What is the appropriate treatment for a patient presenting with keratitis?

Treatment of Keratitis

Initiate empiric broad-spectrum topical antibiotic therapy immediately for suspected bacterial keratitis, with fluoroquinolone monotherapy (moxifloxacin, levofloxacin, or ciprofloxacin) as first-line for peripheral, small lesions, and fortified antibiotics (vancomycin + ceftazidime or cefazolin + tobramycin) for central, large (>2 mm), or severe cases with deep stromal involvement. 1

Initial Assessment and Risk Stratification

Determine severity immediately to guide treatment intensity:

• Severe/sight-threatening features requiring aggressive therapy include: central location, infiltrate >2 mm, deep stromal involvement or melting, hypopyon, multiple infiltrates, or history of corneal surgery 1, 2
• Document baseline visual acuity despite patient discomfort, examine for corneal infiltrates, epithelial defects (using fluorescein staining), stromal involvement, and anterior chamber inflammation 2
• Identify contact lens wear history as this dramatically increases risk of Pseudomonas infection and mandates immediate lens discontinuation 1, 2

Culture and Microbiological Testing

Obtain corneal scrapings for smears and cultures BEFORE starting antibiotics in the following circumstances 1, 2:

• Central, large (>2 mm) infiltrate with significant stromal involvement or melting
• Chronic infection or failure to respond to broad-spectrum antibiotics within 48 hours
• History of corneal surgery
• Atypical features suggesting fungal, amoebic, or mycobacterial etiology
• Multiple corneal infiltrates

Perform Gram stain and Giemsa stain for immediate guidance on empiric therapy selection 2

Antibiotic Selection and Dosing

For Small, Peripheral Bacterial Keratitis

Fluoroquinolone monotherapy is as effective as combination therapy 1, 2, 3:

• Moxifloxacin demonstrates superior healing time (6.8 days faster than ciprofloxacin) and ranks highest among fluoroquinolones 3
• Levofloxacin 1.5% or ofloxacin 0.3% are FDA-approved alternatives with proven efficacy 1
• Standard dosing: every 1-2 hours initially, then reduce to 6-8 times daily after clinical improvement 1, 2

For Central, Large, or Severe Keratitis

Fortified combination antibiotic therapy is superior 1, 2, 3:

• Vancomycin + ceftazidime ranks as most effective (heals 6.2 days faster than ciprofloxacin) with lowest adverse event profile 3
• Cefazolin + tobramycin is alternative fortified combination (heals 5.6 days faster than ciprofloxacin) 3
• Loading dose protocol: every 5-15 minutes for first hour, then hourly application around the clock 1, 2

Critical Resistance Patterns

Be aware of increasing fluoroquinolone resistance 1:

• Methicillin-resistant Staphylococcus aureus (MRSA) shows >30% fluoroquinolone resistance 4
• Pseudomonas aeruginosa demonstrates high multidrug resistance rates with poor prognosis 4
• Recent fluoroquinolone use, hospitalization, and recent ocular surgery increase resistance risk 1

Adjunctive Therapies

Cycloplegic Agents

Use cycloplegic drops when substantial anterior chamber inflammation is present to decrease pain and prevent synechiae formation 1, 2

Corticosteroids

Consider corticosteroids only after 24-48 hours once organism is identified and infection is responding to therapy 1:

• Absolutely avoid in Acanthamoeba, Nocardia, and fungal infections 1
• May benefit central, deep, or large ulcers with low baseline vision when started early after antibiotics 5
• Reduce or eliminate if infection is not controlled 2

Fungal Keratitis

For suspected fungal keratitis, initiate topical natamycin 5% 6, 5, 7:

• Hourly or two-hourly dosing initially for 3-4 days 6
• Reduce to 6-8 times daily after initial period 6
• Continue for 14-21 days until resolution of active infection 6
• Natamycin is superior to voriconazole, particularly for Fusarium species 5
• Oral voriconazole is not recommended due to lack of benefit and increased adverse events 5

Monitoring and Follow-up

Daily follow-up is mandatory until clinical improvement is documented for severe infections 2:

• Signs of clinical response include: reduced pain and discharge, decreased eyelid edema and conjunctival injection, consolidation and sharper demarcation of infiltrate, decreased infiltrate density, reduced anterior chamber inflammation, initial re-epithelialization, and cessation of progressive thinning 2
• Lack of improvement within 48 hours mandates therapy modification and consideration of culture-guided adjustments 2

Special Situations

Contact Lens-Related Keratitis

Immediately discontinue all contact lens wear 1, 2:

• Never patch the eye in contact lens wearers due to increased bacterial keratitis risk 1, 8
• Bandage contact lens use remains controversial and should be avoided until infection is controlled 1
• Prescribe topical antibiotics for contact lens-related corneal abrasions to prevent progression to keratitis 1

Treatment-Resistant Cases

For keratitis refractory to medical therapy 2:

• Consider corneal cross-linking to prevent melting, especially for anterior infections 2
• Evaluate for persistent predisposing factors (ocular surface disease, tear deficiency, lagophthalmos) 2
• Reassess for atypical organisms (fungal, amoebic, mycobacterial) requiring alternative therapy 1

Complications Requiring Surgical Intervention

Hospitalization may be necessary if keratitis is severe, vision-threatening, compliance is unlikely, or pain is severe 2

Surgical options for complications 2:

• Tissue adhesive with bandage contact lens for small perforations
• Tenon's patch graft with cyanoacrylate glue for larger perforations
• Amniotic membrane transplantation to decrease inflammation
• Tectonic keratoplasty for frank perforation

Critical Pitfalls to Avoid

• Do not delay treatment waiting for culture results in sight-threatening cases—begin empiric therapy immediately 1, 2
• Do not use corticosteroids prematurely (before 24-48 hours) or in fungal/amoebic infections 1
• Do not patch eyes in contact lens wearers or use bandage lenses during active infection 1, 8
• Do not assume fluoroquinolone susceptibility in severe cases—fortified antibiotics provide broader coverage against resistant organisms 1, 3, 4
• Do not overlook non-bacterial etiologies if atypical features present or no response to antibiotics within 48 hours 1, 2