How do sunglasses filter ultraviolet rays?

A special clear coating is applied to the lenses, either on the front or back of the lens, or sometimes both sides. It's a transparent coating and can be applied to any colour of lens including clear. The UV-filtering effect, however, is more complex. UV-filtering lenses are coated with special chemicals that allow light to pass through them, but reflect away UV. The most complicated sunglasses are prescription sunglasses. These are sunglasses that not only protect from light and UV, but also work like normal glasses to correct the eyesight.