SCIENCE / MEDICINE : Eye Herpes: Virus-Borne Disease Can Peril Vision
There have been times in the last 21 years when the pain in Kathy Carroll’s left eye has been so excruciating--as though something literally was eating away at her eyeball--that she would trip herself or walk into a wall to divert her attention.
There have been other times when she would tell an acquaintance about the cause of her recurring pain and get “very strange looks” in return.
Kathy Carroll has ocular herpes, a little-known disease that strikes an estimated 300,000 to 500,000 people each year in the United States. In this country, it is the primary infectious cause of corneal blindness.
Widespread Problem
The problem is also found worldwide. Chinese researchers, for example, have told American specialists that it is the No. 1 ophthalmologic problem in China.
In most cases, including Carroll’s, ocular herpes is caused by the herpes simplex I virus, the same virus that for most people raises only a blister on the lip. In a small percentage of cases, usually in infants whose mothers had genital herpes, the herpes simplex II virus is responsible for ocular herpes.
For reasons scientists don’t understand, in about 90% of adults the simplex I virus lies latent in the trigeminal ganglion, a nerve that has branches leading to the mouth, jaw and eye. When the virus activates, it travels down one of these branches.
“Most of us have that virus traveling down either the maxillary or mandibular branch, thus you have a lesion on your lip,” said Melvin Trousdale, a virologist at the Estelle Doheny Eye Foundation at USC. “The unfortunate people where the virus travels down that highway to the eye (are) going to have a lesion on the cornea.”
Branch-Shaped Lesion
When fully developed, that lesion is shaped like a tiny tree branch flattened against the eye. Researchers don’t know how to cure the disease. They don’t know how to predict the onset of an ocular herpes bout and they don’t know why some people have recurrences and others don’t.
But in the last two years, scientists at several institutions, including UCLA and Cedars-Sinai Medical Center, have been developing a genetic map of the virus. It now appears that two genes in the virus may control its recurrence.
“It’s the first real breakthrough in about 15 years,” Anthony Nesburn said of the genetic discovery. Nesburn is a member of one of the teams mapping the virus and director of the Ophthalmology Research Laboratories at Cedars Sinai.
How It Works
Now researchers are trying to better define how the two genes control latency. If they can do that, they may be able to figure a way to destroy the virus, or at least keep it in a latent state.
Most people who get ocular herpes feel it first as some small irritation, like a grain of sand or an eyelash trapped under an eyelid. The eye will look red and watery and be sensitive to light. As it progresses and the lesion grows, the irritation can turn into an intensely painful, scratchy feeling and in severe cases the eye may discharge pus.
“You do not look very pretty,” said Carroll, a human resource manager for a health care company. “You withdraw because you just don’t function as well. It saps you of your confidence.”
Researchers estimate that 29% of first-time ocular herpes simplex I victims will suffer another bout with the virus. Of those people, about half will suffer three or more attacks.
Started at 18
Carroll’s first ocular herpes attack occured when she was 18. Carroll, a Los Angeles resident, had been wearing contact lenses for a year and thought her left lens was the problem until her doctor diagnosed the herpes.
“It was very traumatic,” she said of that first bout, which lasted for several months. Within two years, she had lost most of the vision in her left eye from repeated herpes attacks and had to have a corneal transplant. She estimated that she has had at least 100 attacks since, each one marked by piercing pain. Usually, with antibiotics, the lesion clears up in about two weeks.
Figures on just how many Americans lose vision each year from herpes are hard to ascertain, since the illness is not routinely reported to health department statisticians. However, Nesburn estimates that there are 2,000 to 3,000 patients each year who suffer enough corneal scarring from the disease to require a cornea transplant.
Some Drugs Help
The first drug ever produced to treat a virus was designed in 1962 to treat ocular herpes. Since then, more effective drugs have been developed to speed the time it takes to clear the herpes lesion and minimize tissue damage that could lead to vision loss.
But none of the drugs available cure the virus or guarantee it won’t recur.
Also, although the virus is fairly prevalent, misdiagnosis is not uncommon.
In its early stages, the herpes lesion can look like a spot rather than a branch. Doctors unfamiliar with ocular herpes, Nesburn said, have been known to rely on the symptoms of redness and pain to misdiagnose--and mistreat--the problem as some other, more benign, infection.
