Acanthamoeba keratitis: a parasite on the rise

Abstract

Purpose: To report a recent significant increase of the number of patients diagnosed with Acanthamoeba keratitis (AK) at Wills Eye Hospital between 2004 and 2005. To determine the risk factors, clinical characteristics, treatments, and outcomes of patients with AK.

Methods: Retrospective consecutive case series of 20 eyes with AK. The information included the incidence from 1995 to 2005, initial and final best-corrected visual acuity (BCVA) at 3-month follow-up, risk factors [contact lenses (CL) history, history of swimming with CL, and exposure to well water and/or contaminated water], clinical characteristics, methods of diagnosis, and treatments.

Results: A statistically significant increased incidence of AK was seen in 2004 and 2005 compared with cases from 1995 to 2003 (P < 0.01). All patients wore CL; 19 of 20 wore frequent-replacement soft CL and used multipurpose disinfecting solutions. Other risk factors were exposure to well water in 40%, swimming with CL in 25%, and overnight wear in 25%. The diagnosis was made by histopathology in 50%, by microbiology in 15%, and by initial classic clinical signs and response to treatments in 35%. Herpes simplex virus was the misdiagnosis in 70%. Patients who presented with dendritiform keratitis or radial keratoneuritis had a BCVA better than 20/30 in 8 of 9 (89%) and patients with ring ulcers or stromal disease who had a BCVA less than finger counting in 5 of 8 (62.5%).

Conclusions: We observed an increased incidence of AK. Patients with proper use of frequent-replacement CL and multipurpose solutions can develop AK. Advanced stromal disease at diagnosis is associated with worse outcome.