Colour plays a significant part in our daily lives. Though around 8 per cent of men and 0.5 per cent of women experiencing red-green colour vision deficiency, so for them, life may often be not so straightforward.
Though it is noted that red-green colour deficiency affects around 1 in 12 men of Northern European heritage. This group includes those with any mutations in the red photoreceptor gene (causing protanopia) or the green one (causing deuteranopia). According to Wikipedia, 9.2% of Russian males, 9% of Norwegian males, 8.6% of French males
Africans are much less likely to be colour blind with 2.9% of Hutu males, 2.5% of Tutsi males, 2% of Tswana males, 1.7% of Congolese males.
Prevalence among Eastern Asians is somewhere between Europeans and Africans with 6.9% of Chinese males, 4% of Japanese males, 5.9% of Korean males
Fijians are the least colour blind people with 0.8% of Fijian males.
It is suspected that colour vision deficiency is more common among Europeans due to early migration. Evolution can be random sometimes and not all changes over time or differences between populations are the result of natural selection. Genetic drift can fixate alleles in small populations by pure chance if they are not seriously deleterious. demographic events, like a population bottleneck or a founder effect, can intensify genetic drift. A lot of genetic differences may be explained not by natural selection on this scenario, but by genetic drift, it is estimated there are over 250 million colour blind people around the world.
Colour deficiency, is caused by genetic mutations or damage to cells at the back of the eye. These cells are responsible for colour vision.
Most individuals who are colour vision deficient are unable to see one of the three colours that the human eye can distinguish: blue, green, and red.
In fact, no two people perceive a particular colour in the same way. That’s because colour vision is a complex interplay between photoreceptors, the optic nerve, and the brain. That is why we stock several types of iRo lenses so we can find the correct lens for your vision.
The cells responsible for colour vision are called cone cells and sit at the back of the eye, in the retina. Each cone cell has one type of colour photoreceptor that can pick up blue, green, or red light.
When light enters the eye, the photoreceptors on the cone cells are stimulated and pass messages to the brain via the optic nerve. The combination of input from all three photoreceptors allows us to see complex colours.
The reason why colour vision deficiency mostly affects men because the genes that are responsible for the green and red photoreceptors are located on the X chromosome.
A man who has inherited one mutated copy of one of these genes will, therefore, be colour-blind, as men only have one X chromosome. But women have two copies of this chromosome, and the chance of inheriting a non-mutated photoreceptor gene is subsequently greater.