###Rationale: Investigations to be done in open-angle glaucoma are :Slit lamp examinationTonometryGonioscopyDirect ophthalmoscopyPerimetry

###Answer: OPTION A IS CORRECT.
###Question: In open-angle glaucoma investigation least done is
###Options:
A. Indirect ophthalmoscopy
B. Tonometry
C. Direct ophthalmoscopy
D. Perimetry
