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.

The anatomy of Whitnall ligament.

BACKGROUND: The current understanding of the anatomy of Whitnall ligament does not explain its functional role in eyelid movement. This anatomic study was designed to determine the exact relation of Whitnall ligament to the levator muscle and aponeurosis. METHODS: The anatomy of the eyelid was examined by surgical dissection of 20 eyelids undergoing Müllerectomy via a conjunctival approach, anatomic dissection of 20 fresh cadaver orbits, and histologic correlation in four fresh specimens. RESULTS: Whitnall ligament is a sleeve of fibrous tissue with both a superior and inferior component which join medially and laterally before inserting onto the bony orbit. CONCLUSIONS: The authors postulate that this sleeve acts as a mobile fulcrum straddling the underneath surface of the levator aponeurosis and functions to convert the anterior-posterior vector force of the levator to a superior-inferior direction during eyelid movement. This model proposes that when the levator is relaxed, Whitnall sleeve hangs down, allowing the lid to close. When the muscle contracts, the sleeve along with the levator aponeurosis is lifted superiorly in the orbit, enhancing the lifting effect of levator muscle contraction in eyelid elevation.

The effect of fluorescein volume on lacrimal outflow transit time.

The Jones primary dye test is a commonly used test of lacrimal outflow. Some clinicians, however, find it of limited practical significance because of variable outcome and relatively low sensitivity in documenting normal lacrimal excretory function. We hypothesized that an important variable affecting the transit time may be the volume of fluorescein used in the primary dye test. To accurately determine the exact time from insertion of dye into the eye to its appearance in the nose, using a rigid nasal endoscope, we directly visualized the dye as it appeared at the ostium of the nasolacrimal duct. Fifty nasolacrimal outflow systems were examined in 25 normal volunteers. The fluorescein dye transit time was determined using a single drop of fluorescein on one side and multiple drops of fluorescein on the other side. Using a single drop of fluorescein, the median dye transit time was 8 min, compared to 1.4 min using multiple drops. These results suggest that the volume of fluorescein used may be an important factor affecting variability in the outcome of the primary dye test.