I just received my Spider-Man suit from Zentai Zone and although it is good for the price, I was not happy with the white gauze material they used for the lenses. It is quite easy to see the eyes through this material.
So I had a think about it and in the end I cannibalised a pair of metal speaker grilles off of some Dell speakers I had knocking around. Then I cut up a clear PVC bag (bought specially!) and painted one side of the grille white and the other black. After the paint had dried I placed my PVC cut outs either side and then glued the edges together.
This gave me two benefits, first, I get the glass effect look of the lenses outside and inside my eyeball is not scraping against a painted metal grille.
Then came the stressful task of unpicking the stitching that held the white gauze material in place on my mask. This went fairly well and luckily left me with a "pocket" of inner and outer material to fit my new lenses into and then to be able to glue it into place between the lens and the inner mask.
All in all it looks not too bad. I can't see my eyes anymore!
Have a look at the comparison image I threw together...
Here is the mask complete and original size, which is why I enclosed it in spoiler tags