Role of the Medial Canthus Fibrous Band in Forming Moderate and Severe Epicanthal Folds in Asians and Its Clinical Application

Background: Epicanthal folds (EFs) are skin folds located at the medial canthus in Asians. However, the anatomical structure of EFs remains unclear. The authors discovered a fibrous band connected to the medial canthal tendon (MCT) and referred to it as the medial canthal fibrous band (MCFB). This study aimed to verify whether the MCFB is different from the MCT and whether its unique anatomical relationship with the MCT plays an important role in EF formation. Methods: Forty patients who underwent epicanthoplasty from February of 2020 to October of 2021 were included. EFs from 11 patients underwent biopsy and were stained with hematoxylin and eosin, Masson trichrome, and Weigert stains to reveal their composition. Expression of collagens I and III and elastin was determined through immunohistochemical staining, and their mean optical density was measured. Preoperative and immediate exposed lacrimal caruncle area (ELCA) was measured after removing the MCFB. Results: The MCFB is a fibrous tissue located in the EF and above the MCT. The orientation and composition of collagen fibers of the MCFB are different from those of the MCT ( P < 0.001). The MCFB also has more elastin fibers than the MCT ( P < 0.05). Immediate ELCA was significantly higher than before ELCA ( P < 0.001) once the MCFB was removed. Conclusions: The MCFB is composed of collagen fibers different from those in the MCT and plays a role in EF formation. Removing the MCFB during epicanthoplasty can result in a more attractive appearance postoperatively. CLINICAL QUESTION/LEVEL OF EVIDENCE: Therapeutic, IV.