Variations in the local refractive correction of the eye across its entrance pupil

We show that normally a spherocylindrical lens will correct the local refractive error of any small area of the pupil. In general, however, the correction varies with position across the pupil. Plots are given to illustrate this variation for 2 typical individual eyes and for the average of 11 eyes, as calculated from the corresponding wavefront aberrations. The implications of these results for the design and use of objective optometers are briefly considered.