Photochromic lenses — lenses that are clear indoors and darken when exposed to sunlight — offer a convenient way to protect your eyes outdoors from UV rays and bright light without having to carry around a pair of sunglasses.
The molecules in photochromic technology work by reacting to UV light. However, temperature can have an effect on the reaction time of the molecules.
When the lenses become warm the molecules speed up and become more reactive. This means that they will fade back faster. It can also mean that if you’re outside on a hot sunny day, but sitting in the shade, your lenses will be quicker to detect the diminished UV rays and lighten in color.
In general, photochromic lenses are both for indoor and outdoor activities lens. In the room or at night, the lenses color are basically transparent, the same as the ordinary lenses, like high light transmission performance, relieve visual fatigue,make you see the world more clear. Lens under the action of ultraviolet light in the sun color, ultraviolet dark color change, deep, shallow light-colored ultraviolet light, isolated from UV damage, anytime, anywhere to protect your eyes.
Photochromic lenses, when exposed to sunlight/UV rays, will on average take approx 30 seconds to a minute to darken and will continue to darken for a further 10 minutes to full sunglasses tint/shade, returning to an almost clear state within 2 minutes and fully cleared within 5 minutes although excess temperature will affect this.