In this interview from AAO 2014, Dr. Thomas Lietman describes the surprising results from his recent study that compared topical natamycin and voriconazole in the treatment of filamentous fungal keratitis. This phase 3, double-masked trial enrolled more than 300 patients with smear-positive filamentous fungal ulcer and visual acuity of 20/40 to 20/400. Natamycin treatment provided significantly better clinical and microbiological outcomes than voriconazole, leading to improved visual acuity and lower risk of perforation. The study showed that voriconazole should not be used as monotherapy in filamentous keratitis.