Lenses made from impact-resistant materials such as polycarbonate or Trivex are recommended for children's glasses. Polycarbonate is a soft material that scratches a little bit easier but is safer for children. Trivex, on the other hand, provides better overall vision. You can also use a scratch-resistant coating to add an extra layer of protection. Photochromic lenses can get darker or lighter and are suitable for children when outdoors. Considering the right frame for your child's glasses could also be a big help.