What first‑line topical antibiotic is recommended for treating a corneal abrasion in an adult with no known drug allergies?

First-Line Topical Antibiotic for Corneal Abrasion

For an adult with corneal abrasion and no drug allergies, prescribe a fourth-generation fluoroquinolone—specifically moxifloxacin 0.5% or gatifloxacin 0.5%—applied four times daily, initiated within 24 hours of injury to prevent bacterial keratitis. 1, 2

Why Fluoroquinolones Are First-Line

• The American Academy of Ophthalmology recommends fluoroquinolones as the preferred topical antibiotics due to their broad-spectrum coverage against both gram-positive organisms (including methicillin-resistant Staphylococcus aureus) and gram-negative organisms (including Pseudomonas), which is critical when the injury source may be contaminated. 1

• Fourth-generation agents (moxifloxacin, gatifloxacin) provide superior gram-positive coverage compared to older fluoroquinolones like ciprofloxacin, and they are FDA-approved for bacterial keratitis treatment. 1, 2

• Fluoroquinolone drops achieve higher corneal tissue concentrations than ointments, making them the preferred formulation over tetracycline or other ointment-based antibiotics. 2

Specific Dosing Regimen

• Moxifloxacin 0.5%: one drop four times daily until complete epithelial healing is confirmed (typically 3–5 days). 1, 2

• Alternative: levofloxacin 1.5% four times daily provides equivalent efficacy with higher concentration and is also FDA-approved for bacterial keratitis. 2

• Initiate treatment within 24 hours of injury for maximum prophylactic benefit—this timing window has been shown to prevent ulceration in high-quality studies. 1, 2, 3

Risk-Based Adjustments

• Contact lens wearers require mandatory antipseudomonal coverage with fluoroquinolones because Pseudomonas aeruginosa is the predominant pathogen in this population. 1, 2

• For non–contact lens wearers with simple abrasions from known clean trauma, fluoroquinolones remain first-line due to their broad spectrum, though the absolute infection risk is lower. 4

• Unknown or contaminated sources (vegetable matter, dirty objects, soil) warrant fluoroquinolones to cover polymicrobial and atypical organisms. 1

Role of Tetracycline Ointment (Not First-Line)

• Tetracycline ointment lacks adequate corneal penetration and should not be used as monotherapy for corneal abrasion prophylaxis. 2

• Tetracycline may be added at bedtime as adjunctive therapy to fluoroquinolone drops in less severe cases, but drops remain the primary treatment. 2

What NOT to Do

• Never patch the eye—patching does not improve pain, delays healing, and increases bacterial keratitis risk, especially in contact lens wearers. 1, 2, 4, 5

• Do not use combination steroid-antibiotic drops as initial therapy—steroids delay healing, mask infection signs, and worsen outcomes in fungal or Acanthamoeba keratitis. 2

• Avoid therapeutic contact lenses in the acute phase of contact lens–related abrasions due to elevated secondary bacterial keratitis risk. 1, 2

• Do not prescribe chronic prophylactic antibiotics beyond 3–5 days—prolonged use promotes resistant organisms without additional benefit once epithelial healing is complete. 1, 2

Pain Management Algorithm

• Prescribe oral NSAIDs (ibuprofen) or acetaminophen for pain control rather than topical anesthetics, which delay healing. 1, 5

• Consider a cycloplegic agent (cyclopentolate or homatropine) only if substantial anterior chamber inflammation or ciliary spasm is present—evidence does not support routine cycloplegic use for uncomplicated abrasions. 1, 5

Red Flags Requiring Immediate Ophthalmology Referral

• Central infiltrate >2 mm, hypopyon (layered white cells in anterior chamber), or significant stromal involvement signals severe infection requiring cultures, fortified antibiotics (cefazolin/tobramycin), and hourly dosing. 1, 2

• Increasing pain after initial improvement, purulent discharge, vision loss, or irregular pupil may indicate bacterial keratitis or penetrating injury. 1, 4

• Contact lens wearer with any infiltrate or delayed healing warrants same-day ophthalmology evaluation due to high Pseudomonas risk. 1, 2

Follow-Up Timing

• Small abrasions (≤4 mm) with normal vision and resolving symptoms may not require routine follow-up if the patient is reliable and understands warning signs. 5

• All other patients should be reevaluated in 24 hours to confirm epithelial healing and rule out early infection. 1, 5

• Patients must return immediately if symptoms worsen rather than waiting for scheduled follow-up. 1, 4

Evidence Quality and Guideline Strength

• The American Academy of Ophthalmology provides strong guideline recommendations for fluoroquinolone prophylaxis based on the potentially severe consequences of untreated bacterial keratitis, despite low-certainty trial evidence regarding magnitude of benefit. 2

• A 2022 Cochrane review found very low certainty evidence that antibiotic prophylaxis prevents infection or accelerates healing, but the review included only two small trials and did not assess fluoroquinolones specifically. 6

• A 2001 Nepalese study demonstrated that chloramphenicol ointment started within 18 hours prevented ulceration in 100% of cases, providing high-quality evidence for the 24-hour treatment window principle. 3

• Despite research uncertainty, clinical guidelines prioritize fluoroquinolones because the low risk of short-term topical therapy is outweighed by the catastrophic morbidity of bacterial keratitis (corneal scarring, vision loss). 2

Common Pitfalls to Avoid

• Missing contact lens history increases Pseudomonas risk—specifically ask about lens wear, overnight wear, swimming/hot tub use with lenses, and contaminated storage cases. 1, 2

• Assuming all abrasions are benign—unknown sources may harbor atypical organisms requiring cultures if not improving by 48 hours. 1

• Inadequate blinking or incomplete eyelid closure delays healing—assess lid function and consider temporary tarsorrhaphy with botulinum toxin or suture if closure is inadequate. 4