This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Neuro Ophthalmology, Subject name: Ophthalmology
[{'content': 'Which of the following is a cause of sudden blindness in a quiet eye with normal media and fundus? \nSelect and explain. \nA. Retrobulbar neuritis, B. Vitreous hemorrhage, C. Optic neuritis, D. Iridocyclitis', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Retrobulbar neuritis: sudden blindness with normal media and fundus. In retrobulbar neuritis, disc edema is absent.', 'role': 'assistant'}]