epicanthic fold

An epicanthic fold or epicanthus (/ˌɛpɪˈkænθəs/) is a vertical fold of skin on either side of the nose, sometimes covering the inner canthus (medial canthus) of the eye. However, variation occurs in the nature of this feature and the presence of "partial epicanthic folds" or "slight epicanthic folds" is noted in the relevant literature. Various factors influence whether epicanthic folds form, including ancestry, age, and certain medical conditions.

The primary cause of the epicanthic fold is the hypertrophy of the preseptal (anterior to the orbital septum) portion of the orbicularis oculi muscle.