This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Ophthalmology
[{'content': 'A person has inability to look downward and laterally. The nerve injured is: September 2012 \nSelect and explain. \nA. Occulomotor, B. Trochlear, C. Abducent, D. Trigeminal', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Ans. B i.e. Trochlear Cranial nerves related to ophthalmology 3rd cranial nerve: - Supplies all extra-ocular muscle EXCEPT superior oblique & lateral rectus, Complete paralysis results in external ophthalmoplegia (Inability to move the eye upward, inward & downward), - Drooping of the upper eyelids due to paralysis of levator palpabrae superioris (ptosis), - Pupillary sparing is a feature of DM 4th cranial nerve: - Weakness/ paralysis of superior oblique muscle; - Which normally moves the eye downwards & inwards 6th cranial nerve: - Weakness/paralysis of lateral rectus; - Which normally rotates the eye laterally', 'role': 'assistant'}]