Updated on 

November 2, 2021

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Keratitis

What is Keratitis?

Keratitis is the inflammation of the cornea (the clear outer layer of the eye that focuses light). 

Keratitis may be mild, moderate, or severe, and can be associated with inflammation of other regions of the eye. It may also involve one eye (unilateral) or both eyes (bilateral).1

Is Keratitis Contagious?

Some forms of keratitis can be infectious, but are not often transmitted to others. 

For example, the herpes simplex (which causes cold sores) and herpes zoster viruses (which causes chickenpox) are highly contagious and often transmitted via skin contact. 

After this initial infection, the virus then lives dormant in your body until reactivation, which is when keratitis may develop. 

The likelihood of passing herpes keratitis onto someone else is low, but you should still practice good hygiene like washing your hands often. If you have an active cold sore, do not touch your eyes.

However, keratitis caused by non-infectious elements such as eye injury may not be contagious unless an infection develops.

This condition can progress rapidly. If you suspect keratitis or have a problem with your eye, seek immediate medical advice.

Types of Keratitis

Keratitis is divided into two main types:

  • Infectious keratitis (microbial keratitis)
  • Noninfectious keratitis (caused by physical trauma, weak immunity, or exposure to extreme environmental elements) 

Infectious keratitis

Also known as microbial keratitis, infectious keratitis is caused by bacteria, fungi, viruses, or parasites.

Infectious keratitis is a leading cause of vision impairment and blindness worldwide, disproportionately impacting marginalized populations.2

  • Bacterial keratitis. Caused by bacteria, this form of keratitis occurs mainly due to improper and unhygienic use of contact lenses. The two types of bacteria associated with bacterial keratitis are Pseudomonas aeruginosa and Staphylococcus aureus.3
  • Fungal keratitis. Caused by fungi, this form occurs due to eye trauma, contact lens use, or underlying diseases. It's common in tropical and subtropical environments. The types of fungi involved include Candida species, Fusarium and Aspergillus.4
  • Viral keratitis.  This form of keratitis is caused by viruses, with common triggers being stress, weakened immunity, and exposure to direct sunlight.5 Unlike bacterial and fungal keratitis, this type can be chronic and frequent. Common viruses associated with viral keratitis include herpes simplex virus, varicella-zoster virus, and adenovirus.
  • Parasitic keratitis (or Acanthamoeba keratitis). This type is caused by a microscopic parasite known as Acanthamoeba, commonly found in water, soil, and air.6 It mainly affects those who wear contact lenses. However, it can also result from corneal trauma or exposure to contaminated water.

Non-infectious Keratitis

Non-infectious keratitis may result due to the following:

  • Eye injury
  • Weakened immune system
  • Extended-wear contact lens use
  • Allergens such as plant materials
  • Exposure to extreme environmental elements such as sunlight (photokeratitis or snow blindness)

Apart from the cause, keratitis can also be identified based on the appearance or region of the eye affected. These include the following:

  • Diffuse lamellar keratitis. This is a non-infectious refractive surgery complication. It is characterized by the accumulation of white blood cells and other inflammatory cells under the corneal flap created during LASIK surgery (eye laser surgery).7
  • Disciform keratitis. Associated with herpes simplex virus (HSV) and causes swelling in the center of the cornea.
  • Epithelial keratitis. This is a complication following cataract surgery. It appears in the form of tree-like or pointed lesions.
  • Filamentary keratitis. This condition is associated with corneal swelling and dry eyes. It's characterized by strands made up of epithelial cells and mucus on the surface of the cornea.
  • Punctate keratitis. This type of keratitis is associated with inflammation of the upper layer of the cornea. It is common among those with dry eye syndrome.
  • Ulcerative keratitis. Also known as peripheral ulcerative keratitis, this form manifests as crescent-shaped inflammatory damage to the cornea. It's linked to autoimmune diseases, including rheumatoid arthritis and lupus.

What Causes Keratitis?

Keratitis has many potential causes. The common causes include the following:

  • Bacteria such as Pseudomonas aeruginosa and Staphylococcus aureus
  • Fungi such as Candida, Fusarium, and Aspergillus species
  • Viruses such as varicella-zoster virus, herpes simplex virus, and adenovirus
  • Parasites such as Acanthamoeba 
  • Eye injuries such as a scratch or tear
  • Improper use of contact lenses such as wearing them for prolonged periods
  • Failure to clean contact lenses 
  • Wearing contact lenses when swimming
  • A weakened immune system that prevents the eye from fighting infections
  • Exposure to outdoor allergens and plant materials
  • Exposure to extreme sunlight (photokeratitis)
  • Underlying conditions such as dry eye syndrome or glaucoma

Keratitis Symptoms

The symptoms of keratitis will depend on the type a person is suffering from. However, the symptoms of keratitis include:

  • Eye irritation and pain
  • Red eye
  • Excessive tearing
  • Eye discharge
  • Sensitivity to light
  • Blurred vision or partial blindness
  • Inability to open the eyes

If you don't seek medical attention, keratitis symptoms are likely to progress and become worse over time.

How Keratitis is Diagnosed

It is important to get checked immediately whenever you suspect keratitis. Your eye doctor will discuss your history to determine any symptoms or underlying conditions.

During the diagnosis process, your eye doctor will use a slit lamp to magnify the structures in your eyes to detect any abnormalities.

The eye doctor may also use a penlight to assess your pupil for any unusual changes.

Laboratory analysis may be done to rule out infection and determine the exact cause of your eye keratitis.

Can Keratitis Heal on its Own? 

Keratitis can heal on its own if it's caused by an eye injury or a non-infectious factor like a weak immune system or extended wear contacts. 

However, you may use an antibiotic ointment to prevent the development of an infection during the recovery process.

If keratitis is caused by infectious elements such as bacteria, fungi, viruses, or parasites, it may not heal on its own. In this case, you may have to use medications.

Treatment for Keratitis 

Treatment for keratitis depends on the cause. 

Common treatment options for keratitis include:

  • Topical antibiotics for a bacterial infection
  • Antifungals such as oral voriconazole for fungal keratitis8
  • Antivirals such as trifluridine (USA) and Ganciclovir (Europe) for viral keratitis
  • Biocides such as chlorhexidine, biguanides and phosphocholine for parasitic keratitis

Keratitis is typically easy to treat and resolves quickly. However, if the infection spreads beyond the surface of your cornea, it may leave scars that impair your eyesight or possibly cause blindness.

In addition, not all types of keratitis respond well to treatment. For example, Acanthamoeba keratitis (caused by a parasite) can be difficult to treat and resistant to medications. 

Viral medications may also fail to fully eliminate the virus in the case of viral keratitis. Your doctor may need to conduct further eye examination and implement advanced treatment options if the infection persists.

If you get keratitis as a result of an injury, it will usually go away on its own as your eye recovers. However, you may be prescribed an antibiotic ointment to ease pain and prevent infection.

What Happens if Keratitis is Left Untreated?

If keratitis is left untreated, it may develop rapidly, resulting in severe eye damage or even vision loss. 

What is the Outlook (Prognosis) for Keratitis?

If you seek treatment early, you will likely recover quickly from keratitis. However, delayed treatment may lead to serious complications including:

  • Scars on the cornea
  • Long-term inflammation
  • Corneal ulcers (sores on the cornea)
  • Recurring infections 
  • Glaucoma (in rare cases)
  • Vision loss

Keratitis Prevention Tips

Below are tips to help you prevent development of keratitis:

  • If you're using contacts, follow the care regimen prescribed by your doctor
  • Always wash your hands thoroughly before touching your lenses
  • Replace your contact lenses as per your doctor's advice
  • Avoid sleeping with your contact lenses unless your optometrist recommends it
  • Avoid swimming in your contact lenses
  • Use daily wear contacts
  • Avoid touching your eyes if you have a sore or herpes blister
  • Only use doctor-prescribed eye drops
  • Contact your eye doctor immediately if you experience redness, eye pain, or blurry vision.
8 Cited Research Articles
  1. Acanthamoeba Keratitis,” Cleveland Clinic, 25 May 20121
  2. Update on the Management of Infectious Keratitis,” National Center for Biotechnology Information (NCBI), 21 September 2017
  3. Basics of Bacterial Keratitis,” Center for Disease Control and Prevention (CDC), April 7 2014
  4.  “Basics of Fungal Keratitis,” Center for Disease Control and Prevention (CDC), 10 October 2014
  5. Basics of HSV (Herpes Simplex Virus) Keratitis”,  Center for Disease Control and Prevention (CDC) 21 May 2021
  6. Parasitic keratitis – An under-reported entity,” National Center for Biotechnology Information (NCBI), 20 May 2020
  7. LASIK surgery: Is it right for you?,” Mayo Foundation for Medical Education and Research (MFMER)
  8. Topical and Oral Voriconazole in the Treatment of Fungal Keratitis,” National Center for Biotechnology Information (NCBI), 9 March 2009
Melody Huang is an optometrist and freelance health writer. Through her writing, Dr. Huang enjoys educating patients on how to lead healthier and happier lives. She also has an interest in Eastern medicine practices and learning about integrative medicine. When she’s not working, Dr. Huang loves reviewing new skin care products, trying interesting food recipes, or hanging with her adopted cats.
https://www.visioncenter.org/author/vince/
Author: Vince Ayaga  | UPDATED November 2, 2021
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Medical reviewer: Dr. Melody Huang, O.D.
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Dr. Melody Huang, O.D.
The information provided on VisionCenter.org should not be used in place of actual information provided by a doctor or a specialist.

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