Effect of non polarized sunglasses on the human eyes

Polarized glasses are known to block the harmful UV rays of the sun. 
They work by blocking reflected light as reflected light tends to have 
a certain degree of polarization. What this means is that when light 
reflects on a surface it changes its propagation which is different 
to the ambient light. A polarizing glass blocks this light that 
appears horizontally to the viewer. If you invert your glasses, 
you can see that the glasses block ambient light.

These glasses have minute grooves that prevent reflected light 
from entering your eyes. Of course, this can be exploited to 
block other light as well. Most polarized glasses are darkened as well.
This creates a sensation of coolness by blocking excessive light but
this also dilates the pupils which allow more light to enter the eyes.

But there are glasses in the market which are dark but not polarized.
These glasses are dangerous as they dilate the pupils which allows more 
light to enter but as they are not polarized, they allow glare as well.
This can damage the eyes in the long term. Polarized glasses have been 
proved to block UV rays unlike dark glasses.