2
V
ario Data: After receiving the height data from the
Topolyzer Vario (a device that is specifically selected
to provide benchmark performance in centration
and resolution in topography measurements), the
Contoura Vision topography-guided ablation design begins
with the calculation of the reference body. The median of the
flat meridian (although both keratometry values are displayed
at the planning screen of the WaveLight EX500) is used to
shape the reference body. Additionally, the asphericity of the
dataset imported is determined and used. If various datasets
are imported, the median calculation will only include exams
of the same day.
The actual corneal shape is now fitted to the reference
body. Differences in this calculated reference body are an-
alyzed by a proprietary algorithm based on Zernike poly-
nomials used for the later ablation profile calculation, and
the difference of radii of the main meridians are translat-
ed to C3 and C5 polynomial amplitudes.
Exams containing at least 90% or more data within the
optical zone will be activated by the algorithm and will be
used for the reference body median calculation. To in-
clude exams containing less than 90% of data points, the
user may reduce the optical zone (e.g., from 6.5 mm to 6.0
mm). This decrease of optical zone will potentially result
in surpassing the 90% criterion and will allow Contoura
Vision surgery for patients where patients' anatomy might
shadow the Placido ring projection.
If desired, at this stage, the asphericity used for fitting
the reference body can be modified. However, modifying
the asphericity will affect the spherical aberration and po-
tentially the achieved spherical correction.
To eliminate obvious outliers, the general visual im-
pression of the individual exams, but also some ancillary
criteria such as the keratometry and its axis, the aspheric-
ity, and with lower importance the pupil-size, can be used
as criteria to identify outliers.
Please see Important Product Information about the products mentioned
in this supplement on pages 7-8.
Zernike Fit
Raw Data Sagittal Raw Data Tangential
Contoura Vision
Topography-Guided
Ablation Algorithms
Resulting Examination Profiles
Sissimos Lemonis,
is Director of Clinical Support at
WaveLight GmbH in Erlangen,
Germany. He can be contacted at
sissimos.lemonis@alcon.com.
Overview of imported exams
Advanced Eye-Tracker options for the later treatment will
only be available if an exam with good forecast status
indication (
R
) is used. At this stage, the software will select
one infrared image from the dataset, and that image will
be marked with an asterisk (*). This identified infrared
image is the closest to the median of the selected dataset
imported. The image chosen may also be of red forecast
status
R
(registration not possible); therefore, it is import-
ant to only export infrared images with a green forecast
status if registration is desired or indicated.
The imported examinations and the resulting Examina-
tion Profile can be displayed in various maps:
