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Colour Blindness

What is it?

Colour blindness is not a form of blindness at all, but a deficiency in the way you see colour. With this vision problem, you have difficulty distinguishing certain colours, such as blue and yellow or red and green.

Red-green colour deficiency is the most common form of colour blindness, affecting about 2% to 6% of all men. Much more rarely, a person may inherit a trait that reduces the ability to see blue and yellow hues. This blue-yellow colour deficiency usually affects men and women equally.

Colour Blindness


Colour blindness occurs when light-sensitive cells in the retina called cones fail to respond appropriately to variations in wavelengths of light that enable people to see the full array of colours.

The majority of people with a colour deficiency are born with it although more rarely it can result from some eye diseases.

More men than women experience colour blindness as the gene responsible is located on the sex chromosomes, the X and Y chromosomes, which determine our gender. The gene for colour vision is located on the X (female) chromosome and has no corresponding or blocking location on the Y (male determining) chromosome. A woman carrying the “colour blind” gene on one of her X chromosomes will therefore statistically have 1 in 2 of her male children manifesting colour blindness. Likewise 1 in 2 of her daughters may be a carrier for the colour blind gene- this is how colour blindness can appear to skip generations where there are no males, but is “hidden” or carried on the female chromosome.

Besides differences in genetic make-up, other causes of colour vision defects or loss include:

  • Parkinson’s disease.
  • Cataracts.
  • Hydroxychloroquine, a drug used to treat rheumatoid arthritis, among other conditions.
  • Tiagabine, an anti epileptic drug.
  • Leber’s hereditary optic neuropathy.
  • Kallman’s syndrome.

Colour blindness can occur when aging processes damage retinal cells. An injury or damage to areas of the brain where vision processing takes place can also cause colour vision deficiencies.

What are the symptoms?

test for colour blindnessDo you have difficulty telling if colours are blue and yellow, or red and green? Do other people sometimes inform you that the colour you think you are seeing is wrong? If so, these are primary signs that you have a colour vision deficiency.

Symptoms vary from person to person, but may include;

  • Trouble seeing colours and the brightness of colours in the usual way
  • Inability to tell the difference between shades of the same or similar colours

Often, the symptoms may be so mild that some persons do not know they are colour blind. A parent may notice signs of colour blindness when a child is learning their colours.

Contrary to popular belief, it is rare for a colour blind person to see only in shades of grey.

How is colour blindness detected?

Your optometrist can check your colour vision in a number of ways, all of which are quick and painless. Testing for colour blindness is commonly done during a comprehensive eye exam with an optometrist.

Colour vision testing can help determine the type of colour deficiency you have.

What treatments are available?

There is no known treatment for colour blindness. Colour blindness is a life-long condition. Some coping strategies may help you function better in a colour-oriented world.

Most people are able to adjust to colour vision deficiencies without difficulty or disability but some professions such as graphic design, electrical circuits depend on accurate colour perception.

Hence, a colour vision test is especially important in relation to vocational decisions.

Make an appointment with your optometrist if you think you (or your child) have colour blindness.

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