The central retinal artery (retinal artery) branches off the

ophthalmic artery 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 st ...

, running inferior to the

optic nerve In neuroanatomy, the optic nerve, also known as the second cranial nerve, cranial nerve II, or simply CN II, is a paired cranial nerve that transmits visual system, visual information from the retina to the brain. In humans, the optic nerve i ...

within its dural sheath to the

eyeball Eyes are organs of the visual system. They provide living organisms with vision, the ability to receive and process visual detail, as well as enabling several photo response functions that are independent of vision. Eyes detect light and conve ...

Structure

The central retinal artery pierces the eyeball close to the optic nerve, sending branches over the internal surface of the

retina The retina (from la, rete "net") is the innermost, light-sensitive layer of tissue of the eye of most vertebrates and some molluscs. The optics of the eye create a focused two-dimensional image of the visual world on the retina, which then ...

, and these terminal branches are the only blood supply to the larger part of it. The central part of the retina where the light rays are focused after passing through the

pupil The pupil is a black hole located in the center of the iris of the eye that allows light to strike the retina.Cassin, B. and Solomon, S. (1990) ''Dictionary of Eye Terminology''. Gainesville, Florida: Triad Publishing Company. It appears black ...

and the

lens A lens is a transmissive optical device which focuses or disperses a light beam by means of refraction. A simple lens consists of a single piece of transparent material, while a compound lens consists of several simple lenses (''elements''), ...

is a circular area called the

macula The macula (/ˈmakjʊlə/) or macula lutea is an oval-shaped pigmented area in the center of the retina of the human eye and in other animals. The macula in humans has a diameter of around and is subdivided into the umbo, foveola, foveal avas ...

. The center of this circular area is the

fovea Fovea () (Latin for "pit"; plural foveae ) is a term in anatomy. It refers to a pit or depression in a structure. Human anatomy *Fovea centralis of the retina * Fovea buccalis or Dimple * Fovea of the femoral head * Trochlear fovea of the fr ...

. The fovea and a small area surrounding it are not supplied by the central retinal artery or its branches, but instead by the

choroid The choroid, also known as the choroidea or choroid coat, is a part of the uvea, the vascular layer of the eye, and contains connective tissues, and lies between the retina and the sclera. The human choroid is thickest at the far extreme rear ...

. The central retinal artery is approximately 160 micrometres in diameter.

Variation

In some cases - approximately 20% of the population - there is a branch of the ciliary circulation called the cilio-retinal artery which supplies the retina between the macula and the optic nerve, including the nerve fibers from the foveal photoreceptors. If this artery is present, the central vision will be preserved even in case of central retinal artery occlusion (CRAO).

Development

The central retinal artery is formed from the proximal part of the

hyaloid artery The hyaloid artery is a branch of the ophthalmic artery, which is itself a branch of the internal carotid artery. It is contained within the optic stalk of the eye and extends from the optic disc through the vitreous humor to the lens. Usually f ...

after atrophy of its distal part has formed the

hyaloid canal Hyaloid canal (Cloquet's canal and Stilling's canal) is a small transparent canal running through the vitreous body from the optic nerve disc to the lens. It is formed by an invagination of the hyaloid membrane, which encloses the vitreous body ...

Function

The central retinal artery supplies blood to all the nerve fibers that form the optic nerve, which carries the visual information to the

lateral geniculate nucleus In neuroanatomy, the lateral geniculate nucleus (LGN; also called the lateral geniculate body or lateral geniculate complex) is a structure in the thalamus and a key component of the mammalian visual pathway. It is a small, ovoid, ventral projec ...

of the thalamus, including those that reach over the fovea. Its blood flow can be revealed by

fluorescein angiography Fluorescein angiography (FA), fluorescent angiography (FAG), or fundus fluorescein angiography (FFA) is a technique for examining the circulation of the retina and choroid (parts of the fundus) using a fluorescent dye and a specialized camera. S ...

laser Doppler imaging Laser Doppler imaging (LDI) is an imaging method that uses a laser beam to scan live tissue. When the laser light reaches the tissue, the moving blood cells generate doppler components in the reflected ( backscattered) light. The light that comes ...

.Puyo, L., M. Paques, M. Fink, J-A. Sahel, and M. Atlan. "In vivo laser Doppler holography of the human retina." Biomedical optics express 9, no. 9 (2018): 4113-4129.

Clinical significance

Thus if the central retinal artery gets occluded, there is complete loss of vision in that eye even though the fovea is not affected. The entire retina (with the exception of the fovea) becomes pale and swollen and opaque while the central fovea still appears reddish (this is because the choroid color shows through). This is the basis of the famous "Cherry red spot" seen on examination of the retina on funduscopy of a

central retinal artery occlusion Central retinal artery occlusion (CRAO) is a disease of the eye where the flow of blood through the central retinal artery is blocked (occluded). There are several different causes of this occlusion; the most common is carotid artery atheroscler ...

(CRAO). However it should be remembered that the Cilio retinal artery itself is a branch of the Short Posterior Ciliary Arteries which is derived from the Ophthalmic Artery. Therefore, its possible for the cilio retinal artery itself to occlude causing significant visual loss in the perfused macula region (surrounding visual field will remain intact).

Other animals

In dogs, it is the continuation of the long ciliary artery.

Additional images

Image:Gray879.png, Interior of posterior half of bulb of left eye. The veins are darker in appearance than the arteries. (Central retinal artery visible but not labeled). Image:Gray869.png, Horizontal section of the eyeball. Image:Gray880.png, The terminal portion of the optic nerve and its entrance into the eyeball, in horizontal section. Image:Eyevessels 001.jpg, Eye vessels

References

External links

Diagram at suncoastretina.com
* ("Retinal artery occlusion") {{Authority control Arteries of the head and neck