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Aetiology

• Common pathogens
  • Staph. aureus, Streptococci (S. pyogenes, S. pneumoniae)
  • Pseudomonas (frequent in contact lens wearer)
• Pathogens that can penetrate intact corneal epithelium
  • N. gonorrhoeae, N. meningitidis, C. diphtheriae, H. influenzae

Risk Factors

• Contact lens wear (especially long wearing time, soft contact lenses, poor lens hygiene)
• Trauma
• Ocular surface diseases (herpes keratitis, dry eye, chronic blepharitis…)
• Local or systemic immunosuppressants
• Diabetes mellitus
• Vitamin A deficiency

Workup

• Photo documentation
• Specimen collection in case of
  • Infiltrate >1mm or affecting central visual axis or no response to initial therapy
  • In case of non-central infiltrate <1mm: Smear not mandatory due to only small probability of germ detection
  • Optimal: direct preparation, culture for bacteria + fungi, consider viral PCR (HSV, VZV)
• Consider sending in contact lens container including contact lens to microbiology
  • Especially if acanthamoebae are suspected, otherwise not very helpful, as containers are always contaminated

Management

• Infiltrate size < 1mm:
  • Floxal gtt (Ofloxacin) 5x/d to hourly and Floxal ointment at night
• Infiltrate size > 1mm:
  • Ceftazidim/Ofloxacin gtt hourly in the first 24 – 48h, thereafter, depending on response, reduce frequency during the day and switch to Floxal ointment at night
• Large/multiple infiltrates :
  • Cefta/Ofloxacin gtt initially every 15min (in the first 2-3h for rapid saturation), then hourly as described above
  • Consider inpatient admission depending on the size of the findings, if perforation is imminent or if there are compliance problems
• Consider additional scopolamine 0.25% AT 2x/d in case of (pronounced) cell flare in the anterior chamber, (reduces ciliary spasm, pain)
• Consider additional steroids if there is a lytic process with a risk of perforation
• Systemic antibiotics usually not indicated, may be necessary e.g. in case of severe corneal thinning with imminent or acute perforation or in case of scleral involvement
  • Ciprofloxacin 500mg 2x/d (good penetration into the cornea, also when administered orally)
• Systemic tetracyclines (e.g. doxycycline 100mg 2x/d) may be administered in cases of significant corneal thinning due to the anticollagenase effect
• Systemic antibiotics are indicated for potential systemic involvement in:
  • N. meningitides: benzylpenicillin i.m., ceftraxone or cefotaxime or ciprofloxacin orally
  • H. influenzae: oral amoxicillin with clavulanic acid
  • N. gonorrhoeae: ceftriaxone (a 3rd generation cephalosporin)
• Avoid contact lens wear!

Follow-up

• daily follow-ups until improvement
• Check-up after 1 day:
  • Response to therapy? (Less pain? Less redness/irritation of the eyes?)
• Check-up after 2 days:
  • Clinical signs of response to therapy? (Reepithelialisation? Decrease in anterior chamber cell flare? Better delineation or decrease in size of infiltrate?)
    • If clinical findings show a clear improvement: Consider reducing antibiotic therapy to 2 hourly during the day, Floxal ointment at night
    • If no improvement: possible causes: no response to therapy yet (too early), fungal keratitis, resistant pathogen.
• Check-up after 3-5 days:
  • Consider therapy adjustment depending on culture/sensitivity report
  • Decision on additional steroid therapy (no international consensus)
    • Goal: Minimise scarring
    • Prerequisite: confirmed diagnosis (not in fungal keratitis), confirmed clinical response to therapy with epithelialisation
    • e.g. Pred Forte gtt (Prednisolone) 4x/d for one week, reduce by 1 drop every week
• Further Follow-ups depending on the course

Sources

• EyeWiki Bacterial Keratitis
• The Wills Eye Manual: Office and Emergency Room Diagnosis and Treatment of Eye Disease; Nika Bagheri MD, Brynn Wajda MD, et al; Lippincott Williams&Wilkins; 7th Edition (2016)
• Kanski’s Clinical Ophthalmology: A Systematic Approach; Jack J. Kanski MD, Brad Bowling MD; Saunders Ltd.; 8th Edition (2015)