Diffraction always occurs during the propagation of light waves.
Each surface of any IOL (“refractive” or “diffractive”) generates a phase shift in light waves.
Based on the level of phase shift the diffractive interference can be constructive or destructive in the image space.
ELEVATED PHASE SHIFT * (EPS)
Medicontur‘s proprietary, patented approach to trifocality:
Figure 1: Radial profile with central diffractive phase shift elevated from a destructive level to a constructive interference level.
The Liberty Concept uses EPS in the central part of the optic to generate constructive interference between the 0 (far) and 1st (near) diffractive order. This revolutionary optical design generates the 3rd focal point for intermediate vision in a very unique way:
Figure 2: MTF through focus curves with central diffractive phase shifts at a destructive and a constructive interference level resulting in a 3rd focal point for intermediate vision.