What Is Heterochromia?

Heterochromia is a medical term used to describe variations in color. Heterochromia iridum specifically refers to variations in the colored part of the eye, called the iris. The variation can either be complete (in which you have different-colored eyes) or sectoral (meaning that part of one iris has a different color from the rest).

Heterochromia is most often the result of genetics. An eye injury and certain diseases, including non-cancerous tumors (called iris nevus) and cancerous tumors (like ocular melanoma), can also alter the color of an iris.

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 (the colored part of your eye) 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: When the abnormal iris is of a lighter color than the normal one.
• Hyperchromic heterochromia: When the abnormal iris is darker in color than the normal one.
  

What Causes Heterochromia?

The majority of cases of heterochromia are random. 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: A group of genetic diseases that result in changes in the color of the eyes, skin, and hair. It also sometimes leads to hearing loss.
• Piebaldism: A relatively harmless condition that’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: A condition where 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: A condition that 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 that 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: A rare condition that’s 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 that 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 there.
• Melanoma of the eye: Also called ocular cancer, this is 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 also not an inherited disease. However, it is possible to have heterochromia because of inherited diseases like Waardenburg syndrome and piebaldism.

Diagnosis

Heterochromia is diagnosed by an eye doctor. They will examine your eyes to confirm that there is heterochromia present. Signs of underlying or causative diseases will also be looked out for.

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, including genetic tests.

This typically is not necessary, however.

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 have the same color, you may want to speak to your eye care professional about getting custom-made contact lenses to suit your particular kind of heterochromia.

If your heterochromia is as a result of any underlying disease or injury, treatment will be focused on the condition or injury. Given the array of potential causes, treatment possibilities vary widely.

A Word From Verywell

Being born with two different eye colors is often of no medical concern, but it can be a sign of a medical issue if it develops later In life.

Still, it's best to see a healthcare provider for an evaluation to make sure that there is no underlying cause that requires treatment. This is particularly important if you notice that you or your child's eyes have changed color.