Herpes simplex is a virus that infects the skin, mucous membranes and nerves. There are two major types of herpes simplex virus (HSV). Type I is the most common and is responsible for herpes simplex eye disease and the familiar “cold sore” or “fever blister.” Type II is responsible for sexually transmitted herpes and rarely causes infection above the waist.
An original infection with herpes simplex type I (HSV type I) occurs in 90 percent of the population, usually during childhood or adolescence. The infection, sometimes only a mild sore mouth or sore throat, comes from close personal contact with an infected person and usually passes without notice.
After the original infection, the virus goes into a quiet or dormant period, living in nerve cells that supply the skin or eye. Occasionally, the virus reactivates and causes a recurrent “cold sore” or “fever blister.”
What is Herpes Simplex Eye Disease?
The most common herpes simplex eye disease caused by HSV type I is a current eye infection of the cornea — which can potentially threaten sight. The infection varies in duration, severity and response to treatment, depending in part on which of several different strains of HSV type I caused the original infection. It can be considered a “cold sore” or “fever blister” of the eye.
The disease usually begins on the surface of the cornea. The eye turns red, is uncomfortable and sensitive to light. For most people this will be the only episode. Unfortunately, one out four people who have a corneal infection are likely to have a recurrence within two years.
The process may go deeper into the cornea and cause permanent scarring or inflammation inside the eye. Chronic ulcers, which are sometimes very difficult to heal, may also develop on the cornea.
Herpes simplex eye disease usually occurs in only one eye and rarely spreads to the other eye. Spreading the infection to another person is unlikely. In people with poor immunity, the herpes simplex virus may infect other parts of the eye or body, such as the retina or brain, but this occurs infrequently.
It is important to remember that herpes simplex eye disease is not usually caused by HSV type II, the sexually transmitted herpes. While possible, sexual transmission of herpes eye disease is extremely rare.
Treatment depends on the extent of the disease. Antiviral eye medications are commonly used and may need to be applied as frequently as one drop per hour. At times it may be necessary to scrape the surface of the cornea, to patch the eye, or to use a variety of medications. In cases of severe scarring and vision loss, a corneal transplant may be required.
It is very important to consult an eye doctor before beginning any treatment since some medications may actually make the disease worse.