Is this similar to what you have?
Again, I digress..sorry for the novel.
ETA- do yours start off with a "blind spot" in your vision? I notice that mine do, for eg I'll be reading something and suddenly I can't see half of the word. Then I see a spark in my vision, like what happens when a camera flash goes off in front of your eyes.. It progresses to the point where my entire vision is affected, within about 10 minutes I can't see and start feeling sick. Sometimes there's not even an actual headache. It knocks me about so much, I'm pretty much bed bound for the rest of the day and have to sleep it off, it's horrid. Thankfully mine only occur a few times a year or less and I've figured out that they're possibly hormone related as they are always full on and frequent after I give birth and during the first few months after that.