Optic neuritis is the term used when there is inflammation in the optic nerve, which is the bunch of nerve fibers tasked with transmitting visual information to the brain. A rare condition, it is most commonly associated with multiple sclerosis in that it can possibly be an early indication of the disorder. It is also often related to neuromyelitis optica, which is a condition similar to MS in that it causes an inflammation of the spinal cord and optic nerve.
It is not yet known what causes optic neuritis. However, some experts believe it develops when a person’s immune system accidentally targets the myelin, or the protective substance that covers the optic nerve. The myelin normally aids in the transmission of electrical impulses