Fig. 23. Lacrimal drainage system. A. Measurements. B. Valves of the lacrimal sac and nasolacrimal duct. (A from Jones LT, Wobig JL: Surgery of the Eyelids and Lacrimal System. Birmingham, Aesculapius, 1976. B from Bergin DJ: Anatomy of the eyelids, lacrimal system, and orbit. In McCord CD, Tanenbaum M, Nunery WR [eds]: Oculoplastic Surgery [3rd ed]. New York, Raven Press, 1995).