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': "Retinitis pigmentosa forms a constituent of all the following syndromes except: \nSelect and explain. \nA. Lowe's syndrome, B. Refsum's syndrome, C. Usher's syndrome, D. Hallgren's syndrome", 'role': 'user'}, {'content': "Answer: A \nExplanation: Ans. Lowe's syndrome", 'role': 'assistant'}]