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': "All of the following are true for colloid bodies (drusens) except: \nSelect and explain. \nA. Are hyaline excrescences of Bruch's membrane, B. Are secreted by pigment epithelial cells, C. Are usually associated with marked loss of vision, D. Are a percursor of disciform maci degeneration in some eyes", 'role': 'user'}, {'content': 'Answer: C \nExplanation: Ans. Are usually associated with marked loss of vision', 'role': 'assistant'}]