MONOFOCAL ASPHERIC IOLs
Study of the Visual Performance
Of Aspheric IOLs
Paris XV XX (Prof. Nordmann’s department) / Centre Eiffel
Assessment of the benefits offered by
aspheric IOL (IOL A) requires:
• Evaluation of their performance and comparison of
this performance with that of spherical implants.
• An understanding of the various designs.
The search for vision quality improvements is a shared
objective in both refractive and cataract surgery.
The first photoablative profiles provided good VA
under conditions of maximum contrast,
but often created halos in dim light and occasionally a
significant drop in VA for mesopic vision.
The problem identified for these profiles is that they
should have incorporated Zernicke polynomials
and the HOA.
Accordingly, aspheric profiles have now been
developed that eliminate these visual disturbances
in most cases.
In cataract surgery the approach is the same, but
there is a difference:
patients are always pleased to recover good
VA and the main concern is to obtain good
However, with implant calculation becoming
increasingly accurate, and with the intervention
itself causing less and less astigmatism, the
problem is how to determine which patient, out of
two who have the same refraction, will ultimately
have the best visual envelope.
• This concept defines how the eye perceive shapes and
details under the various conditions of contrast and
• The underlying principles are the analysis of contrast
vision and MTF.
(The measurement of the standard VA at high contrast forms part of the
determination of this envelope)
•The MTF is studied using an aberrometer.
It does not consider retinal and cerebral integration that can
distort the analysis.
•It thus offers an objective means of evaluating IOL.
How does MTF measurement work?
• The aberrometric measurement determines the PSF.
• The PSF is used to produce a convoluted image.
The MTF is used to define the visual envelope.
The perception threshold will be studied for each spatial
Linking the various thresholds produces a curve.
Low contrast Not seen NS NS
Seen Seen Not seen
High contrast Seen Seen Seen Not seen
Large optotype Small optotype
Spatial frequency (cpd)
- if the image projected onto the retina is kept sharp,
- then the eye is better able to identify it when its size is
reduced (by distance) or when the contrast conditions
are less favourable.
•The SA induced by the cornea are on average +0.28 µm.
•The overall SA for the eye of a young subject is +0.10 µm.
•An excess of +SA has an adverse effect.
•A certain degree of +SA improves the depth of field.
• During SAFIR 2005/2006 and ESCRS:
We presented aberrometric studies on the Tecnis AMO and
then on the Sofport AO B&L.
They suggested that the IOL A produced better results
compared with their spherical equivalents.
•Today, we shall present the results of a multi-centre
trial of the very latest IOL A:
XL Stabi ZO Zeiss Ioltech
XL Stabi ZO Zeiss Ioltech:
aspheric posterior profile.
What differentiates this IOL A from other IOL A is its
geometry - calculated from a physiological ocular globe
model and not simply from a corneal model.
This has made it possible to validate its design
using MTF curves.
A specific calculation is performed for each implant power.
Study of the first 200 cases of
XL Stabi ZO Zeiss Ioltech
No case of dysphotopsia
No case of a significant error in implant power
No astigmatism that could not be linked to corneal
MFT results for XL Stabi ZO
Spherical aberration MTF
Average SA - Control group
Average SA - All ZO lenses
Mesopic with no
0 20 40 60
Spacial frequency (cycles/degree)
Do the aspheric IOLs offer an improvement?
The various studies revealed an improvement in vision
quality for the various IOL A compared with their IOL S
equivalents. Moreover, the IOL S are highly sensitive to tilt.
Can they cause dysphotopsia?
No dysphotopsia was found for the 500 IOLs of different
Only the Tecnis lens, which is extremely prolate, shows a
certain sensitivity to decentration and tilt according to one
of the designers, Holladay, and confirmed by Altmann.
What effects do the various aspheric implants induce?
Generate negative SA.
AMO Tecnis: 1st generation IOL A generates -SA of –0.28 µm
Alcon IQ: generates -SA evaluated at –0.20 µm
e.g.: If corneal SA = + 0.15 µm: Tecnis: -0.13 µm; IQ: -0.05 µm
2) NON PROLATE
B&L Ab Free: cancels out the +SA that a comparable IOL S might
have generated. The resulting SA corresponds to the SA of the
In comparison with the IOL A based on a corneal model, the
design of the XL Stabi ZO Zeiss Ioltech appears to be very
interesting. It is based on a physiological ocular model, and
its design integrates pupil offset and the offset of the visual
Its geometry is based on MTF curves that provide an
objective means of measuring the visual envelope.
The clinical results are good and have been confirmed by
MTF curves, measured using the WASCA aberrometer
(Zeiss), in a study that is on-going.
Are there any particular indications?
The first generations of IOL A , based on a corneal model
with an average SA = +0.27µm, made it possible to define
the indications and contraindications as a function of the
The design of the XL Stabi ZO implant lens is based on a
physiological ocular model and on the MTF. The objective
is to produce a multi-purpose implant, that is less sensitive
to offset and tilt than a spherical implant.
The MTF provides an objective means of evaluating IOL and
is used to evaluate the visual envelope.
The aspheric IOL is an evolution that has been developed by
all the laboratories. It is the product of the shared desire to
deliver improved vision quality to match the achievements in
The XL Stabi ZO implant lens is an interesting design whose
good initial results have been confirmed by these first studies.
1. G.E Altmann: Optical perform.of 3 IOL designs in the
presence of decentration: JCRS 31, March 2005
2. J.T Holladay: a new IOL design to reduce spherical
aberration of pseudophakic eyes JRS, Nov. 2002.
3. R.M. Kershner: Retinal image contrast and functional
visual performance with aspheric, silicone, and acrylic
IOL. JCRS 29, Sept. 2003
4. R.Bellucci: comparison of W.front ab.and optical quality
of eyes implanted with 5 different IOL: JRS 20 Jul. 2004
5. S. Marcos: Aberrations and visual performance
following standard laser vision correction. J Refract Surg
6. D. Gatinel: Visions. Surgical Insights W/S 2007:31-38
7. C. Corbe, Fajnkuchen …
8. L. Wang: High-order aberrations from the internal optics
of the eye: JCRS 31, August 2005