A 6-year-old boy with acute ethmoiditis develops eyelid swelling, chemosis, proptosis and painful restriction of ocular movements. Contrast CT shows a well-defined lens-shaped fluid collection along the lamina papyracea displacing the medial rectus laterally. According to the Chandler classification, this is:

• A Stage II, orbital cellulitis
• B Stage III, subperiosteal abscess ✓
• C Stage IV, orbital abscess
• D Stage V, cavernous sinus thrombosis

Explanation

Chandler stages are: I preseptal (inflammatory oedema), II orbital cellulitis (diffuse fat infiltration, no collection), III subperiosteal abscess (lens-shaped collection between bone and periorbita, classically along the lamina papyracea), IV orbital abscess (collection within orbital fat), and V cavernous sinus thrombosis. The discrete extraconal collection displacing the medial rectus defines stage III. Stage II lacks a drainable collection, and stage IV implies pus within the orbit itself rather than against the bony wall.

Reference: Scott-Brown's Essential Otorhinolaryngology, 3rd ed.

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Written and medically reviewed by the StethoPrep medical team.