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 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 locus for visual tasks. To date, little is known about the properties of the PRL. 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 test the hypothesis that there is a shift in the reference coordinate from the fovea to the PRL for people with central vision loss. We will measure the retinal locus for several oculomotor and perceptual tasks to determine if the retinal locus for each task is shifted to an eccentric location outside the scotoma. We will also compare if the same retinal locus is used for various oculomotor tasks and/or perceptual tasks.
The second aim of the proposed research project is to test the hypothesis that the location for a PRL is based on the location with the most optimal retinal structures and/or basic perceptual properties. We will obtain structural information of the retina using an OCT, and functional data will be collected for two tasks, all at multiple retinal locations around the scotoma of each observer with central vision loss. We will determine if the structural and/or functional data can predict the location of the PRL. The data will also tell us if there is a structure-function relationship of th retina around a scotoma.
The third aim of the proposed research project is to test the hypothesis that for people with central vision loss, the benefits due to training can be enhanced by improving temporal processing and/or by improving fixation stability. We will develop a temporal training task and an oculomotor training task (fixational saccade adaptation), and to compare if these are more effective than the conventional spatial training task in improving functional vision for people with central vision loss. The findings from each of these aims have the potential of developing into a useful rehabilitative tool that can either help us identify the est 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 (AMD) adopt a retinal region outside the macular area as their surrogate fovea. The long-term goals of this project are to understand how the surrogate fovea develops, its properties, and to understand the limiting factors and the potential for improving vision for people with macular disorders. Successful accomplishment of our goals may lead to development of more effective rehabilitation strategies 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-H (02))
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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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