Infrared Lenses
From LoveToKnow Sunglasses
Everyone knows about the dangers of UV exposure -- those short wavelengths can damage skin and eyes -- but what about the longer wavelengths of infrared light? Special infrared lenses can be used to protect against them, as well.
What Is Infrared?
To understand what infrared is, you must first understand the electromagnetic spectrum, much of which is not visible to the unaided human eye. The electromagnetic spectrum includes (from longest wavelength to shortest) radio waves, microwaves, infrared, red, orange, yellow, green, blue, indigo, violet, ultraviolet, x-rays, and gamma rays. The human eye can see only those wavelengths from red to violet; this portion of the electromagnetic spectrum is called "visible light."
Red light is the longest wavelength of visible light. Infrared has a longer wavelength than red light; its wavelength is 780 to 1400 nm (nanometers). Infrared light is perceived as heat -- it is what causes you to feel the heat of the sun on a warm day.
Uses of Infrared
The primary use of infrared light is in night-vision applications and in remote control devices. Photographers also use infrared filters to achieve unusual and interesting photographic effects.
Why Protect Against Infrared?
Because infrared light is perceived as heat energy, it is important to protect both the skin and the eyes from it. Most research indicates that normal exposure to infrared is not dangerous; however, there are certain groups of people who receive far more exposure than the average person. It is these people who are at risk from infrared, and who should take precautions.
Aircraft pilots are at greater risk of exposure to both UV and infrared. According to the FAA, UV exposure increases by five percent for every 1000 feet of altitude.
It makes sense that infrared exposure would also increase at higher altitudes, as the long wavelengths do not have to pass through as much of the atmosphere at higher levels. Besides pilots, mountain climbers and those who live at very high altitudes are also at risk for greater exposure to non-visible light.
Where to Get Infrared Lenses
Many sunglasses manufacturers offer infrared protection. Grey and green lenses seem to block the most infrared, while yellow lenses, unless specially treated, do not block infrared at all. Columbia Sportswear and Bolle offer sunglasses that are supposed to block infrared rays.
Important Caution about Infrared Lenses
Infrared sunglasses lenses will not enable the wearer to see better in the dark. The application of the infrared filter may, in fact, make the lenses so dark that they would be more than usually hazardous for night-time wear. For better vision in the dark, one should purchase night-vision goggles, which are specially designed to gather infrared light so that objects can be seen in the dark.
Some Controversy
Many experts feel that it is unnecessary to apply special, sometimes expensive, coatings to sunglasses lenses to block infrared light. The danger (for the average person) of harmful exposure to IR is so slight as to be negligible. In addition, many of the infrared lenses on the market do not live up to their claims, so there is concern about the consumer being cheated into paying for something that they do not get.
Learn More
Comments
You can get a UV coating on any pair of prescription glasses for a (usually) relatively small cost. Polycarbonate lenses have UV protection included. You may see UVA/UVB protection on tags; that's because the UVC rays don't make it through the earth's atmosphere. The UVC rays won't make it to the ground to harm us. As for infrared light, the sun doesn't omit a lot of infrared rays. UV rays are the ones that will do the most harm. However, you will find that polarized lenses are more effective at filtering out infrared light (though they probably won't claim to filter out 100%).
Overall, just looking for a pair of polarized prescription lenses will best suit your needs. In that case, you have a few options:
- Fitovers, which fit over your regular prescription glasses
- Having polarized lenses custom cut with your prescription, either through an optical shop or an authorized dealer such as Bolle, Costa del Mar, Oakley, or Wiley X.
- Inserts, which are a kind of fitover style hybrid. You don't have to wear your normal prescription eyeglasses with these, but the prescription is not in the outside lens. There's a piece that snaps to the bridge on the inside of the frames. That piece houses the clear lenses with your prescription. The outside lenses can be clear or dark. These are ideal for those who sometimes wear contacts, because the insert comes out and you're left with sunglasses. Check with the authorized dealers above for those, plus Adidas.
For the best protection, choose a wraparound style or large lenses. Remember that your sunglasses only protect you from the rays that come through the lenses, so if there is room for rays to come from around the sunglasses, you may not be getting ideal protection.
-- Contributed by: CrystalSchwankeWhich prescription sunglasses filter 100% infrared light and 100% UV a/b/c?
Peter
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