Herpes Simplex keratitis (HSK) is a viral infection that if left untreated can have devastating ocular consequences.
Approximately 90% of the population over the age of 15 has been exposed to the type I herpes virus. This herpes simplex virus is contagious and can be transmitted by skin contact with others and from one part of the body to another (i.e. if one touches a cold sore then the eye, one can infect the eye).
Interesting enough, the corneal infection or “keratitis” form of the disease is not the bodies first contact with the virus. The initial infection (acute primary herpes simplex) most often occurs in childhood. The primary exposure to the virus may cause multiple whitish blisters around the eye termed viral eczema. Infrequently, a mild eye infection may be present. The acute primary herpetic infection is generally self limiting, meaning that within a given period of time, the infection resolves without any treatment or medical intervention. The primary exposure to the virus may be so subtle that it may not even be noticed.
It is the secondary herpetic infection, acute secondary herpes keratitis, which is more troubling for the eye. After the primary infection in childhood, the virus tends to remain dormant within the nerves of the body, especially the trigeminal nerve. The virus may become reactivated during emotional or physical stress, overexposure to ultraviolet light (i.e. tanning) and/or in conditions of immune-compromise (i.e. chronic diseases such as cancer, aids etc.). There are approximately 700,000 new cases of herpes simplex epithelial keratitis in the United States each year.
Signs and symptoms of secondary herpes keratitis include:
- Red painful eye
- Blurred vision
- Photophobia (sensitivity to light)
- General irritation.
These symptoms almost always occur in only one eye.
As the herpes infection progresses, the virus actually “deadens” the nerves of the cornea to the point where pain is no longer felt. This make people feel that the disease is getting better while actually the virus is proliferating and “eating” the corneal surface.
Secondary herpetic infections mainly affect the cornea producing what is called a dendritic keratitis or branching pattern. This is a photo of a corneal dendrite stained green with fluorescein. This represents the virus branching out to envelop more area of the corneal surface. If left untreated, the disease can lead to visually significant scarring, ulceration and/or deeper corneal penetration (stromal herpes) all of which can have site threatening consequences.
Treatment of herpes simplex keratitis involves the use of eye drops, systemic medications and/or ointments. The drop most often used for this condition is Viroptic® (generic: trifluridine), a potent antiviral agent. Vira A® (generic: vidarabine), an ophthalmic ointment may also be used in combination with Viroptic or on its own for the primary form of the disease. In some instances, systemic antiviral medications such as Zovirax® (generic: acyclovir) or Valtrex may also be used. It is important to note that topical steroid medications, at least initially, are contraindicated in the treatment of this dendritic keratitis. Steroids such as dexamethasone found in Tobradex and prednisolone acetate may promote the growth and expansion of the ocular surface disease.
A side note on Viroptic:
FDA Approves Pediatric Use For Viroptic
BRISTOL, TN — February 3, 1998 — The United States Food and Drug Administration has granted approval for the expanded use of King Pharmaceuticals, Inc.’s Viroptic (R) Ophthalmic Solution (trifluridine) 1%, to include pediatric patients, ages six and above.
Another concern with HSV keratitis is the risk of re-occurrence. A recent study published in the Archives of Ophthalmology (Aug 98) reports that the use of oral medications such as Zovirax for one year following the HSV episode, greatly reduces the rate of re-occurrence.