A problem with vision is one of the most common symptoms of MS, and
often one of the first people notice. The symptoms can include blurred
vision, double vision (diplopia), optic neuritis, involuntary rapid eye
movement and occasionally, a total loss of sight.
Why does MS cause visual problems?
Problems with vision can result from damage to the optic nerve or from
an incoordination 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.