Is it true that colour blindness only affects boys?

It’s estimated that up to eight per cent of boys have some degree of colour blindness (also known as colour vision deficiency or CVD), whereas less than one per cent of girls do. That’s about one in 12 boys, and around one in 200 girls.

Colour blindness has different causes. For most people with the condition, it’s genetically inherited from their mothers on the 23^rd chromosome. That’s the one that determines gender. For a boy to be red-green colour blind, it’s just a matter of a faulty colour-blindness gene on his X chromosome. For girls, that faulty gene must be present on both their X chromosomes – hence the greater prevalence of red-green colour blindness among males. Note however, that blue colour blindness affects boys and girls equally, since it is carried on a non-sex chromosome.

 

Cone cells in the retina of the eye are divided into three groups – red, blue, and green – according to their sensitivity to certain colours or colour combinations. If these cones don’t function correctly, then the brain gets inaccurate messages about colour. For example, that green traffic light may appear to be tan-coloured or grey.

Most colour-blind people can see things as clearly as other people do, but they can’t fully see red, green or blue light. In some uncommon cases, colour-blind people cannot see any colour at all.

 

The most common form of colour blindness is red-green, where any colour with any element of red or green in it will not be seen completely. That means it goes beyond just red and green. Blues and purples may be indistinguishable to the red-green colour-blind person, because the red component in the purple will not be visible.

 

People can also become colour blind as a result of diabetes, multiple sclerosis and other diseases. They can also acquire the condition over time as a result of aging or the use of certain drugs such as antibiotics and high-blood pressure medications.

Colour blindness can range from mild and moderate to severe. Some colour-blind people may not even know about their condition. If you’re concerned about this aspect of your children’s vision, you can consult your family eye doctor or their school nurse about tests for colour blindness.