Colour vision deficiency

What is colour vision deficiency?

Colour vision deficiency is a difficulty in distinguishing between colours. This is different from colour blindness which means that someone cannot see any colour at all, and this is very rare.

Total colour blindness

If you have been diagnosed with a colour vision deficiency, you are able to see colours, but you may not see as many variations and you may confuse colours.

What is the cause of colour vision deficiency?

The cause is most commonly hereditary (genetic information passed on from your biological parents), but can sometimes miss out generations. These genetic changes affect the retina.

What is the retina?

When light enters the eye, it is focussed to form an image at the back-surface, on a light-sensitive layer known as the retina. This light sensitive layer is made up of cone and rod cells. These cone cells let us see colour, so if there are changes to the cone cell, it can cause a colour vision deficiency.

How do you test for a colour vision deficiency?

There are a few simple tests that can be done during your eye appointment.

Results will show us if there is a colour vision deficiency, but will not specify the exact colours your child may confuse, as this will not affect the advice you receive.

What colours will my child have difficulties with?

The most common type is known as “red-green” colour vision deficiency meaning people see greens and reds as the same colour. This is because the cone cells for green and red overlap.

There are 3 types of colour deficiency:

Protanopia (red)

Red is usually confused with:

• blacks and reds
• browns and greens
• oranges and reds

Protanopia

Normal vision

Deuteranopia (green)

Green is usually confused with:

• reds and greens or browns
• greens with yellows
• pinks and greys

Deuteranomalia

Normal vision

Tritanopia (blue)

Blue is usually confused with:

• blues and greys
• purples and blacks
• greens and blues

Tritanopia

Normal vision

Is there any treatment?

No. Colour deficiency will be present from birth, but will not get any worse. Although there is no treatment, there are practical steps you can take to better support your child.

How can I support my child?

Your child may first notice difficulties with colour vision during school, as often colours are used to help with teaching. If a colour vision deficiency has been found at your eye appointment, it may be worth taking the below steps:

• make sure there is good lighting at home and in school
• inform their teachers to see if they can make changes or adjustments in lessons and exams
• adjust settings on any devices (laptops, tablets, phones) to improve colour levels
• explain the pattern rather than relying on the colours if possible. For example, when looking at traffic lights, if the top light is on, this means stop, middle light means be ready to stop or go, and the bottom light means go

What does this mean in the long-term?

Colour deficiency will not change throughout life. However, if you are found to have a colour vision deficiency it would be advised to discuss this with any future employers so they can make reasonable adjustments if possible. There are a limited number of careers that may assess colour vision abilities such as the armed forces, electricians and transport services.