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Causes
By Mayo Clinic staff
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 lens and passes through the transparent, jelly-like main body of your eye (vitreous body) to color-sensitive cells (cones) at the back of your eye. Chemicals in the cones distinguish among colors and send that information through your optic nerve to your brain.
If your eyes are normal, you can distinguish hundreds of 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:
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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, 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, fertilizers and styrene 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.
- Color vision deficiency. Genetics home reference. http://ghr.nlm.nih.gov/condition=colorvisiondeficiency. Accessed Nov. 22, 2008.
- Color vision deficiency. American Optometric Association. http://www.aoa.org/x4702.xml?prt. Accessed Nov. 25, 2008.
- Gobba F. Color vision impairment in workers exposed to neurotoxic chemicals. NeuroToxicology. 2003;24:693.
- Color vision. In: Ganong WF. Review of Medical Physiology. 22nd ed. San Francisco, Calif.: The McGraw-Hill Companies; 2005. http://www.accessmedicine.com/content.aspx?aID=707965&searchStr=color+vision+defect. Accessed Jan. 12, 2009.
