RMI and Whittaker Mountaineering Gear Guides Rainier Five Day Kautz Glacier Climb - Page 10

Glacier Glasses A pair of dark-lensed sunglasses with side shields or full wrap-type sunglasses. Almost all sunglasses block UV-A, UV-B and infrared rays adequately. Pay attention to the visible light transmission. The darkest lenses (glacier glasses) only allow approx. 6% visible light to get through, while lighter lenses (driving glasses) let in as much as 20+%. A good rule of thumb is that if you can see the wearer’s pupils through the lenses, they are too light for sun protection at altitude. Glacier glasses remove 100% of UV light, and the lenses let a small fraction of visible light through so that the wearer does not have to squint on bright days. They have a large, wrap-around frames for increased coverage, and a closer fit so that reflected light does not leak in from the sides of the frame.