Keratitis (KEHR-ah-TI-tis) is an inflammation or irritation of the cornea, often characterized by a cloudiness or loss of luster in this transparent membrane covering the iris and pupil. There are many types, causes and degrees of severity of keratitis. Generally, the infection occurs after the cornea has been injured or penetrated, allowing bacteria or fungi to enter and the deeper the infection, the more severe its symptoms and complications.

Keratitis affects about 50,000 Americans each year, most of them recurring cases. It is usually easy to treat – typically with antiviral or antibiotic eye drops – but prompt treatment is important; untreated cases can cause permanent eye damage and help give keratitis the dubious distinction of being the most common cause of infection-caused corneal blindness in the U.S.

Among the most common types is herpes simplex keratitis, caused by the same herpes simplex virus that causes cold sores. This infection usually begins with an inflammation of the conjunctiva, the membrane lining the eyelid, and the portion of the eyeball that comes into contact with it. Subsequent infections, called "dendritic keratitis," are characterized by a pattern of lesions that resemble the veins of a leaf. Those who have been diagnosed with the herpes simplex virus need to be vigilant, since when untreated, this form of keratitis can be serious – leading to vision loss, corneal scarring, chronic inflammation and glaucoma. Herpes-caused recurrences are common, and can be triggered by stress, fatigue or even exposure to outdoor activities such as boating and skiing, in which sunlight reflects off of the surfaces such as water and snow.

Other viruses that cause keratitis include the varicella zoster virus (also a herpes virus), which is associated with chickenpox and shingles, and the adenoviruses, which cause upper respiratory infections.

Bacterial keratitis is caused by bacteria, often resulting from improper care and cleaning of contact lenses or wearing soft daily-wear lenses overnight (which increases risk about 10-fold, according to some research). Contaminated eye makeup can also cause bacterial keratitis. This type of infection is usually aggressive, characterized by waking up with your eyelids stuck together.

Other forms of keratitis result from vitamin A deficiency, poor hygeine, a reaction to antibiotics medications, or rheumatic diseases such as rheumatoid arthritis and Sjögren’s Syndrome, in which eye dryness can lead to a greater susceptability toward corneal irritation and injury.

Symptoms

The number and severity of symptoms may vary, but typically you may experience:

• Pain
• Blurred vision or reduced clarity
• Eye redness, itching or watering
• A feeling as if something was in your eye
• Eye discharge
• Sensitivity to light

Prevention

Many cases of keratitis could be avoided with common sense and good hygiene. Protecting your cornea from cuts with sports and protective eyewear is the first step, since keratitis also results from a corneal injury. If you have a cold sore or genital herpes, avoid touching your eyes – and avoid over-the-counter steroid eyedrops, which can worsen this type of infection. If you have daily-wear contact lenses, remove them nightly and follow the cleaning recommendations by the manufacturer. Also avoid sharing eye makeup.

If you’re prone to dry eye or have a rheumatic condition, keep eyes "hydrated" with moisturizing eye drops recommended by your eyecare provider. Also consume a well-balanced diet, including vitamin A-rich foods such as carrots, squash, mangoes, sweet potatoes and other orange-colored produce; organ meats such as beef or lamb liver; and spinach.

Treatment

Prompt treatment by your eyecare provider is important to determine the specific type of keratitis – and its most effective treatment. You will be asked questions about your symptoms, your lifestyle, and your overall health. A history of cold sores, chickenpox, shingles or arthritis are important in the evaluation. Your doctor will then examine the surface of the cornea, looking for a tiny ulcer or other abnormalities.

Antiviral eyedrops are typically used to treat symptoms in cases caused by the herpes simplex type 1 and other viruses, but these cases can recur because the virus may remain in your body. In severe cases, your doctor may scrape off disease tissue after applying anesthetic eyedrops. After wearing an eyepatch, you may have to wear a special contact lens to prevent re-infection.

Oral or eyedrop antibiotics are used for other infections, and if you wear contact lenses, you may be advised to replace your lenses. For cases caused by dry eye, artificial tears for lubrication are usually effective. Vitamin supplementation is given in cases where a vitamin A deficiency is the suspected cause.