Color Blindness
Topic Overview
What is color blindness?
Color blindness results from an absence or malfunction of certain color-sensitive cells in the retina. The retina is the nerve layer at the back of the eye that converts light into nerve signals that are sent to the brain. A person with color blindness has trouble seeing red, green, blue, or mixtures of these colors.
Normally, the eye has three types of cone cells, which are light-sensitive cells that are located in the retina. Each type is sensitive to either red, green, or blue light. You see color when your cone cells sense different amounts of these three basic colors. When one or more of these types of cone cells is absent or fails to function properly, you may not see one of these three colors or you may see a variation of that color or a different color.
Cone cells are concentrated mostly in the central part of the retina (the macula) to provide clear, sharp color vision. They work best in relatively bright light, so it is difficult to see colors in dim light. See an picture of the eye
that shows the retina and the macula.
The term “color vision problem” is often used instead of color blindness because most people with color blindness can see some color. Very few people with color blindness can see no color at all.
What causes color blindness?
Most color vision problems are inherited (genetic) and are present at birth. Other color vision problems are caused by aging, disease, injury to the eye (acquired color vision problems), optic nerve problems, or side effects of some medicines. Inherited color vision problems are more common than acquired problems and affect males far more often than females.
What are the symptoms?
The symptoms of color vision problems vary with the severity of the condition. In some people the problem is very minor, and they may not even be aware that they see color differently from people with normal color vision. In other people the color vision problem is severe, and they can distinguish only a few shades (a person with normal color vision can see many thousands of colors). In rare cases, a person cannot see color at all but sees only black, white, and gray.
How is color blindness diagnosed?
Tests are used to measure the ability to recognize different colors.
The most common test is the pseudoisochromatic plate test. In this test, you are asked to look at an arrangement of colored dots and identify a pattern, such as a letter or number. The type of color vision problem you have can often be determined by which patterns you can and can't see in the various plates used for the test.
For people with acquired color vision problems, an arrangement test is used. This test involves arranging colored chips in sequence according to hue (color) from a reference color. People who are color-blind 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.
A color vision problem can have a significant impact on a person's life. Color vision problems may affect learning abilities and reading development and may limit a person's career choices. However, children and adults with color vision problems can learn to compensate for their inability to see colors.
Frequently Asked Questions
Learning about color blindness:
Being diagnosed:
Getting treatment:
Ongoing concerns:
Living with color blindness:
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| Author: | Robin Parks, MS | Last Updated: October 31, 2007 |
| Medical Review: | Kathleen Romito, MD - Family Medicine Carol L. Karp, MD - Ophthalmology | |
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| Topic Contents | |
 | Topic Overview |
| Symptoms | |
| Exams and Tests | |
| Treatment Overview | |
| Home Treatment | |
| Other Places To Get Help | |
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| References | |
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