Hi oldsheep,
I used to have migraines with visual disturbances when I was younger. My triggers were fresh orange juice, chocolate, the smell of oil based products like petrol, gloss paints, solvents like turps, and even oil-based paints in the art room at school. I would get the visuals first, followed by an almighty headache with vomitting. Then afterwards I would feel limp, spaced out and washed out for about 48 hours, during which I needed to eat carbs. Oddly enough, I would be really hungry just before the aura started and would yawn uncontrollably (not ideal in the school classroom).
Your visual disturbance sounds very similar to mine but without the crashing headache.
Galadriel x