If you have hard resin lenses (CR-39), you should consider getting a scratch resistant coating. Resins and plastics are more susceptible to scratches than glass. Scratches damage the cosmetic look of the lenses as well as their performance. With a scratch resistant coating, you don’t have to worry so much about minor scratches on your lenses.
Another advantage of scratch resistant coatings is that most coatings come with a one-year warranty. They are a great investment to prevent minor scratches. However, it is important to remember that scratch resistant does not mean scratch-proof. All lenses are susceptible to scratches.