Age-related macular degeneration (ARMD) is the leading cause of visual impairment in persons 65 years of age and older. ARMD often leads to scotomas (blindspots) affecting the fovea, which result in central field loss (CFL). CFL is devastating to vision, in part because it forces the use of peripheral retina to do tasks (e.g. reading) formerly done with the fovea. Patients with CFL often have reduced acuity and read more slowly than do normally-sighted observers using peripheral retina. The goals of this research are to understand when and why this is so. Our underlying assumption is that CFL changes the ability of peripheral retina to process visual information. We will measure acuity and reading speed in patients with central field loss due to ARMD and in normally-sighted subjects with simulated scotomas. We will use simulated scotomas to determine the impact of a scotoma on acuity with central field loss, and simulated scotomas and image stabilization to assess the impact of retinal location and eye movement control on acuity and reading speed. We will also investigate the relationship between letter acuity, word acuity, and reading eye movements. Performance on each of these tasks with simulated scotomas will be compared to the performance of patients with CFL under the same test conditions. The data generated by these studies will help us to better understand the limitations on visual processing in peripheral retina, as well as under what conditions patients with CFL due to disease have reduced visual function relative to normal peripheral retina. This new knowledge will provide vision rehabilitation specialists with realistic guidelines from which to gauge success, as well as provide them with new information for developing rehabilitation protocols and technologies. For example, should we find that there is an optimal retinal meridian for reading and that reading is faster when the words are stabilized on the reader's retina, this could lead to the design of computer-based low vision reading aids, combined with eye tracking devices, that would provide such a display. The research proposed here will also expand our understanding of the plasticity of the adult visual system. Evidence suggests that fast cortical changes occur in response to retinal scotomas. We will, for the first time, investigate the functional changes associated with retinal scotomas, both with short-term adaptation (simulated scotomas) and long-term adaptation (ARMD).
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