In reply to mypyrex: OK your prescription is important. If you just need to wear specs for reading because of age (ahem! - prebyopia) then that's one thing - you could consider prescription stick on inserts inside any pair of sunnies/glacier glasses that you fancy. If you don't have need a 'reading add' then you can get many good quality specs e.g. Oakleys made to your prescription. If you wear varifocals then wrap qround styles, e.g. most Oakleys ('base 8s' - they refer to the amount of curvature of the lens) will cost you an arm and a leg if done properly, and even then may not be satisfactory. You could do worse than go to your optician for further advice, though not high street chains, obviously...
On another note I have quite an old pair of Cebe Cechinel 4000m glacier glasses, which I can't drive in because they are too dark - but my word, wearing them on a bright winter's day skiing is like stepping out of the glare into beautiful shade, and give a new lease of life! My 'normal' sunnies - which work fine in the UK - have nothing like that effect. I imagine you might experience the same in the Himalayas.