Medical interventions for acanthamoeba keratitis

Cochrane: Acanthamoeba are microscopic, free-living, single-celled organisms. Infection of the eye by these organisms is known as Acanthamoeba keratitis (AK). Although very rare, if left untreated AK can lead to the loss of vision in the eye or, in extreme cases, loss of the eye itself. Contact lens wear is the most common risk factor for AK. The most common symptom of AK is severe pain, which is out of proportion to the clinical signs and associated with sensitivity to light, blurry vision, and tearing.

 
Study characteristics
We found one eligible study of 55 participants from the UK. All participants in the study had a history of contact lens wear. The study randomly assigned people with AK to one of two medical treatment options: chlorhexidine eye drops or polyhexamethylene biguanide (PHMB) eye drops. Participants in the study were treated for 51 to 145 days.
 
Key results
In the one study identified, similar results were seen between the chlorhexidine and PHMB groups in terms of resolution of infection, changes in vision, or need for surgery. However, the number of participants in the study was small and the results uncertain; thus, we cannot be confident that there are really no differences between these treatments. No serious side effect was observed with either treatment in the study.
 
Quality of the evidence
Although the study was well-designed with no suggestion of bias, the results must be interpreted carefully because of the small number of participants.

Authors' conclusions: 

There is insufficient evidence to evaluate the relative effectiveness and safety of medical therapy for the treatment of AK. Results from the one included study yielded no difference with respect to outcomes reported between chlorhexidine and PHMB. However, the sample size was inadequate to detect clinically meaningful differences between the two groups as indicated by the wide confidence intervals of effect estimates.