Photochromic lenses are optical lenses that change transparency depending on the current light condition. The photochromic lens darkens in more intense light conditions in order to protect your eyes. In low light conditions the lens becomes more clear. This reaction allows your eyes to have great vision in all light conditions. 

Photochromic lenses are transparent to light without a ultraviolet component, such as artificial light. When exposed to ultraviolet (UV) rays, such as direct sunlight the molecules inside the lens undergo a chemical process that change the lens to a more dark color. This process limits the amount of dangerous rays to reach your eyes. 

This process will keep your eyes comfortable and safe in all conditions, allowing to enjoy the mountains every day all day!