Colour Vision Deficiency

Everyone sees colours a little differently. But some people have difficulty distinguishing specific colours.

Causes and triggers

Colour vision deficiency involves the cells of the eye called cones. There are three types of cones and each is responsible for a colour: red, green or blue colour pigments. These are the so-called primary colours that allow us to see every other colour. If the cones that are associated with a colour are absent or not functioning properly, the affected person will have difficulty distinguishing certain colours.

Colour blindness, for the most part, is hereditary. It is inherited through the X chromosome. Men only have one X chromosome, while women have two. There are therefore more men affected than women, as women can have a second normal X chromosome that compensates for the anomaly. This hereditary form is more common in people of Caucasian origin.

The anomaly may also be caused by a reaction to medication, a disease, a damaged optical nerve or brain damage.

Symptoms

The most common form of colour vision deficiency is deuteranopia. In this case, the cones associated with the green photoreceptors are absent or not functioning properly. As a result, colours such as green, orange, brown and light red are difficult to tell apart.

There is also protanopia, which is associated with red perception disorder, and tritanopia, associated with blue perception disorder. However, they are quite uncommon.

Some people do indeed have only one cone type, while others have none at all. When there is a total absence of cones, everything is seen in black and white, a condition known as monochromacy (or achromatopsia).

Treatment

There is no treatment for colour vision deficiency. Nevertheless, those affected can live perfectly normal lives by developing tricks to determine colours. For example, a person who has difficulty differentiating green and red on traffic lights can rely on their shape or position instead (red on top, green at the bottom). Furthermore, there are mobile apps, as well as glasses and lenses, that can help to better tell the differences. These tools do not, however, allow to perceive the true colours.

Colour vision deficiency is often detected during childhood, but some people discover it later. This disorder can affect the child's comprehension and development at school. This is why it is recommended to have them evaluated by an optometrist between the ages 3 and 5. Moreover, it is good to know that people with colour vision deficiency are forbidden to hold various positions (e.g. airline pilot, electrician).