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 eye ...

s meet. 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 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 angles. Theorems Transversal plane theorem for lines: Lines that intersect a transversal plane ar ...

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 pe ...

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

Population distribution

The eyes 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 ...

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

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

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 passe ...

, 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, or dystopia canthorum, is a lateral displacement of the inner canthi of the eyes, giving an appearance of a widened nasal bridge.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, which is due to mutation in PAX gene.

References

External links

Diagram at sheinman.com

(measure of Pupillary distance) Human eye anatomy {{eye-stub