Investigating colour vision

For people possessing defective colour vision some colours such as red and green may appear identical. Lacking any objective standard, people with defective colour vision can easily go through life without being aware of their difficulty.

It is important that some attempts are made to test for defective colour vision in school children. Potential problems exist in a great many jobs: train drivers, pilots, doctors, nurses, farmers, dressmakers, dyers and colourists, and many more. A high price may have to be paid for mistakes in colour identification: a day's production of colour-coded electrical components lost; a crop of tomatoes picked too early; the wrong coloured yarn used to weave a carpet.

Defective colour vision

Defective colour vision affects over two million people in the UK. The inheritance of colour defects is linked to gender and one in twelve men are affected but only one in 200 women. It is more common in men because the genes which can cause defective colour vision are held in the X chromosome. Since women have two X chromosomes and men only one, women are less likely to suffer from impaired colour vision as it is very rare for both X chromosomes to be faulty. However they can carry the defect and pass it on to their children.