POLARISED SUNGLASSES

What is Polarised Light?

Ambient light or the light we see consists of light waves that vibrate in a number of different directions.  However, these light waves are often reflected off 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 intense uni-directional waves are known as “polarised” light waves.  Polarised light waves are many times brighter that non-polarised light and are otherwise known as “glare”.

Benefits of Polarised Lenses

Polarised lenses block out a lot of scattered and reflected light.  For example, if you look at water in a pool with a standard lens, it is difficult to see an object under water clearly.  This is due to the fact that the surface of the water is reflecting light from all different directions.  Polarised lenses, however, filter those reflected rays so you can see below the surface of the water much more clearly.

Polarised Lenses are manufactured using a special material designed to absorb polarised light waves before they reach your eyes, however, still allowing most of the ambient light through for better visual acuity.  This optically engineered polarising material is a very thin membrane sandwiched between two pieces of optically ground lens material to filter out 99 percent of all reflected light for maximum eye protection.

Polarised lenses have a laminated surface containing vertical stripes.  These stripes only allow vertically polarised light to enter the wearer’s eyes.  Glare is eliminated because the horizontally polarised light waves cannot bypass the polarised filter.  Light reflected from surfaces such as flat road or smooth water is generally horizontally polarised.  This means that, instead of light being scattered in all directions in more usual ways, reflected light generally travels in a more horizontally oriented direction.  However, there are some limitations to the use of polarised lenses, some drivers discover that polarised lenses can cause distortions in liquid crystal displays (LCDs).  Onboard clocks and other instrument displays may be temporarily unreadable.

Polarization is like a chemical venetian blind which rearranges light and lets you see "through" glare. 100% Polarized lenses are the only truly effective way of eliminating glare. Water, fog, rain, snow or early morning dew, have reflective properties, which enhance reflected glare. In addition to water, glare is also a problem on roads and highways.

Though polarized sunglasses improve comfort and visibility, there are some instances when these lenses may not be advisable. One example is downhill skiing, where you don't want to block light reflecting off icy patches because this alerts skiers to hazards they are approaching.  Some wearers who use polarized lenses in snowy areas may find that they lose some contrast between snow and shadows. Fishermen and drivers seem to derive the most benefit from polarized lenses because they deal with mostly horizontal surfaces. A fisherman wearing polarized sunglasses can see below the surface of the water to search for schools of fish or hidden obstacles. Drivers are no longer affected by a constant reflection of light from their hoods or the road ahead.

There are some limitations to the use of polarized lenses, however. Because the polarizing stripes reduce the amount of light entering the eye, polarized lenses cannot be used for regular eyewear with clear lenses. Prescription sunglasses can be tinted a very light gray to accommodate the polarized laminate, but most contact lenses cannot.

How do polarized sunglasses work?

Light reflected from surfaces like a flat road or smooth water is generally horizontally polarized. This horizontally polarized light is blocked by the vertically oriented polarized filter in the lenses.

There is some debate on the effects of polarized lenses on snow-covered surfaces. Some say they can reduce the intense glare that is caused by sunlight reflecting off snow.

We find that they're not satisfactory for sports such as downhill skiing because they may not provide the contrast the eye needs to distinguish ice patches and changes in the terrain quickly. Try mirrored sunglasses instead.

Also a polarized filter will sometimes react with windshield lamination and tinting (as well as Aircraft canopies) to create blinds spots and make it difficult to read LCD instrumentation. We'd suggest a non-polarized lens if you spend a lot of time driving or flying.

Why Protection Is Necessary

As people spend more time outdoors, concern regarding the potentially harmful effects of sunlight increases.  While many people appreciate the importance of using sunscreens to protect their skin, not everyone is quite so careful about choosing sunglasses.  The best protection for the eyes against ultraviolet radiation (UV) is optical quality sunglasses.

You might also be interested in learning about Photochromatic Sunglasses.