We are all capable of experiencing 200,000 or more different colour sensations. This is achieved by the existence of three different receptors in the retina (the sensory lining at the back of the eye). These receptors are called cones and each one absorbs different wavelengths of light. The three cones are red, green and blue.
The existence of colour vision deficiency has been known as far back as the ancient Greeks. Colour Vision Deficiency occurs when one or more of these cone receptors is either not functioning at all or functioning below its maximum capacity. This most commonly affects the red/green cones in both eyes. Usually one in eight males are affected and one in 200 females. These colour deficiencies are permanent and cannot be corrected. The cause of the problem is hereditary with the responsible gene being carried on the X chromosome.
Colour Vision Deficiency can also be acquired through ocular disease such as Cataract, Diabetic Eye Disease and Macular Degeneration. However these patients will usually experience the problem in one eye only and will have difficulty with blue and yellow colours.
The impact of having a Colour Vision Deficiency problem is usually very mild. Most people won’t notice that they are having difficulty with colours. The impact is more severe on the choice of one’s occupation. Those wishing to pursue careers in the military, aviation, police force etc, must have perfect colour vision. Failing a Colour Vision Test does not mean, however, that you are visually handicapped in any way.
A colour vision test is normally given at your first sight test especially with males. However if you feel that you have a problem distinguishing colours then you can request a test at you next sight examination.