Polarized lenses reduces reflexes
An effective protection
It's both comfortable and healthy to use sunglasses of good quality. Sometimes it's even necessary to protect the eyes. In very bright environments, especially when we also are exposed to reflected ligth from water or snow.
It's possible to get over exposed to UV light only from reflections. The UV light can cause damages to the cells in the cornea, making it uncomfortable to see and increased tear flow. This condition is often called snow blindness, the correct term is photokeratitis. Snow reflects approximately 80 % of the UV light, thus sunglasses is important even with an overcast sky since UV light can reach through the clouds. The UV intensity also increases with altitude. This makes it extremely important to protect the eyes when skiing in the alps as an example. The symptoms often dissapears within a day or two if the source is removed but can be really uncomfortable. If exposed too long time, permanent damages to the eyes can occur.
Parallel lines eliminates reflections
The polarized lens can be described as containing many small lines. The lines absorbs the light that is vibrating perpendicular to the lines. Since reflected light from horizontal surfaces only vibrates horizontally (called polarized light), almost no reflecting ligth will transmit through a polarized lens. However, if you tilt your head to the side, the reflected ligth will be transmitted.