Keratitis is a condition where the cornea becomes inflamed, causing it to become red and painful. There are various causes of corneal keratitis, one of which is the herpes simplex virus.

Herpes generally spreads to the eye by touching an active lesion, such as a blister or a cold sore, and then your eye. Typically, an infection of the cornea, the transparent dome at the front of the eye, is the most common manifestation of ocular herpes. In fact, around 80 per cent of herpes infections in the eye are keratitis.

When the infection affects the outermost layer of the cornea, it is usually fairly harmless and will heal without long-term problems. However, if left untreated it can affect deeper layers and is more likely to result in scarring, which can lead to loss of vision and even blindness.

There are a number of symptoms associated with herpes simplex keratitis, including:

• Redness of the eye    
• Aches or pain in the eye     
• Watering     
• Blurred vision    
• Light sensitivity

Visiting an optometrist is important if you experience these symptoms, and they should be able to confirm the infection by examining your eye with a magnifier. The condition is characterised by small erosions on the cornea, which are called dendritic ulcers. This means the ulcer has finger-like branches rather than a smooth edge.

Treatment for ocular herpes will depend on the severity of the condition. Firstly, your optometrist may numb the eye with anaesthetic drops and then scrape away some of the infected cells.You will then be prescribed eye drops or ointment to remedy the infection. If the deeper layers of the cornea are affected, you may also be given steroid drops or antiviral medications. 

In the most severe cases, where scarring has caused significant vision loss or blindness, a corneal transplant may be the only option.