On The True Shape of the Optical Point Spread Function in the Human Eye

Abstract

There are basically three different approaches to assess in vivo the optical quality of the retinal image of the eye [1], but none of them is able to provide a reliable estimate of the true shape of the Point Spread Function, PSF. Interferometric methods can provide accurate estimates of the ocular MTF, but to obtain the PSF the Phase Transfer Function, PTF is also needed. The PSF can be computed from wave aberration data. However, the reliability of these computations is unclear, since in practice, it is difficult to measure higher order aberrations, which may have an important contribution to the optical quality of the retinal image. Finally, the double pass method directly provides the aerial PSF, which, however, is affected twice by ocular aberrations. Furthermore, it has been recently shown [2] that the double-pass aerial PSF is actually the autocorrelation of the retinal PSF, which means that the single pass MTF can be accurately estimated, but the PTF is lost. Therefore, the true PSF can not be estimated, and odd aberrations such as coma are symmetrized in the double passage so that they can not be determined.