Diplopia is more commonly known as double vision. Each
eye has six different muscles responsible for moving it in various
directions. That means the brain has to control 12 eye muscles simultaneously.
The control of these 12 muscles is coordinated through a system of
nerve connections that course throughout the brainstem. Not surpisingly,
such a complex system is vulnerable to a large number of disease conditions.
Three different cranial nerves supply the eye muscles of each eye,
and anything causing damage to them can cause double vision. Strokes,
trauma (injury) and brain tumors are some of the things that can damage
these cranial nerves.
Diabetes is also a common cause of double vision and
occurs when the damage caused by diabetes causes a small stroke to
one of the cranial nerves. Any disease process that involves the eye
muscles themselves can also cause double vision. Interestingly, children
born with eye alignment problems, such as esotropia ("crossed
eyes"), do not experience double vision. Many people have some
imbalance of their alignment mechanisms, and for them the optometrist
can usually help with the prescription of a prism in their glasses.
Prisms help align the images properly when the eyes fail to do the
job, thus eliminating double vision.
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