They work, no batteries required. These are different from 3D glasses by the way, these are meant to train lazy eye aka amblyopia. I mean you could use them as 3D glasses, but you'd have to wear them upside down. You'll want to use these with red and green filters over whatever you're watching/reading, so each eye can only see part of the content. This forces your eyes to work together. The problem with lazy eye is that they're not doing that.