Each iris is unique: it is almost impossible to find two people who have identical eyes! The coloured part of the eye protects the eye from the light by contracting or expanding.
This allows the iris to determine the right amount of light that enters the eye. For example, when it is sunny, the iris contracts, and the pupil becomes smaller. But where does the colour of the iris come from?
Melanin
The colour of the eyes is first determined by the amount of melanin found inside of them.
If you have brown eyes, you have a gene that allows the accumulation of pigments in the same place, which in this case, is located in the front part of your iris.
Blue-eyed people, on the other hand, have little melanin in this section of the iris. Their eyes look blue because of the way the light is scattered. Thus, the blue component of the light is spread in the iris while the other colours are absorbed. The iris seems blue because this colour is more reflective compared to others. As for brown eyes, they reflect less light. They contain more melanin, which explains their colour.
If you have blue or green eyes, you are lucky: they are the rarest colours! However, your eyes let in more light than brown eyes and are probably more sensitive to light. So you need to protect them to keep them healthy.
Your eyes may even be different colors!
Heredity
Sixteen types of genes determine eye colour. It is inherited from a major gene, which makes it possible to predict that two parents with brown eyes are likely to have a child with brown eyes.
The child who is born carries two genes that determine eye colour, one from the father and the other from the mother. There are dominant genes and other recessive ones. The brown eye gene is dominant, and it outweighs the blue eye gene. This explains why a blue-eyed mother and a brown-eyed father are likely to have a brown-eyed child.
But what happens if a child has blue eyes and his parents both have brown eyes? The child inherited two blue genes; although neither parent had blue eyes, it was still part of their DNA. Blue eyes can skip a generation. In other words, this child’s grandparents’ eyes were probably blue. Other genes are involved in the transmission of eye colour, which explains, in particular, the green eye colour, which is created by a variant on a gene.
By the way, people with blue eyes would all come from the same ancestor, according to a Danish study. This eye colour would have been affected by a genetic mutation transmitted to his descendants a few thousand years ago. This ancestor came from Europe, which explains why there are blue-eyed people on this continent, while they are much rarer in Asia and Africa.
Can blue eyes disappear one day?
Since the blue-eye gene is recessive over that of brown eyes, which is dominant, it could lead us to believe that blue eyes will cease to exist one day. However, this is not the case, according to the researchers. The proportion of blue-eyed people in Europe remains stable because recessive genes still continue to be transmitted from one generation to the next.
To learn more about eye colour and the best way to protect them from the sun, talk to your optometrist during your next visit to your local IRIS store!
