Glass must be hardened by chemicals or heat tempering to meet U.S. Food and Drug Administration standards for impact resistance. Glass has the best optical clarity of all the lens materials and many purists swear by it. Many of the leading polarized sunglass manufacturers such as Maui Jim, Ultrasol, Action Optics and Hobie use glass lenses in some or all their lenses. Lens Polarization - Polarized lenses have the benefit of filtering out reflected light and glare off water, pavement and snow. This lens works great for fishing, boating, driving or any other glare intensive activity.
Polarized lenses are the best way to eliminate both glare and UV light.
The principle of a polarized lens can best be described by observing the use of a venetian blind. The blind blocks light at certain angles, while allowing light to transmit through select angles. Be sure to check out the nice polarized lines from Maui Jim, Visi, Costa Del Mar and Ocean Waves. Photochromatic Lenses - Photochromic lenses have an adjustable tint that changes with the amount of available light. Note that the photochemical response does not happen instantaneously.