Color blindness (patient information)
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What is color blindness?
Color blindness, a color vision deficiency, is the inability to perceive differences between some of the colors that others can distinguish.
What are the symptoms of color blindness?
Symptoms vary from person to person, but may include:
- Trouble seeing colors and the brightness of colors in the usual way
- Trouble telling the difference between red and green
- Trouble telling the difference between blue and yellow
- 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.
What are the causes of color blindness?
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.
Color blindness is often inherited genetically. It is most commonly inherited from mutations in a X-linked recessive fashion, but the mapping of the human genome has shown there are many causative mutations – mutations capable of causing color blindness originate from at least 19 different chromosomes and many different genes (as shown online at the Online Mendelian Inheritance in Man (OMIM) database at Johns Hopkins University).
Inherited color blindness can be congenital (from birth), or it can commence in childhood or adulthood. Some of the inherited diseases known to cause color blindness are:
- Cone dystrophy
- Cone-rod dystrophy
- Achromatopsia (aka rod monochromatism, aka stationary cone dystrophy, aka cone dysfunction syndrome)
- Blue cone monochromatism
- Leber's congenital amaurosis
- Retinitis pigmentosa (initially affects rods but can later progress to cones and therefore color blindness)
Other causes of color blindness include:
- Brain or retinal damage caused by shaken baby syndrome, accidents and other trauma which produce swelling of the brain in the occipital lobe
- Damage to the retina caused by exposure to ultraviolet light
- The drug hydroxychloroquine (Plaquenil), which is used to treat rheumatoid arthritis, among other conditions
Who is at risk for color blindness?
Men are at a higher risk for color blindness than women. As color blindness is commonly inherited in a X-linked recessive fashion, about 8 percent of males, but only 0.5 percent of females, are color blind in some way or another, whether it be one color, a color combination, or another mutation.[1][2] The reason males are at a greater risk of inheriting an X linked mutation is because males only have one X chromosome (XY, with the Y chromosome being significantly shorter than the X chromosome), and females have two (XX); if a woman inherits a normal X chromosome in addition to the one which carries the mutation, she will not display the mutation. Men do not have a second X chromosome to override the chromosome which carries the mutation. If 5% of variants of a given gene are defective, the probability of a single copy being defective is 5%, but the probability that two copies are both defective is 0.05 × 0.05 = 0.0025, or just 0.25%.
In addition to those who are genetically predisposed to color blindness, people who suffer from brain or retinal damage, or who take the drug hydroxychloroquine (Plaquenil), are at an increased risk of color blindness.
How to know you have color blindness?
While some people notice that they have difficulty telling the differences between certain colors, others may have such a mild case that they do not even notice any symptoms.
To be certain, your eye care specialist can check your color vision in several ways. Testing for color blindness is commonly done during an eye exam. The Ishihara color test, which consists of a series of pictures of colored spots, is the test most often used to diagnose red-green color deficiencies. A figure (usually one or more Arabic digits) is embedded in the picture as a number of spots in a slightly different color, and can be seen with normal color vision, but not with a particular color defect.
When to seek urgent medical care
Color blindness is not considered a medical emergency.
However, make an appointment with your optometrist or ophthalmologist if you think you (or your child) have color blindness.
Treatment options
There is no known treatment.
Diseases with similar symptoms
Where to find medical care for color blindness
Directions to Hospitals Treating color blindness
Prevention of color blindness
What to expect (Outlook/Prognosis)
Color blindness is a life-long condition. Most persons are able to adjust without difficulty or disability.
Sources
http://www.nlm.nih.gov/medlineplus/ency/article/001002.htm
- ↑ Sharpe, LT (1999). "Opsin genes, cone photopigments, color vision and color blindness". In Gegenfurtner KR, Sharpe LT. Color Vision: From Genes to Perception. Cambridge University Press. ISBN 9780521004398. Unknown parameter
|coauthors=ignored (help) - ↑ http://www.colblindor.com/2006/04/28/colorblind-population/