For the launch of Varilux Physio f-360™, Essilor has
developed new tools to calculate a dual-sided design that would minimize
aberrations over the whole lens.
The front side is a complex progressive surface that
incorporates the degree of correction for presbyopia.
The back side integrates, if necessary, the required degree
of correction for any visual defect (astigmatism, hypermetropia or myopia) and
takes 5 fitting parameters into account: the distance between the eyes, the
fitting height at the pupil center, the lens-eye distance, the lens inclination
and the angle of curvature of the frame. The position of the near vision zone
varies continuously according to these considerations.
By factoring these 5 measurements into the calculation of
the design, the performance for each direction of sight and each lens position
relative to the pupil is optimized. To measure these different parameters,
Essilor has recently developed new measurement tools for opticians.
The dual-sided design is transformed into a customized
physiological optical lens by means of a groundbreaking manufacturing
procedure: digital surfacing combined with point-by-point twinning of the front
and back sides of the lens.
Varilux Physio f-360°™ provides a high degree of accuracy
and visual comfort at all distances, and particularly for near vision.
Perception of contrast is 30% better than with previous generation lenses.
Measuring the five parameters
Specific measuring
devices are required to obtain the additional parameters
required for Varilux
Physio f-360° lenses. These measurements can be taken
using either a fully
automated instrument such like Essilor’s Visioffice unit
that can prove
invaluable in terms of the speed and accuracy, or by using
a hand held device.
Wavefront Management
System™
The Wavefront
Management System™ is a design approach that
considers the wavefront
of the beam of light entering the pupil.
Quality of vision
depends on how much the wavefront is distorted
by both sides of the
lens.
Optimising the
wavefront through the front and rear surface of the lens
greatly reduces aberrations
including higher order aberrations like the coma.
wavefront analysis
The Wavefront
technology allows analysis of lens performance.
With Varilux Physio
f-360° the beam of light passing through the lens is
virtually aberration
free for any direction of gaze whatever the
fitting conditions.
Near vision point location
To achieve perfect
alignment, the exact position of the near vision zone is
tailored to the five
measurements. Vertically, the position can vary between
15-18mm, with the
horizontal inset varying between 1.7 & 7mm.
This exact positioning
ensures the wearer no longer needs to adopt
unnatural postural
adjustments for near vision tasks. Postural comfort and
sharp crisp vision are achieved
naturally without constraints.
