(HealthDay)—Fungal keratitis patients pretreated with antifungal medication appear to have worse outcomes, according to a study published online June 21 in Clinical & Experimental Ophthalmology.

Catherine Q. Sun, M.D., from the University of California, San Francisco, and colleagues conducted a randomized , double-blind trial to determine the optimal treatment for filamentous fungal keratitis. Patients at the Aravind Eye Care System in India were randomized to treatment with either topical natamycin or voriconazole.

The researchers found that 44 percent of the 323 patients enrolled presented on an antifungal agent. Larger mean baseline infiltrate size and epithelial defect size were seen in pretreated . Pretreatment was associated with significantly worse three-month visual acuity, larger three-month scar size, and increased odds of corneal perforation and/or transplant in multivariate analysis.

"Fungal keratitis that is smear-positive despite being pretreated with appropriate antifungal agents appears to be a risk factor for worse outcomes, likely due to initial ulcer severity and failure," conclude the authors.

The drugs used in the study were donated by Alcon and Pfizer.