CausesBy Mayo Clinic staff
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|Anatomy of the eye|
Seeing colors across the light spectrum begins with your eyes' ability to accurately distinguish the primary colors red, blue and green.
Light enters your eye through the cornea and passes through the lens and transparent, jelly-like tissue in your eye (vitreous body) to color-sensitive cells (cones) located at the back of your eye in the retina. Chemicals in the cones distinguish colors and send that information through your optic nerve to your brain.
If your eyes are normal, you can distinguish many different blends of colors, but if your cones lack one or more light-sensitive chemicals, you may see only two of the primary colors.
Poor color vision has several causes:
Inherited disorder. About one in 12 males of Northern European descent is born with some degree of red-green color deficiency. Most females possess genes that counteract the deficiency, and less than 1 percent of females of Northern European descent have this type of color deficiency. In other populations, the prevalence of red-green color deficiency is lower.
Blue-yellow color deficiency is inherited by fewer than one in 10,000 people worldwide, and true inherited colorblindness affects fewer than one in 30,000 people. You can inherit a mild, moderate or severe degree of the disorder, and the severity doesn't change over your lifetime if the cause is inherited.
- Diseases. Some conditions that can cause color deficits are diabetes, glaucoma, macular degeneration, Alzheimer's disease, Parkinson's disease, chronic alcoholism, leukemia and sickle cell anemia. One eye may be more affected than the other and may get better if the underlying disease can be treated.
- Certain medications. Some medications can alter color vision, such as some drugs used to treat heart problems, high blood pressure, erectile dysfunction, infections, nervous disorders and psychological problems.
- Aging. Your ability to see colors deteriorates slowly as a part of aging.
- Chemicals. Exposure to some potent chemicals in the workplace, such as carbon disulfide and fertilizers may cause loss of color vision. If you work around these chemicals, have your color vision evaluated because the loss of some color vision may be too subtle for you to notice.
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- Color vision deficiency. Genetics Home Reference. http://ghr.nlm.nih.gov/condition/color-vision-deficiency. Accessed Dec. 15, 2010.
- Color vision deficiency. American Optometric Association. http://www.aoa.org/x4702.xml?prt. Accessed Dec. 15, 2010.
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- Robertson DM (expert opinion). Mayo Clinic, Rochester, Minn. Dec. 22, 2010.
- Komaromy AM, et al. Gene therapy rescues cone function in congenital achromaptopsia. Human Molecular Genetics. 2010;19:2581.