As many as twenty-five million North Americans may be walking around with a congenital, incurable, and occasionally life threatening condition. I’m talking about colour blindness. This problem may affect one in twelve men and one in two hundred women, and often we are unaware of it. I only realized I had a slight touch of it when my wife pointed out that my green socks were actually blue!

John Dalton, the famous chemist who developed atomic theory, was afflicted with the most common and dangerous form of colour blindness. He was unable to distinguish red from green.

Sufferers with this condition can only tell that the traffic light is red by the position of the light. When a red light has no such additional information to clarify its colour, colour blindness can be quite dangerous.

The retina at the back of the eye contains receptors called “cones,” which can distinguish different colours. In colour blind people, different colours produce the same signals from the cones. This information is then transmitted through nerve cells to the brain as similar colours.

There is the possibility that in the future, opticians may be able to offer colour blind people eye glasses with special sensors. These will be able to transform any light falling on them into colours, which the wearer’s retina can distinguish.

So next time you choose that special tie, check with a friend to make sure it matches.