Which diagnosis distinguishes preseptal cellulitis from orbital cellulitis?

• A. Orbital cellulitis
• B. Preseptal cellulitis
• C. Conjunctivitis
• D. Blepharitis

Answer: (B)

The distinguishing feature is whether the infection involves the orbit behind the orbital septum. Preseptal cellulitis stays anterior to the septum, affecting only the eyelid and surrounding soft tissues, while orbital cellulitis involves the orbit itself. The key clues are signs of orbital involvement: pain with eye movements, restricted or painful extraocular movements, proptosis, and any decrease in visual acuity. If these are present, the diagnosis points to orbital cellulitis; if they are absent and only eyelid swelling is seen, it’s preseptal cellulitis. Conjunctivitis or blepharitis can cause redness or lid irritation but do not produce the orbital signs that distinguish a true orbital involvement.