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
Optic canal is a pa of ? 
Select and explain. 
A. Lesser wing of sphenoid, B. Greater wing of sphenoid, C. Ethmoid, D. Pterygoid
A: Lesser wing of sphenoid
Answer: A: Lesser wing of sphenoid 
Explanation: Ans. is 'a' i.e., Lesser wing of sphenoid The optic nerve leaves the orbit is the optic canal to enter the cranial vault. The optic canal is the most posterior landmark of the orbit. It measures 10 mm in length. The thin piece of bone separating the optic canal from the superior orbital fissure is the optic strut. The optic strut and optic canal are a pa of the lesser wing of sphenoid bone.