Colour Vision Deficiency (Colour blindness)

What is colour blindness?

Colour blindness occurs when the ability to differentiate colours and shades is decreased. The term colour blind is often misused. Very few people are actually completely incapable of differentiating colours. Colour vision deficiency is more common in men than in women.

What causes it?

Colour blindness is usually hereditary, but may also stem from illness, trauma or a side-effect of certain medications. Colour blindness occurs when a fault occurs in the development of one or more of the three sets of colour sensing cones in the eye.

What types are there?

There are three types: two affect the red-green and the other, blue-yellow. Red-green colour deficiency is far from being the most common and reflects an inability to differentiate certain shades of red and green. Problems associated with seeing blue-yellow are very rare and reflects an inability to distinguish certain shades of blue and yellow. In very few cases, the inability to perceive colours is so severe that no colours are differentiated. In such cases, the person only sees their world in shades of black, white and grey.

How is colour blindness detected?

Those affected are not usually aware that they are. The simply assume everyone sees this way. For this reason, a comprehensive eye exam is recommended including a colour vision test. The test mainly involves the patient looking at a series of coloured images. A person with normal colour vision will be able to distinguish the shapes in these images.

When should one undergo an Ishihara colour test?

All children should undergo the test by age five. It is important to detect this problem early, as teaching materials in the early years of school involve a good deal of colours. Furthermore, colour blindness could affect one’s career path. Careers such as pilot, electrician, military, police officer and many others require the ability to differentiate colours.

Is colour blindness curable?

Unfortunately, there is still no known cure. However, those affected by colour blindness can compensate by learning to recognize the brightness and position of traffic lights as opposed to their colour for example. Sometimes the ability to differentiate colours can be increased with the help of specialized filters. For example, a red coloured contact lens can be worn in one eye in order to help the patient.