The optic nerve is the large nerve that connects the eyeball to the brain. This nerve is actually comprised of over a million individual nerve fibers that send visual signals from the retina to the brain for processing. This nerve is obviously important and several eye diseases can affect it. The most common one is glaucoma. Glaucoma occurs when the internal eye pressure is too high, causing the death of the nerve fibers over time. Another optic nerve disorder we see is called optic neuritis. This is an inflammation of the optic nerve and is sometimes associated with multiple sclerosis (which causes inflammation of nerves in the brain as well). An ION (ischemic optic neuropathy) is like a mini-stroke to the optic nerve and occurs when the blood supply to the nerve is temporarily compromised. While most of the optic nerve is located behind the eyeball, a small portion can be seen from inside the eye as the optic disk.