People who lose their central vision often found it difficult to perform visual tasks using their residual peripheral vision. The leading cause of central vision loss is age-related macular degeneration (AMD), which is also the leading cause of visual impairment and blindness for people over 60 years of age. Following the onset of the central vision loss, most patients develop an eccentric retinal location outside the affected macular area, the preferred retinal locus (PRL), as their new reference for visual tasks. The long-term goals of this project are to understand the mechanism(s) underlying the development of the PRL, and to understand the limiting factors and potentialities of the PRL(s) for various visual tasks so that effective visual rehabilitative strategies may be developed for patients with AMD and other macular disorders.
The first aim of the proposed research project is to evaluate the hypothesis that the selection of the location for a PRL is based on optimizing visual performance. We will measure performance for a set of visual tasks in observers with central vision loss and observers with normal vision to construct "performance maps" for our tasks. We will use these performance maps to predict the location for a PRL, specific to a given scotoma, which offers the best performance for our tasks.
The second aim of the proposed research project is to test the hypothesis that slow peripheral reading is due to an inability of the periphery to take advantage of text cues such as redundancy and parafoveal preview of words. A series of experiments, to be tested in observers with normal vision and observers with central vision loss, will evaluate the benefit on reading offered by different text cues in isolation and in various combinations.
The third aim of the proposed research project is to test the hypothesis that visual performance for people with central vision loss can benefit from perceptual learning. We will compare the effectiveness of a few selected training tasks to determine the one that is most effective in improving functional vision of people with central vision loss. We will also compare performance for other untrained tasks before and after training to determine how generalizable the learning effect is. Last but not the least;we will evaluate the longevity of the learning effect following training. The findings from each of these aims have the potential of developing into a useful rehabilitative tool that can either help us identify the best location for a PRL for patients with recent onset central vision loss, or to improve the functional vision or reading performance in patients with central vision loss.

Public Health Relevance

Following the loss of vision in the macular area, most people with macular disorders such as age-related macular degeneration adopt a retinal region outside the macular area as their "new fovea". The long-term goals of this project are to understand how the "new fovea" develops, and to understand the limiting factors and the potential for improving vision for people with macular disorders.

National Institute of Health (NIH)
National Eye Institute (NEI)
Research Project (R01)
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Special Emphasis Panel (ZRG1-ETTN-E (92))
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Wiggs, Cheri
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University of California Berkeley
Schools of Optometry/Ophthalmol
United States
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Kumar, Girish; Chung, Susana T L (2014) Characteristics of fixational eye movements in people with macular disease. Invest Ophthalmol Vis Sci 55:5125-33
Chung, Susana T L (2014) Size or spacing: which limits letter recognition in people with age-related macular degeneration? Vision Res 101:167-76
Bernard, Jean-Baptiste; Kumar, Girish; Junge, Jasmine et al. (2013) The effect of letter-stroke boldness on reading speed in central and peripheral vision. Vision Res 84:33-42
Chung, Susana T L (2013) Cortical reorganization after long-term adaptation to retinal lesions in humans. J Neurosci 33:18080-6
Chung, Susana T L (2013) The Glenn A. Fry Award Lecture 2012: Plasticity of the visual system following central vision loss. Optom Vis Sci 90:520-9
Coates, Daniel R; Chin, Jeremy M; Chung, Susana T L (2013) Factors affecting crowded acuity: eccentricity and contrast. Optom Vis Sci 90:628-38
Chung, Susana T L; Truong, Sandy R (2013) Learning to identify crowded letters: does the learning depend on the frequency of training? Vision Res 77:41-50
Yu, Deyue; Akau, Melanie M U; Chung, Susana T L (2012) The mechanism of word crowding. Vision Res 52:61-9
Chung, Susana T L (2011) Improving reading speed for people with central vision loss through perceptual learning. Invest Ophthalmol Vis Sci 52:1164-70
Chung, Susana T L; LaFrance, Martin W; Bedell, Harold E (2011) Influence of motion smear on visual acuity in simulated infantile nystagmus. Optom Vis Sci 88:200-7

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