Misplaced Pages

#968031

28-416: The appearance of the human upper eyelid often varies between different populations. The prevalence of an epicanthic fold covering the inner corner of the eye account for the majority of East Asian and Southeast Asian populations, and is also found in varying degrees among other populations. Separately, but also similarly varying between populations, the crease of the remainder of the eyelid may form either

56-469: A "single eyelid", a "double eyelid", or an intermediate form. Eyelids can be found in other animals, some of which may have a third eyelid, or nictitating membrane . A vestige of this in humans survives as the plica semilunaris . The eyelid is made up of several layers; from superficial to deep, these are: skin , subcutaneous tissue , orbicularis oculi , orbital septum and tarsal plates , and palpebral conjunctiva . The meibomian glands lie within

84-480: A considerably lower frequency, in other populations: Europeans (e.g., Scandinavians , English , Irish , Hungarians , Russians , Poles , Lithuanians , Latvians , Finns , Estonians and Samis ), Jews , South Asians ( Bengalis , Sinhalese , among other groups in eastern and southern South Asia), Nilotes , Cushites , and Amazigh people. The degree of development of the fold between individuals varies greatly, and attribution of its presence or absence

112-567: A sign of congenital abnormality, such as in Zellweger syndrome and Noonan syndrome . Medical conditions that cause the nasal bridge not to develop and project are also associated with epicanthic fold. About 60% of individuals with Down syndrome (also known as trisomy 21) have prominent epicanthic folds. Other examples are fetal alcohol syndrome , phenylketonuria , and Turner syndrome . Anatomical variation An anatomical variation , anatomical variant , or anatomical variability

140-448: Is a cosmetic surgical procedure performed to correct deformities and improve or modify the appearance of the eyelids. With 1.43 million people undergoing the procedure in 2014, blepharoplasty is the second most popular cosmetic procedure in the world (Botulinum toxin injection is first), and the most frequently performed cosmetic surgical procedure in the world. East Asian blepharoplasty , or "double eyelid surgery", has been reported to be

168-773: Is a presentation of body structure with morphological features different from those that are typically described in the majority of individuals. Anatomical variations are categorized into three types including morphometric (size or shape), consistency (present or absent), and spatial ( proximal / distal or right/left). Variations are seen as normal in the sense that they are found consistently among different individuals, are mostly without symptoms, and are termed anatomical variations rather than abnormalities. Anatomical variations are mainly caused by genetics and may vary considerably between different populations . The rate of variation considerably differs between single organs , particularly in muscles . Knowledge of anatomical variations

196-544: Is almost universal, specifically in East Asians and Southeast Asians, where a majority, up to 90% in some estimations, of adults have this feature. The upper eyelid crease is a common variation between people of White and East Asian ethnicities. Westerners commonly perceive the East Asian upper eyelid as a "single eyelid". However, East Asian eyelids are divided into three types – single, low, and double – based on

224-694: Is also commonly found in Northern India , especially in Kashmir . The Hazara people in Afghanistan and Pakistan commonly have this trait. Some people in Eastern/Northern Pakistan have this trait. In some of these populations, the trait is almost universal. This is especially true in East Asians and Southeast Asians, where a majority, up to 90% in some estimations, of adults have this feature. Epicanthic folds also occur, at

252-443: Is common in many cultures to pull the eyelids of the deceased down to close the eyes. This is a typical part of the last offices . Epicanthic fold An epicanthic fold or epicanthus is a skin fold of the upper eyelid that covers the inner corner (medial canthus ) of the eye . However, variation occurs in the nature of this feature and the possession of "partial epicanthic folds" or "slight epicanthic folds"

280-627: Is found in specific populations or ethnicities: East Asians , Southeast Asians , Central Asians , North Asians , Polynesians , Micronesians , Indigenous peoples of the Americas , and some African people (especially among Khoisan and Nilotic people ). Among South Asians , they occur at very high frequencies among the Nepalis , Bhutanese , Northeast Indians , Kirati people and certain Adivasi tribes of Eastern and Southern India . It

308-445: Is important in order to distinguish them from pathological conditions. A very early paper published in 1898, presented anatomic variations to have a wide range and significance, and before the use of X-ray technology, anatomic variations were mostly only found on cadaver studies. The use of imaging techniques have defined many such variations. Some variations are found in different species such as polydactyly , having more than

SECTION 10

#1732790909969

336-532: Is not open to this explanation. The epicanthic fold found in many African people has been tentatively linked to protection for the eye from the high levels of ultraviolet light found in desert and semi-desert areas. The exact evolutionary function and origin of epicanthic folds remains unknown. Scientific explanations include either random variation and selection (presumably sexual selection ), or possible adaption to desert environment and/or high levels of ultraviolet light found in high-altitude environments, such as

364-567: Is noted in the relevant literature. Various factors influence whether epicanthic folds form, including ancestry, age, and certain medical conditions. Epicanthus means 'above the canthus ', with epi-canthus being the Latinized form of the Ancient Greek ἐπί κανθός : 'corner of the eye'. Variation in the shape of the epicanthic fold has led to four types being recognised: The highest frequency of occurrence of epicanthic folds

392-412: Is often subjective, being to a degree relative to the occurrence of the trait within the community of the specific observer. Also, its frequency varies but can be found in peoples all over the world. Its use, therefore, as a phenotypic marker to define biological populations is debatable. The epicanthic fold is often associated with greater levels of fat deposition around the eyeball. The adipose tissue

420-433: Is thought to provide greater insulation for the eye and sinuses from the effects of cold, especially from freezing winds, and to represent an adaptation to cold climates. It has also been postulated that the fold itself may provide a level of protection from snow blindness . Though its appearance in peoples of Southeast Asia can be linked to possible descent from cold-adapted ancestors, its occurrence in various African peoples

448-594: The Himalayas . Dr. Frank Poirier, a physical anthropologist at Ohio State University, said that the epicanthic fold among Asian people is often explained as part of an adaptation to severe cold or tropical environments, however he suggests that neither of these explanations are sufficient to explain its presence in East and Southeast Asia, and notes that the fold can also be observed in Irish and African people. He attributes

476-405: The area on which the operation is performed is so close to the eye. An anatomical variation in humans occurs in the creases and folds of the upper eyelid. An epicanthic fold , the skin fold of the upper eyelid covering the inner corner (medial canthus ) of the eye, may be present based on various factors, including ancestry, age, and certain medical conditions. In some populations the trait

504-414: The body. In humans, the sensory nerve supply to the upper eyelids is from the infratrochlear , supratrochlear , supraorbital and the lacrimal nerves from the ophthalmic branch (V1) of the trigeminal nerve (CN V). The skin of the lower eyelid is supplied by branches of the infratrochlear at the medial angle. The rest is supplied by branches of the infraorbital nerve of the maxillary branch (V2) of

532-462: The epicanthic fold to pleiotrophic genes that control for more than one characteristic or function. He also did not offer an explanation for the origin of epicanthic folds. Many fetuses lose their epicanthic folds after three to six months of gestation. Epicanthic folds may be visible in the development stages of young children of any ethnicity, especially before the nose bridge fully develops. Epicanthic fold prevalence can sometimes be found as

560-488: The eye from dust and debris by catching them via rapid blinking when the blink reflex is triggered by the debris touching the lashes. Long lashes also play a significant part in facial attractiveness . The eyelids close or blink voluntarily and involuntarily to protect the eye from foreign bodies, and keep the surface of the cornea moist. The upper and lower human eyelids feature a set of eyelashes which grow in up to 6 rows along each eyelid margin, and serve to heighten

588-430: The eyelid and secrete the lipid part of the tear film . The skin is similar to areas elsewhere, but is relatively thin and has more pigment cells. In diseased persons, these may wander and cause a discoloration of the lids. It contains sweat glands and hairs, the latter becoming eyelashes as the border of the eyelid is met. The skin of the eyelid contains the greatest concentration of sebaceous glands found anywhere in

SECTION 20

#1732790909969

616-517: The illusion of creased, or "double" eyelids has become a prominent practice in China and other Asian countries. There is a social pressure for women to have this surgery, and also to use the alternative (taping) practices. Blepharoplasty has become a common surgical operation that is actively encouraged, whilst other kinds of plastic surgery are actively discouraged in Chinese culture. After death , it

644-455: The look of the face and to boost self-confidence by restoring a youthful eyelid appearance. They are intended to remove fat and excess skin that may be found on the eyelids after a certain age. Eyelid surgeries are also performed to improve peripheral vision or to treat chalazion , eyelid tumors, ptosis , extropion, trichiasis , and other eyelid-related conditions. Eyelid surgeries are overall safe procedures but they carry certain risks since

672-578: The most common aesthetic procedure in Taiwan and South Korea. Though the procedure is also used to reinforce muscle and tendon tissues surrounding the eye, the operative goal of East Asian blepharoplasty is to remove the adipose and linear tissues underneath and surrounding the eyelids in order to crease the upper eyelid. A procedure to remove the epicanthal fold (i.e. an epicanthoplasty ) is often performed in conjunction with an East Asian blepharoplasty. The use of double sided tape or eyelid glue to create

700-508: The presence or position of the lid crease. Jeong Sang-ki et al. of Chonnam University , Kwangju , Korea , in a study using both Asian and White cadavers as well as four healthy young Korean men, said that "Asian eyelids" have more fat in them than those of White people. Single/double eyelids are polygenic traits. A 2011 study also states that Saudis of "pure Arab" descent generally have higher upper lid crease and upper lid skin fold heights, compared to other ethnic groups. Blepharoplasty

728-439: The protection of the eye from dust and foreign debris, as well as from perspiration. Any condition that affects the eyelid is called eyelid disorder. The most common eyelid disorders, their causes, symptoms and treatments are the following: The eyelid surgeries are called blepharoplasties and are performed either for medical reasons or to alter one's facial appearance. Most of the cosmetic eyelid surgeries are aimed to enhance

756-629: The trigeminal nerve. In humans, the eyelids are supplied with blood by two arches on each upper and lower lid. The arches are formed by anastomoses of the lateral palpebral arteries and medial palpebral arteries , branching off from the lacrimal artery and ophthalmic artery , respectively. The eyelashes (or simply lashes) are hairs that grow on the edges of the upper and lower eyelids. The lashes are short (upper lashes are typically just 7 to 8 mm in length) hairs, though can be exceptionally long (occasionally up to 15 mm in length) and prominent in some individuals with trichomegaly . The lashes protect

784-402: The usual number of digits. Kopsch gave a detailed listing of muscle variations. These included the absence of muscles; muscles that were doubled; muscles that were divided into two or more parts; an increase or decrease in the origin or insertion of the muscle; and the joining to adjacent organs. The palmaris longus muscle in the forearm is sometimes absent, as is the plantaris muscle in

#968031