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Updated on: Thursday, May 30, 2019, 03:40 AM IST

One in twelve men suffers from colour blindness, say doctors

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Mumbai: Around one in twelve men suffer from colour blindness. So, what is colour blindness? Most of us share a common colour vision sensory experience. Some people, however, have a colour vision deficiency, which means their perception of colours is different from what most of us see. The most severe forms of these deficiencies are referred to as colour blindness.

Colour blindness is a usually a genetic (hereditary) condition (you are born with it). Red/green and blue colour blindness is usually passed down from your parents. The gene which is responsible for the condition is carried on the X chromosome and this is the reason why many more men are affected than women.

Doctors say that 8 per cent of the male population and 4.5 per cent of the population of the UK as a whole is colour blind and there are estimated to be over 250 million colour blind people worldwide. “The vast majority of people with a colour vision deficiency have inherited their condition from their mother, who is normally a ‘carrier’ but not colour blind herself. Some people also acquire the condition as a result of long-standing diseases such as diabetes, multiple sclerosis, some liver diseases and almost all eye diseases,” said Dr Rohit Chhatbar.

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People with this condition are neither blind nor are they able to distinguish any colours. On the contrary, they have absolutely normal eyesight with the inability to perceive equally all the colours of the visible spectrum. “They disqualify from being employed by government of India’s maritime services, aviation services, forest department, railway services and a lot more on the grounds of disability,” said Dr. KK Goyal

The most common form of colour blindness is known as red/green colour blindness and most colour blind people suffer from this. Although known as red/green colour blindness this does not mean sufferers mix up red and green, it means they mix up all colours which have some red or green as part of the whole colour. For example, a red/green colour blind person will confuse a blue and a purple because they can’t ‘see’ the red element of the colour purple. See the example of pink, purple and blue pen cases below to understand this effect.

“Most colour blind people are able to see things as clearly as other people but they are unable to fully ‘see’ red, green or blue light. There are different types of colour blindness and there are extremely rare cases where people are unable to see any colour at all,” added Dr. Chhatbar.

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The effects of colour vision deficiency can be mild, moderate or severe depending upon the defect. If you have inherited colour blindness your condition will stay the same throughout your life it won’t get any better or worse. “Approximately 40 per cent of colour blind pupils currently leaving secondary school are unaware that they are colour blind , whilst 60 per cent of sufferers experience many problems in everyday life,” said Dr. Dheeraj Jain.

The retina of the eye has two types of light-sensitive cells called rods and cones. Both are found in the retina which is the layer at the back of your eye which processes images. Rods work in low light conditions to help night vision, but cones work in daylight and are responsible for colour discrimination.

There are three types of cone cells and each type has a different sensitivity to light wavelengths. One type of cone perceives blue light, another perceives green and the third perceives red. When you look at an object, light enters your eye and stimulates the cone cells. Your brain then interprets the signals from the cones cells so that you can see the colour of the object. The red, green and blue cones all work together allowing you to see the whole spectrum of colours. For example, when the red and blue cones are simulated in a certain way you will see the colour purple.

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The doctors said that the exact physical causes of colour blindness are still being researched but it is believed that colour blindness is usually caused by faulty cones but sometimes by a fault in the pathway from the cone to the brain. “There is no cure for colour blindness. However, there is an on-going research to identify and developed techniques in such a way that they help the entire visual apparatus, viz., the lens, cone cells, ciliary muscles, retina and the optic nerve, to help it correct itself so as to treat the specific ailment which improves visual acuity,” added Dr. Goyal.

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Published on: Monday, September 11, 2017, 07:35 AM IST
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