Hi, I have a problem that may sound simular, but is quite different. It only happened twice so far, but its very unusual. Twice in the same eye (the right one), I've seen what I thuoght was a black spot almost outside my field of view (other side to my nose), its very temporal, but its way outside my field of view, right in the outside corner, it appears and my eye moves to track it and get it in view, but it moves with my eye, staying at that point in your vision where your aware of somethnig, but cant really see it properly. its not my imagination, and I've never had it before these 2 times, but it was identical the second time (some 7 days+ after the first time it happend unexpectedly). I thnik its a large black spot (maybe little smaller than a little finger) and it must only appear for 1-2seconds, then its gone. I'm 28 years old, and as far as I know my eyes are fine. I dont thnik Im diabetic, and my health is fine.
I can't make a determination from your posting but certainly if it doesn't look like the other eye or has changed in appearance an Eye MD exam is important. Find one at www.aao.org
JCH III MD