• #1-3. Anatomical Concept of Asian Eyelid: Paradigm Shift to Evolution Eyelid Theory


    In fact, there are no structures in Asian eyes to be called a fold other than the palpebral fold. In the Asian eyelid, the only part that merits being called a fold, other than the palpebral fold, may be the lower canthal fold (fold of anterior skin edge of canthal margin). Many mistakenly think of this fold as epicanthus. Considering the commonly accepted medical definition of epicanthal fold is “the fold in the upper eyelid covering the tear trough,” we can see that the term “fold” is not suitable for describing the upper eyelid in Asians. A more anatomically accurate description of the Asian medial eye would be epicanthal drooping or drooping of supracanthal soft tissue and lower canthal fold. 


    Image 3. Asian single eyelid (or absence of palpebral fold).


    Before the Korean medical definition of epicanthus was revised to signify “medial eye fold” in 2001, epicanthus was called 內眼角贅皮. The character ‘贅’ means a lump or protruding skin. The term “內眼角贅皮” was coined by Japanese anatomists who were the first in Asia to adopt German anatomical concepts and this term is still used in Japan and China as a medical translation of epicanthus. This term essentially means excess skin in the eye corner and does not include the meaning of “fold.” The Japanese scholars at the time may have deemed the concept of fold unsuitable to describe epicanthus in Asians, as there are no fold-like structures in Asian upper eyelid near the medial eye. On the other hand, the term “Mongolian fold” that was once used synonymously with epicanthus is translated as 蒙古ひだ、蒙古襞 in Japanese, 蒙古襞, 蒙古褶 in Chinese and epicanthus in Korean. All three translations include the meaning of “fold.”


    Here, we can ask the question, why is there so much confusion regarding the terminology of epicanthus or Mongolian fold? To answer this question, we need to look at how the early concept of epicanthus came to be defined and how it changed in the past 180 years.


    In Asians, the palpebral fold, pericanthal soft tissues and medial canthus take widely varying forms. Presence of the palpebral fold or its various shapes and the degree of excess skin over the medial eye and its progression into the lower eyelid are thought have aesthetic significance. Many plastic surgeons would agree that the varying palpebral fold, medial eye soft tissues, or the medial canthus are anatomically related. However, very few studies so far have examined such anatomical association. Epicanthus was explained as a type of developmental anomaly found in Asian medial eye from the perspective of biological racism in the early 1800s when modern anatomy and plastic surgery were still in inception.


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    However, such a pathological concept is still accepted today even after biological racism was rejected by modern science. In 1831, Ammon applied the pathological concept of epicanthus in the Asian eyelid based on the teratological theory of group developmental arrest (Hemmungbildun). This theory posits that unlike Caucasian eyes, the epicanthus remains in most Asians as a group malformation. Such definition of epicanthus is accepted as a fact even today. The original meaning may have faded and it may now be used more as a descriptive term, however, today’s medical textbooks and papers still use the term “epicanthal fold.”


    To avoid confusion in academic discussions, we need to at least clarify the medical definition of epicanthus. Exactly what is epicanthus or epicanthal fold? And where does it exactly lie in the Asian eyelid? Does an anatomical structure even exist in the Asian eyelid that merits being called epicanthus? 

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