ABSTRACT The modulations transfer theory has been applied to a rigorous investigation of the effect on the retinal image of several types of contact lenses designed to help in presbyopia. Among those investigated are the segmented bifocal, the two‐curve bifocal, and pupil restriction. The effect of these various lenses on the extension of the depth of field is illustrated, and it is shown that the restricted pupil lens makes a significant contribution to the depth of field at an acceptable sacrifice in brightness.
Newton K. Wesley (Mon,) studied this question.