Colour Blindness

Chanté Roets - B.Optom (UOFS) CAS(SA)

What is colour blindness?

Colour blindness affects approximately 1 in 12 men (8%) and 1 in 200 women in the world. Worldwide, there are approximately 300 million people with colour blindness.

There are different causes of colour blindness. For the majority of people with deficient colour vision the condition is genetic and has been inherited from their mother, although some people become colour blind as a result of other diseases such as diabetes and optic nerve diseases or they acquire the condition over time due to the aging process, medication etc.

Colour blindness is an often misunderstood condition. Many assume because of its name that “colour blind” means a person can only see in black and white. In reality, the vast majority of people with colour blindness do see colour, but they see a much narrower range of colour. They are unable to fully “see” red, green or blue. 

Types of colour blindness: 

  • Trichromacy - Normal colour vision uses all three types of light cones correctly and is known as trichromacy. People with normal colour vision are known as trichromats.

  • Anomalous Trichromacy - People with ‘faulty’ trichromatic vision will be colour blind to some extent and are known as anomalous trichromats. In people with this condition all of their three cone types are used to perceive light colours but one type of cone perceives light slightly out of alignment. There are 3 types of anomalous trichromacy.

a. Protanomaly, which is a reduced sensitivity to red light.

b. Deuteranomaly which is a reduced sensitivity to green light and is the most common form of colour blindness.

c. Tritanomaly which is a reduced sensitivity to blue light and is extremely rare.

  • Monochromacy - People with monochromatic vision; also called achromatopsia, can see no colour at all and their world consists of different shades of grey ranging from black to white. Achromatopsia is very rare.

Treatment for colour blindness:

There is currently no treatment for colour blindness. Some colour blind people have found  coloured filters that works for them and some lenses might help them to distinguish between some colour combinations in certain situations, whilst others report no effect or that these coloured filters can even cause further confusion.