Yep, had them all the time when I was in my 40s, well before I developed SFN. The first one scared the crap out of me, and I ran right up to the opthamologist. By the time I got there, it had gone away.

Mine would start with slightly blurred vision, followed by a small flashing spot. The spot would eventually take the shape of a boomerang, and get larger and larger. After 20 - 30 minutes, it would go away.

Mine were definitely estrogen related. When I started on HRT, I started having them daily. When I cut back on dosage, they stopped. I haven't had one in quite a while now.