Herpes Simplex Keratitis
"Herpes Simplex (HS) Keratitis" is an infection affecting the front of the "cornea", the dome-shaped structure at the front of the eye. The infective agent is "Herpes Simplex Virus (HSV)", which is the same virus that causes cold sores and fever blisters in and around the mouth and nose. It has been estimated that 85% to 95% of the adult population harbors the virus, although it usually lies dormant in a nerve that supplies the eye and skin.
HS Keratitis can be activated or triggered by a mild injury to the eye, exposure to excessive sunlight, stress, or an illness with fever.
Symptoms and Signs
Once the infection has been triggered, it may run its course and disappear, in much the same way that cold sores do, but the HS infection tends to recur; such recurrences are prone to complications, the most characteristic of which is a type of corneal eruption called a "dendritic corneal ulcer".
The word "keratitis" implies an inflammatory process instead of an infection, but in this particular case, the difference isn’t significant. The corneal disruption called a dendritic ulcer causes a red, watery eye scratchiness and discomfort, light sensitivity, pain and decreased vision.
The typical dendritic ulcer may be about 1/25 of an inch long, which may have branches coming from it so it looks something like a lightning bolt or the branches of a tree limb. The ulcer cannot be seen with the naked eye, but must be evaluated by an eyecare practitioner using a biomicroscope or slit lamp, a specialized microscope with controlled lighting that allows a clear view of the structures of the front of the eye. The eyecare practitioner will usually view the cornea with the slit lamp using fluorescein dye, which mixes with the tears and reacts to blue light by glowing. The ulcer gathers the dye and shows its structure quite clearly.
People with HSK can also have decreased corneal sensitivity, so that may be tested as well, along with best corrected vision and careful consideration of other factors to rule out other types of infection.
Several anti-viral eyedrops may be prescribed, which must be used frequently during the day (sometimes even hourly at the beginning), and an ointment at night. (Ointments are used during the night because they stay in the eye much longer and blur the vision significantly.) You may also be given eyedrops that dilate the pupil of the affected eye which helps decrease discomfort.
HS is extremely contagious, so anyone with it should always wash hands after touching the eye, and be careful not to touch the medication bottle to any surface, especially the eye itself. Keep all medications away from children and do not share your medication with anyone else.
In spite of immediate and best treatment, sometimes the virus just does not respond to the eyedrops and may infect the tissues deeper in the cornea. If this happens, different medications may be added to the regime of treatment and could be necessary for weeks to months. Rarely, extreme cases of corneal scarring will develop and may require a corneal transplant to restore vision.
Prevention of Recurrence
HSK sometimes appears to be well under control, only to break out again months or even years later, in the same spot, just as cold sores tend to do. It may run the same course as it did in the initial episode, although it may be more resistant to treatment than the first time.
Some strategies to avoid triggering a recurrence of HSK include:
- Use sunglasses whenever you are in sunlight
- Make sure every eyecare practitioner that you see knows you have a history of HSK
- Avoid eyedrops with steroids in them, especially if they were not prescribed for you
- Get to the eyecare practitioner as soon as possible if you suspect a recurrence
- Treat every case of conjunctivitis (commonly known as “pinkeye”) as if it is a recurrence and get treatment immediately
Other Herpes Types
There are several types of herpes simplex viruses, one of which is transmitted through sexual activity with an infected person; this is herpes simplex type II. The virus which affects the eyes and facial areas is herpes simplex type I.
Herpes Zoster is another type of virus, identical to the one that causes chickenpox. This does occasionally affect the cornea, but does so in a different way than herpes simplex, so it has a different course of progression and requires different management than simplex infections.