In reply to pascoa341: With sunglasses I'm pretty sure the answer is that you either go pretty basic, or top of the range. Unless you are going to pay well over £100 RRP I personally don't think you will find anything that offers any better performance than the most basic Quechua pairs from Decathlon.
Others are welcome to disagree but I certainly can't tell the slightest difference in performance between most brand name £25 pairs and £80 pairs.
If you do loads of hardcore skiing and want maximum performance in flat-light then the correct £200+ pair of Oakleys with interchangeable lenses will certainly give you an edge, but you need to consider firstly whether you can afford it and second whether you can be sure that you won't lose, break, scratch or otherwise trash them in short order.
Personally find I can manage fine with basic 'grade 3' wrap around sunglasses in the mountains but I rarely spend day after day on snow with bright sun. However, on a long high-altitude exped I would be taking two pairs of sunglasses as a matter of course (as well as googles) and in that case one pair would probably be 'grade 4'. It is worth remembering that it is against the law to drive with 'grade 4' sunglasses meaning that if you go for the darkest possible ones with side and nose guards you would need another pair for any driving.