DEAR DOCTOR K: Why are some people colorblind?
DEAR READER: People who are colorblind are unable to see colors the way most people do. True colorblindness, in which everything appears black, gray or white, is rare. More often, “colorblind” people have trouble distinguishing colors from one another.
Light that enters our eyes is focused by the lens to fall on the back of the eye – the retina. Within the retina are 7 million cone cells. These specialized cells contain chemicals, called photopigments, that react to different wavelengths in light. The color of light is determined by its wavelength. Photopigments respond to blue, green or red light. Colorblindness occurs when the eye either lacks certain photopigments, or when these pigments do not work as they should.
Most people who are colorblind inherit the condition. Rarely, a condition that develops later in life causes colorblindness. (……)
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