The UV420 CUT lens is able to block harmful HEV high energy visible light in the 400 to 420 nm spectrum which causes oxidative stress and deterioration of lutein in your eye. Lutein is said to act as natural sunglasses. It is present as a pigment in the retina, a crucial part of the eye that receives light and allows you to see. The UV420 lens prevents cumulative macular degeneration by blocking harmful light and has an anti oxidant effect. Lutein is destroyed when it absorbs harmful light. Its presence in the retina is limited and, because the body cannot make lutein, it can only be replaced by eating lutein rich food.