Scratch resistant coating: The plastic lens material is relatively soft and is easily scratched if it is not coated with scratch-resistant material. Even with scratch-resistant coating, your lenses will become scratched through normal use over time. The coating material is a much harder plastic compound that is applied to the lens, but it too can be scratched. Once scratched, a lens cannot be repaired or "buffed" free of the scratch. Scratch coating cannot be guaranteed; it is simply added protection from scratching, and it will inevitably scratch over time.
Ultraviolet protection (UV) Coating: The sun radiates ultraviolet waves, which are extremely damaging to the human eye and skin. Lenses with ultraviolet protection help prevent the harmful UV radiation from touching your eyes. Polycarbonate, high-index, photochromic, and polarized lenses all automatically contain UV protection.
Anti Reflective (AR) Coating is an extremely thin layer of film that is deposited on either the front or the back surface of the sunglass lens that virtually eliminates reflections from the back of the lens. AR coating makes it easier for other people to see the wearer's eyes, and it makes it easier for the wearer to see through the lens. AR coating is very useful for night driving and for people who look at computer screens. Lenses with AR coating must never be cleaned dry, as this can scratch the coating. The best cleaner is one that is made especially for AR-coated lenses.