Keratitis

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

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.

Diagnosis

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.