SKILLIANS_at_aol.com wrote: > Info from one of my favorite websites: (www.straightdope.com) > > Tests of sunglasses have found wide variations in their effectiveness > against UV, regardless of cost, tint color, or lens material. Ignore the > sales hype and look for the following voluntary industry labels. > "Cosmetic" sunglasses block 70 percent of the sun's most damaging rays, > "general purpose" shades block 95 percent, and "special purpose" glasses > block 99 percent. "UV-400," another label you often see, supposedly > means the sunglasses block 100 percent of UV. A lot of experts recommend > glasses in the latter two categories, the special purpose in this case > being that they may keep you from going blind. Today, there was a post on rec.boats.paddle that said that Consumers Reports claimed little difference between sunglass quality (wrt uv resistance) based on cost etc. Hmmm Check http://www.polycarb.org/ for info on polycarbonate lenses. 99% UV absorption for most optical formulations. If all the lenses tested were optical polycarbonate, this could explain the CR results. Glass lensed sunglasses need specific coatings to make them UV absorbent. The optical polycarbonate lenses are (in Canada at least) required to have adequate UV absorption. A friend of mine, an optician and professor/ researcher at a nearby university, will only prescribe polycarbonate lenses for patients. Contact lenses are also UV absorbent, so if you wear them, your need for UV absorbent sunglasses is reduced (I still insist on the 99% lenses) His research specialty is radiation damage to the eye and this makes for interesting conversations. I asked him about the use of glass-lensed binoculars (not UV blocking) and the risk of enhanced light grasp and reflected UV getting into the eye. He assured me that this is not an issue due to relatively low exposure and short exposure times. He also pointed out the effects of blue light on the eye (close to UV in the spectrum). High intensity blue light can cause rapid heating in retina cells to the point that individual cells boil and explode! (Sounds dramatic, huh?). Mountain Equipment Coop, in their catalogues, recommend getting lenses that also absorb a lot of blue light in addition to UV. They list glasses according to the absorption at different parts of the UV-Blue spectrum. One of his big issues is the consumption of a certain recreational weed that some advocates claim is actually good for the eyes (based on the observation that internal eye pressure is reduced by its consumption). Ha! Yes folks, we're talking about marijuana. His tests on rabbits showed that THC consumption significantly increased the eye's sensitivity to UV radiation. In one series of tests, high doses of THC followed by relatively high exposure to UV resulted in the rabbits' eyes shriveling up and falling out (I've seen the photos and they aren't pleasant). Lower doses cause less damage, but damage nonetheless. The sensitivity is long term, not limited to the immediate period after consumption. So if you indulge, wear 100% UV wrap-around lenses or paddle only at night. Mike *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.paddlewise.net/ ***************************************************************************Received on Sun Aug 15 1999 - 12:27:25 PDT
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