Problems with vision are relatively common in MS. MS may cause blurring of vision or difficulty with eye movement.
Optic neuritis is the most common problem in MS. Almost 70 percent of people with MS experience optic neuritis at some point during the course of the disease and, in fact, 35 percent visit their doctor with optic neuritis presenting as an initial symptom.
The rate of onset of optic neuritis can vary from a few hours to a few days and sometimes greater. Often, sight is at its worst about one week after onset of symptoms. The good news is that optic neuritis is transient and often occurs in just one eye, and any vision loss is usually temporary.
Diplopia refers to double vision. In MS, the nerve pathways that control eye movements may be damaged. When this occurs, the eyes may not move through their full range of movement and double vision may occur.
Nystagmus is defined as jerky, involuntary movement of the eyes and is usually related to brain stem inflammation in areas that control eye movement. Nystagmus may be vertical or horizontal and can occur in one or both eyes. Loss of balance or dizziness may accompany this symptom.
Afferent Pupillary Defect (APD)
Afferent pupillary defect occurs when one pupil fails to dilate properly. It doesn't cause visual disturbances, so you may not notice this yourself unless someone points it out to you. In people with MS, it usually happens because the person has had optic neuritis, even if the episode was so mild that he was not aware that it occurred.
APD is identified by examining the eyes with a bright light. During a neurological exam, your doctor may perform the swinging flashlight test, where your doctor shines a flashlight in one eye and then the other. In normal circumstances, when a light is shined in one eye, both pupils constrict (get smaller) at the same time. However, when a light is shined in the affected eye of a patient with APD, the pupil of the affected eye dilates (gets larger) rather than constricts.