Over the last year I seem to have developed monocular diplopia in my right eye (always there, just more noticeable at times.) My left eye is absolutely fine. The diplopia is vertical. Apart from the ghost image the actual vision seems quite clear. The effect is very noticeable with LEDs and highly contrasted images. I've done the pinhole test which seems to correct the problem. I have very mild myopia in my right eye as well. When I do wear my glasses (I never normally wear them) it also seems to correct the diplopia. I'm 30 and male.
Any idea on where the problem could be? My latest reading suggests some kind of a refractive error, but I don't really understand the finer details.