Heterochromia

Heterochromia is when a person has two different colored eyes or segments of different colors in one eye. This unique eye condition often catches attention because it is rare and visually striking. Genetics most often cause heterochromia, but injury, certain diseases, or even some medications can also lead to it.

In many cases, genetics passed down from parents lead to heterochromia, and it is harmless. However, changes in eye color later in life may signal medical issues like injury, bleeding, or diseases affecting the eye. Understanding why heterochromia happens can help people recognize when a doctor’s visit might be needed.

Definition of Symptom

Heterochromia means a person has different colors in their irises or within the same iris. This color variation can affect one eye, both eyes, or even sections of an iris. People may notice heterochromia by looking at the eyes. One eye might be blue while the other is brown, or a single eye could have two distinct colors. The symptom of heterochromia mainly appears in these forms:

• Complete Heterochromia: Each eye is a different color.
• Sectoral (Partial) Heterochromia: Part of one iris is a different color from the rest.
• Central Heterochromia: There is a ring of color around the pupil that is different from the main color of the iris.

Heterochromia itself is a visual sign, not a disease. It is a noticeable difference in eye color that might be harmless or linked to another condition. Most cases start at birth due to a harmless gene difference. In rare situations, it may show up later and signal an underlying health issue, so a doctor may check for other symptoms. A simple way to recognize heterochromia is by comparing the colors of both eyes or checking for unusual patterns of color in the irises.

Possible Causes/ Diseases Condition

Different factors can cause heterochromia. Genetic mutations commonly lead to it. If a person is born with two different colored eyes, a harmless gene change is often the reason. Some people develop heterochromia later in life, called acquired heterochromia. Eye injury, eye surgery, or certain medications like some glaucoma eye drops can cause this. Heterochromia can also link to health conditions, such as:

• Waardenburg syndrome
• Horner’s syndrome
• Sturge-Weber syndrome
• Fuchs’ heterochromic iridocyclitis

Swelling inside the eye and bleeding in the eye can also cause a color change. Tumors or infections in the eye may play a role too. A table below shows some causes and whether they are present at birth or happen later:

Cause/Condition	Congenital (Birth)	Acquired (Later)
Genetic mutation	✓
Injury		✓
Waardenburg syndrome	✓
Eye surgery		✓
Fuchs’ heterochromic iridocyclitis		✓
Medications (e.g., glaucoma drops)		✓

In rare cases, other inherited diseases or unique genetic situations, like mosaicism or chimerism, can also lead to heterochromia.

Other Non-Disease Causes

Heterochromia can sometimes happen for reasons not linked to disease or medical conditions. Genetics is one of the most common non-disease factors. Some people are simply born with differently colored eyes because of harmless genetic mutations. This trait may appear even if no one else in the family has it.

Eye injury can also lead to heterochromia. If someone injures their eye, the trauma can change the color of the iris in one eye. This change can be permanent. Certain eye drops for conditions like glaucoma can also cause color shifts. These changes sometimes appear after months or years of treatment. Below is a quick overview of other non-disease causes:

Cause	Description
Genetic Mutation	Inherited or natural change in genes.
Eye Injury	Trauma that leads to a color change in one eye.
Eye Drops	Some medicines can gradually alter iris color.
Mosaicism/Chimerism	Genetic differences within the body’s own cells.

Mosaicism and chimerism happen when there are different sets of genetic material in a person’s cells. This can lead to unique patterns, including heterochromia. None of these causes are linked to illness. They usually do not affect vision or health.

How It Causes the Symptom

Heterochromia happens when the amount or placement of melanin is different in each eye. Melanin is the pigment that gives color to the eyes, hair, and skin. When a gene mutation or injury changes how melanin spreads, one eye may have more or less pigment than the other. This makes each iris look like a different color.

Injury, disease, or swelling in the eye can also change melanin. If someone has bleeding, inflammation, or infection, the way melanin appears can shift in one eye. Rarely, certain medical conditions or syndromes cause changes to eye color after birth. For example, some people develop heterochromia from illnesses or as a reaction to medication.

Common Ways Heterochromia Appears

Type	Description
Complete Heterochromia	Each eye is a completely different color.
Sectoral (Partial) Heterochromia	Part of one iris is a different color.
Central Heterochromia	There is a ring of another color around the pupil.

The changes are usually harmless, especially if present from birth. Most people do not feel any pain or discomfort from heterochromia itself.

Possible Complications

Most people with heterochromia do not have any health problems linked to it. The condition itself is usually harmless, especially if it has been present since birth. If heterochromia develops later in life, an underlying health issue might be responsible. Some of these issues can affect eye health and vision if not addressed. Possible complications may include:

• Vision changes
• Increased risk of glaucoma
• Inflammation in the eye
• Damage from eye injuries

If injury or a medical condition causes heterochromia, other symptoms may appear, such as eye pain, redness, sensitivity to light, or blurry vision. Some rare conditions that cause heterochromia, like Fuchs’ heterochromic cyclitis or Waardenburg syndrome, can lead to more serious complications, including decreased vision or hearing problems.

People who notice a sudden change in eye color should see an eye doctor. Common signs to watch for:

Symptom	Possible Concern
Color change	Underlying disease
Pain/redness	Inflammation/injury
Blurred vision	Eye health problem
Light sensitivity	Irritation/damage

When to Seek Medical Attention

Pay attention to any sudden changes in eye color. Sudden or recent heterochromia can sometimes signal an underlying health issue. Seek medical attention if heterochromia appears along with any of the following symptoms:

• Eye pain or discomfort
• Blurry vision
• Changes in vision
• Redness or swelling
• Sudden change in the shape or size of the pupil

If a child develops heterochromia early in life, a healthcare provider should evaluate it. Some conditions linked to heterochromia may appear in babies and children. If someone develops heterochromia later in life, it can sometimes mean that the eye is unhealthy or has been hurt.

If eye color changes after an injury or with other new symptoms, see an eye doctor. Eye doctors, such as ophthalmologists or optometrists, can find out the cause of heterochromia. They perform an eye exam and may use tests to check for other eye problems.