Optic Neuritis is one of the more common presenting symptoms of Multiple Sclerosis (MS) and can cause blurred vision, color blindness, loss of vision, pain behind the eyes and even flashing/flickering lights. This usually occurs in one eye but both eyes being affected is not uncommon. Typically people just complain about their vision blurring and never experience anything else.
An LP (Lumbar Puncture; AKA Spinal Tap) is a procedure in which a needle is placed between two vertebrae of the lumbar (lower back) area of the spine to extract cerebrospinal fluid (CSF). CSF is a clear liquid that surrounds the brain and spinal cord and is usually extracted for diagnostic purposes, for example, diagnosing Multiple Sclerosis (MS) by looking for myelin proteins in the CSF. MS attacks the myelin around nerves which causes pieces of myelin to break away into the cerebrospinal fluid around the brain and spinal cord.