In the Chandler classification of orbital infections, a collection of pus between the orbital bone and periorbita corresponds to which stage?

• A Stage III: subperiosteal abscess ✓
• B Stage II: orbital cellulitis
• C Stage I: preseptal cellulitis
• D Stage V: cavernous sinus thrombosis

Explanation

The Chandler classification has five stages: I preseptal cellulitis, II orbital cellulitis, III subperiosteal abscess (pus between bone and periorbita), IV orbital abscess (pus within the orbit proper), and V cavernous sinus thrombosis. Stage III is distinguished from Stage IV anatomically, not by severity alone, and this distinction guides surgical drainage decisions. Cavernous sinus thrombosis carries bilateral signs and high mortality.

Reference: Parsons' Diseases of the Eye, 23rd ed.

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