The present invention features a method and device for measuring characteristics of the human eye, particularly spherical refractive error. The device comprises a recorded hologram of an array of elements each bearing an identifying indicia. When the reconstructed hologram is viewed by a subject each of the indicia appear at different virtual distances. By indicating which indicia appear to be in focus the spherical refractive error of the eye and the range of accommodation is determined. The indicia are conveniently numbers that indicate dioptres. Also described is an apparatus for working the method. The apparatus can also be used to determine cylinder power and axis, binocular refraction and stereopsis.