HEALTH Colour blindness and deficiency

GREYSCALE Total colour blindness, where everything is seen in shades of black, white and grey, is very rare.

Have you colour vision deficiency?


Aine Higgins

A PARENT  recently attended at the optician’s with her son for an eye examination. He was struggling in school but she felt his vision was perfect. On examination he had perfect  eyesight but was struggling in school because he has a colour vision deficiency. 
People with colour vision deficiency are unable to see colours the same way that most people do, and they may have difficulty distinguishing between two different colours.
Colour vision deficiency is often incorrectly known as colour blindness. However, true colour blindness is where no colour can be seen at all, which is rare.
Colour vision deficiency occurs when the cells in the retina that interpret colour do not function normally. The retina is the thin layer of nerve cells that line the inside of the back of the eye. The cells are known as ‘cones’ and they are able to process the three primary colours: red, green and blue.
Using the primary colours, the cone cells can interpret hundreds of different colours and shades.
If someone has colour vision deficiency, the cone cells lack the right amount of chemicals to process colours accurately.

How common is colour vision deficiency?
Colour vision deficiency affects approximately one in 12 men, and one in 100 women. In most cases, the condition is inherited.
It’s quite common on the west of Ireland, and you are more at risk if your maternal grandfather or maternal uncles had a colour vision deficiency.
There are three main types of colour vision deficiency. These are described in more detail below.
Red-green deficiency (deuteranopia) - this is the most commonly diagnosed deficiency. People with this condition cannot distinguish certain shades of red and green.
Blue-yellow deficiency (tritanopia) - this is a rare condition where it is difficult to distinguish between blue and green. Yellow can appear as a pale grey or purple.
Total colour blindness (achromatopsia) - this is the rarest type of colour vision deficiency. It is where no colours can be detected and everything is seen in shades of black, white, and grey.
People with this condition have poor sight and are very sensitive to light.
Unfortunately there is no cure for colour vision deficiency, but it should not cause any other symptoms or health complications.
It should also not affect other aspects of your vision - for example, the ability to see distances or details.
In most cases, people are able to adapt to having colour vision deficiency. For example, by recognising the position of the lights on a traffic light, rather than the different colours, people with a colour vision deficiency are still able to drive.

What are the symptoms of colour vision deficiency?
There are no obvious, or physical, symptoms of colour vision deficiency. Many people have the condition without being aware of it.
If you have colour vision deficiency, you may have difficulty: identifying pale colours or identifying deep colours if there is poor lighting or if you are tired or stressed.
Colour vision deficiency can vary in severity. Some people will only experience a very slight difference in the way that they appreciate different hues and shades of colour. For others, many colours will all appear to look the same.

Aine Higgins is an optician based in Mongey’s Opticians, Castlebar and Ballinrobe. She was the first Irish optician to be nominated for the UK and Ireland Optician of the Year 2010.