Orbital Cellulitis
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Direct answer
Orbital cellulitis is infection of the soft tissues behind the orbital septum — proptosis, painful restriction of eye movements, chemosis, swollen lids and fever, often with reduced vision — nearly always spreading from the ethmoid and other paranasal sinuses in children and young adults. It is distinguished from preseptal cellulitis, which affects only the lid tissues anterior to the septum and produces swelling without proptosis, ophthalmoplegia or visual loss. The Chandler classification grades the spectrum from I (preseptal) through II (orbital cellulitis) and III (subperiosteal abscess) to IV (orbital abscess) and V (cavernous sinus thrombosis), the last two threatening both sight and life. Management is contrast-enhanced CT of the orbits and sinuses, blood cultures, intravenous antibiotics, and ENT-surgical drainage of abscesses or unresolved disease; in Indian practice, diabetic and immunocompromised patients warrant suspicion of fungal disease — mucormycosis — which became epidemic after COVID-19.
What you must remember
- The septum is the dividing line: preseptal cellulitis — lid oedema and erythema with normal vision, full motility and no proptosis; orbital cellulitis — proptosis, painful ophthalmoplegia, chemosis, possible RAPD and visual loss, usually sinusogenic.
- Chandler classification (five stages): I preseptal cellulitis; II orbital cellulitis; III subperiosteal abscess (between periorbita and orbital wall, often medial from the ethmoid); IV orbital abscess; V cavernous sinus thrombosis.
- Source and organisms: ethmoid sinusitis dominates because the paper-thin lamina papyracea separates the ethmoids from the orbit; organisms are streptococci (pneumoniae, pyogenes), Staphylococcus aureus, and Haemophilus influenzae type b in the unvaccinated under-five; mixed anaerobes in chronic sinus and dental sources.
- Danger signs demanding escalation: dropping vision or a new RAPD (optic nerve compromise), severe proptosis with corneal exposure, bilateral lid oedema (cavernous sinus thrombosis until disproved), meningism or altered sensorium, and a frozen globe.
- Investigation: contrast-enhanced CT of orbits and sinuses, blood cultures before antibiotics where feasible, and visual acuity with pupils at least daily — vision is the vital sign of the orbit.
- Treatment: admission and intravenous antibiotics (ceftriaxone with metronidazole, or co-amoxiclav with vancomycin where severity dictates) with oral continuation; surgical drainage with ENT — endoscopic sinus surgery — for abscess stages, non-response despite 24-48 hours, or optic nerve compromise.
- The fungal caveat for Indian settings: rhino-orbital mucormycosis in diabetic ketoacidosis, immunosuppression or post-COVID steroid use presents with pain, ophthalmoplegia and black nasal crusts; treatment is urgent debridement with liposomal amphotericin B, and mortality is high when diagnosed late — India's 2021 epidemic made this a household word.
- The danger triangle: facial and orbital infections drain via valveless angular and ophthalmic veins to the cavernous sinus — facial sepsis here is never trivial.
How to work through a swollen eye in a child
An 8-year-old boy is brought with two days of lid swelling after a "cold", now with fever 39 degrees, painful diplopia and an eye that will not abduct. Triage: swollen lid plus proptosis plus painful restricted movement plus fever crosses the septum — orbital cellulitis, Chandler stage II at least. Baseline vision and pupils are charted (6/18, no RAPD), CT with contrast shows right ethmoid opacification with a medial subperiosteal collection — stage III — and intravenous ceftriaxone with metronidazole starts after cultures. The collection is modest and vision stable, so he is monitored for 24-48 hours; no improvement, rising proptosis or visual decline takes him to combined endoscopic sinus and abscess drainage with ENT. Contrast his diabetic grandfather after COVID with anaesthetic facial swelling, ophthalmoplegia and a black middle turbinate: mucormycosis — biopsy, aggressive debridement and liposomal amphotericin with glycaemic correction, with no delay for antibiotic trials. Same anatomy, opposite drugs: the bacterial child recovers; the fungal adult dies of delay.
Where students slip
The preseptal-versus-postseptal question is answered wrongly by treating the septum as a radiological curiosity: proptosis, ophthalmoplegia, pain on movement and visual change are the signs that infection is orbital, and a child whose eye cannot be examined beneath swollen lids cannot be safely labelled preseptal — imaging resolves it. The opposite error admits every mild preseptal case for scans: with a clearly examinable, normally moving eye, oral antibiotics and review suffice. Third, vision checks drive management — a declining acuity or new RAPD converts medical management into surgical drainage regardless of imaging.
Frequently asked questions
How is orbital cellulitis differentiated from preseptal cellulitis?
Orbital cellulitis lies posterior to the orbital septum, with proptosis, painful restricted movements, chemosis and possible visual loss; preseptal cellulitis affects the lids only, with normal vision, motility and globe position.
What is the Chandler classification?
A five-stage grading: I preseptal cellulitis, II orbital cellulitis, III subperiosteal abscess, IV orbital abscess, V cavernous sinus thrombosis — increasingly severe extensions of sinusogenic infection.
Which sinus most commonly seeds orbital cellulitis and why?
The ethmoid, whose paper-thin lamina papyracea allows infection to spread directly into the orbit, particularly in children.
When does orbital cellulitis need surgical intervention?
For abscess stages on imaging, deterioration or failure to improve within 24-48 hours, or optic nerve compromise — jointly with ENT, usually endoscopically.
Why suspect mucormycosis in a diabetic patient with orbital cellulitis?
Rhino-orbital mucormycosis presents with rapidly progressive ophthalmoplegia, facial anaesthesia and necrotic nasal crusts in ketoacidosis or post-steroid states; it needs urgent debridement and amphotericin, not antibiotics alone.