Question: Do you know how colour blindness is caused?

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  1. There are different types of colour blindness, but in most cases people have problems seeing the colours blue, red, green or a mix of these colours. Red-green colourblindness appears to be the most common. It is actually quite rare for someone to be completely colour blind. Sometimes people just won’t see the colour in question or it will appear a different colour. The condition of colourblindness relates to the photoreceptor cells in your eyes, which are called cone cells.

    In your eyes there are three types of cone cells – each type senses either blue, red or green light. Cone cells are found in the macula which is part of the retina. Colourblindness occurs when someone is missing one or more of these types of cone cells or the cone cells don’t function properly.

    Often the cause is genetic, and someone will be inherit the mutations that affect the cone cells from their parents, and they will be colourblind for life. However, sometimes colourblindness can be acquired due to aging, disease, degeneration or injury.

    The genetic mutations associated with inherited colour blindness are mostly found on the X chromosome as this is where the genes for the red/green colour receptors are found, however many other causative mutations found on other chromosomes have been discovered. The condition is sex-linked and recessive, meaning that the condition will only be seen if only the mutation is present (if there is also a copy of the gene that is normal it won’t cause disease) . Up to 8% of males are born colourblind, but only 0.5% of females are – this is because males only inherit one X chromosome (the other being a Y chromosome) and thus will exhibit any colour-blind mutations associated with that single X chromosome. As females have two X chromosomes if only one X chromosome with has the mutation and one does not, the female won’t be affected by colourblindness due to recessive nature of the condition, and only females who have both copies of the X chromosome with the mutation causing colourblindness will actually be colourblind.