Herpes simplex keratitis is corneal infection with herpes simplex virus. It may involve the iris. Symptoms and signs include foreign body sensation, lacrimation, photophobia, and conjunctival hyperemia. Recurrences are common and may lead to corneal hypoesthesia, ulceration, permanent scarring, opacification, thinning of the corneal stroma, and decreased vision. Diagnosis is based on the characteristic dendritic corneal ulcer and sometimes viral culture. Treatment is with topical or systemic antiviral drugs.
Herpes simplex keratitis usually affects the corneal surface but sometimes involves the corneal stroma (the deeper layers of the cornea) or the inner corneal surface (endothelium), anterior chamber, and iris. Stromal involvement is probably an immunologic response to the virus.
As with all herpes simplex virus infections, there is a primary infection, followed by a latent phase, in which the virus enters the nerve roots. Latent virus may reactivate, causing recurrent symptoms.
Herpes simplex keratitis is a major cause of blindness worldwide.
Symptoms and Signs of Herpes Simplex Keratitis
Primary infection
The initial (primary) infection is usually nonspecific self-limiting conjunctivitis, often in early childhood and usually without corneal involvement. If the cornea is involved, symptoms include foreign body sensation, lacrimation, photophobia, and conjunctival hyperemia. Sometimes vesicular blepharitis (blisters on the eyelid) follows, symptoms worsen, vision blurs, and blisters break down and ulcerate, then resolve without scarring in about a week.
Recurrent infection
Recurrent ocular herpes affects the cornea. Three main types of herpes simplex keratitis are
Epithelial keratitis (dendritic keratitis)
Disciform keratitis (localized endotheliitis)
Stromal keratitis
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Most patients with disciform keratitis, which involves the corneal endothelium primarily, have a history of epithelial keratitis. Disciform keratitis is a deeper, disc-shaped, localized area of secondary corneal stromal edema and haze accompanied by anterior uveitis. This form may cause ache, photophobia, and reversible vision loss.
Stromal keratitis is likely to cause necrosis of the stroma and severe ache, photophobia, foreign body sensation, ulceration, permanent scarring, opacification, neovascularization, thinning of the corneal stroma, and irreversible decreased vision.
Diagnosis of Herpes Simplex Keratitis
Slit-lamp examination
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Slit-lamp examination is mandatory. Finding a dendrite is enough to confirm the diagnosis in most cases. When the appearance is not conclusive, viral culture or nucleic acid amplification tests (NAAT) swab of the lesion can confirm the diagnosis.
Treatment of Herpes Simplex Keratitis
For stromal involvement or uveitis, topical corticosteroids in addition to antiviral drugs
Most patients are managed by an ophthalmologist. If stromal or uveal involvement occurs, treatment is more involved and referral to an ophthalmologist is mandatory.
Topical corticosteroids are contraindicated in epithelial keratitis, but they may be effective when used with an antiviral to manage later-stage stromal involvement (disciform or stromal keratitis) or uveitis
Key Points
Herpes simplex keratitis typically is a recurrence of primary herpes simplex eye infection that was usually a nonspecific, self-limiting conjunctivitis.
Characteristic findings include a branching dendritic or serpentine corneal lesion (indicating dendritic keratitis), disc-shaped, localized corneal edema and haze plus anterior uveitis (indicating disciform keratitis), or stromal scarring (indicating stromal keratitis).
Diagnosis is confirmed by finding a dendritic ulcer, by viral culture, or by NAAT swab.
