Age-related macular degeneration affects the central part of the visual field, which provides high acuity visual function and serves as the reference point for eye movements. Thus difficulties with reading and with eye movements are common complaints. Extensive research effort has been invested in understanding the causes of reading difficulties in individuals with vision loss, leading to the development of optical devices and assistive technology to alleviate the problem. However, much less attention has been paid to the obstacles central field loss poses to tasks of daily living. Individuals complain about difficulty shopping for groceries, finding items at home, following moving targets, performing eye-hand coordination tasks and navigating. Our goal is to develop research methods to help patients with central vision loss learn to use their remaining vision effectively. We believe that three factors underlie the difficulties that individuals with AMD confront while performing everyday tasks. Firstly, most are unaware of the location of the region of vision loss (scotoma) and are therefore unaware of objects obscured by the scotoma. To address this issue Aim 1 will investigate methods that teach scotoma awareness and direct eye movements towards the scotoma to locate static objects that would otherwise go undetected. Secondly, while individuals adopt a peripheral retinal locus when the fovea is affected, the shift of the eye-movement reference to this new locus takes much longer. Thus they have difficulty directing their gaze to objects of interest and tracking moving objects, particularly those moving toward them, in depth.
Aim 2 will use training tasks that help patients direct their PRLs to acquire and track targets whose position and direction of motion are unpredictable, and to become aware that their scotoma extends in depth, so that they can keep track of oncoming objects such as cars and bicyclists. Finally, 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. To address this issue, Aim 3 will evaluate the potential for coarse stereopsis in the peripheral part of the visual field to improve eye hand coordination in near space.
HEALTH RELEVANCE The ability to move the eyes to find and track objects, and the ability to use coarse information about depth is critical to the safe execution of everyday tasks that require eye-hand coordination and navigating through the environment while keeping track of moving objects. Comprehensive rehabilitation of individuals with central field loss could have dramatic results in helping them to a full independent lifestyle. Our findings will lay the groundwork for therapies that maximize residual visual function and help create an important intervention for the successful rehabilitation of individuals with AMD.