👁️ Heterochromia — a difference in iris colour between the two eyes or within one eye. Usually benign, but occasionally a sign of underlying systemic or ocular disease. ⚠️ Neuroblastoma (childhood) and melanoma (later life, with dark iris spot) are rare but important causes of acquired heterochromia.

🌈 About

Heterochromia means different eye colours or multi-toned irises within one eye.
Usually harmless and may be congenital or acquired.
Common in animals (e.g. huskies, cats), rare in humans.

🧬 Types

🔹 Complete heterochromia: Each eye a different colour (e.g., one blue, one brown).
🔸 Sectoral / partial heterochromia: Segment of one iris differs in colour (as below).
🔹 Central heterochromia: Inner ring around pupil differs from outer iris colour.

🎨 Split Iris (Sectoral Heterochromia)

Example of partial heterochromia — a wedge of lighter pigment within one iris.

👶 Heterochromia in Infancy — Causes

🌈 Benign (physiological) heterochromia — normal pigment variation.
🦋 Horner’s syndrome (congenital) — smaller pupil (miosis), mild ptosis, lighter iris.
🧠 Sturge–Weber syndrome — facial port-wine stain, glaucoma risk.
🎧 Waardenburg syndrome — white forelock, broad nasal root, deafness.
🧬 Piebaldism — patchy albinism of skin and hair.
🚼 Hirschsprung disease — may co-occur in syndromic forms (e.g., Waardenburg type IV).
🌀 Bloch–Sulzberger syndrome (Incontinentia pigmenti).
📘 Neurofibromatosis (von Recklinghausen disease).
🍃 Tuberous sclerosis (Bourneville disease).
🕊️ Parry–Romberg syndrome — facial hemiatrophy, sometimes with iris pigment loss.

🧑‍⚕️ Waardenburg Syndrome (example)

Note iris colour variation, white forelock, and characteristic facial features.

⚡ Acquired Heterochromia — Causes

🩸 Eye trauma or post-surgical pigment change.
🧠 Neuroblastoma (childhood) — tumour of sympathetic chain; may present with unilateral Horner’s syndrome.
🦠 Inflammation: Iritis, uveitis, Fuchs’ heterochromic cyclitis.
💊 Medications: Prostaglandin analogues for glaucoma (e.g., latanoprost, bimatoprost, “Latisse”).
🌀 Glaucoma or pigment dispersion syndrome.
🎯 Melanoma or melanocytoma of the iris — often darkened, irregular patch.
💉 Bleeding (hyphema) or iron deposition post-injury.
🧩 Horner’s syndrome (acquired) — lighter iris on affected side.
💧 Posner–Schlossman syndrome — recurrent uveitic glaucoma.
🧬 Chediak–Higashi syndrome — albinism, immune defects.
⚡ Diabetes / CRVO — rare secondary pigment changes.

🩺 Clinical Evaluation

Assess onset, laterality, visual acuity, photophobia, pain.
Look for pupil asymmetry, eyelid ptosis (Horner’s), or signs of uveitis/glaucoma.
Use slit-lamp examination to confirm iris pigment change (not reflection or shadow).

🧭 Management

👶 At birth: Discuss with paediatrician; often benign pigment development, but consider ophthalmology referral.
🧑‍⚕️ Later in life: Refer to ophthalmologist if new or changing heterochromia to exclude melanoma or uveitis.
⚕️ Treat underlying cause if identified (infection, inflammation, or trauma).
📸 Baseline photograph — useful for monitoring progression.

💡 Teaching tip: - Congenital = likely benign (esp. stable since infancy). - Acquired = always investigate (rule out tumour, inflammation, or trauma). - Horner’s syndrome can be recognised by triad: ptosis + miosis + anhidrosis ± lighter iris.

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Heterochromia Iridium