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': 'Which one of the following statements, concerning persistent hyperplastic primary vitreous (PHPV) is not true ?a) It is generally unilateralb) Visual prognosis is usually goodc) It may calcifyd) It is most easily differentiated from retinoblastoma by the presence of exophthalmos or cataract \nSelect and explain. \nA. abc, B. bcd, C. ac, D. bd', 'role': 'user'}, {'content': 'Answer: B \nExplanation: PHPV is almost always (90%) unilateral.\nVisual prognosis is bad as neither conservative treatment nor surgery can improve visual acuity.\nThere is no calcification, which is a differentiating feature from retinoblastoma.\nPHPV can be differentiated from retinoblastoma by presence of cataract in PHPV but not by exophthalmos.', 'role': 'assistant'}]