This option is recommended for high prescriptions. High prescriptions are typically considered a Sph over |4.00| or Cyl over |3.00|. 1.67 High Index lenses are 30% thinner than glass or plastic and more optically true than glass, CR-39 and polycarbonate. They are also 100% UV-A and UV-B blocking. Included Anti-Reflective and Super Hydrophobic coatings reduce glare, improve night vision and make your glasses easier to clean.