Common Anti-Viral Medication Prevents Severe Eye Herpes

The study, published in the July 30 edition of the New England Journal of Medicine, shows that acyclovir is particularly effective in preventing recurrences of a serious strain of the eye disease, called stromal keratitis, which can lead to scarring of the cornea with vision loss and blindness.

The study found that the rate of recurrence of this blinding form of the disease dropped 50 percent when patients took 400 milligrams of acyclovir by mouth twice a day, said Chandler R. Dawson, MD, UCSF professor emeritus of ophthalmology and former director of UCSF's Francis I. Proctor Foundation for Research in Ophthalmology, who led the study.

The findings, Dawson said, are the key to preventing recurrences of a particularly harmful form of the disease that affects thousands of Americans each year. About 400,000 Americans have had some form of ocular herpes and some have recurrent eye infections. About 25 percent of the 50,000 Americans who experience some form of eye herpes each year have stromal keratitis.

The study's key finding, Dawson said, is that it identifies those patients with potentially blinding herpetic stromal keratitis who will benefit most from long-term acyclovir treatment. Most opthalmologists can diagnose this blinding disease by a simple clinical examination and treat these high risk patients with long-term preventive dose of acyclovir, Dawson said.

The results of the study are particularly promising because this dose of acyclovir has very few side effects, meaning patients can safely use the drug for prevention, Dawson said.

"This is the first time the drug has been used for prevention of the eye disease," Dawson said. "Acyclovir clearly and significantly reduces the number of recurrences."

The drug also sharply reduced the recurrence of less serious forms of the herpes eye disease, the study found. Acyclovir reduced by 41 percent the chance that any form of the eye herpes virus would recur in patients who had the infection during the previous year.

In both stromal keratitis and less severe forms of the eye disease, the causative herpes simplex virus persists between disease episodes in the nerve cells involved in pain and touch to the lids and eyes. The virus may be dormant most of the time, but there is a high risk of recurrence once patients have had any eye involvement.

Less severe types of eye herpes are not as damaging as stromal keratitis, though they also recur frequently, Dawson said. The herpes virus also causes blisters on the eyelids, conjunctivitis or superficial ulcers of the cornea. These forms of the disease usually heal with locally applied anti-virals and without complications. Herpes of the eye is usually caused by herpes simplex I virus, which also causes fever blisters or cold sores around the face and mouth.

The study, which was funded by the National Eye Institute of the National Institutes of Health, tracked 703 patients in medical centers around the country who had eye herpes infections during the previous year. About half those patients used acyclovir for one year. The other half took placebo capsules. During that time, about 19 percent of the patients who took acyclovir experienced a herpes flare up. The infection flared up in about 35 percent of the placebo group.