Canthus

Canthus (pl. canthi, palpebral commissures) is either corner of the eye where the upper and lower eyelids meet.

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

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, 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.

A canthotomy involves cutting the canthus, often performed to release excessive orbital pressure (i.e., from orbital hemorrhage or infection).

Pathology

"Dystopia canthorum" is associated with Waardenburg syndrome.