Colour Blindness
Topic Overview
What is colour blindness?
Colour blindness results from an absence or malfunction of certain colour-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 colour blindness has trouble seeing red, green, blue, or mixtures of these colours.
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 colour when your cone cells sense different amounts of these three basic colours. 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 colours or you may see a variation of that colour or a different colour.
Cone cells are concentrated mostly in the central part of the retina (the macula) to provide clear, sharp colour vision. They work best in relatively bright light, so it is difficult to see colours in dim light. See an picture of the eye
that shows the retina and the macula.
The term “colour vision problem” is often used instead of colour blindness because most people with colour blindness can see some colour. Very few people with colour blindness can see no colour at all.
What causes colour blindness?
Most colour vision problems are inherited (genetic) and are present at birth. Other colour vision problems are caused by aging, disease, injury to the eye (acquired colour vision problems), optic nerve problems, or side effects of some medicines. Inherited colour vision problems are more common than acquired problems and affect males far more often than females.
What are the symptoms?
The symptoms of colour 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 colour differently from people with normal colour vision. In other people the colour vision problem is severe, and they can distinguish only a few shades (a person with normal colour vision can see many thousands of colours). In rare cases, a person cannot see colour at all but sees only black, white, and grey.
How is colour blindness diagnosed?
Tests are used to measure the ability to recognize different colours.
The most common test is the pseudoisochromatic plate test. In this test, you are asked to look at an arrangement of coloured dots and identify a pattern, such as a letter or number. The type of colour 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 colour vision problems, an arrangement test is used. This test involves arranging coloured chips in sequence according to hue (colour) from a reference colour. People who are colour-blind cannot arrange the coloured chips correctly.
How is it treated?
Inherited colour vision problems cannot be treated or corrected. Some acquired colour vision problems can be treated, depending on the cause. For example, if a cataract is causing a problem with colour vision, surgery to remove the cataract may restore normal colour vision.
A colour vision problem can have a significant impact on a person's life. Colour vision problems may affect learning abilities and reading development and may limit a person's career choices. However, children and adults with colour vision problems can learn to compensate for their inability to see colours.
Frequently Asked Questions
Learning about colour blindness:
Being diagnosed:
Getting treatment:
Ongoing concerns:
Living with colour blindness:
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| Author: | Alison Allen Robin Parks, MS | Last Updated: December 6, 2007 |
| Medical Review: | Kathleen Romito, MD - Family Medicine Carol L. Karp, MD - Ophthalmology Anne C. Poinier, MD - Internal Medicine | |
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| Topic Contents | |
 | Topic Overview |
| Symptoms | |
| Examinations and Tests | |
| Treatment Overview | |
| Home Treatment | |
| Other Places To Get Help | |
| Related Information | |
| References | |
| Credits | |