Heterochromia: UK guide to different coloured eyes

Quick answer: heterochromia means the irises are different colours, or one iris has more than one colour. If it has been there since early childhood and nothing else is wrong, it is usually harmless. A new colour change in an adult, a growing iris spot, or colour change with pain, redness or a different pupil size should be checked by an eye specialist.

Heterochromia is famous for its associations with celebrities and animals. Most cases are congenital and completely benign. What matters clinically is whether the difference has always been there, or has developed over time.

Types of heterochromia

Complete heterochromia — each eye is a completely different colour (for example, one blue, one brown).

Sectoral (partial) heterochromia — a patch of a different colour within one iris.

Central heterochromia — the inner ring around the pupil is a different colour to the outer iris. Very common and often mistaken for a distinct eye colour.

Harmless or worth checking? A quick guide

- Likely harmless: present in baby photos, stable for years, no other eye symptoms, normal vision.

- Worth a routine appointment: you are unsure whether it is new, or you have started glaucoma drops and noticed darkening.

- Seek prompt review: a new difference as an adult, a spot that is growing or changing shape, or colour change with pain, redness, light sensitivity, a smaller pupil or a drooping eyelid.

Old photographs are useful: compare close-up pictures from several years ago in daylight and bring them to your appointment.

Congenital heterochromia — usually harmless

In most cases, heterochromia is present from birth or emerges in infancy as pigment develops. It is either isolated or part of a benign genetic pattern. No treatment is needed and no ongoing surveillance is required.

Occasionally congenital heterochromia is a marker for a syndrome:

- Waardenburg syndrome — hearing loss, white forelock, wide-set eyes

- Sturge-Weber syndrome — facial port-wine stain, glaucoma

- Horner's syndrome from birth — smaller pupil and hypopigmented iris on the affected side

Acquired heterochromia — needs investigation

A change in iris colour in adulthood is different. Causes include:

- Trauma — iris atrophy after a blunt injury

- Fuchs heterochromic uveitis — a chronic low-grade inflammation causing gradual lightening of the affected iris

- Pigment dispersion — heavier pigmentation on the anterior iris surface

- Iris tumours — melanocytoma, melanoma. Rare but must not be missed.

- Latanoprost and similar glaucoma drops — darken the iris slowly over months

- Horner's syndrome acquired in early childhood — can lighten the iris on the affected side

Heterochromia in babies and children

Eye colour often keeps changing during the first year or so of life, so a mild difference in a baby may settle. Ask your GP or health visitor to arrange assessment if the difference is marked, appears with a smaller pupil or droopy eyelid, or comes with a white forelock or hearing concerns.

When to seek review

- New difference in iris colour in an adult

- Any pigmented spot on the iris that is growing or changing shape

- Iris colour change with pain, redness, or light sensitivity

- Difference in pupil size accompanying the colour change

- One drooping eyelid alongside a smaller pupil (possible Horner's)

Sudden loss of vision or a painful red eye needs same-day urgent care — contact NHS 111 or an eye casualty service rather than waiting for a routine appointment.

Investigation

A slit-lamp examination is the mainstay. Anterior segment imaging (UBM, AS-OCT) and iris photography document changes over time. Suspected iris tumours are referred to a specialist ocular oncology service.

Book a consultant-led iris assessment

If you have noticed a change in your eye colour, an iris spot, or new pigment, book a consultation with my private practice or call 020 3137 3237. An initial telephone call is free; a clinical consultation costs £250, charged separately from any treatment.