Introduction
Also known as the second cranial nerve, or CN II, the optic nerve is the second of twelve cranial nerves. Although located at the back of the eye, the optic nerve is considered a part of the central nervous system due to its role in visual integration and function. The optic nerve transfers visual information from the retina to the vision centers of the brain via electrical impulses. Made of about 1.7 million retinal ganglion cell axons, or nerve cells, the optic nerve encompasses the first portion of the visual pathway: from the retina to the optic chiasm.
Dimensions
The optic nerve itself is a cylindrical structure. Approximately 50mm in length, it can be divided into 4 main parts: intraocular (1mm of the optic nerve head), …show more content…
Derived entirely from branches of the ophthalmic artery, the arterial supply of the anterior optic nerve is supplied via 1 to 5 posterior ciliary arteries (cite). Typically, between 2 and 4 posterior ciliary arteries course anteriorly before dividing into 10–20 short posterior ciliary arteries prior to entering the posterior globe (Remington, 204). Some short posterior ciliary arteries course, without branching, through the sclera directly into the choroid; others divide within the sclera to provide branches to both the choroid and the optic nerve (cite ). These vessels also anastomose around the optic nerve forming the circle of Zinn-Haller, which supplies both the prelaminar and laminar regions of the eye (cite). Another posterior orbital branch of the ophthalmic artery, the central retinal artery penetrates the optic nerve approximately 10–15 mm behind the globe (cite). The central retinal artery has few if any intraneural branches, which may anastomose with the pial system to help supply the laminar region (cite). Within the central portion of the optic nerve, the central retinal artery courses adjacent to the central retinal vein. Venous drainage of the optic nerve is almost exclusively via the central retinal vein directly or indirectly. Any issues with supply or drainage of these vessels can damage the optic nerve and overall
Also known as the second cranial nerve, or CN II, the optic nerve is the second of twelve cranial nerves. Although located at the back of the eye, the optic nerve is considered a part of the central nervous system due to its role in visual integration and function. The optic nerve transfers visual information from the retina to the vision centers of the brain via electrical impulses. Made of about 1.7 million retinal ganglion cell axons, or nerve cells, the optic nerve encompasses the first portion of the visual pathway: from the retina to the optic chiasm.
Dimensions
The optic nerve itself is a cylindrical structure. Approximately 50mm in length, it can be divided into 4 main parts: intraocular (1mm of the optic nerve head), …show more content…
Derived entirely from branches of the ophthalmic artery, the arterial supply of the anterior optic nerve is supplied via 1 to 5 posterior ciliary arteries (cite). Typically, between 2 and 4 posterior ciliary arteries course anteriorly before dividing into 10–20 short posterior ciliary arteries prior to entering the posterior globe (Remington, 204). Some short posterior ciliary arteries course, without branching, through the sclera directly into the choroid; others divide within the sclera to provide branches to both the choroid and the optic nerve (cite ). These vessels also anastomose around the optic nerve forming the circle of Zinn-Haller, which supplies both the prelaminar and laminar regions of the eye (cite). Another posterior orbital branch of the ophthalmic artery, the central retinal artery penetrates the optic nerve approximately 10–15 mm behind the globe (cite). The central retinal artery has few if any intraneural branches, which may anastomose with the pial system to help supply the laminar region (cite). Within the central portion of the optic nerve, the central retinal artery courses adjacent to the central retinal vein. Venous drainage of the optic nerve is almost exclusively via the central retinal vein directly or indirectly. Any issues with supply or drainage of these vessels can damage the optic nerve and overall