A 30-year-old man develops ptosis, ophthalmoplegia, and anaesthesia in the V1 distribution after penetrating trauma near the orbital apex. Visual acuity is counting fingers in the affected eye with a relative afferent pupillary defect. Which structure involved at this site explains his visual loss?

• A Superior ophthalmic vein compression
• B Optic nerve involvement within the optic canal ✓
• C Maxillary division of the trigeminal nerve
• D Trochlear nerve palsy alone

Explanation

This is an orbital apex syndrome: cranial nerves III, IV, VI, and V1 plus the optic nerve are involved at the superior orbital fissure and optic canal junction. Vision loss with a relative afferent pupillary defect localises the lesion to the orbital apex rather than the superior orbital fissure syndrome, which produces identical ocular motor and sensory findings but spares the optic nerve. That sparing is the discriminating fact.

Reference: Kanski's Clinical Ophthalmology, 9th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.