When I was little I would watch cartoon network and see the cartoons hit their head and circle of stars would circle their head just like this picture. I never believed you actually saw stars I always thought it was just a cartoon thing. However, one time I fell so quickly to the ground and got up right away and saw stars. I thought I was a cartoon. I was so confused and wondered why does that happen to real people? I thought that only happens on TV!
The stars you see are actually just neurons in your visual cortex https://en.wikipedia.org/wiki/Visual_cortex firing randomly. This happens when their “oxygenation level changes abruptly” either because you stood up too quickly, which was my case or because you got hit in the head. The neurons closet to capillaries are affected first and, and it can fire before the surrounding neurons. The result in isolated signals that your brain interprets as lights.
The stimulus that causes “stars” is mostly from being hit in the head. However, for those of you who have never seen stars, you don’t always see stars. When you hit your head on a surface after standing up, “your head stops, but is surrounded by cerebrospinal fluid https://en.wikipedia.org/wiki/Cerebrospinal_fluid,” which means it is cushioned from your skull.
It is possible to seen “stars” without being hit in the head or standing up too quickly. There are less dramatic ways you can experience “stars.” For example when you wake up in the morning and rub your eyes really hard you can see stars because you are, “creating the same stimulus that the retina would when it sees light.” That is because the retina is used to see like or no to see light.