What Is Heterochromia?

Heterochromia is the medical term for having two different colored irises (the colored part of the eye) or having different colors within one iris. The first type is called complete heterochromia; the second is called sectoral heterochromia.

Heterochromia is most often the result of a genetic mutation. In some cases, it can be caused by an eye injury or an underlying disease, such as a benign eye tumor (called iris nevus) or cancerous tumors (like ocular melanoma).

This article describes the different types and causes of heterochromia. It also explains what is involved in the diagnosis and whether or not treatment is needed.

Types and Symptoms of Heterochromia

The only symptom of heterochromia is a difference in eye colors. Someone may, however, have other symptoms if their heterochromia stems from an underlying condition.

The extent of the difference in eye colors can differ. To reflect this, heterochromia is classified in different ways.

Cases can be distinguished by the amount of the iris that is involved:

• Complete heterochromia: One iris is a totally different color from the other. For example, the iris in one eye may be brown while the other is green.
• Partial or segmented heterochromia: Part of one iris is different in color from the rest of that same iris.
• Central heterochromia: A ring in one iris is a different color from the remaining parts of the same iris.

They can also be defined by the difference in the colors between the two eyes:

• Hypochromic heterochromia: The abnormal iris is of a lighter color than the normal one.
• Hyperchromic heterochromia: The abnormal iris is darker in color than the normal one
  

A Word From Verywell

Iris heterochromia is a condition in which a person has two different colored eyes. Although a large proportion of cases are the result of genetic mutation, heterochromia can also result from congenital disease or other ocular or systemic disorders. In these cases, further evaluation with an ophthalmologist is warranted.

— CHRISTINE L. LARSEN, MD, MEDICAL EXPERT BOARD

What Causes Heterochromia?

In the majority of cases, heterochromia occurs randomly. Most people born with heterochromia do not have any other health problems or symptoms. In rare cases, it is a symptom of another congenital (present from birth) disease.

It is also possible to develop heterochromia later In life due to a new, underlying condition, an eye injury or surgery, or even the use of certain medications.

Congenital Heterochromia

Some of the congenital diseases that can cause heterochromia include:

• Waardenburg syndrome: This group of genetic diseases results in changes in the color of the eyes, skin, and hair. It also sometimes leads to hearing loss.
• Piebaldism: A relatively harmless condition, it's characterized by a lack of pigment in the skin, eyes, and hair. People with this condition usually have portions of their hair, skin, and eyes that are lighter than normal.
• Sturge-Weber syndrome: There are brain, skin, and eye abnormalities due to the abnormal development of certain blood vessels. People with this condition usually have a port-wine birthmark—a pinkish/reddish/purplish mark on their faces.
• Parry-Romberg syndrome: In this condition, the skin, soft tissue, muscles, and sometimes bones on one side of the face slowly weaken and atrophy. It’s a very rare disease; people with it also suffer from seizures.
• Hirschsprung disease: This condition affects the large intestine. Mainly newborn babies and toddlers have this condition, and it makes them unable to pass stool easily and properly.
• Tuberous sclerosis (Bourneville syndrome): A rare disease, it involves the formation of noncancerous tumors in many different body organs such as the brain, heart, skin, kidneys, eyes, and lungs.

Acquired Heterochromia

Any of the following could cause heterochromia to develop in those who were not born with it:

• Horner’s syndrome: This rare condition is caused by damage to the nerves connecting the brain and eye. It usually affects just one side of the face and is characterized by droopy eyelids and permanently small pupils on that affected side.
• Neuroblastoma: A form of cancer, it starts in the nerve cells of the sympathetic nervous system. It affects mainly infants and younger children.
• Fuchs' syndrome, also known as heterochromic cyclitis syndrome: Fuchs’ heterochromic iridocyclitis is an unusual form of chronic, low-grade anterior uveitis with variable clinical appearance. Typically the lighter-colored eye is the affected eye due to atrophy or loss of iris tissue. Symptoms can include on-and-off blurring and pain.
• Glaucoma: This is a progressive disease where fluid builds up in the front part of your eye(s) and causes damage to the optic nerve.
• Melanoma of the eye: Also called ocular cancer, this is a cancer that develops in the eye cells that produce melanin.
• Eye injury or trauma
• Certain types of eye drops
• Eye surgery
• Some of the drugs used to treat glaucoma
• Diabetes

There are generally no risk factors associated with heterochromia, and it is not in itself an inherited disease. However, it is possible to have heterochromia because of inherited diseases like Waardenburg syndrome and piebaldism.

Diagnosis

Heterochromia can be diagnosed by an ophthalmologist (eye doctor). They will examine your eyes to confirm the diagnosis. Signs of underlying diseases will also be assessed.

If your eye doctor suspects that the heterochromia is a symptom of another disease, you may be referred to a healthcare provider who treats that condition. Further investigation may involve blood tests, imaging tests, and genetic tests.

Does Heterochromia Need Treatment?

Typically, there’s no need to treat heterochromia if it isn't caused by another condition.

However, if you want both your eyes to be the same color, you may want to speak to your eye care professional about getting custom-made contact lenses to make your eyes match.

If your heterochromia is a result of an underlying disease or injury, those will need to be treated.

Summary

When a person has two different colored eyes, or one eye that is multi-colored, this is known as heterochromia. Heterochromia most frequently occurs at birth as the result of a random genetic mutation. In this case, it requires no treatment. Heterochromia can also be a symptom of a congenital condition or the result of an illness or injury, in which case the underlying condition will need to be treated.