In exemplary implementations of this invention, a bi-ocular apparatus presents visual stimuli to one eye of a human subject in order to relax that eye, while measuring refractive aberration of the subjects other eye. Alternately, a monocular device presents stimuli to relax an eye while testing the same eye. The apparatus induces eye relaxation by displaying virtual objects at varying apparent distances from the subject. For example, the apparatus may do so by (i) changing distance between a backlit film and a lens (ii) using extra lenses (iii) using an adaptive lens that changes power (v) selecting distinct positions in a progressive or multi-focal length lens (vi) selecting distinct optical depths by fiber optical illumination (vii) displaying a 3D virtual image at any given apparent depth or (viii) display both a warped version of the real world and a test image at the same time.
