Abstract: A pair of spectacles adapted for viewing stereoscopic images is disclosed. In accordance with the invention, within the body of the spectacles, there is provided a pair of mirror assemblies each of which has a pair of substantially parallel mirrors arranged in periscope-type manner so that light is shifted laterally between the mirrors. The spectacles include an adjustment mechanism which simultaneously adjusts one of the mirrors in each assembly by an identical amount, but in the opposite direction so that the two pairs of images seen by the wearer become superimposed, whereupon the wearer immediately perceives a stereo or 3D image in the region where he perceives the superimposition to occur. Means are also provided to allow the separation of left and right casings (10, 12), each housing one of the mirror assemblies and one set of apertures, ti be adjusted. This allows the interocular spacing to be varied.