The epicanthic fold is the skin fold of the upper eyelid covering the inner angle of the eye.
Epicanthic fold, epicanthal fold, epicanthus, or simply eye fold are names for a skin fold of the upper eyelid, covering the inner corner (medial canthus) of the eye. Other names for this trait include plica palpebronasalis and palpebronasal fold. One of the primary facial features often closely associated with the epicanthic folds is the nasal bridge; all else equal, a lower-based nose bridge is more likely to cause epicanthic folds, and a higher-based nose bridge is less likely to do so. There are various factors influencing whether someone has epicanthic folds, including geographical ancestry, age, and certain medical conditions.
Epicanthic fold is typical in many peoples of Eastern Asia and is common among Central Asian populations. It is most frequent in northeastern Asia and eastern central Asia, such as Mongolia, Manchuria, Korea, central and northern China, central and eastern Siberia and much of Japan and its prevalence decreases when one goes south and west. It is also noticed among indigenous peoples of the Arctic like Inuits and Aleuts. Epicanthic folds are characteristic of San populations in Southern Africa. It is also found in significant numbers among Indigenous Americans.
Epicanthic fold is sometimes found as a congenital abnormality. Medical conditions that cause the nasal bridge not to mature and project are associated with epicanthic folds. One of the characteristics of a number of people with Down syndrome is prominent epicanthic folds. In 1862, John Langdon Down classified what is now called Down syndrome. He used the term mongoloid for the condition. This was derived from then-prevailing ethnic theory and from his perception that children with Down syndrome shared physical facial similarities (epicanthic folds) with those of Blumenbach's Mongolian race. While the term "mongoloid" (also "mongol" or "mongoloid idiot") continued to be used until the early 1970s, it is now considered pejorative and inaccurate and is no longer in common use.
According to Ashley Montagu who taught anthropology at Princeton University, "The Mongoloid skull, whether Chinese or Japanese, has been rather more neotenized than the Caucasoid or European". In his list of "neotenous structural traits in which Mongoloids... differ from Caucasoids", Montagu lists "Larger brain, larger braincase, broader skull, broader face, flat roof of the nose, inner eye fold, more protuberant eyes, lack of brow ridges,.... less hairy, fewer sweat glands, fewer hairs per square centimeter and long torso". 
It is hypothesized that epicanthic folds are caused by climatic factors and it may have originated more than once during human evolution. The genetic basis of epicanthic folds is not well understood.
Epicanthic eyes vary possibly because they are adapted to different climates. In the warm climate of the Far East, Far East Asians have more fat on their eyelids which causes an inner eyelid fold.  This fat warms the eyes, conserving body heat.
- Double eyelid surgery
- Epicanthoplasty, the surgical modification of epicanthic folds
- Human physical appearance
|Wikimedia Commons has media related to Epicanthic fold.|
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