Heterochromia is when a person has differently coloured eyes or eyes that have more than one colour in them, which affects less than 1% of the population.
It’s caused by genes passed down from your parents or by something that happened when your eyes were forming. In rare cases, it can be a symptom of a medical condition. It is usually harmless and doesn’t need to be treated.
Your eyes gets their colour from a pigment called melanin. The amount of melanin effects how dark or light the eye is. Less melanin leads to lighter eye colour and more melanin makes darker eyes.
There are 3 types:
- Complete heterochromia – means one iris is a different colour from the other.
- Segmental heterochromia – means different parts of one iris are 2 or more colours.
- Central heterochromia is when the outer ring of your iris is a different colour from the rest.
When you’re born with different-coloured eyes, it’s called congenital heterochromia.
There are different conditions that can cause this which include:
- Hirschsprung disease
- Bloch-Sulzberger syndrome
- Von Recklinghausen disease
- Bourneville disease
- Waardenburg syndrome
- Sturge-Weber syndrome
- Parry-Romberg syndrome
- Horner’s syndrome
If your eye colour changes when you are older, it is called acquired heterochromia.
This can be caused by:
- Eye injury
- Certain medicines
- Neuroblastoma which is a cancer of the nerve cells
- Eye cancer or melanoma. One sign of eye melanoma is a dark spot on the iris.
An optometrist can detect these eye changes easily in regular eye exams. Read how often you should get your eyes tested here on our blog.