Lacrimal flow.

Syncinetic reflex or isolated orbicularis muscle contraction squeezes the tearsac between Horner's muscle and the inner palpebral ligament, closes the canaliculi and prevents conjunctival fornix backflow, while the tears are expressed (pseudo-peristaltism) towards the nose through the flexible naso-lacrimal canal. The diameter at the level of the canaliculi should be kept optimal in order to allow proper suction towards the tearsac and free capillarity since surface tension varies to a lesser extent. Scopy of contrast lacrimal outflow-channels provides important information on the morphology and the physiopathology of the lacrimal ducts, ruling out eventual functional origin of the lacrimation. The technique is especially important in decision making for treatment (allergic conditions, congenital dacryocystitis) for evaluation of dacryocystorhinostomy, for the early diagnosis and management of infection, inflammation and posttraumatic conditions of the face and anterior skull.