Lacrimal drainage system-physiology The puncta should be open and in firm apposition to the globe. The tears drain into the puncta from the tear meniscii along the lid margins by capillary action and also due to the negative pressure created by the sac. As the sac is surrounded by the orbicularis muscle, normal blinking movements result in negative pressure in the sac when the lids are open and positive pressure when,the lids are closed.Lacrimal drainage system - physiology • The puncta should be open and in firm apposition to the globe. • The tears drain into the puncta from the tear meniscii along the lid margins by capillary action and also due to the negative pressure created by the sac. • As the sac is surrounded by the orbicularis muscle, normal blinking movements result in negative pressure in the sac when the lids are open and positive pressure when, the lids are closed