I added a small color setup to choose between optical and non-optical glasses. The non-optical version does have less distortion when you render with less than 2000 samples (I prefer that, because I do not want to wait a week before the hair-rendering is done). A RGB color wheel is also attached to make sunglasses. The next pictures show the differences. Of course you can also take this setup for the lenses, if you import the glasses from MH.
Next, poor Leska, blind like a bat

The way to get the result with the .blend attachment:
- load or import your character in Blender (cycles mode)
- append the blend-file, select the group "glasses".
- the glasses should be quite okay, when you export the mhx2-character without modification in scale. If not, resize the glasses. Then put them in place. Switch off the hair, to see what you are doing
- the ear-pieces are designed in a way you can rotate them.
- insert the armature three times in the front and both ear-pieces of the glasses. The vertex-group "head" is available and set to a value of 1.
- select a color you like and optical shading or non-optical one.
If your character does not need the glasses, put it somewhere, that also works fine ...

I hope nothing is missing in the zip-file. It is my first .blend upload (build on an older Blender 2.71, but that should not make a difference to the newest one).