View source for Medicine:Canthus

{{Short description|Corner of the eye where the upper and lower eyelids meet}}
{{Infobox anatomy
| Name        = Canthus
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| Caption     = Front of left [[Biology:Eye|eye]] with eyelids separated to show medial canthus.
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The '''canthus''' ({{plural form}}: '''canthi''', '''palpebral commissures''') is either corner of the [[Biology:Eye|eye]] where the upper and lower [[Biology:Eyelid|eyelid]]s meet.<ref>{{DorlandsDict|two/000016591|canthus}}</ref> More specifically, the inner and outer canthi are, respectively, the medial and lateral ends/angles of the [[Medicine:Palpebral fissure|palpebral fissure]].

The '''bicanthal plane''' is the [[Transversal plane|transversal plane]] linking both canthi and defines the upper boundary of the midface.

==Etymology==
The word ''{{wikt-lang|la|canthus}}'' is the [[Social:Romanization of Greek|Latinized]] form of the [[Social:Ancient Greek|Ancient Greek]] {{wikt-lang|grc|κανθός}} (''{{grc-transl|κανθός}}''), meaning 'corner of the eye'.

==Population distribution==

The eyes of those of East Asian and some Southeast Asian people tend to have the inner canthus veiled by the epicanthus. In the [[Biology:Caucasian race|Caucasian]] or double eyelid, the inner corner tends to be exposed completely.<ref>Bongsik Kwon,  Anh H. Nguyen: [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4536067/ Reconsideration of the Epicanthus: Evolution of the Eyelid and the Devolutional Concept of Asian Blepharoplasty]  Semin Plast Surg. 2015 Aug; 29(3): 171–183. {{doi|10.1055/s-0035-1556849}}, {{PMC|4536067}}</ref>

==Commissures==
* The ''lateral palpebral [[Biology:Commissure|commissure]]'' (commissura palpebrarum lateralis; external canthus) is more acute than the medial, and the eyelids here lie in close contact with the bulb of the eye.
* The ''medial palpebral commissure'' (commissura palpebrarum medialis; internal canthus) is prolonged for a short distance toward the [[Medicine:Human nose|nose]], and the two eyelids are separated by a triangular space, the lacus lacrimalis.

==Surgery==
[[File:CuttingLateralCanthus.jpg|thumb|Cutting lateral canthus]]

Canthoplasty refers to a plastic surgery of the medial and/or lateral canthus. This technique is common in cosmetic procedures, as well as procedures that address eyelid function or malposition.<ref>{{Cite journal|last=Taban|first=Mehryar R.|date=2010|title=Aesthetic Lateral Canthoplasty|url=https://r7z9r7i7.stackpathcdn.com/wp-content/uploads/2014/08/AestheticLateralCanthoplasty.pdf|journal=Ophthalmic Plastic & Reconstructive Surgery|volume=26|issue=3|pages=190–194|doi=10.1097/IOP.0b013e3181baa23f|via=Stackpath}}</ref>

A canthotomy involves cutting the canthus, often performed to release excessive orbital pressure (i.e., from orbital hemorrhage or infection).<ref>{{cite book|title=Nurse Anesthesia |first1=John J. |last1=Nagelhout |first2=Karen |last2=Plaus |year=2009 |url=https://books.google.com/books?id=zfknhzaSOSAC |chapter=Chapter 40. Anesthesia For Ophthalmic Procedures |via=[[Google Books]] |access-date=2023-03-24 |page=[https://books.google.com/books?id=zfknhzaSOSAC&pg=PA963 963] |isbn=9780323081016 |publisher=Elsevier Health Sciences |quote=Canthotomy is a procedure performed to increase the orbital space by cutting the lateral canthus. This procedure reduces the orbital pressure that results from a retrobulbar hemorrhage.}}</ref>  

The two canthi of each eye (medial and lateral, that is, inner and outer) are represented in cephalometric analysis by the endocanthion and exocanthion landmarks (single points representing the point of each commissural angle).

==Pathology==
[[Biology:Telecanthus|Telecanthus]], or dystopia canthorum, is a lateral displacement of the inner canthi of the eyes, giving an appearance of a widened nasal bridge.<ref>[http://www.utmb.edu/otoref/grnds/genetic-hl-2004-0317/genetic-hl-2004-0317.doc Genetic Hearing Loss] {{Webarchive|url=https://web.archive.org/web/20130217173715/http://www.utmb.edu/otoref/grnds/Genetic-HL-2004-0317/Genetic-HL-2004-0317.doc |date=2013-02-17 }} from UTMB, Dept. of Otolaryngology, March 17, 2004. Resident physician: Jing Shen, faculty physician: Ronald W. Deskin, MD, series editors: Francis B. Quinn, Jr., MD and Matthew W. Ryan, MD.</ref> It is associated with [[Medicine:Waardenburg syndrome|Waardenburg syndrome]], which is due to mutation in PAX gene.<ref name="pmid16880590">{{cite journal |vauthors=Tagra S, Talwar AK, Walia RL, Sidhu P |title=Waardenburg syndrome |journal=Indian J Dermatol Venereol Leprol |volume=72 |issue=4 |pages=326 |year=2006 |pmid=16880590 |doi= 10.4103/0378-6323.26718|doi-access=free }}</ref>

==See also==
* [[Biology:Anatomy|Anatomy]]
* Biological morphology
* [[Biology:Commissure|Commissure]]
* [[Biology:Epicanthic fold|Epicanthic fold]]
* [[Biology:Fissure (anatomy)|Fissure (anatomy)]]
* [[Medicine:Lateral palpebral raphe|Lateral palpebral raphe]]

==References==
{{reflist}}

==External links==
* [https://web.archive.org/web/20070311130947/http://www.sheinman.com/Aanatomyp1.htm Diagram at sheinman.com]
* [https://web.archive.org/web/20170303122913/http://www.solobambini.com/measure_canthus.html Diagram at solobambini.com] (measure of [[Biology:Pupillary distance|Pupillary distance]])
{{Accessory organs of the eye}}

[[Category:Human eye anatomy]]

{{Sourceattribution|Canthus}}