photochromic sunglasses can turn dark automatically when they are exposed to the UV rays and go back to clear when they are indoors. There are some brands thay offer the best photochromic sunglasses. One of them is the Transitions lenses which offers photochromic sunglasses with light lens material like plastic, polycarbonate, Trivex and high-index plastics. LifeRx is another brand that offers photochromic sunglasses.
The most popular brands of photochromic lenses today is owned by Transitions Optical. This is the reason why some people called photochromic lenses "transition" lenses.
And Transitions Optical partners with other lens manufacturers to make photochromic versions of their lenses.
Besides, Corning Inc also create their first mass-produced photochromic lenses in the 1960s. And right now, their photochromic lenses remain popular today.
In addition, LifeRx photochromic lenses are also very popular because their lenses darken in less than one minute.