View source for Canthus

{{Short description|Corner of the eye where the upper and lower eyelids meet}}
{{Use dmy dates|date=March 2023}}
{{Other uses}}
{{Infobox anatomy
| Name        = Canthus
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| Image       = Gray892.png
| Caption     = Front of left eye with eyelids separated to show medial canthus.
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| Precursor   =
| System      =
| Artery      =
| Vein        =
| Nerve       =
| Lymph       =
}}
The '''canthus''' ({{plural form}}: '''canthi''', '''palpebral commissures''') is either corner of the [[eye]] where the upper and lower [[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 [[palpebral fissure]].

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

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

==Population distribution==

The [[Human eye|eyes]] of [[East Asian]] and some [[Southeast Asian]] people tend to have the inner canthus veiled by the [[epicanthus]]. In the [[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 [[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 [[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|pmid=20489545 |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==
[[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 [[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==
{{Portal|Anatomy|Animals|Medicine|Biology|Science}}
* [[Anatomy]]
* [[Biological morphology]]
* [[Commissure]]
* [[Epicanthic fold]]
* [[Fissure (anatomy)]]
* [[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 [[Pupillary distance]])
{{Accessory organs of the eye}}

[[Category:Human eye anatomy]]