Double vision, or diplopia, is not the same as blurry vision. People who have double vision see two distinct clear images of a single object, rather than one blurred image. Seeing double can interfere with even the simplest of activities and make complicated tasks impossible. In this Health Alert, Johns Hopkins Professor Susan B. Bressler, M.D. discusses the causes and treatment options of double vision.
There are two types of double vision -- binocular and monocular. Binocular double vision is present only when both eyes are open. The double vision disappears if either eye is closed. Binocular double vision is caused by problems with the extraocular muscles that control the eyeball or the nerves that signal these muscles. If the eyeballs aren’t correctly aligned and moving in synchrony with one another, the images generated from each eye are focused on a different point and don’t match up. Double vision is the natural result.
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According to Susan B. Bressler, M.D., Professor of Medicine in the Department of Ophthalmology at Johns Hopkins, the two most common causes of binocular double vision in people over 50 are thyroid conditions, such as Graves’ disease, and cranial nerve damage. Graves’ disease can affect the extraocular muscles directly. In most cases, however, underlying nerve damage causes the extraocular muscles to malfunction. Multiple sclerosis, a brain tumor, head trauma, or stroke can all damage the cranial nerves, but the most common cause is diminished blood flow due to high blood pressure or diabetes.
Monocular double vision is present with both eyes open but, unlike binocular double vision, persists when the problematic eye is open and the contralateral (fellow) eye is closed. Monocular double vision is caused not by misalignment, but rather by problems in the eyeball itself. Astigmatism, dry eye, and some retinal problems or certain cataracts can all cause monocular double vision.
Getting Treatment for Double Vision -- Some cases of double vision resolve after a change of eyewear prescription. Binocular double vision may be treated with prisms incorporated into glasses or with an eye patch. If the condition doesn’t improve using these measures, surgery may be considered. Monocular double vision is addressed by treating the underlying condition, using anything from eyedrops (for dry eyes) to surgery (for cataracts).
Bottom line on double vision: Over time, binocular double vision may seem to go away on its own, as the brain eventually learns to suppress one of the mismatching images to avoid seeing double. While the symptom of double vision improves, you may still be suffering from whatever condition caused the double vision in the first place. If you’re experiencing double vision, make an appointment with an ophthalmologist as soon as possible. With so many possible causes, the sooner you seek help, the better your chances of seeing clearly in the future.
