Figure 3.

Encircled energy for aberrated eye and for cylinder approximation. (A) The point-spread function (PSF) for the cylinder function we used is shown in the upper panel. The PSF for an eye with typical aberrations is shown in the lower panel. Modeled pupil diameter was 3.5 mm, relative distance was −0.5D, and the light was equal-energy white. The red circles represent the circles used to calculate encircled energy. They have radii of r. (B) Diameters of circles that encircle 50% of the energy as a function of relative distance. A relative distance of 0 corresponds to perfect focus. The three sets of curves are for pupil diameters of 7, 4, and 2 mm. (Note that the PSF in the lower left panel is not for a condition on one of the green curves; instead, it lies between the 2- and 4-mm curves.) The solid green lines represent the encircled energy for the aberrated eye. The dashed gray lines represent them for the cylinder approximation.