Eyelid
Closed human eye showing eyelid and a set of lashes which grow along the edge of the lid
The same eye with its eyelid pulled open, displaying meibomian glands on the inside and a set of lashes growing in multiple layers
Details
SystemIntegumentary
FunctionCovers and protects the eye by blinking or closing, keeping the cornea moist
Identifiers
Latinpalpebrae
MeSHD005143
TA98A15.2.07.024
TA2114, 115
FMA54437
Anatomical terminology
Blood vessels of the eyelids, front view
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An eyelid (/ˈ.lɪd/ EYE-lid) is a thin fold of skin that covers and protects an eye. The levator palpebrae superioris muscle retracts the eyelid, exposing the cornea to the outside, giving vision. This can be either voluntarily or involuntarily. "Palpebral" (and "blepharal") means relating to the eyelids. Its key function is to regularly spread the tears and other secretions on the eye surface to keep it moist, since the cornea must be continuously moist. They keep the eyes from drying out when asleep. Moreover, the blink reflex protects the eye from foreign bodies. A set of specialized hairs known as lashes grow from the upper and lower eyelid margins to further protect the eye from dust and debris.

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 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.

Structure

Layers

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 the eyelid and secrete the lipid part of the tear film.

Skin

The skin is similar to areas elsewhere, but is relatively thin[1] 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.[2] The skin of the eyelid contains the greatest concentration of sebaceous glands found anywhere in the body.[1]

Nerve supply

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 the trigeminal nerve.

Blood supply

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.

Eyelashes

Main article: Eyelash

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 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.

Function

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 the protection of the eye from dust and foreign debris, as well as from perspiration.

Clinical significance

Any condition that affects the eyelid is called eyelid disorder. The most common eyelid disorders, their causes, symptoms and treatments are the following:

Eyelid affected by stye

Surgery

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 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 the area on which the operation is performed is so close to the eye.

Anatomical variation

Further information: Epicanthic fold

A South Korean woman, before (left) and after (right) undergoing double eyelid surgery. Note the presence of the epicanthic fold in both photographs.

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 is almost universal, specifically in East Asians and Southeast Asians, where a majority, up to 90% in some estimations, of adults have this feature.[8]

The upper eyelid crease is a common variation between people of White and East Asian ethnicities.[9] Westerners commonly perceive the East Asian upper eyelid as a "single eyelid".[9] However, East Asian eyelids are divided into three types – single, low, and double – based on the presence or position of the lid crease.[10] 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.[9] Single/double eyelids are polygenic traits.[11]

Prevalence

Prevalence of double eyelid among Asian populations[12]
Year Ethnic group Gender Prevalence of double eyelid
1896 Japanese Female 82–83%
2000 Chinese Singaporean Female 66.7%
2007 Korean Male 24.1%
Female 45.5%
2008 Asian Male 30.3%
Female 41.3%
2009 Asian N/A 50.0%
2013 Taiwanese Chinese Female 83.1%

Society and culture

Further information: Chinese ideals of female beauty § Double eyelid

Cosmetic surgery

Blepharoplasty is a cosmetic surgical procedure performed to correct deformities and improve or modify the appearance of the eyelids.[13] With 1.43 million people undergoing the procedure in 2014,[14] 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.[15]

East Asian blepharoplasty, or "double eyelid surgery", has been reported to be the most common aesthetic procedure in Taiwan and South Korea.[16] 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.[17] A procedure to remove the epicanthal fold (i.e. an epicanthoplasty) is often performed in conjunction with an East Asian blepharoplasty.[18]

The use of double sided tape or eyelid glue to create 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.[19] Blepharoplasty has become a common surgical operation that is actively encouraged, whilst other kinds of plastic surgery are actively discouraged in Chinese culture.[20]

Death

After death, it 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.

Additional images

See also

References

  1. ^ a b Goldman, Lee (25 July 2011). Goldman's Cecil Medicine (24th ed.). Philadelphia: Elsevier Saunders. p. 2426. ISBN 978-1437727883.
  2. ^ "eye, human." Encyclopædia Britannica. Encyclopædia Britannica Ultimate Reference Suite. Chicago: Encyclopædia Britannica, 2010.
  3. ^ "Facts About Blepharitis". Archived from the original on 14 April 2010. Retrieved 30 March 2010.
  4. ^ "Upper Eyelid Edema Treatment and Symptoms". Archived from the original on 15 March 2010. Retrieved 30 March 2010.
  5. ^ "Eyelid and Orbital Tumors". Retrieved 30 March 2010. "Eyelid and Orbital Tumours". Archived from the original on 26 August 2014. Retrieved 22 August 2014.
  6. ^ "Eyelid twitch". Retrieved 30 March 2010.
  7. ^ Taber's Cyclopedic Medical Dictionary, Edition 21, Page-6.
  8. ^ Lee, Y., Lee, E. and, Park, W.J. (2000) Anchor epicanthoplasty combined with outfold type double eyelidplasty for Asians: do we have to make an additional scar to correct the Asian epicanthal fold? Plast. Reconstr. Surg. 105:1872–1880
  9. ^ a b c Jeong S, Lemke BN, Dortzbach RK, Park YG, Kang HK (July 1999). "The Asian upper eyelid: an anatomical study with comparison to the White eyelid". Archives of Ophthalmology. 117 (7): 907–12. doi:10.1001/archopht.117.7.907. PMID 10408455.
  10. ^ Han, M. H., & Kwon, S. T. (1992). A statistical study of upper eyelids of Korean young women. Journal of the Korean Society of Plastic and Reconstructive Surgeons, 19(6), 930-935.
  11. ^ Wang, Peiqi; et al. (2022). "Novel genetic associations with five aesthetic facial traits: A genome-wide association study in the Chinese population". Frontiers in Genetics. 13.
  12. ^ Lu, Ting Yin; Kadir, Kathreena; Ngeow, Wei Cheong; Othman, Siti Adibah (1 November 2017). "The Prevalence of Double Eyelid and the 3D Measurement of Orbital Soft Tissue in Malays and Chinese". Scientific Reports. 7 (1): 1–9. doi:10.1038/s41598-017-14829-4. ISSN 2045-2322. PMC 5665901. PMID 29093554.
  13. ^ "Eyelid Surgery". American Society of Plastic Surgeons. Retrieved 16 March 2023.
  14. ^ Taylor, Rosie. "July 2015 ISAPS Global Statistics Release." International Society of Aesthetic Plastic Surgery (2015): n. pag. Web. 8 Jul 2015. http://www.isaps.org/Media/Default/global-statistics/July%202015%20ISAPS%20Global%20Statistics%20Release%20-%20Final.pdf Archived 24 August 2015 at the Wayback Machine
  15. ^ "Quick Facts: Highlights of the ISAPS 2014 Statistics on Cosmetic Surgery." International Society of Aesthetic Plastic Surgery (2015). Web. http://www.isaps.org/Media/Default/global-statistics/Quick%20Facts%202015v2.pdf Archived 22 March 2016 at the Wayback Machine
  16. ^ Liao WC, Tung TC, Tsai TR, Wang CY, Lin CH (2005). "Celebrity arcade suture blepharoplasty for double eyelid". Aesthetic Plastic Surgery. 29 (6): 540–5. doi:10.1007/s00266-005-0012-5. PMID 16237581. S2CID 11063260.
  17. ^ "Blepharoplasty". www.mayoclinic.org. Mayo Clinic. 27 April 2016. Retrieved 16 March 2023.
  18. ^ Yen MT, Jordan DR, Anderson RL (January 2002). "No-scar Asian epicanthoplasty: a subcutaneous approach". Ophthalmic Plastic and Reconstructive Surgery. 18 (1): 40–4. doi:10.1097/00002341-200201000-00006. PMID 11910323. S2CID 42228889.
  19. ^ Levinovitz, Alan (22 October 2013). "Chairman Mao Invented Traditional Chinese Medicine". Slate (magazine). Retrieved 2 July 2016
  20. ^ Cornell, Joanna. "In the Eyelids of the Beholder." Yale Globalist (2010): n. pag. Web. 2 Mar 2011. http://tyglobalist.org/perspectives/in-the-eyelids-of-the-beholder/ Archived 3 October 2017 at the Wayback Machine

Sources