Eye Disorders: Herpes Simplex Virus Keratitis (corneal infection)
Herpes Simplex Virus Type 1 (HSV-1) is a very common viral infection of the cornea (keratitis means corneal inflammation). In the United States, random sampling reveals about 90% of people have been exposed to this virus, probably through "cold sores," which are HSV-1 infections of the lips and mouth. When a person is exposed, the virus takes up residence deep in the peripheral nervous system in "ganglia", where it remains for life. During one's life, it may migrate along a nerve to the skin or mucous membranes to cause active disease. Why the virus is quiet at times and active at others is a mystery in most cases, but may be related to illnesses or immunosupressive medication taken for other conditions. Herpes keratitis (meaning herpes corneal disease) is the leading corneal cause of vision loss in the United States.
The most common manifestation of HSV-1 is a cold sore or fever blister. A rarer but important manifestation of HSV-1 is corneal inflammation. There are several other types of Herpes viruses. Herpes Simplex type 2 causes sexually transmitted (genital) herpes, which rarely causes eye disease. Other viruses in the Herpes class include Varicella Zoster Virus (VZV) which causes chicken pox and shingles, Cytomegalovirus (CMV) which causes mononucleosis, and Epstein Barr Virus (EBV). VZV (Shingles) is also a common cause of eye disease.
How does HSV-1 affect the eye?
Most commonly, the first ocular HSV-1 infection is as an infection of the epithelium of the cornea, and sometimes also eyelid skin. The epithelium is the surface layer of the cornea. For perhaps most people, that one infection will be the only manifestation of ocular herpes during their lifetime. About 25-50% of people will have recurrent episodes, that may also involve the epithelium, but may also involve deeper parts of the eye. The stroma, which is the main body of the cornea under the epithelium, may become inflamed in different ways, some examples of which are disciform keratitis, necrotizing keratitis, and scarring. The inside of the eye can be involved as well, some examples of which include iritis, and retinal vasculitis. Interestingly, herpetic eye disease almost never involves both eyes.
What are the symptoms of a corneal herpes infection?
The symptoms are the same as many eye infections. Pain, sensitivity to light, blurry vision, red eye, and eye irritation are typical. The skin is usually not involved; but if so, blisters and redness may form along the eyelids. Recurrent herpes Keratitis carries a risk of corneal scarring and vision loss. For this reason, a person who has had herpes eye disease should always visit their eye doctor when the eye is red or irritated for prompt diagnosis and treatment.
How is herpetic corneal disease treated?
The Herpetic Eye Disease Study (HEDS) was a large, randomized study that guides most of the therapy of herpetic eye disease. This was an important study to help doctors understand the natural history of this condition and how to treat it's various manifestations. The common epithelial form is treated usually with a topical antiviral medication, called Viroptic. Alternatively, antiviral medication by mouth (Acyclovir, Famvir, Valtrex) can be used. For deeper involvement (stroma, for example), topical steroid eye drops may also be used. If corneal scarring develops that limits vision, a corneal transplant may be an option. However, herpes can recur in the new cornea as well.
If herpetic eye disease recurs more than once, prophylactic (preventative) antiviral medications by mouth may be recommended to help prevent recurrences. This therapy will decrease the chance of HSV recurring by about half.
More information on this condition can be found at the National Eye Institute's website, under the corneal section.