Lenses which block 99% or 100% of UVB and UVA rays.
Lenses that meet ANSI Z80.3 blocking requirements. (This actually refers to the standards, which are set by the American National Standards Institute.)
UV 400 protection. (These glasses are good to block light rays that have wavelengths up to 400 nanometers. It means the eyes are suitably shielded from even the tiniest of UV rays.)
It is important to choose the right color for your sunglasses.
The coating of the sunglasses plays a very important role in blocking the ultra violet radiation from the sun, so it is clearly a myth that darker lenses are actually more effective than the lighter ones. However, in certain respects, the hue of the sunglasses is very important in color perception.
For example, rose or yellow tinted lenses can cause a problem at times because distinguishing changes in traffic lights is a problem for people wearing them. However, colors like gray, brown and green lenses are good because they minimize color distortion, and hence certainly a better choice, especially, while driving.
Polarized lenses are good for people who spend considerable time inside water