This is when a person sees double … that is to say, they see the same object twice.  This can be a horizontal side-by-side doubling, a vertical up-down effect, or a combination of the two.  Whenever a person has “double vision” the biggest question we ask is whether this is a monocular (one-eyed) diplopia or a binocular (two-eyed) problem. If the doubling goes away when covering either eye, then we know this is a binocular problem where the eyes are out of ‘sync’ with each other (such as with crossed-eyes).  There are many potential causes for binocular diplopia such as a cranial nerve palsy or a stroke. This alignment problem requires a thorough workup and may involve an MRI and neurologic evaluation depending upon our findings. If the double vision persists for many months, prism glasses or strabismus surgery may be required to get the eyes straightened out. Monocular (one-eye) diplopia is simpler and less concerning – if double vision remains, even when the other eye is covered, than we know the problem is located in just the eyeball itself.  Monocular diplopia is rarely an emergency and can be caused by astigmatism, dry eye, cataracts, and rarely retinal problems like an epiretinal membrane.

Dr. Timothy Root is a practicing ophthalmologist and cataract surgeon in Daytona Beach, Florida. His books, video lectures, and training resources can be found at:


  1. That really was helpful, thank you so much
    But it seems you don’t include the required eye exam so we detect the diplopia?
    Waiting for your reply Mr.root
    Thank you again


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