Herpes simplex eye infection is caused by a type of herpes simplex virus. An episode often clears without any permanent problem. However, in some cases the infection causes scarring to the transparent front part of the eye (the cornea). This can lead to permanent loss of vision. Prompt treatment with antiviral eye ointment or drops helps to prevent corneal scarring. There are two types of herpes simplex virus. Type 1 is the usual cause of cold sores around the mouth, and herpes simplex infection in the eye.
Type 2 is the usual cause of genital herpes. It rarely causes cold sores or eye infections. The first time you are infected is called the primary infection. Many people become infected with this virus, often during childhood. The herpes simplex virus can pass through the moist skin that lines the mouth. It is commonly passed on by close contact such as kisses from a family member who has a cold sore. In many people the primary infection does not cause any symptoms, although in some cases symptoms do occur.
In many people, the virus remains permanently inactive and causes no problems. In some people, the virus activates and multiplies from time to time. Virus particles then travel down the nerve to cause episodes of active infection with symptoms: In most of these cases, the virus travels down a branch of the nerve to the mouth to cause cold sores. (See separate leaflet called Cold Sores for details.) In some of these cases, the virus travels down a branch of the nerve to the eye to cause episodes of active eye infection. In most cases, the infection is just in the top (superficial) layer of the cornea. This is called epithelial keratitis. Sometimes deeper layers of the cornea are involved.
This is called stromal keratitis. This is more serious, as it is more likely to cause scarring of the cornea. The thin lining of the eyelid (the conjunctiva), called conjunctivitis. The eyelids, called blepharitis. Sometimes, deeper structures, such as the retina or the iris. The retina is a layer of the eyeball, found on its back wall. The iris is the coloured part of the eye.
Who gets herpes simplex infections of the eye? About 1-2 people in 1,000 will develop at least one episode of active herpes simplex eye infection at some stage in their life. The most common time for a first active infection is between the ages of 30 and 40. Often people who get active eye infection will have had previous cold sores during their lifetime. Herpes simplex eye infections may also be more common in people who wear contact lenses. Redness of the eye – mainly around the transparent front part of the eye (the cornea). Ache or pain in the eye.
Discomfort when opening the eyes in bright light (photophobia). Watering of the eye. Blurring of vision. A doctor will usually examine your eye with a magnifier. They may also put some stain on the front of your eye. This is used to show up any irregular areas on the transparent front part of the eye (the cornea). With a herpes simplex infection they will often see a small ulcer (erosion) on the cornea.
The typical ulcer which develops is called a dendritic ulcer. Dendritic means branching. The ulcer is not round with a smooth edge but like a tree with many finger-like branches. If your doctor suspects a herpes eye infection you will usually be referred urgently to an eye specialist (ophthalmologist). A specialist will do a detailed magnified examination of the eye. This is to confirm the diagnosis and to determine whether the infection is in the top layer of the cornea (epithelial keratitis), or if the deeper layers are involved (stromal keratitis). Before you start to use any eye drops or ointment, your eye specialist (ophthalmologist) may gently scrape away some of the infected cells from the surface of your eye.
They will numb your eye with anaesthetic drops before the procedure. This procedure is called debridement. Treatment is with antiviral eye ointment or drops (such as aciclovir ointment or ganciclovir gel). These do not kill the virus but stop it from multiplying further until the infection clears. You should take the full course exactly as prescribed. This is often several times a day for up to two weeks. The aim is to prevent damage to the transparent front part of the eye (the cornea).
Treatment is similar to epithelial keratitis (above). In addition to the antiviral eye ointment or drops, your specialist may add in some steroid eye drops. This helps to reduce inflammation. Note: steroid eye drops must only be used under close supervision of an eye specialist. He or she will prescribe the correct strength and dose in conjunction with antiviral treatment. Used wrongly on their own, steroid drops cause more harm than good. These infections will usually settle on their own in 1-3 weeks.
No treatment may be advised. You are likely to be kept under review, until the infection clears, to check that the cornea does not become infected. Some people develop repeated (recurring) episodes of active infection. As mentioned above, these occur if the virus reactivates from time to time – similar to cold sores. A recurrent infection may occur any time between a few weeks and many years after the first active infection. At least half of people who have one episode of active infection will have a recurrence within 10 years of the first. Recurrences occur more often in some people than others.
If recurrences are frequent or severe, your eye specialist (ophthalmologist) may advise that you take antiviral tablets each day to prevent episodes of active infection. Studies have shown that, on average, the number of recurrences is roughly halved in people who take regular antiviral tablets. Some people say that episodes of active herpes infection may be triggered by strong sunlight. So, wearing sunglasses may also help to prevent recurrences. It is also possible that active infection may be triggered if you are run down or unwell for another reason. However, the evidence for this is limited. Some women find that they get recurrences around the time of their period but again there is limited evidence to support this.
The main concern with corneal infection (keratitis) is that it can cause scarring of the transparent front part of the eye (the cornea). With scarring, the normally clear cornea can become like frosted glass. This may sometimes seriously affect vision. Epithelial keratitis tends to settle and go away within a few weeks. It has a good outlook and often causes little or no scarring. Stromal keratitis is more likely to result in corneal scarring and loss of vision. Recurring episodes of active infection can make any existing scarring worse.
Prompt treatment with antiviral eye ointment or drops helps to minimise damage during each episode of active infection. Overall, good vision remains in about 9 in 10 eyes affected by herpes simplex infection – that is, vision good enough to drive. However, severe and recurrent herpes simplex eye infections may lead to serious scarring, impaired vision and even severe sight impairment in some cases. If severe sight impairment does develop, a corneal transplant may be the only option to restore vision.