Most of us were taught in primary or secondary school science class that eye colour is hereditary, with the dominant eye colour being brown and the recessive one blue. Upon closer scrutiny, the process of determining eye colour is not so simple. Here you can discover all the facts about hazel eyes.
Recent research has revealed that up to 16 genes instead of one dominant and one recessive gene may affect eye colour. Hence it is tough to confirm for sure the colour of a child’s eyes until he or she grows up a little more, owing to how multiple genes interact and express themselves. For instance, two blue-eyed parents could have a child with brown eyes, due to interactions of various genes.
Moreover, the first few years of life can result in major changes in eye colour. For example, some white babies are born with blue eyes and then develop brown, green or hazel eyes as time progresses. This phenomenon has little to do with genetics. However, this phenomenon can explain how this eye colour comes about.
Hazel eyes are a result of melanin, the same pigment that affects skin and hair colour.
The amount of melanin pigmentation your iris (thin and circular structure in your eye that gives it colour) produces is dependent on your genes. Various colours in your iris come about based on the amount of melanin present and how it is dispersed.
Notably, there are two types of melanin: The first is known as eumelanin. Eumelanin leads to brown eyes when it is present in huge amounts in the iris and blue eyes when it is more diffused. The second type of melanin is called pheomelanin. Increased levels of this second type can lead to eyes with a yellow hue.
People with hazel eyes have both types of melanin present in varying amounts and at various locations of the iris.The greater amount of melanin you have in your iris, the darker your eyes would be. People with the least amount of melanin have blue or green eyes. The varying amounts of melanin at different parts of the iris give people various combinations of brown (or yellow) and green eye colours.
These colour eyes are considerably rare. Only around 5% of the world’s population has this eye colour. Though anyone can have them, hazel eyes can typically be found in people with North African, Middle Eastern, Brazilian, and Spanish ancestry.
Like people with hazel eyes, green-eyed people also have both types of melanin in their irises. The difference between hazel-eyed and green-eyed people is how these pigments are scattered. While green eyes are more evenly scattered and diffuse the light that hits them in a way that appears green to others, hazel eyes also have areas of green. However the uneven distribution of pigments leads to brown or gold areas as well in people with hazel eyes. For instance one colour may seem like a ring around the pupil while the other color may be found on the outside edges of the iris. If you have green eyes with gold or brown areas, those are hazel eyes.
If you have light-coloured eyes, you would be more vulnerable to ocular melanoma, also known as eye cancer (cancer of a layer of the eye called the uvea). Thankfully, ocular melanoma is rather uncommon, impacting on only six of every million people in the U.S. each year. 
While your natural eye colour is permanent, you can try out a different eye colour, such as hazel, with coloured contacts that come in various shades of colours. Consult your doctor for a prescription.
 A. Hellem, “Hazel eye color: What causes it,” All About Vision, 07-Jul-2022. [Online]. Available: https://www.allaboutvision.com/conditions/eye-color-hazel.htm. [Accessed: 11-Aug-2022]
 “Hazel Colour (Pictures, Genetics & Facts),” Vision Center, 25-Apr-2022. [Online]. Available: https://www.visioncenter.org/conditions/hazel-eyes/. [Accessed: 11-Aug-2022]
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