Computation of the Modulation Transfer Function (MTF) for Progressive Addition Lenses (PAL's) and Its Applications

For the examination of a patient’s visual characteristics, astigmatism and mean power errors or visual acuity (V. A.) are basic optometric quantities. Unfortunately those quantities do not incorporate the pupil diameter as a variable but rather for an average fixed size. Moreover V. A. is measured for spherical and cylindrical trial lenses only. For PAL’s the pupil diameter is important because of the gradient behaviour of astigmatism and mean power. In this paper we introduce a new quantity which incoperates the pupil size. This quantity, which we call relative optical performance (R. O. P.), is based on the modulation transfer function (MTF) that takes a finite aperture into account.