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Relationship between visual span and reading performance in age-related macular degeneration
Allen M Y Cheong1, Gordon E Legge, Mary G Lawrence
1Minnesota Laboratory for Low Vision Research, University of Minnesota, Department of Psychology, 75 East River Road, N218 Elliott Hall, Minneapolis, MN 55455, USA. cheon015@umn.edu
Vision Research
|January 15, 2008
Summary
Information transfer rate, combining visual span and temporal processing, better predicts reading speed in age-related macular degeneration (AMD) than visual span size alone. This finding is crucial for understanding AMD
Area of Science:
- Ophthalmology
- Visual Neuroscience
- Human Factors
Background:
- Age-related macular degeneration (AMD) impairs reading speed.
- Reduced visual span size was previously proposed as a limiting factor.
- Temporal processing (letter recognition exposure time) also impacts reading speed in AMD.
Purpose of the Study:
- To measure visual-span profiles in AMD patients and controls.
- To assess the relationship between spatial/temporal visual span properties and reading speed.
- To determine if temporal processing or visual span size better predicts reading speed in AMD.
Main Methods:
- Visual-span profiles were measured using a trigram letter-recognition method.
- Exposure time was set to the individual's temporal threshold for 80% letter recognition accuracy.
- Visual span size (bits) and information transfer rate (bits/sec) were calculated.
Main Results:
- AMD subjects had significantly smaller visual spans than controls in central and peripheral vision.
- Information transfer rates were significantly slower in AMD subjects.
- Information transfer rates correlated more strongly with reading speed (explaining 36% of variance) than visual span size.
Conclusions:
- Both visual span size and information transfer rate are impaired in AMD.
- Information transfer rate, reflecting combined spatial and temporal deficits, is a superior predictor of reading speed in AMD.
- Understanding these factors can inform interventions for reading difficulties in AMD.
