<prompt> Followup of cataract operations in national blindness control program is done byActive surveillancePassive surveillanceSentinel surveillanceRoutine check-up  <response>: 25 sentinel surveillance units have been established in departments 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. 