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': 'In open Angle Glaucoma which investigation is least useful – \nSelect and explain. \nA. Indirect opthalmoscopy, B. Tonometry, C. Direct opthalmoscopy, D. Perimetry', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Actually all the investigations, provided in the options, can be used in POAG.\n\n"A good baseline evaluation and a record of all parameters - IOP (Tonometry), perimetly, optic nerve head evaluation\xa0and gonioscopy - over the years should be available for proper management".\xa0\xa0-- Parson\'s\n"Careful examination of disc changes can be made by direct ophthalmoscopy, slit lamp bimicroscopy and indirect\xa0ophthalmoscopy". \xa0—Khurana 4th /e 216\n\nAs you all know, indirect ophthalmoscopy is usually not used for central retina (optic disc), it is used for peripheral retina, therefore, it is the single best answer here.\nForget about above discussion, you just remember following information :-\n\nCommonly used investigations in POAG → Gonioscopy, Tonometry, direct ophthalmoscopy / slit lamp\xa0biomicroscopy, Perimetry.', 'role': 'assistant'}]