This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Lens, Subject name: Ophthalmology
[{'content': 'Nuclear cataract can cause- \nSelect and explain. \nA. Myopia, B. Hyperopia, C. Presbyopia, D. Astigmatism', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Nuclear cataract causes index myopia. Ref: Duker 21st/e p.412.', 'role': 'assistant'}]