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.
Sep. 20, 2012

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