Have you ever seen someone with differently colored eyes or eyes that have more than one color? For instance, do you know someone with blue eyes flecked with brown? The condition is called heterochromia iridis, and it affects the iris, the colored part of your eye.

Most of the time, it doesn't cause any problems. It's often just a color quirk that's caused by genes inherited from parents or by a problem that happened when the eyes were being formed. In rare cases, though, it can be a symptom of something else. It could be a health problem or a condition a person was born with.

It's common in some animals but rare in humans. It affects fewer than 200,000 people in the United States.

A Closer Look at Eye Color

Your iris gets its color from a pigment called melanin. It's what makes them blue, green, brown, or hazel. Less melanin leads to lighter eye color. More melanin leads to darker eyes.

Sometimes, the amount of pigment in your eyes can vary:

  • Complete heterochromia means one iris is a different color than the other. For example, you may have one blue eye and one brown eye.
  • Segmental heterochromia means different parts of one iris are different colors.