An epicanthal fold, epicanthic fold or epicanthus is a skin fold of the upper eyelid (from the nose to the inner side of the eyebrow) covering the inner corner (medial canthus) of the human eye.
The term "epicanthal fold" refers to a visually categorized feature; however the underlying physiological reason and purpose for its presence in any given individual may be entirely different.
All humans initially develop epicanthal folds in the womb. Some children have lost them at birth, but epicanthal folds may also be seen in young children of any ethnicity before the bridge of the nose begins to elevate.
The maintenance of the epicanthic fold into adulthood in many populations is believed to be an evolutionary defense against both the extreme cold as well as the extreme light that occurs in the Eurasian arctic and north. It has also been suggested that the fold provides some protection against dust in areas of desert such that found in the deserts of northern China and Mongolia as well as parts of Africa.
There is a wide distribution of the epicanthic fold across the world. It is found in significant numbers amongst Native Americans, the Khoisan of Southern Africa, many Central Asians and some people of Sami origin. The presence of epicanthal folds is common in people of many, though not all, groups of East Asian and Southeast Asian descent. It also occurs sometimes on people of South Asian descent. Due to classic genetics children of a parent with a pronounced epicanthal fold and one without an epicanthal fold will have varying degrees of epicanthal folds as a result.
In Asian cultures, the presence of an epicanthal fold is associated with the lack of an upper eyelid crease, commonly termed "single eyelids" as opposed to "double eyelids". The two features are distinct; a person may have both epicanthal fold and upper eyelid crease, one and not the other, or neither.
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"Epicanthal fold".
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