Orbital Cellulitis

Orbital cellulitis is infection involving the soft tissues of the orbit posterior to the orbital septum — distinct from preseptal (periorbital) cellulitis, limited to tissues anterior to the septum with a far more benign course. Orbital cellulitis is uncommon but carries real potential for significant morbidity, including vision loss and intracranial spread.¹ Orbital complications of sinusitis are staged using the Chandler classification: preseptal cellulitis, orbital cellulitis (diffuse infection without a discrete collection), subperiosteal abscess, orbital (intraconal) abscess, and cavernous sinus thrombosis.

Orbital cellulitis is typically caused by contiguous spread from the paranasal sinuses (especially ethmoid sinusitis), though it can also result from local trauma, dental infection, or hematogenous spread.¹ It is more common in children than adults, though adult cases tend to be more severe.¹² Among complications of acute rhinosinusitis, orbital involvement is the most frequent site of spread, accounting for roughly 60-75% of rhinosinusitis complications in one series.² Infection most commonly spreads through the thin, porous lamina papyracea or via valveless orbital venous communications. Once within the orbit, infection can remain diffuse or progress to a subperiosteal or true orbital (intraconal) abscess, and, if unchecked, extend posteriorly toward the cavernous sinus or intracranially.

Patients present with periorbital swelling, erythema, and pain, often with concurrent sinusitis symptoms. Proptosis, restricted or painful extraocular movements, and decreased visual acuity distinguish true orbital (septal) involvement from preseptal disease.

Key differentials: preseptal cellulitis (the key first distinction, far more common and less urgent), orbital inflammatory disease or thyroid eye disease (can mimic proptosis and restricted motility without infectious features), ruptured dermoid cyst with secondary inflammation, rhabdomyosarcoma or other orbital malignancy (rapidly progressive proptosis mimicking infection in a child), and cavernous sinus thrombosis as a complication to specifically identify or exclude.

Key findings raising concern for orbital involvement include proptosis or globe displacement, restricted/painful extraocular movements, decreased acuity or an afferent pupillary defect, chemosis, and resistance to retropulsion or elevated IOP suggesting orbital compartment syndrome — a true emergency requiring immediate decompression. Complete inability to open the eyelid has been associated with greater likelihood of needing surgery in a pediatric cohort.³ Contrast-enhanced CT of the brain and orbits is critical for detecting abscess or intracranial extension; MRI should follow if suspicion remains high despite non-diagnostic CT. Point-of-care ultrasound can help distinguish preseptal from orbital cellulitis at the bedside but cannot reliably exclude intracranial extension, so it does not replace CT/MRI.¹

Emergency clinicians should first assess for orbital compartment syndrome before proceeding with the rest of the eye exam.¹ Initial management is early broad-spectrum IV antibiotics and prompt ophthalmology consultation; adjunctive corticosteroid use remains controversial rather than settled.¹ Neurosurgery consultation is warranted for any intracranial extension.¹ The decision between medical management and surgical drainage is individualized: in a pediatric cohort with Chandler stage III subperiosteal abscess, roughly half required surgery, with complete eyelid closure, ophthalmoplegia, exophthalmos, elevated CRP (>60 mg/L) or leukocyte count (>15,600/L), retro-septal cellulitis, posterior ethmoid opacification, and abscess width >4mm each independently associated with need for surgery — decision-support factors from that specific population, not universal cutoffs, since many patients in that cohort were managed medically without surgery.³ A separate series similarly found small, medially-located subperiosteal abscesses in young children often responded well to antibiotics alone, while other locations or older patients more often required surgical drainage.²

• The preseptal-versus-orbital distinction is the single most important early triage decision, changing the entire management pathway
• Point-of-care ultrasound is useful for the preseptal-versus-orbital distinction but cannot exclude intracranial spread¹
• Complete eyelid closure, exophthalmos, ophthalmoplegia, elevated inflammatory markers, and larger abscess width were each independently associated with need for surgical drainage in one pediatric cohort³
• Many small, medially-located subperiosteal abscesses in young children can be managed successfully with antibiotics alone²
• Common pitfall: treating preseptal and orbital cellulitis interchangeably
• Common pitfall: relying on POCUS alone to exclude intracranial extension of infection¹
• Common pitfall: missing orbital compartment syndrome by not specifically assessing for resistance to retropulsion or a taut, tense orbit