Question

Nerve supply of the extraocular muscles is constituted by all except

• A. Ophthalmic nerve
• B. Oculomotor nerve
• C. Trochlear nerve
• D. Abducent nerve

Answer 1

The Correct Option is A

Mnemonic-first elimination. The classic eye-movement rule is LR6 (SO4) 3: lateral rectus = CN VI (abducent), superior oblique = CN IV (trochlear), and everything else = CN III (oculomotor). That rule already names three of the four options as genuine motor supply to the extraocular muscles, so the odd one out must be the fourth. The ophthalmic nerve is CN V1, the topmost branch of the trigeminal, and it is purely sensory: it carries afferent input from the cornea, conjunctiva, upper eyelid, forehead and nose, but it never makes a muscle contract. Being sensory, it cannot form part of the motor supply of the extraocular muscles. Hence the all-except answer is the ophthalmic nerve. Reference: BDC, 7e, Vol 3, p 215.