution of everyday tasks that require eye-hand coordination and orientation and mobility. Comprehensive rehabilitation of individuals with central field loss could have dramatic results in helping them t a full independent lifestyle. Our findings will lay the groundwork for therapies that promote binocular function and depth perception and help create an important intervention for the successful rehabilitation of individuals with AMD. )