Transcript ascrs2008.abstractsnet.com

“Evaluating and Defining the Sharpness of IOLs:
Microedge Structure of Commercially Available
Square-Edge Hydrophobic IOLs”
Matthias Müller, PhD,1
Liliana Werner, MD, PhD,1,2
Manfred Tetz, MD1
1
Berlin Eye Research Institute (BERI), Berlin, Germany
2John A. Moran Eye Center, Salt Lake City, UT, USA
-The authors have no financial or proprietary interest in any product mentioned in
this poster.
-Supported in part by unrestricted research grants to the BERI from Alcon, AMO,
Wavelight, Hoya, and Advanced Vision Science, and by a 2007 Research Grant from
the ESCRS (Werner).
-Some of the IOLs described here are not FDA approved.
Background
•
Posterior chamber intraocular lenses (IOLs) with a square posterior optic edge were
found to be associated with better results in terms of posterior capsule opacification
(PCO) prevention, regardless of the material used in their manufacture. This IOL
design feature can be appropriately assessed in morphological studies using
scanning electron microscopy (SEM). However, SEM studies of new IOLs have
generally focused on the quality of their optic surface, or their optic finishing, with no
specifications made on how sharp the optic edge needs to be to effectively prevent
lens epithelial cells (LECs) from growing onto the posterior capsule.1
•
Tetz and Wildeck performed the first attempt to evaluate and quantify the edge
structure of IOLs at the microscopic level (Part 1).2 They experimentally evaluated
the optimum microedge profile of an IOL to prevent LEC migration in cell culture.
Experimental PMMA lenses with different edge profiles were imaged under SEM,
and the area above the edge, representing the deviation from an ideal square was
calculated with a digital system (EPCO).3
•
The objective of this poster was to describe the findings of our current study (Part
2), for which we used an improved methodology to evaluate the optic microedge
structure of currently available, hydrophobic IOLs marketed as square edge lenses.
The experimental square edge PMMA lens in Part 1, with the edge design that
effectively stopped LEC growth in culture was used as the reference lens against
which the currently available square edge lenses were compared.4
Materials/Methods
•
•
•
•
IOL designs: Sixteen designs of hydrophobic acrylic or silicone IOLs. Reference square edge
lens: experimental square edge PMMA lens, with an edge design that effectively stopped LEC
growth in culture (Part 1). Control lenses: 2 round edge silicone lenses;
IOL powers: +20.0 D IOL and +0.0 D IOL (or the lowest available plus dioptric power);
SEM system: Hitachi S-2700 SEM (X25, X300, X1,000). Analysis from a perpendicular view of
the edge;
Image analysis system: JPEG photos imported to the AutoCAD LT 2000 system (Autodesk,
San Rafael, CA, USA):
X25
X1,000
•Micron
scale
adjusted
(reference bar in SEM photos);
•Projection of reference circles
of 40 and 60 microns of radius
on the photos (the area
evaluated was therefore the
area of interaction of at least 1
or few LECs with the optic
edge);
•Area above the lateral-posterior
edge (deviation from a perfect
square) was measured in
square microns.
Post. surface
Ant. surface
40-μ radius
(Equiconvex)
In vivo LEC: 8-21
μ in diameter
(larger lengths)
Area = 281.4 μ2
Results
Reference PMMA lens: 34.0 and 37.5 μ2 (40- and 60-radius circles,
respectively);
+20.0 D control silicone lens: 729.3 and 1,525.3 μ2;
+0.0 D control silicone lens: 727.3 and 1,512.7 μ2;
Acrylic IOLs: 69.5 to 338.4 μ2 (40 radius); 122.4 to 524.4 μ2 (60 radius);
Silicone IOLs: 4.8 to 281.4 μ2 (40 radius); 0.2 to 520.4 μ2 (60 radius);
Out of 30 lenses, 7 silicone lenses had area values smaller or in the
vicinity of the corresponding values of the reference PMMA IOL (+5.0
Z9002, +20.0 L200, +20.0 SofPort AO, +0.0 and +20.0 SoFlex SE, and
+12.5 and +20.0 AQ310Ai);
Acrylic versus silicone lenses: P = 0.0017 for 40- and 60-radius circles
(Wilcoxon Two-Sample Test);
+20.0 D versus +0.0 D (or lowest available dioptric power) lenses: P =
0.4419 and P = 0.2616 (NS) for 40- and 60-radius circles.
Area
Area
IOL model
IOL manufacturer
Dioptric
power
Optic
material
(40
Radius)
(60
Radius)
Matrix Acrylic
Medennium
0.0
Acrylic
69.5
131.8
SA60AT
Alcon
20.0
Acrylic
97.2
157.5
SN60WF
Alcon (aspheric)
6.0
Acrylic
100.1
159.4
Hydromax
Zeiss
10.0
Acrylic
104.4
171.0
SA60AT
Alcon
6.0
Acrylic
114.5
122.4
Hydromax
Zeiss
19.0
Acrylic
116.5
211.2
Matrix Acrylic
Medennium
20.0
Acrylic
133.8
275.5
SN60WF
Alcon (aspheric)
20.0
Acrylic
136.5
228.8
L450
Wavelight
20.0
Acrylic
138.8
287.3
VA60BB
Hoya
0.0
Acrylic
169.5
111.5
ZA9003
AMO (aspheric)
20.0
Acrylic
188.4
377.8
AR40e
AMO
20.0
Acrylic
196.6
403.5
X-60
AVS
0.0
Acrylic
202.7
232.7
ZA9003
AMO (aspheric)
10.0
Acrylic
232.0
391.7
X-60
AVS
20.0
Acrylic
268.0
395.0
MA60MA
Alcon
0.0
Acrylic
268.8
524.4
MA60AC
Alcon
20.0
Acrylic
278.9
421.0
VA60BB
Hoya
20.0
Acrylic
329.7
427.3
AR40M
AMO
0.0
Acrylic
338.4
448.3
Examples of square optic edge profile and finishing of hydrophobic acrylic IOLs:
SA60AT, +20.0 D
AR40e, +20.0 D
L450, +20.0 D
Matrix Acrylic, +0.0 D
Z9003, +10.0 D
VA60BB, +0.0 D
Area
Area
(60
Radius)
IOL model
IOL manufacturer
Dioptric power
Optic material
(40
Radius)
SoFlex SE
Bausch & Lomb
0.0
Silicone
4.8
0.2
SofPort AO
B&L (aspheric)
20.0
Silicone
16.9
17.5
Z9002
AMO (aspheric)
5.0
Silicone
17.7
21.7
AQ310Ai
Staar (aspheric)
20.0
Silicone
19.7
20.1
L200
Wavelight
20.0
Silicone
28.7
30.3
AQ310Ai
Staar (aspheric)
12.5
Silicone
38.9
39.9
SoFlex SE
Bausch & Lomb
20.0
Silicone
40.1
39.9
Z9000
AMO (aspheric)
5.0
Silicone
78.2
96.5
SofPort AO
B&L (aspheric)
0.0
Silicone
89.3
123.7
Z9002
AMO (aspheric)
20.0
Silicone
202.6
359.6
Z9000
AMO (aspheric)
20.0
Silicone
281.4
520.4
•IOLs with deviation areas in the vicinity to the cut off limits (or smaller) had similar values for the
40- and the 60-radius circles, while the others had a tendency to present increasing values with
the larger radius, mostly as a function of the convexity of their posterior optic surface.
Examples of square optic edge profile and finishing of silicone IOLs:
SofPort AO, +20.0 D
SoFlex SE, +0.0 D
Z9002, +20.0 D
Z9002, +5.0 D
Z9000, +20.0 D
AQ310Ai, +12.5 D
Discussion / Conclusions
• A square edge on the posterior optic surface was found to
be the most import IOL-related factor for PCO prevention.
According to different experimental studies, this may be due
to the mechanical barrier effect exerted by the square
edge,5 to the contact inhibition of migrating LECs at the
capsular bend created by the sharp optic edge,6 to the
higher pressures exerted by IOLs with a square edge optic
profile on the posterior capsule,7 or perhaps to varying
combinations of all of the above.
• Analysis of the microstructure of the optic edge of currently
available, square edge, hydrophobic IOLs revealed a large
variation of the deviation area from a perfect square, as well
as of the edge finishing. Both parameters varied not only
among different designs, but also between different powers
of the same design.
Discussion / Conclusions
• If IOLs with different square microedge profiles produce similar
outcomes in terms of PCO formation, one may conclude that other
factors play a role in its prevention. We believe the factor that may play
the most important role in even out the differences in the microedge
profiles shown in our study is the shrink wrapping of the IOL by the
capsular bag, enhancing the contact of the posterior IOL surface with the
posterior capsule. The amount of postoperative capsular bag shrinkage
has been indirectly determined in clinical studies, by the measurement
of the diameter or the area of the capsulorhexis opening at different
postoperative time points (13.8 to 14.8%).8-11
Central PCO = 0
Soemmering‘s ring
Discussion / Conclusions
• We believe that existing and future clinical data will help us to better
understand the effect of microedge structure and design on reducing
PCO. At present, a cut-off value should be sought for to clinically label
an IOL as square edged. This study may help on the task for better
understanding differences in microedge structures.
• We only focused on commercially available hydrophobic IOLs. Due to
their low water content, we believe the SEM technique used did not
cause any significant alteration of the IOL edge profile. Modern
hydrophilic lenses, with water contents generally in the vicinity of 26%
may have their microedge structure significantly modified during the
vacuum required in standard SEM procedures. Therefore, we are
currently evaluating the microedge structure of hydrophilic lenses by
using an environmental SEM technique, which operates in low vacuum
and does not require any prior coating. Results of this evaluation are the
object of an upcoming report.
References
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