Half Circle Light Flash on the Right Corner of Eye?

When I look to the far right really fast or upper corner or even lower corner on my right eye I see a flash but a small light kinda blue or something, but it only happens when I look really fast in the dark, it kinda looks like a half circle or what we see a half of the moon, I also have many floaters, the eye docter told me I dont have a retinal detachment, Im trying to figure out what it is and I cant find any answers on here. I kinda remember seeing this when I was a kid also, does anyone else get this? please answer.