Medial horn supporting ligament in Asian upper eyelids.

The purpose of this study was to describe the medial horn supporting ligament (MHSL) attached to the medial horn of the levator aponeurosis. The authors examined 3 different groups of specimens: gross cadaveric samples, microscopic cadaveric samples and intraoperative samples from levator resections. In all eyelids in the gross cadaveric samples, the MHSL was attached from the superior to the medial surfaces of the medial horn, and ran deeper in the direction of the trochlea in the superior region. Furthermore, the MHSL continued to the Whitnall ligament and was partially attached to the trochlea. In the microscopic samples, the MHSL was located adjacent to the levator aponeurosis in all specimens. The MHSL was constituted by comparatively thick fibers with few smooth muscle fibers. Under the MHSL, another fibrous structure existed with minute fibers including much smooth muscle. In the intraoperative samples from levator resections, the MHSL was also observed in all specimens. The MHSL was released from the medial horn in the cases of lateral tarsal shifts, but not in cases without. The MHSL, an indicator of the medial margin of the levator aponeurosis, may provide support, tension and suspension to the medial margin of the medial horn, strengthening its fragility.