Optic chiasm
Anatomy [edit]. The optic nerve is a cable connection that transmits images from the retina to the brain. It consists of over one million retinal ganglion cell axons. The optic nerve head, or optic disc is the anterior end of the nerve that is in the eye and hence is visible with an ophthalmoscope. It is located nasally and slightly inferior to the macula of the eye. Optic disc drusen (ODD) or optic nerve head drusen (ONHD) are globules of mucoproteins and mucopolysaccharides that progressively calcify in the optic disc. They are thought to be the remnants of the axonal transport system of degenerated retinal ganglion cells. blind spot. The beginning of the optic nerve in the retina is called the optic nerve head or optic disc. Since there are no photoreceptors (cones and rods) in the optic nerve head, this area of the retina cannot respond to light stimulation. As a result, it is known as the blind spot, and everybody has one in each eye. The optic nerve (also known as cranial nerve II) is a continuation of the axons of the ganglion cells in the retina. There are approximately 1.1 million nerve cells in each optic nerve. The optic nerve, which acts like a cable connecting the eye with the brain, actually is more like brain tissue than it is nerve tissue. The second most significant risk factor for the development of chronic open-angle glaucoma is the size of the central cup cupping of the optic nerve head. Cupped disc. The cupping of the optic nerve means the size of the depression in the middle of the nerve when viewed from the front of the eye. When there is damage to the optic nerve, the cupping increases. When a person is shown to have large optic nerve cups, it could be an indicator of damage unless it can be determined that the cup size is considered normal for that individual. The end of the optic nerve, where all the individual nerves from each of the cells in your retina come together, is known as the optic disc. Your optic disc is visible as a small circular area of your retina which can be seen by the ophthalmologist (eye specialist) or optician when they look into your eye. From your optic disc, the nerve fibres travel together in bundles, forming your optic nerve, to your brain. In humans, the optic nerve extends from the optic disc to the optic chiasm and continues as the optic tract to the lateral geniculate nucleus, pretectal nuclei, and superior colliculus. The optic nerve is ensheathed in all three meningeal layers (dura, arachnoid, and pia mater) rather than the epineurium, perineurium, and endoneurium found in peripheral nerves. Through periodic photographs of the optic nerve, the ratio of the cup to the disc can be monitored. This helps your eye doctor determine a baseline and to see whether or not damage is still occurring to the nerve fibers with current treatment and/or if treatment should be modified. When there is damage to the optic nerve, the cupping increases. When a person is shown to have large optic nerve cups, it could be an indicator of damage unless it can be determined that the cup size is considered normal for that individual. The optic nerve head represents the perpendicular transition of the retinal nerve fibers from the surface of the retina to the optic nerve as they exit the eye. The normal, healthy optic nerve is composed of approximately 1.2 to 1.5 million neurons or fibers.  The optic nerve is a cable of nerve fibers that carry electrical impulses from the retina to the brain. A layer of cells on the retina, called retinal ganglion cells, is one end of this cable.. It is there that the electrical impulses are interpreted into sight. Damage to the optic nerve interrupts this flow of visual information. In glaucoma, researchers believe that the ganglion cells of the retina, as well as the support cells within the optic nerve, can die for various reasons. Glaucoma is a group of eye diseases causing optic nerve damage. The optic nerve carries images from the retina, which is the specialized light sensing tissue, to the brain so we can see. In glaucoma, eye pressure plays a role in damaging the delicate nerve fibers of the optic nerve. When a significant number of nerve fibers are damaged, blind spots develop in the field of vision.
https://en.wikipedia.org/wiki/Optic_disc_drusen http://www.tedmontgomery.com/the_eye/optcnrve.html http://www.glaucoma.org/q-a/if-i-have-a-large-optic-nerve-cup-does-that-mean-i-have-glaucoma.php http://www.rnib.org.uk/eye-health-eye-conditions/optic-neuritis https://en.wikipedia.org/wiki/Optic_nerve http://www.glaucoma.org/q-a/if-i-have-a-large-optic-nerve-cup-does-that-mean-i-have-glaucoma.php http://www.americanglaucomasociety.net/patients/faqs http://www.glaucoma.org/research/optic-nerve-regeneration-1.php http://kellogg.umich.edu/patientcare/conditions/glaucoma.html
where does the optic nerve end