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Poor color vision
By Mayo Clinic staffMayo Clinic Health Manager
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Definition
Poor color vision is an inability to distinguish among certain shades of color. Although many people call it colorblindness, true colorblindness describes a total lack of color vision. The ability to see only shades of gray is rare.
Most people with poor color vision can't distinguish between certain shades of red and green. Less commonly, people with poor color vision can't distinguish between shades of blue and yellow.
Poor color vision is an inherited condition in most cases. Men are more likely to be born with poor color vision. Certain eye diseases and some medications also can cause color deficiency.
Symptoms
You may have poor color vision and not know it. You also may not suspect the condition in your child until a situation causes confusion or misunderstanding — such as encountering a traffic light or trying to interpret color-coded learning materials.
People affected by poor color vision may not be able to distinguish:
- Different shades of red and green
- Different shades of blue and yellow
- Any colors at all
The most common color deficiency is an inability to see some shades of red and green. Often, a person who is red-green or blue-yellow deficient isn't completely insensitive to both colors. Defects can be mild, moderate or severe. Someone with red-green or blue-yellow deficiency may not be able to differentiate the colors of a rainbow or recognize a rose-colored sky at sunrise or sunset.
Also, people with poor color vision may not be able to properly name different colors. For example, their "green" may be what normal-sighted people call "yellow." That's because they've always heard that leaves are green, so they interpret the yellow leaves they see as "green."
When to see a doctor
If you suspect that your color vision isn't satisfactory, you should see an eye doctor for testing. Also, if you have a child who's having a preschool eye exam, it's a good idea to make sure your child is tested for color vision as well as for visual acuity. Even though there's no treatment for inherited poor color vision, have your child's eyes examined if you suspect your child has poor color vision. If the cause is an eye illness, treating that illness may improve color vision.
Causes
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:
-
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.
Tests and diagnosis
If you have trouble seeing certain colors, your eye doctor can quickly and easily test to see if you have a color deficiency. Many specialists trained in diseases and disorders affecting the eye use a book containing several multicolored dot-pattern tests to provide a simple and accurate assessment of color vision deficiencies inherited at birth. If you don't have a color vision deficiency, you'll be able to pick out numbers and shapes from within the dot patterns. However, if you do have a color vision deficiency, either you'll find it difficult to see anything among the dots, or you won't see anything at all.
Treatments and drugs
No treatment can correct inherited color vision deficiencies.
If you have problems discerning shades of color, your eye doctor can determine which type of poor color vision you have and check to see if there's an associated eye disease. Eye disease isn't as common a cause of poor color vision as heredity is, but treatments that slow or reverse the course of an eye disease may help your color vision.
Wearing a colored filter over eyeglasses or a colored contact lens may enhance your perception of contrasts. But such lenses won't improve your ability to discern colors.
- 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.
