Every lens we sell includes a Scratch Resistant Coating and an Ultra-Violet protective filter. Other options would include an Anti-Reflective coating or mirror coat for sunglasses. Below is a demonstration of the view through lenses without an Anti-Reflective coat and to the right, lenses with an Anti-Reflective coating.
The Anti-Reflective coating allows more light to pass through your lenses, which does three things; 1) Reduces eyestrain associated with computer monitor glare and glare from reading, 2) Enhances vision at night and will eliminate light halos around car headlights and streetlights, 3) and it makes the lenses 'disappear' on your face. This is a wonderful coating for anyone, including children, as the Anti-Reflective coating features a 1-year warranty against scratches.
A mirror coat is used only as a glare and brightness reducer on sunglasses.
A tint may also be added to any lens for a variety of purposes, such as cosmetic appeal, glare reduction, or basic sunglasses.