The anatomy of the common canaliculus.

BACKGROUND: The functional valve between the common canaliculus and the lacrimal sac has traditionally been attributed to the valve of Rosenmüller, although this anatomical structure has never been rigorously documented. OBJECTIVE: To define the anatomy of the canaliculus-sac junction. METHODS: Twelve rigid plastic casts of the lacrimal outflow systems were obtained in human cadaver specimens using a well-known biologic casting material (partially polkymerized monomer to which a catalyst and promoter were added). RESULTS: A consistent pattern of angulation within the canalicular system was documented. The canaliculi bend posteriorly behind the medial canthal tendon, then anteriorly to enter the sac at an acute mean angle of 58 degrees to the lateral wall of the sac. CONCLUSIONS: This consistent configuration at the canaliculus-sac junction has not been previously described and may contribute to the 1-way valve phenomenon seen in some lacrimal disorders.