Double vision is technically referred to as diplopia and it may be associated with a number of serious diseases. It is necessary to distinguish double vision when looking with one eye (uncommon) or when experienced with both eyes open (more common).
Causes of double vision when using one eye
Affected eye disease
In this less common case, the disorder is usually located in the affected eye. Usually it is a pathological state of cornea or lens (e.g. a cataract).
Causes of double vision when using both eyes
In this case, there is disturbed coordination between the eyes for some reason. The muscles ensuring eye movements do not operate correctly.
If a stroke affects part of the brain that is responsible for proper function of any extraocular muscle, the result is its paralysis followed by double vision. Double vision usually occurs only when looking in a certain direction, it depends which of the muscles is affected. In more severe disabilities eye asymmetry can be spotted as squinting. Minor disorders are mostly not observed by other people; however, subjective symptoms of the affected person can be very uncomfortable.
Brain tumor growing near brain centers of ocular muscles control affects their performance and can cause diplopia.
This autoimmune disease damages the central nervous system, i.e. brain and spinal cord. Resulting disruption of ocular muscles may be one of many symptoms.
Double vision is one of typical symptoms. This autoimmune disease is rare compared to previous conditions. Auto-antibodies emerge that start to attack neuromuscular junctions and thereby disrupt transmission of impulses from nerves to muscles. More detailed information can be found in relevant article.
Patient experiencing double vision should be examined by a neurologist and ophthalmologist (including ophthalmoscopy). Computed tomography or magnetic resonance scan of brain is often performed as part o neurological examination. When there is suspicion of multiple sclerosis, spinal tap is usually executed.