The overall goal of this study is to identify the sources of form-vision deficits in peripheral vision. Macula is the high-resolution patch in a human retina, which provides clear and sharp """"""""central"""""""" vision. Patients with various forms of macular disorders, such as aged-related macular degeneration, must see objects eccentrically and rely on their low-resolution peripheral visual fields to recognize objects, identify faces and read. Compared to the fovea, the periphery is far less capable of this type of form vision, even when its poor spatial resolution is compensated for by magnification and contrast enhancement. For example, reading in the periphery is laboriously slow, and objects can become unidentifiable in a cluttered scene. At present, we do not have a good understanding of how form vision in the periphery is achieved by the visual system, why peripheral form vision is qualitatively different from central vision, and what are the causes of the form-vision deficits in the periphery. Such lack of understanding hinders our ability in deriving effective rehabilitation regimens and adaptive technologies for patients with central vision loss. Our focus is to investigate form vision in the periphery with ecologically important stimuli (faces, objects, and letters). We hypothesize that form vision deficits in the periphery are largely due to a lack of mechanisms for properly selecting and assembling simple features into complex ones at an early stage of visual processing. We further hypothesize that practice improves peripheral form vision mostly by improving the visual system's ability to make better inference about the misassembled inputs at the later stages. Our investigation is divided into three interrelated parts. Parts 1 will use psychophysical and computational methods to identify the functional causes of form vision deficits in the periphery. Part 2 will use fMRI to locate the brain regions that are associated with these deficits in order to provide converging evidence for the findings from Parts 1. Part 3 will determine the functional and neural mechanisms that underlie form-vision learning in the periphery. We will conduct experiments on normally sighted young adults, patients with central vision loss, and older adults (aged-matched controls for the patients).
The most common cause of visual impairment in the older population is age-related macular degeneration (AMD), which accounts for about 50% of all cases of registered blindness in industrialized countries (Koh &Ang, 2002). Patients with AMD and other macular disorders must view objects eccentrically and rely on their peripheral visual fields to recognize objects, identify faces and read. These form-vision tasks are often laborious if not impossible. The overall goal of this study is to identify the sources of form-vision deficits in peripheral vision, which we believe will enable the development of effective rehabilitation regimens and adaptive technologies.
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