What is the treatment approach for keratitis?

Treatment Approach for Keratitis

The treatment of keratitis must be tailored to the specific causative organism, with bacterial keratitis typically requiring intensive topical antibiotics (such as fluoroquinolones or fortified antibiotics), fungal keratitis requiring natamycin 5% suspension, and viral keratitis requiring antivirals with appropriate adjunctive therapy. 1, 2, 3

Diagnosis and Initial Assessment

• Obtain corneal scrapings for smears and culture before initiating antimicrobial therapy
• Determine the likely causative organism based on clinical presentation and risk factors
• Consider additional diagnostic methods for challenging cases:
  • In vivo confocal microscopy (for fungal and Acanthamoeba)
  • PCR testing (especially for viral and atypical cases)

Treatment by Causative Organism

Bacterial Keratitis

For central or severe bacterial keratitis (deep stromal involvement, infiltrate >2mm, extensive suppuration):

1. Initial therapy:

   • Single-drug therapy with fluoroquinolone OR combination therapy with fortified antibiotics 1
   • Loading dose: Apply every 5-15 minutes followed by hourly applications
   • Consider fortified topical antibiotics for large/visually significant infiltrates, especially with hypopyon

2. Medication options:

   • Fluoroquinolones (moxifloxacin 0.5%, gatifloxacin 0.3%, levofloxacin 1.5%, ciprofloxacin 0.3%, ofloxacin 0.3%) 4
   • For Gram-positive cocci: Cefazolin is preferred 5
   • For Gram-negative rods: Gentamicin is preferred 5

3. Adjunctive therapy:

   • Cycloplegic agents to decrease synechiae formation and pain, especially with anterior chamber inflammation 1
   • Topical corticosteroids may be considered after infection control (safe when used with appropriate antibiotics) 6, 7

Fungal Keratitis

1. Initial therapy:

   • Natamycin 5% ophthalmic suspension (preferred treatment) 2, 3, 7
   • Dosing: One drop hourly or every two hours initially, then reduce to 6-8 times daily after 3-4 days 2
   • Continue for 14-21 days or until resolution of active fungal keratitis 2

2. Important considerations:

   • Gradually reduce dosage at 4-7 day intervals to ensure elimination of the organism 2
   • Avoid corticosteroids as they may be harmful in fungal keratitis 6
   • For Fusarium keratitis specifically, natamycin is superior to voriconazole 7

Viral Keratitis (Herpes Simplex)

1. Treatment approach:
   • Topical antivirals for epithelial disease
   • Combination of topical corticosteroids and oral acyclovir for stromal keratitis 7
   • Oral acyclovir for prophylaxis to prevent recurrence 7

Acanthamoeba Keratitis

1. Initial therapy:
   • Polyhexamethylene biguanide or chlorhexidine 3
   • Avoid corticosteroids before initiating anti-amoebic therapy 6

Treatment Duration and Monitoring

• Daily follow-up until clinical improvement is confirmed 4
• Continue therapy for bacterial keratitis until resolution
• For fungal keratitis, continue for 14-21 days 2
• Monitor for positive response indicators:
  • Reduced pain
  • Decreased discharge
  • Lessened eyelid edema or conjunctival injection
  • Sharper demarcation of stromal infiltrate
  • Initial re-epithelialization
  • Reduced anterior chamber inflammation 4

Common Pitfalls to Avoid

1. Inadequate dosing frequency or premature discontinuation of therapy 4
2. Delayed modification of ineffective therapy (consider culture results after 48-72 hours) 4, 8
3. Inappropriate corticosteroid use before infection control 4, 6
4. Failure to eliminate predisposing factors (contact lens wear, ocular surface disease) 8
5. Misdiagnosis of the causative organism 8

Special Considerations

• For treatment-resistant bacterial keratitis, consider antibiotic susceptibility testing including imipenem, colistin, and linezolid 8
• Corneal crosslinking may be an emerging option for superficial bacterial keratitis 8
• Systemic antibiotics may be necessary for scleral/intraocular extension of infection or impending corneal perforation 1, 4
• Bandage contact lenses should be used cautiously due to increased risk of infection, with regular lens exchange if prolonged use is required 1