Colour vision deficiency - Causes 

Causes of colour vision deficiency 

To see colour accurately, your eyes need to be able to distinguish between the three primary colours – red, green and blue.

How the eye detects colour

When light enters your eye, it passes through the lens at the front of your eye before reaching the colour-sensitive cells, called cones, of the retina (the layer of cells that lines the inside of the back of the eye).

There are three different types of cone cells – blue, green and red (also known as short, medium and long wavelength cones) – which detect different wavelengths of light.  

The cones interpret which colour you are seeing and send a message to your brain through the optic nerve. If your cone cells function normally, you will be able to distinguish between hundreds of different colour combinations.

However, if you are missing one of the types of cone cells, or if the cones are not functioning normally, you may see colours differently.

Inherited colour vision deficiency

Most people with colour vision deficiency inherit the condition from their parents. An inherited colour vision deficiency usually affects the way you see green and red colours.

Your condition can vary from mild to severe but it will not get worse as you get older. Your colour deficiency will stay the same, provided you do not develop any other conditions or take medication that could affect your sight.

Other health conditions

Sometimes, colour vision deficiency can be caused by an illness or a pre-existing health condition. If you have colour deficiency as a result of a health condition, you will usually have problems seeing blue and yellow colours. Your colour vision may also be worse in one eye than the other.

Conditions which can cause colour vision deficiency include:

  • diabetes – a long-term condition that is caused by too much glucose in the blood
  • glaucoma – a group of eye conditions that affect vision
  • optic neuritis – inflammation of the optic nerve (the nerve that transmits images to the brain) this condition is sometimes associated with multiple sclerosis
  • age-related macular degeneration – a painless eye condition that affects the retina
  • alcoholism
  • sickle cell anaemia – an inherited blood disorder where red blood cells develop abnormally

If your condition is treatable, it may also be possible to improve your colour vision deficiency. However, if your condition gets worse, your colour vision deficiency may become more severe.


Some medications can cause abnormalities in colour vision. If the abnormality is caused by medication, your sight will usually correct itself once you stop taking the medication.

Speak to your GP if you find it difficult to distinguish colours after taking a medicine. They may be able to prescribe an alternative medication for you. However, do not stop taking prescribed medication unless your GP specifically advises you to do so.

Medicines that can cause colour vision abnormalities include:


If you are exposed to chemicals as part of your job, you may be at risk of developing colour vision deficiency.

Chemicals known to cause problems with colour recognition include carbon disulfide and styrene.

Your health and safety should be protected in the workplace. If you develop a health condition, such as colour vision deficiency, speak to your employer to ensure appropriate health and safety procedures are in place and it is safe for you to continue working.

The Health and Safety Executive website provides more information and advice about health and safety at work.


Most people find their ability to distinguish colours deteriorates with age. This is a natural part of the ageing process and not something to be overly concerned about.

However, you should visit your GP if you have symptoms that start suddenly or if you are experiencing severe colour vision deficiency.

Page last reviewed: 02/04/2012

Next review due: 02/04/2014


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