Keratitis refers to an inflammation of the cornea. Infection of the cornea is called infectious keratitis. It is the most serious complication of contact lens wear and can cause blindness.

Bacterial keratitis is the most common type of infectious keratitis. Overall, bacterial keratitis is among the least frequent complications of wearing contacts, but it is much more common in people with extended-wear soft lenses, especially those who wear the lenses overnight.

Many eye professionals no longer recommend continuous use of extended-wear lenses. Some recommend avoiding overnight wear completely. The recommended wearing time for extended-wear lenses has been cut from 30 days to 7 days.

On rare occasions, viruses and fungi may cause keratitis. A germ that is often present in tap water causes a form of keratitis that is increasingly seen in contact lens wearers, especially those with soft lenses.

Noninfectious causes of keratitis in contact lens wearers include:

• Injury (from a blow, scratch, or foreign object).
• Chemicals, including those in contact lens solutions.
• Physiological factors, such as an allergic reaction to deposits on the lenses.

If you wear contact lenses and you have a painful, red eye, you may have infectious keratitis. Remove your lenses and call your doctor immediately. Symptoms of bacterial keratitis include:

• Pain and redness in the eye.
• Tearing and painful sensitivity to light.
• Sometimes, discharge or decreased vision.