This is almost exactly what mine look like:
Sometimes I can still see in the middle, sometimes it's the middle that goes and I can see around. They usually last from 15-60 minutes, followed by either no headache or a light headache.
What makes me nervous is my mother used to get violent migraines. Full on 3 days in bed, puking, horrible pain, the works. I'd like to avoid getting to that point if possible!
There was discussion in the other thread around various medications. I'd be open to pot if it worked. I get them so infrequently that having to head home to puff and sleep wouldn't be a bad thing!