What is eye herpes?
Eye herpes, or ocular herpes, is a recurrent viral infection that affects the eyes. It is caused by herpes simplex virus type 1. It causes an inflammation of the eye, as well as scarring in the cornea.
Eye herpes can be transmitted from one person to another when there is a close contact with the affected person. Once infected with HSV–1 the virus, enters the body through the mouth or nose, and travels into the nerve roots where it stays inactive for many years. The real cause of the outbreak is not known, but it is believed that conditions like fever, sunburn, or anything else that affects the immune system can trigger the eye herpes infection to reoccur.
Eye herpes forms
Different forms of eye herpes can occur ranging from a simple eye infection to a condition that could even cause a loss of vision.
Herpes keratitis is the most common type of the eye herpes. This type of herpes usually heals without scarring, as it only affects the epithelium (the top layer) of the cornea.
Stromal keratitis is a more serious viral infection characterized by an affection of the deeper layers of the cornea. It is a rare condition that is believed to result from a late immune response to the original infection. Stromal keratitis can lead to scarring of the eye, problems with vision, as well as loss of vision and blindness.
Iridocyclitis is the most serious form of eye herpes characterized by redness and painful eyes, severe sensitivity to light, and eye inflammation. The iris and the surrounding tissues are affected.
Herpes retinitis is a form of eye herpes affecting the retina.
Signs and symptoms of eye herpes
The signs and symptoms of eye herpes vary from one person to another.
Characteristic signs and symptoms of eye herpes include:
- Redness of the eyes
- Pain in the eyes
- Swelling around the eyes
- A sensation of a foreign body
- Watery eye discharge
- Sensitivity to light
- Recurrent eye infections
- Blurred vision
- Loss of vision.
How is ocular herpes transmitted?
In most of the cases direct transmission does not take place from one eye to another. By direct contact the virus is first acquired but no initial signs and symptoms are produced. The virus lies in latent and dormant state in the body’s nervous system. However it can reactivate months or years later and cause ocular herpes by traveling to the eye or it may cause cold sore by travelling to the lip. In children the herpes simplex virus causes a sign of an initial direct infection such as a small rash and pink eye. Mostly in childhood during epidemics of chicken pox the herpes zoster virus can be acquired through air. Before it can be reactivated and produce shingles in the eye it can sit dormant for decades.
Parts of the eye that can be affected by herpes virus
The herpes virus can affect all the parts of the eye. The components of eye are iris, cornea, pupil, lens, retina, optic nerve, vitreous, choroids and macula. Usually it is referred to as herpes ophthalmicus when any part of the eye is affected. The most affected part by HSV and HZV is cornea. Herpetic kertatitis is when the cornea is infected or inflamed. But even the skin of the eyelids can be affected. Even uveal tissue and retina can also be affected. To assess the extent of the eye involvement a thorough eye exam is recommended.
Majority of the population can carry the virus but not everyone carrying the virus may show eye infection. The virus can most likely become active and give rise to an eye infection when a person has weakened immune system such as those with HIV, age, medications and stress. However the frequency of eye infection appears to be random in many cases of HSV keratitis but this infection may not be accompanied by episodes of immune weakness or stress. From few days to several decades can be the range of incubation period of the virus.
Based on the symptoms and the signs alone most of the time the diagnosis can be made. Distinct erosion of the outer layer of the cornea referred to as dendrite is produced typically by herpes keratitis. The examiner can see the tree-branching pattern on the dendrite by using a blue light and an eye drop in which a dye is used. To distinguish between HSV and HZV keratitis the eye doctor can look for further clues under a slit lamp microscope but the initial antiviral treatment in either case is the same. The extent of the infection is assessed by close examination of the other eye tissues. To confirm the diagnosis a culture can be obtained in cases that are questionable.
How is eye herpes treated?
Treatment of the eye herpes depends from the severity of the infection and its location. In superficial corneal herpes infections, antiviral eye drops and oral antiviral medications are enough. Sometimes a debridement of the affected eye is necessary, during which an eye doctor will scrap away the infected corneal epithelial cells with the help of a corneal spatula.
With either topical or oral antiviral medication the treatment can be initiated. Intravenous medication is necessary in less common cases. The number of active viruses can be reduced using antiviral medications that suppress the reproduction of the virus. Thus the duration and severity of the infection can be reduced and possibly the chances of recurrence will also reduce. As of now there is no cure. Into the cells of the nervous system the herpes virus is incorporated where for months or years the virus remains inactive and quiet.
To eradicate the viruses in their latent state to date there is no treatment developed. For whatever reason when the virus becomes active it starts to reproduce and along a nerve to the site of the infection its progeny travels. These actively replicated viruses are today affected only by antiviral medications. Along with this the chances of a bacterial infection developing at the infection area can be reduced by antibiotic drops or ointment. This is because the cornea becomes vulnerable to secondary bacterial infection when the cornea is eroded.
As a result of internal swelling of the eye it can give rise to eye pressure. Also it may arise when the trabecular meshwork is directly affected. If this is the case then medications that can lower pressure can be prescribed. Herpes associated with significant inflammation can affect the middle layer of the cornea, iris and the back layer of the cornea.
Anti inflammatory medications such as steroids can be required if there is an inflammation of any tissues of the eye. In some cases the inflammation may recur or it can be chronic or several rounds of steroid treatment may be required.
Steroid drops are also recommended in order to reduce the inflammation, as well as to prevent corneal scarring. Antibiotic eye drops are sometimes prescribed to prevent a secondary bacterial infection of the affected eye.
In severe cases of herpes infection, surgery is needed to remove the scarred tissue in the cornea. When the scarring after eye herpes is permanent, corneal transplantation is the only solution.
Eye herpes does not have a cure, but treating it will only help prevent further damage to the eye and it can also help control the outbreak.
Complications and prognosis
If the herpes eye infection is not treated then in the worst cases it can cause blindness, loss of the eye and chronic pain. The treatment is aimed at reducing the eye pressure problems, chances of scarring and direct damage to the eye tissues.
Mostly the infection can be limited to the outer layer of cornea and with antiviral therapy it can resolve within couple of weeks with no permanent damage. Higher complication rate due to inflammation may be associated with HSV infections of the deeper tissue layers. With antiviral therapy, over the couple of week the HZV and shingles involving the outer layer of the cornea may resolve. However for months or years the person may feel painful burning sensation in the area of the skin rash.
This condition is referred to as postherpeutic neuralgia and sometimes to control pain, treatment may be required. Residual cornea scarring can be caused by both types of herpes eye infection that can blur the vision. Sometimes with surgery this can be corrected. Chronic numbs of the cornea, can be caused by damage to the corneal nerves. This may cause dry eyes and if the case is severe then it my further cause ulcers or predispose to dry eye related corneal erosions.
To protect the cornea, punctual plugs, lubricating drops and eyelid surgery may help. However in both the cases of HSV and HZV opthalmicus, the frequency in either eye cannot be predicted. To rule out any underlying condition that may make the immune system weak a general medical check up should be done to warrant frequent recurrences. However in some cases the activity level is determined by the virulence of the particular virus strain.