Q: What is color blindness, and are there any treatments?
A: More accurately called "color vision deficiency," color blindness is the inability to distinguish colors, most often shades of red and green. Only rarely does a person not see any color at all (achromatopsia).
Color vision deficiency is almost always hereditary. Some people don't know they see colors incorrectly unless they happen to be tested. More men than women (8 percent vs. less than 1 percent) are affected because the faulty gene is carried on the X chromosome. Since men have only one X chromosome, the trait is more likely to be expressed, whereas women, with two X chromosomes, are likely to have a normal gene that will be dominant.
Infrequently, color deficiency is a result of retinal disease or other eye disorders, or a side effect of certain medications. The retina has three types of color-sensing cone cells (red, green and blue). Normally, signals from cone cells are blended, so the brain perceives a full spectrum of colors. But a genetic defect can cause red to look brown, or create confusion between green and yellow. Rarely are blue cone cells affected.
There's no cure for inherited color deficiency. Some people learn to distinguish colors in other ways (standardized traffic lights, for example, are green on the bottom, red on top). Certain tinted glasses may help in some cases.
Adapted from The University of California, Berkeley Wellness Letter (March 2012)