Chlorhexidine 0.02% or polyhexamethylene biguanide 0.02% as the main treatment for Acanthamoeba keratitis

To report medical cure and treatment failure rates of Acanthamoeba keratitis (AK) with respect to type of treatment, disease stage and prognostic factors.

Electronic records were reviewed for 45 patients with PCR-positive AK treated at the Department of Ophthalmology, Aarhus University Hospital, Denmark from 2012 to 2025. Patients received standardized treatment with either polyhexamethylene biguanide (PHMB) 0.02% (n = 27) or chlorhexidine 0.02% (n = 18) both in combination with propamidine 0.1%. Evaluated risk factors included disease stage, patient age, time to diagnosis and prior corticosteroid use.

All 29 patients (64%) presenting with stage 1 or 2 disease achieved medical resolution of the infection, irrespective of the treatment regimen. Sixteen patients (36%) presented with stage 3 disease. Twelve of these patients underwent therapeutic keratoplasty and were considered treatment failures. The overall proportion of treatment failures was comparable between groups. Among medically cured patients, the average treatment duration was significantly lower in chlorhexidine- than in PHMB-treated patients (118 vs. 233 days); however, this group also presented with a shorter diagnostic delay. All 12 cases of treatment failure occurred in patients who had received corticosteroid treatment prior to diagnosis and were significantly older than patients achieving medical cure.

PHMB 0.02% and chlorhexidine 0.02% in combination with propamidine 0.1% demonstrated comparable clinical outcomes in the treatment of AK, although the average treatment duration was shorter in chlorhexidine-treated eyes. Steroid use before diagnosis and older patient age are significantly associated with higher risk of treatment failure.