| Canthus | |
|---|---|
 Front of left eye with eyelids separated to show medial canthus. | |
| Identifiers | |
| FMA | 59222 |
| Anatomical terminology | |
The canthus (pl.: canthi, palpebral commissures) is either corner of the eye where the upper and lower eyelids meet. [1] 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.
The word canthus is the Latinized form of the Ancient Greek κανθός (kanthós), meaning 'corner of the eye'.
The eyes of East Asian and some Southeast Asian 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. [2]
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. [3]
A canthotomy involves cutting the canthus, often performed to release excessive orbital pressure (i.e., from orbital hemorrhage or infection). [4]
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).
Telecanthus, or dystopia canthorum, is a lateral displacement of the inner canthi of the eyes, giving an appearance of a widened nasal bridge. [5] It is associated with Waardenburg syndrome, which is due to mutation in PAX gene. [6]
In anatomy, the orbit is the cavity or socket/hole of the skull in which the eye and its appendages are situated. "Orbit" can refer to the bony socket, or it can also be used to imply the contents. In the adult human, the volume of the orbit is 30 millilitres, of which the eye occupies 6.5 ml. The orbital contents comprise the eye, the orbital and retrobulbar fascia, extraocular muscles, cranial nerves II, III, IV, V, and VI, blood vessels, fat, the lacrimal gland with its sac and duct, the eyelids, medial and lateral palpebral ligaments, cheek ligaments, the suspensory ligament, septum, ciliary ganglion and short ciliary nerves.
Eye surgery, also known as ophthalmic surgery or ocular surgery, is surgery performed on the eye or its adnexa. Eye surgery is part of ophthalmology and is performed by an ophthalmologist or eye surgeon. The eye is a fragile organ, and requires due care before, during, and after a surgical procedure to minimize or prevent further damage. An eye surgeon is responsible for selecting the appropriate surgical procedure for the patient, and for taking the necessary safety precautions. Mentions of eye surgery can be found in several ancient texts dating back as early as 1800 BC, with cataract treatment starting in the fifth century BC. It continues to be a widely practiced class of surgery, with various techniques having been developed for treating eye problems.
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" means relating to the eyelids. Its key function is to regularly spread the tears and other secretions on the eye surface to keep it moist, since the cornea must be continuously moist. They keep the eyes from drying out when asleep. Moreover, the blink reflex protects the eye from foreign bodies. A set of specialized hairs known as lashes grow from the upper and lower eyelid margins to further protect the eye from dust and debris.
The lacrimal glands are paired exocrine glands, one for each eye, found in most terrestrial vertebrates and some marine mammals, that secrete the aqueous layer of the tear film. In humans, they are situated in the upper lateral region of each orbit, in the lacrimal fossa of the orbit formed by the frontal bone. Inflammation of the lacrimal glands is called dacryoadenitis. The lacrimal gland produces tears which are secreted by the lacrimal ducts, and flow over the ocular surface, and then into canals that connect to the lacrimal sac. From that sac, the tears drain through the lacrimal duct into the nose.
The ophthalmic artery (OA) is an artery of the head. It is the first branch of the internal carotid artery distal to the cavernous sinus. Branches of the ophthalmic artery supply all the structures in the orbit around the eye, as well as some structures in the nose, face, and meninges. Occlusion of the ophthalmic artery or its branches can produce sight-threatening conditions.
The orbicularis oculi is a muscle in the face that closes the eyelids. It arises from the nasal part of the frontal bone, from the frontal process of the maxilla in front of the lacrimal groove, and from the anterior surface and borders of a short fibrous band, the medial palpebral ligament.
The tarsi or tarsal plates are two comparatively thick, elongated plates of dense connective tissue, about 10 mm (0.39 in) in length for the upper eyelid and 5 mm for the lower eyelid; one is found in each eyelid, and contributes to its form and support. They are located directly above the lid margins. The tarsus has a lower and upper part making up the palpebrae.
The lacrimal nerve is the smallest of the three main branches of the ophthalmic nerve (CN V1) (itself a branch of the trigeminal nerve (CN V)).
The angular vein is a vein of the face. It is the upper part of the facial vein, above its junction with the superior labial vein. It is formed by the junction of the supratrochlear vein and supraorbital vein, and joins with the superior labial vein. It drains the medial canthus, and parts of the nose and the upper lip. It can be a route of spread of infection from the danger triangle of the face to the cavernous sinus.
The lacrimal artery is an artery of the orbit. It is a branch of the ophthalmic artery. It accompanies the lacrimal nerve along the upper border of the lateral rectus muscle, travelling forward to reach the lacrimal gland. It supplies the lacrimal gland, two rectus muscles of the eye, the eyelids, and the conjunctiva.
The infraorbital nerve is a branch of the maxillary nerve. It arises in the pterygopalatine fossa. It passes through the inferior orbital fissure to enter the orbit. It travels through the orbit, then enters and traverses the infraorbital canal, exiting the canal at the infraorbital foramen to reach the face. It provides sensory innervation to the skin and mucous membranes around the middle of the face.
The angular artery is an artery of the face. It is the terminal part of the facial artery. It ascends to the medial angle of the eye's orbit. It is accompanied by the angular vein. It ends by anastomosing with the dorsal nasal branch of the ophthalmic artery. It supplies the lacrimal sac, the orbicularis oculi muscle, and the outer side of the nose.
The medial palpebral arteries are arteries of the head that contribute arterial blood supply to the eyelids. They are derived from the ophthalmic artery; a single medial palpebral artery issues from the ophthalmic artery before splitting into a superior and an inferior medial palpebral artery, each supplying one eyelid.
In anatomy, the orbital septum is a membranous sheet that acts as the anterior (frontal) boundary of the orbit. It extends from the orbital rims to the eyelids. It forms the fibrous portion of the eyelids.
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.
Oculoplastics, or oculoplastic surgery, includes a wide variety of surgical procedures that deal with the orbit, eyelids, tear ducts, and the face. It also deals with the reconstruction of the eye and associated structures.
Blepharophimosis is a congenital anomaly in which the eyelids are underdeveloped such that they cannot open as far as usual and permanently cover part of the eyes. Both the vertical and horizontal palpebral fissures are shortened; the eyes also appear spaced more widely apart as a result, known as telecanthus.
The lateral palpebral raphe is a ligamentous band near the eye. Its existence is contentious, and many sources describe it as the continuation of nearby muscles. It is formed from the lateral ends of the orbicularis oculi muscle. It connects the orbicularis oculi muscle, the frontosphenoidal process of the zygomatic bone, and the tarsi of the eyelids.
Telecanthus, or dystopia canthorum, refers to increased distance between the inner corners of the eyelids, while the inter-pupillary distance is normal. This is in contrast to hypertelorism, in which the distance between the whole eyes is increased. Telecanthus and hypertelorism are each associated with multiple congenital disorders.
Canthotomy 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 (IOC). The procedure is typically done in emergency situations when the intraocular pressure becomes too high, which can damage the optic nerve and lead to blindness if left untreated.
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.
