Not much you can do in my experience. I'm personally as irritated as the OP by it but getting revenge doesn't help anyone's cause. You still can't see and now neither can they (as is pointed out above). Your best bet, and what I do when I am prepared for it, is to watch the right edge of the road versus staring straight back at those high beams. There's something magnetic about really bright lights and it certainly fuels the fire when you stare at them longer but it does nothing to help you see the road. As for being prepared for the high beams, I seem to be surrounded by some real dimwits who apparently figure out that I'm just a guy on a bike and throw on their high beams (or turn them back on) before they've passed me. Argh! FWIW I've been riding with a L&M Arc Ultra (650 lumens IIRC) but it's getting replaced after a second battery failure.