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[1]:

  • Piebaldism
  • 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
  • Glaucoma
  • 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.



[1] https://www.webmd.com/eye-health/heterochromia-iridis