Thursday, April 25, 2013

Colour-blindness: Key facts and info

Can you imagine a world without colour? Well there are a number of Indian’s who suffer from a condition that makes it impossible to see all or some colours. With the recent news that a large number of BEST bus drivers in Mumbai have been found to be suffering from color-blindness, it’s alarming how we haven’t had many more accidents. Although colour-blindness is not an alarming condition, it is important to know about it.

According to statistics approximately 13,956 people from different regions in India, suffer from colour-blindness. This number is fairly low compared to nations such as Japan, Great Britain or France.

What is colour blindness?

It is a condition where a person cannot figure out the difference between certain colours. This happens because he/she may be born without certain color sensitive pigments in their eyes. These pigments are usually present in the cones of the eye, which are present at the back of the eyeball.

Who does it affect?

Colour-blindness is a hereditary condition that affects mostly the male population. The gene that causes colour-blindness is present on the X chromosome. Since women have two X chromosomes and men have only one, they are more likely to suffer from the condition.

How does it happen?

Eye-anatomy. The eye has a number of components, and one of the most important parts of the eye is the retina. The retina is placed at the back of the eyeball and is packed with nerve endings that carry impulses to the brain along with two types of photoreceptor cells, called the rods and cones. The rods are mainly responsible for perceiving the presence of light and are placed on the outer edge of the retina. The central part is filled with cones. Cones have a number of pigments that help it perform its main function of helping us see colours. These pigments have a different wavelength which when activated helps us perceive a colour.The three main colours that these pigments are sensitive to are– green, blue and red . In the case of colour-blind people, because of the deficiency of certain pigments, they are unable to see these colours. For example what we may see as red, they may see as light green or grey, depending on the type of colour blindness they are suffering from.

Types of colour blindness:

There are mainly three types of colour blindness, the most common type is red-green colour- blindness. People who suffer from this can most often not see green, red and blue.

Monochromatism: In this condition the person can only perceive one type of color. This means that only one type of cone is present in the eye.
Dichromatism: Here the person can see only two colours. Therefore he would have only two types of cones, the third variant would be completely missing.
Anomalous trichomatism: In this condition where the person has all three types of cones but they either malfunctioning or are less in number. People with this kind of colour blindness usually can see a smaller spectrum of colours.

Can a person become colour-blind later in life?

Although colour-blindness is usually an inherited disease, there are certain conditions of the eye that could lead to colour-blindness. Conditions such as cataract can lead to ‘acquired colour-blindness’. Usually a person’s vision comes back to normal once the condition has been reversed with surgery.

Symptoms of colour-blindness:

The most glaring symptom of colour-blindness is the inability to see certain colours. For instance you might be able to see red and green but might not be able to see colours like blue and yellow.
You might be able to see only a few shades of a colour, while most people can see a large variety of colours.
In rare cases you might be able to see only black, white and grey.

Diagnosis of colour-blindness

Since colour-blindness affects a person from childhood , they usually don’t know that they suffer from the condition. In children it is particularly more difficult to diagnose the condition because they learn the colors of objects and apply the same technique when they are given a test for colour-blindness. There are variations to the two main tests used to diagnose the condition.

Ishihara Test: This is the most common test used to diagnose colour-blindness. It involves using a set of cards that have circles of various colours on them. Each circle is made up of a number of coloured dots. A colour-blind person would not be able to figure out the number in the center. A peadiatric version of this test has also been made, mainly for children who cannot read numbers.

Ishihara_plates

Lantern test: This is a test used for people who are either working with or seeking a job in sectors where they have to drive or operate heavy machinery etc. It is usually prescribed to those people who will require the ability to accurately identify colours of lights etc for safety reasons.

Treatment options for colour-blind people

There is currently no treatment available for colour-blindness, but there are measures that can help people with the condition. One innovation in this field is the production of ‘light filtering lenses’. These lenses are made so that a person suffering from the condition is able to see all colours. The lenses help filter the colour of light they cannot see, thereby helping them see all colours. Although in the preliminary stages, this is not widely available.

Driving and colour-blindness:

Driving for someone who is coulour-blind could be down right dangerous. As a driver it is not only important that you are able to differentiate between the different colours in a traffic light, you also have to be able to see the colours of the lights of the vehicle in front of you.For example, a vehicle that is stopping will flash a red light and if the driver is reversing he will flash a yellow light. Not being able to differentiate colours could be life threatening.

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