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
Muscle not paralysed in retrobulbar block 
Select and explain. 
A. Superior oblique, B. Lateral rectus, C. Superior rectus, D. Medial rectus
A: Superior oblique
Answer: A: Superior oblique 
Explanation: Answer- A. Superior obliqueA retrobulbar block is a regional anaesthesic nerve block in the retrobulbar space, the area located behind the globe ofthe eye. Injection oflocal anaesthesic into this space constitutes the retrobulbar block.Cranial nerve IV lies outside the muscle cone,but is blocked by diffusion of the local anaesthetic.Superior oblique is supplied by cranial nerve IV.