11 January, 2024
Have you ever wondered why people have different eye colours? Or why blue eyes are less common than brown eyes? This article dives into the fascinating world of eye colour, exploring the most popular colours and the science behind why our eyes look the way they do.
Your eye colour is determined by genetics and the amount of melanin in your iris. It’s not just about inheriting mum’s blue eyes or dad’s brown ones. There’s more to it, including genetics of eye colour, the amount of melanin, and even genetic variations.
Our genes control how much melanin is present in our irises. But it’s not as simple as one gene for one colour. Multiple genes are involved in this process, leading to a wide range of possible colours.
Melanin, the pigment found in your skin and hair, is also responsible for the colour of your eyes. This pigment comes in different types and amounts, which can lead to a wide range of eye colours. If your irises have a lot of melanin, your eyes will be darker. This is why brown eyes, which have high melanin content, are the most common eye colour globally.
But melanin’s role in eye colour is more than just about how much is there. It’s also about where it’s located. For instance, blue eyes occur when there’s less melanin, mainly at the back of the iris. This lack of pigment at the front of the iris results in the blue colour due to the way light scatters when it hits the eye.
The genetics behind eye colour is a fascinating and complex topic. It’s not just one gene that decides what colour your eyes will be. In fact, several genes are involved, and they all interact in different ways to determine your eye colour.
One of the key genes in this process is known as OCA2. This gene helps control how much melanin is produced in the iris. Changes in this gene can lead to different amounts of pigment and, thus different eye colours. But OCA2 isn’t working alone. Another gene called HERC2 is also involved. It can turn on or off the OCA2 gene, influencing how much melanin is produced.
But here’s where it gets even more interesting: even though these genes play a big role, they don’t tell the whole story. Other genes can influence eye colour in minor ways, adding to the variety we see in human eyes. This is why predicting eye colour based on parents’ eyes isn’t always straightforward.
Eye colour isn’t just about the overall hue. If you look closely at an iris, you might see patterns and speckles. These variations add uniqueness to each person’s eyes. They’re like fingerprints for your eyes!
Patterns in the iris can range from circular rings to bursts of colour radiating from the pupil. And those little speckles? They’re unique to each individual. So, while you might share the same eye colour with someone, the patterns in your irises make them uniquely yours.
Around 8-10% of people have blue eyes. Blue eyes, while less common than brown, captivate with their range of hues – from a deep ocean blue to a lighter sky blue. Interestingly, blue eyes aren’t blue because of blue pigmentation. Instead, they appear blue due to the way light scatters in the stroma, the front part of the iris. This phenomenon, known as Rayleigh scattering, is the same reason the sky appears blue. Regions like Northern Europe, particularly Iceland and the Netherlands, have a higher prevalence of blue-eyed individuals, which is thought to be due to historical population movements and genetic bottlenecks.
Comprising about 5% of the population, hazel eyes are a mix of brown and green, often with flecks of gold. These eyes are particularly unique because their colour can appear to change depending on the lighting or the colours the person is wearing. This chameleon effect is due to the moderate amount of melanin in the iris and how light interacts with it.
Green is among the rarest colours, found in about 2% of people. The green hue is achieved with a lower melanin level than brown eyes but a bit more than blue eyes. The green colour comes from a combination of a light brown melanin pigment and the blue light scattering effect. Green eyes are especially prevalent in regions with Celtic or Germanic ancestry, such as Scotland, Ireland, and Northern Europe, adding a touch of mystique to their allure.
These eyes are light brown with golden or copper tints. Amber coloured eyes make up about 5% of the population. They have a solid golden or coppery tint and are often mistaken for a light brown. This unique colour comes from the presence of a yellowish pigment in the iris. Amber eyes are less common and are a spectacular sight, often glowing warmly under sunlight.
Very rare, gray eyes are seen in about 3% of the population and are common in Asia and the Middle East. They often appear as a pale or smokey gray. They have even less melanin than blue eyes, and the unique colour is due to the combination of the collagen in the stroma and the scattering of light.
While it’s true that a child’s eye colour can often be predicted by looking at the parents’ and relatives’ eye colours, the genetics behind this is quite complex and sometimes surprising. For instance, two blue-eyed parents are generally expected to have blue-eyed children, but there are rare cases where they might have a brown-eyed child. This can happen due to hidden genetic traits passed down from ancestors, known as recessive genes.
Eye colour is influenced by both recessive and dominant genes. Brown eye colour is generally considered dominant, which means that if one parent has brown eyes (especially if they carry two dominant genes for it), it’s more likely for their child to have brown eyes. Blue and green eyes are often recessive, meaning both parents need to pass on these genes for their child to have these eye colours.
However, it’s not always as straightforward as one dominant gene overpowering a recessive one. Sometimes, a combination of multiple genes from each parent can result in an eye colour different from either parent. This is why you might see a brown-eyed child from two blue-eyed parents – hidden genes from the family tree can resurface in surprising ways.
It’s also fascinating to note that many babies are born with blue or grey eyes, regardless of their genetic eye colour. This is because the melanin, which determines the final eye colour, takes some time to develop and deposit in the iris. It’s common for a child’s eye colour to change in the first few years of life as this melanin develops. For example, a baby born with blue eyes might end up with green or brown eyes as they grow older.
In cases where parents have mixed eye colours, like one with brown eyes and the other with blue, predicting the child’s eye colour becomes even more unpredictable. The child could end up with any combination, including hazel, which is a mix of green and brown.
Heterochromia is a unique condition where a person has two different coloured eyes. This can mean each eye is a completely different colour, like one blue and one brown, or it can mean one eye has two different colours in it. Heterochromia is rare and usually harmless. It often happens because of genetics – it’s just the way the person was born. But sometimes, it can be caused by an injury or a health condition.
Albinism is a condition where a person has less melanin in their body. Melanin is what gives colour to our skin, hair, and eyes. People with albinism usually have very light-coloured eyes, sometimes blue or even pinkish. This is because they have very little melanin in their irises. The lack of melanin can make their eyes very sensitive to light and can sometimes lead to vision problems.
While your eye colour usually doesn’t directly affect your health, some conditions linked to eye colour can have health impacts. For example, as mentioned, people with albinism might have vision issues due to their light eye colour. It’s really important for everyone to look after their eye health. This means regular eye check-ups and protecting your eyes from too much sunlight.
People with lighter eyes, like blue or green, might find they are more sensitive to bright light. This is because they have less melanin to protect their eyes from the sun’s harsh rays. So, if you have light-coloured eyes, wearing sunglasses on sunny days is a good idea.
The world of eye colour is rich and varied, influenced by the complex interplay of genetics and melanin. From the common brown to the rarer hues of blue-green and grey, each colour tells a story of genetic interactions. And beyond just colour, the unique patterns in each iris add another layer of beauty and complexity to our eyes. So next time you look into someone’s eyes, remember, you’re looking at a unique combination of colour and patterns
But beyond the aesthetics, the health of our eyes is crucial. Regardless of their colour, our eyes are essential organs that require care and attention. Regular eye exams are vital for maintaining good vision and early detection of potential eye problems. Protecting our eyes from harmful UV rays, managing screen time, and ensuring proper nutrition are all key steps in preserving our eye health.
Taking care of your eyes should be a priority, and EyeQ Optometrists make it easy. With a focus on delivering the very best in clinical eye care, EyeQ ensures that your eyes receive the best possible treatment throughout every stage of life. Our eye care services include eye health assessments, contact lenses, prescription lenses, children’s vision care, behavioural optometry, and more.
With locations across various states and territories including New South Wales, ACT, Queensland, South Australia, Victoria, and Western Australia, you’re likely to find a practice near you. To book an eye test or to learn more about the services we offer, find the nearest EyeQ practice near you. Don’t wait until you experience vision problems; take a proactive approach to your eye health with EyeQ Optometrists.
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