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Brett Jeffrey, Wadih Zein, Benedetto Falsini, Divya Nigam, Paul Sieving; Quantitative Measurement of Color Discrimination in Cone-Rod Dystrophies and Inherited Maculopathy. Invest. Ophthalmol. Vis. Sci. 2013;54(15):2793.
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To provide quantitative measurement of color discrimination in subjects with inherited retinal degenerations involving the central retina.
Nine subjects aged 12-65 years had a diagnosis of cone-rod dystrophy (n=4), Stargardt disease (n=3) or inherited maculopathy (n=2). Color discrimination thresholds were measured along 8 axes spaced 45° apart in CIE 1976 L*u*v* space using a low vision version of the Cambridge Color Test (LvCCT). Achromatic area (AA 10^6 u*v*2) was determined from the fit of an ellipse to threshold chromaticity coordinates. Total threshold length (TLL 10^3 u*v*) was the sum of all 8 thresholds. Results were correlated with full-field ERG, SD-OCT and fundus autofluorescence. To test for luminance cues thresholds were measured from 8 complete achromats. The effect of reduced visual acuity on color thresholds was examined using optical blur in 2 control subjects.
Color discrimination thresholds were obtained along all axes for 8 subjects with visual acuities ranging from 20/25 to 20/800 (median 20/250). One subject with advanced cone-rod dystrophy did not perceive color along any axis. Achromatic area and total threshold length were smaller (p<0.001) in subjects with foveal sparing (AA 551±321; TLL 97±34) compared with those with no sparing (4758 ± 1141; 272 ± 62). Achromatic area and total threshold length were not correlated with visual acuity, ERG amplitude, foveal thickness or area of geographic atrophy. In 7 subjects the rotation angle of the ellipse ranged from -12o to -55o, consistent with confusion along the deutan axis; one subject had a tritan defect. Achromats were at or near maximum achievable chromaticity along all axes. In controls, a reduction in visual acuity down to 20/800 produced no change in color thresholds.
In subjects with foveal sparing, the lack of correlation between color discrimination thresholds and visual acuity suggests that these two tests are limited by different retinal regions and/or mechanisms. The results from the achromats and two controls confirm that neither luminance cues nor a reduction in visual acuity contribute to color discrimination thresholds. The LvCCT uses a conceptually simple stimulus amenable to the low vision population and provides a means of quantifying color discrimination changes in subjects with progressive inherited retinal disease.  Simunovic MP et al Vis Res 1998 38:3413-19
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