What is the primary treatment approach for a contact lens wearer with bacterial keratitis?

Treatment for Bacterial Keratitis in Contact Lens Wearers

Topical antibiotic eye drops are the primary treatment for bacterial keratitis in contact lens wearers, with fluoroquinolone monotherapy (particularly moxifloxacin 0.5% or levofloxacin 1.5%) being as effective as fortified combination therapy for most cases. 1

Immediate Management Steps

Contact Lens Discontinuation

• Immediately remove contact lenses and discontinue all wear until complete corneal healing is confirmed. 1
• Discard the current contact lenses and cases entirely—they cannot be reused after infection. 2
• Never patch the eye in contact lens wearers, as this dramatically increases the risk of bacterial keratitis progression. 1

Initial Antibiotic Selection

For small, noncentral ulcers (most community-acquired cases):

• Start fluoroquinolone monotherapy with either moxifloxacin 0.5%, levofloxacin 1.5%, or ciprofloxacin 0.3% (all FDA-approved for bacterial keratitis). 1
• Apply every 1-2 hours while awake initially, then taper based on clinical response. 1
• Recent network meta-analysis shows moxifloxacin has the fastest healing time (6.81 days faster than ciprofloxacin). 3

For central or severe keratitis (deep stromal involvement, infiltrate >2mm, or hypopyon present):

• Use loading doses every 5-15 minutes, followed by hourly applications around the clock. 1
• Consider fortified antibiotic combination therapy: vancomycin 25-50 mg/ml + ceftazidime 50 mg/ml (or tobramycin 14 mg/ml + cefazolin 50 mg/ml). 1
• Network meta-analysis demonstrates vancomycin + ceftazidime has the best healing profile (SUCRA 83.8) and lowest adverse effect rate (SUCRA 93.1). 3

Critical Pathogen Considerations

Pseudomonas aeruginosa Risk

• Pseudomonas aeruginosa is the most common organism in contact lens-associated bacterial keratitis (80% of positive cultures in some series). 4, 5
• This organism requires antipseudomonal coverage—fluoroquinolones (especially ciprofloxacin) or fortified aminoglycosides are essential. 4, 5
• Multidrug-resistant Pseudomonas carries very poor functional and anatomical prognosis. 6

Staphylococcal Species

• Staphylococcus aureus and coagulase-negative staphylococci are the second most common organisms (12% of cases). 4, 5
• These organisms have >30% resistance rates to fluoroquinolones and methicillin, with high multidrug resistance. 6

Adjunctive Therapy

Cycloplegic Agents

• Add cyclopentolate 1% or homatropine 5% three times daily to decrease synechiae formation and reduce pain from anterior segment inflammation. 1

Avoid These Interventions

• Do not use ocular ointments as primary therapy—they lack adequate corneal penetration due to poor solubility. 1
• Ointments may be added at bedtime only in less severe cases as adjunctive therapy. 1
• Never use topical corticosteroids initially, as they delay healing and increase infection risk. 7

When to Escalate Treatment

Indications for Fortified Antibiotics

• Large infiltrates (>2mm) or visually significant location (central cornea). 1
• Presence of hypopyon. 1
• Lack of improvement after 48-72 hours of fluoroquinolone monotherapy. 1

Indications for Systemic Antibiotics

• Scleral extension of infection. 1
• Intraocular extension (endophthalmitis). 1
• Systemic infection (e.g., Neisseria gonorrhoeae). 1

Alternative Delivery Methods (Selected Cases)

• Subconjunctival antibiotic injections if adherence is questionable or delays in obtaining fortified antibiotics occur. 1
• Avoid collagen shields or antibiotic-soaked soft contact lenses due to risk of drug toxicity, corneal hypoxia, and unrecognized displacement. 1

Microbiological Workup

When to Obtain Cultures

• All sight-threatening keratitis cases (central location, multifocal, characterized by melting, or painful) require corneal scraping for smears and culture before starting antibiotics. 6
• Gram stain results guide empirical antibiotic selection while awaiting culture results. 6
• Higher minimum inhibitory concentration to the treating antibiotic correlates with worse outcomes (slower re-epithelialization, more visual acuity loss at 3 months). 1

Antibiotic Susceptibility Patterns

• For sight-threatening and resistant keratitis, request susceptibility testing including imipenem, colistin, and linezolid. 6
• Global resistance data shows bacteria are most sensitive to fluoroquinolones (especially ciprofloxacin) and aminoglycosides (especially gentamicin). 4
• Highest resistance rates occur with penicillins, cephalosporins (especially cefazolin), and chloramphenicol. 4

Follow-Up Protocol

Initial Monitoring

• Reassess within 24 hours of treatment initiation to evaluate response and detect early treatment failure. 7
• Perform slit-lamp biomicroscopy with fluorescein staining at each visit to measure epithelial defect and infiltrate size. 2
• Document visual acuity at every visit. 2

Signs of Treatment Failure (Requiring Culture and Regimen Change)

• No improvement or worsening at 48-72 hours. 2
• Increasing pain, purulent discharge, or expanding infiltrate. 7
• Development of corneal perforation. 1

Common Pitfalls to Avoid

Diagnostic Errors

• Failing to examine the cornea with fluorescein staining can miss keratitis in patients presenting with "conjunctivitis." 2
• Missing Acanthamoeba keratitis in contact lens wearers with moderate-to-severe pain and water exposure history (swimming, showering, hot tubs). 2

Treatment Errors

• Resuming contact lens wear before complete epithelial healing leads to recurrence and chronic complications. 2
• Using chronic prophylactic antibiotics promotes resistant organism growth without established efficacy. 1
• Treating with combination steroid-antibiotic drops initially worsens bacterial keratitis outcomes. 7

Patient Education for Prevention

Contact Lens Hygiene

• Never rinse lenses or cases with tap water, bottled water, or homemade saline—use only sterile commercial solutions. 1, 2
• Replace contact lens cases every 3 months minimum, as they become sources of contamination. 1, 2
• Replace disinfecting solution completely each time—never mix old and new solutions. 1

Water Exposure Risks

• Avoid all water contact while wearing lenses: no swimming, hot tubs, showering, or hair washing with lenses in place. 1, 2
• Even occasional overnight wear increases corneal infection risk fivefold compared to daily wear. 1, 2

Long-Term Recommendations

• Consider switching to daily disposable lenses to reduce infection risk. 2
• Schedule regular ophthalmology examinations to monitor lens fit, ocular health, and reinforce proper care techniques. 1