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Acanthamoeba Keratitis — SCE Infectious Diseases MCQ

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HardInfection Prevention & ControlAcanthamoeba KeratitisSCE Infectious Diseases

A 40-year-old man is diagnosed with Acanthamoeba keratitis. He is a contact lens wearer who swam while wearing lenses. Confocal microscopy shows Acanthamoeba cysts in the cornea. What is the first-line treatment?

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Correct answer: A — Polyhexamethylene biguanide (PHMB) 0.02% plus Propamidine isethionate 0.1% (Brolene) — topical combination anti-amoebic therapy applied hourly initially

Acanthamoeba keratitis is a sight-threatening corneal infection associated with contact lens wear (particularly with poor hygiene, tap water exposure, or swimming with lenses). Treatment is topical anti-amoebic therapy: PHMB (polyhexamethylene biguanide) 0.02% or Chlorhexidine 0.02% PLUS Propamidine isethionate 0.1% (Brolene), applied hourly for the first 48 hours then gradually reduced. Treatment duration is typically 3–6 months due to the resistance of Acanthamoeba cysts to therapy. The initial diagnosis is often delayed as it mimics HSV keratitis.

Reference: RCOphth 2023 – Acanthamoeba keratitis; NICE CKS 2024 – Contact lens complications