One of the first things that we notice when we see a person are his/her eyes and in fact, eyes are amongst the primary features that attract us towards an individual. Even in case of eyes, the aspect that first comes into notice is the eye colour. Eye colour is basically a polygenic trait of an individual. It is determined by the amount and type of pigments present in the iris of the eyes.
Most Common Eye Colours
Brown
The eye colour that can be described as the most common amongst human beings is brown, with the exception of countries around the Baltic Sea. It is the result of the presence of large amounts of melanin (eumelanin) within the iris stroma. People who have very dark brown irises might give the appearance of having black eyes.
Hazel
Another common eye colour is hazel. Hazel eyes are the result of a combination of a Rayleigh scattering and a modest amount of melanin in the front border layer of the iris. Hazel eye colour has also been defined as the medium-colour between light brown and dark green. Hazel is common amongst people in America and Europe, while rare in African, Middle Eastern and Asian people.
Gray
Gray eye colour is considered to be a darker shade of blue (like blue-green). This eye colour is related to low melanin in the iris and is related to scant pigmentation throughout the body (like pale skin, light hair, etc). Gray eyes have been found to reveal small amounts of yellow and brown colour in the iris. European people, belonging to countries like Russia, Finland and the Baltic States, often have gray eyes, while those in Southeast Asia rarely have this eye colour. Gray eyes might seem to change between the shades of blue, green and gray, mainly because of the lighting changes.
Blue
Blue eyes are quite common amongst people, especially those born in Germany, Netherlands, Iceland, Austria, Sweden, Norway, Denmark, Finland, and Estonia. The reason behind this eye colour is low amounts of melanin within the iris stroma. In Central Asia and Middle East, blue eyes are pretty rare. Since the production of melanin generally increases during the first few years of life, the blue eyes of some babies might darken as they get older.
Rarest Eye Colours
Amber
Amber eyes can be defined as the ones having a strong yellowish/golden and russet/coppery tint. The reason behind amber eyes is the deposition of ‘lipochrome’, the yellow pigment, in the iris. It is a very rare eye colour and also known as ‘wolf eyes’, since amber eye colour is very common in wolves.
Green
Green eye colour is amongst the rarest eye colour, with only 1-2% of the world's population born with green eyes. The reason for green eye colour is the production of moderate amounts of melanin. People born in Northern Europe and Nordic countries (like Iceland, Sweden, Denmark, Finland, Norway, Germany, and Netherlands) usually have green eyes.
Violet
Violet eyes are mainly seen in albinos. In effect, the eyes of some albinos appear to be violet because of the mixing of red and blue reflections. Violet eyes are either a form of blue eyes or a mutation.
Red
Red is probably the rarest eye colour amongst the human population of the world. It is mainly seen in case of albinos and is the result of either large quantities of the ‘normally scarce’ red areas in the eyes or a small leakage of blood into the iris.
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