Orbital versus preseptal (periorbital) cellulitis
Accurate differentiation between preseptal (periorbital) and orbital (post‑septal) cellulitis is essential in the emergency department. Orbital cellulitis is a potentially sight‑ and life‑threatening infection requiring urgent admission, parenteral antibiotics and specialist input.
Preseptal cellulitis is usually limited to the eyelid and may be managed as an outpatient if the patient is well and there are no red flags (NICE NG141, NG79).
Definitions and anatomical basis
- Preseptal (periorbital) cellulitis: infection of the eyelid and periorbital soft tissues anterior to the orbital septum. Orbital contents (extraocular muscles, orbital fat, optic nerve) are not involved.
- Orbital cellulitis: infection of tissues posterior to the orbital septum involving orbital fat, extraocular muscles and potentially the optic nerve and intracranial venous channels.
The orbital septum is the clinical divider. Posterior spread (for example, from ethmoid sinusitis) risks subperiosteal or intraorbital abscess, optic nerve compromise, cavernous sinus thrombosis and intracranial complications.
Epidemiology and aetiology
- Preseptal cellulitis commonly follows eyelid trauma, insect bites, blepharitis or contiguous skin infection. Staphylococcus aureus and streptococci are typical pathogens.
- Orbital cellulitis is more common in children and often follows ethmoid sinusitis, facial trauma, dental infection or postoperative infection. Usual organisms include staphylococci, streptococci and organisms from sinus flora; consider anaerobes with dental/sinus source and MRSA / iGAS where local epidemiology dictates (NICE NG141).