Dei'ah veDibur - Information & Insight

A Window into the Chareidi World

10 Ellul 5761 - August 29, 2001 | Mordecai Plaut, director Published Weekly








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Home and Family
Color Blindness
by A. Ross

Who would ever think that even color blindness could be connected to judging people favorably? Something to think about...

Part I

There are many people who have never met a color blind person, and have never thought about the subject at all. Some of these people think that there is no such phenomenon, that it is just a figure of speech. I met a highly intelligent teacher once who slapped a boy (in the `olden days') for being cheeky. He had colored the leaves of a tree a bright red, and the teacher had asked jokingly, "Are you color blind?" To which the child had replied very positively that he was. When the teacher related this story to me, I remarked that he probably was, indeed, and this teacher was convinced that there was no such thing.

What is color blindness? The Encyclopedia Britannica writes: "The inability to distinguish one or more of the three colors: red, green and blue." Color blind people may be blind to one, two or all three of these colors.

Color blindness, perhaps color deficiency for those who regard the term as offensive, affects about 7 or 8% of the male population and 0.5% of females. That is about one in twelve males and one in two hundred females. A color blind man and a woman who sees colors normally, will have daughters with normal vision who are carriers of this gene. The daughters' sons, or at least some of them, will very likely be color blind. If a color blind man is married to a carrier, then their daughters might also be color blind. The sons of a color blind man and a woman with normal vision, have normal color vision themselves and cannot pass on this gene.

When light stimulates the retina which is a membrane lining inside the back of the eye, a person sees. Tle retina is made up of cones and rods. The cones which are located at the center of retina let us see color by day, but are not much use at night. This is why we cannot distinguish color at night. The rods give us night vision, but do not distinguish color.

Many people think that color blind people see only black and white, but this is not true. It is extremely rare for someone not to be aware of any colors. The cones contain a light sensitive pigment. Genes contain the coding instructions for these pigments. If the coding instructions are wrong, the cones will be sensitive to different wavelengths of light, which results in the color deficiency.

People with normal cones and light sensitive pigments are able to see all the different colors and shades by using cones sensitive to one of three wavelengths of light: red, green and blue, as mentioned before. There are many color deficient people who do not even know that they have a problem. They are poor at telling the difference in shades of red, orange, yellow and green.

There are others who are not just poor at differentiating between colors and shades. They are the severely color blind. They see no difference between red, orange, yellow and green. Lavender, violet, purple and blue all seem to be blue. Green, beige and brown are indistinguishable from each other. Red and black are often the same in different lights.

A Japanese man devised a series of plates in 1917 which are now the basis of all tests for color blindness. There are a series of circles, which are filled with a background of grey dots, with varying digit patterns in different color dots imposed on the background. Underneath each pattern he writes which digit a normal sighted person can see, and which digit people with varying degrees of color blindness can see. For example, he may write "People with normal vision will see a 2, some others (there are different names for the different kinds and degrees of color blindness) will see a 7 and some will see no number at all." Several people who had access to this book have discovered that they had been color blind all their lives, without being aware of it!

Most opticians are equipped with Ishihara's tests, but kindergarten teachers are not. They do not realize the implications in the everyday world. Even if they have learned about the subject in theory, they do not really know what is involved. Bus companies that display bright red numbers on a black background disregard the fact that numerous passengers are unable to read the numbers at all.

The next article will discuss everyday experiences of the color blind, and bring some examples of true stories which happened to color blind children or adults. There are also some experimental `cures' or rather, aids, which seem to help color blind people see colors for the first time in their lives.

Anyone interested in this subject will find books in any library which do not just scratch the surface but give all the names of the varying degrees of color blindness. Ishihara's tests are also available from some libraries.


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