High index lenses rated at 1.67 high-index are great for many but people with prescriptions over +/-6.00 sphere they are a must have. They will make your glasses Thinner and lighter for better performance and aesthetics.
Thinner lenses have three advantages:
3- Do not magnify or minify your eyes when seen by others as much
The suggested prescription range is +/-6.00 to +/-8.00 sphere.