My husband is always changing the different types of sunglasses he wears. The pair he likes the most are his Bolle. Being my husband works outdoors in the construction trade different variables of sunshine make a lot of difference when you're working a hundred foot off the ground building scaffolding. He said the worst time on the job was when he was working on a huge mall they were working on the east side and the corner of the north side on the same day.
There was snow and bright sunshine on the east side unlike the north side was dark with no snow. Normally he would just slide his glasses up on his head but with the hard hat and safety issues for his eyes he couldn't do this. As he turned the corner to the darkness it would take a minute or two to adjust to the darkness.