## Herpes Simplex Keratitis — Dendritic Ulcer **Key Point:** The dendritic ulcer is the pathognomonic finding of HSV epithelial keratitis, caused by direct viral cytolysis of corneal epithelial cells. ### Morphology of the Dendritic Ulcer - **Shape:** Tree-like branching pattern with a central ulceration - **Terminal bulbs:** Swollen, club-shaped ends at the tips of the branches (hallmark) - **Staining:** Stains with fluorescein (ulcer base) and rose bengal or lissamine green (infected epithelium at margins) - **Size:** Typically 1–2 mm in diameter, though may coalesce into larger lesions ("amoeboid" or "geographic" ulcer if recurrent) ### Pathophysiology 1. Viral replication in corneal epithelial cells 2. Cell lysis and necrosis → ulceration 3. Spread along nerve axons → branching pattern 4. Terminal bulbs represent active viral replication at the ulcer margin ### Clinical Stages of HSV Keratitis | Stage | Finding | Duration | |-------|---------|----------| | **Epithelial** | Dendritic ulcer | 1–2 weeks | | **Stromal** | Stromal infiltration, edema, neovascularization | Weeks to months | | **Endothelial** | Disciform keratitis, Descemet's folds, anterior chamber reaction | Chronic | **High-Yield:** The dendritic ulcer is virtually diagnostic of HSV-1 epithelial keratitis. Recurrent episodes may present as amoeboid or geographic ulcers due to prior scarring. **Clinical Pearl:** Topical antivirals (acyclovir, ganciclovir, trifluridine) are first-line treatment for epithelial HSV keratitis. Topical corticosteroids are contraindicated in epithelial disease (risk of geographic ulcer) but may be used cautiously in stromal/endothelial disease under ophthalmology supervision. **Mnemonic:** **DENDRITIC** — Dendritic ulcer, Epithelial involvement, Necrosis of cells, Dendritic pattern with terminal bulbs, Replication in epithelium, Infected margins stain with vital dyes, Terminal bulbs are swollen, Infectious viral particles, Central ulceration. [cite:Krachmer Corneal Disease 3e Ch 5] 
Sign up free to access AI-powered MCQ practice with detailed explanations and adaptive learning.