Double vision is not a common occurrence for most patients, but it’s a problem that be very 
debilitating. Double vision may be a sign of a serious underlying problem, or may simply require the right eyeglasses or therapy to treat the problem. This article will cover the most common causes of double vision, also called diplopia. For treatment options in a companion article, click here.
Double vision can just present one day, or may start to present intermittently over time. Normally the brain processes what each eye sees and fuses the two images to create one three dimensional image. This is processed at different levels of the brain. This process begins in each eye. Here are the common sources of double vision:
Eye Muscle Problems
Behind each eye there are 6 muscles that move the eye. These six muscles must work in tandem with the six muscles of the other eye in order for the eyes to track the same object at the same time. This system is delicate and for many patients, isn’t perfectly ‘fine tuned’. In most cases, patients will compensate by using their eye muscles a little harder or tilting or turning their head slightly to allow for easier coordination of the eye muscles. In mild cases of muscle imbalance there are no symptoms. For other patients, this is a common source of headaches. For still others, the result is double vision.
Cranial Nerve Problems
Most of the nerves in the body come off the spinal cord. But 12 nerves come off the brain directly and provide stimulation the muscles of the head and neck, and serve to bring you your sense of smell, hearing, and vision. Three of these twelve nerves have branches that go to the 6 muscles behind each eye. If the eye muscles are positioned properly with normal nerve function, then no double vision results. But for some folks an underlying condition may affect the function of one or more of these nerves, resulting double vision.
Problems that may affect nerve and/or muscle function include:
- Myasthenia gravis – an autoimmune disorder that affects nerve stimulation of muscles may show up first in eye function, resulting in double vision or drooping of the eyelids
- Grave’s disease – a thyroid disorder that affects eye muscle control
- Multiple sclerosis – this disorder can affect muscle control anywhere in the body, sometimes producing double vision
- Uncontrolled diabetes can cause nerve damage and produce double vision
Since double vision can be the result of an underlying problem, it’s imperative that patients see their eye doctor for a full evaluation. The eye doctor may coordinate care with other specialists as needed to detect and treat an underlying problem.
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