Heterochromia: Causes of Two Different Coloured Eyes

May 17, 2026

Look closely at certain faces in a crowded room, and you may spot something striking: one eye a soft hazel, the other a clear blue. Or one entirely brown with just a slice of green in the iris. This is heterochromia, the condition in which a person has two different coloured eyes, or two colours within the same eye. It is unusual enough to draw attention, yet in most cases perfectly harmless.

This guide walks you through what heterochromia is, why it happens, which forms need medical review, and how it is managed when needed.

What Is Heterochromia?

Heterochromia is a condition in which iris colour differs between the two eyes or within parts of the same eye. The iris is the coloured ring around the pupil. Its colour comes mostly from melanin, the same pigment that gives skin and hair their colour. More melanin leads to brown, less to green, blue, or grey.

Heterochromia is not a disease in itself. It is a pattern, and the important question in any case is: is the pattern present from birth, or did it develop later?

Types of Heterochromia

There are three recognizable patterns.

1. Complete heterochromia (heterochromia iridum)

Each eye is a completely different colour, for example one blue and one brown. It is the most visually striking form.

2. Partial or sectoral heterochromia

One part of an iris is a different colour from the rest of the same iris. For example, a section of the iris may be brown in an otherwise blue eye.

3. Central heterochromia

A different-coloured ring around the pupil with another colour in the outer iris, like a gold-green centre with a brown outer ring.

Is Heterochromia When You Have Two Different Coloured Eyes?

Yes, usually. When most people say “heterochromia”, they mean complete heterochromia: two eyes with clearly different colours. Partial and central forms are also considered heterochromia because they both reflect uneven distribution of iris pigment.

What Causes Heterochromia?

Causes fall into two broad groups: present from birth (congenital) and developed later (acquired).

Congenital heterochromia

Genetic variation. Inherited differences in how the melanocytes (pigment cells) populate the iris during development.
Waardenburg syndrome. A genetic condition that can include hearing loss, white hair streak, and heterochromia.
Horner’s syndrome at birth. A nerve condition that can change pigment formation in one eye.
Piebaldism and other rare syndromes.

Congenital heterochromia is usually noticed in childhood and remains stable through life.

Acquired heterochromia

Eye injury. Bleeding, scarring, or inflammation can change iris colour.
Chronic iritis or uveitis. Long-term inflammation can alter melanin distribution.
Fuchs’ heterochromic iridocyclitis. A low-grade chronic inflammation, often affecting one eye, that can change colour slightly.
Certain glaucoma medications. Some drops in the prostaglandin class can darken the iris over years.
Pigmentary glaucoma.
Eye tumours. Iris naevi, melanoma, or other growths can change colour.
Neurological conditions. Horner’s syndrome acquired later in life.
Siderosis. Iron deposits from a retained metal foreign body can change iris colour.

Any iris colour change in adulthood deserves a careful eye examination.

Is Heterochromia Due to Inbreeding?

No. Inbreeding and heterochromia are not linked. Heterochromia is mostly the result of normal genetic variation or specific underlying conditions. It can run in families when it is linked to a particular genetic syndrome, but on its own it does not indicate inbreeding. Unfortunately, online myths around the topic persist, so it is worth restating clearly.

Why Are My Eyes Suddenly Two Different Colours?

A sudden or new change in iris colour, in contrast to lifelong heterochromia, always deserves attention. Possible causes include:

Eye injury with bleeding or scarring
Uveitis or iritis
Fuchs’ heterochromic iridocyclitis
Chronic use of certain glaucoma drops
Iris tumour
Retained metal foreign body
Neurological conditions such as Horner’s syndrome

A full slit-lamp examination at an eye specialist hospital can usually pick up the cause within one visit.

How Rare Is Heterochromia?

Complete heterochromia is quite uncommon, affecting less than 1 per cent of the general population. Partial and central forms are more common, though they often go unnoticed because the two colours are subtle. Heterochromia is also seen in many animals, particularly certain cat and dog breeds.

What Are the Symptoms?

Heterochromia itself has no symptoms beyond the visual difference in eye colour. Any accompanying symptoms usually come from the underlying condition:

Light sensitivity, pain, or redness (inflammation)
Blurred vision (injury, inflammation, tumour)
Pupil size difference (Horner’s syndrome)
Hearing loss or white hair streak (Waardenburg syndrome)
Drooping eyelid with small pupil on one side (Horner’s)
Blind spots, flashes, or changes in visual field (tumour or retinal involvement)

How Is Heterochromia Diagnosed?

Detailed history, including age of onset
Family history and any syndrome features
Eye trauma or surgery history
Full eye examination with a slit lamp
Measurement of pupil size and reaction
Check of iris transillumination
Eye pressure measurement
Dilated fundus examination
Imaging such as OCT or ultrasound if a growth or abnormality is suspected
Systemic review in paediatric cases to check for associated syndromes

How Is Heterochromia Treated?

Heterochromia itself rarely needs treatment. The plan depends on the cause.

Congenital heterochromia: No treatment needed; it is a cosmetic variation.
Post-inflammatory or post-injury changes: Treat the underlying inflammation or injury first.
Glaucoma-drop-induced colour change: Review the medicines with the doctor; sometimes an alternative is chosen.
Iris tumour: Specialist oncological assessment and treatment.
Horner’s syndrome: Investigation of the neurological cause, then treatment.
Systemic syndromes: Multidisciplinary care involving ENT, cardiology, or genetics where needed.

Some patients choose coloured contact lenses for cosmetic reasons, either to match both eyes or to highlight the difference. This should always be done with a proper fit through an eye hospital and with good lens hygiene.

Supportive eye treatments such as lubricating drops help if dryness or low-grade inflammation is part of the picture.

Heterochromia in Children

Parents often notice unequal eye colour in early infancy. Pointers during review include:

Whether the colour difference has been there from birth or recently
Any associated issues like hearing loss, white patch in hair, or lighter skin patches
Any difference in pupil size
Family history of similar findings

Most children with isolated, stable heterochromia need only routine eye checks. Those with additional features often benefit from a paediatric or genetic review.

Living With Heterochromia

For most people, heterochromia is a feature, not a problem. A few practical points:

Protect both eyes from UV with good sunglasses
Attend yearly eye examinations so any change over time is noticed early
Inform any new eye doctor of your heterochromia pattern so it is not mistaken for a sudden change
If using coloured contact lenses, follow the hygiene rules strictly
Avoid unverified “eye colour change” products, which can injure the eye

When Should You See a Doctor?

Book an eye review if:

Iris colour changes in adulthood
One eye suddenly becomes noticeably different from the other
There is pain, redness, or light sensitivity
Vision drops or distorts
A child has heterochromia with hearing issues or other features
You see patches or spots forming within the iris
You use glaucoma eye drops and notice gradual darkening

Heterochromia Care at Vasan Eye Care

Vasan Eye Care has been looking after patients across India since 2002, now as part of ASG Enterprises. With more than 150 super-speciality centres, 500+ ophthalmologists, and over 5,000 trained eye care staff, the team is well placed to assess heterochromia, rule out any underlying condition, and offer practical guidance on routine eye care and, where needed, specialist referrals.

Key Takeaways

Heterochromia means different colours in the iris of one or both eyes.
Three main types are complete, partial (sectoral), and central heterochromia.
Most cases are congenital, isolated, and harmless.
Acquired heterochromia in adulthood deserves a full eye examination.
Treatment is aimed at the underlying cause when one exists, not at the colour itself.
Coloured contact lenses can be used cosmetically, with proper fitting and hygiene.

Frequently Asked Questions

Yes, that is the most recognised form, called complete heterochromia. However, the term also covers partial or sectoral heterochromia, where a section of one iris has a different colour, and central heterochromia, where a different-coloured ring surrounds the pupil. All three patterns reflect uneven distribution of iris pigment.

No. Heterochromia is generally caused by normal genetic variation, specific inherited syndromes, or acquired conditions in the eye. It is not a marker of inbreeding. The belief likely spread through myths online and has no medical basis. If heterochromia appears alongside hearing loss or other unusual features, a genetic review can identify the specific underlying syndrome.

A sudden change in iris colour, in contrast to lifelong heterochromia, usually points to an eye or systemic condition. Possible causes include eye injury, uveitis, Fuchs’ heterochromic iridocyclitis, long-term use of certain glaucoma drops, iris tumours, a retained metal foreign body, or Horner’s syndrome. Any new change should be reviewed promptly by an eye specialist, as an underlying cause may need treatment.

Complete heterochromia affects less than 1 per cent of the general population, which makes it quite uncommon. Partial and central forms are slightly more common, though they often go unnoticed because the colours involved are subtle. Famous people with heterochromia tend to get attention for it, which can make the condition seem more common than it actually is.

References

National Center for Biotechnology Information. Heterochromia Iridis. https://www.ncbi.nlm.nih.gov/books/NBK563131/
American Academy of Ophthalmology. Heterochromia. https://www.aao.org/eye-health/diseases/what-is-heterochromia
WebMD. Heterochromia. https://www.webmd.com/eye-health/heterochromia-iris-colors
Genetic and Rare Diseases Information Center. Waardenburg Syndrome. https://rarediseases.info.nih.gov/diseases/5524/waardenburg-syndrome