By Kevin Styles
Photochromatic glasses turn dark by exposing the glasses lenses to ultra violet light.
There are several common brands of photochromic glasses that you can source online, for example Transitions (which is the market leader) or Reactions, Reactolite or Graduations prescription glasses.
They were originally introduced made of glass, but today most transitions glasses are made out of plastic. The way that the glasses lenses change from light to darl is essentially the same – by embedding or coating the lenses with microcrystalline or molecular organic...