Herpes Simplex Keratitis Eye Infection
Herpes Simplex Keratitis or simply herpes keratitis (sometimes referred to as dendritic keratitis) is an infection of the cornea of the eye by the herpes simplex virus type 1 (HSV1), which can cause serious vision loss including blindness. It is estimated that 80% of the U.S. population harbors this virus! At least two thirds of those infected do not have outbreaks and recurrences or they are too mild to notice.
This article does not refer to Herpes Varicella Zoster virus that causes chickenpox or shingles or herpes zoster ophthalmicus. Please scroll the left side column to locate herpes zoster if you are searching that subject.
Cause of Herpes Keratitis
After a primary herpes infection the herpes virus is not destroyed and does not leave the body. The herpes simplex 1 virus simply remains dormant in the trigeminal ganglion in the area of the ears. The trigeminal ganglion is a mass of nerve cell bodies of the trigeminal nerve. The trigeminal nerve (fifth cranial nerve) provides sensory information for the face and some motor functions (chewing, swallowing). There are two trigeminal nerves, one on each side of the pons. Each trigeminal nerve has three major branches, the ophthalmic nerve , the maxillary nerve and the mandibular nerve.
The ophthalmic nerve provides neural sensation for the cornea of the eye as well as other surrounding structures. The maxillary nerve provides sensory signals for the upper lip, teeth, gums etc. The mandibular nerve provides the sensory signals for the lower lip, lower teeth and gums and other surrounding anatomical structures.
Therefore, when a stressor (fever, sunburn, injury, surgery) or reduced immune system allows the herpes virus out of latency and the virus becomes active and starts replicating, the virus usually travels from the trigeminal ganglion through the maxillary nerve to the upper lip or through the mandibular nerve to the lower lip. However, sometimes, the virus chooses the third option of the ophthalmic nerve and travels to the cornea of the eye where it can create a devastating infection with severe consequences.
Herpes Keratitis is usually NOT caused by genital herpes because that virus lies dormant in the sacral ganglion near the base of the spinal cord. However, it is worth noting that HSV1 can transfer to other parts of the body. For example, genital herpes (herpes simplex virus type 2) can be caused through oral sex when one’s lip is infected. Vice versa, genital herpes can be transferred to the lip during oral sex.
Signs & Symptoms of Herpes Keratitis
The following signs and symptoms occur in only one eye in a herpes simplex keratitis infection:
- Photophobia – light sensitivity
- Excessive Tearing/watery eyes
- Irritation and gritty feeling
- Eyelid swelling
- Foreign body sensation
- Eye redness
Treatment and Management of Herpes Keratitis
Herpes keratitis is often difficult for an eye doctor to diagnose. It is often called the “great masquerader” because the appearance of herpes keratitis can be misleading and doesn’t usually take on a classic appearance.
Treatment usually consists of Zirgan ophthalmic gel (Bausch & Lomb) applied topically to the eye or Valtrex or Acyclovir tablets taken orally. In some cases both Zirgan and Acyclovir are prescribed simultaneously. In some cases a corticosteroid eye drop is prescribed to minimize corneal scarring along with the Zirgan.
Other treatment may consist of “debridement” or scraping of the outer surface of the cornea (epithelial cells) to remove the infected tissue.
If the condition worsens into stromal keratitis, which is an infection deeper into the corneal layers, it often results in scarring and possible blindness.
Because herpes keratitis can often recur many eye doctors prescribe a continued preventive dose of valtrex or acyclovir because the risk of a subsequent herpes eye infection is worse than the potential risk from continued use of acyclovir.