A 48-year-old man with a history of recurrent HSV keratitis presents with right eye pain, photophobia, and blurred vision for 3 days. Slit-lamp examination shows a central corneal opacity with stromal infiltration and anterior chamber reaction (2+ cells). Fluorescein staining reveals a faint dendritic pattern at the edge of the opacity. What is the most likely diagnosis and the most appropriate management?

Explanation

## Diagnosis: HSV Stromal Keratitis **Key Point:** The combination of **stromal infiltration**, **anterior chamber reaction**, **central corneal opacity**, and **faint dendritic pattern at the edge** in a patient with recurrent HSV keratitis indicates **HSV stromal keratitis** (immune-mediated, not primarily viral replication). ## Pathophysiology of HSV Stromal Disease ### Mechanism 1. Viral antigen persists in the stroma after epithelial healing 2. Immune complexes (IgG, IgM) deposit in the stroma 3. Complement activation and T-cell infiltration cause inflammation 4. Results in stromal necrosis, vascularization, and scarring **Clinical Pearl:** Stromal HSV keratitis is **immune-mediated**, not primarily infectious. The faint dendritic pattern at the edge represents the advancing border of immune inflammation, not active viral replication. ## Management Algorithm ```mermaid flowchart TD A[HSV Stromal Keratitis]:::outcome --> B{Severity?}:::decision B -->|Mild-moderate| C[Topical corticosteroids<br/>+ Systemic acyclovir]:::action B -->|Severe/vision-threatening| D[High-dose topical corticosteroids<br/>+ Systemic acyclovir<br/>± Oral corticosteroids]:::action C --> E[Monitor for recurrence]:::action D --> F[Ophthalmology referral]:::action E --> G[Healing with reduced scarring]:::outcome ``` ## Treatment Regimen ### First-Line Therapy | Component | Dosing | Rationale | |---|---|---| | **Topical corticosteroids** | Dexamethasone 0.1% QID (or stronger if severe) | Suppresses immune-mediated inflammation; safe in stromal disease because viral replication is not active | | **Systemic acyclovir** | 400 mg PO five times daily for 7–10 days | Suppresses any residual viral replication and prevents epithelial recurrence | | **Topical lubricants** | Preservative-free tears QID–QID | Prevents secondary epithelial breakdown | ### Adjunctive Therapy (if severe) **High-Yield:** Oral corticosteroids (prednisolone 0.5–1 mg/kg/day tapered over 4–6 weeks) may be added in severe stromal keratitis with significant vision loss, but ONLY with concurrent systemic antivirals to prevent epithelial recurrence. ## Why Corticosteroids Are Safe Here (Unlike Epithelial Disease) **Mnemonic: STROMAL ≠ EPITHELIAL** - **S**tromal disease = immune-mediated (steroids help) - **T**hick infiltration = not active viral replication - **R**ecurrent in nature = requires antivirals - **O**pacity central = not spreading epithelially - **M**edium-term inflammation = steroid-responsive - **A**ntiviral cover mandatory (prevents epithelial flare) - **L**ow risk of geographic ulcer (stromal, not epithelial) In contrast, epithelial HSV keratitis has active viral replication in the epithelium; steroids promote geographic spread. [cite:Khurana Comprehensive Ophthalmology Ch 5; Yanoff & Duker Ophthalmology 5e Ch 4]