Many people — about 8% of men and 1% of women — have difficulty distinguishing between some colors and shades. This is called color vision deficiency and 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.

 

The most common form is red-green deficiency, followed by blue-yellow deficiency. In very rare cases, color deficiency exists to an extent that no colors can be detected, only shades of black, white and grey.

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.

 

Since many learning materials are color-coded, it is important to diagnose color vision deficiency early in life. This is why the California Optometric Association recommends a comprehensive optometric examination before a child begins school.