What is herpes simplex keratitis?
Up to 90% of people in the UK have an inactive nerve infection caused by herpes simplex virus type 1. This infection is usually acquired in childhood by contact with an adult. The viruses penetrate the skin and travel along the nerves of sensation to the central part of the nervous system (brain or spinal cord) where they become ‘latent’ and produce no symptoms. The infection cannot be eliminated and there is no protective vaccine. Another variety, herpes simplex type 2, is usually sexually transmitted, but can also affect the eye.
The infection remains inactive until some factor such as poor health, disturbance of the body’s immune system or certain drugs allow the virus to become active and then travel back down the nerves to the surface of the body. If this happens in the trigeminal nerve (the nerve that gives sensation to the head and neck), an infection of the skin such as a cold sore on the lip, or an infection of the eye surface, can occur. If the cornea (the clear window at the front of the eye) is involved, the condition is known as Herpes Simplex Keratitis. Usually only one eye is affected.
Several different forms of corneal infection are possible, ranging from slight to severe. One of them, affecting the surface skin of the cornea, produces ulcers with a characteristic branching outline and this is known as a dendritic ulcer. The infection can recur and if this happens scarring may result, which can cause blurring of vision.
How is herpes simplex keratitis managed?
A new case, with involvement of the surface skin of the cornea only, will usually be treated by the optometrist with anti-viral eye ointment. In children, contact lens wearers and where the condition affects both eyes, same-day referral to the ophthalmologist is recommended. This is a condition which tends to recur from time to time. Recurrences involving only the surface skin of the cornea can often be managed by the optometrist, who will usually prescribe anti-viral eye ointment, but if this is not effective after a week, urgent referral to the ophthalmologist is recommended. If the vision has become badly affected by scarring of the cornea, a patient may be offered a corneal transplant.
