Acanthamoeba is a free-living protozoan mainly found in water and soil. Like other protozoa, it exists as a motile, feeding trophozoite which when in danger turns into a cyst (Fig 1). The cystic form is double walled and resistant to extreme temperatures, desiccation and antimicrobial agents. Although Acanthamoeba keratitis (AK) accounts for less than 1% of all infective keratitis overseas, the incidence in New Zealand has been on the rise. This is thought to be primarily due to the increasing use of contact lenses, which account for more than 95% of cases. Interestingly, in India, less than 1% of Acanthamoeba keratitis is contact lens related, which is explained by the low prevalence of contact lens wear and the widespread use of contaminated water in the country’s rural areas.
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