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: Social & Preventive Medicine
Follow-up ofcataract operations in national blindness control program is done by - 
Select and explain. 
A. Active surveillance, B. Passive surveillance, C. Sentinel surveillance, D. Routine check-up
C: Sentinel surveillance
Answer: C: Sentinel surveillance 
Explanation: Ans. is 'c' i.e., Sentinel surveillance o 25 sentinel surveillance units have been established in depaments of ophthalmology and PSM in medical collages in India for assessment of - Beneficiary profiles. Visual outcomes based on cataract surgery records. Follow-up of operated cases. Ocular morbity data.