what does hard coating on glasses do ?

[Barnum Island]

what does hard coating on glasses do ?

[Barnwell]

The hard coating is used to help prevent from scratching so that the glasses are more resistant to scratching.

[Baroda]

Hard coating are usually used on eyeglasses with plastic lenses. You know , today most of eyeglasses lenses are made of plastic lenses. The plastic lenses is lighter and safer than other glass lenses. But the plastic easy to get scratches. So, we need hard coatings which can used to protect the plastic lenses. They can toughen the surface greatly.