Herpes Simplex Keratitis

Overview

Herpes simplex keratitis is an infection of the cornea caused by the herpes simplex virus (HSV), the same family of virus that causes cold sores. The cornea is the clear, dome-shaped window at the front of the eye that focuses light, so infection there can blur vision and, over repeated episodes, leave permanent scarring. It is one of the most common infectious causes of corneal damage and a leading infectious cause of vision loss in one eye in many countries.

Most people are exposed to the herpes simplex virus at some point, often without ever knowing it. After a first infection, the virus does not leave the body; instead it travels along nerves and lies dormant, where it can reactivate later and reach the eye. This is why herpes simplex keratitis is characteristically a recurring condition, with attacks that may come months or years apart.

Different forms exist. The most common is a surface infection that produces a branching ulcer and usually heals well with antiviral treatment. Deeper forms involve inflammation within the layers of the cornea and need careful, specialist management. Importantly, steroid eye drops used without antiviral protection can make the surface form worse, which is why self-treating a red, painful eye with leftover drops is unsafe.

Symptoms

Symptoms usually affect one eye and may include:

• Eye pain or aching
• Redness
• Watering and a gritty, foreign-body feeling
• Blurred vision
• Sensitivity to light
• Reduced corneal sensation in long-standing cases

A characteristic finding is a branching, tree-like (dendritic) ulcer on the cornea that a doctor can reveal with fluorescein dye and magnification. Recurrent episodes often feel similar to previous ones, and many people learn to recognize their own early warning signs. Deeper, stromal forms may cause more blurring and a longer-lasting ache rather than the surface grittiness of a simple ulcer. Because reduced corneal sensation can blunt pain, the severity of symptoms does not always match the severity of the infection, which is another reason to seek assessment rather than wait.

Causes

The condition is caused by herpes simplex virus infecting the cornea. Most people are exposed to HSV at some point in life. After the initial infection, the virus remains latent in nerve tissue and can reactivate to reach the eye.

Common triggers for reactivation include:

• Physical or emotional stress
• Fever or other illness
• Strong sunlight or ultraviolet exposure
• A weakened immune system
• Eye surgery or trauma

Risk Factors

• A previous episode of herpes simplex keratitis
• History of cold sores or HSV infection
• A weakened immune system
• Use of steroid eye drops without antiviral cover
• Recent eye surgery or injury

Diagnosis

An eye specialist examines the cornea with a slit lamp microscope. To confirm the diagnosis they may:

• Apply fluorescein dye to reveal the typical branching dendritic ulcer
• Test corneal sensation, which is often reduced
• Take a sample for viral testing in uncertain cases
• Review the history of cold sores or previous eye episodes

The branching dendritic ulcer is fairly distinctive and often allows the diagnosis to be made on examination alone. In deeper or less typical cases, the doctor weighs the history, the appearance, and the response to treatment, and may take a sample for laboratory confirmation. Identifying which layer of the cornea is involved is important, because a surface ulcer and deeper inflammation are treated differently, the former mainly with antivirals and the latter sometimes with carefully supervised steroid drops alongside antivirals.

Treatment

Treatment depends on which layer of the cornea is affected and is supervised by an ophthalmologist.

• Antiviral medication: Antiviral eye drops, ointment, or oral tablets clear the active virus.
• Careful use of steroids: For deeper inflammation, anti-inflammatory drops may be added under specialist supervision, usually with antiviral cover, never alone for a surface ulcer.
• Gentle debridement: Sometimes the infected surface cells are removed by a specialist.
• Preventing recurrence: Long-term low-dose oral antivirals can reduce the frequency of attacks in people with recurrent disease.

How long treatment lasts depends on the form. A surface ulcer often heals within one to two weeks of antiviral therapy, while deeper inflammation can require weeks of carefully tapered drops and close monitoring. Repeated or deep episodes can scar the cornea and, over time, reduce vision; a small number of people eventually need a corneal transplant to restore sight. Even after a successful transplant, antiviral medication is usually continued because the virus can still reactivate. Attending follow-up appointments and starting treatment early in each flare are the most effective ways to protect long-term vision.

Prevention

• Take antiviral medication as prescribed if you have recurrent eye herpes
• Avoid rubbing the eyes and wash hands regularly
• Do not share towels, eye makeup, or contact lenses
• Protect eyes from strong sunlight, a known trigger
• Never use leftover steroid eye drops for a red eye without medical advice
• Seek care at the first sign of a flare-up

When to See a Doctor

See an eye doctor urgently, ideally the same day, if you have:

• A painful red eye with blurred vision or light sensitivity
• A known history of eye herpes and new or returning symptoms
• Symptoms that worsen despite treatment

Prompt antiviral treatment protects the cornea and reduces the risk of scarring and vision loss. Avoid self-treating with old eye drops, which can make the infection worse.

Related Topics

Frequently Asked Questions

References

1. American Academy of Ophthalmology. Herpes Keratitis.
2. National Eye Institute (NEI). Keratitis.
3. MedlinePlus, U.S. National Library of Medicine. Corneal injuries and infections.
4. Centers for Disease Control and Prevention (CDC). Herpes Simplex Virus.