Acanthamoeba Keratitis: Analysis of Risk Factors, Diagnostic Modalities, and Clinical Outcomes at a Tertiary Referral Ophthalmic Unit.

Abstract

Purpose: The aim of this study was to analyze the risk factors, clinical features, and diagnostic tests of Acanthamoeba keratitis and to evaluate clinical outcomes with polyhexanide (PHMB) 0.06% monotherapy.

Methods: This study was s retrospective case series of eyes with Acanthamoeba keratitis from January 2020 to April 2023. All patients were investigated with smear microscopy, microbial culture (MC), polymerase chain reaction (PCR), and in vivo confocal microscopy (IVCM) and were commenced on treatment with PHMB 0.06% monotherapy.

Results: A total of 149 eyes were included. 93.2% were contact lens (CL) wearers, with the most common risk factor being water exposure to CL (71.2%, 99/139). 6.7% of eyes (10/149) were correctly diagnosed with AK at presentation, with the most common alternative diagnosis being bacterial keratitis (48.3%). The median time from symptom onset to diagnosis was 30 days. When compared with a composite diagnosis reference standard, the sensitivities of IVCM, PCR, and MC were 0.97, 0.49, and 0.13, respectively. Medical treatment success was achieved in 91.9% of eyes (138/149), with a further 2.7% (4/149) requiring surgery to achieve treatment success. The overall treatment failure rate was 4.7% (7/149). Prediagnosis steroid use (P < 0.0002), AK relapse (P < 0.0001), scleritis (P < 0.0001), ring infiltrate at diagnosis (P < 0.02), and delayed diagnosis (P < 0.03) were all poor visual prognostic factors.

Conclusions: PHMB 0.06% monotherapy is highly effective in treating Acanthamoeba keratitis, achieving a medical cure in 91.9% of eyes. CL water exposure remains the leading risk factor. While IVCM is the most sensitive diagnostic tool, its limited availability means that clinical judgment in the context of relevant risk factors remains essential for timely diagnosis and treatment.