This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: All India exam, Subject name: Microbiology
[{'content': 'In open-angle glaucoma investigation least done is \nSelect and explain. \nA. Indirect ophthalmoscopy, B. Tonometry, C. Direct ophthalmoscopy, D. Perimetry', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Investigations to be done in open-angle glaucoma are :Slit lamp examinationTonometryGonioscopyDirect ophthalmoscopyPerimetry', 'role': 'assistant'}]