Polarization Facts   UV Facts

Polarized Sunglasses Polarization Facts

What is "polarized" light? Ambient light or the light we use to see is comprised of light waves that vibrate in an infinite number of directions. Quite often however, these light waves are reflected off of flat or shiny surfaces. These reflective surfaces concentrate the light causing the vibrations of these light waves to travel in the same direction as opposed to being scattered in a random fashion. These unidirectional waves which are much more intense are what are known as "polarized" light waves. These polarized waves are many times brighter than non-polarized light and are otherwise known as "glare".

What are "polarized" sunglasses?Polarized sunglasses contain polarized lenses. Polarized lenses contain a special material designed to absorb these polarized waves before they reach your eyes. The special material still allows most of the ambient light through for better visual acuity. This optically engineered material is actually a very thin membrane that is sandwiched between two pieces of optically ground lens material. If you were to take apart a polarized lens you would find that each lens is comprised of a minimum of 3 pieces. Regular or non-polarized sunglasses do not have this polarized light absorbing membrane. In recent years there have been major advances in the methods manufacturers use to sandwich this membrane in each lens. These advances have significantly improved the quality of polarized lenses

What is the difference between polarization and UV protection?Polarization has nothing to do with UV protection. All sunglasses offer some amount of UV protection attributed to their darkening effect. Most polarized lenses will offer superior UVA and UVB protection when compared to regular sunglasses. The improved UV protection results from their engineered design.

Why do I need Polarized sunglasses? There are several reasons: - Contact lens wearers often suffer increased discomfort from glare. Glare can be 7 to 10 times brighter than normal light. As the eye tries to adjust to glare, it constricts the pupil to reduce the amount of light coming in. Since a minimum amount of light is needed to see, your eye adjusts to let in as much light as possible without discomfort. Looking at glare can result in squinting, tired eyes and headaches. Polarized lenses minimize or eliminate the effects of glare vs. non-polarized sunglasses hence reducing these negative side effects. - Polarized sunglasses are normally not as darkly tinted as regular sunglasses. Regular sunglasses typically use dark lenses as a means to reduce the effects of glare. The darkened lenses in regular sunglasses actually darken your entire vision while polarized lenses allow more of the "desired" light to get through. I equate it to the fact that the sun doesn't bother you at night but you also can't see as well either. - As an Ophthalmologist, I and most members of my profession recommend polarized sunglasses as the best means to maintain the health of your eyes while exposed to the sun. I feel that you are getting more value for your money when you purchase polarized sunglasses.

Why do polarized sunglasses cost more? There is an increased cost to the manufacturing process associated with sandwiching the membrane between the two outer lenses. Although recent technology has improved this process and made the resultant lens much clearer and of better quality, it is still more costly to produce polarized lenses.

What about UV (ultraviolet)?

What is UV or ultraviolet radiation? UV or Ultraviolet radiation is comprised mostly from the invisible light spectrum that falls between 100 and 400 manometers (nm). UV is divided into three segments. These segments are designated as A, B, and C. The last segment, UV-C (below 280 nm), is not considered a threat since it is filtered by the earth's ozone layer and as such never reaches earth. Exposure to both UV-A and UV-B does pose a risk to both the short term and long term health of your eyes. Where does UV come from? The primary source of UV is from the sun. However, there are other sources (artificial) such as, sun lamps typically found in tanning parlors, the flash from welding machines, high-intensity mercury vapor lamps found in sports stadiums, lasers and xenon arc lamps to name a few.

How does UV affect my visual health? On the short-term side, some of the typical effects of excessive UV exposure are known as "welder's flash" and "snow blindness". These conditions are both caused from the cornea being exposed to excessive amounts of UV radiation over a short period of time. Just think of it as getting your eyes sunburn. Similar to sunburn, it does not feel painful right away but after a short period of time, the pain gets extremely intense and then disappears after a few days. The sensation has been described as a feeling similar to having sand in your eyes. These symptoms are typically caused by long hours of unprotected exposure to the sun in the snowy environments or at the beach, etc... . Red eyes, tearing, and eye irritation are all symptoms of short term over exposure. These symptoms are not normally associated with permanent vision damage. The long-term effects of UV radiation slowly cause visual impairment over long periods of time. Hence, these changes are not immediately noticeable but are far more devastating to the health of your eye. PolarShades recommends that you use sunglasses with 99-100% UVA and UVB protection. This protection is normally 100% for polarized sunglasses due to the functionality of their optical membrane material