Multiple sclerosis (MS) is a progressive disease that affects the nervous system and brain. Multiple sclerosis is thought to be an autoimmune disease. The antibodies of the immune system in MS patients mistakenly attack the insulating sheath that surrounds the signal-conducting axons of nerve cells, called the myelin sheath. The damage to the myelin sheath caused by MS results in problems with nerve conduction and a variety of nervous system symptoms throughout the body, such as nerve pain, muscle spasms, balance problems, muscle coordination problems and muscle weakness. The specific symptoms that a person with multiple sclerosis experiences depend on which parts of the nervous system are affected by the disease and the severity of the inflammation.
Vision problems are commonly associated with multiple sclerosis, with over half of MS patients experiencing a condition called optic neuritis at some point. Optic neuritis does not usually cause eye pain, but other eye conditions associated with MS may cause eye pain or discomfort. Optic neuritis is caused by inflammation of the large nerve at the back of the eye, called the optic nerve, that transmits visual information between the retina of the eye and the brain. Optic neuritis is inflammation of the optic nerve. Multiple sclerosis is one of the most common causes of this condition. Optic neuritis usually affects only one eye at a time. The symptoms of optic neuritis are blurry vision, temporary blindness or graying of the visual field. Vision loss due to optic neuritis is rarely permanent; usually, once the inflammation is under control with medical treatment, vision in the affected eye usually returns to normal.
Two conditions resulting from muscle control problems of the eye in MS patients are double vision and involuntary eye movements. Double vision occurs when there is loss of control of certain eye muscles so that the two eyes are not coordinated. Involuntary eye movements, also called nystagmus, are also caused by loss of control of eye muscles. In some cases, the involuntary eye movements of nystagmus can be severe enough to cause vision problems. Neither of these symptoms commonly cause severe eye pain, although some people with nystagmus or double vision report headaches and eye strain. The eye pain reported by some multiple sclerosis patients is generally a dull pain that is worse when moving the eyes.