  In this work, we propose a new diffractive trifocal intraocular lens design
with focus extension, conceived to provide a high visual performance at
intermediate distances. This design is based on a fractal structure known as
the "Devil's staircase". To assess its optical performance, numerical
simulations have been performed with a ray tracing program using the
Liou-Brennan model eye under polychromatic illumination. The simulated through
the focus visual acuity was the merit function employed to test its
pupil-dependence and its behavior against decentering. A qualitative assessment
of the multifocal intraocular lens (MIOL) was also performed experimentally
with an adaptive optics visual simulator. The experimental results confirm our
numerical predictions. We found that our MIOL design has a trifocal profile,
which is very robust to decentration and has low degree of pupil dependence. It
performs better at intermediate distances than at near distances and, for a
pupil diameter of 3 mm, it works like an EDoF lens over almost the entire
defocus range.
