Heterochromia iridis, also known as heterochromia of the iris, is a rare condition in which the iris of one or both eyes has a different color than the other. It is triggered by changes in the location and amount of melanin—the pigment that gives eyes their color. While it is not associated with health problems, it can be a symptom of a condition. Here is a look at what causes heterochromia, its signs, and treatment.

Causes
Heterochromia iridis or iridium can show up in different ways, such as full or partial color difference, sectoral heterochromia (when only a part of the iris is a different color), or central heterochromia (where the inner part of the iris has a different color). Heterochromia is associated with several factors, like genetics, medical conditions, or accidents. Here are a few of the most popular causes of heterochromia:

Genetic factors: Genetic changes or inherited traits can cause changes in eye color. It can be a birth defect or develop later in life. Heterochromia can be passed down as autosomal dominant, autosomal recessive, and X-linked inheritance.

Conditions: Horner syndrome, Waardenburg syndrome, Sturge-Weber syndrome, Fuchs’ heterochromic iridocyclitis, and neurofibromatosis are a few conditions that can change the color of the eyes by affecting the nerves, blood vessels, or pigment cells in the iris.

Eye injuries: Damage to the iris or problems with melanin can trigger heterochromia. Eye diseases, like uveitis or an infection from the herpes simplex virus (HSV), can also cause inflammation in the iris and change how melanin is produced or distributed, leading to heterochromia iridis.

Prescription treatment: Certain eye drops or other prescription treatments for glaucoma can cause changes in eye color, leading to heterochromia iridis as a side effect.

Radiation or chemotherapy: Eye tumors or other types of cancer treated with radiation or chemotherapy can sometimes cause changes in eye color.

Congenital abnormalities: Heterochromia iridis is sometimes linked to rare congenital disabilities, like coloboma, a gap or hole in the structure of the eye.

Common signs
Differences in eye color are the main symptoms of heterochromia iridis. The color change can be small or obvious and develop in one or both eyes. Depending on the underlying cause, heterochromia can be accompanied by the following signs:

Changes in vision: Some people with heterochromia iridis may experience vision changes. Depending on the cause, the changes could be blurry vision, sensitivity to light, or other problems with eyesight.

Eye discomfort: Some people with heterochromia iridis may feel pain, redness, or itching in their eyes. This when the underlying cause is a medical condition or an injury.

Uneven pupil size: Those with heterochromia may have uneven pupils.

Photophobia: People with heterochromia may have photophobia, or sensitivity to light, especially if the changes in color are caused by inflammation or other eye problems.

Management options
The treatment plan here is determined by the underlying cause and extent of the difference in eye color. For some people, treatment may be unnecessary, especially if the problem is not causing symptoms or discomfort. Here are a few options the doctor might recommend:

Prescription treatment: This may focus on treating the underlying condition if heterochromia iridis is caused by an underlying medical condition, like Horner syndrome or Fuchs’ heterochromic iridocyclitis. So, one may have to take prescription options to control inflammation, ease pain, or treat any other signs or problems that arise.

Cosmetic management: If the differences in eye color are not accompanied by discomfort or other symptoms, one can use colored contact lenses or artificial iris implants to make both eyes take on the same color.

Regular eye exams: People with heterochromia iridis may have to get regular eye exams and visit an ophthalmologist or optometrist often. The doctor will check for changes in their eyesight or eye health and treat any underlying conditions that may be causing the differences in eye color.

Additionally, those with heterochromia can speak to a doctor even when they are not experiencing pain or discomfort. This can help them determine the underlying cause of the difference in eye color and see if it can be managed with treatment. Heterochromia iridis is a rare condition that can be triggered by genes, health conditions, or injuries to the eye. It is marked by a change in eye color that can be slight or obvious. Even though heterochromia iridis is usually a harmless condition that does not cause vision loss or other major health problems, it may be linked to other issues that need treatment and immediate care.