Ocular Herpes Simplex
Herpes simplex virus is a common virus affecting humans. It is perhaps best known as the cause of cold sores, the facial blisters that sometimes occur following a cold or fever. The name herpes comes from the Greek word meaning "to creep", as cold sores sometimes appear to creep or spread over the face. There are two types of herpes simplex viruses. Type I primarily involves the face and eyes, and type 2 primarily causes genital infections. Each year in the United States approximately 25 million people have flare-ups of facial herpes, five million develop genital herpes. There are about 500,000 people in the U.S with a history of herpetic eye disease.
Eye involvement and symptoms
When the eye is afflicted by herpes simplex, it usually affects only one eye and most often occurs on the cornea (the normally clear dome that covers the front part of the eye). This type of corneal infection is called Herpes Keratitis. The infection may be superficial, involving the top layer (epithelium) of the cornea, and usually heals without scarring, or it may involve the deeper layers of the cornea. If the infection involves the deeper layers, it may lead to scars of the cornea, loss of vision, and sometimes even blindness. Less commonly, herpes simplex virus may also infect the inside of the eye (Herpes Uveitis) or the retina (Herpes Retinitis).
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Symptoms of herpetic eye disease may include blurred vision, sensitivity to light, and pain and redness of the eye.
Who gets herpes in the eye? A majority of people have been exposed to herpes simplex virus without being aware of it, usually sometime in early childhood. In most people, the virus settles in the nerves going to the face. Usually the virus remains dormant from then on and does not cause any clinical disease. In some people, however, the virus can be reactivated and spread down the nerves to the face or to an eye. The reasons for this reactivation and reinfection are not completely understood. The factor that determines eye involvement and only skin or lip involvement is unknown. Probably the strain or subtype of the virus as well as the patient’s immune system play a role in whether the disease recurs. The factors that trigger a recurrence of herpes simplex infection are unknown. After the first episode of corneal infection, approximately one in four patients will have a recurrence in the next two years. After the second eye infection, the odds of further recurrences greatly increase. Recurrences cannot yet be predicted or prevented.
The treatment of herpes infection of the eye depends on the location and the severity of involvement. Patients whose corneal infection is only superficial need to apply eyedrops or ophthalmic ointments that are antiviral – they attack viruses. Some ophthalmologists may also treat these patients by wiping away infected cells from the cornea with a dry, cotton-tipped applicator. Treatment may vary for deeper, more severe corneal infection and for herpetic inflammation within the eye. The antiviral eyedrops presently available are less effective in treating these severe infections. Steroids, in the form of drops, may help decrease inflammation and corneal scarring. Despite the available treatments, some patients do not respond well or rapidly to treatment. These patients may have prolonged inflammation and ultimately permanent corneal scarring and may need corneal transplantation to restore their vision. Thus, better therapies for herpes keratitis are required.
The UIC Eye Center is involved in research to help find the safest and most effective treatments for herpetic eye disease. We participated in a multicenter study called the Herpetic Eye Disease Study (HEDS), funded by the National Eye Institute. This study investigated the efficacy of certain treatments in reducing the severity of herpes simplex keratitis. This study showed that corticosteroids are beneficial in treatment of stromal keratitis. The efficacy of oral antivirals and the triggers of recurrences are still being studied.
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