I've been getting scintillating scotoma for over 50 years. They've changed character over the years from widespread fortifications to virtually no scintillation at all but always progress from a bright spot to a large blind spot to an expanding toroidal blind region with vision restored at the origin point until they pass out of my field of vision. They used to lead to headaches and sometimes speech deficits or other somatic experiences (like sizzling on my tongue and lips) but now I just get mild abdominal discomfort. With a couple of notable exceptions it lasts about an hour.

I have learned that while they're inconvenient, they're harmless and I just generally continue with whatever I was doing when they began. I have never been able to discern a trigger: they appear to come on completely randomly.