What is color blindness? January 21, 2009
Posted by Ruth in : Color Blind , add a comment
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Color blindness, or color vision deficiency is the inability to perceive differences between some of the colors that other people can distinguish. We have “photoreceptor cells” in the back of our eyes called “rods” and “cones.” The rod cells are more active in low light and account for night vision and distinctions of grey. The cone cells are more next day active in light and account for our more fine vision and color perception (a combination of blue, green and red receptors).
When your cones don’t work properly, or you don’t have the right combination blue, green and red receptors, your brain doesn’t get the right message about which colors you’re seeing. For example, for someone who’s color-blind, he/she might have trouble distinguishing the colors of a traffic light, or a green leaf might look tan or grey.
There are about 120 million rods in one retina of a human eye, about 20 times the number of cones.
Color blindness is almost always inherited.
Here is a simple test to test for color blindness -