When looking at a rainbow, most people can distinguish six distinct bands of colour – red, orange, yellow, green, blue and violet. However people with colour deficiency, or colour blindness as it is commonly known, don’t perceive colour in the same way. For example, they may not distinguish between red and green, or even blue and yellow.
A person can be born with colour perception deficiencies.
Around eight in 100 males and four in 1000 females inherit colour deficiency. People may not even realise they have colour perception difficulties – it might take a random comment like “it looks more red to me” for it to be drawn to their attention that they are not seeing colour in the same way as everyone else.
Retinal eye disease such as macular degeneration, optic nerve diseases or brain damage can affect colour perception.
If you have cataracts, everything will appear more yellowy. In fact Monet’s paintings became more yellow as his cataracts developed. When the cataracts are removed colours will appear more vibrant again.
Red-green deficiency is the most common
It occurs when a person has abnormal pigment in the cone cells of the retina at the back of the eye.
The red, green and blue cones are responsible for us seeing colour. They each have a pigment that is receptive to certain wavelengths of light enabling us to see different colours. If you have difficulty seeing green (deuteranomaly), the cones for the colour green are defective, or difficulty seeing red (protanomaly) means the red cones do not work properly.
There is no treatment for either form of red-green deficiency.
Blue-yellow deficiency is rare
This combination affects around one in 10,000 people; men and women equally. It is caused by a mutation on chromosome 7 (tritanomaly), causing confusion of blue colour with green and yellow with violet.
If you’ve inherited a colour deficiency, it can’t be cured. If your problem has been caused by medicines or chemicals, eliminating these may improve your colour perception.
Special colour filter lenses can help expand the range of distinguishable colours while also making them more vivid, but they can’t cure colour deficiency.
Your optometrist can carry out tests to determine whether or not you have a colour deficiency.
The most common test is the Isihara which diagnoses a red-green colour or blue-yellow colour deficiency. This is a book of 24 colour plates with the pictures made up of a series of dots. Usually a number is discernible, but if you have a colour deficiency you’ll see a different number to people with normal colour vision or nothing at all.
Can you see the numbers 3 and 29 in the pictures?
If not, or if you have any concerns about your colour vision, contact one of our practices for an appointment with an optometrist.