Photochromic lenses adapt automatically to your environment. Indoors the are clear and help filter harmful UV Blue light from your computer, tablet, and smart phone. Outdoors they are activated by ultraviolet light and darken to meet the intensity. In other words the brighter the sun the darker the lenses become. In moderate sun they will become the perfect shade in between. For the ultimate experience the Magz photochromatic lens is the perfect Magnetic reading glass for all occasions. Magzeyewear.com also offers a full range of prescription lenses in our magnetic frames and offer Transition brand photochromic lenses in those as well.