Lenses that are treated front and back with a clear, scratch-resistant coating have a much smoother surface that is more resistant to scratching.
The coating does not interfere with how the lens functions and does not affect vision. Though an anti-scratch coating is not 100% scratch-proof, but it helps to prevent minor scratches that can easily happen to a regular lens. These minor scratches can damage the surface of the lens and impair vision. An anti-scratch coating acts as a protective layer thus making the lenses more durable and safe.

Polycarbonate is the material favored by most sports eyewear manufacturers because it's very light and shatterproof, which is an impressive impact resistant lens. Being flexible is what enables it to absorb energy without fracturing. Polycarbonate lenses are more impact-resistant than plastic or glass lenses. PC lens provide a very high degree of eye protection.