Polarized lenses are special filtered lenses that block glares from light reflecting off shiny surfaces (like water) better than other types of sunglass lenses. Polarized sunglasses can be helpful outdoors, especially for driving because they reduce glare-causing reflections from flat surfaces, such as the hoods and rear windshields of vehicles and light-colored walkway.

Sunlight scatters in all directions. But when it strikes flat surfaces, the light that is reflected by the surfaces tends to become polarized — meaning the reflected light beams travel in a more uniform (usually horizontal) direction. This creates an annoying and sometimes dangerous intensity of light that causes glare and reduces visibility.

Polarized lenses have a special filter that blocks this type of intense reflected light, reducing glare and discomfort. Though polarized sunglass lenses improve comfort and visibility, you may encounter some instances when these lenses cause interference. One example is polarized lenses reduce the visibility of images produced by liquid crystal displays (LCDs) found on some digital screens, such as bank automatic teller machines (ATMs) and the screen on your smartphone (depending on the type of screen technology used). Despite these exceptions, polarized sunglasses offer great advantages when it comes to decreasing eye strain and discomfort in bright sunlight.