>> Frames Skip metal and go with blended nylon, which is lighter and extremely tough. To minimize peripheral light, choose wraparound frames, larger lenses, and wide temple arms. For long snow climbs, upgrade to glacier glasses with built-in, removable side shields.
>> Lenses Though glass offers excellent optical quality, polycarbonate lenses (brand names Carbonic, Plutonite) or other plastics (NXT, Trivex) are lighter and nearly indestructible. Polycarbonate scratches easier than glass, but good ones have scratch-resistant coatings.
>> Color Clear and yellow-tinted lenses are ideal for low light (cloudy days, dawn, dusk, shady areas). Dark yellow suits snow travel since yellow enhances contrast and reduces eye-damaging blue light, though this skews colors. Rose tints keep colors truer, while still increasing contrast, especially on green or blue terrains. Brown, green, and gray are good all-around, mid- to bright-light tints, so choose by preference.
>> Visible light transmission (VLT) Determined by the darkness of the tint (not the color), the VLT measures how much light passes through a lens. Low VLT (3% to 18%) glasses are darker and ideal for most bright activities, like hikes above treeline and open-water paddling. VLTs closer to 50% work for moderate- to low-light situations, like overcast and dappled rainforest treks. Mirrored coatings further deflect incoming light, but can cause ghostly image doubles if not applied well (so choose a reputable brand).
>> Ultraviolet protectionSunglasses should block at least 95% of UVA and 99% of UVB radiation (shades will be labeled accordingly). Polycarbonate lenses inherently eliminate most UV rays. Note: UV protection isn’t related to lens darkness. Some cheap shades may look dark but not block radiation. This harms your eyes more than no shades at all, since instead of squinting in bright light, your pupils dilate wider with the dark sunglasses, admitting more radiation.
>> Polarization Polarized lenses block the blinding glare from light reflecting off flat surfaces like water or snow (see above). But they also can hide slick ice patches and make LCD screens appear black.
>> Photochromic These lenses darken as skies brighten. Polycarbonate lenses achieve this with UV-sensitive dyes, which can lose effectiveness in cold weather or after several years. Photochromic lenses work great for hikes that ramble in and out of tree cover, but they have trouble keeping up with rapid sun/shade shifts, like during a trail run. And we haven’t found one that darkens enough for high-alpine travel.
>> Get fitFrames should comfortably balance weight between the temple arms and the nose piece, without any pinching. Many stores can also shape nylon frames to improve fit and relieve pressure. >> Protect your eyes Some UV-reflecting clouds actually increase the radiation reaching your eyes, so don’t doff sunglasses on murky days.
>> Protect your shadesGet a retainer strap, like those sold by Croakies or EK, to avoid an oily head-top perch or careless drops in the dirt.
>> WipeUse a clean microfiber cloth; for grimier lenses, gently wash them with warm water and dish soap (e.g., Simple Green), then dry.
>> De-fogSome sunglasses have anti-fog coatings of varying durability, and ventilation holes help, too. Good aftermarket anti-fog treatments include Fogtech, Cat Crap, and Sea Drops. In a pinch, spit on your lenses, wipe it around, then wipe it off. >> Mend For on-the-fly screw replacements, slot a paperclip or thin wire through the hinge, fold it over, and twist it around itself—bending any sharp ends away from your eyes. Broken frames are generally not fixable, but several top manufacturers offer lifetime warranties.