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J. V. Odom, P. Ghude, M. J. J. Leys; Effects of Age and Age-Related Macular Degeneration on Coherence Thresholds in Rotational Optic Flow Patterns (Curl). Invest. Ophthalmol. Vis. Sci. 2007;48(13):5506.
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© ARVO (1962-2015); The Authors (2016-present)
To determine the coherence thresholds for direction of rotation judgments (curl) 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 subjects were tested; younger normals aged 21-50 years, older normals aged 60 years or more and low vision patients with AMD aged 60 years or more. Observers were seated 50 cm from a display that subtended 44.6 arc deg in the horizontal dimension. The observer saw a red line at the center of the screen. Pressing a mouse button began a of 833 mS trial during which the stimulus was an optic flow pattern of 100 white dots on a black background. Dots had a lifetime of 467 mS or were replaced if they moved off of the screen. Dot velocity was 1.261 deg/S. At the end of the trial the central red line reappeared. The observers’ indicated the direction of rotation, clockwise or counterclockwise, of the dots by pressing either the left or right mouse button. On the first trial all 100 dots moved in the same direction, clockwise or counterclockwise. Correct judgments resulted in a reduction in the number of dots moving in the same direction (coherently) and an increase in the number of dots which moved in other randomly selected directions. A staircase procedure using a two-down, one-up rule was employed to determine the threshold number of coherently moving dots which were required for subjects to accurately determine the direction of rotation of the coherently moving dots.
Young normals had an average coherence threshold of 9.5%, while the average threshold for older normals was 17.15%, and for AMD patients was 33.75% (p = 0.0047).
Age affects directional judgments of curl. AMD has an additional major impact on judgments of curl direction. Detection and discrimination of curl is thought to be important in the control of balance. Impaired curl perception may be related to poorer balance and increased falls in the elderly and patients with AMD.
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