Are you wondering what determines your eye colour? Have you ever been curious about why some people have blue eyes while others have brown? If so, you’re not alone! For centuries, people have been trying to unlock the secrets of eye colour and understand why some people have blue eyes while others have brown or green.
Eye colour is a powerful indicator of genetic traits, and it’s determined by a mix of genes that you get from your parents. What’s more, eye colour isn’t just one simple trait—it’s a complex combination of various pigments and hues. In this comprehensive guide, we’ll explore the science behind eye colour, including how it’s inherited, and how it can change over time.
The eyes are often referred to as the “windows to the soul.” It is no surprise, then, that the colour of one’s eyes can be an important part of an individual’s identity. We are all familiar with the common eye colours like brown, blue, and green, but there are many more variations that can affect how a person’s eyes appear. Let's take a look at the different eye colours
Brown eyes
Brown eyes are the most common eye colour in the world, accounting for nearly 80% of the population. Brown eyes are caused by the presence of a large amount of melanin, a pigment that absorbs light and gives the eye its colour. Brown eyes can range from light amber to dark chocolate, and can be further broken down into subtypes based on the amount of melanin present.
Blue eyes
Blue eyes are much less common, but still account for around 8% of the population. Blue eyes are caused by a lack of melanin but an increased presence of a protein called lipochrome. This protein scatters light, giving the eye its blue hue. Blue eyes can range from light sky blue to a deep navy, and can also be broken down into subtypes based on the amount of lipochrome present
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Green eyes
Green eyes are even rarer, making up only 2% of the population. Green eyes are caused by a combination of melanin and lipochrome, as well as a yellow pigment called pteridine. This combination of pigments creates the green colour, and can range from a light aqua to a deep emerald.
Hazel eyes
Hazel eyes are the rarest eye colour, accounting for only around 1% of the population. Hazel eyes are caused by a combination of melanin and lipochrome, but with a higher concentration of melanin than green eyes. This combination of pigments gives the eye its unique mix of green, brown, and gold. 
Eye colour is a fascinating trait that is determined by a complex combination of factors, including genetics, age, ethnicity, and environment. While blue and brown eyes are the most common colours, there are many other hues that can be seen in humans. The various factors that affect eye colour can range from biological to environmental, and each one can have a unique impact on the colour of an individual's eyes.
It is a largely inherited trait, but can also be altered by environmental influences such as exposure to sunlight, age, and even illness. Let’s go over the various factors that determine eye colour.
Genetics
The most important factor in determining eye colour is genetics. Your eye colour is determined by the amount and type of melanin in your iris. The amount and type of melanin is determined by your parents’ genetic makeup. Generally, people with brown eyes have more melanin in their iris, while people with blue eyes have less melanin.
Melanin
is a pigment found in the iris of the eye, and it is responsible for the colour of the eyes. The amount of melanin in the iris determines the eye colour. Darker eyes contain more melanin, while lighter eyes contain less. The colour of melanin can range from light brown to black, and the colour of the eyes will depend on the type and amount of melanin present.
Environmental Influences
Environmental factors, such as sunlight, can also influence the amount of melanin in the eyes, resulting in a change of eye colour. Sunlight exposure can cause the melanin in the eyes to darken, resulting in a darker eye colour. On the other hand, a lack of sunlight can cause the melanin to lighten, resulting in a lighter eye colour.
Illness
can affect your eye colour by causing the iris of your eye to become inflamed. This inflammation can cause the colour of the iris to change temporarily. Certain medications, such as corticosteroids, can also cause the colour of your eyes to change. In some cases, a serious health condition can cause a permanent change in eye colour.
Aging
It affects eye colour because the amount of pigment in the iris changes as you age. As you get older, the amount of pigment in the iris decreases, resulting in a lighter eye colour. This is why some people's eyes may appear to be a lighter shade as they age.
Interestingly, eye colour can change over time. This is because the amount of melanin in the iris can be affected by hormones, especially during pregnancy and puberty.
In conclusion, eye colour is a fascinating and complex trait that’s determined by genetics, hormones, and melanin levels in the iris. It’s also possible for eye colour to change over time, due to hormonal shifts or a decrease in melanin production. Understanding the science behind eye colour can help us appreciate the unique beauty of our own eyes.