Sunlite Photochromic Lenses darken on exposure to ultraviolet radiation. In the absence of UV (for example while walking indoors), the lenses will gradually return to their clear state. Sunlight consists of 3 types of UV rays. UVA and UVB rays are most commonly found in the atmosphere and this poses great threat for the eyes. Needless to say complete protection is required against these harmful rays to avoid eye problems. Sunlite Photochromic Lenses thus ensure that your eyes remain protected, while providing you convinience.