This goes into sensory deprivation / control. With simple contact lenses, one could inhibit the eyesight of the wearer, or even make them completely blind. This, of course, can be taken further into high-tech stuff, by making the lenses displays. That way, someone else can control exactly what the wearer is actually seeing right now, without the wearer actually being able to look away, as they are directly on top of their eyeballs. More Details