## Diagnosis: VZV Stromal Keratitis **Key Point:** VZV stromal keratitis is a deeper corneal inflammation (unlike HSV epithelial keratitis) that presents with stromal infiltration, neovascularization, and anterior uveitis. It often occurs during recurrent herpes zoster ophthalmicus. ## Drug of Choice: Acyclovir ### Why Acyclovir for VZV Stromal Disease? 1. **Systemic Penetration:** VZV stromal keratitis requires systemic antiviral therapy because the infection involves deeper corneal layers and anterior uveal tissue. Acyclovir achieves therapeutic levels in aqueous humor and corneal stroma when given orally or intravenously. 2. **Efficacy:** Acyclovir is highly effective against VZV and reduces the duration and severity of stromal inflammation. 3. **Dosing for VZV Stromal Keratitis:** - **Systemic:** 800 mg orally 5 times daily for 7–14 days (or IV acyclovir 10–15 mg/kg every 8 hours for severe disease) - Topical acyclovir ointment may be added for epithelial involvement **High-Yield:** Acyclovir is preferred for VZV stromal keratitis because it crosses the blood–aqueous barrier better than topical agents and provides sustained antiviral coverage in the stroma and uveal tissue. ## Topical Antivirals: Limited Role in Stromal Disease | Agent | Mechanism | Use in VZV Stromal Keratitis | Limitation | |-------|-----------|-------------------------------|------------| | Acyclovir (systemic) | DNA polymerase inhibitor | First-line for stromal disease | Requires systemic dosing | | Trifluridine (topical) | Nucleoside analogue | Epithelial VZV keratitis only | Poor stromal penetration | | Vidarabine (topical) | Nucleoside analogue | Epithelial HSV/VZV keratitis | Minimal stromal penetration | | Penciclovir (topical) | Nucleoside analogue | Epithelial HSV keratitis | Not preferred for VZV; poor stromal penetration | **Clinical Pearl:** VZV stromal keratitis often requires **concurrent topical corticosteroids** (in addition to systemic acyclovir) to suppress the inflammatory response. This is in contrast to HSV epithelial keratitis, where steroids are avoided. The combination of systemic acyclovir + topical corticosteroids + topical cycloplegic agents is standard for VZV stromal disease. ## Adjunctive Therapy - **Topical corticosteroids:** Prednisolone acetate 1% 4–6 times daily (essential for stromal inflammation) - **Cycloplegic agents:** Cyclopentolate 1% for pain and to prevent posterior synechiae - **Lubricating drops:** For comfort and to prevent exposure keratopathy **Warning:** Do not use topical corticosteroids without systemic antiviral coverage in VZV keratitis—risk of viral dissemination. Always pair steroids with acyclovir.
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