"For an item to reveal truths, but have it's own truth unobservable through it's own use, is the stuff of thinker's late nights spent restlessly thinking. "
That is damn good line.
I good see these item falling to players hands for the period of an adventure or something, you send the players through a series of events and locations once, then you have them revisit the components of these events and the locations with the glasses. These could certainly be a quest item, or item loaned to the PCs.
An item that bends light for the light quest...nice