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What is color blindness? | Who is affected? | Types | Consequences | Treatment

What is color blindness?

A more accurate term for color blindness is color vision deficiency. The amount of color vision deficiency can range from a slight difficulty distinguishing among different shades of a particular color to the rare inability to distinguish any colors. A color vision deficient person may see colors, but not in the same the way a person with normal vision does.

Color vision deficiency occurs when the cones, or the light sensors in the retina that respond to color, are damaged or don't function properly. There are three types of cones that respond to red, blue, and green light. All three must be activated to get full color vision. If the function of one type of cone is disrupted, the person won't see colors the same way people who aren't color vision deficient do. They will see some colors normally, but be unable to distinguish other colors.

Who is affected?

In most instances, color vision deficiency is inherited. Color vision deficiency, a sex-linked trait, is caused by a recessive gene carried on the X-chromosome. The gene for normal color vision is a dominant gene. Since females have two X-chromosomes, they usually aren't affected by color vision deficiency even if they carry the color vision deficiency gene. They generally have a dominant normal gene masking the recessive color vision deficiency gene. However, males with the XY chromosomes have only one X chromosome. Therefore, if their X chromosome carries the gene for color vision deficiency, they will be color blind. Approximately eight percent of males are color vision deficient, while less then one percent of females are affected. There are nearly fifteen million people in North America who are color vision deficient and 250 million people worldwide.

As people age, changes occurring in the crystalline lens may cause difficulty in distinguishing colors. These changes can start happening as early as age forty. By age sixty-five, nearly ninety percent of people have some clinically detectable abnormalities in their color vision. However, this is not considered true color vision deficiency. In addition, medications and retinal or optic nerve disease may disrupt normal color vision.

Types

There are three categories of color vision deficiency.

• Deuteranamolous - red and green color confusion
• Protanamolous - red and bluish-green color confusion
• Tritanamolous - blue and yellow color confusion

The most common type of color vision deficiency is deuteranopia while the rarest type is tritanopia. The inability to see any color is called achromatopsia or monochromatism and is extremely rare.

Consequences

Color vision deficiency can put people at a disadvantage. They may have difficulty with something as simple as matching shirts, ties, and socks. They may need assistance in shopping for clothing or making daily clothing selections. Women with color vision deficiency may have difficulty selecting and applying cosmetics.

People with color vision deficiency may also have difficulty telling if meats are raw, undercooked, or burnt.

Many learning and educational materials are color-coded and consequently, a child with color vision deficiency may have trouble at school. Examples of materials that are color coded include pictures, images and writing in beginner books; maps and globes; crayons, paints, paper, and markers; and Legos and other building blocks.

As adults, people with color vision deficiency may have difficulty with computer interfaces and monitors, and communicative signs and signals. Color vision deficiency may prevent a person from taking certain jobs that require accurate color recognition. These jobs include being pilots, air traffic controllers, police officers, firefighters, electricians, textile workers, printers, and color photographers.

Treatment

At this time, there is no cure for color blindness. Affected people must learn to live with it. With training, they may learn to distinguish some colors using clues such as brightness or location.

In addition, new color vision enhancement glasses have been recently introduced that can improve color vision discrimination for people with color vision deficiency. The prescription is based on your type of color deficiency as well as the severity of the deficiency, and can be integrated with your eyeglass prescription into standard eyeglass or sunglass frames.