I suddenly (yesterday evening) noticed that with my left eye, I see a thin, light-colored, semi-circular stretch of line -- not particularly long -- that has a smaller dark patch behind it, as if forming the 'background' for it. It doesn't seem to be a floater -- it doesn't float. And here's the strange part: it is visible only as I shift fixation from one spot to another. In other words, it does not obscure my vision. It only appears briefly as I change fixation and then disappears. Always in precisely the same location in my visual field. More visible on a white or bright background. The darker part seems to be located where an obsessive observer would notice a dark spot even in a normal eye upon rapidly shifting his gaze :)
Pertinent history: Longtime 'painless migraine'-type scintillating scotoma, with some spots remaining for a day to a couple of months before receding. Standard cataract operation 16 months ago, no complications, excellent vision post-procedure. Lifetime nearsightedness, approximately 4.5 diopters.
Shall I panic and run to the ER on a Sunday?
Thanks.