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': 'Visually-evoked response (VER) is useful in the diagnosis of all of the following except: \nSelect and explain. \nA. Retinitis pigmentosa, B. Retrobulbar neuritis, C. Visual potential in eyes with opaque media, D. Optic atrophy', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Ans. Retinitis pigmentosa', 'role': 'assistant'}]