What is color blindness?
Color blindness means you have trouble seeing red, green, or blue or a mix of these colors. It’s rare that a person sees no color at all.
Color blindness is also called a color vision problem.
A color vision problem can change your life. It makes it harder to learn and read, and you may not be able to have certain careers. But children and adults with color vision problems can learn to make up for their problems seeing color.
What causes color blindness?
Most color vision problems are inherited (genetic) and are present at birth.
People usually have three types of cone cells in the eye. Each type senses either red, green, or blue light. You see color when your cone cells sense different amounts of these three basic colors. Most cone cells are found in the macula, which is the central part of the retina.
See a picture of the eye that shows the retina and the macula.
Inherited color blindness happens when you don't have one of these types of cone cells or they don't work right. You may not see one of these three basic colors, or you may see a different shade of that color or a different color. This type of color vision problem doesn't change over time.
A color vision problem is not always inherited. In some cases, a person can have an acquired color vision problem. This can be caused by:
- Eye problems, such as glaucoma, macular degeneration, cataracts, or diabetic retinopathy.
- Injury to the eye.
- Side effects of some medicines.
What are the symptoms?
The symptoms of color vision problems vary:
- You may see many colors, so you may not know that you see color differently from others.
- You may only be able to see a few shades of color, while most people can see thousands of colors.
- In rare cases, you may see only black, white, and gray.
How is color blindness diagnosed?
Tests measure how well you recognize different colors.
- In one type of test, you look at sets of colored dots and try to find a pattern in them, such as a letter or number. The patterns you see help your doctor determine which colors you have trouble with.
- In another type of test, you arrange colored chips in order according to how similar the colors are. People with color vision problems cannot arrange the colored chips correctly.
How is it treated?
Inherited color vision problems cannot be treated or corrected.
Some acquired color vision problems can be treated, depending on the cause. For example, if a cataract is causing a problem with color vision, surgery to remove the cataract may restore normal color vision.
You can find ways to help make up for a color vision problem, such as wearing colored contact lenses or eyeglasses or wearing glasses that block glare. You can learn to look for other things, such as brightness or location, rather than colors. For example, you can learn the order of the three colored lights on a traffic signal.
How can you help a child who has color blindness?
Color vision problems can make learning and reading hard for children, which can lead to poor schoolwork and low self-esteem.
You can help your child by:
- Making sure your child is tested for color vision problems during routine eye tests. The sooner you know there is a problem, the sooner you can help your child.
- Telling your child’s teachers and other school staff about the problem. Suggest seating your child where there is no glare and using a color of chalk that your child can see.
Frequently Asked Questions
Learning about color blindness:
Living with color blindness:
Symptoms of color blindness can vary. Different people see different shades of colors. You may not be able to see red, green, and blue or variations of those colors. If the color vision problem is not severe, you may not realize that you are seeing something different than a person who has normal color vision.
People with less severe color vision problems see variations of colors. They may not be able to tell the difference between red and green but can see blue and yellow.
People with severe color vision problems cannot see color at all. They see only shades of gray, black, and white.
Inherited color vision problems affect both eyes equally. Acquired color vision problems may occur in only one eye or may affect one eye more than the other. Inherited problems with color vision are usually present at birth and do not change. An acquired color vision problem may change over time as a person ages or during the course of the disease or injury that causes the problem.
Exams and Tests
Tests can detect color blindness by measuring the ability to recognize different colors.
A test that is used to check for inherited color vision problems is called a pseudoisochromatic plate test. For this test, you are asked to look at a square of colored dots and identify a pattern, such as a letter or number, within the colored dots. People who have normal color vision can see these patterns. People who have color vision problems can see only some of these patterns or cannot see the patterns at all. Often the type of color vision problem a person has can be determined from which patterns they can identify in the plate test.
An arrangement test is used to check for acquired color vision problems or check the severity of inherited color vision problems. This test involves arranging colored chips in sequence according to hue (color) from a reference color. People who have normal color vision can arrange the colored chips with similar color. People who have color vision problems cannot arrange the colored chips correctly.
For more information about vision tests, including tests used for color vision, see the topic Vision Tests.
Because a color vision problem can have a big impact on a person's life, it is important to detect the problem as early as possible. In children, color vision problems can affect learning abilities and reading development. And color vision problems may limit career choices. Most experts recommend eye exams for children between ages 3 and 5. Vision screening is recommended for all children at least once before entering school, preferably between the ages of 3 and 4.
Color blindness that is acquired may sometimes be improved by surgery. For example, if you are having trouble seeing colors because of cataracts, surgery to treat the cataracts may improve color vision. If the problem is caused by a side effect of medicine, color vision may be improved when that medicine is stopped.
There may be some things you can do to help compensate for a color vision problem.
- Specially tinted contact lenses and eyeglasses may help you see differences between colors. But these lenses do not provide normal color vision and can distort objects.
- Glasses that block glare (with side shields or wide temples) are helpful because people with color vision problems can see differences between colors better when there is less glare and brightness. A person with color vision problems can actually see better when the lighting is not bright.
- If you do not see color at all and rely on rod cells for vision (rod monochromatism), you may need to wear tinted or dark glasses with side shields because rod cells work better in dim light. You may also need corrective lenses (glasses or contact lenses) because vision using only the rod cells is less clear and sharp.
Color vision problems cannot be prevented.
Color blindness can have a big impact on your life. Many common activities rely on signs or signals that are color-coded, such as traffic signs, signal lights, and maps. Choosing clothing with appropriate matching or complementary colors can also be more of a challenge.
In many cases, there are ways to help compensate for your inability to see or distinguish colors by the way you observe things or by watching other people's actions. You may rely on brightness or location rather than color to identify objects. For example, you can learn the order of the three colored lights on a traffic signal and know that if the bottom light is lit, it means that the light is green and it is safe to go.
Color vision problems can affect learning abilities and reading development. Children may try to hide the fact that they cannot see certain colors by watching other classmates or even copying their work. Not being able to tell the difference between colors can be a serious problem for children and can lead to poor class work and low self-esteem.
- Testing for color vision problems during routine vision screening may help a child avoid having trouble in school. If your child is having trouble in school, have his or her vision, including color vision, checked by an eye doctor.
- If your child has color vision problems, it is important that his or her teacher be aware of this. Even simple things like reading yellow chalk on a green board can be hard for a child with color vision problems.
- You may want to offer suggestions to your child's teacher about how to help your child see better. This can include using a different color chalk or seating your child where there is no glare from bright lights. You can test your child at home with different colors of chalk, pens, and paper to find out which colors are easiest for your child to see.
Color vision problems may limit career choices. For example, color photographers, interior and clothing designers, and painters need normal color vision. Laws prohibit people with severe color vision problems from holding certain jobs, such as airline pilot, police officer, and some positions in the military.
Other Places To Get Help
|American Academy of Ophthalmology (AAO)|
|P.O. Box 7424|
|San Francisco, CA 94120-7424|
The American Academy of Ophthalmology (AAO) is an association of medical eye doctors. It provides general information and brochures on eye conditions and diseases and low-vision resources and services. The AAO is not able to answer questions about specific medical problems or conditions.
|American Optometric Association (AOA)|
|243 North Lindbergh Boulevard|
|St. Louis, MO 63141-7881|
The American Optometric Association (AOA), which is a national organization of optometrists, can provide information on eye health and eye problems.
|National Eye Institute, National Institutes of Health|
|31 Center Drive MSC 2510|
|Bethesda, MD 20892-2510|
As part of the U.S. National Institutes of Health, the National Eye Institute provides information on eye diseases and vision research. Publications are available to the public at no charge. The Web site includes links to various information resources.
|Prevent Blindness America|
|211 West Wacker Drive|
|Chicago, IL 60606|
Prevent Blindness America assists the visually impaired and provides consumer information on vision problems and vision aids. Its Web site has information about eye health and safety for children and adults. Many states have local affiliates.
Other Works Consulted
- Chang DF (2008). Color vision testing section of Ophthalmologic examination. In P Riordan-Eva, JP Whitcher, eds., Vaughan and Asbury's General Ophthalmology, 17th ed., pp. 46-59. New York: McGraw-Hill.
- Sieving PA, Caruso RC (2009). Retinitis pigmentosa and related disorders. In M Yanoff, JS Duker, eds., Ophthalmology, 3rd ed., pp. 550–559. Edinburgh: Mosby Elsevier.
|Editor||Kathleen M. Ariss, MS|
|Associate Editor||Pat Truman, MATC|
|Primary Medical Reviewer||Kathleen Romito, MD - Family Medicine|
|Specialist Medical Reviewer||Christopher J. Rudnisky, MD, FRCSC - Ophthalmology|
|Last Updated||October 7, 2009|
Last Updated: October 7, 2009
Author: Jeannette Curtis