Is monocular diplopia dangerous and should be fixed immediately?

Monocular diplopia means "seeing two images out of one eye." Most diplopia is due to a lack of alignment between the two eyes.

But it is indeed possible to "see double" out of one eye. Usually this double vision is more of a "ghost image:" a second, more faded image just offset a little on the object of regard.

The most common reason for this in middle age is the onset of cataract development in the natural lens of the eye. Having two areas of the lens focusing slightly differently is the reason. When it gets bad enough, a new artificial lens implant can be used to replace the failing natural lens.

The second most common reason I see is after refractive surgery such as LASIK. If there is a significant irregularity in the cornea from that surgery, it can also create a "ghost image" which is reported as double vision. None of these are emergencies but they should be followed up by the appropriate eye doctor.

_Written by J. Trevor Woodhams, M.D. - Chief of Surgery, Woodhams Eye Clinic