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Colour Blindness

Colour Blindness

“Of all God’s gifts to the sighted man, color is the holiest, the most divine, the most solemn”
-John Ruskin

What is Colour Blindness?

Colour Blindness means that you have difficulty seeing red, green or blue or a mix of these colours. A total lack of colour vision or the ability to see only shades of grey is very rare.

Approximately 8 out of 100 men and 1 out of 100 women are affected by colour blindness.


What causes colour blindness?

Normally, there are two types of cells in your eye that are sensitive to light. They are called rods and cones. Rods are responsible for vision in dim light, while cones enable you to differentiate between colours and see in detail. There are 3 types of cone cells: green, red and blue. These 3 types of cones work together and enable you to see the entire spectrum of colours. Each of these types of cones has a different level of sensitivity to light. When you look towards an object, the light rays enter your eyes and stimulate the respective cone cells. These stimuli are interpreted by your brain and thus you can ‘see’ a colour.

In colour blindness, one or more of these cone types are either missing or faulty. Eg. If your red cones are missing you will not be able to see clearly any of the colours containing red.

• In most of the cases, it is an inherited condition, especially so for red – green colour blindness. You are more likely to be born with colour blindness if you are a male. If you have inherited colour blindness, it will probably stay the same throughout your life.
• You can develop reduced colour vision because of an illness, side-effects of medications (contraceptive pills, certain medicines for rheumatoid arthritis and a few heart, nervous disorder medications), head injuries or exposure to particular chemicals.
• Diseases of the eye like glaucoma, cataract, optic nerve disease and age-related macular degeneration can also cause troubles with colour vision. Diseases like diabetes and multiple sclerosis can also be a cause.
• Exposures to industrial solvents, alcohol abuse and smoking have also been found to be contributory.
• Aging may play a significant role.

How do I know if I have Colour Blindness? (Signs and Symptoms)

The main symptom is that you will have a difficulty in differentiating certain colours or may make errors in identifying them. You may not notice much of a difference in various shades of colours.

These symptoms may be worse if:

The lighting is dim or low

The area of the colour is small

A large area of the colour is seen at a distance

You try to differentiate faint colours or darker shades

What are the tests for Colour Blindness?

The Ishihara Test is most commonly used to diagnose reed-green colour blindness. Colour plates will be held out in front of you. If you are colour blind, you may not be able to see certain information.



The Colour Assessment and Diagnosis test may be used along with the Ishihara test. Unlike the Ishihara, this can be used for both red-green and blue colour blindness. This involves you looking at coloured blocks in a grey square on a monitor. This test can give you a measure of the severity of your colour blindness.

What is the treatment for Colour Blindness?

For inherited colour blindness, there is no cure. Using coloured filters or tinted contact lenses may help improve the brightness between certain colours.
For acquired colour blindness, the original cause has to be treated.
Having Colour Blindness can affect many of your daily activities like knowing when the traffic lights have changed, rewiring an electrical plug, reading maps etc. However, you can always find ways and means to cope with it for e.g. relying on the position of the traffic lights rather than the colour.
Some professions may not be possible for you to pursue e.g. pilots, coastguards.