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 Herpes Simplex Virus (HSV) Infections Herpes simplex viruses (human herpesviruses types 1 and 2) commonly cause recurrent infection affecting the skin, mouth, lips, eyes, and genitals. Common severe infections include encephalitis... read more , 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
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 ocular herpes affects the cornea. Three main types of herpes simplex keratitis are
Epithelial keratitis (dendritic keratitis)
Disciform keratitis (localized endotheliitis)
Reactivation of latent herpes simplex can be triggered by UV light exposure (eg, intense sunlight, corneal cross-linking [an ultraviolet light treatment that stiffens the cornea], or laser refractive procedures), fever, menstruation, significant systemic physical stress (eg, burns or multiple fractures), immunosuppression, or use of glucocorticoids (topical ophthalmic, periocular injection, intraocular injection, or systemic). Recurrences usually take the form of epithelial keratitis (also called dendritic keratitis), with tearing, foreign body sensation, and a characteristic branching (dendritic or serpentine) lesion of the corneal epithelium with bulb-like terminals that stain with fluorescein. Multiple recurrences may result in corneal hypoesthesia or anesthesia, ulceration, permanent scarring, opacification, thinning of the corneal stroma, and decreased vision.
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 Slit-lamp examination The eye can be examined with routine equipment, including a standard ophthalmoscope; thorough examination requires special equipment and evaluation by an ophthalmologist. History includes location... read more 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) Nucleic Acid–Based Identification Methods for Infectious Disease Nucleic acid–based methods detect organism-specific DNA or RNA sequences extracted from the microorganism. Sequences may or may not be amplified in vitro. Nucleic acid–based (molecular) identification... read more swab of the lesion can confirm the diagnosis.
Treatment of Herpes Simplex Keratitis
Topical ganciclovir or trifluridine
Oral or IV acyclovir or valacyclovir
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.
Dendritic (epithelial) keratitis can be treated with topical therapy (eg, ganciclovir 0.15% gel applied every 3 hours while awake [5 times/day] or trifluridine 1% drops every 2 hours while awake [9 times/day]). Topical therapy is usually effective and is tapered off over 2 to 3 weeks.
Alternatively, oral therapy (eg, acyclovir 400 mg orally 3 to 5 times/day or valacyclovir 1000 mg orally twice/day) is also effective. Acyclovir 400 mg orally twice/day or valacyclovir 500 to 1000 mg orally once/day may be prescribed as suppressive therapy to prevent frequent recurrences as well as to preserve eyesight in patients whose vision has been threatened.
Immunocompromised patients may require IV antivirals (eg, acyclovir 5 mg/kg IV every 8 hours for 7 days).
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 Overview of Uveitis Uveitis is defined as inflammation of the uveal tract—the iris, ciliary body, and choroid. However, the retina and fluid within the anterior chamber and vitreous are often involved as well.... read more . In such cases, patients may be given prednisolone acetate 1% instilled every 2 hours initially, lengthening the interval to every 4 to 8 hours as symptoms improve.
If the epithelium surrounding the dendrite is loose and edematous, debridement by gentle swabbing with a cotton-tipped applicator before beginning drug therapy may speed healing. Topical drugs to relieve photophobia include atropine 1% or scopolamine 0.25% 3 times a day.
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.
Treatment requires antivirals, usually topical ganciclovir or trifluridine or oral acyclovir or valacyclovir.