I get these and also have worried about a tumor until figured out what was going on (sort of). They are usually triggered by lack of sleep and or stress.
I describe them as psychedelic neon abstract Australian Aboriginal art combined with an inability to form a coherent picture of what I see. I can see my environment but it is fractured.
Once experienced this phenomena while playing a in a high school basketball game and took a shot that missed the entire backboard and also threw a pass 5 feet behind a teammate. My coach asked if I was stoned.
