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Colour blindness

colour blindness; vision; eyes; sight; colour; color; pupil; retina; green; red;

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People who are colour blind are not blind – they can see very clearly - but they cannot see some colours the way other people see them.

How your eyes see colour

  • colour blindnessLight from the sun or from a light bulb bounces off everything that your eyes see and goes through the pupil (the black hole in the centre of the front of your eye).
  • The light reaches the retina at the back of your eye.
  • In the retina there are millions of cells called rod cells and cone cells – these are the nerve cells which 'see' the light.
  • Rod cells are very sensitive to light, and they can react to even very faint light, such as the light from a star in a hazy night sky, but they do not 'see' different colours. Our rod cells allow us to see things around us at night, but only in shades of black, grey and white.
  • Cone cells react to brighter light and they help us to see the detail in objects. They also pick up colours. Different types of cones in the retina see different colours – there are three types of cone cells, for seeing red, green or blue light. By combining the messages from each set of cone cells, we get the wide range of colours that we can normally see.

What is colour blindness?

Sometimes a person may not have some types of cone cells. This means that some people cannot see some colours.

  • colour blindnessSome people may be unable to see the colours green and red – this is the most common type of colour blindness. They might see red as orange and green as white.
  • A few people have cones missing which cause them to be unable to see blue and yellow.
  • A very few people are unable to see any colours at all. They see the world as if it were an old black and white movie.

How do you get colour blindness?

  • Defective colour vision, as it is called by doctors and scientists, is something which is passed on in the genes. That means that a person gets it from his parents, and they got it from their parents.
  • Most of the people with colour blindness are male – about 1 boy in 10 will be colour blind, while only about 1 girl in 200 will be colour blind.
  • colour blindnessThe gene for colour vision is on the X chromosome. Females have two X chromosomes and will only be colour blind if both those chromosomes are affected. Males have only one X chromosome, so they only need that chromosome to be affected – that's why colour blindness is more common in males.
  • Because they are colour blind from birth, most people do not know they are colour blind. They don't know that other people see things differently.
  • They might know that some people say a ball is orange, when it looks to them exactly like the ball that people say is red – this can be very confusing for the person.
  • They might think that they are dumb when they are told off for putting green things in the same pile as red things, or they might think other people must be dumb if they can't see that the things are all the same colour.

How can you tell if you are colour blind?

If you have always seen the world without some colours, then it could be hard to know.

  • Maybe you get mixed up with the names of colours.
  • Maybe it is hard to tell the difference between some pale colours. Maybe a lot of the world looks black and grey and white to you.
  • If you are not sure, ask your parent or carer to get your colour vision checked. This could be done by an optitian (optometrist) or some doctors can do the test.
  • There are some colour vision tests on the internet. They are not as good as ones that are printed on paper.

colour blindness

Helping your friend

  • Being colour blind is not having a disease.
  • It is not something that makes a person less clever than someone else.
  • It is not something to tease someone about.
  • Read what some kids have to say about being colour blind and maybe you can understand it a bit better.

Using colours

Nowadays kids have their own websites, make their own power point presentations and use lots of graphics in their work.

Here are a few hints to help make your work readable for everyone, including those who have defective colour vision.

  1. Use strong bright colours like blue, white and black.colour blindness
  2. Use bold, different fonts, textures or shading instead of colour.
  3. Use a simple font that is easy to read.
  4. Don't use heaps of different colours all together as this is very hard to read. (Hard for the teacher too!)
  5. Don't use really pale colours, especially in the writing, as this is hard to read for everyone.
  6. Do not use red, green, brown, grey and purple next to each other or on top of each other. They can all look the same.

What kids say

colour blindnessMy dad is red/green colour blind. People ask really dumb questions like, "How do you know what colour the traffic lights are on?" ….as if everyone doesn't know that red is the top light and green is the bottom!" Dan

"It took me ages to learn my colours because I couldn't tell which was blue and which was yellow. My mum wrote the names on my pencils. When the teacher asked us to draw something in blue I could read the pencil." Michael

"I like my crayons because they have the names of the colour written on the paper round each crayon."

Dr Kim says:

Dr Kim"People who are colour blind do not see the world in all its colours as most of us do. Being colour blind could mean that people are not able to do some jobs, like be an electrician where different wires have different colours, in case their colour blindness puts people into danger. Some people with a certain kind of red/green colour blindness may hold an ordinary driver's licence but may not be allowed to have a licence for driving a truck, bus or some other machines.

It can be difficult for some people to wear colours which go well together, or to tell when some fruits are ripe just by looking at them."

colour blindness

 

There is more about colour blindness on the website of the 'Colour Blind Awareness and Support Group Australia' 
http://www.members.optusnet.com.au/~doverton/ 

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We've provided this information to help you to understand important things about staying healthy and happy. However, if you feel sick or unhappy, it is important to tell your mum or dad, a teacher or another grown-up.

 

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