Colour blindness

What is it?

Sometimes colour blindness only becomes obvious as the result of a test, say, if you want to be a pilot. It’s the inability to distinguish between certain colours.

What causes it?

It’s usually due to a genetic abnormality of the cones, the colour-sensitive cells at the back of the eye.

Cones are sensitive to short (blue), medium (green) or long (red) wavelengths of light. Chemicals in the cones trigger a reaction and send the wavelength information through your optic nerve to your brain. When light containing all colour wavelengths enters your eye, it passes to cones in the retina at the back of it.

Normal eyes perceive colour, but you’ll be unable to distinguish the colours red, green or blue if your cones lack one or more wavelength sensitive chemicals.

There are several causes of colour blindness...

Diseases such as sickle cell anaemia, diabetes, macular degeneration, Alzheimer’s, multiple sclerosis, glaucoma, Parkinson’s, chronic alcoholism, and leukaemia, with one eye possibly more affected than the other.

Inherited disorder, much more common in men than in women. The most common colour deficiency is red-green. Blue-yellow deficiency is much less common. Ageing, your ability to see colours deteriorates slowly as you age. Certain medications such as those that treat certain autoimmune diseases, heart problems, high blood pressure, erectile dysfunction, infections, nervous disorders and psychological problems. Chemicals, such as carbon disulphide and fertilisers, may cause loss of colour vision.

What’s the treatment?

Genetic colour blindness has no cure but all medicines can be changed and eye conditions treated. Treating underlying diseases may help.