Overview

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, such as from wearing your contact lenses too long or getting a foreign body in the eye. 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 an eye specialist. 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.

Symptoms

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, called photophobia
  • A feeling that something is in your eye

When to see a doctor

If you notice any of the symptoms of keratitis, make an appointment to see an eye specialist right away. Delays in diagnosis and treatment of keratitis can lead to serious complications, including blindness.

Causes

Causes of keratitis include:

  • Injury. If any object scratches or injures the surface of your cornea, noninfectious keratitis may result. In addition, an injury may allow microorganisms to gain access to the damaged cornea, causing infectious keratitis.
  • Bacteria, fungi or parasites. These organisms may live on the surface of a contact lens or contact lens carrying case. The cornea may become contaminated when the lens is in your eye, resulting in infectious keratitis. Poor contact lens hygiene or contact lens overwear can cause both noninfectious and infectious keratitis.
  • Viruses. The herpes viruses — herpes simplex and herpes zoster — may cause keratitis.
  • Bacteria. Staphylococcus, streptococcus and pseudomonas are common bacteria involved in keratitis.
  • Contaminated water. Bacteria, fungi and parasites in water — particularly in oceans, rivers, lakes and hot tubs — can enter your eyes when you're swimming and result in keratitis. However, even if you're exposed to these organisms, a healthy cornea is unlikely to become infected unless there has been some previous breakdown of the corneal surface — for example, from wearing a contact lens too long.

Risk factors

Factors that may increase your risk of keratitis include:

  • Contact lenses. Wearing contact lenses — especially sleeping in the lenses —increases your risk of both infectious and noninfectious keratitis. The risk typically stems from wearing them longer than recommended, improper disinfection or wearing contact lenses while swimming.

    Keratitis is more common in people who use extended-wear contacts, or wear contacts continuously, than in those who use daily wear contacts and take them out at night.

  • Reduced immunity. If your immune system is weakened due to disease or medications, you're at higher risk of developing keratitis.
  • Corticosteroids. Use of corticosteroid eye drops to treat an eye disorder can increase your risk of developing infectious keratitis or make existing keratitis worse.
  • Eye injury. If one of your corneas has been damaged from an injury in the past, you may be more vulnerable to developing keratitis.

Complications

Potential complications of keratitis include:

  • Chronic corneal inflammation and scarring
  • Chronic or recurrent viral infections of your cornea
  • Open sores on your cornea, called corneal ulcers
  • Temporary or permanent reduction in your vision
  • Blindness

Prevention

Caring for your contact lenses

If you wear contact lenses, proper use, cleaning and disinfecting can help prevent keratitis. Follow these tips:

  • Choose daily wear contacts and take them out before going to sleep.
  • Wash, rinse and dry your hands thoroughly before handling your contacts.
  • Follow your eye care provider's recommendations for taking care of your lenses.
  • Use only sterile products that are made specifically for contact lens care, and use lens care products made for the type of lenses you wear.
  • Replace your contact lenses as recommended.
  • Replace your contact lens case every 3 to 6 months.
  • Discard the solution in the contact lens case each time you disinfect your lenses. Don't "top off" the old solution that's already in the case.
  • Don't wear contact lenses when you go swimming.

Preventing viral outbreaks

Some forms of viral keratitis can't be completely eliminated. But the following steps may control viral keratitis occurrences:

  • If you have a cold sore or a herpes blister, avoid touching your eyes, your eyelids and the skin around your eyes unless you've thoroughly washed your hands.
  • Only use eye drops that have been prescribed by an eye doctor.
  • Washing your hands frequently can reduce viral outbreaks.

Sept. 15, 2022
  1. What is a corneal ulcer (keratitis)? American Academy of Ophthalmology. https://www.aao.org/eye-health/diseases/corneal-ulcer. Accessed Aug. 25, 2022.
  2. Yanoff M, et al., eds. Bacterial keratitis. In: Ophthalmology. 5th ed. Elsevier; 2019. https://www.clinicalkey.com. Accessed Aug. 25, 2022.
  3. Basics of bacterial keratitis. Centers for Disease Control and Prevention. https://www.cdc.gov/contactlenses/bacterial-keratitis.html. Accessed Aug. 25, 2022.
  4. Cherry JD, et al., eds. Ocular infections. In: Feigin and Cherry's Textbook of Pediatric Infectious Diseases. 8th ed. Philadelphia, Pa.: Elsevier; 2019. https://www.clinicalkey.com. Accessed Aug. 25, 2022.
  5. Jacobs DS. The red eye: Evaluation and management. https://www.uptodate.com/contents/search. Accessed Aug. 25, 2022.
  6. Austin A, et al. Update on the management of infectious keratitis. Ophthalmology. 2017; doi:10.1016/j.ophtha.2017.05.012.
  7. What is bacterial keratitis? American Academy of Ophthalmology. https://www.aao.org/eye-health/diseases/what-is-bacterial-keratitis. Accessed Aug. 25, 2022.
  8. Basics of HSV (herpes simplex virus) keratitis. Centers for Disease Control and Prevention. https://www.cdc.gov/contactlenses/viral-keratitis.html. Accessed Aug. 25, 2022.
  9. Chodnicki KD (expert opinion). Mayo Clinic. Aug. 26, 2022.

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