Which topical antiviral is commonly used for dendritic keratitis?

• A. Ganciclovir
• B. Acyclovir
• C. Trifluridine
• D. Foscarnet

Answer: (C)

Topical antiviral therapy for epithelial herpes simplex keratitis relies on a drug that actively stops HSV DNA synthesis in the corneal epithelium. Trifluridine is the classic topical agent used for dendritic keratitis because it is a potent thymidine analogue that, once inside infected cells, is phosphorylated to an active form that inhibits viral DNA polymerase and incorporates into viral DNA, leading to termination of DNA synthesis. This direct action on the infected corneal epithelium helps rapidly halt viral replication and promotes healing of the characteristic dendritic ulcers.

Its potent activity against HSV-1 and good ocular surface penetration make it a go-to choice for epithelial involvement. Dosing is frequent to maintain therapeutic levels since the corneal epithelium turns over quickly and viral replication is rapid. Side effects are mainly local irritation and punctate epithelial keratopathy due to its toxicity to the ocular surface, so treatment requires careful monitoring.

Other topical antivirals can be used, but they are not as consistently effective for acute dendritic keratitis. Acyclovir topical has slower onset and limited penetration, and while ganciclovir is active, trifluridine remains the most traditional first-line option for this presentation. Foscarnet is typically reserved for acyclovir-resistant cases or systemic use, not routine topical therapy for dendritic keratitis.