How can you make a costume with opaque eye covers? Basically, my question is: is it possible to make a real life costume in which the eyes of the person wearing it are fully covered with opaque material but the person can still see through it, and if it is possible, how can you do it?

In the case of Dead Pool, his eyes are covered with what seem to be white covers that are part of the mask. I imagine this is to conceal his identity but it's never explained how he can see through that thing. 



Is this even possible to construct at home (say for a Halloween costume)? What material would it have to be for it to be transparent only in one direction?
For this Lego Batman costume, we covered the eyeholes with white gauze (ok, actually patches cut from some old pantyhose). Vision was only very slightly reduced -- much more so by the small eye openings (and loss of peripheral vision) than by the gauze.