Colorblind Individuals have expanded color vision

by Medindia Content Team on  December 7, 2005 at 8:22 PM General Health News   - G J E 4
Colorblind Individuals have expanded color vision
Deuteranamolous patients suffer from color blindness due to X-chromosome variations, which make them unable to differentiate between colors but have an increased sensitivity to differentiate two color dimensions, which are unable to be differentiated by normal persons. The results of these studies carried out by Professor John Mollon and colleagues, University of Cambridge had been published in the Journal Current Biology.

Colors are differentiated by the eyes by cone photoreceptors, which are activated by different wavelengths and in X-chromosome linked variants they have an color blindness to differentiate different colors and these sensitivities are altered in deuteranomalous colorblind individuals because they possess a variant form of one of the cone photoreceptors--the sensitivity of cones that should be "middle-wave" is shifted toward that of "long-wave" cones, resulting in decreased ability to differentiate between some colors that are easily distinguishable by those with normal color vision. In theory, however, it is possible that owing to the altered sensitivities of their cone photoreceptors, deuteranomalous individuals may be sensitive to color differences that are not apparent to those with normal color vision.

The researchers conducted the experiment in deuteranamolous and "color-normal" individuals to report whether they were able to distinguish between pairs of colors that were theoretically predicted to look different to deuteranamolous colorblind individuals but to appear the same to those with normal color vision. Indeed, the researchers found that some color pairs were only seen to be different by deuteranamolous individuals. The finding suggests that although these individuals may be blind to some colors accessible by color-normal individuals, they also have a sensitivity to a "color dimension" that is inaccessible to those with normal color vision.

The researchers point out that because deuteranamolous colorblindness is caused by an X-chromosome-linked genetic alteration, and because women randomly inactivate one of their two X chromosomes in each of their cells, women who are carriers of the deuteranamoly trait (and hence have one normal X chromosome) are predicted to express four types of cone photoreceptor--the three normal cone types, as well as the cone with a shifted wavelength sensitivity. Thought it is unclear whether this would appreciably affect color vision in a way that allows expanded color sensitivities without the colorblindness experienced by deuteranamolous individuals, a test similar to that utilized in the present study could potentially be used to test this possibility.

Source: Eurekalert

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