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L. A. Hagen, R. C. Baraas; Visual Acuity and Contrast Sensitivity in Deuteranomalous Trichromats. Invest. Ophthalmol. Vis. Sci. 2009;50(13):2736.
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It has been suggested that there is a trade-off between spatial and chromatic vision related to the distance between peak sensitivities of L and M cones in human trichromatic observers (Barlow, 1982 Vision Res. 22: 635-643). The aim of this study was to test whether deuteranomalous trichromats, who have a narrower distance between peak sensitivities of L and M cones, have better spatial vision than normal trichromats.
Five deuteranomalous trichromatic males and seven normal trichromatic females were tested with a battery of color-vision tests, including the Rayleigh match (Oculus anomaloscope). Spatial resolution was measured with the Freiburger Visual Acuity Test and spatial contrast sensitivity with horizontally oriented Gabor patches (full-width-at-half-height of 3.76 deg). Contrast sensitivity was measured at 1.2, 2.8, 4.0, 5.6, 11.2 and 31.0 c deg-1. Observers were corrected to best logMAR letter acuity and viewed the stimuli monocularly with a 2.8 mm artificial pupil at 6 m.
Rayleigh match midpoints were significantly different for normal trichromats (39.5±0.5) and deuteranomals (16.8±2.0), and were employed as an estimate of the effective distance between peak sensitivities of L and M cones. Deuteranomals had poorer contrast sensitivity at low spatial frequencies, with a significant difference at 1.2 c deg-1. Their Freiburger Visual Acuity and contrast sensitivity at high spatial frequencies were not significantly different from that of normal trichromats. There was, however, a positive and significant correlation between contrast sensitivity at high spatial frequencies (11.2 and 31.0 c deg-1) and the Rayleigh match midpoint for individual deuteranomals; that is, observers with match midpoints closer to normal had higher sensitivity at high spatial frequencies.
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