Colour Blindness

Search Knowledgebase

Topic Contents

Colour Blindness

Topic Overview

Picture of a cross section of the eye

What is colour blindness?

Colour blindness means you have trouble seeing red, green, or blue or a mix of these colours. It’s rare that a person sees no colour at all.

Colour blindness is also called a colour vision problem.

A colour 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 colour vision problems can learn to make up for their problems seeing colour.

What causes colour blindness?

Most colour 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 colour when your cone cells sense different amounts of these three basic colours. 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 colour 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 colours, or you may see a different shade of that colour or a different colour. This type of colour vision problem doesn't change over time.

A colour vision problem is not always inherited. In some cases, a person can have an acquired colour vision problem. This can be caused by:

What are the symptoms?

The symptoms of colour vision problems vary:

  • You may see many colours, so you may not know that you see colour differently from others.
  • You may only be able to see a few shades of colour, while most people can see thousands of colours.
  • In rare cases, you may see only black, white, and grey.

How is colour blindness diagnosed?

Tests measure how well you recognize different colours.

  • In one type of test, you look at sets of coloured dots and try to find a pattern in them, such as a letter or number. The patterns you see help your doctor determine which colours you have trouble with.
  • In another type of test, you arrange coloured chips in order according to how similar the colours are. People with colour vision problems 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.

You can find ways to help make up for a colour vision problem, such as wearing coloured 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 colours. For example, you can learn the order of the three coloured lights on a traffic signal.

How can you help a child who has colour blindness?

Colour 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 colour 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 colour of chalk that your child can see.

Frequently Asked Questions

Learning about colour blindness:

Being diagnosed:

Getting treatment:

Ongoing concerns:

Living with colour blindness:

Symptoms

Symptoms of colour blindness can vary. Different people see different shades of colours. You may not be able to see red, green, and blue or variations of those colours. If the colour vision problem is not severe, you may not realize that you are seeing something different than a person who has normal colour vision.

People with less severe colour vision problems see variations of colours. They may not be able to tell the difference between red and green but can see blue and yellow.

People with severe colour vision problems cannot see colour at all. They see only shades of grey, black, and white.

Inherited colour vision problems affect both eyes equally. Acquired colour vision problems may occur in only one eye or may affect one eye more than the other. Inherited problems with colour vision are usually present at birth and do not change. An acquired colour vision problem may change over time as a person ages or during the course of the disease or injury that causes the problem.

Examinations and Tests

Tests can detect colour blindness by measuring the ability to recognize different colours.

A test that is used to check for inherited colour vision problems is called a pseudoisochromatic plate test. For this test, you are asked to look at a square of coloured dots and identify a pattern, such as a letter or number, within the coloured dots. People who have normal colour vision can see these patterns. People who have colour vision problems can see only some of these patterns or cannot see the patterns at all. Often the type of colour 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 colour vision problems or check the severity of inherited colour vision problems. This test involves arranging coloured chips in sequence according to hue (colour) from a reference colour. People who have normal colour vision can arrange the coloured chips with similar colour. People who have colour vision problems cannot arrange the coloured chips correctly.

For more information about vision tests, including tests used for colour vision, see the topic Vision Tests.

Early detection

Because a colour 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, colour vision problems can affect learning abilities and reading development. And colour vision problems may limit career choices. Most experts recommend eye examinations 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.

Treatment Overview

There is no medical treatment for colour blindness that is inherited. Some acquired colour vision problems can be treated, depending on the cause.

Colour blindness that is acquired may sometimes be improved by surgery. For example, if you are having trouble seeing colours because of cataracts, surgery to treat the cataracts may improve colour vision. If the problem is caused by a side effect of medicine, colour vision may be improved when that medicine is stopped.

There may be some things you can do to help compensate for a colour vision problem.

  • Specially tinted contact lenses and eyeglasses may help you see differences between colours. But these lenses do not provide normal colour vision and can distort objects.
  • Glasses that block glare (with side shields or wide temples) are helpful because people with colour vision problems can see differences between colours better when there is less glare and brightness. A person with colour vision problems can actually see better when the lighting is not bright.
  • If you do not see colour 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.

Colour vision problems cannot be prevented.

Home Treatment

Colour blindness can have a big impact on your life. Many common activities rely on signs or signals that are colour-coded, such as traffic signs, signal lights, and maps. Choosing clothing with appropriate matching or complementary colours can also be more of a challenge.

In many cases, there are ways to help compensate for your inability to see or distinguish colours by the way you observe things or by watching other people's actions. You may rely on brightness or location rather than colour to identify objects. For example, you can learn the order of the three coloured 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.

Colour vision problems can affect learning abilities and reading development. Children may try to hide the fact that they cannot see certain colours by watching other classmates or even copying their work. Not being able to tell the difference between colours can be a serious problem for children and can lead to poor class work and low self-esteem.

  • Testing for colour 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 colour vision, checked by an eye doctor.
  • If your child has colour 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 colour 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 colour chalk or seating your child where there is no glare from bright lights. You can test your child at home with different colours of chalk, pens, and paper to find out which colours are easiest for your child to see.

Colour vision problems may limit career choices. For example, colour photographers, interior and clothing designers, and painters need normal colour vision. Laws prohibit people with severe colour vision problems from holding certain jobs, such as airline pilot, police officer, and some positions in the military.

Other Places To Get Help

Organizations

Canadian National Institute for the Blind
1929 Bayview Avenue
Toronto, ON  M4G 3E8
Phone: (800) 563-2642
Fax: (416) 480-7677
Email: info@cnib.ca
Web Address: http://www.cnib.ca
 

The Canadian National Institute for the Blind is a voluntary agency dedicated to helping improve the lives of the blind and visually impaired, preventing blindness, and promoting sight enhancement services. The organization offers a variety of publications and educational resources about vision loss and impairment, including pamphlets, newsletters, and a quarterly magazine.


Canadian Ophthalmological Society
610-1525 Carling Avenue
Ottawa, ON  K1Z 8R9
Email: cos@eyesite.ca
Web Address: www.eyesite.ca/english/index.htm
 

The Canadian Ophthalmological Society is an association of eye doctors dedicated to helping the public take good care of their eyes and vision. This group provides educational information on eye conditions and diseases and eye safety.


National Eye Institute, National Institutes of Health
Information Office
31 Center Drive MSC 2510
Bethesda, MD  20892-2510
Phone: (301) 496-5248
Email: 2020@nei.nih.gov
Web Address: www.nei.nih.gov
 

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.


Related Information

References

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.

Credits

By Healthwise Staff
Primary Medical Reviewer Kathleen Romito, MD - Family Medicine
Primary Medical Reviewer Anne C. Poinier, MD - Internal Medicine
Specialist Medical Reviewer Christopher J. Rudnisky, MD, MPH, FRCSC - Ophthalmology
Last Revised November 6, 2009

This information does not replace the advice of a doctor. Healthwise, Incorporated disclaims any warranty or liability for your use of this information.