Diplopia is a type of vision disturbance which has a wide range of causes. While some causes are relatively benign, diplopia may indicate the presence of a serious health problem. People with diplopia see two images of an object, where normally only one can be seen. The two images are typically viewed side-by-side in horizontal fashion, or one on top of the other in vertical fashion. This visual disturbance is more commonly known as double vision.
This condition may be temporary or permanent, and may be experienced in both eyes simultaneously, or in only one eye. Most people who develop diplopia are adults. It is very uncommon for children to experience double vision, because the visual system of children is able to suppress the one copy of the doubled image, so that the child sees only one image. While this is largely beneficial for the child, in some cases it can result in the development of amblyopia, also known as lazy eye. This condition causes blurry or otherwise poor vision in the affected eye.
Binocular diplopia is double vision which is seen in both eyes. Generally, this means that if a person with this misalignment looks at an object, only one eye is directed at the object; the other eye is directed either to the left or the right of the object. This causes the image of the object to fall on different spots in the retina of each eye. The brain therefore cannot resolve the two images into a single image, so the viewer experiences double vision.
This type of double vision develops because the two eyes are aligned differently in relation to one another. Often this is caused by a condition called strabismus, in which the muscles which control each eye are unable to coordinate their movement well enough to direct the eyes to the same point. Strabismus may also cause other vision disturbances, such as reduced depth perception.
Monocular diplopia is double vision which occurs only in one eye, while the other eye views images normally. This condition is much less common than binocular double vision. Monocular double vision is not caused by muscle weakness or lack of coordination; instead it is usually caused by scarring or physical deformity of the cornea, iris, or retina.
Several different types of diplopia treatment can be used in an attempt to correct the problem. One common temporary treatment is to simply patch one eye, so that only one image of an object can be seen. This prevents double vision because the brain does not have to attempt to resolve two images. Physical therapy to train the eye muscles to coordinate properly is another common treatment. More rarely, surgery may be needed to correct a severe muscular problem.
The sudden onset of double vision, particularly in adults, may indicate the presence of a serious medical condition. Sudden visual disturbances may signify a neurological abnormality such as a stroke, brain tumor, or aneurysm. Anyone who experiences a sudden serious visual disturbance such as double vision should seek immediate medical attention.