Here are some amazing facts about the iris that might surprise you – and help you appreciate just how incredible your eyes really are.
8 Incredible Facts About the Iris
Your iris is the coloured circle in your eye – the part that makes your eyes brown, blue, green or grey. But this small ring of muscle does so much more than just give your eyes colour. It plays a key role in how your eyes work, and it’s full of fascinating features!
The Iris Photography Campaign: World Sight Day 2025
For World Sight Day 2025, Orbis invites you to take part in the Iris Campaign - a celebration of the beauty and uniqueness of our eyes, and a reminder of why protecting everyone's sight is so critical.
1. Your Iris Controls How Much Light Enters Your Eye
The iris works like a camera shutter. It gets smaller in bright light and bigger in the dark, controlling the size of your pupil to protect your retina and help you see clearly.
2. No Two Irises Are Alike – Not Even in Twins
Each iris has a unique pattern made of tiny fibres, colours and textures. Even identical twins have different irises – which is why iris recognition is used in high-security systems like airports and smartphones.
3. Your Eye Colour Comes From Your Iris
Eye colour is created by melanin, the same pigment that colours your skin and hair. More melanin = darker eyes. Less melanin = lighter eyes like blue or grey.
Ever wondered what your iris looks like up close? Come to King’s Cross and see for yourself.
4. Blue Eyes Aren’t Actually Blue
Blue eyes don’t have blue pigment. They appear blue due to how light scatters in the iris – a bit like how the sky looks blue. All eyes would look dark if there was no light to bounce around.
5. Some People Have Two Different Coloured Eyes
It’s called heterochromia, and it can be complete (one eye is a different colour) or partial (part of one iris is a different colour). It’s rare, but usually harmless – and very striking!
6. Your Iris Never Stops Moving
Even when you try to keep your eyes still, your irises make tiny movements to adjust your pupil and help you focus. It’s all happening without you noticing!
This stunning iris photo could be yours too — come and capture your own unique eye portrait at King’s Cross.
7. Emotions Can Change Your Pupil Size
Your pupil dilates not just in the dark, but also when you're feeling strong emotions like fear, surprise or love. Your iris responds instantly, revealing what you might be feeling before you say a word.
8. Most Babies Are Born With Blue or Grey Eyes
Many babies – especially of European descent – are born with blue or grey irises that may change in the first year as melanin develops. Final eye colour usually settles by age 3.
Why the Iris Matters
The iris is a small but mighty part of the eye. It protects your vision, reacts to your environment, and even helps show your emotions. But like all parts of the eye, it needs protection and care.
At Orbis, we believe everyone has the right to healthy vision. Millions of people around the world are at risk of losing their sight due to preventable or treatable eye conditions – especially in communities without access to basic eye care.
Help Us Make Eye Care Equal for Everyone
- See the beauty of your own eyes. Visit the Orbis Iris Photo Booth in the King’s Cross Station ticket hall, 8–10 October. Get your iris photographed, take home a stunning artwork – and help fund our global sight-saving work.
Authored by John Ferris
John Ferris is a UK ophthalmologist and a consultant Ophthalmologist at Cheltenham General Hospital since 1999. He is also an Orbis Volunteer and Orbis UK trustee.
