There are several places to look for the Cartier logo on authentic glasses. The logo normally appears on the lenses, the nose piece and the temple inserts. Counterfeit glasses often omit or poorly replicate the logo on any of these three places.
The Cartier logo on the lenses is etched or stamped. It has a texture that counterfeiters do not bother to replicate. Knock-off glasses include the logo with a cheap screen print, so it lacks the texture from the authentic glasses. In order to determine the real from the fake, run a thumb over the logo to see if there are ridges.
Most counterfeiters do not include the logo on the nosepiece because it is an interior detail that many overlook. The Cartier double C should be stamped on the inside of both nose pieces.
Finally, the Cartier logo on the temple inserts is made of gold and is hand-engraved. The writing and gold plate are always centered on authentic glasses. Imitations are detectable if they are not centered or not made of real gold.