Corticosteroids as a therapy for bacterial keratitis: an evidence-based review of 'who, when and why'

Corticosteroids have been proposed as an adjunct to antibiotics for the treatment of bacterial keratitis, with significant controversy regarding the appropriate use of this therapy. Recent prospective randomised controlled trials have provided additional evidence to guide clinical decision-making. A review of the epidemiology and mechanisms of pathogenesis, preliminary animal studies, retrospective human studies and prospective randomised clinical trials that address the potential risks and benefits of corticosteroids in patients with bacterial keratitis was performed. Four prospective randomised controlled trials were identified. Three small studies found no benefit of topical corticosteroids, but were underpowered to evaluate adverse events. The Steroids for Corneal Ulcers Trial (SCUT) study and subgroup analyses provide evidence for a relative gain of one line of best spectacle-corrected visual acuity in patients with non-Nocardia bacterial keratitis, especially when corticosteroids were initiated within 3 days of presentation; no increase in adverse events was noted. No evidence was found to support the concern for corneal thinning attributable to corticosteroids in the absence of an inadequately treated infectious process. In patients with culture-proven non-Nocardia bacterial keratitis, corticosteroids provide one line of vision improvement over antimicrobials alone, with no increase in adverse events. This benefit should not be extrapolated to patients with other aetiologies of keratitis, such as fungus, herpes viruses, acanthamoeba or atypical mycobacteria, and these entities should be excluded before considering adjunctive steroid therapy.