Acanthamoeba
Key points
- Acanthamoeba is found in water and soil.
- Recent studies have found Acanthamoeba to be present in around one third of domestic sinks in the South East of England, where it has an affinity for the bacteria associated with high levels of calcium deposition.
- Since 2011, the use of Oxypol in contact lens solutions has been associated with the rise in cases of Acanthamoeba keratitis.
- Acanthamoeba infects the cornea to cause an initial epitheliopathy, perineural infiltrates and a subsequent stromal involvement. In around 20%, the late stage stromal infiltrate is ring-shaped. Direct infection beyond the cornea is not found.
- About 50% of Acanthamoeba keratitis begins with dendritic epithelial lesion and may therefore mimic Herpes simplex keratitis.
- Active corneal infection may persist for up to 12 months.
- 90% of infection is due to avoidable risk factors, most importantly as water exposure with contact lens wearers.
- Acanthamoeba keratitis is rare and affects about 2 per 100,000 contact lens wearers per year, about 20 times less common than bacterial keratitis.
- Acanthamoeba keratitis is less common with daily wear regimes but may still occur.
- Suspect Acanthamoeba keratitis warrants same day referral to hospital for confirmation and treatment (with anti-amoebic drops).