I see a scintillating checkerboard pattern when I'm getting a migraine. It actually replaces most of my vision, then slowly fades until the pain starts. So if I

I see a scintillating checkerboard pattern when I'm getting a migraine. It actually replaces most of my vision, then slowly fades until the pain starts. So if I start getting one I have about 10 minutes to get home before I'm blind enough to be unable to drive safely, and another 20 before I need to lay down in a dark room.