What Is It?

Keratitis is an inflammation of the cornea, the outermost part of the eye. It most commonly caused by the herpes simplex virus type 1, the same virus that causes cold sores. The infection usually begins by affecting the outer layer of the cornea, but it can go deeper into the cornea, increasing the risk of impaired vision. Other viruses that cause keratitis include varicella zoster (also a herpes virus), which is associated with chickenpox and shingles, and the adenoviruses, which cause upper respiratory infections. More rarely, keratitis results from other infections, such as bacteria, parasites and fungi.

Keratitis is usually easy to treat. Untreated cases can cause permanent eye damage. Nearly 50,000 new and recurring cases are diagnosed each year, and keratitis is the most common infectious cause of corneal blindness in the United States.

Other causes of keratitis include vitamin A deficiency and rheumatic diseases (such as rheumatoid arthritis and Sjögren’s syndrome) in which dryness or inflammation lead to corneal irritation and injury. Surgery on the cornea, including LASIK surgery, may be complicated by keratitis.


Symptoms of keratitis include:

  • Red eye
  • Sensation of something, like sand, in the eye
  • Pain
  • Sensitivity to light
  • Watery eye
  • Blurred vision

When caused by herpes simplex virus, keratitis usually affects only one eye, but both eyes may be affected when keratitis is due to other causes.


Your health care provider will ask you about symptoms regarding your eyes and your vision, but about your health in general. A past history of immune problems, chickenpox or shingles, or arthritis may be important in the evaluation of keratitis. Your doctor, or an eye specialist, will use an instrument that magnifies the surface of the cornea, looking for a tiny ulcer caused by viral infection. This ulcer tends to send out star-like branches, and is best seen after a dye is used to stain the cornea temporarily. Herpes simplex infection of the cornea may be accompanied by infection of the eyelid. In this case, tiny, painful blisters resembling cold sores of the lips may appear on the eyelid. Other ways to determine whether keratitis is present, and its severity, are tests of sharpness and clearness (visual acuity), the responsiveness of the pupil to light, corneal measurement and examination of the eye using a slit-lamp, a special instrument ophthalmologists and optometrists use to examine the eye. Swabs or other samples from the eye sometimes are taken to confirm the diagnosis of herpes simplex infection.

Expected Duration

Keratitis may be brief if caused by an infection that the body fights off (as with many viral infections) or by antibiotics (for bacterial or fungal infection). If keratitis is related to contact lenses, the duration tends to be brief. However, when it is caused by rheumatic disease or prior injury, keratitis may be long lasting (chronic).


If you have a cold sore, do not put your fingers to your eyes, because that could spread the infection. If there is any suspicion that you have herpes simplex virus, avoid over-the-counter steroid eye drops, which can make this infection worse. Routine contact lens hygiene, a balanced diet and moisturizing eye drops may prevent other causes of keratitis.


Antiviral eye drops will clear up the symptoms of herpes simplex virus. But even though the active infection is treated, the virus can flare up again because it remains in your system. In some serious cases, the doctor may apply anesthetic drops and gently scrape (debride) the diseased tissue off the cornea. After this procedure, you will wear an eye patch for a few days, and your doctor may put a soft contact lens in the eye as protection until the infection subsides. For other infections, antibiotics may be necessary.

Artificial tears for lubrication usually are effective for keratitis related to ocular dryness. Vitamin supplementation is effective for cases related to vitamin A deficiency. For rheumatic illness, such as rheumatoid arthritis, treatment of the underlying disease, along with lubricating eye drops, may be effective.

When To Call A Professional

The seriousness of keratitis varies widely, but you should call your doctor promptly if symptoms develop, particularly if you experience pain or your vision is impaired. Depending on how severe your symptoms are, your doctor may send you directly to an eye specialist (an ophthalmologist or an optometrist) who has special equipment for evaluating eye conditions. If your vision becomes poor in the affected eye, your doctor usually will send you immediately to an eye specialist.


Treatment is effective if started early. However, because the herpes simplex virus remains in the body, there is a 50 percent chance that the infection will recur. It is important to pay attention to early symptoms in order to begin treatment and prevent permanent eye damage. For other causes of keratitis, such as vitamin A deficiency and rheumatic diseases, it is possible for symptoms to improve or be cured.

Johns Hopkins patient information

Last revised:

Diseases and Conditions Center

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All ArmMed Media material is provided for information only and is neither advice nor a substitute for proper medical care. Consult a qualified healthcare professional who understands your particular history for individual concerns.