There are more than 3.3 million Americans with low vision, most of whom have reading difficulties. Many suffer from macular degeneration and associated loss of central vision. The primary purpose of this proposal is to develop principled training methods to enhance low-vision reading, particularly for those with macular degeneration Our research indicates that decrease in the size of the visual span is a key factor explaining reduced reading speed in low vision. The visual span for reading refers to the number of letters, arranged side-by-side as in text that can be recognized accurately without moving the eyes. Structure of the retina and cortical magnification of the central visual field produce a small visual span, even for normal vision. This small visual span is further diminished as a consequence of eye disease. In a series of psychophysical studies, we will build on our prior research on the visual span to develop principled training methods to enhance low-vision reading. The three forms of training to be evaluated include: 1) Vertical reading in cases where the vertical visual span exceeds the horizontal visual span;2) Oculomotor training of eye fixations to maximize the information transfer rate through the visual span;and 3) Perceptual Learning which is focused on enlarging the size of the visual span. The applications to reading rehabilitation will benefit from our exploration of the sensory factors determining the size of the visual span and its role in reading. We will examine spatial factors (crowding, positional uncertainty) and temporal factors determining the size of the visual span in central and peripheral vision. We will use fMRI to localize the neural site of word and letter recognition within the visual span and the influence of perceptual learning on its size. These studies will inform our psychophysical exploration of the visual- processing capacity of the preferred retinal locus (PRL), the region of peripheral retina used for reading by many people with macular degeneration.
There are more than 3.3 million Americans with low vision, most of whom have reading difficulties. Our broad goal is to use findings from vision science to understand the reading difficulties of people with low vision. A major goal of the current proposal is to develop principled training methods to enhance low-vision reading, particularly for people with macular degeneration.
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