What is happening when I see a bright circular light in my eyes? What is happening when I see a bright circular light in my eyes?

I've had this happen twice now. I start to feel icky. Not sick to my stomach, or headache, not flu like, just icky and then this bright light appears in my eyes like when a eye doctor is looking into my eye when I have an eye exam with his light. I mean it's that bright. The only other way I could explain it is like the old time flash in a camera and you look away and you see a dark spot, well this is the opposite. I am 55 years old. And sure some people will write and say see a doctor, but the closest one is 100+ miles away. Plus it's only happened twice, in the last few months. What do you think it is? So I can research it over the internet and then travel those 100 miles etc. Thanks!

Summarized question: What could cause seeing bright circular flashes occasionally?