I know this might look more appropriate to ask this kind of question on the biology or medical stackexchange but since this kind of cross-science question I'll ask it here.
Sometimes when sitting and working on my computer I get to see sparkles which look like particle trajectories.
Sometimes they look like electron-positron decay going in spiral, sometimes they is just a line, a trace.
I suppose the nerves that transfer electric signals from the eye to the brain get to interact with some kind of electrical stuff (electrons ? electrons absorbing EM waves ?). This kind of sparkles are different from the ones you would see if you were to hit your head on the ground (or any other childish stuff).
Does anybody knows from where this "electric" perturbations come from ?
Could it be from environmental radiation, like Earth's natural radioactivity, or energetic cosmic beams that reach Earth ?
$dt$ is about 100ms-500ms.
Note: this is a question addressed in a rational way and I expect a physical interpretation - if any (= not superstitious stuff. thx)