Primary infection (herpetic blepharitis)
- Is seen as blepharo conjunctivitis i.e. lid and conjunctival infection that heals without scarring. Corneal involvement is rare.
Recurrent eye infection
- Due to virus reactivation in a latent infected sensory ganglion, transport of the virus to sensory nerve endings, and subsequent infection of ocular surface.
- The following classification of herpes simplex keratitis is important for understanding this disease:
- Dendritic ulcer (Epithelial keratitis)
- A classic lesion consisting of a linear branching corneal ulcer (dendritic ulcer). The underlying cornea has little inflammation.
- Symptoms of foreign-body sensation, light sensitivity, redness and blurred vision.
- Local or diffuse reduction in corneal sensation develops following recurrent epithelial keratitis.
- Disciform keratitis (Stromal keratitis)
- Is seen as a disc-shaped area of corneal edema. Longstanding edema leads to permanent scarring and is the major cause of decreased vision connected with herpes.
- Caused by Localized endothelitis, the localized inflammation of corneal endothelial layer.
- Other forms
- Metaherpetic ulcer results from inability of the corneal surface to heal.
- Necrotizing keratitis.
- Keratouveitis: granulomatous uveitis with large keratic deposits on the corneal endothelium.