Antibiotic Management for Cat Scratch Corneal Abrasion
For a cat scratch corneal abrasion, ofloxacin ophthalmic drops alone are sufficient for antibiotic prophylaxis, but erythromycin ointment should NOT be used as it lacks adequate corneal penetration and does not provide appropriate coverage for the high-risk pathogens associated with cat scratches. 1, 2
Critical Pathogen Consideration
Cat scratches carry a specific risk for Pasteurella multocida infection, which can cause severe keratitis and corneal ulceration. 3 This organism requires appropriate fluoroquinolone coverage, which ofloxacin provides, but erythromycin does not adequately cover. 3
Why Erythromycin is Inadequate
- Ocular ointments, including erythromycin and tetracycline, lack solubility and cannot penetrate into the cornea significantly for optimum therapeutic benefit. 1
- Ointments may only be useful at bedtime in less severe cases as adjunctive therapy to antibiotic drops, not as primary or sole therapy. 1
- Topical antibiotic eye drops are the preferred method of treatment for corneal abrasions due to their ability to achieve high tissue levels in the cornea. 1
Recommended Treatment Protocol
Standard Prophylaxis
- Apply ofloxacin 0.3% ophthalmic drops four times daily until complete epithelial healing is confirmed, with treatment initiated within 24 hours of the abrasion. 1
- Prophylactic topical antibiotics following corneal abrasion prevent ulceration when treatment is started within 24 hours. 4, 1, 2
Ofloxacin Efficacy
- Ofloxacin achieves corneal tissue concentrations of 4.4 mcg/mL four hours after topical application, providing adequate antimicrobial coverage. 5
- Ofloxacin has demonstrated clinical success rates of 82% for corneal ulcers and 86% improvement rates for conjunctivitis in controlled trials. 5
- Single-drug therapy using fluoroquinolones like ofloxacin has been shown to be as effective as combination therapy utilizing fortified antibiotics for bacterial keratitis. 2
When to Escalate Treatment
Immediately escalate treatment if any of the following develop:
- Central location or infiltrate >2mm 1
- Deep stromal involvement 1
- Presence of hypopyon 1
- Corneal stromal loss 1
- Increasing pain, purulent discharge, or worsening symptoms 1
Escalation Protocol
- Initiate loading dose every 5-15 minutes, then hourly dosing 1, 2
- Consider fortified antibiotics (tobramycin 1.5% + cefazolin 10%) for severe cases 1, 2
- Fourth-generation fluoroquinolones (moxifloxacin, gatifloxacin) may offer better gram-positive coverage in severe cases 2
Important Caveats
- Do NOT use pressure patching or bandage contact lenses in this patient, as cat scratch abrasions carry increased risk of secondary bacterial keratitis. 4, 6
- Avoid combination steroid-antibiotic drops as initial therapy; steroids should only be added after 2-3 days of antibiotic-only therapy if needed. 1
- Fluoroquinolone resistance is increasing, with risk factors including recent fluoroquinolone use, hospitalization, advanced age, and recent ocular surgery. 2
- Educate the patient about signs of infection (increasing pain, redness, discharge, vision changes) and instruct them to return immediately if symptoms worsen. 1, 6