2 LAST month we discussed how to select sunglasses that best protect your eyes against ultraviolet and blue light. Comfort is another important factor in ‘choosing sunglasses. If you spend much time at one particular outdoor activity — driving or cycling, for instance — the following types of lenses offer special characteristics that may best suit you.
Polarized Lenses are usually made by sandwiching a polarizing filter between pieces of tinted plastic or glass to block glare reflected at certain angles from water, wet or sunlit roads, a car hood, or any other horizontal surface. This makes them good for fishermen, boating enthusiasts, and drivers; however, polarized lenses may bring out distracting patterns in some windshields. Unless specially treated, polarized lenses provide little protection against ultraviolet rays and blue light.
Mirrored Lenses offer excellent protection against overall glare, since their thin metallic coating (Over a tinted lens) acts as an extra buffer against strong light. This makes them useful for water and snow sports. Some mirrored lenses block more than 90% of all visible light, but not necessarily 100% of UV rays. The mirrored coating scratches easily.
Photochromic Lenses are made of light sensitive glass (rarely plastic) that automatically adjusts to light conditions. They’re good for cyclists, golfers, and other people who are in constantly changing light conditions. They don’t work well in a car, however, since the interior isn’t that bright and the windshield blocks much of the UV radiation that stimulates them. If you’re considering sun sensitive lenses, make sure they get dark enough when you go outside, and remember they may take several minutes to adjust to light conditions. How dark they become largely depends on their thickness and the temperature. Photochromic treatment is not by itself effective against all UV rays and blue light.
Gradient Lenses: Many drivers and pilots prefer single gradient lenses (darker at top than at bottom), which allow them to see the dashboard or instrument panel easily. Because of glare reflecting off snow or water, skiers and many fishermen prefer double gradient lenses (darker at top and bottom than in the middle). Gradient lenses can be polarized, photochromic or mirrored.
Article extracted from this publication >> July 8, 1988
