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': 'Marcus Gunn pupil is a feature of all, EXCEPT: \nSelect and explain. \nA. Optic neuritis, B. Papilloedema, C. Optic atrophy, D. Retinal detachment', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Marcus Gunn Pupil: In swinging flashlight test, the pupil on the diseased side dilates on transferring light to it. It is positive in the following cases: Optic neuritis Optic atrophy Retinal detachment Central retinal vein occlusion Central retinal aery occlusion Ref: Review of ophthalmology A.K.Khurana, 5Th Ed, page 22.', 'role': 'assistant'}]