Evaluating and Defining the Sharpness of Intraocular Lenses

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Evaluating and defining the sharpnessof intraocular lenses

Microedge structure of commercially availablesquare-edged hydrophobic lenses

Liliana Werner, MD, PhD, Matthias Muller, PhD, Manfred Tetz, MD

PURPOSE:To evaluate the microstructure of the edges of currently available square-edged hydro-phobic intraocular lenses (IOLs) in terms of their deviation from an ideal square.

SETTING: Berlin Eye Research Institute, Berlin, Germany.

METHODS:Sixteen designs of hydrophobic acrylic or silicone IOLs were studied. For each design,

a C20.0 diopter (D) IOL and a C0.0 D IOL (or the lowest available plus dioptric power) wereevaluated. The IOL edge was imaged under high-magnification scanning electron microscopy usinga standardized technique. The area above the lateralposterior edge, representing the deviationfrom a perfect square, was measured in square microns using reference circles of 40 mm and60 mm of radius and the AutoCAD LT 2000 system (Autodesk). The IOLs were compared with anexperimental square-edged poly(methyl methacrylate) (PMMA) IOL (reference IOL) with an edgedesign that effectively stopped lens epithelial cell growth in culture in a preliminary study. Tworound-edged silicone IOLs were used as controls.

RESULTS: The hydrophobic IOLs used, labeled as square-edged IOLs, had an area of deviation froma perfect square ranging from 4.8 to 338.4 mm2 (40 mm radius reference circle) and from 0.2 to524.4 mm2 (60 mm radius circle). The deviation area for the square-edged PMMA IOL was 34.0 mm2

with a 40m

m radius circle and 37.5 m

m

2

with a 60m

m radius circle. The respective values forthe C20.0 D control silicone IOL were 729.3 mm2 and 1525.3 mm2 and for the C0.0 D controlsilicone IOL, 727.3 mm2 and 1512.7 mm2. Seven silicone IOLs of 5 designs had area values thatwere close to those of the reference square-edged PMMA IOL. Several differences in edge finishingbetween the IOLs analyzed were also observed.

CONCLUSIONS:There was a large variation in the deviation area from a perfect square as well as inthe edge finishing, not only between different IOL designs but also between different powers of thesame design. Clinically, factors such as the shrink-wrapping of the IOL by the capsule may even outor modify the influence of these variations in terms of preventing posterior capsule opacification.

J Cataract Refract Surg 2008; 34:310317Q 2008 ASCRS and ESCRS

Posterior chamber intraocular lenses (IOLs) witha square posterior optic edge, regardless of thematerial used in their manufacture, have been associ-ated with better results in termsofposterior capsuleopacification (PCO) prevention.15 This IOL designfeature can be appropriately assessed in morphologicalstudies using scanning electron microscopy (SEM).However, SEM studies of new IOLs have generallyfocused on the quality of the optic surface or opticfinishing, with no specifications on howsharp the opticedge must be to effectively prevent lens epithelial cells

(LECs) from growing onto the posterior capsule.

6,7

In a preliminary study, Tetz and Wildeck8 made thefirst attempt to evaluate and quantify the edge struc-ture of IOLs at the microscopic level. They experimen-tally evaluated the optimum microedge profile of anIOL to prevent LEC migration in cell culture. Experi-mental poly(methyl methacrylate) (PMMA) IOLswith different edge profiles were imaged under SEM,and the area above the edge, representing the devia-tion from an ideal square, was calculated with a digitalsystem based on the Evaluation of PosteriorCapsuleOpacification System (EPCO 2000 program9). In this

current follow-up study, we used improved

Q 2008 ASCRS and ESCRS 0886-3350/07/$dsee front matter

Published by Elsevier Inc. doi:10.1016/j.jcrs.2007.09.024

310

LABORATORY SCIENCE


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methodology to evaluate the optic microedgestructure of currently available hydrophobic IOLsmarketed as square-edged IOLs. The experimentalsquare-edged PMMA IOL in the study by Tetz andWildeck, with an edge design that effectively stoppedLEC growth in culture, was used as the reference IOLwith which the currently available square-edged IOLswere compared.

MATERIALS AND METHODS

Commercially available hydrophobic IOLs with an opticcomponent manufactured from hydrophobic acrylic orsilicone materials were provided by the respective manufac-turers for use in this study. All the IOLs are marketed as hav-ing a square optic edge. Two IOLs of each design wereevaluated: a C20.0 diopter (D) IOL and a C0.0 D IOL whenavailable. If an IOL design was not available inC0.0 D,the lowest dioptric power for that design was used. Thecommercially available IOLs were compared with an exper-imental square-edged PMMA IOL (reference IOL) manufac-tured for use in the preliminary study.8 The edge designof the experimental IOL effectively stopped cell growth inculture (area above the edge of 13.5 mm2 measured withthe EPCO 2000 system). Two silicone IOLs (C20.0 D andC0.0 D) manufactured with round optic edges (model 733D,Acri.Tec) were used as controls.

The SEM analyses were performed by an experiencedtechnician trained in edge analyses at the Technische Univer-sitat, Berlin. Each IOL was carefully removed from its origi-nal packaging with a toothless forceps. This was done bygrasping the IOL by the haptics to prevent alteration of theoptic component. The IOLs were sputter-coated with gold,mounted on a round sample aluminum stub for imaging,

and examined under a Hitachi S-2700 scanning electron mi-croscope. During SEM examination, the analysis of each op-tic edge was done from a perpendicular view. To assist withthe perpendicular orientation of the specimen, information

on the radius of anterior and posterior IOL surfaces was ob-tained from the respective manufacturers as some biconvexIOL designs are not equiconvex. The authors signedconfidentiality agreements with the respective manufacturers;as this type of information is generally confidential, it is not in-cluded in this report. Photographs of the optic edge of eachIOL from a perpendicular view were obtained at 3 magnifica-

tions: 25, 300, and 1000. The first 2 magnifications wereused to document the overall orientation of the specimen,and the 1000 magnification photographs were used for themicroedge analysis (Figure 1,A andB).

The following procedures were performed by the sameobserver (L.W.): The SEM photographs of each IOL weresaved as electronic, high-resolution JPEG files. They werethen imported into the AutoCAD LT 2000 system (Auto-desk). This program, which is commonly used in engineer-ing and architecture, allows accurate area calculations. Thefirst step was to adjust the scale of the photograph into theprogram using the reference bar incorporated on the rightbottom corner of each SEM photograph. After the scale oneach photograph was confirmed by measuring the reference

bar and obtaining the corresponding value, a reference circleof known radius, divided into 4 quadrants by 2 perpendicu-lar lines passing through its center, was projected onto thephotograph. The position of the circle was adjusted so thatthe end of both perpendicular lines touched the lateral andposterior IOL optic edges. The area of the lateralposteriorIOL edge deviating from a perfect square defined by the 2perpendicular lines inside the reference circle was easily de-lineated using the computer mouse. The measurement of thearea was then calculated by the program and provided insquare micrometers. This was done using 2 reference circleswith a different radius: 40 mm and 60mm (Figure 1, Cand D).The minimum radius size of 40 mm was chosen as a functionof the size of the human LEC, which in vivo was shown tohave a size ranging from 8 to 21 mm in diameter, with larger

lengths.10

The area evaluated was therefore the area of inter-action of at least 1 LEC with the optic edge.

RESULTS

Table 1shows the characteristics of the IOLs used inthis study, including the values of the area represent-ing the deviation from an ideal square measured ineach IOL with the AutoCAD system.Figure 2showsSEM photographs of the lateralposterior edge of allIOLs analyzed incorporated into the AutoCAD analy-sis screen. The Hydromax IOLs and the L200 and the

L450 IOLs were received in the laboratory in nonsterileIOL containers. The C0.0 D X-60 IOL was manufac-tured for this study and was also provided in a nonster-ile container. All remaining IOLs were received in theiroriginal commercial packages. Two dioptric powerswere analyzed for each IOL design except the L200and the L450 IOLs, for which only the C20.0 D modelwas analyzed. A C19.0 D rather than a C20.0 D Hy-dromax IOL was analyzed.

For the square-edged PMMA IOL, the value of thearea measured with the AutoCAD system with the40 mm radius circle and 60 mm radius circle was

34.0 m

m

2

and 37.5 m

m

2

, respectively. The respective

Accepted for publication September 23, 2007.

From the Berlin Eye Research Institute (Werner, Muller, Tetz),Berlin, Germany, and John A. Moran Eye Center (Werner), Universityof Utah, Salt Lake City, Utah, USA.

No author has a financial or proprietary interest in any material ormethod mentioned.

Presented in part at the XXV Congress of the European Society ofCataract & Refractive Surgeons, Stockholm, Sweden, September2007.

Supported in part by unrestricted research grants to the BERI fromAlcon, AMO, WaveLight, Hoya, and Advanced Vision Science, andby a 2007 ESCRS research grant (Werner).

Jorg Nissen, Dipl.-Ing. (FH), Zentraleinrichtung Elektronenmikros-kopie, Technische Universitat, Berlin, Germany, assisted with thescanning electron microscopy analyses.

Corresponding author: Liliana Werner, MD, PhD, Berlin EyeResearch Institute, Alt-Moabit 98/99, D-10559, Berlin, Germany.E-mail:[email protected].

311LABORATORY SCIENCE: MICROEDGE STRUCTURE OF COMMERCIALLY AVAILABLE SQUARE-EDGED HYDROPHOBIC IOLS

J CATARACT REFRACT SURG - VOL 34, FEBRUARY 2008
mailto:[email protected]:[email protected]


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values for the C20.0 D control silicone IOL were729.3 mm2 and 1525.3 mm2 and for the C0.0 D controlsilicone IOL, 727.3 mm2 and 1512.7 mm2. The valuefor the square-edged PMMA IOL measured with the60 mm radius circle was similar (1.1 times larger) tothe value measured with the 40 mm radius circle. Thevalues for the C20.0 D and C0.0 D silicone controlIOLs measured with the 60mm radius circle were twicethe values measured with the 40 mm radius circle. In-

traocular lenses 10, 19, 23, 26, and 27 had area valuesmeasured with both reference circles that were smallerthan the corresponding values of the reference square-edged PMMA IOL, and IOLs 25 and 28 had values thatwere close to those of the reference IOL. Four of theabove-mentioned 7 IOLs were C20.0 D; the other 3were C0.0 D (nZ 1) or of the lowest dioptric poweravailable for the design (n Z 2). All were siliconeIOLs. The difference between acrylic and siliconeIOLs in the area measured with the AutoCAD systemwith the 40 mm radius circle and 60 mm radius circlewas statistically significant (P Z .0017 for both radii,

Wilcoxon 2-sample test). The area value measured

on all 7 IOLs with the 60 mm radius reference circlewas similar (maximum 1.2 times larger) to the corre-sponding value measured with the 40 mm circle, aswith the square-edged PMMA IOL. This was alsoobserved with IOLs 2, 8, and 22.

For IOLs 16 and 26, the area values measured withthe 60 mm radius circle were smaller than the valuesmeasured with the 40 mm radius circle. This can beexplained by the projection angles formed by the lat-

eral and posterior optic edges of the IOLs, which aresmaller than 90 degrees (Figure 3). In contrast, itappeared that the projection angle formed by the lat-eral and posterior optic edges of some IOLs was largerthan 90 degrees (Figure 3). This was especiallyobserved with IOL 6, leading to an area value with the60 mm radius circle that was 1.95 times larger than thevalue with the 40 mm radius circle. All remainingIOLs had area values with the 60 mm radius circlethat were from 1.3 to 2.0 times larger than the valueswith the 40 mm radius circle, and this was mostlya function of the convexity of the IOLs posterior optic

surface. For the following designs, the values

Figure 1. Scanning electron microscopy and AutoCAD analyses of 1 IOL used in this study. A: Perpendicular view of the optic edgeobtained with a magnification of25. All IOLs were oriented with the lateral edge up and the anterior and posterior surfaces on the rightand left sides, respectively. The SEM photographs of the 25 and 300 helped to control the orientation of the specimens. In this case, theIOL is equiconvex; that is, the distance between the right edge and the anterior surface and between the left edge and the posterior surface(bottom of photograph) is the same.B : Perpendicular view of the lateralposterior optic edge obtained with1000 magnification. The 30 mmbar was used to adjust the scale of the photograph into the AutoCAD program. Cand D: AutoCAD screens of the analyses of the pho-tograph inB using 40 mm radius and 60 mm radius circles, respectively. The magnification of the photographs on the screens was adjustedto incorporate the entire bottom-right quadrant of each circle. The area in red corresponds to the deviation from the ideal square, which

was measured as 281.4 mm2

and 520.4 mm2

, respectively.

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measured on theC20.0 D IOLs with both reference cir-cles were larger than the corresponding values mea-sured on the C0.0 D (or lowest available dioptricpower) IOLs: SN60WF, Z9000, Z9002, VA60BB, Hy-dromax, X-60, SoFlex SE, and Matrix Acrylic. The dif-ference between C20.0 D and C0.0 D (or lowestavailable dioptric power) IOLs regarding the area

measured with the AutoCAD system with 40 mm ra-dius circle and 60 mm radius circle was not statisticallysignificant (PZ .4419 and P Z .2616, respectively; Wil-coxon 2-sample test).

On SEM evaluation of the surface characteristics ofthe optic edge, IOLs 1 through 6 showed various de-grees of surface rugosity. Intraocular lenses 7, 8, 19,22 through 24, 27, and 28, as well as the square-edgedexperimental PMMA IOL, had mild to moderatedegrees of surface irregularities. Intraocular lenses9 through 18, 20, 21, 25, 26, 29, and 30, as well asthe control round-edged silicone IOLs, had over-

all smooth edge surfaces. Variations in surface

characteristics between the 2 dioptric powers analyzedwere found with the following designs: SA60AT,SN60WF, MA60AC/MA, Z9000, X-60, and AQ310Ai.

DISCUSSION

A square edge on the posterior optic surface was

found to be the most important IOL-related factorin PCO prevention. According to experimental stud-ies, this may be due to themechanical barrier effectexerted by the square edge,11,12 contact inhibition ofmigrating LECs at thecapsular bend created by thesharp optic edge,13,14 higher pressures exerted byIOLs with asquare-edged optic profile on the poste-rior capsule,15,16 or perhaps to various mechanismcombinations.

In a preliminary study,8 the optimum microedgedesign feature of an IOL to prevent LEC migrationwas evaluated in an in vitro setting. Plano C0.0 D

PMMA IOLs with 11 defined edge designs were

Table 1. Characteristics of the IOLs used in the study.

IOL Number IOL Model IOL Manufacturer Dioptric Power Optic Material Area 40*(mm2) Area 60 (mm2)

1 SA60AT Alcon 20.0 Acrylic 97.2 157.5

2 SA60AT Alcon 6.0 Acrylic 114.5 122.4

3 SN60WF Alcon (aspherical) 20.0 Acrylic 136.5 228.84 SN60WF Alcon (aspherical) 6.0 Acrylic 100.1 159.4

5 MA60AC Alcon 20.0 Acrylic 278.9 421.0

6 MA60MA Alcon 0.0 Acrylic 268.8 524.4

7 Z9000 AMO (aspherical) 20.0 Silicone 281.4 520.4




11 ZA9003 AMO (aspherical) 20.0 Acrylic 188.4 377.8

12 ZA9003 AMO (aspherical) 10.0 Acrylic 232.0 391.7

13 AR40e AMO 20.0 Acrylic 196.6 403.5

14 AR40M AMO 0.0 Acrylic 338.4 448.3

15 VA60BB Hoya 20.0 Acrylic 329.7 427.3

16 VA60BB Hoya 0.0 Acrylic 169.5 111.5

17 Hydromax Zeiss 19.0 Acrylic 116.5 211.2

18 Hydromax Zeiss 10.0 Acrylic 104.4 171.0

19 L200 WaveLight 20.0 Silicone 28.7 30.3

20 L450 WaveLight 20.0 Acrylic 138.8 287.3

21 X-60 AVS 20.0 Acrylic 268.0 395.0

22 X-60 AVS 0.0 Acrylic 202.7 232.7

23 SofPort AO B&L (aspherical) 20.0 Silicone 16.9 17.5

24 SofPort AO B&L (aspherical) 0.0 Silicone 89.3 123.7

25 SoFlex SE Bausch & Lomb 20.0 Silicone 40.1 39.9

26 SoFlex SE Bausch & Lomb 0.0 Silicone 4.8 0.2

27 AQ310Ai Staar (aspherical) 20.0 Silicone 19.7 20.1

28 AQ310Ai Staar (aspherical) 12.5 Silicone 38.9 39.9

29 Matrix acrylic Medennium 20.0 Acrylic 133.8 275.5

30 Matrix acrylic Medennium 0.0 Acrylic 69.5 131.8

*Edge area of deviation from an ideal square measured with the AutoCAD system using the 40 mm radius reference circle

Edge area of deviation from an ideal square measured with the AutoCAD system using the 60 mm radius reference circle




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manufactured for use in the preliminary study. To ob-tain different edge designs, the IOLs were removedfrom the tumble-polishing machine at different times.To evaluate the optic edges, standardized SEM pic-tures with an enlargement of 500 were taken of

1 IOL in each group. A digital computer system

(EPCO 2000 program)9 was used to evaluate the areaabove the edges on the SEM photographs. To achievethis, the area had to be defined as the deviation froman ideal rectangular projection. The edges ability tostop cell growth was observed by placing each IOL

into cell culture and observing bovine LEC growth

Figure 2.AutoCAD screens of the analyses (40 mm radius circle) of SEM photos obtained from the study IOLs.




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over 18 days on average. Only 3 groups of IOLs, thosewith the sharpest edge design, prevented the growthof LECs onto the visual axis of the IOL. The edge de-sign that effectively stopped cell growth was charac-

terized by an area above the edge, measured withthe EPCO system, of 13.5 mm2 at most.

In the current study, we used the AutoCADprogram to calculate the area of deviation from anideal square formed by the lateralposterior edges ofcurrently available square-edged hydrophobic IOLs.Measurement with this program was easy as it allows

great flexibility in the adjustment of the measurementscale and in the projection of structures of knowndimensions onto the photographs. Projection of the 2circles of known radius, with 2 perpendicular linescrossing their centers, helped us standardize the mea-surements. Indeed, on each1,000 SEM photograph,there is only 1 site for each circle where the 2 linestouch the lateral and posterior edges of the IOL. Weused the square-edged PMMA IOL from the prelimi-nary study8 as the reference IOL in the present study.Therefore, we remeasured the deviation area of thisIOL according to the technique described in this paper.The new cutoff limits obtained with the AutoCAD sys-tem were 34.0 mm2 and 37.5 mm2 for the 40 mm radiusreference circle and 60 mm radius reference circle,respectively. Intraocular lenses with deviation areasclose to the cutoff limits (or smaller) had similar valuesfor the 40mmand60 mm radius circles, while the others

had a tendency to present increasing values with thelarger radius, mostly as a function of the convexityof their posterior optic surface.

Of the 30 commercially available square-edged,hydrophobic IOLs evaluated, only 7 of 5 designs hadarea values that were smaller than, or close to, thoseof the reference square-edged PMMA IOL. To ourknowledge, there are no clinical studies in the litera-ture that directly compare these IOL designs (Z9002,L200, SofPort AO, SoFlex SE, and AQ310Ai) with theother designs shown inTable 1in terms of PCO pre-vention. The AQ310NV (nonaspherical version of the

AQ310Ai IOL used in this study) was comparedwith the MA60BM in a clinical study assessing postop-erativePCO with an anterior eye segment image ana-lyzer.17 No statistically significant difference wasfound between the 2 IOLs in PCO formation 12months postoperatively. Of the IOLs inTable 1withan OptiEdge configuration, only the C5.0 D Z9002had area values smaller than the reference square-edged PMMA IOL values. All other OptiEdge IOLs(C20.0 D Z9002, C20.0 D and C10.0 D Z9003,AR40e, and AR40M) had much higher values. How-ever, incorporation of the posterior square optic edge

design feature (present in the OptiEdge configuration)clearly improved the outcome of PCO formationwiththe Sensar IOL (AR40e), as shown by Buehl et al.2 ina prospective randomized study. The same findingwas seen in a study comparing the SoFlex SE IOLwith its predecessor, the SoFlex Li61U, with roundedges.5 Similarly, other studies comparing differentIOL designs in terms of PCO formation concludethat IOLs with a square optic edge provide betterresults, regardless of IOL material.1,3,4

If IOLs with different square microedge profiles pro-duce similar outcomes in terms of PCO formation, one

can conclude that other factors play a role in the

Figure 2(cont.)

Figure 3.Scanning electron microscopy photographs of IOLs 16, 26,and 6 (Table 1). The arrows on the bottom photographs show theprojection angle formed by the lateral and posterior edges of theoptic (continuous lines). The punctuated line delineates the theoretical90-degree angle.




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prevention of this complication. We believe the factorthat may play the most important role in evening outthe differences in the microedge profiles in our studyis shrink-wrapping of the IOL by the capsular bag,which enhances contact between the posterior IOLsurface and the posterior capsule. The amount of post-operative capsular bag shrinkage has been indirectlydetermined in clinical studies by the measurement ofthe diameter or area of the capsulorhexis openingatdifferent postoperative time points. Gonvers et al.18

prospectively evaluated 26 eyes with a single-piecePMMA IOL and 27 with plate-haptic silicone IOLs.In their study, the capsulorhexis used with the single-piece PMMA IOLs had a slight tendency to constrict,with a mean surface decrease of 0.59 G 2.16 mm2

(4.3%). The capsulorhexis used with plate-hapticsilicone IOLs showed a marked and statistically signif-icant constriction, with a mean decrease of 2.55 G

3.51 mm2 (14.4%). In another prospective study of 38eyes of 32 patientswith a 3-piece hydrophobic acrylicIOL, Kimura et al.19 found that the postoperativereduction ratio in capsulorhexis diameter was 2.14%at 1 week, 3.83% at 1 month,4.29% at 3 months, and5.03% at 6 months. Joo et al.20 evaluated 166 pseudo-phakic eyes 1 week and 1 and 3 months postopera-tively by measuring the capsule opening diameterwith an image-analysis system. The capsule openingdiameter was reduced by an average of 13.87% 3months after capsulorhexis. Tehrani et al.21 foundmean capsular bag shrinkage of 14.8% over a 6-month

postoperative period. They used a different approach.In their study, 58 eyes were implanted with a 3-piecehydrophobic acrylic IOL and a Koch capsule measur-ing ring (HumanOptics). This allowed measurementof the capsular bag diameter at different postoperativetime points.

Hayashi and Hayashi22 believe that of the differentIOL factors, optic material has the most significanteffect on the degree of anterior capsule contraction.They evaluated 331 patients scheduled for bilateralcataract surgery to compare the degree of anteriorcapsule contraction in fellow eyes that received IOLs

that were different with regard to the followingfactors: (1) optic material: hydrophobic acrylic opticversus silicone optic; (2) optic design: round edgeversus sharp edge; (3) haptic material: PMMA loopversus polyvinylidene fluoride loop; and (4) hapticmaterial and design: single-piece hydrophobic acrylicversus 3-piece PMMA haptic. The 2 IOLs implanted inthe fellow eyes of each patient had almost the samematerial and design except for the specific factor beingcompared. The mean percentage reduction of theanterior capsule opening area was only significantlygreater in eyes with a silicone optic IOL than in eyes

with a hydrophobic acrylic optic IOL. This relates to

the finding of significantly more capsule fibrosiswith silicone IOLs, as demonstrated in studies ofhuman eyes obtained post-mortem.23,24

We also found several differences in edge finishingbetween the IOLs analyzed, not only between differ-ent designs but also between different powers of thesame design. Modification of the finishing of the Acry-Sof IOLs, giving the side walls an unpolished ortextured appearance (so called frosting), was associ-ated with fewer complaints of glare phenomena thanIOLs of earlier design.25 Under 1000 magnification,this finishing was seen as various degrees of surfacerugosity. The surfaces of the other IOLs ranged frombeing overall smooth to having mild or moderateirregularities.

In summary, analysis of the microstructure of theoptic edge of currently available, square-edged hydro-phobic IOLs showed a large variation in the deviation

area from a perfect square and a large variation in theedge finishing. Both parameters varied between differ-ent IOL designs as well as between different dioptricpowers of the same IOL design. We believe that exist-ing and future clinical data will help us better under-stand the effect of microedge structure and design onreducing PCO. At present, a cutoff value to clinicallylabel an IOL as square edged should be sought. Thisstudy may help us better understand differences in mi-croedge structures.

We focused on commercially available hydrophobicIOLs only. Because of their low water content, we be-

lieve the SEM technique used did not cause significantalterations of the IOL edge profile. The microedgestructure of modern hydrophilic IOLs, most of whichhave a water content in the vicinity of 26%, may besignificantly modified during the vacuum requiredin standard SEM procedures. Therefore, we arecurrently evaluating the microedge structure of hydro-philic IOLs using an environmental SEM techniquethat operates with low vacuum and does not requireprevious coating.

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First author:Liliana Werner, MD, PhD

Berlin Eye Research Institute, Berlin,Germany, and John A. Moran Eye Center,University of Utah, Salt Lake City, Utah,USA



Evaluating and Defining the Sharpness of Intraocular Lenses

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