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J. V. Odom, M. Leys; Speed Discrimination: Effects of Age and Age-Related Macular Degeneration. Invest. Ophthalmol. Vis. Sci. 2008;49(13):1512.
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To determine the thresholds for speed discrimination in three groups of subjects, young normals, older normals, and patients with central visual field loss due to age-related macular degeneration (AMD).
Three groups of observers made speed discrimination judgments. The groups were younger normals aged 21-50 years, older normals aged =>60 years and low vision patients with AMD aged =>60 years. Observers were seated 50 cm from a display that subtended 44.6 arc deg in the horizontal dimension. Pressing a mouse began a trial. During the 833 mS trial, a pattern of 100 white dots on a black background appeared. The observer saw four regions on the screen. Alternating regions of the screen moved in opposite directions, 25 dots in each region, at random locations and moved either left to right or right to left. Dots had a lifetime of 467 mS or were replaced as they moved off of the screen. The observer’s task was to determine the direction of motion which had faster moving dots.
AMD patients discriminate speed differences less well than younger normals (p<0.01) and tended to discriminate speed differences less well than older normals as well, although the difference was not statistically significant. There was also a trend for the older normals to discriminate speed differences less well than younger normals.
The results are consistent with Brown et al. (1986) who reported that discrimination of speed differences was related to mobility performance in low vision patients. The untested implication from our results is that AMD patients would have impaired mobility performance.
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