Colour Vision Deficiency (Colour Blindness)

By Lucy Bailey (Optometrist)

Colour vision deficiency means people have difficulty distinguishing between certain shades of colour. Usually they can see some colours and their ability to see fine details are as well as individuals with full colour vision.

Colour vision deficiency is often inherited, and affects 1 in 12 boys compared to 1 in 200 girls.

Eye cells and vision

The retina (a layer inside the back of your eye) has two types of light-sensitive cells called rods and cones. Rods work in low light conditions to help night vision, and cones work in daylight and are responsible for colour discrimination.

Each cone cell has pigments which are sensitive to either red, green or blue light (long, medium or short wavelengths). They register the different colours and send information through the optic nerve to the brain. If the cones don’t have these pigments, the affected individual will be unable to see all the colours.

How colour vision deficiency occurs

Colour vision deficiency is most commonly a genetic condition (you are born with it). The genes involved are on the X chromosome. Therefore, boys will inherit the gene through their mother’s side of the family.

Colour vision problems can also occur later in life from disease, trauma or exposure to toxins.

Red-green colour vision deficiency: is the most common inherited type. People cannot see the red and green components of colours. They may confuse red and green with each other or with yellow. There are two types of red/green colour deficiency protonopia and deutronopia.

Blue-yellow colour vision deficiency (tritanopia): makes it difficult to tell the difference between shades of blue and green. Yellow may also be hard to identify – it may look violet/grey or pink. Blue-yellow colour vision deficiency is very rare (1 in 10,000) with males and females affected equally. 

People who are totally colour blind, a condition called achromatopsia, can only see things as black and white or in shades of grey.

Occupations and colour vision deficiency

People who have a colour vision deficiency may be restricted in carrying out certain occupations where reliable colour recognition is required. Common occupations that may have colour vision requirements include police, maritime careers and the defence force.

In Australia, it is possible for people with colour vision deficiency to become pilots, electricians and commercial drivers.

How colour vision deficiency affects children 

Activities at school that are colour coded are difficult for children with colour vision problems as they would struggle recognising, identifying and separating things by colour.

Colour vision deficiency is quite common and has minimal impact on a child’s long-term health. 

There is generally no treatment and people with colour vision deficiency find they have few limitations. Often people don’t suspect or discover they have a problem until they are adults. Adjustments such as taking cues from others or using visual cues that don’t rely on colour, are some of the ways to adjust.

It is recommended that all children (especially boys) have a colour vision assessment. Colour vision testing can be done by optometrists, using specially designed charts. If a deficiency is found, further testing may be required to identify the exact deficiency.