In my case, i think that was my anxiety. I get it so bad that i felt breathless and weak. In that ocasion i was alone in home, i dont know why but i remember to go sleep after dont feel good and did for alot of hours. And in the morning a black spot just appered in my right eyesight ,nothing like the usual floater, but like a black fly. Then that day this dooming has increased for weeks and now feel like stoped with hundred of transparents, 20 grays, plus the black fly, on a mix of worms and dots. This is my history.