What is Colour Vision Deficiency ?
Colour vision deficiency is the inability to distinguish certain shades of colour or in more severe cases, do not see colors at all. The term “colour blindness” is also used to describe this visual condition, but very few people are completely colour blind.
Most people with colour vision deficiency can see colours, but they have difficulty differentiating between particular shades of reds and greens (most common) or blues and yellows (less common).
The pigments inside the cones register differing colours and send information through the optic nerve to the brain enabling you to distinguish countless shades of colour. But if the cones lack one or more light sensitive pigments, you will be unable to see one or more of the three primary colours thereby causing a deficiency in your color perception.
The most common form of colour deficiency is red-green. This does not mean that people with this deficiency cannot see these colors at all, they simply have a harder time differentiating between them. The difficulty they have in correctly identifying them depends on how dark or light the colours are.
Another form of colour deficiency is blue-yellow. This is a rarer and more severe form of colour vision loss than red-green since persons with blue-yellow deficiency frequently have red-green blindness too. In both cases, it is common for people with colour vision deficiency to see neutral or gray areas where a particular colour should appear.
What causes colour vision deficiency?
Usually, colour deficiency is an inherited condition caused by a common X-linked recessive gene, which is passed from a mother to her son. But disease or injury damaging the optic nerve or retina can also result in loss of color recognition. Some specific diseases that can cause color deficits are:
Other causes for colour deficiency may be due to medications (certain medications such as drugs used to treat heart problems, high blood pressure, infections, nervous disorders and psychological problems can affect colour vision) ageing, or chemical exposure.
In the majority of cases, genetics is the predominate cause for colour deficiency, women are typically just carriers of the colour deficient gene, though approximately 0.5% of women have colour vision deficiency. When the deficiency is hereditary, the severity generally remains constant throughout life. Inherited colour vision deficiency does not lead to additional vision loss or blindness.
How is colour deficiency diagnosed?
Colour deficiency can be diagnosed through a comprehensive eye examination. Testing will include the use of a series of specially designed pictures composed of coloured dots, called pseudisochromatic plates (Ishihara), which include hidden numbers or embedded figures that can only be correctly seen by persons with normal colour vision and the Farnsworth Panel D-15 Test (a more comprehensive colour vision examination) to identify all colours.
How is colour vision deficiency treated?
There is no cure for inherited colour deficiency. But if the cause is an illness or eye injury, treating these conditions may improve colour vision. Though colour vision deficiency can be a frustration and may limit participation in some occupations, in most cases it is not a serious threat to vision and can be adapted to your lifestyle with time, patience and practice.
Colour Vision Deficiency and Careers
Colours are frequently used to mark differences between objects in everyday life. Certain jobs or careers require some degree of color identification. Some of these careers are listed below. They are grouped according to how important colour vision is in the nature of the job. In addition, there are different activities within a listed industry and there may be jobs within the industry that do not require full colour vision.
List 1 –Occupations/Activities requiring perfect colour vision
- Air force (certain grade)
- Navy (certain grade)
- Army (certain grade)
- Civil aviation
- Police (certain grade)
List 2- Occupations/Activities where defective colour vision may be an asset
List 3- Careers/Jobs where defective colour vision is a handicap and important consequences might result from errors of colour judgement
- Air traffic controller
- Car body re sprayer / retouch
- Chemists and chemicals
- Forensic scientist
- Meat inspector
List 4 – Careers/Jobs where good colour vision is desirable, but a defective colour vision would not necessarily cause a handicap