Treatment of Eye Scratch from Unknown Source
For a corneal abrasion from an unknown source, prescribe a topical fluoroquinolone antibiotic (moxifloxacin or gatifloxacin) 4 times daily, with consideration for antibiotic ointment at bedtime, and provide oral analgesics for pain control. 1, 2
First-Line Antibiotic Selection
- Fluoroquinolones are the preferred topical antibiotics due to their broad-spectrum coverage against both gram-positive and gram-negative organisms, which is critical when the source is unknown 3, 1, 2
- Moxifloxacin or gatifloxacin drops should be applied 4 times daily 1
- These agents are FDA-approved for bacterial keratitis and provide superior gram-positive coverage compared to older fluoroquinolones like ciprofloxacin 3
- Antibiotic ointment (such as erythromycin or polymyxin B) may be added at bedtime for additional protection and lubrication 1, 4
Critical Consideration: Unknown Source Risk
Since the source is unknown, you must assume higher risk for infection:
- Start antibiotics within 24 hours for maximum prophylactic benefit 1
- Unknown sources could include contaminated objects, vegetable matter (fungal risk), or dirty environments (polymicrobial risk) 3
- The broad-spectrum coverage of fluoroquinolones addresses the most common pathogens: Staphylococcus (including methicillin-resistant strains), Streptococcus, and Pseudomonas 3
Pain Management Algorithm
- Prescribe oral NSAIDs (ibuprofen) or acetaminophen for pain control 1, 5, 4
- Topical NSAIDs (ketorolac 0.5%) can significantly reduce pain, photophobia, and foreign body sensation within 24 hours 4
- Consider a cycloplegic agent (cyclopentolate or homatropine) if substantial anterior chamber inflammation is present to reduce ciliary spasm pain 3, 5
What NOT to Do
- Do not patch the eye - patching does not improve healing and may actually delay it 1, 2, 6
- Avoid topical steroids initially as they delay healing and increase infection risk 1, 2
- Do not use therapeutic contact lenses in the acute phase due to increased bacterial keratitis risk 3, 5
- Instruct the patient not to rub the eye, as this worsens the injury 5, 2
Follow-Up and Warning Signs
Patients must return immediately if they develop:
- Increasing pain after initial improvement 1, 2
- Purulent discharge or corneal infiltrate 1, 2
- Vision loss or irregular pupil 5
- Symptoms persisting beyond 48-72 hours 6
Special Circumstances Requiring Escalation
If the abrasion is central, large (>2mm), or associated with significant stromal involvement, consider:
- More frequent dosing of fluoroquinolones (every 1-2 hours initially) 3
- Fortified antibiotics (cefazolin/tobramycin combination) 3
- Immediate ophthalmology referral 3
Common Pitfalls to Avoid
- Chronic antibiotic use promotes resistant organisms - limit prophylaxis to 3-5 days unless infection develops 1, 2
- Inadequate blinking or incomplete eyelid closure delays healing - assess lid function 2
- Missing contact lens history increases Pseudomonas risk - specifically ask about lens wear 3, 5
- Assuming all abrasions are benign - unknown sources may harbor atypical organisms requiring cultures if not improving by 48 hours 3