A few days ago, my vision briefly flashed twice. What could it be?

I suddenly felt as if my vision was flashing before my eyes, similar to how objects appear to flicker after staring at a bright light for a long time and then moving into a dark place, causing afterimages.

And after a day or two, suddenly those symptoms occurred again.

It seems to have lasted about 5 to 10 minutes. What could this be?

I'm also worried.