The medial canthus is a vertical fold of skin that occurs at the inner canthus and is usually bilateral and congenital. Caucasians have almost no medial canthus, and it is more common in the yellow race. In China, 80% of children under 10 years of age have canthus, although the age and nasal development of the canthus gradually reduced to 10 years of age tends to stabilize. The canthus is a type of canthus that starts from the upper eyelid crease and ends at the inner canthus. 2. The lid-type canthus starts from the upper eyelid and extends downward through the inner canthus to the lower eyelid, sometimes fusing with the nasal cheek crease. 3. According to national and international studies, congenital canthus is an autosomal dominant trait that is characteristic of the Mongolian race. The treatment principle is to relieve the tension in the vertical direction by various means. The congenital medial canthus is often bilateral, with the medial canthus and tear trough partially obscured, resulting in a pseudo-“internal strabismus” appearance. The canthus can disappear when the skin is pinched on the bridge of the nose, and sometimes the lower lid canthus can be accompanied by an inverted eyelash, touching the cornea and causing photophobia and tearing. Treatment Mild canthus alone does not require treatment if it has no clinical symptoms and does not affect the appearance. In adults, blepharoplasty is performed, but in cases of moderate canthus and above, the result of the surgery can be compromised and canthopexy (commonly known as an open eye) can be corrected at the same time. The most commonly used surgical method is the “Z” procedure, in which A and B are the two transposition flaps of the Z procedure.