A vertical fold of skin over the angle of the inner canthus of the eye. It may be slight or marked, covering the canthus and the caruncle. Also called epicanthus, epicanthal fold, epicanthic fold.

Epicanthic folds may be seen in young children of any ethnicity before the bridge of the nose begins to elevate. They may persist where birth is pre-term.

A Mongolian fold is a typical characteristic among North American Indian and Northeast Mongolian races. It often refers to a type of fold where the skin hangs down from the epicanthal region, which passes through the corner of your eyes and finally covers the inner canthus of your eye. Statistics show that most Koreans have Mongolian folds starting from the canthal area, covering the corner of the eyes in various ways. This can create a small and stuffy look of the eye and can worsen one’s impression. The weaker the Mongolian fold, the more refined your eyes’ impressions become. In some ethnicities, the presence of an epicanthic fold is associated with a less prominent upper eyelid crease, commonly termed "single eyelids" as opposed to "double eyelids". The two features are distinct, a person may have both epicanthic fold and upper eyelid crease, one or neither.

If there is no Mongolian fold in one’s eyes, it can be said that he or she has more dominant genes of other races than those of the North Mongolian race. It is a hereditary trait in Asian people and is of no clinical significance.

Example) Typical eyes with a single eyelid accompanied with Mongolian folds