Keratitis is an inflammation of the cornea — the clear, dome-shaped tissue on the front of your eye that covers the pupil and iris. Keratitis may or may not be associated with an infection. Noninfectious keratitis can be caused by a relatively minor injury, wearing your contact lenses too long or other diseases. Infectious keratitis can be caused by bacteria, viruses, fungi and parasites.
If you have eye redness or other symptoms of keratitis, make an appointment to see your doctor. With prompt attention, mild to moderate cases of keratitis can usually be effectively treated without loss of vision. If left untreated, or if an infection is severe, keratitis can lead to serious complications that may permanently damage your vision.
Causes of keratitis include:
- Injury. If an object scratches the surface of one of your corneas or penetrates a cornea, keratitis without an infection may result. In addition, an injury may allow bacteria or fungi to gain access to the cornea through the damaged surface, causing keratitis that involves an infection.
- Contaminated contact lenses. Bacteria, fungi or parasites — particularly the microscopic parasite acanthamoeba — may inhabit the surface of a contact lens and contaminate the cornea when the lens is in your eye, resulting in infectious keratitis.
- Viruses. Viruses such as the herpes viruses (herpes simplex and herpes zoster) and the virus that causes chlamydia may cause keratitis.
- Contaminated water. Chemicals in water such as those used in swimming pools may irritate the cornea and cause irritation and a physical breakdown of the delicate surface tissue of the cornea (corneal epithelium), resulting in a chemical keratitis. This is usually transient and may last only minutes to hours. Bacteria, fungi and parasites in water — particularly in oceans, rivers, lakes and hot tubs — can enter your eyes when you’re swimming or bathing and result in keratitis. However, even if you’re exposed to these bacteria, fungi or parasites, a healthy cornea is unlikely to become infected unless there has been some previous breakdown of the corneal epithelium. For example, physical breakdown of the corneal epithelium from wearing a contact lens too long may allow the cornea to become vulnerable to infection.
Signs and symptoms of keratitis include:
- Eye redness
- Eye pain
- Excess tears or other discharge from your eye
- Difficulty opening your eyelid because of pain or irritation
- Blurred vision
- Decreased vision
- Sensitivity to light (photophobia)
- A feeling that something is in your eye
When to see a doctor
If you notice any of the signs or symptoms of keratitis, make an appointment to see your doctor right away. Delays in diagnosis and treatment of keratitis can lead to serious complications, including blindness.