Properties of a new hydrophobic diffractive trifocal intraocular lens: linear chromatic aberrations (LCA) by optical simulation and optical bench testing

Purpose:

Impact of the IOL raw material Abbe number on diffractive trifocal optical outcomes in terms of light energy partition between the three foci, modulation transfer function (MTF) and linear chromatic aberration (LCA).

Setting:

Space Center Liège (Centre Spatial de Liège), University of Liège, Liège, Belgium

Methods:

The difference between hydrophilic and hydrophobic materials doesn't rely on biocompatibility only, but also influence some optical properties. In order to highlight the impact of the raw material associated to Diffractive-Trifocal-IOLs, we compare certain optical properties of two Diffractive-Trifocal-IOLs associated to Physiol's Trifocal-technology and made of 26% hydrophilic and hydrophobic GF raw material. The Abbe number of the two IOL materials was measured with a refractometer. The through focus MTF curves at 3 wavelengths (480, 546 and 650 nm) and different apertures were generated by simulation in an Arizona eye model and compared with results on a PMTF optical bench.

Results:

The through focus MTF curves at the three wavelengths shows that the diffracted light for the near vision (+3.5 D) by the trifocal optic generates chromatic aberrations of opposite sign with respect to the refracted light assigned to the Far vision. The diffracted light at the origin of the Intermediate vision (+1.75 D) does not show significant amount of LCA and can be considered as a chromatic aberration free focus. Results are similar for the two lens materials.

Conclusions:

Diffractive Trifocal IOLs show chromatic aberrations whose sign and amplitude depend on the add-power of the different foci (far, near or intermediate), but is basically independent of the nature of the type of raw material, hydrophilic or hydrophobic.