Color vision deficiency


What is colour deficiency ?
Colour deficiency occurs when your ability to distinguish colours and shades is less than normal. The term "colour blind" is often used, but usually incorrectly. Only a very small number of people are completely unable to identify any colours. Colour deficiency is more common in males than females. 

What causes colour deficiency ?
Colour deficiency is usually inherited, but can also result from certain diseases, trauma or as a side effect of certain medications. It happens when an individual partially or completely lacks one or more types of the three kinds of cones. 

What types of colour deficiency exist ?
There are three: two different kinds of red-green deficiency and one blue-yellow deficiency. The red-green deficiencies are by far the most common and result in the inability to distinguish between certain shades of red and green. Blue-yellow deficiency is very rare and results in the inability to distinguish between certain shades of blue and yellow. In very rare cases, colour deficiency exists to an extent that no colours can be detected. This person sees all things in shades of black, white and grey. 

How is colour deficiency detected ?
People who are colour deficient are generally unaware of their condition. They assume that everyone sees things the way they do. As a result, a complete optometric examination, including a test for colour vision, is recommended. The test for colour deficiency is a relatively simple one, typically involving the viewing of a series of coloured designs. The designs have been created in such a way that a person with normal colour vision can see certain figures in the designs. A colour deficient person will not be able to distinguish the figures. 

When should a person be tested for colour deficiency ?
Every child should be checked for colour deficiency by at least age five. It is important to detect colour deficiency early because colour coded learning materials are used extensively in the primary grades. In addition, colour deficiency may affect the career path of an individual, since the ability to distinguish colours is an important aspect of some jobs, such as pilots, electricians, some military personnel, police officers and others. 

Can colour deficiency be cured ?
Unfortunately a cure for colour deficiency has not yet been discovered. A person with colour deficiency can, however, be taught to adapt to the inability to distinguish colours. For example, you can be taught to recognize the brightness and location of a traffic light rather than the colour itself. It is sometimes possible to increase the ability to distinguish colours with the use of special filters. A special red tinted contact lens, used in one eye, and other devices are used, in some cases, to aid persons with certain colour deficiencies.