My Deuteranomalous Life

I was diagnosed with red-green colour deficiency at about the age of eight. During a routine eye check at a Boots opticians, the optician produced a mesmerising book consisting of pages and pages of coloured slides, each of which was made up of a circle composed of randomnly sized and arranged dots of slightly different colours. (Later to become known to me as the Ishihara Test). The optician merely asked me to say what I saw. It rapidly became obvious that the test was exposing some hitherto silent trait within me as each slide was passed before me, eliciting little more than "erm...some more coloured dots?" My dad gradually became more and more animated during the encounter, exclaiming his surprise that I couldn't see the blindingly obvious numbers contained within the dot-mosaics. He was eventually asked to leave the room by the optician! My red-green colour defiency was sold to me as better than being colour blind.


Deuteranomoly is the most common (and mildest) form of colour blindness (or to use the correct term, congenital colour vision deficiency), affecting 5-6% of the male population.

The cause of the disproportionately-high numbers of males affected is that the most common form - red-green colour blindness - is an 'X-chromosome sex-linked recessive' disorder. The 'recessive' part means that a person must carry two copies of the defective gene to develop the condition. 'X-linked' means that the gene is on the X-chromosome. Women have two copies of the X-chromosome, and so they may have normal colour vision, even if they carry one copy of the defective gene. Men only have one X-chromosome, and so will be colour blind with only one defective copy of the gene. Men inherit the X-chromosome from their mother, so a woman with one copy of the defective gene (and therefore normal colour vision) can still pass colour-blindness to her sons - she is a 'carrier'.

Click here to see the world through my eyes and here to see some professional implications. (Don't worry - I can tell that blood and the top traffic light are red).

On the plus side:

Colour blind people have a tendency to better night vision and an ability to be able to distinguish hues that remain unseen to those who do not have the disorder. In males, this may result in improved hunting skills in low light levels.