Incorporation of directional effects of the retina into computations of optical transfer functions of human eyes.

Two-dimensional optical transfer functions (OTF's) of individual human eyes are computed from the retinal images of a point test object, using a phase-retrieval method. The retinal reflection directionality effect is included in the computations by means of an apodization pupil, and subsequently the Stiles-Crawford effect is also considered. The modulation transfer functions obtained when the retinal reflection directionality effect is considered show lower values of the modulation; on the other hand, their two-dimensional form and the corresponding phase transfer functions remain practically unchanged. The importance of the Stiles-Crawford apodization depends on the wave aberration of the individual subject, but in general it produces an improvement in image quality, and the modulation transfer function becomes more symmetrical.