The canthus (: canthi, palpebral commissures) is either corner of the

eye An eye is a sensory organ that allows an organism to perceive visual information. It detects light and converts it into electro-chemical impulses in neurons (neurones). It is part of an organism's visual system. In higher organisms, the ey ...

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. "Palpebral ...

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 Geometry (; ) is a branch of mathematics concerned with properties of space such as the distance, shape, size, and relative position of figures. Geometry is, along with arithmetic, one of the oldest branches of mathematics. A ...

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 classical antiquity, ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: Mycenaean Greek (), Greek ...

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

Population distribution

The

eyes An eye is a sensory organ that allows an organism to perceive visual information. It detects light and converts it into electro-chemical impulses in neurons (neurones). It is part of an organism's visual system. In higher organisms, the ey ...

East Asian East Asia is a geocultural region of Asia. It includes China, Japan, Mongolia, North Korea, South Korea, and Taiwan, plus two special administrative regions of China, Hong Kong and Macau. The economies of Economy of China, China, Economy of Ja ...

and some

Southeast Asian Southeast Asia is the geographical southeastern region of Asia, consisting of the regions that are situated south of China, east of the Indian subcontinent, and northwest of the Australian mainland, which is part of Oceania. Southeast Asia is ...

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 presence of "partial epicanthic folds" or "slight epic ...

. In the

Caucasian Caucasian may refer to: Common meanings *Anything from the Caucasus region or related to it ** Ethnic groups in the Caucasus ** ''Caucasian Exarchate'' (1917–1920), an ecclesiastical exarchate of the Russian Orthodox Church in the Caucasus re ...

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 wikt:abut#Verb, 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 at ...

'' (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 sensory organ and respiratory structure in vertebrates. It consists of a nasal cavity inside the head, and an external nose on the face. The external nose houses the nostrils, or nares, a pair of tubes providing airflow through the ...

, 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 Canthotomy (also called lateral canthotomy and canthotomy with cantholysis) is a surgical procedure where the lateral canthus, or corner, of the eye is cut to relieve the fluid pressure inside or behind the eye, known as intraocular pressure (IO ...

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 treatment ...

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 whol ...

, 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 part of the nose, where the nasal bones and surrounding soft tissues provide structural support. While commonly discussed in human anatomy, nasal bridges exist in various forms across many vertebrates, particularl ...

.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 Heterochromia iridum, one blue eye and one brown ey ...

, which is due to mutation in PAX gene.

References

External links

Diagram at sheinman.com

(measure of

Pupillary distance Pupillary distance (PD), more correctly known as interpupillary distance (IPD) is the distance in millimeters between the centers of each pupil. Interpupillary Distance Classifications Distance PD is the separation between the visual axes of the ...

) {{Accessory organs of the eye Human eye anatomy