Why do we "see stars"?

Question

Not real stars...you know what I mean, right?

Answer 1

well...it's normal. Usually occurs to anemic person. When u get up so fast, the blood is not completely transferred to your brain/head, so that is a respond from your optic nerve which got information in form of sparkling vision. that why u see "stars" every time u do that.

I often had it all the time,especially when i don't get enough food to eat.

Answer 2

When your brain or your optic nerve suffer some injury (due to a bump on the head, an infection, or a tumor, etc) there can be electrical signals that the brain interprets as "stars".  You are not seeing actual light but only the misfiring of neurons.