I agree that it could be a hydration/electorlyte issue. Perhaps you should experiment with drinking your electrolytes rather than taking the capsules. I get kind of jittery when I've uses capsules before. I now stick to Cytomax.

I'm also curious as to what kind of sunglasses you're using. Do they offer any glare resistance? I know that glare used to both me until I invested in some Tifosi sunglasses that protect against it. My eyes don't bother me nearly as much now.

I also found myself getting post-ride headaches when I first started riding again this spring after the winter hiatus. I started taking some Excedrin the minute the ride started and that did the trick. Eventually, I found myself forgetting to take the Excedrin, yet I stopped getting the headaches. I haven't otherwise changed any of my eating/drinking habits, so I tend to think that I was just readapting to riding.