Seeing a double image can be alarming, whether it only lasts for a few moments or for an extended period of time. Double vision, also known as diplopia, can have a range of underlying causes. Temporary instances of double vision can be caused by certain medications, head injuries, or even too much alcohol. Prolonged or repeating cases of diplopia may be indicative of a more serious underlying medical condition. In order to identify the cause of the double vision and rule out a serious underlying problem, a visit to the eye doctor may be warranted. Read on to learn more about some of the many causes of double visions.
Monocular Double Vision
If your double vision is monocular, meaning it only occurs in one eye, and persists even if the other eye is covered up, then there may be several specific causes. These cases of diplopia are most commonly caused by something altering the optical system of the eye and changing how light is focused on the back of the eye. Astigmatism is one of the most common causes of monocular double vision, and can be easily corrected by glasses or contact lenses. Corneal irregularities, including keratoconus and degenerative dystrophies, can cause diplopia by interfering with the normal optics of the eye. Even dry eyes can cause monocular double vision. Cataracts are another possible cause of monocular diplopia, and occur quite frequently over the age of 70.
Binocular Double Vision
More commonly, diplopia occurs binocularly, meaning covering up one eye relieves the double vision. In these cases, double vision occurs because the eyes are not aligned, and the brain is receiving two different images signals from the eye. When these images between the two eyes don’t match, double vision occurs. Misalignment of the eyes can occur for many reasons. Strabismus, which is a condition found relatively frequently in childhood, occurs when one eye turns inward or outward, and can cause double vision. Systemic diseases like Myasthenia Gravis, Hyperthyroidism, or Multiple Sclerosis can cause muscle weakness, which can affect the muscles that control eye movements; this can occasionally lead to cases of double vision in such systemic diseases. Temporary cranial nerve palsies, in which certain muscles controlling eye movements are paralyzed for a short period of time, can cause episodes of double vision, and may be indicative of vascular abnormalities. Some of the causes of binocular double vision are much more emergent and require immediate medical attention. Strokes can cause double vision by hindering blood flow to certain cranial nerves or muscles responsible for eye movements. Aneurysms within the brain can also interfere with cranial nerve function, resulting in eye misalignment. Even brain tumors have the potential to cause double vision by compressing eye muscles and restricting eye movement.
Only some of the many causes of diplopia are outlined here, and numerous other potential causes for this visual disturbance exist. If you are experiencing unexplained double vision, visit your eye doctor. They may be able to identify the cause, and help you take steps to alleviate the diplopia.