Bright light is blinding and the effect is magnified by the reflective surfaces all around you. Heavy snow and low-hanging clouds can cause the contours of a landscape to completely disappear. To be prepared for this phenomenon, you should bring along protection for your eyes both in the form of a pair of good sunglasses with dark glass and high-quality UV protection as well as a pair of ski goggles, which increases the contrast when the weather is bad. Remember that your sunglasses should also have side protectors to minimise the amount of light leakage.
Snow blindness is the result of bright sunlight shining on unprotected eyes, which causes small sores to appear on the cornea. It is painful and, as the name implies, you become blind and dependent on others, often for several days. There is often little you can do other than rest in a darkened tent until the sores go away. Eye drops or a liniment can ease the pain. (It is possible to tape over your sunglasses so that only a small hole remains, and in that way at least be able to move, but this is usually not a very practical solution.)
Goggles offer contrast
Ski goggles protect your eyes from the wind and drifting snow, which is composed of tiny, sharp crystals that are actually another cause of snow blindness. Many goggles have dark lenses to offer protection from the strong rays of the sun, but these do not work very well when you are experiencing a “whiteout” since you then need something to help enhance the contrast – for example a yellow- or orange-tinted lens. Some ski goggles come with pop-out lenses, and you may want to consider investing in a pair. Otherwise, a practical alternative is to find a pair of goggles with light lenses that you can wear over a pair of sunglasses.