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What is Colour-Blindness?

16th April, 2015  


What is Colour-Blindness?


People often find themselves confused when they hear the phrase ‘colour blind’. The Eye Blog has decided to educate you about colour-blindness by asking; what is it, how can you tell whether you have it and can you treat it?


Colour-blind, a definition


The term ‘colour-blind’ is thrown around a lot. We use it in a variety of contexts. Sometimes we find ourselves wishing that society was colour-blind; that people didn’t discriminate by race. Others, we find ourselves lamenting our best friend’s colour-blind wardrobe; we’re insulting their fashion sense. However, sometimes we use the phrase ‘colour-blind’ literally; we use it to describe a condition which affects sight.


When we use it in this context, according to the NHS, we’re saying that the person in question is unable to see some colours clearly or accurately. In many cases, people who are colour-blind can’t differentiate between colours and/or shades. Society deems them colour-blind, but the more accurate term is colour vision deficient; truly colour-blind people can’t see any colour at all and it’s a very rare condition.


Types of colour-blindness


What we colloquially call colour-blindness isn’t a one-fits-all kind of eye condition. There are three types of colour-blindness, two separate conditions that result in a red-green colour deficiency and one that results in a blue-yellow colour deficiency. There are four subdivisions in the red-green category.


– Deuteranopia: Where someone confuses colours in the red-yellow-green spectrum, caused by a lack of M-cones (more about that later).

– Deuteranomaly:Where someone confuses shades of the same colour in the red-yellow-green spectrum, caused by a lack of M-cones (more about that later). For example, they may see jade-green as emerald-green.

– Protanopia: Where someone confuses colours in the red-yellow-green spectrum, caused by a lack of L-cones (more about that later). People in this condition confuse red with darker colours.

– Protanomaly: Where someone confuses shades of the same colour in the red-yellow-green spectrum, caused by a lack of L-cones (more about that later). Like, Protanopia, people are likely to see red as darker than it is. So if someone in this category was looking at something that was rose-red, they may see it as scarlet-red.


Red-green colour deficiency is the more common form of colour-blindness, yet there is another form that causes a blue-yellow colour deficiency. This rare condition makes it hard for somebody to distinguish between shades of blue and green and is caused by a lack of S-cones (more about that below).


What causes colour-blindness?


Now you know what colour-blindness is, how can you determine whether you have it? To answer this question we need to look at what causes the condition.


We won’t get too scientific. Basically colour-blindness is caused by an abnormality of the retina, the part of the eye that converts light energy into signals that the optic nerve then carries to the brain to create an image. The retina is made up of long-wavelength (L), middle-wavelength (M) and short-wavelength (S) cone cells.


Colour-blindness is caused by a deficiency of one or more of these cones. For example, Deuteranopia and Deuteranomaly are caused by a lack of M-cones, Protanopia and Protanomaly are caused by a lack of L-cones and blue-yellow colour deficiency is caused by a lack of S-cones.


How to diagnose colour-blindness


This means that in most cases, colour-blindness is genetic. It can be diagnosed in childhood. It’s also important to note, however, that you can become colour-blind due to the side-effects of any medicine you’re taking or as a result of a pre-existing eye condition.


How do you diagnose colour-blindness in childhood? Simple. You observe your child. As they grow up they may find it hard to identify colours or struggle to comprehend a document or map that uses colour extensively. You need to diagnose colour-blindness in your child as early as you can. If your child’s condition can be diagnosed and brought to the attention of their teachers early, they can be taught to compensate for their inability to differentiate certain colours and shades.


As this suggests, it’s harder to diagnose the condition in adults. This is because colour-blindness becomes entrenched; a normal part of everyday life. If you think you may be colour-blind, here’s the best way to diagnose it. Ask a friend to do for you what you would do for your child. Ask them if they see the same colour you do. If they don’t, you may be colour-blind.


Can you treat colour-blindness?


If you think you or your child may be colour-blind, you need to go to your optician for an official diagnosis. It’s important to remember that opticians won’t include a colour vision test in the standard eye test. You’ll need to request it.


If you have the condition, can you cure it? No. Not if you’re born colour-blind. This is because at the moment it’s impossible to repair or replace the cones which cause the condition in the retina. However it isn’t a serious condition; it won’t affect your health, so you can live with it and take steps to compensate for your lack of ability to see the same colours as everybody else.


We should note that it’s possible to treat colour-blindness if it has been caused by medication or a pre-existing condition. If it’s been caused by medication, consult with your GP and/or optician to find a replacement medication. If it’s been caused by a pre-existing eye condition, treat the condition and it should disappear.


What does this mean for your sight?


Therefore colour-blindness, or more accurately colour vision deficiency, is a condition which makes it harder to see certain colours. It can be diagnosed but in most cases it can’t be treated. The only way you can overcome colour-blindness is to learn to adapt to the condition and compensate for it.


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