The canthus (pl. canthi, palpebral commissures) is either corner of the eye where the upper and lower

eyelid An eyelid 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. The human eyel ...

s meet. More specifically, the inner and outer canthi are, respectively, the medial and lateral ends/angles of the

palpebral fissure The palpebral fissure is the elliptic space between the medial and lateral canthi of the two open eyelids. In simple terms, it is the opening between the eyelids. In adult humans, this measures about 10 mm vertically and 30 mm horizontally. Va ...

. The bicanthal plane is the

transversal plane In geometry, a transversal plane is a plane that intersects (not contains) two or more lines or planes. A transversal plane may also form dihedral angle A dihedral angle is the angle between two intersecting planes or half-planes. In chem ...

linking both canthi and defines the upper boundary of the midface.

Etymology

The word ' is the Latinized form of the

Ancient Greek Ancient Greek includes the forms of the Greek language used in ancient Greece and the ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: Mycenaean Greek (), Dark Ages (), the Archaic peri ...

('), meaning 'corner of the eye'.

Population distribution

The

eyes Eyes are organs of the visual system. They provide living organisms with vision, the ability to receive and process visual detail, as well as enabling several photo response functions that are independent of vision. Eyes detect light and conve ...

of those of

East Asian East Asia is the eastern region of Asia, which is defined in both geographical and ethno-cultural terms. The modern states of East Asia include China, Japan, Mongolia, North Korea, South Korea, and Taiwan. China, North Korea, South Korea a ...

and some

Southeast Asian Southeast Asia, also spelled South East Asia and South-East Asia, and also known as Southeastern Asia, South-eastern Asia or SEA, is the geographical south-eastern region of Asia, consisting of the regions that are situated south of mainland ...

people tend to have the inner canthus veiled by the

epicanthus 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 ...

. In the

Caucasian Caucasian may refer to: Anthropology *Anything from the Caucasus region ** ** ** ''Caucasian Exarchate'' (1917–1920), an ecclesiastical exarchate of the Russian Orthodox Church in the Caucasus region * * * Languages * Northwest Caucasian l ...

or double eyelid, the inner corner tends to be exposed completely.

Commissures

* The ''lateral palpebral

commissure A commissure () is the location at which two objects abut or are joined. The term is used especially in the fields of anatomy and biology. * The most common usage of the term refers to the brain's commissures, of which there are five. Such a commi ...

'' (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

nose A nose is a protuberance in vertebrates that houses the nostrils, or nares, which receive and expel air for respiration alongside the mouth. Behind the nose are the olfactory mucosa and the sinuses. Behind the nasal cavity, air next passes th ...

, and the two eyelids are separated by a triangular space, the lacus lacrimalis.

Surgery

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. A canthotomy involves cutting the canthus, often performed to release excessive orbital pressure (i.e., from orbital hemorrhage or infection). The two canthi of each eye (medial and lateral, that is, inner and outer) are represented in

cephalometric analysis Cephalometric analysis is the clinical application of cephalometry. It is analysis of the dental and skeletal relationships of a human skull. It is frequently used by dentists, orthodontists, and oral and maxillofacial surgeons as a treatmen ...

by the endocanthion and exocanthion landmarks (single points representing the point of each commissural angle).

Pathology

Telecanthus Telecanthus, or dystopia canthorum, refers to increased distance between the inner corners of the eyelids (medial canthi), while the inter-pupillary distance is normal. This is in contrast to hypertelorism, in which the distance between the w ...

, or dystopia canthorum, is a lateral displacement of the inner canthi of the eyes, giving an appearance of a widened

nasal bridge The nasal bridge is the upper, bony part of the human nose, which overlies the nasal bones. Association with epicanthic folds Low-rooted nasal bridges are closely associated with epicanthic folds. A lower nasal bridge is more likely to cause an ...

.Genetic Hearing Loss
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. It is associated with

Waardenburg syndrome Waardenburg syndrome is a group of rare genetic conditions characterised by at least some degree of congenital hearing loss and pigmentation deficiencies, which can include bright blue eyes (or one blue eye and one brown eye), a white foreloc ...

, which is due to mutation in PAX gene.

References

External links

Diagram at sheinman.com

(measure of

Pupillary distance Pupillary distance (PD) or interpupillary distance (IPD) is the distance measured in millimeters between the centers of the pupils of the eyes. This measurement is different from person to person and also depends on whether they are looking at near ...

) Human eye anatomy {{eye-stub