These lenses remain tinted all the time (as oppose to photochromatic lenses) and are available in plastic, high index, polycarbonate and glass materials. Light coloured tints are used for cosmetic effects, as well as indoor glare. Dark coloured tints are used for protection against the sun’s rays, i.e. sunglasses.
Lenses can be tinted all over or be graduated i.e. fade from dark to light, usually fading from the top down.