Glare

No matter how dark the tint of your glasses or how efficient the lenses are at blocking UV, they won't necessarily stop glare. Glare is sometimes caused by reflected light - often from water or a road surface - and can only be reduced with polarized lenses.

Polarization completely blocks light rays on the horizontal axis only and is highly effective when applied to sun lenses. These are specially useful for those involved in snow and water sports since they remove the surface reflections that make seeing in these environments so uncomfortable.