Purpose: To report that the medial canthal tendon (MCT) is not simply the aggregate of the orbicularis oculi muscle (OOM) and its tendon.
Methods: Twenty eyelids of 10 cadavers were used. The cadavers, seven male and three female, were all Japanese, with an average age of death of 76.2 years. The relationship between the MCT and the OOM, and between the tarsus and Horner's muscle were investigated. Histological findings were obtained with hematoxylin and eosin staining.
Results: The MCT was structured with an anterior lobe, the tendon from the tarsal area of the OOM, and a posterior lobe, the muscle-tendon transition area in the orbital area of the OOM. The nasal aspect of the tarsus was fixed by Horner's muscle.
Conclusions: The MCT and Horner's muscle are located in an important area of the eyelid; therefore, it is essential to understand their precise anatomy.