Longitudinal Chromatic Aberration discussion on diffractive intraocular lenses

Diffractive multifocal IOLs show chromatic aberration especially along the axis (LCA-longitudinal Chromatic aberration) but also out of the optical axis. These chromatic aberrations are the results of the refractive chromatic properties of the lens, driven by refractive indexes involved into the light path and the diffractive profiles. Refractive effects are mainly controlled by the biomaterial Abbe number while diffractive effects are controlled by the topography of the diffractive pattern. The insertion of a multifocal diffractive lens after crystalline lens extraction may significantly modify the chromatic aberration of the pseudophakic eye. Chromatic aberrations are inducing vision losses due sharpness reduction of any object edges. The contrast sensitivity as much as the visual acuity are then reduced. This has been proven with measurements optical benches. Diffractive and refractive effects act in an opposite way and can in principle be compensated. However rules to creates an achromatic lens based on refractive-diffractive lens are quite complex because topology, dioptry , abbe number,… In this study, we will investigate the effect of wavelength on the through-focus modulation transfer function (MTF) and diffraction efficiency for different pupil apertures and different diffractive intraocular lenses. Pin-hole effect will also be discussed and addressed with the point of view of chromatic effect.