A problem with vision is one of the most common symptoms of MS, and often one of the first that people with MS notice. The symptoms can include blurred vision, double vision (diplopia), optic neuritis, involuntary rapid eye movement and occasionally, a total loss of sight.
Problems with vision can result from damage to the optic nerve or from a lack of coordination in the eye muscles. The optic nerve connects the eye to the brain. Inflammation or demyelination in the optic nerve causes optic neuritis, which is experienced as a temporary loss or disturbance in vision and possibly pain behind the affected eye.
Typically, vision returns partially or fully within a few weeks. While it is quite rare for a person with MS to become totally blind, it is not at all uncommon for an individual to have recurrent episodes of optic neuritis over the course of the disease, usually in one eye at a time. Damage to the optic nerve can result in a blurring of vision, which may or may not totally resolve over time. Colour vision requires a great many nerve fibres from the eye for accurate transmission and is particularly susceptible to changes from demyelination.
Optic neuritis can cause a large, noticeable “blind spot” in the centre of the visual field, and the person experiences a visual image with a dark, blank area in the middle. This is called a central scotoma and is not correctable with either eyeglasses or medication, although steroids may be helpful in the early, acute phase.
Diplopia (double vision), the experience of seeing two of everything, is caused by weakening or incoordination of eye muscles. This symptom is typically treated with a short course of steroids. Patching one eye while trying to drive or read will stop the double image; however, permanent patching of the eye will slow the brain’s remarkable ability to accommodate to the weakness and produce a single image in spite of the weakened muscles. Some physicians are prescribing eyeglasses with special prisms that help to minimise double vision.
Upon examination, the physician may detect a rhythmic jerkiness or bounce in one or both eyes. This relatively common visual finding in MS is nystagmus. Nystagmus does not always cause symptoms of which the person is aware. In the event that it does become troublesome, clonazepan (Klonopin®) is sometimes effective in reducing this annoying but painless problem.