Glacier Glasses for trekking, climbing and skiing in the alps and greater ranges on calm to middling days. Category 3 will be fine for most uses but for prolonged exposure at very high altitudes (eg expeditions) or for those with weak eyes, Category 4 is preferable. All the glasses on this page have frames with close fitting sides that block out light getting in round the edges and so protect your eyes - it is this that differentiates them from sunglasses, though on many of these glacier glasses the side pieces can be removed for day to day use.
By far the best choice for everything from alpine climbing and ski-ing to prolonged exposure on the world's highest peak are Reactive Glasses, as the lenses automatically adjust according to the light conditions. They can also be used as day to day sunglasses for car driving etc. The downside is that they are more expensive than single category glasses. In Julbo terminology, Zebra adjusts from Category 2-4, while Chameleon does the same but are also polarised which reduces reflected glare.