Color discrimination in carriers of color deficiency

Abstract

Carriers of X-linked color vision deficiencies have previously been reported to exhibit mild abnormalities of color matching and discrimination. In a sample of 55 carriers of protan and deutan deficiencies and 55 age-matched normal controls, we measured chromatic discrimination along a red-green axis. We found that discrimination was impaired in the case of carriers of deutan deficiencies (which affect the middle-wave-sensitive cones of the retina), but was normal in the case of carriers of protan deficiencies (which affect the long-wave-sensitive cones). We argue that this result can be explained by the difference in the relative numbers of middle- and long-wave cones in heterozygous retinae: the imbalance of the two cone types is predicted to be much greater in the case of the deutan heterozygote than in the case of the protan heterozygote. In future studies it will be necessary to consider separately the two types of heterozygote.

Sex-related differences in chromatic sensitivity

“…However, this general assumption is not supported by findings from Hood et al's (2006) study that showed some heterozygote females (i.e., carriers for deutan defects), but not others (i.e., carriers for protan defects) have poorer RG colour discrimination when compared with homozygotes. We, therefore, applied two different analyses: one which controlled for the possible influence of carriers of deutan defects and a second which controlled for the possible influence of carriers of either defect.…”

“…Why should this be the case? Hood et al (2006) have offered one explanation for why deutan carriers may have slightly impaired red-green colour discrimination compared with males. They speculate these differences can be explained by differences in the relative numbers of L-and M-cones in heterozygous retinae.…”

Does gender and experience influence shade matching quality?

“…[4][5][6][7][8][9][10] As far as color normal persons of both genders are concerned, vision science literature stated that differences between color normal men and women in red-green color discrimination were not significant if color deficient males and females and heterozygote female carriers (15%) were excluded from comparisons. 11 When color assessment and diagnosis test was performed on 150 color normal males and the same number of color normal females, no significant gender-related difference was recorded. 12 Several dentistry-related studies offered evidence on nonsignificance of differences in shade matching results between color normal females and males.…”

Performance of normal females and carriers of color-vision deficiencies on standard color-vision tests

“…Some carriers may also exhibit a shift in Nagel match midpoint (MMP) and an enlarged Nagel matching range (MR) when tested by Rayleigh anomaloscopy [2,[6][7][8][9]. Protan carriers are less sensitive to red light, a characteristic known as Schmidt's sign [6,[10][11][12]. Deutan carriers, on the other hand, are more sensitive to red light [12][13][14][15].…”