Double vision, or diplopia, is not the same as blurry vision. People who have diplopia see two distinct clear images of a single object, rather than one blurred image. Seeing double can interfere with even the simplest of activities, like writing, and make complicated tasks impossible.
There are two types of diplopia - binocular and
monocular. Binocular diplopia is present only when both eyes are open. The double vision disappears if either eye is closed. Binocular diplopia 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.
The two most common causes of binocular diplopia 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 tumour, 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.
Giant cell artertis, an inflammation of the arteries that often affects blood vessels in the head, can also cause double vision. Symptoms of this condition typically are fever, weakness, weight loss, headaches, temple pain, and stiffness of the neck, hips, and shoulders. Immediate treatment with corticosteroids is essential to avoid blindness and other serious complications.
Monocular diplopia is present with both eyes open but, unlike binocular diplopia, persists when the problematic eye is open and the fellow eye is closed. Monocular diplopia 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 diplopia.
Some cases of diplopia resolve after a change of eye
wear prescription. You may be asked to maintain strict control of his BP and blood sugar. His binocular diplopia was treated with prisms incorporated into his glasses. He was also given an eye patch "which makes me look rakish and interesting," he grins. But his opthalmologist has warned him that if his condition doesn't improve or resolve with these measures, surgery may be needed. Monocular diplopia is addressed by treating the underlying condition, using anything from eye drops (for dry eyes) to surgery (for cataracts).
A word of warning:
Over time, binocular diplopia 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 diplopia in the first place. If you're experiencing diplopia, see an ophthalmologistimmediately. The sooner you seek help, the better your chances of nipping, and the trouble in the bud. There's no fun in seeing double if the extra zeros at the end of your bank balance don't pan out in reality.