PANS-OPS Vol 1
7.3.3 Minimum descent altitude/height (MDA/H)
When the OCA/H is established, an MDA/H is also specified to allow for operational considerations. Descent below MDA/H should not be made until:
a) visual reference has been established and can be maintained;
b) the pilot has the landing threshold in sight; and
c) the required obstacle clearance can be maintained and the aircraft is in a position to carry out a landing.