I have done some searching to see how much light transmission is ok at a certain elevation for your eyes, but can't come up with a comparison or chart. I see where "mountain climbers" need 5% to 8% light transmission in glacier glasses/sun glasses, but would like a chart or comparision table for any given elevation. I just found out, that permissible light changes by 5% percenage points for every 1000'. I would like some eye protection good for an elevation of around 8000' or less, since my winter trips are at a lower elevation than that, but could go close to that if going to Lassen Volcanic National Park. I'm going to AK in a little bit and I guess we may visit a glacier while there and I want something finally to give my eyes decent protection that I can use in the future. Does anyone know, or have a chart? If I knew what the elevation was where a maximum of 5% light transmission starts at and could figure downward, I could figure this out.

Also, I need something to fit over my small glasses, someone mentioned Cocoons, but I can't find any info on their light transmission.