Viral Keratitis
A viral infection of the cornea that can recur and affect sight
Quick Facts
- Type: Eye (corneal) infection
- Most common cause: Herpes simplex virus
- Notable feature: Tends to recur
- Seek urgent care: Painful red eye with blurring or light sensitivity
Overview
Viral keratitis is an infection of the cornea, the clear front window of the eye, caused by a virus. The most common cause is the herpes simplex virus (the same virus that causes cold sores), and infections caused by the chickenpox and shingles virus (varicella-zoster) can also affect the eye.
A key feature of herpes-related keratitis is that it can lie dormant in nerves and flare up again, sometimes years after the first episode. Repeated attacks can scar the cornea and reduce vision, so accurate diagnosis and timely treatment matter. Importantly, steroid eye drops used without antiviral cover can make some viral keratitis much worse, which is why self-treating a red, painful eye is unsafe.
Viral keratitis covers a range of conditions. Herpes simplex tends to affect one eye and recur over a person's life. Shingles affecting the eye usually follows a painful, blistering rash on one side of the forehead or nose and can involve several parts of the eye. Adenovirus, the cause of the very contagious form of conjunctivitis, can sometimes spread to the cornea and leave small patches of inflammation that blur vision for weeks. Distinguishing these forms, and separating them from bacterial or fungal infection, guides the right treatment, since antivirals help viral disease but not other causes.
Symptoms
Symptoms usually affect one eye and may include:
- Eye pain or aching
- Redness
- Watering and a feeling of grittiness or a foreign body
- Blurred vision
- Sensitivity to light
- Reduced corneal sensation in some long-standing cases
People with herpes simplex keratitis may have a branching (dendritic) ulcer on the cornea that a doctor can see with dye and magnification. Shingles affecting the eye often follows a painful rash on the forehead, scalp, or around the eye on one side.
Causes
Viral keratitis is caused by viruses reaching or reactivating in the cornea:
- Herpes simplex virus (HSV): The leading cause. After a first infection, the virus stays dormant in nerves and can reactivate to infect the cornea again.
- Varicella-zoster virus: Reactivation as shingles can involve the eye (herpes zoster ophthalmicus).
- Adenovirus: The cause of highly contagious viral conjunctivitis, which can sometimes spread to involve the cornea.
Triggers for herpes reactivation can include stress, illness, fever, strong sunlight, and a weakened immune system.
Risk Factors
- A previous episode of herpes simplex keratitis (recurrence is common)
- Cold sores or prior herpes infection
- Shingles affecting the face or eye area
- A weakened immune system
- Use of steroid eye drops without antiviral protection
- Recent eye surgery or contact with someone with viral conjunctivitis
Diagnosis
An eye specialist examines the cornea with a slit lamp microscope. To diagnose viral keratitis they may:
- Apply fluorescein dye, which can reveal the branching dendritic ulcer typical of herpes simplex
- Test corneal sensation, which is often reduced in herpetic disease
- Take a sample for laboratory testing in unclear cases
- Look for an associated rash if shingles is suspected
The branching dendritic ulcer of herpes simplex is fairly characteristic and often allows a confident diagnosis on examination. When shingles is the cause, a painful, blistering rash on one side of the forehead or nose usually accompanies the eye symptoms and helps confirm it. Distinguishing viral keratitis from bacterial or fungal infection is important because the treatments differ, so in unclear cases a sample may be taken for testing. A careful history of cold sores, previous eye episodes, and any recent rash adds valuable context to the examination.
Treatment
Treatment depends on the virus and how deep the infection is, and is guided by an ophthalmologist.
- Antiviral medication: Antiviral eye drops, ointment, or oral antiviral tablets are used for herpes simplex and zoster infections.
- Careful use of steroids: Anti-inflammatory steroid drops are sometimes added, but only under specialist supervision and usually with antiviral cover, because they can worsen surface infection.
- Supportive care: Lubricating drops, pain relief, and protecting the eye while it heals.
- Preventing recurrence: People with frequent flare-ups may take long-term low-dose oral antivirals to reduce attacks.
Treatment length varies with the type and depth of infection. A surface herpes ulcer often clears within one to two weeks, while deeper inflammation or shingles affecting the eye may need weeks of carefully supervised treatment and gradual tapering of any steroid drops. Throughout, the eye is monitored closely to make sure it is improving and that eye pressure and inflammation stay controlled. Most episodes settle with treatment, but scarring from repeated attacks can gradually reduce vision and sometimes requires a corneal transplant. Because the underlying virus stays in the body, the goal is not only to treat the current episode but to reduce the chance and impact of future ones.
Prevention
- Take antiviral medication as prescribed if you have recurrent herpes eye disease
- Avoid rubbing or touching the eyes, and wash hands often
- Do not share towels, eye makeup, or contact lenses
- Never use leftover steroid eye drops for a red eye without medical advice
- Consider the shingles vaccine if eligible to reduce zoster eye disease
- Seek prompt 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 previous diagnosis of herpes keratitis and new symptoms
- A rash or blisters near one eye, which may signal shingles affecting the eye
- Symptoms that are worsening despite treatment
Early antiviral treatment protects the cornea and lowers the risk of lasting vision loss. Avoid self-treating with old eye drops.
Frequently Asked Questions
Can viral keratitis come back?
Yes. Herpes simplex keratitis is well known for recurring, sometimes years after the first episode, because the virus stays dormant in nearby nerves. People with frequent recurrences may be prescribed long-term antivirals to reduce attacks.
Is viral keratitis contagious?
The herpes and adenovirus that cause it can spread through close contact and shared items like towels or eye makeup. Good hand hygiene and not sharing personal items reduce the risk of passing it on.
Why are steroid eye drops risky in viral keratitis?
Steroid drops reduce inflammation but can let the surface herpes infection spread and worsen if used without antiviral cover. This is why a red, painful eye should be assessed by a doctor rather than treated with leftover drops.
How is viral keratitis treated?
Herpes-related viral keratitis is treated with antiviral eye drops, ointment, or tablets, sometimes alongside carefully supervised steroid drops. Treatment is guided by an eye specialist based on how deep the infection is.
Can viral keratitis cause blindness?
Most episodes heal with treatment, but repeated attacks can scar the cornea and reduce vision. Prompt antiviral treatment and follow-up greatly lower the risk of permanent damage.
References
- American Academy of Ophthalmology. Herpes Keratitis.
- National Eye Institute (NEI). Keratitis.
- Centers for Disease Control and Prevention (CDC). Genital Herpes and Herpes Simplex Virus.
- MedlinePlus, U.S. National Library of Medicine. Corneal injuries and infections.