This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Techniques of Ocular Examination and Diagnostic Tests, Subject name: Ophthalmology
Which instrument is used to visualize the angle of anterior chamber? (D. REPEAT 2013) 
Select and explain. 
A. Slit lamp examination, B. Keratometry, C. Gonioscopy, D. Indirect ophthalmoscopy
C: Gonioscopy
Answer: C: Gonioscopy 
Explanation: Ref: Basok's Essentials of Ophthalmology, 5th editionExplanation:ANGLE OF ANTERIOR CHAMBER (COCKPIT OF GLAUCOMA)The inner layers of sclera contain circular venous sinus called Canal of Schlemm w hich is lined by endothelium.Between Schlemm's canal and recess of anterior chamber, lies loose meshwork of tissue known as Trahacular meshwork.Angle of anterior chamber is best visualized by Gonioscope.Normally the angle is wide open (20-45 Degress).Chance of developing angle closure glaucoma is high when angle is <10 degress.NOTEPachvmeter: Measures thickness of cornea.Keratometry: Measure curvature of cornea.Campimetry: Measures field of vision.