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Alternative Names : Color deficiency; Blindness – color
Definition: Color blindness is the inability to see certain colors in the usual way.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. The English chemist John Dalton in 1798 published the first scientific paper on the subject, “Extraordinary facts relating to the vision of colours”, after the realization of his own color blindness; because of Dalton’s work, the condition is sometimes called Daltonism, although this term is now used for a type of color blindness called deuteranopia.…………....CLICK & SEE
Color blindness is usually classed as disability; however, in selected situations color blind people may have advantages over people with normal color vision. There are some studies which conclude that color blind individuals are better at penetrating certain camouflages. Monochromats may have a minor advantage in dark vision, but only in the first five minutes of dark adaptation.
Causes:
Color blindness occurs when there is a problem with the color-sensing materials (pigments) in certain nerve cells of the eye. These cells are called cones. They are found in the retina, the light-sensitive layer of tissue at the back of the inner eye.
If you are missing just one pigment, you might have trouble telling the difference between red and green. This is the most common type of color blindness. Other times, people have trouble seeing blue-yellow colors. People with blue-yellow color blindness almost always have problems identify reds and greens, too.
The most severe form of color blindness is achromatopsia. A person with this rare condition cannot see any color. Achromatopsia is often associated with lazy eye, nystagmus (small, jerky eye movements), severe light sensitivity, and extremely poor vision.
There are many types of color blindness. The most common are red-green hereditary (genetic) photoreceptor disorders, but it is also possible to acquire color blindness through damage to the retina, optic nerve, or higher brain areas. Higher brain areas implicated in color processing include the parvocellular pathway of the lateral geniculate nucleus of the thalamus, and visual area V4 of the visual cortex. Acquired color blindness is generally unlike the more typical genetic disorders. For example, it is possible to acquire color blindness only in a portion of the visual field but maintain normal color vision elsewhere. Some forms of acquired color blindness are reversible. Transient color blindness also occurs (very rarely) in the aura of some migraine sufferers.
The different kinds of inherited color blindness result from partial or complete loss of function of one or more of the different cone systems. When one cone system is compromised, dichromacy results. The most frequent forms of human color blindness result from problems with either the middle or long wavelength sensitive cone systems, and involve difficulties in discriminating reds, yellows, and greens from one another. They are collectively referred to as “red-green color blindness”, though the term is an over-simplification and is somewhat misleading. Other forms of color blindness are much more rare. They include problems in discriminating blues from yellows, and the rarest forms of all, complete color blindness or monochromacy, where one cannot distinguish any color from grey, as in a black-and-white movie or photograph.
Most color blindness is due to a genetic problem. About 1 in 10 men have some form of color blindness. Very few women are color blind.
The drug hydroxychloroquine (Plaquenil) can also cause color blindness. It is used to treat rheumatoid arthritis, among other conditions.
If your clothes don’t match, someone might have teased you about being color-blind. But some people really are color-blind. It doesn’t mean they can’t see any color at all, like a black and white movie. It means that they have trouble seeing the difference between certain colors. (Check out the image on the right to see how well you see colors.)
CLICK & TEST YOUR COLOR VISION
Being color-blind can make it tricky to match your shirt and pants, but it’s not a serious problem. People who are color-blind can do normal stuff, even drive. Most color-blind people can’t tell the difference between red or green, but they can learn to respond to the way the traffic signal lights up. The red light is generally on top and green is on the bottom.
Cones and Color:
To understand what causes color blindness, you need to know about the cones in your eyes. Cones in your eyes? Yes, but they’re very small. These cones are cells on your retina, an area the size of a postage stamp that’s at the back of your eye.
You have “red,” “blue,” and “green” cones, which are sensitive to those colors and combinations of them. You need all three types to see colors properly. When your cones don’t work properly, or you don’t have the right combination, your brain doesn’t get the right message about which colors you’re seeing. To someone who’s color-blind, a green leaf might look tan or gray.
Color Blindness Is Passed Down:
Color blindness is almost always an inherited (say: in-her-ut-ed) trait, which means you get it from your parents. You get inherited traits through genes (say: jeenz), which determine everything about your body, including how tall you’ll be and whether your hair will be straight or curly.
…………....CLICK & SEE
Eye doctors (and some school nurses) test for color blindness by showing a picture made up of different colored dots, like the one above. If a person can’t see the picture or number within the dots, he or she may be color-blind.
Boys are far more likely to be color-blind. In fact, if you know 12 boys, one of them is probably at least a little color-blind. So girls, the next time a boy asks you if something matches, you’d better lend him a hand!
Symptoms :
Symptoms vary from person to person, but may include:
- Trouble seeing colors and the brightness of colors in the usual way
- Inability to tell the difference between shades of the same or similar colors
Often, the symptoms may be so mild that some persons do not know they are color blind. A parent may notice signs of color blindness when a child is learning his or her colors.
Rapid, side-to-side eye movements and other symptoms may occur in severe cases.
Exams and Tests:
Your doctor or eye specialist can check your color vision in several ways. Testing for color blindness is commonly done during an eye exam…..….CLICK & SEE
Treatment:
THERE IS NO TREATMENT
Outlook (Prognosis) :
COLOR BLINDNESS IS A LIFE-LONG CONDITION. MOST PERSONS ARE ABLE TO ADJUST WITHOUT DIFFICULTY OR DISABILITY. .
Possible Complications :
THOSE WHO ARE COLORBLIND MAY NOT BE ABLE TO GET CERTAIN JOB THAT NEEDS COLOR VISION. FOR EXAMPLE , A PILOT NEEDS TO BE ABLE TO SEE COLORS.
When to Contact a Medical Professional :
Make an appointment with your health care provider or ophthalmologist if you think you (or your child) have color blindness.
Click to learn more about Color blindness
Resources:
http://www.nlm.nih.gov/medlineplus/ency/article/001002.htm
http://kidshealth.org/kid/talk/qa/color_blind.html
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