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
In open Angle Glaucoma which investigation is least useful 
Select and explain. 
A. Indirect opthalmoscopy, B. Tonometry, C. Direct opthalmoscopy, D. Perimetry
A: Indirect opthalmoscopy
Answer: A: Indirect opthalmoscopy 
Explanation: A i.e. Indirect ophthalmoscopy Baseline Evaluation in PAOG before initiation of therapy includes Visual Acuity Slitlamp biomicroscopy to rule out any signs of secondary glaucomas Applanation Tonometry to measure the IOP (> 21 mm Hg) Gonioscopy to assess the angle (an open angle of normal appearance) Ophthalmoscopy to assess the optic disc (Best done by Direct Ophthalmoscopy) Perimetry to assess visual field to judge progress of the disease and grading