Free living amoebae (FLA) keratitis

Abstract

PurposeTo describe the clinical features and treatment results in 41 consecutive patients with microbiologically proven free‐living amoebae (FLA) keratitis.MethodsCorneal scrapings from patients with suspected amoebic keratitis were plated on non‐nutrient agar. Amoebic isolates were identified morphologically and by polymerase chain reaction (PCR). All patients were treated with polyhexamethylene biguanide (PHMB) 0.02% eye‐drops.Results41 corneal scrapings from 41 patients were found to be culture‐positive for FLA; 39 (95%) were from contact lens (CL) wearers, 2 (5%) from non‐CL wearers. Microscopic examination identified 3 Acanthamoeba spp, 23 Hartmannella spp, 12 Vahlkampfiidae, and 3 mixed infections with Hartmannella/Vahlkampfiidae. Morphological results were confirmed by PCR. Patients with Acanthamoeba, Hartmannella and Vahlkamfiidae keratitis had indistinguishable clinical features. In 37 eyes with keratitis at an early stage, treatment with PHMB 0.02% eye‐drops was fully successful. In 4 patients with advanced keratitis, topical PHMB 0.02% controlled the infection, but all of them developed a central corneal scar with visual deterioration.ConclusionsAcanthamoeba is not the only cause of amoebic keratitis, because this condition may also be caused by other FLA, such as Hartmannella and Vahlkampfiidae. This finding is epidemiologically interesting, suggesting a possible different geographical prevalence of the different FLA responsible for keratitis. Early diagnosis and proper anti‐amoebic treatment are crucial to yield a cure.