Colour blindness is a condition where a person cannot figure out the difference between certain colours. This happens because he/she may be born without certain colour 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.
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 them perform their main function of helping us see colours. These pigments have a different wavelength which, when activated, helps us perceive 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.
The prevalence of colour blindness is more in boys compared to girls. It has been reported that 8% of men are colour blind in this world, while only 0.5% of women suffer from this disorder.
Girls are mainly the carriers of this disorder and pass it to their offsprings. A girl child will be affected with colour blindness only if her father is colour blind and her mother is a carrier.
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.
1. Monochromatism: In this condition, the person can only perceive one type of colour. This means that only one type of cone is present in the eye. It is also known as achromatopsia, and this condition is uncommon. People with this condition can only see various shades of grey.
2. 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.
3. Anomalous trichromatism: 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. People with this vision are usually known as anomalous trichromats. Namely, there are three different types of anomalous conditions; protanomaly, deuteranomaly and tritanomaly. People with protanomaly have decreased sensitivity to red light. In deuteranomaly, which is the most common type of colour blindness, there is reduced sensitivity to green light. Reduced sensitivity to blue light is known as tritanomaly, and it is very rare.
Causes
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.
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.
Damage to the brain or eye can also cause colour blindness. Medications that harm the eye can also lead to this eye disorder.
Risk Factors
The following are some of the risk factors for colour blindness:
The common symptoms of colour-blindness are -
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.
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 color-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 pediatric version of this test has also been made, mainly for children who cannot read numbers. Children can be tested for colour blindness when they reach four years of age as, by then, they will be mature enough to answer questions about what they can or cannot see.
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.
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.
Other aids that can help a person with colour blindness, such as:
In the case of acquired colour blindness, identifying the cause can help treat the condition. If the colour blindness has occurred as a side effect of any medication, the doctor may suggest replacing the drug with some other alternatives or discontinuing it. This step may help in reversing the condition.
Driving for someone who is colour-blind could be downright 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.
Colour blindness is a life long disorder, and so far, there is no cure for it. However, it is not a severe condition, and the affected person can carry on daily activities without many difficulties.
Colour blindness can pose a problem when choosing careers that require a normal vision, such as a career as a pilot, fashion designer, painter, electrician etc.
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Can colour blind students be allowed to pursue medical courses?
Colour-blindness: What you need to know
Suffering from diabetes, hypertension or colour blindness? Here is why you might have inherited those diseases.
No more blindness - Blindness control mission close to success
