Can my eyes change colour?

By Sophia Miettinen

Your eye colour is so unique that no one else in the world has the same colour as you!

The most common eye colour is brown, with more than half of the world having brown eyes. Some brown eyes are so dark they can appear black. Other eye colours include green, blue, hazel, grey, and even red!

So why do we have different colour eyes?

Scientists used to think that eye colour was determined by two genes, and that you could predict your eye colour based on your parents and grandparents eye colours, but this isn’t true. Scientists now think that there are as many as 16 different genes that help decide what eye colour you have.

Your eye is made up of the main white part called the sclera, the coloured part called the iris, and the black small circle inside the iris called the pupil. If you have brown eyes, you have lots of melanin in your iris. Melanin is a brown coloured pigment made by special cells called melanocytes. Melanocytes produce melanin to protect us against the sun’s harmful ultraviolet rays, and it can be found in our eyes as well as our skin and hair. If you have blue eyes, you do not actually have blue pigment in your eyes. Instead, blue eyes have less of the brown melanin pigment to absorb the light, so more light bounces back out of your eye and appears blue. This same bouncing of the light is why the sea and sky look blue.

If you have very little or no melanin in your body, you may have a condition called albinism. If you have albinism your skin and hair are very pale, and very rarely your eyes may appear like they are red. Your eyes appear red because there is very little melanin in your iris, and you can see the blood vessels in the back of your eye.

Some people may even have two different coloured eyes. This is called heterochromia iridum.

You may have heard that everyone is born with blue eyes. When babies are born, their eyes do not have much melanin. This is because melanocytes produce melanin when there is lots of light, and babies have spent many months in darkness until they were born. By the time you are nine months old, your eyes will usually have their final colour. But if you have more melanin in your body, you’ll usually be born with darker skin and brown eyes, and your eyes won’t seem to change colour so much. Sometimes your eyes will change colour as you get older too. This can happen because of certain diseases, medications, and the sun’s harmful rays causing sun damage freckles in your eyes. It is important to keep your eyes protected with sunglasses throughout the year.

Can your eyes change colour for any other reason?

Some people say their eyes change colour when they are feeling different emotions such as happiness or sadness. What is really happening is that because your iris is a muscle, when it contracts and relaxes, it makes the iris change size. When the iris is smaller, the brown melanin pigments get squashed together and makes the eye appear darker. The clothes you are wearing and how bright it is where you’re standing can make it seem as if your eyes are changing colour too. Have a look in the mirror and see what colour your eyes appear today!