This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Diseases of the Optic Nerve, Subject name: Ophthalmology
[{'content': 'Colour blindness in ethambutol toxicity: \nSelect and explain. \nA. Red blue, B. Red green, C. Blue, D. Red green blue', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Ans. (b) Red greenRef : A.K. Khurana 6th ed. 1329* Optic neuritis, the most serious adverse effect reported due to ethambutol toxicity, typically presents as reduced visual acuity, central scotoma, and loss of the ability to see green (or, less commonly, red).* Please refer to pharmacology section for detailed discussion on ATT and their side effect.', 'role': 'assistant'}]