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

Abstract

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.

Keywords: acanthamoeba; contact lens; in vivo confocal microscopy; keratitis.