Ocular Aberrations and their Measurement

As we described in the previous chapter, the first step in the visual process is the formation of an image on the retina by the eye’s optics. Thus, the optical quality of the eye imposes the first limit on spatial vision (Charman, 1983). It has been long known that the normal human eye suffers from many aberrations that degrade retinal image quality (Helmholtz, 1896). As shown in Fig. 1, a point of light on the retina would emerge as a ideal, planar wavefront in a perfect eye. However, normal eyes possess optics with inferior quality, rendering a point source of light on the retina as an aberrated wavefront that exits the pupil of the eye. Hermann Von Helmholtz (1962) commented on the eye: