A NEW TRIFOCAL DESIGN

Purpose:
Contributions of IOL biomaterial (Abbe #) and diffractive pattern topography on LCA of various types of multifocal IOLs.

Methods:
The LCAs associated with the different focal points of diffractive hydrophobic – made of aromatic and/or aliphatic materials – and hydrophilic multifocal IOLs were experimentally determined on an optical bench in RGB conditions (650, 546 and 480 nm). The effects of Abbe number and of the topography of the different diffractive profiles were evaluated. Based on wavelength–dependent MTF through-focus curves, polychromatic behavior of multifocal IOLs was assessed.

Results:
LCA amplitudes and signs were different for each of the focal points. While far vision LCA was of negative sign and appeared to be controlled by the material Abbe number, the diffractive LCA for near and intermediate visions was independent of IOL material. The diffractive pattern characteristics, which control the closer distance powers, prove to be pivotal in fine-tuning the LCA related to these near and intermediate foci.

Conclusions:
Diffractive multifocal IOLs show chromatic aberrations with are controlled by the biomaterial Abbe number for its refractive component on the one hand, and by the topography of the diffractive pattern for the second component on the other hand.