Color vision deficiency 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.
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 grey.
Because many learning materials are color-coded, it is important to diagnose color vision deficiency early in life. This is why the American Optometric Association recommends a comprehensive optometric examination before a child begins school.
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 people with certain color deficiencies.