Herpes simplex keratitis is infection of the cornea caused by herpes simplex virus.
The herpes simplex virus (which causes cold sores—see Viral Infections: Herpes Simplex Virus Infections) never leaves the body after an initial (primary) infection. Instead, the virus remains in a dormant stage in the nerves. Sometimes, the virus reactivates and causes further symptoms.
Primary herpes simplex eye infections usually occur in children and cause a mild keratoconjunctivitis. Symptoms usually resemble those of common conjunctivitis, so the diagnosis of herpes simplex infection is not made. The infection resolves without treatment. However, if the infection reactivates, it can affect the cornea (the clear layer in front of the iris and pupil) more seriously and cause more severe symptoms.
Symptoms of a reactivation include eye pain, tearing, redness, a feeling like a foreign object is in the eye (foreign body sensation), and sensitivity to bright light. Rarely, the infection worsens and the cornea swells, making vision hazy. The more often the infection recurs, the more likely is further damage to the surface of the cornea. Several recurrences may result in the formation of deep ulcers, permanent scarring, and numbness of the eye surface. The herpes simplex virus can also cause blood vessels to grow onto the cornea and, occasionally, can lead to significant visual impairment. To diagnose a herpes simplex infection, a doctor examines the eye with a slit lamp (see What Is a Slit Lamp?). Sometimes, the doctor may swab the infected area to identify the virus (viral culture).
The doctor may prescribe an antiviral eye drop, such as trifluridine or ganciclovir. Acyclovir, another antiviral drug, can be taken by mouth or by vein (intravenously). The antiviral drug valacyclovir can also be taken by mouth. Treatment should be started as soon as possible. Deep infections that cause a lot of inflammation may require use of corticosteroid drops and drops that dilate the eye, such as atropine or scopolamine. Occasionally, to help speed healing, after numbing the eye, an ophthalmologist (a medical doctor who specializes in the evaluation and treatment—surgical and nonsurgical—of eye disorders) may have to gently swab the cornea with a soft cotton-tipped applicator to remove infected and damaged cells.
Last full review/revision November 2012 by Melvin I. Roat, MD, FACS