Same here, I'll be fine, then bang I start getting like shiney sharp lines in my vision that spread from the outside to the center. When this happens I absolutely can't work, I can barely see anything (last time my vision was so messed up I couldn't read the pamthlet on my new migraine pills to know if I was to take 1 or 2).

SOmetimes it can knock me out for a day, but sometimes after half an hour or so I'm good to go (especially if there is no pain accompanying it).

I've never had to give more explanation than "Sorry, migraine, I need to take rest of day off, see you tomorrow".