What is Infectious Keratitis?

Infectious keratitis is caused by various pathogens in the cornea producing inflammation. Many are vision threatening.

“Keratitis” is inflammation of the cornea (the clear covering of the eye). Infectious keratitis specifically refers to infection from bacteria, fungus, viruses, and parasites. Some types of keratitis are relatively common and keratitis is most common in contact lens wearers.  

Bacterial keratitis

Bacterial keratitis is usually caused by Pseudomonas aeruginosa or Staphylococcus aureus. This type of keratitis is seen mostly in people who use contact lenses improperly.

Common causes of bacterial keratitis in contact lens wearers is caused by:

  • Overnight wear
  • Not disinfecting contact lenses thoroughly
  • Not cleaning contact lens cases
  •  Storing or rinsing contact lenses in water
  • Using visibly contaminated lens solution
  • Topping off contact lens solution rather than discarding used solution and replacing. Topping off is when fresh contact lens solution is added to used solution already in a contact lens case.
  • Sharing colored or decorative contact lenses

Fungal keratitis

Fungal keratitis can be caused by 70 different fungi, but the most common fungi causing fungal keratitis are Aspergillus, Candida, and Fusarium. Fungal keratitis is often caused by an eye injury from a plant which allows the fungi that were on the plant into the eye. There is also a risk of developing fungal keratitis with improper contact lens use.

Parasitic keratitis

An organism called Acanthamoeba has become more common in the United States in those who wear contact lenses. This microscopic amoeba can be found worldwide in the water and soil. An eye infection from this parasite can be picked up by swimming in a lake or getting infected water on your contact lenses. This type of infection is called Acanthamoeba keratitis.

Most people will be exposed to the Acanthamoeba during their lifetime, but very few will become infected from the exposure.

If you wear contact lenses you can reduce your risk of acanthamoeba keratitis by:

  • Avoiding contact with contaminated water, which could include freshwater lakes, rivers and hot springs.
  • Filling your contact lens storage case with fresh solution each time you open it.
  • Never sleeping in your contact lenses.
  • Not showering, swimming in a freshwater lake, or using a hot tub while wearing contact lenses.
  • Not using another person’s contact lenses.
  • Replacing contact lenses regularly, according to your healthcare provider’s recommendations.
  • Using only disinfecting solution (not saline solution) to rinse and store your contact lenses — never use tap water.
  • Washing your hands before touching your eyes or handling your contact lenses.

Viral keratitis

This type of keratitis is primarily caused by the herpes simplex virus, which progresses from conjunctivitis to keratitis. The herpes simplex virus (HSV) is only found in humans and is passed on through direct contact with someone who is infected with the virus.

Viral keratitis or HVS keratitis affects approximately 1.5 million people around the world each year and is one of the most common causes of infectious blindness in the USA and Canada. HSV keratitis is commonly caused by touching a cold sore and then touching the eyes.

Symptoms of all types of keratitis include:

  • Eye pain
  • Watery eyes
  • Red, irritated or bloodshot eyes
  • Sensitivity to light (photophobia)
  • Blurry vision
  • Problems opening your eyelids because of pain or irritation.
  • The feeling that something is in your eye.

Treatments for the various types of keratitis:

Bacterial keratitis: Antibiotic eye drops are the primary treatment for bacterial keratitis. Depending on the severity of the infection, the frequency for instilling eye drops ranges from four times a day to every 30 minutes, even during the night. Sometimes oral antibiotics are also used.

Fungal keratitis: Antifungal eye drops and oral antifungal medication.

Acanthamoeba keratitis: Keratitis caused by the parasite acanthamoeba can be difficult to treat. Antiparasitic eye drops are used, but some acanthamoeba infections are resistant to medication and can require treatment for several months. Severe cases of acanthamoeba keratitis may require a cornea transplant.

Viral keratitis: Antiviral eye drops and oral antiviral medications may be effective.

When to see your doctor

If you have eye redness or any of the other symptoms of keratitis make an appointment to see your eye care specialist. With prompt treatment, mild to moderate cases of keratitis can usually be treated without vision loss.

If left untreated or if the infection is severe keratitis can lead to serious complications that may permanently damage your vision.

Gregory Scimeca, M.D.
Ophthalmologist and Medical Director
The Eye Professionals

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