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Dr. Kwon established Evolution Theory of Asian eyelid

 

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Medical Column

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Asian Single Eyelid(monolid)-Difference of eyes among races/ Ethnicities

1.Difference of eyes among races/ Ethnicities



Anthropologists call Asians as 'Mongoloids’. There is the anthropological hypothesis that the single eyelid is a outward phenotype which is the result of evolution for adaptation to relavant environments. Genetically, All modern humans are included into the subspecies Homo sapiens sapiens, i.e. the subspecies of Homo sapiens. According to the results of various analyses, Koreans are classified as part of the northern Mongoloid race and the southern Mongoloid race. Except for the southeast Asian and part of Chinese race, people of Korea, Manchuria, and north of part of the Great Wall of China are named as ‘a northern mongoloid’ and has characteristics such as small eyes without a double eyelid, epicanthus, a flat face with prominent cheekbones, and a mongolian spot on the buttocks. On the other hand, the southern Mongoloid race adapt to relatively warm climates in areas such as Polynesia, and Hawaii in the Pacific ocean. Most people from the oceanic regions and southern Asia have incomplete double eyelids, slight epicanthus, and bigger eyes than the people of the northern regions. They are called the 'southern mongoloids’. It is said that among Koreans, 70~80% of the people are north and 20~30% are the south. It has been reasoned that the racial differences of modern humans are just phenotypic variations. But, the developmental mechanism of Asian single eyelid was not suggested clearly. We reconsidered basically without stereotype for the Asian eyelid. Dr. Kwon suggests that the Asian epicanthus and single eyelid  has developed in evolutional process of eyelid(Kwon’s Theory).


2.Actual shape and differences of eyelid in Asians


Actual shape of eyelid and canthus



Examples) In most Asian single eyelid, eyes with a single eyelid seem so small in both of width and length, they look stuffy and puffy. Therefore, the refined image is hardly made and they always cause the eyes to look swollen and small as if the person is unintentionally glaring. 


The eyelashes are the true boundaries of the palpebral fissure. The eyelashes of a Caucasian is exposed completely and the eyes look clear. Also, the eye looks bigger with the parallel supratarsal crease of eyelid. In contrast, the eye of Asian without supratarsal crease is veiled by various amount of skin drooping and the eyeline where the lashes grow is hidden beneath the soft tissues called epiblepharon. The more the eyelid tissues droops down, the smaller and the puffier the eyes look. 



Example) Caucasian's canthal angle





Example) This picture shows a case of asymmetric shapes of the canthal angles and caruncles(the red tissue at inner corner) 



The canthus of Caucasian is exposed completely, whereas the inner part of medial canthus of Asian eye is veiled by the epicanthus. The shapes of the canthal angle are quite various, but generally Asian canthal angles are rounder and shorter than those of the Caucasians. There are various distortions of canthal shape in Asian medial canthus which have been affected in the eyelid evolution. Devolutional epicanthoplasty can restore original shape of medial canthus and reveal it completely. Epicanthoplasty also restore length of palphebral fissure and refine nasocanthal contour.




Examples) Magic epicanthoplasty combined with a non- incisional double eyelid surgery 




Examples) Double eyelid surgery, ptosis correction with epicanthoplasty. Notice minimal epicanthus before epicanthoplasty. 


Anatomical differences of eyelid between Caucasian and Asian




Anatomical charicteristics of Asian upper eyelid :

Thick, streched skin
Subcutaneous fat
Preseptal/pretarsal fat
Thickened, malpositioned orbicularis muscle
Lax, ballooned septum with lower insertion with levator aponeurosis
Prolapsed, hypertrophied preaponeurotic fat pad with incompentant septum
Weak, incomplete anterior expansions of the levator aponeurosis.
Stretched, weakened levator aponeurosis and Muller muscle
Smaller vertical height of tarsal plate


Although the eyelid is very thin, various tissues (skin, orbicularis muscle,septum,levator muscle, Muller muscle, tarsal plate, fat, conjunctiva) are composed in it. The levator muscle and mullermuscle are those that help open the eyes. In Caucasian, the levator aponeurosis is usually attached to the tarsus and skin of inferior part of eyelid . The strands of the muscle tissues (levator expansion) are attached to the back of the skin of the eyelid, and the skin attached is pulled during eye opening, then a double eyelid is formed. The fusional part of the orbital septum and levator aponeurosis in Caucasian eyelid is typically in the skin crease (8-12 mm from eyelid margin). Its location lies above the superior tarsal border(2-5mm), which limit the downward prolapse of the orbital fat pads and enable aponeurotic expansions to insert toward the subdermal surface of the pretarsal eyelid skin. Whereas the fusional part lies at the lower point in Asian eyelid and the height of tarsal plate is relatively less than Caucasian’s(more than 8mm in Caucasian). Because of the differences in the eyelid anatomy of Asians, the surgical methods ususally applied to Caucasian cases cannot yield the favorable result in Asian blepharoplasty. Considering the differences of the Asian eyelid and relationship of the epicanthus and double eyelid, structural Asian blepharoplasty based on devolutional concept should be applied to establish a appropriate plan and accomplish best results. The devolutional Asian blepharoplasty can yield much better, natural looking surgical results because it is basically different from conventional blepharoplasty based on Caucasian’s eyelid anatomy

For Asian blepharoplasty, the upper eyelid should be evaluated for :

Epicanthus and epiblepharon with/without orbicularis muscle
malposition
Existence or absence of crease
Excess and thickness of skin
Amount of preaponeurotic fat,usually pseudoherniated and hypertrophied
Blepharoptosis
Pericanthal skin tension
Shape of medial canthus
Brow ptosis and lacrimal gland ptosis
Inclination between medial canthus and lateral canthus
Eyelash direction and prickling around medial canthus
Skin fold on lower eyelid and related wrinkles


<Teuim Clinic Dr.Kwon>






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