A wavefront device produces adjustable amplitudes in optical path differences and adjustable axis orientation angles. two substantially identical wave plates have a wavefront profile of at least the third order Zernike polynomial function which are not circularly symmetric, as denoted by Z(i,j) where i≧3 and j≠0. The wave plates are mounted in rotatable mounts with their optical centers substantially aligned with each other. An subjective wavefront refraction instrument and method are provided to correct low and high order aberrations of the eye, using the adjustable wave plates that have astigmatism and higher order Zernike function optical path difference wavefront profiles.
