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Color Vision Deficiency

What is color vision deficiency?

Color vision deficiency is sometimes mistakenly called "color blindness." Actually, the term describes a number of different problems people have with color vision. Abnormal color vision may vary from a mild inability to tell certain colors apart to a total inability to identify any color.

Who does color vision deficiency affect?

An estimated eight percent of males and fewer than one percent of females have color vision problems. Most color vision problems run in families and are present at birth.

A child inherits a color vision deficiency by receiving a faulty color vision gene from a parent. Abnormal color vision is found in a recessive gene on the X chromosome. Men are born with just one X and one Y chromosome. Women however have two X chromosomes. Because of this, women can sometimes overcome the faulty gene with their second normal X chromosome. Men, on the other hand, do not have a second X chromosome to help compensate for the faulty color vision gene.

Heredity does not cause all color vision problems. One common problem happens from the normal aging of the eye's lens. Our lenses are clear at birth, but the aging process causes them to darken and yellow. Older adults may have problems identifying certain dark colors, particularly blues. Certain medications such as Viagra® as well as inherited or acquired retinal and optic nerve disease, may also affect normal color vision.

What are some types of color vision deficiency?

The specialized cells in the retina are called rods and cones. We use these cells for normal vision. Rods are useful for night vision and work in dim light. Cones are responsible for color vision. They operate best in daylight. Three types of cone pigments are present in normal vision. These are sensitive to either blue green or red colored objects. Together, they let us see a wide range of colors, from purple through red.

For normal color vision, all three cone pigments must work correctly. When a cone pigment is abnormal or missing, a type of color vision deficiency results. For example, the most common deficiency causes confusion between red and green colors. Rarely, some people are born without any cones. These people are truly "color blind." They see the world in shades of gray. Most types of color vision deficiency are present at birth. There are also some types caused by eye disease or injury.

Who should be tested for color deficiency?

Any child who is having difficulty in school should be checked for possible visual problems including color vision impairment. Those who have a family history of color deficiency, have a job that requires identifying colors accurately or those who have problems identifying colors should be tested.

How do eye doctors test color vision?

There are several ways to test color vision. Simpler tests involve colored figures (either shapes or numbers) placed against a confusing background. A person with normal color vision can see the figures against the background. Those with color vision deficiencies cannot see the symbols.

A more complex test requires placing a large number of colored disks in order from one shade to another. People with different color deficiencies place the disks in different orders.

How is faulty color vision treated?

Unfortunately, there is no cure for hereditary color vision deficiency. Many people with color vision deficiency develop their own "system" or learn to identify colors by other means. Some people learn to tell colors apart by brightness and location.

If you suspect a color vision deficiency, the best advice is to consult your eye doctor.


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