Treatment of Eye Cellulitis
Critical Distinction: Preseptal vs. Orbital Cellulitis
Eye cellulitis requires immediate differentiation between preseptal cellulitis (infection of eyelid tissues anterior to the orbital septum) and orbital cellulitis (infection posterior to the orbital septum involving orbital contents), as orbital involvement demands aggressive intervention with imaging and potential surgical management, while preseptal cellulitis in healthy adults can be managed conservatively with oral antibiotics. 1
When Orbital Involvement is Present or Suspected
- Obtain orbital imaging immediately (CT or MRI) if there is proptosis, ophthalmoplegia, vision changes, or severe pain, as orbital cellulitis can spread intracranially and cause devastating consequences 1
- Hospitalize and initiate IV antibiotics with broad-spectrum coverage including vancomycin plus piperacillin-tazobactam or a carbapenem for patients with orbital involvement, systemic inflammatory response syndrome (fever, hypotension, altered mental status), or severe disease 2
- Consult ophthalmology urgently for any suspected orbital involvement, as these patients require aggressive management by physicians trained in eye diseases and surgery 1
Preseptal Cellulitis in Adults (No Orbital Involvement)
First-line oral antibiotic therapy targeting Streptococcus pyogenes and methicillin-sensitive Staphylococcus aureus is appropriate for preseptal cellulitis in healthy adults without orbital or optic nerve involvement. 2, 1
Preferred First-Line Agents
- Cephalexin 500 mg every 6 hours orally provides effective coverage against typical pathogens causing periocular cellulitis 2
- Dicloxacillin is equally effective as first-line therapy 2
- Amoxicillin-clavulanate is appropriate when broader coverage is needed, particularly with traumatic wounds or purulent drainage 2
Treatment Duration
- 5 days of therapy is sufficient if clinical improvement occurs, with extension only if infection has not improved 2
- Evidence demonstrates 5-day courses are as effective as 10-day courses for uncomplicated cellulitis 2
When to Add MRSA Coverage
- Do NOT routinely add MRSA coverage for typical periocular cellulitis, as MRSA is an unusual cause 2
- Add MRSA coverage in specific scenarios: penetrating trauma, purulent drainage, known MRSA colonization, evidence of MRSA infection elsewhere, or systemic inflammatory response syndrome 2
- MRSA coverage options include clindamycin 300-450 mg three times daily (covers both streptococci and MRSA) or trimethoprim-sulfamethoxazole plus a β-lactam 2
Penicillin Allergy Considerations
- Clindamycin 300-450 mg orally three times daily is the preferred agent for penicillin-allergic patients, as 99.5% of S. pyogenes strains remain susceptible 2, 3
- For severe infections requiring parenteral therapy in allergic patients, use IV clindamycin 600 mg three times daily 3
Reassessment and Treatment Failure
- Reassess within 24-48 hours to ensure clinical improvement 2
- If no improvement with appropriate first-line antibiotics, immediately add empiric MRSA coverage with trimethoprim-sulfamethoxazole 1-2 DS tablets twice daily, doxycycline 100 mg twice daily, or clindamycin 2
- Consider alternative diagnoses including abscess requiring drainage, deep vein thrombosis, or necrotizing infection if treatment fails 2
- Do not delay switching therapy beyond 48-72 hours of failed treatment, as this increases morbidity 2
Critical Pitfalls to Avoid
- Never dismiss complaints of pain or red eye in post-surgical patients, as endophthalmitis must be ruled out and requires aggressive management by ophthalmology 1
- Do not use trimethoprim-sulfamethoxazole as monotherapy for typical cellulitis, as it lacks adequate streptococcal coverage 2
- Do not assume all periocular infections are simple cellulitis—severe conjunctivitis and any corneal infection require cultures and broad-spectrum antibiotics 1