The ophthalmic artery is the first branch of the internal carotid artery

Internal carotid artery

In human anatomy, the internal carotid arteries are two major arteries, one on each side of the head and neck. They arise from the common carotid arteries where these bifurcate into the internal and external carotid artery, and they supply the brain....

 distal to the cavernous sinus

Cavernous sinus

The cavernous sinus , within the human head, is a large collection of thin-walled veins creating a cavity bordered by the temporal bone of the skull and the sphenoid bone, lateral to the sella turcica.-Contents:...

. Branches of the OA supply all the structures in the orbit as well as some structures in the nose, face and meninges. Occlusion of the OA or its branches can produce sight-threatening conditions.

Course from internal carotid to orbit

The OA emerges from the internal carotid artery usually just after the latter emerges from the cavernous sinus although in some cases, the OA branches just before the internal carotid exits the cavernous sinus. The OA arises from the internal carotid along the medial side of the anterior clinoid process

Anterior clinoid process

In the sphenoid bone, the posterior border, smooth and rounded, is received into the lateral fissure of the brain; the medial end of this border forms the anterior clinoid process, which gives attachment to the tentorium cerebelli; it is sometimes joined to the middle clinoid process by a spicule...

 and runs anteriorly passing through the optic canal with and inferolaterally to the optic nerve

Optic nerve

The optic nerve, also called cranial nerve 2, transmits visual information from the retina to the brain. Derived from the embryonic retinal ganglion cell, a diverticulum located in the diencephalon, the optic nerve doesn't regenerate after transection.-Anatomy:The optic nerve is the second of...

. Here, it should be noted that the ophthalmic artery can also pass superiorly to the optic nerve in a minority of cases . In the posterior third of the cone of the orbit, the ophthalmic artery turns sharply medially to run along the medial wall of the orbit.

Central retinal artery

The central retinal artery

Central retinal artery

The central retinal artery branches off the ophthalmic artery, running inferior to the optic nerve within its dural sheath to the eyeball.- Course :...

 is the first, and one of the smaller branches of the OA and runs in the dura mater inferior to the optic nerve. About 12.5mm (0.5 inches) posterior to the globe, the central retinal artery turns superiorly and penetrates the optic nerve continuing along the center of the optic nerve entering the eye to supply the inner retinal layers.

Lacrimal artery

The next branch of the OA is the lacrimal artery

Lacrimal artery

The lacrimal artery arises close to the optic foramen, and is one of the largest branches derived from the ophthalmic artery: not infrequently it is given off before the artery enters the orbit....

, one of the largest, arises just as the OA enters the orbit and runs along the superior edge of the lateral rectus muscle

Lateral rectus muscle

The lateral rectus muscle is a muscle in the orbit. It is one of six extraocular muscles that control the movements of the eye and the only muscle innervated by the abducens nerve, cranial nerve VI....

 to supply the lacrimal gland

Lacrimal gland

The lacrimal glands are paired almond-shaped glands, one for each eye, that secrete the aqueous layer of the tear film. They are situated in the upper, outer portion of each orbit, in the lacrimal fossa of the orbit formed by the frontal bone. Inflammation of the lacrimal glands is called...

, eyelids and conjunctiva

Conjunctiva

The conjunctiva covers the sclera and lines the inside of the eyelids. It is composed of rare stratified columnar epithelium.-Function:...

.

Posterior ciliary arteries

The OA then turns medially giving off 1 to 5 posterior ciliary arteries (PCA) that subsequently branch into the long and short posterior ciliary arteries (LPCA and SPCA respectively) which perforate the sclera posteriorly in the vicinity of the optic nerve and macula to supply the posterior uveal tract. In the past, anatomists made little distinction between the posterior ciliary arteries and the short and long posterior ciliary arteries often using the terms synonymously. However, recent work by Hayreh has shown that there is both an anatomic and clinically useful distinction. The PCAs arise directly from the OA and are end arteries which is to say no PCA or any of its branches anastomose with any other artery. Consequently, sudden occlusion of any PCA will produce an infarct in the region of the choroid supplied by that particular PCA. Occlusion of a short or long PCA will produce a smaller choroidal infarct within the larger area supplied by the specific parent PCA.

Muscular branches

The OA continues medially the superior and inferior muscular branches arise either from the OA or a single trunk from the OA subsequently divides into superior and inferior branches to supply the extraocular muscles.

Supraorbital artery

The supraorbital artery branches from the OA as it passes over the optic nerve. The supraorbital artery passes anteriorly along the medial border of the superior rectus and levator palpebrae and through the supraorbital foramen to supply muscles and skin of the forehead.

Ethmoidal arteries

After reaching the medial wall of the orbit, the OA again turns anteriorly. The posterior ethmoidal artery

Posterior ethmoidal artery

The posterior ethmoidal artery is an artery of the head which supplies the nasal septum. It is smaller than the anterior ethmoidal artery.-Course:...

 enters the nose via the posterior ethmoidal canal and supplies the posterior ethmoidal sinuses and enters the skull to supply the meninges.

The OA continues anteriorly, giving off the anterior ethmoidal artery

Anterior ethmoidal artery

The anterior ethmoidal artery, also anterior ethmoid artery is an artery of the head.-Course:Once branching from the ophthalmic artery, it accompanies the nasociliary nerve through the anterior ethmoidal canal to supply the anterior and middle ethmoidal cells, frontal sinus, and anterosuperior...

 which enters the nose after traversing the anterior ethmoidal canal and supplies the anterior and middle ethmoidal sinuses as well as the frontal sinus and also enters the cranium to supply the meninges.

Medial palpebral arteries

The OA continues anteriorly to the trochlea where the medial palpebral arteries (superior and inferior) arise and supply the eyelids.

Terminal branches

The OA terminates in two branches, the supratrochlear (or frontal) artery and the dorsal nasal artery. Both exit the orbit medially to supply the forehead and nose.

Classification of ophthalmic artery branches

Because of the obvious importance of the ocular globe branches of the ophthalmic artery are often subdivided into two groups: those that supply the eyeball (ocular group) and those that supply nonocular orbital structures (orbital group). http://education.yahoo.com/reference/gray/subjects/subject/146

Orbital group

The orbital group, distributing vessels to the orbit and surrounding parts, includes:

• Lacrimal artery
  Lacrimal artery
  The lacrimal artery arises close to the optic foramen, and is one of the largest branches derived from the ophthalmic artery: not infrequently it is given off before the artery enters the orbit....
  
  
• Supraorbital artery
• Posterior ethmoidal artery
  Posterior ethmoidal artery
  The posterior ethmoidal artery is an artery of the head which supplies the nasal septum. It is smaller than the anterior ethmoidal artery.-Course:...
  
  
• Anterior ethmoidal artery
  Anterior ethmoidal artery
  The anterior ethmoidal artery, also anterior ethmoid artery is an artery of the head.-Course:Once branching from the ophthalmic artery, it accompanies the nasociliary nerve through the anterior ethmoidal canal to supply the anterior and middle ethmoidal cells, frontal sinus, and anterosuperior...
  
  
• Internal palpebral artery
• Frontal artery, also called the Supratrochlear artery
  Supratrochlear artery
  The supratrochlear artery , one of the terminal branches of the ophthalmic artery, branches off where the ophthalmic travels posterior to the trochlea.-Course:...
  
  
• Dorsal nasal artery
  Dorsal nasal artery
  The dorsal nasal artery is an artery of the head. It is one of the two terminal branches of the ophthalmic artery.-Course:...
  
  

Ocular group

The ocular group, distributing vessels to the eye and its muscles, includes:

• Posterior ciliary arteries
• Long posterior ciliary arteries
  Long posterior ciliary arteries
  The long posterior ciliary arteries are arteries of the head arising, together with the other ciliary arteries, from the ophtalmic artery. There are two in each eye.-Course:...
  
  
• Short posterior ciliary arteries
  Short posterior ciliary arteries
  The short posterior ciliary arteries from six to twelve in number, arise from the ophthalmic as it crosses the optic nerve.-Course and target:...
  
  
• Anterior ciliary artery
• Central retinal artery
• Superior muscular artery
• Inferior muscular artery

Structures supplied by ophthalmic artery

Branches of the ophthalmic artery supply:

• Frontal belly of the occipitofrontalis muscle
  Occipitofrontalis muscle
  The occipitofrontalis or epicranius is a muscle which covers parts of the skull. It consists of two parts or bellies: The occipital belly, near the occipital bone, and the frontal belly, near the frontal bone....
  
  
• Inferior oblique muscle
  Inferior oblique muscle
  The Obliquus oculi inferior is a thin, narrow muscle placed near the anterior margin of the floor of the orbit.-Action:Its actions are lateral rotation, elevation and abduction of the eye....
  
  
• Inferior rectus muscle
  Inferior rectus muscle
  The inferior rectus muscle is a muscle in the orbit.-Actions:It depresses, adducts, and helps extort the eye.The inferior rectus muscle is the only muscle that is capable of depressing the pupil when it is in a fully abducted position....
  
  
• Lacrimal gland
  Lacrimal gland
  The lacrimal glands are paired almond-shaped glands, one for each eye, that secrete the aqueous layer of the tear film. They are situated in the upper, outer portion of each orbit, in the lacrimal fossa of the orbit formed by the frontal bone. Inflammation of the lacrimal glands is called...
  
  
• Lateral rectus muscle
  Lateral rectus muscle
  The lateral rectus muscle is a muscle in the orbit. It is one of six extraocular muscles that control the movements of the eye and the only muscle innervated by the abducens nerve, cranial nerve VI....
  
  
• Levator palpebrae superioris muscle
  Levator palpebrae superioris muscle
  The levator palpebrae superioris is the muscle in the orbit that elevates the superior eyelid.-Structure:...
  
  
• Medial rectus muscle
  Medial rectus muscle
  The medial rectus muscle is a muscle in the orbit.As with most of the muscles of the orbit, it is innervated by the inferior division of the oculomotor nerve ....
  
  
• Nasalis muscle
  Nasalis muscle
  The nasalis is a sphincter-like muscle of the nose whose function is to compress the nasal cartilage.It consists of two parts, transverse and alar:...
  
  
• Procerus muscle
  Procerus muscle
  The Procerus is a small pyramidal slip of muscle deep to the superior orbital nerve, artery and vein.-Origin and insertion:It arises by tendinous fibers from the fascia covering the lower part of the nasal bone and upper part of the lateral nasal cartilage....
  
  
• Superior oblique muscle
  Superior oblique muscle
  For the abdominal muscle see: Abdominal external oblique muscleThe superior oblique muscle, or obliquus oculi superior, is a fusiform muscle originating in the upper, medial side of the orbit which abducts, depresses and internally rotates the eye...
  
  
• Superior rectus muscle
  Superior rectus muscle
  The superior rectus muscle is a muscle in the orbit. It is one of the extraocular muscles. It is innervated by the superior division of the oculomotor nerve...
  
  

Occlusion

Severe occlusion of the ophthalmic artery causes ocular ischemic syndrome

Ocular ischemic syndrome

Ocular ischemic syndrome is the constellation of ocular signs and symptoms secondary to severe, chronic arterial hypoperfusion to the eye. Amaurosis fugax is a form of acute vision loss caused by reduced blood flow to the eye that may be a warning sign of an impending stroke...

. As with central retinal artery

Central retinal artery

The central retinal artery branches off the ophthalmic artery, running inferior to the optic nerve within its dural sheath to the eyeball.- Course :...

 occlusions, ophthalmic artery occlusions may result from systemic cardiovascular disease

Cardiovascular disease

Heart disease or cardiovascular disease are the class of diseases that involve the heart or blood vessels . While the term technically refers to any disease that affects the cardiovascular system , it is usually used to refer to those related to atherosclerosis...

s; however, a cherry-red spot

Cherry-red spot

A cherry-red spot is a finding in the macula of the eye in a variety of lipid storage disorders and in central retinal artery occlusion.It describes the appearance of a small circular choroid shape as seen through the fovea centralis....

 is typically absent and the vision is usually worse. Amaurosis fugax

Amaurosis fugax

Amaurosis fugax is a transient monocular visual loss.-Pathophysiology and etiology:...

 is a temporary loss of vision that occurs in two conditions which cause a temporary reduction in ophthalmic artery pressure: orthostatic hypotension

Orthostatic hypotension

Orthostatic hypotension, also known as postural hypotension, orthostasis, and colloquially as head rush or dizzy spell, is a form of hypotension in which a person's blood pressure suddenly falls when the person stands up or stretches. The decrease is typically greater than 20/10 mm Hg, and may be...

 and positive acceleration.

Even complete occlusion of the ophthalmic artery may possibly leave the eye without symptoms, probably because of circulatory anastomoses

Circulatory anastomosis

A circulatory anastomosis is a connection between two blood vessels, such as between arteries , between veins or between an artery and a vein . Anastomoses between arteries and between veins result in a multitude of arteries and veins, respectively, serving the same volume of tissue...