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.
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.