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Color Blindness

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A truck driver comes up to a blinking red light, but he cannot tell weather the light is blinking red or yellow. He is pretty sure it is blinking yellow so he continues on through. Another car about to pull out jerks on the brakes as the trucks surges through the intersection. Is this the drivers fault or should he have known what color the light was? Could blindness, is one of the more common forms of vision deficiency that many males and some females have to deal with on a day-to-day basis. Color blindness does not also affect the way they drive but the colors they wear, the food they cook, and can even keep them from obtaining certain jobs.

Color blindness, or color vision deficiency, in humans is the inability to perceive differences between some or all colors that other people can distinguish. It is most often of genetic nature, but may also occur because of eye, nerve, or brain damage, or due to exposure to certain chemicals. Color blindness is an inaccurate term for a lack of perceptual sensitivity to certain colors. Absolute color blindness is almost unknown.

The first person to describe color blindness was the English chemist and physicist John Dalton. Dalton is well known because he was the first modern scientist to develop the atomic theory. However, Dalton was concerned in many topics besides atoms. For example, he was keenly interested in meteorology, which is the study of weather and kept daily weather records for fifty-seven years. His records, published as Meteorological Observations and Essays, are among the most complete in all of scientific history. The first scientific paper Dalton ever wrote was about color blindness. He most likely became interested in the subject of color blindness because he, as well as his brother, was color blind. After the discovery that he and his brother were color blind, Dalton, in 1798, published the first scientific paper on the subject, "Extraordinary facts relating to the vision of colours". In honor of his research, the condition of color blindness is still sometimes called daltonism, although this term is now used for a type of color blindness called deuteranopia.

The normal human retina contains two kinds of light sensitive cells, the rod cells, which are active in low light and the cone cells, which are active in normal daylight. Normally, there are three kinds of cones, each containing a different pigment. The cones are activated when the pigments absorb light. The absorption spectra of the pigments vary; one is extremely sensitive to short wavelengths, one to medium wavelengths, and the third to long wavelengths. The wavelengths peak sensitivities are in the blue, yellowish-green, and yellow regions of the color spectrum. The absorption spectra of all three systems cover much of the visible spectrum, so it is not entirely accurate to refer to them as "blue", "green" and "red" receptors, especially because the "red" receptor actually has its peak sensitivity in the yellow. The sensitivity of normal color vision actually depends on the overlap between the absorption spectra of the three systems. Different colors are recognized when the different types of cone are stimulated to different extents. For example, red light stimulates the long wavelength cones much more than either of the others, but the steady change in color seen, as wavelength reduces, is the result of the other two cone systems being gradually stimulated as well.

There are three types of color receptors in our eyes, red, green and blue. We also have black and white receptors. These black and white receptors are more sensitive than the color receptor, which is why we have poor color perception in the dark.

Color blindness comes as a result of a lack of one or more of the types of color receptors. Most color perception defects are for red or green or both. About 10% of males have a color perception defect, but this is rare in females. Red-green color blindness is a result of a lack of red receptors.

Another form of color blindness is yellow-blue color blindness and is the second most common form, but it is extremely rare. It is also possible to have the color receptors missing entirely, which would result in black and white vision. This is known as total color blindness but is also extremely rare. There is no cure or treatment for color blindness. Most people with the disorder learn to live with the problem and learn how to adjust to it.

There are five different types of color blindness some that are more severe than others and others that are just different than others; different in a good way and different in a bad way. They are a mild color deficiency that is present when one or more of the three cones functions poorly. A more severe color deficiency is present when one of the cones does not function at all or is missing.

Protanomaly is the first type of color blindness and one out of every100 males has this type of color blindness. Protanomaly is referred to as "red-weakness"; this is an appropriate description of this form of color deficiency due to its nature. The protanomalous viewer sees red much more weakly than that of a normal observer, both in conditions of its saturation, or known as depth of color, and its brightness. Red, orange, yellow, yellow-green, and green, appear somewhat shifted in color. They appear shifted in color mainly towards green, and all appear paler than they do to the normal observer. The redness component that a normal observer sees in a violet or lavender color is so weakened for the protanomalous observer. The protanomalous observer will also only see the blue component because of the failure of these colors. For this reason to the protanomalous observer the color that the normal viewer calls "violet" may look only like another shade of blue. Under poor conditions, such as when driving in bright sunlight or in rainy or foggy weather, it is easily possible for protanomalous individuals to mistake a blinking red traffic light from a blinking yellow or amber one, or to fail to distinguish a green traffic light from the various "white" lights in front of stores, signs, and street lights that line many streets. Do not let the protanomalous viewer adjust the color on the television, because it will look far too reddish or violet for the rest of the family members.

The next type of color blindness is deuteranomaly blindness. Because five out of every 100 males have this type of color blindness this makes this the most common form of color blindness. Let the deuteranomalous person adjust your television and they would add more green and subtract red. They are considered "green weak". This is similar to the protanomalous person, meaning they are poor



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