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Viral Keratitis
Cornea
1. Clinical Analogy
Think of the cornea as a transparent brick wall - epithelial cells are the outer mortar, Bowman's is the foundation slab, and the stroma is the load-bearing brickwork. Viruses are molecular saboteurs: HSV-1 dissolves the mortar (epithelial dendrites) and, in deeper disease, dismantles the cement (stromal necrosis or immune interstitial disease). VZV is a more aggressive demolition crew. CMV quietly undermines the foundations (endotheliitis). Adenovirus floods the site temporarily but rarely causes permanent structural damage. The clinician's task: identify which saboteur, at which depth, via which mechanism.
2. Master Classification of Viral Keratitis
| Virus | Disease | Layer | Mechanism | Key Feature |
|---|---|---|---|---|
| Herpes simplex virus type 1 (HSV-1) | Epithelial keratitis | Epithelium | Direct viral cytopathy | • Dendritic / geographic ulcer |
| Herpes simplex virus type 1 (HSV-1) | Non-necrotising stromal (neurotrophic keratopathy (NK)) | Stroma | Primarily host immune response | • Stromal opacity / inflammation • Intact epithelium |
| Herpes simplex virus type 1 (HSV-1) | Necrotising stromal | Stroma | • Viral destruction • Immune-mediated destruction | • Necrosis • Possible vascularisation |
| Herpes simplex virus type 1 (HSV-1) | Endotheliitis | Endothelium | Immune ± direct | • Keratic precipitates (KPs) • Disc oedema • Raised intraocular pressure (IOP) |
| Varicella-zoster virus (VZV) | Herpes zoster ophthalmicus (HZO) keratitis | Epithelium / stroma / endothelium | • Direct viral involvement • Immune-mediated inflammation | • Pseudo-dendrites • Nummular infiltrates |
| Cytomegalovirus (CMV) | Endotheliitis | Endothelium | Direct viral involvement | • Coin-shaped keratic precipitates • Raised intraocular pressure (IOP) |
| Epstein–Barr virus (EBV) | Interstitial keratitis | Variable stromal depth | Mechanism uncertain | • Rare • Peripheral stromal infiltrates involving variable depths • Possible minimal neovascularisation |
| Adenovirus | Epidemic keratoconjunctivitis (EKC) / pharyngoconjunctival fever (PCF) | Epithelium in epidemic keratoconjunctivitis (EKC); subepithelial infiltrates may follow | • Direct epithelial infection • Immune-mediated subepithelial infiltrates | • Subepithelial infiltrates in epidemic keratoconjunctivitis (EKC) |
| Measles virus | Keratitis | Epithelium | Multifactorial | • Children with malnutrition / vitamin A deficiency • Possible secondary infection |
| Vaccinia virus | Post-vaccination | Epithelium / stroma | Direct viral inoculation or spread | • After smallpox vaccination or contact / autoinoculation • Now rare |
| Virus | Disease | Layer | Mechanism | Key Feature |
|---|---|---|---|---|
| Herpes simplex virus type 1 (HSV-1) | Epithelial keratitis | Epithelium | Direct viral cytopathy | • Dendritic / geographic ulcer |
| Herpes simplex virus type 1 (HSV-1) | Non-necrotising stromal (neurotrophic keratopathy (NK)) | Stroma | Primarily host immune response | • Stromal opacity / inflammation • Intact epithelium |
| Herpes simplex virus type 1 (HSV-1) | Necrotising stromal | Stroma | • Viral destruction • Immune-mediated destruction | • Necrosis • Possible vascularisation |
| Herpes simplex virus type 1 (HSV-1) | Endotheliitis | Endothelium | Immune ± direct | • Keratic precipitates (KPs) • Disc oedema • Raised intraocular pressure (IOP) |
| Varicella-zoster virus (VZV) | Herpes zoster ophthalmicus (HZO) keratitis | Epithelium / stroma / endothelium | • Direct viral involvement • Immune-mediated inflammation | • Pseudo-dendrites • Nummular infiltrates |
| Cytomegalovirus (CMV) | Endotheliitis | Endothelium | Direct viral involvement | • Coin-shaped keratic precipitates • Raised intraocular pressure (IOP) |
| Epstein–Barr virus (EBV) | Interstitial keratitis | Variable stromal depth | Mechanism uncertain | • Rare • Peripheral stromal infiltrates involving variable depths • Possible minimal neovascularisation |
| Adenovirus | Epidemic keratoconjunctivitis (EKC) / pharyngoconjunctival fever (PCF) | Epithelium in epidemic keratoconjunctivitis (EKC); subepithelial infiltrates may follow | • Direct epithelial infection • Immune-mediated subepithelial infiltrates | • Subepithelial infiltrates in epidemic keratoconjunctivitis (EKC) |
| Measles virus | Keratitis | Epithelium | Multifactorial | • Children with malnutrition / vitamin A deficiency • Possible secondary infection |
| Vaccinia virus | Post-vaccination | Epithelium / stroma | Direct viral inoculation or spread | • After smallpox vaccination or contact / autoinoculation • Now rare |
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Keep reading Viral Keratitis
11 more sections are included with the Clinical plan.
- Herpes Zoster Ophthalmicus - Overview
- Types of VZV Keratitis
- Management of HZO Keratitis
- CMV Keratitis
- Diagnosis and Management of CMV Endotheliitis
- Adenoviral Keratoconjunctivitis