Sun glasses maybe????
This all boils down to environmental awareness and seeking to use your surroundings to your advantage. As the old saying goes, "Always fight with your back to the sun!"
In all honesty I don't think that it would be too big a deal, if you were unfortunate enough to find yourself in a combat situation, your adrenaline would kick in. One effect of the Adrenaline response is tunnel vision as your brain focusses all of its attention on the imeadiate source the danger. Once the adrenaline kicks its more like wearing blinkers.
Don't forget also that when your walking down the road and the car comes down the hill your attention is drawn to the headlights, thus you'll look directly at it. In a combat situation your attention will be centre solely on your opponent, so I think you'd be very unlucky to become blinded by a passing cars headlights.
So, although something to be aware of, I don't think its something to be overly concerned with. The fact that you're considering these sorts of issues show that your awareness is where it should be though, nice one!