Which is the first-line topical antifungal for fungal keratitis?

• A. Amphotericin B
• B. Natamycin
• C. Voriconazole
• D. Ketoconazole

Answer: (B)

Starting treatment with the right agent hinges on matching the drug’s spectrum to the fungi most often causing keratitis and how well it works on the corneal surface. Natamycin at a 5% suspension is the best choice because it has strong activity against the filamentous fungi that most commonly cause fungal keratitis, such as Fusarium and Aspergillus. It provides reliable initial control of surface and stromal infection and has a well-established track record in improving healing and outcomes when started promptly.

Other antifungals have limitations in this setting. Amphotericin B works well against yeasts like Candida but is less consistently effective against filamentous fungi responsible for keratitis. Voriconazole has broad coverage and good corneal penetration, but randomized experience shows it often performs less well than natamycin as initial therapy for filamentous keratitis. Ketoconazole is limited by poor corneal penetration and overall efficacy in this eye infection. So, natamycin remains the preferred first-line topical antifungal for fungal keratitis.