Board Thread:Questions and Answers/@comment-5836726-20131016212310/@comment-146.52.150.76-20140106164236

He needs direct eye contact to use his Geass, the exception are normal glasses.

In R2 Leouch wears lenses, which keep back his Geass power. But he can't use the Geass if the other person is wearing glasses.

evidence: In R1 he couldn't use the Geass when he had the mask on! He had to open the mask on the side.