Okay, I know this isn't going to be a cure -- not likely to help in all instances, but are you wearing really good suglasses? Or are you squinting a lot in the sun? That squinting takes a lot of muscle tension, and yes, it can result in wicked headaches! I need to invest in some for biking -- the ones I have are great in the car, when I'm really in the shade looking into the sun, but they don't quite cut it when I'm out in the sun for real. Just not enough coverage!

Polarized is good, cuts glare, and then, there are varying degrees of gray. I wear the darkest one most of the time, even when it's rainy! Some of the cycling glasses I've seen are available with photochromic lenses. I haven't looked closely enough to know if they're similar or different to the Transitions lenses I wear on a daily basis: I don't think they get dark enough for being in the sun "for real" -- I do like them for the in/out type use they get most of the time.

By the way: sunglasses are worth spending a good chunk of change on. Quality lenses cause less distortion, quality frames hold up better. Make sure that your optical professional knows how you plan to use them and invest in their recommendations! (I'm betting there are blind bikers out there, but I am pretty sure that seeing where we're going is more than a little bit important!)

Karen in Boise