I don't know about dogs, but I have what's called a blonde eye, and that means I have very very little pigment on the back on my eye, or wherever, which means bright lights really mess me up. I was a very blonde child, and I'm still a pale person, I just don't have a lot of pigment anywhere really, including my eyes.
I have the glasses that darken in bright light to help with it, and they really do. It sucks in bright sunlight without my glass, and can give me a headache really quickly.