Age-related macular degeneration (AMD) affects about 13.5% of the U.S population over the age of 60 and impacts the central part of the visual field, which provides high-acuity visual function and serves as the reference point for eye movements. The type of functional loss depends on the extent to which the scotomata in the two eyes overlap. When the scotomata locations in the two eyes overlap and include the fovea, the resultant binocular central field loss (CFL) can significantly impact daily life, particularly tasks that require high-acuity vision, such as reading. Binocular CFL also causes individuals to adopt an eccentric preferred retinal locus (PRL) for fixation, which takes several years to become the reference for eye movements and complicates simple goal-directed behavior such as finding items of interest. We will investigate the challenges of using the PRL for visuomotor behavior and investigate whether coordinated eye and hand movements can facilitate the transition to the PRL as an oculomotor reference (Aim 1). We will also address challenges that are independent of the overlap of the scotomata in the two eyes. Specifically, individuals can experience loss of stereopsis in the parts of the visual field that correspond to a scotoma in either eye, regardless of whether their scotoma is binocular or monocular, leading to difficulty with eye-hand coordination tasks in near space and with navigating stairs and drop-offs. To address these challenges, we will investigate the potential for the periphery to mediate stereopsis (Aim 2). We will also examine the potential of monocular cues such as motion parallax to mediate depth perception, particularly for those individuals who have spared central fields in one eye (Aim 3). In sum, our research plan seeks to understand the impact of binocular scotomata and more extensive stereo-blind zones on eye movements, hand-eye coordination, and mobility in macular degeneration, under binocular, real world viewing conditions.
The ability to move the eyes to find objects, and the ability to use information about depth is critical to the safe execution of everyday tasks that require eye-hand coordination and navigating through the environment safely. Comprehensive rehabilitation of individuals with central field loss could have dramatic results in helping them achieve 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.