Herpes Simplex Karetitis
Herpes simplex virus (HSV) keratitis is the most frequent cause of corneal blindness in the United States and the most common source of infectious blindness in the Western world. The prognosis in HSV keratitis, however, is generally favorable with aggressive treatment.
Signs and symptoms
Patients with HSV keratitis may complain of the following:
The earliest sign of active viral replication in the corneal epithelium is the development of small, raised, clear vesicles.
Dendritic ulcers are the most common presentation of HSV keratitis. Prominent features of a dendritic ulcer include a linear branching pattern with terminal bulbs, swollen epithelial borders, and central ulceration through the basement membrane.
The earliest signs of neurotrophic keratopathy include an irregular corneal surface and punctate epithelial erosions. These erosions may progress to a persistent epithelial defect and eventual stromal ulceration.
Necrotizing stromal keratitis is characterized by dense stromal infiltrate, ulceration, and necrosis. Immune stromal keratitis (ISK) may present clinically with focal, multifocal, or diffuse cellular infiltrates; immune rings; neovascularization; or ghost vessels at any level of the cornea.
Clinical signs of endotheliitis include keratic precipitates (KP), overlying stromal and epithelial edema, and absence of stromal infiltrate or neovascularization. A mild to moderate iritis is frequently seen. Patients present with pain, photophobia, and injection.
See Clinical Presentation for more detail.
HSV keratitis remains primarily a clinical diagnosis based on characteristic features of the corneal lesion.If the diagnosis is in doubt, however, laboratory diagnosis can be made using the following:
Giemsa stain – Scrapings of the corneal or skin lesions show multinucleated giant cells
Papanicolaou stain – This shows intranuclear eosinophilic inclusion bodies
Immunohistochemistry looking for viral antigens
Polymerase chain reaction (PCR) assay