Ski-alpinism racer
Es Tresidder needs a pair of sunnies that don't mist up, whatever the conditions.
"Ski-alpinism racing takes place on snow (obviously), and it's often sunny and at relatively high altitudes. However, it also has the almost unique combination for a snow sport of extremely high levels of exertion at relatively modest speeds. This makes it very challenging to find sunglasses that don't mist up – they have to deal with a huge amount of moisture coming their way, and the air isn't moving around them as fast as it might in other sports. "
Read more at http://www.ukclimbing.com/gear/review.php?id=4121