For a simple corneal abrasion, how many times per day and for how many days should a polymyxin‑based ophthalmic drop be administered?

Polymyxin-Based Ophthalmic Drops for Simple Corneal Abrasion

For simple corneal abrasions, apply polymyxin-based antibiotic drops (typically polymyxin B/trimethoprim or polymyxin B/bacitracin ointment) 3-4 times daily for 3-5 days, with follow-up at 24-48 hours to assess healing. 1

Dosing Frequency

• Administer topical antibiotics 3-4 times daily as the standard prophylactic regimen for uncomplicated corneal abrasions 2, 1
• Do not reduce frequency below 3-4 times daily, as subtherapeutic dosing increases resistance risk 2
• For contact lens-associated abrasions or high-risk trauma cases, consider more frequent initial dosing (every 2-4 hours while awake for the first 24-48 hours) 1

Duration of Treatment

• Continue treatment for 3-5 days or until complete epithelial healing is confirmed 1, 3
• Most simple corneal abrasions heal within 24-72 hours, but antibiotic prophylaxis should continue until re-epithelialization is complete 4
• Discontinue antibiotics once infection risk has passed and healing is confirmed, as prolonged use causes corneal toxicity 2

Clinical Monitoring Algorithm

Day 1 (24 hours post-injury):

• Mandatory follow-up to assess healing progress 3
• Evaluate for signs of infection (increased pain, purulent discharge, infiltrate) 1
• If healing appropriately and no infection signs, continue antibiotics 3-4 times daily 1

Day 3-4:

• Re-evaluate if not fully healed 2, 5
• If no improvement or worsening, obtain cultures and consider resistant organisms or non-bacterial causes 2
• Most abrasions should be healed by this point; delayed healing warrants investigation 6, 4

Formulation Considerations

• Polymyxin B combinations (with trimethoprim or bacitracin) provide adequate gram-negative and some gram-positive coverage for prophylaxis 6, 7
• Ointment formulations may be preferred at bedtime for sustained contact and comfort 6, 7
• Drops during daytime allow better vision and are more convenient for patients 7

Critical Caveats and Pitfalls

High-Risk Scenarios Requiring Modified Approach:

• Contact lens-related abrasions require anti-pseudomonal coverage (fluoroquinolones preferred over polymyxin alone) 1, 8
• Vegetable matter or organic material injuries warrant antifungal coverage in addition to antibiotics 1
• Central or large abrasions (>4mm) may require more aggressive initial dosing 1

Absolute Contraindications to Standard Approach:

• Never patch the eye in contact lens wearers, as this dramatically increases bacterial keratitis risk 2, 1
• Do not use therapeutic contact lenses in contact lens-associated abrasions for the same reason 1

When to Escalate:

• If epithelial defect persists beyond 5-7 days, consider underlying pathology (recurrent erosion syndrome, basement membrane dystrophy, neurotrophic keratopathy) 6
• Any signs of infiltrate, hypopyon, or progressive pain warrant immediate ophthalmology referral and consideration of fortified antibiotics 1

Evidence Quality Note

The evidence for antibiotic prophylaxis in corneal abrasion shows very low certainty regarding infection prevention, with infection rates extremely low in both treated and untreated groups 4. However, the standard of care remains prophylactic antibiotics given the potentially devastating consequences of secondary bacterial keratitis, particularly in high-risk populations 1, 3. The American Academy of Ophthalmology specifically recommends topical antibiotics to prevent acute bacterial keratitis following corneal abrasion, especially in trauma or contact lens wear 1.