Color Deficiencies


Color vision deficiency (color blindness) means that your ability to distinguish some colors and shades is less than normal. It occurs when the color-sensitive cone cells in your eyes do not properly pick up or send the proper color signals to your brain. About eight percent of men and one percent of women are color deficient. It is usually inherited but can also result from certain diseases, injury or as a side effect of some medications.

Most people with this condition can identify some or many colors. Few people are totally "color blind."

Are there different types of color deficiencies?
Those with a red-green deficiency, the most common type, can have trouble distinguishing red and green traffic lights. People with blue-yellow deficiency, a less common type cannot distinguish blues or yellows, and they may not be able to distinguish blue from green or recognize violet.

Red-green deficiency is by far the most common form and it results in the inability to distinguish certain shades of red and green. Those with a less common type have difficulty distinguishing blue and yellow. In very rare cases, color deficiency exists to an extent that no colors can be detected, only shades of black, white and gray.

Defective color vision is usually congenital. In Caucasians, approximately 8% of males and less than 0.5% of females have inherited color defective vision. Of the males, approximately 2% are dichromats with severe deficiency. The largest group is actually trichromatic -- color weak rather than color deficient. Dichromatics are protanopes if they have a red-green deficiency related to red-insensitivity, deuteranopes if they are red-green deficient related to green-insensitivity, and tritanopes if they have blue-yellow deficiency related to blue-insensitivity. At night, dichromats may be further reduced to monochromaticity when the physiological phenomenon of small field tritanopia is added. Color vision can be affected after optic neuritis or in macular degeneration, central serous retinopathy, multiple sclerosis or as a sequela to heavy metal poisoning.

A defect of the cones which affects color detection; called "achromatopsia" in its most extreme form; X-linked genetic defect occurring in 8% of men and 0.4% of women; may also be acquired as a result of retinal disease (specifically when it affects the macula) or poisoning. Type depends on which cones are affected:

Cone Monochromats have only one type of cone and may be red-green, red-blue, or green-blue blind; occurs one in a million.

Dichromats have two types of cones; this group is further divided into: Protanopes (red-blind; see blue and green), Deuteranopes (green- blind; confuse shades of red, green and yellow), and Tritanopes (blue-blind; see red and green).

Anomalous Trichromats make up the largest group and are similar to the Dichromatic group except in intensity (Protans and Protanopes, Deutrans and Deuteranopes, Tritans and Tritanopes...similar but milder defects.

Rod Monochromatism is very rare; there is complete lack of cone function and accompanying photophobia, nystagmus, and poor visual acuity; visual fields are normal. The photophobia and nystagmus reduce with age.

How is a person tested for color deficiencies?
Most doctors have a color vision testing book in their office. Dr. Quiring has the Ishihara test, which is one of the most common testing books. This simple test takes less than a minute to perform.

Is there any treatment for color deficiencies?
Inherited color deficiency cannot be cured but the condition usually does not interfere with normal everyday life. It may, however, affect some career choices. Color filters, such as a special red contact lens worn on one eye, can be used to help some people with a color deficiency.

In the case of achromatopsia, optical aids, sunglasses, and lowered illumination may be helpful.

Color vision deficiency is usually inherited and cannot be cured, but those affected can often be taught to adapt to the inability to distinguish colors. In some cases, a special red tinted contact lens is used in one eye to aid persons with certain color deficiencies.

What does it mean for me if I am color deficient?
Although color blindness is more of a social inconvenience than a handicap, educators should be aware of students with this condition since many educational materials utilize color as an instructional vehicle. Students with color blindness may need to learn compensatory techniques for sorting or selecting clothing or interpreting traffic signals.

Genetic counseling may be indicated.

Where can I get more information?
For more information on color deficiency, send a self-addressed, stamped business-size (#10) envelope to Communications Center, Dept. Q15, American Optometric Association, 243 N. Lindbergh Blvd., St. Louis, MO 63141. If you want information on another eye care topic that is not in the Healthtouch library or on eye care for the whole family, please specify that topic when writing the American Optometric Association, which produces a wide range of consumer education materials on eye care.

Color Vision Links For More Information:
American Optometric Association
Online Color Vision Test
Color Deficiencies