What Is Herpetic Eye Disease

Overview

Herpetic eye disease is a painful viral eye infection caused by herpes viruses that can lead to vision loss and blindness if left untreated. The most common type of eye herpes is herpes simplex keratitis which affects the cornea. In the developed world, it is the main cause of blindness and it accounts for 1 in 10 corneal transplants in the UK.
Symptoms include red, painful, swollen eyes and a rash or blisters can develop around the eye or on the eyelid. Herpes simplex infections cannot usually be cured but with the right treatment, they can be controlled.

Ocular herpes is mainly caused by the herpes simplex virus type 1 (HSV-1), responsible for cold sores, and not usually the herpes simplex virus type 2 (HSV-2), the cause of genital herpes. Herpes simplex infections cannot usually be cured but with the right treatment, however, they can be controlled.

A similar eye infection, herpes zoster ophthalmicus (HZO) is caused by the herpes zoster virus which causes chickenpox or shingles. 

Usually, the first exposure to herpes viruses occurs in children. The viruses then remain dormant in adults, however, they may be reactivated due to different triggers such as illness or stress. This can then lead to an outbreak of ocular herpes. 

What is the cornea

The cornea is the clear region in the front center of the eye's outer wall, exactly where you wear your contact lenses. It is made of collagen fibers arranged in such a way that the cornea is clear, allowing light to enter the eye and bend onto the retina. The iris and pupil can be seen through the cornea.⁴

Our vision is strongly reliant on corneal transparency and refractive power. The cornea provides defense against damage and infections and accounts for two-thirds of the overall refractive power of the eye. It is made up of three layers: epithelium, stroma, and endothelium, which are separated by two extracellular matrix interfaces: the Bowman's layer and the Descemet membrane.³

Types of eye herpes

There are two main types of ocular herpes that affect the cornea: epithelial keratitis and stromal keratitis. Keratitis caused by an infection with the herpes simplex virus is known as herpes simplex virus keratitis (HSV keratitis). Herpes zoster keratitis is caused by an infection with the herpes zoster virus:

• Epithelial keratitis makes up between 50-80% of ocular herpes cases and usually only affects the outer layer of the cornea (epithelium)

Sometimes the deeper layers of the cornea (stroma) are affected and this is known as stromal keratitis. 

• Stromal keratitis can lead to increased intraocular pressure, scarring and even blindness. The stromal keratitis may be necrotising which can lead to a corneal ulcer

After a mild trauma, the epithelium can easily recover and regain normal vision. In the case of deeper wounds, however, the stroma develops permanent opaque scars, the amount of which is proportional to the severity of the lesion.³

Eye herpes can also affect other parts of the eye such as the retina, iris, conjunctiva, eyelids and surrounding skin, but this is rarer.

Causes of eye herpes

Herpes simplex eye infection is mainly caused by an infection with HSV-1, the virus that usually causes cold sores. Although HSV-1 can be transmitted directly to the eye by contact with an infected area such as a cold sore, most ocular herpes infections are secondary. 

Most people are exposed to herpes simplex as children and first-time infections are usually mild or asymptomatic. If symptomatic they usually only cause blepharoconjunctivitis.

After this, the herpes simplex virus remains dormant in the body, usually in the trigeminal nerve ganglion. When the virus reactivates it can then lead to ocular herpes.

This reactivation can be triggered by illness, stress, too much or prolonged exposure to sunlight or eye injury. People who are immunocompromised or taking immunosuppressive drugs are also more at risk. 

Similarly, most adults are exposed to the herpes zoster virus, which usually causes chickenpox  or shingles, as children.

Just like with HSV, the virus causes a primary infection, usually as a child and then lies dormant in the dorsal root and cranial nerve sensory ganglia until reactivation.

Herpes zoster affects 20-30% of the population at some point during their lifetime, and it is due to a localised reactivation in the ophthalmic division of the trigeminal nerve that leads to herpes zoster ophthalmicus (HZO). This usually occurs in older age, or people who are immunocompromised or taking immunosuppressive drugs.

Signs and symptoms of eye herpes

Symptoms usually only affect one eye and can include the following:

• Pain in and around the eye
• A red eye
• Watery discharge from the eye
• Sensitivity to light
• Blurred vision and a feeling of having “grit” in the eye tends to occur more with hsv keratitis

Symptoms of herpes zoster keratitis usually also include a red, vesicular rash on the eyelids, forehead and tip of the nose and pain on one side of the forehead. Flu-like symptoms may also be present.

Symptoms of herpes keratitis can sometimes be confused with conjunctivitis (also known as pink eye). Conjunctivitis can be caused by bacteria, viruses or allergies and usually affects both eyes, whereas herpes eye usually only affects one eye. 

Management and treatment for eye herpes

Herpes keratitis infections are treated with antiviral medicine taken as eye drops, tablets or both.

Corticosteroid eye drops may also be given to reduce the swelling if the cornea is affected. If these are given the patient has to be monitored, as it may raise the eye pressure in some patients. When treated correctly most patients recover within a couple of weeks and their vision is not permanently affected.

Patients who wear contact lenses should not use them until 24 hours after symptoms have disappeared. A new set of contact lenses should be used after the infection.

Some people who get recurrent ocular herpes may need to take antiviral tablets daily to prevent this.

In some countries, the varicella vaccine is given to children to prevent chicken pox. This may help to prevent herpes zoster in older age.

Patients who suffer corneal scarring due to recurrent or severe infections may need a cornea transplant as their vision may become impaired.

Diagnosis

Eye herpes is usually diagnosed through a thorough eye exam by an eye specialist based on the patient's presentation, symptoms and medical history. The ophthalmologist will look for the presence of dendritic lesions on the cornea during fluorescein staining of the eye by usign a slit lamp biomicroscope. This examination will show any abrasions or damage to the cornea.² 

If eye herpes is suspected, an eye culture to test for the presence of the herpes virus should be done. 

Reduced corneal sensation should also indicate herpes keratitis. 

If the patient had a previous ocular herpes infection, herpes simplex infection or an unresolved case of blepharoconjunctivitis, herpes simplex keratitis should be suspected.

FAQs

How can I prevent eye herpes

Eye herpes is usually caused by the herpes family of viruses. To reduce the risk of infection, avoid touching your eyes, wash your hands regularly and avoid touching your lips if you are suffering from an outbreak of cold sores. It is also important not to share eye drops or eye makeup with anyone else. The vaccine against varicella may also be helpful to prevent herpes zoster in later life. For those suffering from recurrent herpes keratitis, it is a good idea to try to boost immunity and some patients may need to take daily antiviral medication to prevent an outbreak.

How common is eye herpes

Herpes eye infections are quite common. They usually affect middle-aged people. About 1-2 people in 1000 will develop a herpes simplex eye infection at some point in their life.

Who is at risk of eye herpes

People with a weakened immune system are most at risk of eye herpes. This is because the herpes viruses usually remain dormant until something triggers them. Triggers include illness, too much sun, stress or an eye injury.

When should I see a doctor

If you have pain in your eye, the redness in your eye is getting worse or does not improve after several days, or the swelling and irritation isn’t getting any better you should contact your healthcare provider and make an urgent appointment. You should also make an urgent appointment if you experience any blurry vision or changes to your sight. 

Summary

Ocular herpes is caused by the herpes viruses. It usually leads to herpes keratitis, an infection of the cornea. More severe infections which damage the cornea can lead to vision loss and blindness. It is one of the leading causes of blindness in the developed world.

Most infections are caused by the herpes simplex virus, which is also responsible for cold sores. Some cases of ocular herpes are also caused by the herpes zoster virus, the virus that usually causes chickenpox or shingles. The primary infection with these herpes viruses occurs in early childhood and is asymptomatic, the viruses then remain dormant in the body until later reactivation is triggered, often during periods of weakened immunity. This can then lead to an outbreak of ocular herpes. Symptoms can include red, painful eyes and blurred vision. A person suffering from these symptoms should contact an eye specialist for urgent assessment and quick treatment to avoid any corneal scarring. Although ocular herpes can not be cured the flare-ups can be treated with the help of antiviral medication and steroid eye drops. Early and accurate diagnosis, is necessary to prevent any complications.