What is the appropriate first‑line antibiotic eye drop regimen for an adult with a corneal abrasion and no known drug allergies?

First-Line Antibiotic Eye Drop for Corneal Abrasion

For an adult with a simple corneal abrasion and no drug allergies, prescribe a fluoroquinolone eye drop (moxifloxacin 0.5% or levofloxacin 1.5%) four times daily, initiated within 24 hours of injury to prevent bacterial keratitis and ulceration. 1, 2

Standard Treatment Protocol

Antibiotic Selection by Risk Category

Low-Risk Abrasions (non-contact lens related):

• Fluoroquinolone drops remain the preferred first-line choice due to broad-spectrum coverage and superior corneal penetration 2
• Moxifloxacin 0.5% or levofloxacin 1.5% applied four times daily 2, 3
• Treatment duration: Continue until complete epithelial healing is confirmed, typically 3-7 days 2, 3

High-Risk Abrasions (contact lens-related):

• Mandatory antipseudomonal coverage with fluoroquinolones 2
• Contact lens wear dramatically increases risk of Pseudomonas keratitis 2
• Never patch the eye in contact lens wearers—this increases bacterial keratitis risk 1, 2

Critical Timing

• Prophylactic antibiotics must be started within 24 hours of the abrasion to effectively prevent ulceration 1, 2
• This 24-hour window is evidence-based and represents the therapeutic window for maximum benefit 1

Why Fluoroquinolones Over Other Options

Advantages of Fluoroquinolone Drops

• Achieve high corneal tissue levels—the preferred delivery method for corneal abrasions 1, 2
• Broad-spectrum coverage against both gram-positive and gram-negative organisms 1
• Fourth-generation fluoroquinolones (moxifloxacin, gatifloxacin) demonstrate superior gram-positive coverage compared to earlier generations 1
• FDA-approved options include ciprofloxacin 0.3%, ofloxacin 0.3%, and levofloxacin 1.5% for bacterial keratitis 1

Why NOT Ointments as First-Line

• Ocular ointments (including tetracycline or erythromycin) lack adequate corneal penetration due to poor solubility 1, 2
• Ointments may be useful only as adjunctive bedtime therapy in less severe cases, not as monotherapy 1, 2
• Drops are superior for achieving therapeutic antibiotic levels in corneal tissue 1

Specific Dosing Regimen

Standard prophylaxis:

• Moxifloxacin 0.5%: One drop in affected eye 3 times daily for 7 days 3
• Levofloxacin 1.5%: Four times daily until healed 2
• Alternative: Ofloxacin 0.3% four times daily 2

Red Flags Requiring Treatment Escalation

Immediate Ophthalmology Referral Needed If:

• Central infiltrate >2mm diameter 2
• Deep stromal involvement or corneal melting 2
• Presence of hypopyon (layered white cells in anterior chamber) 1, 2
• Corneal infiltrate with suppuration, necrosis, or feathery margins 2
• Contact lens wearer with worsening symptoms despite treatment 2

For severe keratitis: Escalate to loading dose every 5-15 minutes, then hourly dosing, with consideration of fortified antibiotics (tobramycin 1.5% + cefazolin 10%) 2

Critical Management Pitfalls to Avoid

Do NOT:

• Never patch the eye—patching does not improve pain, may delay healing, and increases infection risk especially in contact lens wearers 2, 4
• Never use combination steroid-antibiotic drops initially—steroids mask infection signs and worsen outcomes in fungal/Acanthamoeba infections 2, 5
• Never use therapeutic contact lenses in contact lens-related abrasions—this increases secondary bacterial keratitis risk 1
• Avoid chronic prophylactic antibiotic use beyond the healing period—this promotes resistant organisms 2

Resistance Concerns

• Methicillin-resistant Staphylococcus aureus (MRSA) shows 42% prevalence in ocular isolates with high concurrent fluoroquinolone resistance 1
• Pseudomonas aeruginosa demonstrates increasing fluoroquinolone resistance, particularly in contact lens wearers 2
• Despite resistance concerns, fluoroquinolones remain first-line due to superior tissue penetration and clinical outcomes 1, 2

Evidence Quality Considerations

The 2024 American Academy of Ophthalmology Bacterial Keratitis Preferred Practice Pattern provides the strongest guideline evidence supporting broad-spectrum topical antibiotics for corneal abrasion prophylaxis 1. However, the most recent Cochrane systematic review (2025) found very low certainty evidence regarding antibiotic efficacy in preventing infection or accelerating healing 6. Despite this uncertainty in the research literature, clinical guidelines strongly recommend antibiotic prophylaxis based on the potential severity of untreated bacterial keratitis and the low risk of short-term antibiotic use 1, 2.

Patient Education Points

• Apply drops within 24 hours of injury for maximum benefit 1, 2
• Watch for warning signs: increasing pain, purulent discharge, vision changes, or worsening redness 2
• Avoid contact lens wear until complete healing confirmed by healthcare provider 2
• Do not rub the eye—this worsens injury 2
• Seek immediate care if symptoms worsen despite treatment 2