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: Unknown
In open angle glaucoma investigation least done is : 
Select and explain. 
A. Indirect ophthalmoscopy, B. Tonometry, C. Direct ophthalmoscopy, D. Perimetry
A: Indirect ophthalmoscopy
Answer: A: Indirect ophthalmoscopy 
Explanation: Investigations to be done in open angle glaucoma are :
Slit lamp examination
Tonometry
Gonioscopy
Direct ophthalmoscopy
Perimetry