Orbital vs Preseptal Cellulitis

Background

The orbital septum divides the anterior (preseptal) and posterior (orbital) Infections.
Preseptal cellulitis: Infection confined anterior to the septum
Orbital cellulitis: infection extends posterior to the septum
Common risk factors/etiologies: URI, acute or chronic sinusitis, trauma, tooth abscess, stye or other local/adjacent skin infection or condition, local or adjacent bug bite, immunocompromised state, underlying systemic infection
Common causes: bacterial (Staph, Strep, Peptococcus, Bacteroides); Fungal (Aspergillus, Mucor) in immunocompromised or diabetic patients.

Feature	Preseptal Cellulitis	Orbital Cellulitis
Appearance	less toxic	more toxic
Vision	No compromise	May be compromised
Eye movements	No/minimal restriction	Painful, restricted, +/- diplopia
Proptosis	No/minimal	Can be present
Conjunctival injection	Mild	Severe
Conjunctival chemosis	None to mild	Severe
Response to PO antibiotics	Improve	Fails to improve

Symptoms that can be present In either: Erythema and Edema of eyelids (upper and/or lower) and periorbital skin; Fever (although more likely in Orbital cellulitis); Difficulty opening the eye d/t swelling; Blurry vision; Tearing/ocular discharge

Vital signs, CBC, CMP, ESR, CRP, blood cultures, wound culture if any open draining areas
CT orbits with and without contrast
track progression with daily photos
LRINEC scale can be used to help assess whether the infection is necrotizing:
https://www.mdcalc.com/lrinec-score-necrotizing-soft-tissue-infection

Preseptal cellulitis: Treat outpatient with PO antibiotics (e.g., Augmentin). Follow closely.
If failure to improve or concern for orbital cellulitis:
Start IV antibiotics (e.g., vancomycin + Unasyn to start if no intracranial extension; could also do vancomycin + ceftriaxone + flagyl).
Consult ophthalmology, ENT (If concomitant sinusitis), OMFS (if odontogenic etiology suspected), and/or ID as needed.
Adjuncts: Tobradex eye drops QID In affected eye, nasal toilet (afrin, flonase, nasal saline per ENT), warm compresses QID to affected eye, trend daily CRP.
If abscess, necrotizing infection, or visual compromise: Surgical drainage is necessary.