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': 'Basic lesion in tobacco amblyopia is \nSelect and explain. \nA. lschaemia of optic nerve fibres, B. Degeneration of ganglion cells especially of macular region, C. Degeneration of foveal cones, D. All of the above', 'role': 'user'}, {'content': "Answer: B \nExplanation: Tobacco amblyopia It typically occurs in men who are generally pipe smokers, heavy drinkers and have a diet deficient in proteins and vitamin B complex; and thence also labelled as 'tobacco-alcohol-amblyopia. Pathogenesis: The toxic agent involved is cyanide found in tobacco. Ref:- A K KHURANA; pg num:-296", 'role': 'assistant'}]