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': 'All of the following ocular structures are derived embryologically from the neuroectoderm except: \nSelect and explain. \nA. Epithelial layers of ciliary body and iris, B. Sphincter and dilator pupillae muscles, C. Optic nerve, D. Optic nerve sheaths', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Ans. Optic nerve sheaths', 'role': 'assistant'}]