One-way flow in the lacrimal drainage system: determinants from the basic sciences.

All life processes must be compatible with known physical laws. While the physiology of the lacrimal pump and valvular system are well known, the physical and histologic aspects related to anatomy remain to be clarified. Maximization of forward-directed capillarity, the operation of Bernoulli's law, the Venturi tube effect, and histologic microciliation are related to the system's basic anatomy and directed toward forward flow only, or, conversely, the avoidance of backflow of nasal secretions toward the conjunctival sac.