Name a topical antiviral used for HSV keratitis, and a key consideration in its use.

• A. Ganciclovir; ocular surface toxicity with prolonged use
• B. Acyclovir; ocular surface toxicity with prolonged use
• C. Trifluridine; ocular surface toxicity with prolonged use
• D. Idoxuridine; ocular surface toxicity with prolonged use

Answer: (C)

Trifluridine is a classic topical antiviral used to treat HSV keratitis. It works by inhibiting viral DNA synthesis, helping to curb the infection in the corneal epithelium. The key consideration with its use is ocular surface toxicity with prolonged use. It can cause corneal epithelial irritation and damage (punctate keratitis, surface toxicity) if used for extended periods, so it’s given in short, intensive courses with careful monitoring, and clinicians may switch to a less toxic option as the infection comes under control. Idoxuridine is an older, more toxic alternative; ganciclovir gel and systemic acyclovir are other options with different safety profiles, but the prominent caution with trifluridine is keeping the exposure short to protect the ocular surface.