A 25-year-old man was struck in the left orbit by a ball. He reports double vision when looking upward and numbness of his left cheek. Examination shows limitation of left elevation and depression, enophthalmos, and hypoesthesia in the distribution of the infraorbital nerve. The structure MOST likely responsible for his findings is:

• A Superior orbital fissure compression by retrobulbar haemorrhage
• B Entrapment of the inferior rectus within an orbital floor fracture ✓
• C Avulsion of the lateral rectus at its insertion
• D Optic nerve sheath haematoma at the orbital apex

Explanation

B blowout fracture of the orbital floor traps the inferior rectus and inferior oblique, producing vertical diplopia worse on attempted upgaze and downgaze. Fracture involving the infraorbital canal causes cheek hypoesthesia, and volume expansion of the orbit produces enophthalmos. Retrobulbar haemorrhage presents with tense proptosis and visual loss, not enophthalmos, and optic nerve injury reduces vision without restricting elevation.

Reference: Kanski's Clinical Ophthalmology, 10th ed.

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Written and medically reviewed by the StethoPrep medical team.