On occaision I'll see very bright spots, usually in a circle, in the center of my vision. It usually happens after I've been in bright sunlight or in front of a bright screen in the dark for a long time. If I don't go into the dark it gets worse and can lead to a migraine. It usually leads to a minor headache at least.
My optometrist said it had to do with my optic nerve. I was hoping you could give me more information?
Specifically, are they really migraines or just bad headaches? Is it possible to get auras without getting a headache?

Yes, you can get a migraine aura without the headache. The classic visual aura is a circle or semi-circle with jagged edges. There are triggers for migraines, so keep track of when this happens.