The rising tide of Acanthamoeba keratitis in Auckland, New Zealand: a 7‐year review of presentation, diagnosis and outcomes (2009–2016)

Importance Acanthamoeba is an increasingly prevalent cause of vision‐threatening microbial keratitis. Background To assess the incidence, clinical presentation, diagnosis and outcomes of patients with Acanthamoeba keratitis (AK) in Auckland, New Zealand over a 7‐year period. Design Retrospective observational consecutive case series. Participants Fifty‐eight eyes of 52 patients diagnosed with AK. Methods All cases of AK were identified using a cross‐referenced search of clinical, laboratory and pharmacy records from March 2009 to May 2016. Main Outcome Measures Demographic and clinical data were collected including age, gender, risk factors, clinical manifestations, initial diagnosis, diagnostic investigations, treatment, presenting and final visual acuity and surgical interventions. Results Contact lens (CL) use was noted in 96% of unilateral and 100% of bilateral cases. The mean duration of symptoms at presentation was 21 days and the mean duration from presentation to definitive diagnosis was 14 days. Initial diagnosis was recorded as CL‐related keratitis in 70.6%, viral keratitis in 15.5% and AK in 12.0%. The diagnosis was confirmed with In vivo confocal microscopy (IVCM) in 67.2%, corneal scrape in 22.4%, corneal biopsy in 1.7% and clinically in 8.6%. IVCM sensitivity was 83.0%. Surgical intervention was required in four patients, all with delayed diagnosis (range 63–125 days). The incidence of AK has more than doubled when compared with the preceding 7‐year period. Conclusions and Relevance AK is a rare vision‐threatening protozoal infection with rapidly‐increasing incidence in New Zealand, predominantly affecting CL users. Diagnosis is often challenging and when delayed is associated with worse outcomes. IVCM offers rapid diagnosis with high sensitivity.