Quote Originally Posted by Ryllharu
By "special," C.C. could simply mean that the lens is polarized or something similar so Lelouch can actually see out of it. He said "opaque." What her next line implied about it possibly not working if his Geass gets any stronger is that even blocking his eye might not work, or more benignly, that he'll get the effect in both eyes.
Now based on the eclipse dialog is completely different then the GG conversation. Lelouch in the eclipse version.
14:35-15:08

C.C. It will block your Geass that's unstoppable now.
Lelouch If all it takes is to block optic information, then a normal color contact would work...
C.C. Enough with the prying talk.
C.C. As you conjecture, that's a special one.
C.C. However if your Geass becomes stronger then it is now...
Lelouch: I will end it before that happens...
Lelouch ...This game!


Its clearly stated it doesn't just block his vision and a normal contact wouldn't work. Its also clear that no part of his eye is glowing with the Geass while the contact is on where it would based on the size of the contact vs the size of the eye though in anime thats pretty moot.

So if you don't believe that means the Geass is being blocked by the contact in a way thats beyond simply a visual blocker what do you think she means when she says stop prying its special after being asked if all it does is optically block the Geass.