Question: what is the difference between 1.57 and 1.61 index lenses?
Answer: In addition, the 1.59 pure polycarbonate lens tends to scratch more easily than the 1.50, 1.57, and 1.53 lenses, because it's a softer lens material. The 1.61 high-index polymer single-vision lens provides a thinner lens for stronger prescriptions than mid- and standard-index optical lenses do.