Photochromic, or “transition”, lenses darken when exposed to sunlight or ultraviolet (UV) light. Once the light source is removed (for example by walking indoors), the lenses will gradually return to their clear state. Indoors and at night, these lenses carry no tint making them as clear as ordinary lenses.
“Transition” lenses are available in gray and brown. Gray lenses transmit color evenly for true color recognition; brown improves contrast and depth perception. These lenses can also be made in almost any prescription and lens material.
Additionally, photochromic lenses block 100% of UV rays. This provides protection for everyone, especially children given that they receive 3 times the annual UV exposure as adults.