Purpose: To describe an outbreak of Acanthamoeba keratitis (AK) cases among contact lens wearers.
Design: Retrospective cohort study.
Methods: Patients with AK were included. Relevant demographic and clinical data were obtained from case records, and patients were interviewed using a standardized questionnaire. Contact lens practices, including type of contact lens and solution used, were noted. In addition, clinical features at presentation, management, and clinical outcomes were recorded.
Results: Forty-two patients (affecting 43 eyes) treated between 2000 and 2007 were included. Diagnosis was made by microbiologic culture in 35 cases and by microbiologic and histologic analysis in 2 cases, whereas the remainder were diagnosed based on clinical features and response to treatment. There was a gradual increase in cases since 2005, with a sharp increase in 2007, when 8 local patients were treated. Of 30 patients where contact lens solution data were available, 18 reported using a Complete brand Multipurpose solution (Advanced Medical Optics, Santa Ana, California, USA) before the infection. Among resident cases treated since February 2006, 7 (63%) of 11 patients used a Complete brand solution. Suboptimal hygiene practices were found in all patients interviewed. Fifteen patients required corneal grafting, with 11 undergoing therapeutic deep lamellar keratoplasty (DLK), 2 undergoing optical penetrating keratoplasty (PK), 1 undergoing optical DLK, and 1 undergoing therapeutic PK. The remainder were treated successfully medically with combination antiamebic therapy. The average duration of therapy was 116.2 days (range, 15 to 283 days). Of patients with radial keratoneuritis with or without epithelial disease, 83.3% achieved final vision of 20/40 or better, whereas this was achieved in 41.7% of those with ring infiltrate. Twenty-five percent of patients with ring infiltrate had final visual acuity of counting fingers or worse, whereas no patient with keratoneuritis and epithelial disease had final vision worse than counting fingers.
Conclusions: There was an increase in the number of contact lens users with AK seen in the major eye departments of Singapore. Most of our patients also reported using a Complete brand Multipurpose solution before infection, and this parallels a similar outbreak in the United States. Increasing severity of infection was associated with worse visual outcome.