29 Sep 2015

Could Your Child be Colorblind?

Category: Health,LearningAdmin @ 6:06 pm

Color blindness can be problematic. One test for it is the Farnsworth-Munsell 100 Hue Test. The online version is less accurate than the eye doctor would have, since monitors and room light variations may affect the outcome. Nevertheless, it’s worth trying because it is free and a high score indicates that further testing is warranted.

Let me relate a true story about a boy whom I’ll call Justin. Justin was completely confused about his math assignment, which depended upon reading graphs. His red-green color blindness made the red lines indistinguishable from the gray ones, so he had no way to answer the questions. His mother, who herself has red-green color blindness (which is unusual in women), perceived the red lines as different enough to pick them out. Fortunately it did not take her long to realize her son’s problem. She asked the school to modify the graphs with different colors so that he could read them.

By the way, you might think that people with red-green color blindness could not read traffic lights, but often this not the case. Both my cousin and my brother, who have red-green color blindness, can tell the difference between the lights well enough to drive. In fact, my cousin, whose color blindness is quite severe and involves more than just the red-green variety, can nevertheless distinguish colored lights well enough to be a pilot. My brother tells me that picking out ripe tomatoes is more of a problem, so he leaves that task to his wife.

The gene for red-green colorblindness is on the X chromosome and it is recessive (meaning it will not be expressed if a normal gene is present). The implications are different for men and women. Men only get one copy of the gene, always from their mother (since the father donates the y chromosome to boys). Their mother may not be colorblind, as she has two X chromosomes and one may be normal. However, if her biological son is red-green colorblind, you can be sure that she carries at least one gene for it (barring a less-common gene alteration by a gamma ray or another disruptor of DNA).

Females, on the other hand, must have two copies of the recessive gene in order to have this form of color blindness. Unless the father is colorblind, none of the daughters will display color blindness, since they will get at least one “good” gene from the father.

I took the Farnsworth-Munsell 100 Hue Test and got a score of 40, which is within what is considered normal. It was fun to find that the test agreed with my previous experience, which suggests that I have a very minor difficulty with some shades of blue. I haven’t looked into the genetic basis for that, but when I was choosing colors for one of my websites, I did some reading on blue-yellow color blindness and some other color issues so that I could choose colors and shades that would show intended contrasts for everyone. Book publishers and Web designers would do well to look into this area.

You can find more information about color blindness at some websites devoted to this issue, including the National Association for the Advancement of Color-Blind People and Colour Blind Awareness.

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