Causes of Colour Blindness


Light passes through the eye lens and then through the vitreous body to the cone cells in the retina of the eye.  These cones distinguish differences in colour and relay this information to the brain.  Hundreds of colours can be distinguished.  If certain light sensitive chemicals are not present in the cone cells, then all three primary colours (red, blue and green) cannot be distinguished and a colour may be seen as grey.  Red and green colour deficiency is the most common and usually means that there is a degree of deficiency instead of complete deficiency of colour depending on the amount of light-sensitive substances that are missing.  Some people with such a deficiency are not even aware of it because it is only mild.

Usually colour blindness is inherited and doesn’t change with age.  It is caused by an X-linked recessive gene and males can inherit the gene from a colour deficient mother or a mother who has normal colour vision but carries the gene.  Fathers with the gene cannot pass it directly to their children, but daughters are always carriers of the gene and will be colour blind if their mother also has the gene.

Colour blindness may also occur with age or disease where retinal cells are damaged.  In extreme cases almost total colour blindness occurs.  Disease related colour blindness usually affects the perception of blue and yellow.  One eye may show more symptoms than the other and symptoms may lessen as the disease becomes resolved.  Such diseases include Diabetes, Glaucoma, Macular Degeneration, Alzheimer's, Parkinson's disease and Leukaemia. 

Certain medications have also been known to cause a colour deficiency.  Certain chemicals have also been reported to affect colour vision such as certain fertilisers.

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