Keratitis is an inflammation of the cornea, the outermost part of the eye. It usually is 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 is caused by other infections, such as bacteria, parasites and fungi.

Keratitis needs to be treated. Untreated cases can cause permanent eye damage. Nearly 50,000 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 Sjogren's syndrome) in which dryness or inflammation lead to irritation and injury of the cornea. Trauma to the front of the eye, as may occur with poorly fitting contact lenses, surgery on the cornea (including LASIK surgery), or any other injury to the cornea may lead to 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 professional will ask you about your symptoms, your vision, and your health in general. A history of immune problems, chickenpox or shingles, or arthritis may help your doctor diagnose keratitis. Your doctor, or an eye specialist, will use an instrument that magnifies the surface of the cornea to look for a tiny ulcer caused by viral infection. This ulcer tends to send out starlike 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. To help diagnose keratitis, your doctor also may:

• Test your visual sharpness and clearness (visual acuity)
• Test of how well your pupil responds to light
• Measure your cornea
• Examine your eye using a special instrument called a slit lamp
• Swab the eye or take samples from the eye to confirm the diagnosis of herpes simplex infection

Keratitis may be brief if it is caused by an infection that is fought off by the body (as with many viral infections) or treatable 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). Some infectious causes are resistant to treatment despite our best efforts and may lead to permanent damage and loss of sight.

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 because they 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 supplements can be used to treat keratitis related to vitamin A deficiency.

Keratitis caused by a rheumatic illness, such as rheumatoid arthritis, can be treated by treating the underlying disease, and using lubricating eye drops.

The seriousness of keratitis varies widely, but you should call your doctor promptly if symptoms develop, especially if you have 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% chance that the infection will return. It is important to pay attention to early symptoms so you can 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.

National Eye Institute
2020 Vision Place
Bethesda, MD 20892-3655
Phone: 301-496-5248
http://www.nei.nih.gov/