October 25, 2014
ABCDEFGHIJKLMNOPQRSTUVWXYZ

Eye Health

 Health Home >> Eye Health >> Related conditions 

Colour Blindness

(Monochromatism, Deuteranopia, Protanopia, Colour Vision Deficiency)

The Facts on Colour Blindness

Colour blindness is a condition where the eyes have trouble distinguishing certain colours. Most people have either red or green colour blindness. Blue colour blindness and monochromatism, a condition in which a person sees only black, white, and grey, are very rare.

Most people have mild forms of colour blindness that don't interfere much with their daily lives. 8% of Caucasian men and less than 1% of Caucasian women have either red or green colour blindness. This condition is rare among people of Asian, First Nations, or African descent. Colour blindness is divided between inherited and acquired kinds.

Causes of Colour Blindness

The area at the back of the eye, called the retina, is sensitive to light and colour. It contains specialized cells, called cones, which respond to colour. There are three types of cone cells. One responds best to red light, one to green light, and one to blue light. When a specific type of cone cell doesn't work properly, a person will have trouble seeing the colour that particular cone cell responds to. For example, a person with red colour blindness has a defect in red cone cells.

Most colour blindness is inherited, although some cases are caused by an injury or disease of the retina or optic nerve, the nerve that takes information from the eye to the brain. People inherit colour blindness as a result of a defect on the gene(s) for colour located on the X chromosome.

Men inherit colour blindness 10 times as often as women do. Colour blindness "shows up" in men because they have only one X chromosome. Since women inherit two X chromosomes, a healthy gene on one X chromosome can override the unhealthy gene on the other. A woman can still have the unhealthy gene; it just doesn't always show up. She can, however, pass the gene to her children. A person who doesn't have a genetic condition like colour blindness but who can pass it to her children is called a "carrier."





Symptoms and Complications of Colour Blindness

Colour blindness ranges from very mild to very severe forms, with most people having mild symptoms. People with colour blindness can't see the difference between certain colours. For example, a person with severe green colour blindness (deuteranopia) has trouble seeing the difference between oranges, greens, browns, and pale reds. In someone with severe red colour blindness (protanopia), all red colours look very dull.

A few people have trouble distinguishing blue. This condition, called tritanopia, is either inherited or is caused by a reaction to drugs or poisons that damage the retina or optic nerve. It can also be due to a loss of function in these two areas over time.

Most people don't know they have colour blindness until someone else notices they have trouble telling shades apart. For example, someone may notice the colour-blind person has trouble matching colours.

Continued... 1 | 2 | Next

Ad

The contents of this site are for informational purposes only and are meant to be discussed with your physician or other qualified health care professional before being acted on. Never disregard any advice given to you by your doctor or other qualified health care professional. Always seek the advice of a physician or other licensed health care professional regarding any questions you have about your medical condition(s) and treatment(s). This site is not a substitute for medical advice.

© 1996 - 2014 MediResource Inc. - MediResource reaches millions of Canadians each year.