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    Infectious Keratitis – Diagnosis and Treatment

    Cardinal Presentations / Presenting Problems, Ears, Eyes, Nose, and Throat, Infections

    Last Updated Dec 16, 2022
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    By John Ward, Jethro Moneo

    First 5 Minutes

    • Serious, potentially sight-threatening infection and inflammation of the cornea.
    • Can be ophthalmologic emergency as it can rapidly to vision loss due to scarring, ulceration, and/or corneal perforation.
    • Obtain visual acuity before performing any investigations or starting treatment.
    • Initiate treatment promptly once diagnosis made.
    • Withhold any corticosteroids until advised by ophthalmology.


    • Keratitis is a general term for inflammation of the cornea.
    • Can be infectious (bacterial, viral, fungal, amoebic, parasitic) or non-infectious.
    • Ophthalmology should be consulted in ED when any type of infectious keratitis is suspected as it can be severe and rapidly progress to sight threatening complications.
    • Pathogens
      • Bacterial: Staphylococcus, streptococcus, mycobacterium, pseudomonas (more common in contact lens wearers).
      • Viral: HSV, VZV (herpes zoster ophthalmicus).
      • Fungal: aspergillus, fusarium, candida.
      • Protozoan: acanthamoeba.
    • Complications include corneal scarring, perforation, development of anterior and posterior synechiae, glaucoma, cataracts.

    Diagnostic Process

    Clinical diagnosis

    • History
      • Risk factors
        • Contact lens (10x risk bacterial keratitis, especially in extended-wear lenses and people who leave on during sleep).
        • History of oral or genital herpes infection.
        • Previous ocular surgery or injury, recent trauma.
        • Topical or systemic steroids, or other immunosuppressant, diabetes.
        • Dry cornea (bell’s palsy or other conditions with incomplete eye closure).
        • Ocular trauma with exposure to plant material or dirt (associated with fungal or amoebic keratitis).
      • Symptoms
        • Ocular pain or foreign body sensation.
        • Photophobia.
        • Blurred vision.
        • Tearing.
      • Physical Exam
        • Visual acuity – can be decreased if central ulcer or uveal tract inflammation.
        • Inspection
          • Can monocular or binocular involvement.
          • Red, irritated eyelids.
          • Discharge
            • Bacterial: Mucopurulent.
            • Viral: watery.
          • VZV: often associated with dermatomal rash involving the forehead, tip of nose and/or upper eyelid (shingles), iritis, uveitis, and/or choroiditis.
          • HSV: May have associated typical herpetic eruptions on eyelid/surrounding skin with palpable preauricular lymph node.
          • Bacterial: can often see a corneal ulcer without a slit lamp.
        • Slit lamp (examine first without fluorescein, then with):
          • Bacterial: Round or irregular ulcer with a hazy white base and heaped up edges.
          • Viral
            • VZV: associated iritis or uveitis.
            • HSV: Dendritic patterned lesions (branches with terminal bulbs).
          • Fungal: On slit lamp, serrated “feathery” infiltrate margins, raised slough.
          • Parasitic: large, round fluorescein-enhanced circular lesion.
        • Pupillary, visual field, extraocular movement examinations should be normal.
        • Ophthalmology may scrape center of ulcer to culture the organism.

    Recommended Treatment

    Bacterial keratitis

      • Referral to Ophthalmology at time of diagnosis.
      • Aggressive antibiotic treatment:
        • In contact lens wearer:
          • Gatifloxacin or moxifloxacin 1 drop q1-2hrs; OR
          • Tobramycin 14mg/mL topical AND ceftazidime 50mg/mL topical q5min for first hr, then q15-60min for 24-72 hrs then slowly reduce; OR
          • Ciprofloxacin 0.3% ophthalmic solution topically for same dosing schedule (though resistance to fluoroquinolones increasing).
        • In non-contact lens wearer
          • Gatifloxacin or moxifloxacin 1 drop q1-2hrs; OR
          • Tobramycin 14mg/mL topical AND Cefazolin 50mg/mL topical q5min for first hr, then q15-60min for 24-72 hrs then slowly reduce; OR
          • Vancomycin 50mg/mL AND ceftazidime 50mg/mL at same dosage.
        • Duration generally 3-4 weeks guided by ophthalmology.


    Viral Keratitis

      • Prompt initiation of topical antivirals.
      • HSV
        • Debridement recommended – referral recommended.
        • The only topical agent available in Canada, Viroptic (trifluridine 1%) will be discontinued. Oral antivirals are your best bet.
          • Viroptic (trifluridine 1%) 1 drop every 2 hours while awake up to 9 times a day for 7 days (if available).
        • Oral antivirals; Acyclovir 400mg po 5x/day x 10 days; Valacyclovir 500 mg twice daily for 10 days or Famciclovir 250 mg po BID 10 days.
      • VZV
        • Treatment should be initiated within 72hrs of onset of skin lesions.
        • Famciclovir 500mg po tid x 10 days or Valacyclovir 1g po tid x 10 days.
      • Do not prescribe topical steroids without ophthalmologist approval.
        • For stromal and endothelial keratitis, ophthalmology may prescribe topical corticosteroids and prolonged oral antiviral therapy.
      • Fungal, protozoan, or parasitic keratitis suspected:
        • Contact ophthalmology for diagnosis and treatment.
      • General:
        • Do not patch eye due to risk of pseudomonas infection, and no proven benefit.
        • If contact lens wearer, discontinue until infection resolves.

    Criteria For Hospital Admission

    • Generally not required, however consider hospitalization for initial period of frequent dosing, if infection is sight-threatening or treatment compliance is a concern due to patient age or disability or lack of support.
    • If concern for corneal perforation (positive Seidel test), ophthalmology may choose to admit for surgical intervention.

    Criteria For Transfer To Another Facility

    Transfer not required for infectious keratitis.

    Criteria For Close Observation And/or Consult

    All patients with suspected infectious keratitis should be referred to ophthalmology.

    Criteria For Safe Discharge Home

    • Discharge instructions and considerations.
    • Patients with infectious keratitis can be safely discharged after ophthalmology consultation in the ED, with ophthalmology follow up arranged.

    Quality Of Evidence?


    Monotherapy with fluroquinolone recommended for bacterial keratitis is a STRONG recommendation based on HIGH quality evidence that it is as effective as combined antibiotics.


    Addition of topical ophthalmic corticosteroids to antibiotics may not affect clinical outcome, based on HIGH quality evidence based on a 2014 Cochrane review.


    Related Information


    Reference List

    1. Bugs&Drugs. Ophthalmic Infections: Keratitis [Internet]. Bugs and Drugs. 2022 Available from: https://www.bugsanddrugs.org/26400D98-0622-4B24-B2C4-E424F1EC1050

    2. Hogrefe C. EM:RAP CorePendium [Internet]. Keratitis. 2022 [cited 2022 Dec 7]. Available from: https://www.emrap.org/corependium/chapter/recdLUKfb1cY8ZJak/Keratitis#h.rvj07p84mpxr

    3. Go S. Chapter 149. Ocular Emergencies. In: Cline DM, Ma OJ, Cydulka RK, Meckler GD, Handel DA, Thomas SH, editors. Tintinalli’s Emergency Medicine Manual [Internet]. 7th ed. New York, NY: The McGraw-Hill Companies; 2012. Available from: accessemergencymedicine.mhmedical.com/content.aspx?aid=56279532

    4. DynaMed. Keratitis. EBSCO Information Services. https://www.dynamed.com/condition/keratitis


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