Orbital and Periorbital Cellulitis
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Direct answer
Orbital cellulitis is infection of the tissues behind the orbital septum, usually spreading from the ethmoid sinuses, whereas periorbital (preseptal) cellulitis lies in front of the septum. Proptosis, ophthalmoplegia, pain on eye movement, chemosis and reduced vision mark orbital involvement and need urgent contrast CT and IV antibiotics. Preseptal disease without these features is usually treated with oral antibiotics.
What you must remember
- Preseptal cellulitis: infection in front of the septum, with eyelid swelling and redness but normal eye movement, vision and globe position.
- Orbital cellulitis: infection behind the septum, with proptosis, ophthalmoplegia, pain on eye movement, chemosis and reduced visual acuity.
- Chandler classification: Group I is preseptal, Group II orbital cellulitis, Group III subperiosteal abscess, Group IV orbital abscess and Group V cavernous sinus thrombosis.
- Source: ethmoid sinusitis is the commonest source, with dental infection, facial trauma and upper respiratory infection as other routes.
- Organisms: Staphylococcus aureus, Streptococcus pneumoniae, Haemophilus influenzae and streptococci, with anaerobes in sinus-related disease.
- Imaging: contrast-enhanced CT of the orbits and sinuses is the investigation of choice for suspected orbital disease.
- Treatment: IV antibiotics covering staphylococci and streptococci, with surgical drainage for subperiosteal or orbital abscess and step-down to oral therapy once improving.
A stepwise approach to a child with a swollen, red eye
A 5-year-old with fever and a red, swollen eyelid has had a blocked nose for a week. The assessment order matters, because the eye can look normal behind a swollen lid.
- Test eye movement and vision. Check ocular movements, visual acuity, pupils and pain on movement, since any restriction moves the child towards orbital disease.
- Look for proptosis. Assess the globe from above and in front, because proptosis suggests a process behind the septum.
- Image urgently. Contrast CT of the orbits and sinuses defines subperiosteal or orbital abscess and identifies the sinus source.
- Start IV antibiotics. Cover Staphylococcus aureus and streptococci, and involve ENT and ophthalmology early.
- Refer for drainage. A subperiosteal or orbital abscess needs surgical drainage, and falling vision is an indication for urgent surgery.
- Step down. Once improving, switch to oral antibiotics guided by culture and the expected duration.
Repeated examination of eye movements and vision every few hours is the safest way to catch change early. A child who deteriorates needs urgent escalation to the surgical team, even while CT is still pending.
Where the exam tries to catch you
Three errors recur on this topic.
- Trap: treating a febrile swollen eyelid as preseptal and giving oral antibiotics alone Correct: ophthalmoplegia, proptosis, pain on eye movement or reduced vision mean orbital involvement needing IV antibiotics and CT.
- Trap: assuming a normal-looking eye excludes orbital disease when the lid is swollen Correct: the lid can conceal proptosis, so eye movements and vision must be formally tested.
- Trap: delaying CT while waiting for a response to antibiotics Correct: orbital disease can deteriorate quickly, so imaging is ordered early rather than after treatment failure.
Frequently asked questions
What separates preseptal from orbital cellulitis?
Preseptal cellulitis lies in front of the orbital septum and causes eyelid swelling and redness without affecting eye movement or vision. Orbital cellulitis lies behind the septum and produces proptosis, ophthalmoplegia, pain on eye movement or reduced vision.
What does the Chandler classification describe in orbital cellulitis?
The Chandler classification in orbital cellulitis grades disease from preseptal infection through orbital cellulitis and subperiosteal abscess to orbital abscess and cavernous sinus thrombosis. Higher grades are more severe and usually need surgical drainage and intensive treatment.
Why is contrast CT used in orbital cellulitis?
Contrast-enhanced CT in orbital cellulitis shows the extent of disease, any subperiosteal or orbital abscess and the sinus source. It guides surgical drainage and identifies complications early.
Which sinus is the commonest source of orbital cellulitis?
The ethmoid sinus is the commonest source of orbital cellulitis in children, because its thin walls lie close to the orbit. Infection can spread across the lamina papyracea, the thin bone that separates the ethmoid sinus from the orbit.