Migrain So bad I went Blind?

just yesterday I had the worst migrain I got Really Dizzy then Everything went black for about an hour and a half Give or take. I have Maigrans Daily but never this bad. I usually have them Combined with Bloody Noeses and Throwing up but never blindness. This is a First for me. I don't know what Else to do. The Doctors can seem to find any thing Wrong. All my CT scans and my MRI's came back Negative Any advise for me?