This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Glaucoma, Subject name: Ophthalmology
[{'content': 'Which of the following is not a source of error in the applanation tonometry: \nSelect and explain. \nA. High Pressure on the globe, B. Tear film, C. Astigmatism, D. Wide pulse pressure', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Tear film is required for accurate measurement , is not a source of error. Sources of error in tonometry: Inappropriate fluorescein pattern. Pressure on the globe. Central Corneal thickness. Corneal edema. Pulse pressure. Astigmatism. Incorrect calibration. Wide pulse pressure.', 'role': 'assistant'}]