The first time I got it, a few years ago, I thought I was having a stroke.
The visual area gets ripped in two by the diagonal, the two pieces move away and are replaced with a silver band. The picture stays more or less complete, but broken in two. The image kind of pulsates, or rather waves.
I was terrified the first time, then visited the ophthalmologist, did a tomography of my head and ended up at a neurologist. He was a specialist of migraines and told me that about 30% of migraines are without headaches.
My father has migraines, my younger brother too and both have headaches.
I had some other extasy-like migranes and I am usually exhausted afterwrds and sleep 10 to 12 hours straight.
I am lucky to have only a few cases a year.