Causes of Double Vision
Double vision, when you see two of the same images at the same time, is essentially never normal. It means there is something wrong on the pathway your vision takes from eye to brain.
The problem can be in one of your eyes or the muscles that move your eyes, the nerve that connects your eyes to your brain, or some part of your brain that is processing the information.
There are a few ways to start to determine the causes of double vision. Is the double vision present only when both your eyes are open, or also when you have one eye covered? If it is present only with both eyes open, there is very often a problem in the way your two eyes are yoked together. Usually both eyes track sideways, up and down together, and the brain processes both images together. When this system fails, two images go to the brain that are too different to be processed as one image.
All you have to do is cover one eye at a time and see if you still have double vision. If you have double vision in one eye only, it is more likely that there is a problem either in that eye or its pathway to the brain.
The other important piece of information is whether or not the double vision came on suddenly, or has been going on for a long time. A serious injury or to the head or face (including the eye socket) can cause double vision. Health status is also a factor that must also be considered, because many illnesses and medications can cause double vision.
Double vision in one eye is usually due to a problem in that eye. Severe eye abnormalities such as corneal scars, cataracts, abnormal movement of the natural lens in the eye or of a lens implant after cataract surgery, and problems with the retina such as scarring can cause double vision, but these are uncommon causes. There has to be a very significant problem with the eye.
Most people with double vision have it only with both eyes open. There are many things doctors can tell by examination to get an idea where the problem is. They can check the motion of the eyes to see if the eye muscles are working, as well as checking that the nerves to these muscles and other nerves nearby are functioning. They can check for evidence of other muscular problems.
Muscle abnormalities are common Causes of Double Vision, including :
• Myasthenia gravis, a disease that causes muscle weakness.
• Grave’s disease, a thyroid problem that can affect the eye muscles.
Nerve problems are also common causes of double vision by leading to eye muscle weakness, include:
• Multiple sclerosis (MS), which can damage any nerves, including those to the eye muscles. MS can also damage the optic nerve which relays the information from the eye to the brain.
• Other less common causes of muscle weakness including Guillain-Barre syndrome.
• Diabetes, in this case by causing damage to a nerve leading to the eye muscles. Diabetes can also cause severe visual loss which could cause double vision in one eye.
Almost any illness or damage to the brain can cause double vision if it is in a part of the brain that involves images processing from the eyes and these causes including:
- Strokes, both from blood clots or bleeding into the brain.
- Increased pressure inside the brain. When the brain swells, it has no place to go because of the skull. The swelling can pinch nerves involved in vision. Pressure can come from trauma, bleeding or infection, among other causes.
- Brain tumors
Eye Migraine and headaches can cause double vision in one eye or both eyes. In these cases the double vision usually resolves after the headache.
Rarely, very large size difference between the images from the two eyes can cause double vision. This can occur after surgery to improve vision in one eye, such as a LASIK procedure or a cataract being removed and an artificial lens implanted.
Adults will go to the doctor with double vision because it is very distressing and makes normal activity very difficult.
Young children with amblyopia (lazy eye) may experience double vision at some point but usually are too young to tell anyone. Their brain learns to suppress the image from the lazy eye so that they only see one image.
Until the causes of double vision are found and treated when possible, an eye patch will stop it. However, this also causes a loss of depth perception, so anyone with an eye patched for this reason should get used to wearing it before driving or any other activity in which depth perception is necessary.