A person with ‘normal’ colour vision sees approximately six bands of colour (red,orange, yellow, green, blue and violet). A person with colour deficiency will possibly only see four colour bands (yellow-orange, grey, blue and violet).

Distinguishing pastel colours may prove difficult for someone with colour deficiency. Blue-green and red-purple shades can be confused with grey, while yellow, brown and green may also be confused for each other.

What does someone with colour deficiency see?
People with a disturbance in their colour vision may find it difficult to describe different colours accurately. This is because some colours appear grey or almost colour-less while others are easily confused. As you can imagine, this could be frustrating, difficult and potentially dangerous.

Are there differences in the severity of colour deficiency?
Yes, colour deficiency affects people to different degrees. In an extreme form, someone with colour deficiency may only see three colours of the rainbow and grey. Alternatively, a mild expression may result in minor alterations in colour vision. In such cases, only diluted colours may prove troublesome.

How does colour deficiency develop?
Colour deficiency is either ‘inherited’ or ‘acquired’. A person who inherits colour deficiency is more likely to be male than female. Approximately 8% of males experience some form of colour deficiency while only 0.4% of females are colour deficient. Colour deficiency can be acquired as a result of disease, injury or natural aging processes. In some cases it can be an early sign or symptom of eye disease.

Colour deficiency can also be acquired through the use of various drugs (medicinal and illicit), alcohol and the fumes of some chemicals.

How can colour deficiency affect my life?
There are many, often subtle ways colour deficiency can impact on an individuals’ life. School children who experience colour deficiency may have difficulty seeing coloured chalk on a blackboard; frustrations may arise when trying to determining differences between bank notes, and some research indicates motorists who have red perception difficulties may have an increased chance of nose to tail collisions due to their reduced ability to pick up red brake-lights.

Career choices may also be affected. The Armed Forces and Police generally require normal colour vision in all recruits. Of the 8% of men affected by colour deficiency, 6% have a green perception difficulty (deutan detect) and 2% have a red perception difficulty (protan defect). Less than 0.5% of men have a severe red perception difficulty (protanopia).

© 2005 Medica Consulting Limited.