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': 'Papilloedema is characterised by all of the following EXCEPT- \nSelect and explain. \nA. Loss of retinal venous pulsations, B. Transient obscurations of vision, C. Sudden painless loss of vision, D. Disc oedema', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Vision loss occurs in long standing papilloedema (not in acute pappiloedema), and that occurs in less than 25% of patients.\nPost neuritic atrophy also occurs in long standing papilloedema and not acute papilloedema.', 'role': 'assistant'}]