**Core Concept:** Herpes simplex virus (HSV) is a common cause of ocular infections, particularly HSV-1 is responsible for ocular herpes. Topical antiviral agents, like acyclovir, are used for the treatment of HSV keratitis.

**Why the Correct Answer is Right:** Acyclovir is a nucleoside analogue that competitively inhibits viral DNA polymerase, thus preventing viral replication. It is highly effective against HSV and is the first-line treatment for herpes keratitis. Acyclovir is available in topical formulations, making it suitable for ocular use.

**Why Each Wrong Option is Incorrect:**

A. **Acyclovir**: False - Acyclovir is the correct antiviral agent for treating herpes keratitis.
B. **Ganciclovir**: Ganciclovir is a guanosine analogue used primarily for the treatment of cytomegalovirus (CMV) infections, not HSV.
C. **Famciclovir**: Famciclovir is another antiviral drug with a similar mechanism to Acyclovir. However, it is typically used orally, not topically for ocular infections.
D. **Lubricant eye drops**: Lubricant eye drops are used for symptomatic relief of dry eye and not for treating viral infections like HSV keratitis.

**Clinical Pearl:** Topical antiviral therapy, including Acyclovir, is crucial for the treatment of herpes keratitis to prevent progression of the infection, reduce inflammation, and preserve the corneal integrity. Prompt initiation of therapy is essential for a favorable outcome.

**Correct Answer:** B. Famciclovir.