Despite their popularity, topical steroids can confound the management of some keratitis patients, as the anti-inflammatory component masks the clinical course of the infectious activity, hindering treatment. Authors of a recent study reviewed the clinical features and visual outcomes of patients with severe corneal ulcers who were prescribed topical corticosteroids, as well as antibiotic eye drops, to assess its impact.

Out of 200 eyes of 197 patients with infectious keratitis reviewed over a four-year span, 14 eyes were treated with topical steroids before a culture-proven diagnosis. All patients were prescribed the steroid for keratitis owing to unresponsive empirical antibiotic therapy, and at least six patients were treated for stromal keratitis due to herpes simplex virus.

Based on the culture results, Acanthamoeba keratitis (AK) was diagnosed in six patients, fungal keratitis (FK) in two patients and bacterial keratitis in two patients; the remaining four were of unknown cause. Two patients with non-bacterial keratitis had unfortunate clinical courses and poor visual outcomes. From the information in the referral letters, at least six of the 14 patients were treated with either acyclovir or valaciclovir, along with topical corticosteroids.

The authors found steroid use did not affect the visual prognoses in the eyes with bacterial keratitis; however, vision was lost in two eyes with fungal keratitis. Two of the six Acanthamoeba keratitis eyes also lost vision.

“In the Acanthamoeba keratitis patients, as well as in two fungal keratitis patients and two unknown keratitis patients, one of the reasons for the undesirable visual prognosis could be the delay in proper diagnosis caused by the masked clinical findings and the reactions to the empirical use of topical antibiotics and corticosteroids,” the authors noted in their paper on the study.

The study concludes that microbiological evidence, as well as a differential diagnosis of herpetic stromal keratitis, is needed when prescribing a topical steroid for suspected infectious keratitis.

“It is important to evaluate the patient for fungal keratitis and Acanthamoeba keratitis before deciding on the use of topical corticosteroids for the treatment of the keratitis,” the authors concluded. “Because correct differentiation of bacterial or fungal keratitis by the clinical signs or findings is difficult even for a corneal specialist, it is important to make a biologically proven diagnosis by smear and culture before prescribing topical corticosteroids. In addition, it is important to stop the application of topical corticosteroids immediately when keratitis does not improve by these steroids.”

Hirano K, Tanaka H, Kato K, Araki-Saasaki K. Topical Corticosteroids for Infectious Keratitis Before Culture-Proven Diagnosis. Clin Ophthalmol. February 16, 2021. [Epub ahead of print].