This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Glaucoma, Subject name: Ophthalmology
Which procedure is being done in the patient? 
Select and explain. 
A. Applanation tonometry, B. A scan ultrasonography, C. Indentation tonometry, D. Keratometry
C: Indentation tonometry
Answer: C: Indentation tonometry 
Explanation: Ans. (c) Indentation tonometryRef: Parson's 22/e. p. 126The instrument in the image is a Schiotz tonometer - which is based on principle of Indentation tonometry - a plunger will indent and thus displace aqueous to raise IOP more in a soft eye than a hard eye.