How Do Polarized Lenses Work?
Light reflected from surfaces such as a flat road or smooth water generally is horizontally polarized. 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. This creates an annoying and sometimes dangerous intensity of light that we experience as glare.
Polarized sunglasses cut glare and haze so your eyes are more comfortable and you can see better.
Polarized lenses contain a special filter that blocks this type of intense reflected light, reducing glare.
Though polarized sunglasses improve comfort and visibility, you will encounter 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.
In addition, polarized lenses may reduce the visibility of images produced by liquid crystal displays (LCDs) found on the dashboards of some cars or in other places such as the digital screens on automatic teller (bank) machines.
With polarized lenses, you also may be unable to see your cell phone or GPS device. Boaters and pilots also have reported similar problems when viewing LCD displays on instrument panels, which can be a crucial issue when it comes to making split-second decisions based strictly on information displayed on a panel.
However, for most other sports and activities, polarized sunglasses offer great advantages. And today, many polarized lenses are available in combination with other features that can enhance outdoor experiences.
--Source, All About Vision April 2012