Why are some people colour blind?

eyePeople are colour blind because of a condition they got when they were born. We see colours because of millions of little receptors in our eyes called ‘cones’. The cones sort out all of the light that is coming into our eyes, and depending on what energy  the light is, tells our brain what colour we are seeing as a signal it sends down our optic nerve. There are other receptors called ‘rods’, which are great at detecting black and white and help us see in dark rooms.

cones1About 8 % of men are colour blind, which means 8 in every 100 men. Colour blindness happens because some of the cone receptors, which detect the colours, are faulty. So the red-detectors don’t pick up reds very well. Most people who have it can’t see the difference between red and green. The genes (part of our DNA) that cause colour blindness occur on something called our X chromosome. rods1Men have two X chromosomes, and women
only have one, which is why men are more likely to get it.


It effects lots of things- like advertising and where people work. Graphic designers who design adverts know lots of people can’t distinguish red from green, so don’t use those colours together for adverts. If you were working for a railway company, you might have a hard time with the traffic lights!
Scientists are now making special glasses that let people with colourblindness see all of the different colours. When we can’t see between red and green, it’s because our red cones and our green cones are confusing the messages they are receiving. Just like when to radio stations overlap and we hear a messy noise or a mix of music, the two colours seem to overlap. The eye underneath is just a healthy! Using some computer models and maths, scientists have worked to make filters to block out parts of the colourful light they receive. They block out the signals that overlap the most, so that the red and green cones can do their job properly.

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