Photochromic Lenses
Photochromic lenses have a special chemical coating that makes them change to a dark tint in the sunlight and turn clear indoors. Photochromic lenses are great for people who do not wish to carry a separate pair of prescription sunglasses. It is important to recognize that these lenses do not darken as well while driving a car. The windshield prevents most of the UV light from reaching the lens.
You may have heard this type of lens referred to as Transitions Lenses. The Transition lenses are available in 4 different designs. To find which design is best suited for you and your needs, visit Transitions.com to see this comparison chart.