While most people know that the colour of your eyes is determined by genetics, just like your hair and skin colour, there are also some surprising and fascinating facts about eye colour that you may not have heard before. With no two people sharing the same hue, let’s explore some fun facts about what makes eye colour as unique as fingerprints.
Eye colour is determined by melanin
The colour of your eyes depends on the amount of melanin, the pigment responsible for skin and hair colour, present in the iris.
Brown eyes have the most melanin, while blue eyes have the least. Green and hazel eyes have levels of melanin that fall in between. The more melanin, the darker the eye colour.
Brown eyes are the most common
Globally, brown is the most common eye colour, with around 55-79% of the world’s population having brown eyes. They are especially prevalent in Asia, Africa and South America.
In many cultures, brown eyes are associated with trustworthiness and warmth.
Blue eyes are genetically “new”
If you have blue eyes, you’re related to a single common ancestor who lived between 6,000 and 10,000 years ago. Blue eyes are the result of a genetic mutation that affects melanin production; before this mutation, everyone had brown eyes.
Today, blue eyes are found in about 8-10% of the world's population.
Green eyes are the rarest
Only about 2% of the world’s population has green eyes. They result from a unique combination of low melanin levels in the iris and the way light scatters through it.
Green eyes are caused by a genetic mutation that produces less melanin than brown eyes but slightly more than blue eyes.
The likelihood of having green eyes is influenced by a complex interaction of multiple genes and specific genetic variations known as single nucleotide polymorphisms (SNPs).
Green eyes are most found in people of European descent, especially those from Celtic or Germanic ancestry.
Hazel eyes can change colour
People with hazel eyes may notice that their eye colour seems to change based on the lighting or what they’re wearing. This is due to the combination of colours in the iris and how light reflects off them.
Hazel eyes often contain shades of brown, green and gold, which gives them a unique ability to shift in appearance.
Heterochromia: when your eyes don’t match
Heterochromia is an extremely rare condition affecting less than 1% of the world’s population, where a person has two different-coloured eyes or variations in colour within one eye. It can be present from birth or develop due to injury or medical conditions.
Celebrities like Kate Bosworth and Mila Kunis are famous examples.
Babies are born with blue or grey eyes
Most babies are born with blue or grey eyes, regardless of their eventual eye colour. This is because melanin production isn’t fully developed at birth.
Over the first few months of life, their eyes may darken as melanin levels increase. By around six to twelve months, the baby’s true eye colour typically emerges.
Eyes can reveal your mood
While your eyes don’t technically change colour based on your emotions, they can appear to do so. When you’re feeling happy or excited, your pupils dilate, which can make your eyes look darker.
Alternatively, when you’re tired or sad, your pupils contract and your eye colour might appear lighter.
Eye colour can affect sensitivity to light
People with lighter eye colours, such as blue or grey, may be more sensitive to bright light. This is because lighter eyes have less melanin, which offers less protection against the sun's harmful rays.
While everyone should wear sunglasses when outdoors, it's especially important if you have light-coloured eyes.
Your eye colour can change over time
While rare, it’s possible for your eye colour to change over time due to age, injury or health conditions.
Conditions like Horner’s syndrome or pigmentary glaucoma can affect the melanin in your iris, leading to a change in eye colour.
If you’re curious to learn more about how your eye colour might affect your vision or are interested in tips for maintaining good vision for life, speak to your optometrist today.
