Vertical Double Vision (2)

With reference to my previous post, people asked me if it was monocular
or binocular.

I can confirm I noticed the same shadow recently looking at the green
blobs on the volume bar on the tv. Interesting I thought, and proceeded
to open and close eyes.

And there was that same shadow in my monocular vision. Though it only
lasted momentarily (1 sec max) before the ghost image joins its master.