Management of Keratitis
Bacterial keratitis requires immediate initiation of intensive topical fluoroquinolone monotherapy (every 1 hour initially) for most cases, with fortified antibiotics reserved for large, central, or severe ulcers with hypopyon. 1
Immediate Treatment Approach
For Bacterial Keratitis
Initial antibiotic selection:
- Small, non-central ulcers: Topical fluoroquinolone monotherapy (ciprofloxacin 0.3%, ofloxacin 0.3%, or levofloxacin 1.5%) is equally effective as combination therapy 1, 2
- Large (>2mm), central, or severe ulcers with deep stromal involvement or hypopyon: Consider fortified antibiotics with loading doses every 5-15 minutes, then hourly 1
- Add cycloplegic agents to reduce pain and prevent synechiae formation 1
Critical timing: Tissue loss can occur within 24 hours with virulent organisms (Pseudomonas, Streptococcus pneumoniae, Neisseria gonorrhoeae), making prompt recognition and treatment essential 1
For Fungal Keratitis
Topical natamycin 5% is the first-line treatment for filamentous fungal keratitis and has demonstrated superior outcomes compared to voriconazole, particularly for Fusarium infections 2, 3, 4. For severe cases, combine with systemic antifungals (voriconazole, ketoconazole, or amphotericin B) 4. Amphotericin B should be considered first-line for yeast infections 5.
For Viral Keratitis (HSV/VZV)
Antivirals are indicated based on the corneal layer involved, with topical corticosteroids added for stromal keratitis after epithelial healing 2, 6. Oral acyclovir reduces recurrence by approximately 50% 2.
For Acanthamoeba Keratitis
Initiate polyhexamethylene biguanide (PHMB) or chlorhexidine immediately 6, 7. Look for characteristic radial keratoneuritis and severe pain disproportionate to clinical findings 1.
Corticosteroid Use: Critical Decision Points
Add topical corticosteroids only after 2-3 days of documented improvement on antibiotics, once the pathogen is identified and fungal infection is ruled out 1. The Steroids for Corneal Ulcers Trial demonstrated 1-line better visual acuity at 3 months when corticosteroids were added within 2-3 days (versus after 4+ days) 1.
Corticosteroids are beneficial for:
- Central, deep, or large ulcers
- Non-Nocardia infections
- Patients with low baseline vision
- Classical invasive Pseudomonas aeruginosa 2
Absolute contraindications:
- Active fungal keratitis (increases risk of perforation requiring keratoplasty) 1
- Nocardia infections 1
- Before epithelial healing begins 1
Monitor IOP within 1-2 days of starting corticosteroids and use the minimum dose needed to control inflammation 1.
Modification of Therapy
Reassess at 48 hours: If no improvement or stabilization occurs, modify the regimen based on culture results and clinical response 1. The therapeutic efficacy is judged primarily by clinical response, not solely laboratory sensitivity testing 1.
Diagnostic Essentials
Before initiating treatment, obtain:
- Corneal scraping for culture (preferred initial test) 6
- Consider PCR for difficult-to-culture organisms or atypical presentations 6, 5
- In vivo confocal microscopy helps diagnose fungal and Acanthamoeba keratitis 2, 6
Key Risk Factors to Address
Contact lens-related (most common):
- Overnight wear
- Swimming/showering with lenses
- Tap water exposure
- Poor hygiene 1
Ocular surface disease:
- Dry eye, epithelial defects
- Previous surgery (cataract, refractive, keratoplasty)
- Trauma or foreign bodies 1
Systemic factors:
- Diabetes mellitus
- Immunosuppression
- Critical illness 1
Critical Pitfalls to Avoid
- Never patch eyes or use therapeutic contact lenses in contact lens-associated abrasions due to increased infection risk 1
- Do not reduce corticosteroids in patients already on them at presentation until infection is controlled - temporary symptom increase is expected and does not indicate worsening infection 1
- Avoid chronic prophylactic antibiotics as they promote resistant organisms without proven efficacy 1
- Do not delay treatment for culture results - begin empiric therapy immediately while awaiting identification 1
Treatment Goals
Prioritize eradicating organisms, minimizing corneal scarring, healing epithelial defects, and optimizing visual function while preventing perforation, endophthalmitis, and eye loss 1. Untreated or severe keratitis can progress to perforation and endophthalmitis, potentially resulting in loss of the eye 1.