I'd call it slight hallucination. The eyes play tricks in the dark & shadows. I have these slight ones often but like you, I know they're not "real". I think that's a big factor, not positive, but whether you know it is real or not. Others will know more about this & if its severe or concerning. When I see the shadows, they might startle me at first, but usually I can choose what imaginary shape to morph them into. Hope you're ok.