Fig. 16. A graphic representation of what happens to an image of an object in focus superimposed on an out-of-focus image. This would represent the type of image produced by a bifocal lntraocular lens. Unlike the defocused curve which has lost all edge contrast. these images retain edge sharpness through contrast declines. (Atebara N: Image Contrast and the Optics of Multifocal lntraocular Lenses. Senior thesis, Harvard Medical School, 1991)