Herpes Simplex Eye Infection

An episode of herpes simplex infection of the eye often clears without any permanent problem. However, in some cases the infection causes scarring to the cornea. This can lead to permanent loss of vision. Prompt treatment with antiviral eye ointment or drops helps to prevent corneal scarring.

 

Herpes simplex infections

There are two types of herpes simplex virus. Type 1 virus is the usual cause of cold sores around the mouth, and herpes simplex infection in the eye. Type 2 virus is the usual cause of genital herpes. It rarely causes cold sores or eye infections.

 

Type 1 herpes simplex 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.

Following the primary infection, the virus stays with you for life. It stays inactive (dormant) in the root of a nerve in the face (the trigeminal nerve).

• 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'.)
    
  • In some of these cases, the virus travels down a branch of the nerve to the eye to cause episodes of active eye infection. The rest of this leaflet is about herpes simplex infection of the eye.
    
  
  

Which part of the eye is affected with herpes simplex infection?

The common situation is for the cornea to become infected. The cornea is the transparent 'window' of the eye. Infection of the cornea is called keratitis.

 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.

Other parts of the eye are sometimes affected. A minor and temporary inflammation of the conjunctiva (conjunctivitis) or eyelids (blepharitis) may occur with active infection, often at the same time as the cornea is infected. Deeper structures such as the retina or iris are sometimes affected.

Who gets herpes simplex infections of the eye?

About 1-2 people in 1000 will develop at least one episode of active herpes simplex eye infection at some stage in their life. The most common age for a first episode is aged 30-40.

What are the symptoms and signs of active infection?

Most episodes of active infection are due to a re-activation of the virus at some point, often years after a primary infection. Symptoms include:

• Redness of the eye - mainly around the cornea.
  
• Ache or pain in the eye.
  
• Photophobia (discomfort when opening the eyes in bright light).
  
• Watering of the eye.
  
• Blurring of vision.

A doctor will usually examine the eye with a magnifier. They may also put some stain on the front of the eye to show up any irregular areas on 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 'many fingered'. 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 be referred urgently to an eye specialist. A specialist will do a detailed magnified examination of the eye. This is to confirm the diagnosis and to determine if the infection is in the top layer of the cornea (epithelial keratitis) or if the deeper layers are involved (stromal keratitis).

What is the treatment for herpes simplex eye infection?

 

If the top (superficial) layer is affected - epithelial keratitis

Treatment is with antiviral eye ointment or drops (such as aciclovir ointment or ganciclovir drops). 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 cornea. In some cases, a specialist may also gently scrape the affected part of the cornea to remove affected cells.

 

If the deeper layer of the cornea is affected - stromal keratitis

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 who will prescribe the correct strength and dose in conjunction with antiviral treatment. Used wrongly on their own, steroid drops cause more harm than good.

Antiviral tablets are used in some cases.

 

If just the eyelids or conjunctiva are affected

No treatment may be advised. These infections will usually settle on their own in 1-3 weeks. You are likely to be kept under review until the infection goes to check that the cornea does not become infected.

 

Preventing recurring infections

Some people develop recurring episodes of active infection. As mentioned above, these occur if the virus 'reactivates' from time to time - similar to cold sores. At least half of people who have one episode of active infection will have a recurrence within 10 years of the first. In about 1 in 10 cases, the recurrence is within a year. Recurrences occur more often in some people than others.

If the recurrences are frequent (say, once a year or more) or severe, then your eye specialist 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. Wearing sunglasses may also help to prevent recurrences.

If a recurrence does occur, each episode is treated as described above.

 

What is the outlook (prognosis)?

The main concern with corneal infection (keratitis) is that it can cause scarring. With scarring the normally clear and transparent cornea become like 'frosted glass'. This can seriously affect vision.

• Epithelial keratitis tends to settle and go away in 1-2 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, about 9 in 10 'involved eyes' maintain good vision (good enough to drive). However, severe and recurrent herpes simplex eye infections may lead to serious scarring, impaired vision and even blindness. If blindness develops, a corneal transplant is then the only option to restore vision.

References

• Clinical Knowledge Summaries; Herpes simplex - ocular (March 2008).
  
• Wang JC, Ritterband DC; eMedicine: Keratitis, Herpes Simplex (December 2007).
  
• Wilhelmus KR; Therapeutic interventions for herpes simplex virus epithelial keratitis. Cochrane Database Syst Rev. 2008 Jan 23;(1):CD002898. [abstract]
  

© EMIS and PiP 2008    Updated: 15 May 2008

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