The photochromic lenses used in Serengeti sunglasses make them ideal for changing conditions. They automatically lighten or darken to an optimal viewing level for anything from bright sunlight to dark cloudy weather. This technology is engineered into the glass so it will never wear off or wear out. Spectral Control® is a patented lens system that selectively filters light waves to improve contrast and reduce eye fatigue. It provides a superior high-definition view – images are clearer and colors pop. Lenses reduce distracting blue light that causes eyestrain and eye fatigue. They also cut through haze and glare for optimum visual clarity, even at a distance. Polarization keeps your eyes relaxed and focused by eliminating glare and 100% of UVA/UVB rays.