Clinical Review

D
TE 5
A T 201
P D US
U A UG
Clinical Review
Spring Issue 2014
True Axis: Essential for premium IOL Planning
Douglas D. Koch, M.D.
Baylor College of Medicine
Houston, TX USA
Ronald Krueger, M.D.
Cleveland Clinic
Cleveland, OH USA
Arthur Cummings, M.D.
Wellington Eye Clinic
Dublin, Ireland
Jonathan Solomon, M.D.
Solomon Eye Associates
Bowie, MD USA
James Schumer, M.D.
Revision Eyes
Mansfield, OH USA
The challenge of
determining the
exact axis of
astigmatism for
cataract surgery
Determining the exact axis of corneal
astigmatism during cataract surgery planning
can be a challenge due to the measuring
limitations of current corneal topographers
and keratometers. In addition, the expectations
and demands of patients have risen in recent
years and the search for perfection has
become critical, especially when it comes
to astigmatism correction.
Noted toric IOL expert Warren Hill, MD,
Medical Director of East Valley Ophthalmology
in Mesa, AZ, has described how each degree
that a toric IOL is misaligned will results in
a loss of 3.3% of correction power. So,
even at 5 degrees of misalignment, there is
a loss of 16.5% and a larger 10 degrees
will equate to a loss of one-third of the
toric IOL correction power. At 30 degrees
James Katz, M.D.
The Midwest Center for Sight
Des Plaines, IL USA
Farrell Toby Tyson, M.D.
Cape Coral Eye Center
Cape Coral, FL USA
Mitchell P. Weikert, M.D., M.S. A. John Kanellopoulos, M.D.
Laservision Eye Institute
Baylor College of Medicine
Athens, Greece
Houston, TX USA
Frank Bowden, M.D.
Bowden Eye and Associates
Jacksonville, FL USA
misalignment, there is full loss of toric IOL
correction power. The impact of misalignment
on vision becomes greater with increasing
toric IOL power.
Cassini is ready to play an essential role
in your toric IOL planning process. Due to the
superb axis precision of less than 3 degrees
measured by Cassini, this new color LED
patent device could play an essential role
in your toric diagnostic platform.
“Cassini offers new insights and opportunities”
and is “a better alternative” when it comes
to corneal astigmatism axis determination in
toric IOL planning, says Douglas D. Koch,
MD, Professor of Ophthalmology at Baylor
College of Medicine, Houston, TX.
Along with TrueVision’s TrueGuide surgical
guidance software, Cassini can address
data generation and alignment marking
errors that can occur during toric IOL
planning and implantation. The use of Cassini
data and imaging of the eye to address
cyclotorsion errors, along with registration
of the planned treatment aligned to the live
surgical eye provides surgeons with digital
precision during premium cataract surgery
Johny Gayton, M.D.
Eyesight Associates
Warner-Robins, GA USA
Michael Endl, M.D.
Fichte, Endl & Elmer
Amherst, NY USA
Nic J. Reus, M.D.
Het Oogziekenhuis
Rotterdam, The Netherlands
procedures. The synergy of Cassini diagnostics
with intraoperative guidance technology
and real-time eye tracking is driving a new
approach to address known potential errors
in traditional cataract surgery. Cassini data
is having a real impact in today’s surgical
practice.
Experienced Cassini user Jonathon D.
Solomon, MD, Medical Director at Solomon
Eye Associates, Bowie, MD, maintains that
“any procedure that requires accurate axis
determination benefits from Cassini’s data.
Cassini takes the guesswork out of the
equation.”
This is an incredibly dynamic time in the
evolution of our understanding of the cornea
and its optics, as well as how surgeons
can use this information for more accurate
and safe procedures for patients. Cassini
provides an exciting new method of corneal
analysis to increase toric IOL use and to
ease the planning of surgical astigmatism
treatments. Improved data going into the
planning process is the key to producing
optimal patient outcomes.
Axis repeatability in normal corneas
Dr. Kanellopoulos (NYU Medical School,
New York; Laservision Eye Institute, Athens,
Greece)) has evaluated the clinical effects
of Cassini and investigated the repeatability
of astigmatism measurements in a group
of young healthy corneas and a group of
elderly pre-cataract corneas.
0
0
Steep
Axis repeatability
Steep Axis repeatability (0) Steep Axis repeatabilitySteep
Axis
repeatability
(0) (0)
(0) (0)Axis repeatability ( ) Steep
Axis
repeatability
(0) (0) ( ) Steep
Steep
Axis
repeatability
Steep Axis repeatability
Steep
Axis
repeatability
Cassini has proven to measure the axis of astigmatism within 3 degrees in normal corneas.
Axis repeatability in young healthy corneas (n=175)
Axis repeatability in young healthy corneas (n=175)
4
4
3
3
2
2.49
2.49
2
2.05
2.05
1.44
1.44
1
1.14
1.14
1
0
0
4
34
4
3
2
3
< 1.00D
1.00D
- 1.99D healthy corneas
2.00D - 2.99D
Axis
repeatability in
young
(n=175)
< 1.00D
0
0
2.49
3.03
3.03
< 1.00D
2.05
2.70
2.70
> 3.00D
1.44
1.14
1.25
1.25
1.00D - 1.99D
0.62
0.62
2.00D - 2.99D
> 3.00D
2.00D
- 2.99D (n=175)
< 1.00D
- 1.99Dpre-cataract
Axis
repeatability in1.00D
elderly
corneas
< 1.00D
2.00D - 2.99D
1.00D - 1.99D
4
3
> 3.00D
> 3.00D
Data courtesy of Dr. A. John Kanellopoulos & Dr. George Asimellis
3.03
2
> 3.00D
2.00D - 2.99D
Axis repeatability in elderly pre-cataract corneas (n=175)
Axis repeatability in elderly pre-cataract corneas (n=175)
2
1
2
1
0
1
1.00D - 1.99D
2.70
Axis repeatability in complicated corneas
Axis repeatability in complicated corneas
1.25
Axis repeatability in complicated corneas
1
6
6
0
0.62
< 1.00D
2.00D - 2.99D
1.00D - 1.99D
> 3.00D
4
3.45
4
Cassini has proven to measure highly irregular
and 3.45
complicated corneas,
accurately and precisely.
3.12
3.03
Dr. Kanellopoulos also investigated the
repeatability of axis measurements in
complicated corneas. The conditions
included post-LASIK group, corneas with
relatively low astigmatism, keratoconus
group, corneas with relatively high
astigmatism and *post-Athens Protocol
group.
3.12
2
3.03
2
0
0
6
4
Axis repeatability in complicated corneas
Post-LASIK
(n=51)
Post-LASIK
(n=51)
Keratoconus
(n=95)
Keratoconus
(n=95)
3.45
Post-Athens
Protocol
(n=47)
Post-Athens
Protocol (n=47)
3.12
3.03
Keratoconus
(n=95)
Post-Athens
Protocol (n=47)
2
0
Post-LASIK
(n=51)
1
2
3
Data courtesy of A. John Kanellopoulos, MD.
1
Clinical
Professor
Of Ophthalmology
A. John
Kanellopoulos,
M.D. Clinical Professor
Of
Ophtalmology
NewMedical
York University
Medical School
New
York
University
School
2
3
Karabatsas et al. EJO 2005
McAlinden et al. IOVS 2011
Data courtesy of Dr. A. John Kanellopoulos & Dr. George Asimellis
*Athens Protocol = Anterior-surface topography-guided excimer
ablation combined with high-fluence collagen cross-linking performed
in the same session on Keratoconus corneas.
Astigmatism correlation comparison study
Cassini measurements (corneal axis and magnitude of astigmatism) shows to be significantly closer
to the data of the auto-refractor, in comparison with other topographers.
Axis of Astigmatism
Correlation
R^2 R^2
Correlation
1,0
0,8
1,0
Axis of Astigmatism
0.88
0,6
0,8
0.59
0,4
0,6
0.59
0,2
0,4
0,0
0,2
0,0
0.70
0.67
0.70
0.88
Pentacam Ant.
Pentacam
Ant. & Post.
Lenstar Ant.
Cassini Ant.
Pentacam Ant.
Pentacam
Ant. & Post.
Lenstar Ant.
Cassini Ant.
Magnitude of Astigmatism
1,0
Correlation
R^2 R^2
Correlation
Dr. Arni Sicam (PhD, Rotterdam Eye
Institution, The Netherlands) has evaluated
the correlation of total cylinder acquired
by a Topcon auto-refractor versus the
anterior corneal astigmatism (both axis
and magnitude) of Cassini, Pentacam
and Lenstar LS 900 on 39 Pseudophakic
eyes with spherical monofocal IOL’s.
0.67
Magnitude of Astigmatism
0,8
1,0
0,6
0,8
0,4
0,6
0,2
0,4
Pentacam Ant.
0.60
0.64
Lenstar Ant.
Pentacam
0.19
Ant. & Post.
Pentacam
Ant. & Post.
0.13
0,0
0.64
0.19
0.13
0,0
0,2
0.60
Pentacam Ant.
Cassini Ant.
Lenstar Ant.
Cassini Ant.
Data courtesy of Dr. Arni Sicam
Accurate measurements regardless of tear film stability
With Cassini’s multicolor LED point-to-point
measurement technique, virtually all corneas
can be measured accurately.
Artificial surface acquisition with an octofoil test target
28
2,8
4
24
2,4
3
20
16
2,0
1,6
2
12
1,2
0.01
0,8
1
4
0
-4
y (mm)
height (µm)
8
height (µm)
0.02
0
-1
-8
0
-12
-20
-24
-2
-1,6
-2,0
-2,4
-4
-2,8
-0.02
-4
-3
-2
-1
0
1
2
3
4
Image reconstructed by Cassini
0
x(mm)
28
Octofoil test target
2,8
4
24
16
1,6
2
0,8
1
height (µm)
y (mm)
4
The state-of-the-art technology of Cassini
demonstrates the accurate and superior
results in reconstructing a rotational nonsymmetric surface.
0
-1
-8
-12
-24
1
0,4
0
-0,4
0
-1
-0,8
-2
-1,2
-16
-20
2
1,2
8
0
3
2,0
12
-4
4
2,4
3
20
y (mm)
0
-2
-1,6
-3
-2,0
-2,4
-4
-28
-3
-4
-2,8
-4
-3
-2
-1
0
1
2
3
4
0
-1,2
-3
-28
y(mm)
0,4
-0,4
-0,8
-16
-0.01
height (µm)
Cassini technology employs 679 red,
green and yellow LEDs that are each
positioned in a unique relationship to all
four LED points surrounding it, which gives
each one an unmistakable ‘coordinate’.
Cassini uses the Ray-Tracing principle to
measure the position of each point in
relation to that of its neighbors, using
the three different colors as triangulation
points. A rise in elevation increases the
distance between points and a dip in
elevation decreases it. Due to the fact
that Cassini does not use edge detection
in its measurement algorithms, smeared
or doubly reflected LEDs cannot influence
the results in any direction. Together, these
design principles enable Cassini to
shine as a robust analysis device to aid
in surgical planning.
A poor tear film in Placido acquisition can
result in melted or distorted rings, which
will cause misinterpreted information.
z(mm)
True
Technology
-4
-3
-2
-1
Image reconstructed by a Placido system
0
1
2
3
4
Case report: Robust in imaging a highly
irregular cornea with Keratitis
An 18 year old female patient, infected with Acanthamoeba Keratitis in her right (OD) eye approximately two years ago.
Comparison of measurement results between different devices
OCT high resolution meridian (80°) Scan
The OCT successfully shows the deep stromal scars,
appearing as an opacity associated with the residual
stromal scaring (central corneal thickness and minimum
corneal thickness were 381µm and 318µm respectively).
A thinner epithelium (56µm) over the thinnest, most elastic
region of the cornea.
Cassini Scan
Cassini imaging on the affected eye shows both radial and
contour differences based on differential spot-imaging enabling
proper imaging and accurate measurement of this irregular
cornea.
Cassini Specifications
True Axis
l
l
Multicolor LED imaging technology
Axis repeatability within 3 degrees
Diopter range 4.00D – 171.00D
Display K-values per zone
l Keratometric indices display in D (diopters)
or mm (millimeters)
l
True Magnitude
Scheimpflug Scan
As a possible consequence of the corneal opacity,
the posterior surface is poorly identified and the lesion
may alter the normal densitometry interpolation of the
Scheimpflug algorithm. The Scheimpflug imaging derived
central and minimum corneal thickness were 438µm and
167µm respectively which was very different from the
OCT data.
l
l
l
l
True Capture
l
l
l
True Accuracy
l
l
l
l
True Technology
l
l
l
Auto Capture with joystick positioning
Measurement Quality Factor parameter
Auto pupil detection
Topographic indices - E (shape factor), e (eccentricity),
Q (asphericity), p (form factor)
Keratoconus indices - SAI (Surface Asymmetry Index),
SRI (Surface Regularity Index)
679 LED lights with 129,000 points analyzed
10.00mm analysis diameter
Full color Photography
Topographic maps - Axial, Refractive, Tangental,
Elevation, Aberrations, Recorded color HD image
Multiple color spectrum options
Incorporated patient management program
USB, Direct print, PDF, JPG, PNG, 3rd party output
connectivity
Mesopic and photopic pupillometry
Placido Ring System Imaging
The Placido imaging shows the highly distorted ring pattern
along the vertical direction. The refractive map shows very
large variation of the corneal refraction, ranging from
a localized 33.50D inferiorly to more than 48.00D
superiorly, which was not successful in imaging this case.
Data courtesy of Dr. A. John Kanellopoulos & Dr. George Asimellis
For more information:
i-Optics USA - usa@i-optics.com - +1 888 660 6965
i-Optics International - info@i-optics.com - +31 70 3993 112 - www.i-optics.com