The best defense for sun in the eyes is a baseball cap. As its usually an issue when doing the upper windows.
I have a pair of polarised sunglasses (rating level 4, 5 being the highest), I find I'm constantly removing them to make sure the windows are being rinsed clear.
They do make it more comfortable, and offers protection for your eyes when working in sunny conditions.
For those times of the day when the sun is just above the roof line, a basbeball cap, or other rimmed hat works wonders to keep the direct light out of your eyes. Basically for those times when you use your hand to block the sunlight when you look up.