A 6-year-old boy with acute ethmoiditis develops marked eyelid swelling, chemosis, lateral and downward displacement of the globe, restricted ocular motility and falling visual acuity. Contrast CT shows a lens-shaped collection along the lamina papyracea displacing the medial rectus. According to Chandler's classification, this represents:

• A Stage II: orbital cellulitis
• B Stage III: subperiosteal abscess ✓
• C Stage IV: orbital abscess
• D Stage I: inflammatory oedema

Explanation

Chandler's five stages are: stage I, preseptal inflammatory oedema; stage II, orbital cellulitis with diffuse infiltration but no discrete collection; stage III, subperiosteal abscess between the lamina papyracea and periorbita, classically displacing the globe laterally, downwards and forwards; stage IV, intraorbital abscess within the orbital fat; stage V, cavernous sinus thrombosis. The lens-shaped collection elevating the periorbita off the lamina papyracea defines a subperiosteal abscess. An orbital abscess instead sits within the extraconal or intraconal fat and does not conform to the bone.

Reference: Dhingra's Diseases of Ear, Nose and Throat, 8th ed.

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Written and medically reviewed by the StethoPrep medical team.