Effect of intraocular lens design on posterior capsule opacification

REVIEW/UPDATE

Effect of intraocular lens design on posterior capsule opacification Wolf Buehl, MD, Oliver Findl, MD, MBA

Posterior capsule opacification (PCO) remains the most common long-term complication after cataract surgery. Many studies have attempted to identify factors that influence the development of PCO. The aim of this systematic review based on Cochrane methodology was to summarize the effects of intraocular lens (IOL) geometry, including modifications of the IOL optic (especially optic edge design) and haptics, on the development of PCO. Twenty-six prospective randomized controlled trials with a follow-up of at least 12 months were included. In 5 of 7 studies, visual acuity was better in sharp-edged IOLs than in round-edged IOL. The PCO score was significantly lower with sharp-edged IOLs but did not differ significantly between 1-piece and 3-piece open-loop IOLs. Because of the significant difference in the PCO score, sharp-edged IOL optics should be preferred to round-edged IOL optics. J Cataract Refract Surg 2008; 34:1976–1985 Q 2008 ASCRS and ESCRS

Extracapsular cataract extraction (ECCE) with posterior chamber intraocular lens (IOL) implantation is the preferred surgical technique for the treatment of cataract in many countries, and most surgeons are now being trained in this method.1 However, leaving the posterior capsule intact during surgery may result in long-term complications, primarily posterior capsule opacification (PCO).2 People with PCO experience decreased visual acuity, impaired contrast sensitivity, and glare disability. Posterior capsule opacification is usually treated by creating an opening in the posterior capsule with a neodymium:YAG (Nd:YAG) laser or, rarely, by surgical capsulotomy. However, laser treatment may damage the IOL optic, transiently increase intraocular pressure, induce cystoid macular edema, and increase the incidence of retinal detachment; it often does not improve visualization of the peripheral retina.3 Additionally, Nd:YAG laser treatment is associated with high

Accepted for publication July 8, 2008. From the Department of Ophthalmology (Buehl, Findl), Medical University of Vienna, Vienna, Austria, and the Moorfields Eye Hospital (Findl), London, United Kingdom.

costs for the health-care system.4 The lack of availability of laser treatment is a major reason that ECCE with IOL implantation is not extensively used in the developing world. Interventions for preventing PCO include modifications in surgical technique explicitly to inhibit PCO, modifications in IOL design (material and geometry), implantation of additional devices, and pharmacological therapy. The role of IOL design is determined by 2 major factors: geometric and material properties. The introduction of sharp optic edges appears to reduce the incidence of PCO.5–7 It is unclear whether differences in the style of IOL loops (or haptics) play a role in PCO inhibition. An extensive body of data on interventions to reduce the incidence of PCO has been published. To draw conclusions about the various interventions to prevent PCO, a systematic review of randomized controlled trials was undertaken. This review is part of a Cochrane review, which is available in the Cochrane Library.8 The aim was to summarize the effects of modifying IOL design on PCO. The roles of IOL material, surgical technique, and pharmacological therapy were not included.

Neither author has a financial or proprietary interest in any material or method mentioned.

PATIENTS AND METHODS

Corresponding author: Oliver Findl, MD, MBA, Moorfields Eye Hospital NHS Foundation Trust, City Road, London EC1V 2PD, United Kingdom. E-mail: [email protected].

This review included only prospective randomized and controlled trials with a follow-up of at least 12 months in which different IOL designs were compared with each other

1976

Q 2008 ASCRS and ESCRS Published by Elsevier Inc.

Study Inclusion Criteria and Search Strategy

0886-3350/08/$dsee front matter doi:10.1016/j.jcrs.2008.07.029

REVIEW/UPDATE: IOL DESIGN AND PCO

or to ‘‘standard’’ IOLs. Participants in the trials were people with age-related cataract without prior sight-threatening ocular disease (glaucoma, corneal disease, uveitis, traumatic or complicated cataract [eg, zonular weakness], retinal disease, history of diabetes mellitus with diabetic retinopathy) who had cataract surgery with implantation of an IOL in the capsular bag. Trials were identified from the Cochrane Central Register of Controlled Trials, (CENTRAL) (which contains the Cochrane Eyes and Vision Group Trials Register) on the Cochrane Library, MEDLINE, EMBASE, and Latin American and Caribbean Literature on Health Sciences (LILACS).8 Reference lists of all identified trials and previous reviews were searched for additional trials. Manual searches of journals were not done specifically for this review. There were no language or date restrictions in the electronic searches for trials. The searches were last updated in January 2007.

Selection of Trials The authors reviewed the titles and abstracts resulting from the searches. Full articles of any trial that seemed to fit the inclusion criteria were obtained. To rate the level of evidence, 4 aspects of the trials were assessed using a standardized form provided by the Cochrane group. They included allocation concealment (was the randomization process performed and described adequately? for example, computergenerated randomization list, etc.), masking of participants and researchers (eg, examiner-masked, double-masked), detection bias (any differences between the comparison groups in outcome assessment?), and attrition bias (systematic error due to dropouts in one group; eg, after Nd:YAG capsulotomy [see below]).9 Only randomized studies were included. If there was any evidence of detection bias, the study was not included.

1977

Review Manager software (RevMan version 4.2 for Windows, Copenhagen, The Nordic Cochrane Centre, The Cochrane Collaboration, 2003) was used to analyze the data. RevMan is the software used to prepare and maintain Cochrane reviews. Data from studies collecting comparable outcome measures with similar follow-up times were summarized. Studies with missing standard deviation (SD) values were not excluded but could not be incorporated in the metaanalyses. Dichotomous outcomes were presented as odds ratios or risk ratios. Continuous outcomes were presented as the mean difference. A random-effects model (assuming between-study variability due to different study design and different study inclusion/exclusion criteria) was used, unless there were fewer than 3 trials in a comparison; if there were fewer than 3 trials, a fixed-effect model (assuming homogeneity) was used. Heterogeneity between trial results was examined using a chi-square test. Review Manager was also used to create the forest plots showing the results of the individual studies and the overall effect (mean difference between groups) and therefore the strength of the evidence in the included studies. In the forest plot, the metaanalyzed measure of effect is plotted as a diamond. The lateral points of the diamond indicate the confidence intervals for this estimate. If the points of the diamond overlap the line of no effect, the overall metaanalyzed result cannot be said to differ from no effect at the given level of confidence. Since different types of PCO scores (EPCO, POCO, AQUA system, and other scoring techniques)10 were used in the studies, an attempt to convert the values to a ‘‘common score’’ (0 to 100) was made to be able to compare these values in forest plots. It was presumed that the PCO scoring systems were linear systems. The EPCO score (scale 0 to 4), for example, was multiplied by 25; the AQUA score (0 to 10) was multiplied by 10 to attain a score of 0 to 100. Otherwise, it would not have been possible to perform metaanalyses for the PCO score.

Types of Outcome Measures The primary outcome measure for this review was best corrected visual acuity. The minimum length of follow-up was 12 months. Visual acuity was chosen as the primary outcome parameter because at the time the review was planned, more studies reporting visual acuity data than PCO scores were expected and because visual acuity would be easier to compare than different types of PCO scores. The secondary outcome measures were intensity of PCO as assessed with scoring techniques or quantification by image analysis and proportion of people needing capsulotomy (Nd:YAG laser capsulotomy rate). Assessment of PCO intensity/severity is complicated by their being no commonly accepted scoring method for PCO.10 There are several well-known subjective scoring systems, such as the Evaluation of PCO (EPCO) computer-aided scoring system, as well as semi-objective or objective systems, such as the posterior capsule opacification system (POCO) and Automated Quantification of After-Cataract (AQUA) system, both based on automated analysis of retroillumination PCO images. In addition, there is a frequently used objective PCO assessment method based on analysis of Scheimpflug images.11

Data Synthesis Data synthesis was performed according to the Cochrane Eyes and Vision Group review development guidelines.

LITERATURE REVIEW Three hundred twenty-six reports published between 1988 and 2006 were screened and 26 trials that met the inclusion criteria were identified (Table 1). As most of the included studies did not report longterm results, mainly 1-year data were used for the metaanalysis. Decimal values are used for best corrected distance visual acuity (BCDVA) and a PCO score of 0 to 100 for PCO intensity. The metaanalysis of the included studies showed significantly less PCO in sharp-edged than roundedged IOLs of the same optic material. Looking at the pooled results of all studies comparing sharp and round optic edges (irrespective of the optic material), there was also a clear difference between the 2 IOL edge designs, not only in PCO score and Nd:YAG rates, but also in BCDVA. Sharp Versus Round Optic Edges in Poly(Methyl Methacrylate) Intraocular Lenses One study6 compared sharp and round optic edges in poly(methyl methacrylate (PMMA) IOLs and found

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REVIEW/UPDATE: IOL DESIGN AND PCO

Table 1. Twenty-six studies that were included in the review.

Study* Bender12

Bilge13

Buehl14

Buehl15

Buehl5

Findl6

Hayashi11

Methods 1-piece (Alcon SA30AL) vs 3-piece (Alcon MA30BA) hydrohobic acrylic IOLs; prospective, randomized; 1-year follow-up; 35 drop-outs 1-piece (Alcon SA30AL) vs 3-piece (Alcon MA30BA) sharp-edged acrylic IOLs; randomized, prospective; 2-year follow-up AMO Sensar OptiEdge AR40e (sharp edge hydrophobic acrylic) vs AMO Sensar AR40 (round edge hydrophobic acrlyic) IOL; randomized, prospective, patient- and examiner-masked; 1-year follow-up; 8 drop-outs AMO ClariFlex OptiEdge (sharp edge silicone) vs AMO PhacoFlex SI40 (round edge silicone) IOL; prospective, randomized, patient- and examinermasked; 1-year follow-up; 12 drop-outs AMO Sensar OptiEdge AR40e (sharp edge hydrophobic acrylic) vs AMO Sensar AR40 (round edge hydrophobic acrlyic) IOL; randomized, prospective, patient- and examiner-masked; 3-year follow-up; 22 drop-outs Sharp vs round optic edges in PMMA IOLs (both Microplex MP260 by Dr Schmidt); prospective, randomized, patient- and examiner-masked; 5-year follow-up; 13 drop-outs Alcon MZ60BD (round edge PMMA) vs Allergan SI30NB (round edge silicone) vs MA60BM (sharp edge, hydrophobic acrylic) IOLs; 2- year follow-up; 28 drop-outs

Outcomes

Allocation concealment

Participants

Interventions

167 people with age-related cataract, 2 groups (115 in the MA30 group, 52 in the SA30 group); mean age 74; setting: UK and Germany 493 eyes of 519 people with age-related cataracts, 2 groups (256 eyes of 198 people in the 3-piece group; 240 eyes of 169 people in the 1-piece group); mean age 70; setting: Turkey 106 eyes of 53 people with bilateral age-related cataract (intra-individual comparison); mean age 72, setting: Austria

Phaco

POCO objective score, YAG rate

Unclear

Phaco

Own subjective PCO score, YAG rate

Unclear

Phaco

Subjective C objective PCO score (AQUA), BCVA, YAG rate

Adequate

104 eyes of 52 people with bilateral age-related cataract (intra-individual comparison); mean age 77, setting: Austria

Phaco

Subjective C objective PCO score (AQUA), BCVA, YAG rate

Adequate

106 eyes of 53 people with bilateral age-related cataract (intra-individual comparison); mean age 72, setting: Austria

Phaco

Subjective C objective PCO score (AQUA), BCVA, YAG rate

Adequate

64 eyes of 32 people with age-related cataract (intra-individual comparison); mean age 74; setting: Austria

Phaco

BCVA, AQUA objective PCO score, YAG rate

Adequate

240 eyes of 240 people with age-related cataract, 3 groups (80 each); mean age 69, setting: Japan

Phaco

Scheimpflug objective PCO score (Nidek anterior segment analyzer), BCVA, YAG rate

Adequate

(continued on next page)

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REVIEW/UPDATE: IOL DESIGN AND PCO

Table 1 (cont. ) Study* Hayashi16

Hayashi7

Hollick17

Hu¨tz18

Ku¨cu¨ksu¨mer19

Martin20

Mester21

Nejima22

Methods

Participants

Storz Hydroview (round edge hydrogel) vs Alcon MA60BM (sharp edge hydrophobic acrylic) IOL; prospective, randomized, patient- and examiner-masked; 2-year follow-up; 14 drop-outs AMO Sensar AR40e (sharp edge hydrophobic acrylic) vs AMO Sensar AR40 (round edge hydrophobic acrylic) IOL; prospective, randomized, double-blind; 2-year follow-up; 6 drop-outs Small (4.5–5.0 mm) vs large (6.0–7.0 mm) rhexis, standard cataract surgery with implantation of a Pharmacia 812A (round-edged PMMA) IOL; prospective, randomized; 1-year follow-up; 14 drop-outs Round-edged PMMA IOL with laser ridge vs round-edged PMMA IOL without ridge; prospective, randomized; 5- year follow-up; 56 drop-outs Alcon MA60BM (sharp edge hydrophobic acrylic) vs MemoryLens (roundedged PMMA) IOL; prospective, randomized, double-blind; 3- year follow-up; 29 drop-outs Effect of lens design and surgical placement on PCO (1-piece/3-piece, biconvex/plano-convex/ laser ridge, bag/sulcus placement); prospective, randomized, 1-year follow-up Pharmacia 911A (sharpedged silicone) vs Pharmacia SI40NB (round-edged silicone) vs Alcon MA60BM (sharpedged hydrophobic acrylic) IOL; prospective, randomized, multi-center; 1-year follow-up, 109 drop-outs (?) 1-piece(Alcon SA30AL) vs 3-piece (Alcon MA30BM) hydrophobic acrylic IOL; prospective, randomized, patient- and examiner-masked; 18-month follow-up; 4 drop-outs

Interventions

218 eyes of 109 people with bilateral age-related cataract (intra-individual comparison); mean age 71, setting: Japan

Phaco

150 eyes of 75 people with bilateral age-related cataract (intra-individual comparison); mean age 70, setting: Japan

Phaco

75 eyes of 75 people with age-related cataract, 2 groups (36 in the small capsulorhexis group, 39 in the large capsulorhexis group); mean age 73, setting: UK

Outcomes

Allocation concealment

Scheimpflug objective PCO score (Nidek anterior segment analyzer), BCVA, YAG rate Scheimpflug objective PCO score (Nidek anterior segment analyzer), BCVA, YAG rate

Adequate

Phaco

POCO objective PCO score, BCVA, contrast sensitivity, YAG rate

Unclear

100 eyes of 100 people with age-related cataract, 2 groups (50 each); mean age 71, setting: Germany

ECCE

Own PCO score (semiquantitative), BCVA

Unclear

100 eyes of 50 people with bilateral age-related cataract (intra-individual comparison); mean age 67, setting: Turkey

Phaco

Own subjective PCO score, BCVA, contrast sensitivity, YAG rate

Adequate

600 eyes of 600 people with age-related cataract in 12 groups; mean age 74; setting: USA

Phaco

Own subjective PCO score, BCVA, YAG rate

Adequate

576 eyes of 288 people with bilateral age-related cataract (intra-individual comparison: 911A vs. SI40NB or MA60BM); mean age 72, setting: Germany

Phaco

EPCO subjective PCO score

40 eyes of 20 people with bilateral age-related cataract (intra-individual comparison); mean age 71; setting: Japan

Phaco

Scheimpflug Adequate objective PCO score (Nidek anterior segment analyzer), BCVA

Adequate

Unclear

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REVIEW/UPDATE: IOL DESIGN AND PCO

Table 1 (cont. ) Study* Nejima23

Pohjalainen24

Sacu25

Sacu26

Sacu27

Sellmann28

Sundelin29

Wejde30

Methods

Participants

1-piece (Alcon SA60AT) vs 3-piece (Alcon MA60AC) sharp- edged hydrophobic acrylic IOL; prospective, randomized, patient- and examiner-masked; 1-year follow-up; 8 drop-outs SI30NB (round-edged silicone) vs MA60BM (sharp-edged hydrophobic acrylic) IOL; prospective, randomized; 2-year follow-up; 7 drop-outs 1-piece (Alcon SA30AL or SA60AT sharp-edged hydrophobic acrylic) vs 3-piece (Alcon MA30BA or MA60BM sharp-edged hydrophobic acrylic) IOL; prospective, randomized, patient- and examiner-masked; 2-year follow-up; 18 drop-outs AMO AR40e (sharp-edged hydrophobic acrylic) vs AMO AR40 (round-edged hydrophobic acrylic) vs AMO ClariFlex (sharp-edged silicone) vs AMO SI40 (round-edged silicone) IOL; prospective, randomized, patient- and examiner-masked; 1-year follow-up; 26 drop-outs Sharp vs round optic edges in a silicone IOL (both Microsil by Dr Schmidt); prospective, randomized, patient- and examiner-masked; 5-year follow-up; 27 drop-outs Convex-plano (Vision Care/3M 34R round-edged PMMA IOL) vs plano-convex (Vision Care/3M 34S round-edged PMMA IOL) optic, standard cataract surgery; randomized, prospective, multi-center AMO 911A (sharp-edged silicone) vs AMO SI40NB (round-edged silicone) IOL; prospective, randomized; 3-year follow-up; 33 drop-outs Pharmacia 809C (HSM-PMMA, round-edged) vs Allergan SI40NB (round-edged silicone) vs Alcon MA60BM (sharp-edged hydrophobic acrylic) IOL; randomized, prospective; 2-year follow-up; 17 drop-outs

Interventions

Outcomes

80 eyes of 40 people with bilateral age-related cataract (intra-individual comparison); mean age 70, setting: Japan

Phaco

80 eyes of 80 people with age-related cataract, 2 groups (40 each); mean age 67, setting: Finland

Phaco

104 eyes of 52 people with bilateral age related cataract (intra-individual comparison), 2 subgroups (large or small IOL diameter); mean age 74, setting: Austria

Phaco

Subjective C objective (AQUA) PCO score, BCVA, YAG rate

Adequate

210 eyes of 105 people with age-related cataract (intra-individual comparison sharp vs. round edge), 2 subgroups (53 in the AR40/ AR40e group, 52 in the SI40/ ClariFlex group); mean age 77, setting: Austria

Phaco

Own subjective fibrotic PCO score

Adequate

102 eyes of 51 people with bilateral age related-cataract; intra-individual comparison; mean age 73; setting: Austria

Phaco

Objective PCO score (AQUA), YAG rate

Adequate

505 eyes of 505 people with age-related cataract, 2 groups (254 in the 34S group, 251 in the 34R group); mean age 71, setting: USA

116 eyes of 116 people with age-related cataract, 2 groups (57 in the 911A group, 59 in the SI40 group); mean age 72; setting: Sweden 180 people with age-related cataract, 3 groups (61 in the HSM-PMMA group, 60 in the SI40 group, 59 in the MA60 group); mean age 74; setting: Sweden

Scheimpflug objective PCO score (Nidek anterior segment analyzer), BCVA BCVA, own subjective PCO score

Allocation concealment

ECCE or phaco Own subjective PCO score (PCO incidence)

D

Unclear

Unclear

Phaco

EPCO subjective score, YAG rate

Unclear

Phaco

EPCO subjective PCO score; YAG rate

Unclear

(continued on next page)

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REVIEW/UPDATE: IOL DESIGN AND PCO

Table 1 (cont. ) Study*

Methods

Participants

Westling31

JF1U (non-ridged) vs JF1LRU (laser ridge) round-edged PMMA IOL; prospective, randomized; 1-year follow-up; 48 drop-outs

WintherNielsen32

Pharmacia 700b (planoconvex, ridge, round-edged PMMA) vs Pharmacia 725a (biconvex, round-edged PMMA); heparin surface modified (HSM) vs unmodified; prospective, randomized, patient- and examiner-masked; 3-year follow-up Alcon MA30BA (3-piece sharpedged hydrophobic acrylic) vs Alcon SA30AL (1-piece sharp- edged hydrophobic acrylic) vs Pharmacia 911A (sharp-edged silicone) vs Alcon Crystal (round-edged PMMA) IOL; randomized, prospective; 1-year follow-up

Zemaitiene33

Interventions

Outcomes

Allocation concealment

319 eyes of 319 people with age-related cataracts, 2 groups (143 in the JF1U group, 176 in the JFLRU group); mean age 71; setting: Sweden 250 eyes of 246 people with age-related cataract, 4 groups (62 with unmodified 700b, 58 with HSM-700b, 60 with unmodified 725a, 70 with HSM-725a); mean age 75; setting: Denmark

ECCE

Own subjective PCO score, BCVA, YAG rate

Unclear

ECCE

Subjective PCO score, YAG rate

Unclear

165 eyes of 165 people with age-related cataract, 4 groups (46 in the MA30BA group, 38 in the SA30AL group, 39 in the 911A group, 42 in the PMMA group); mean age 67, setting: Lithuania

Phaco

EPCO subjective PCO score, YAG rate

Unclear

AQUA Z Automated Quantification of After-cataract: objective PCO scoring system; BCVA Z best corrected visual acuity; EPCO Z evaluation of PCO): subjective PCO scoring system; HSM-PMMA Z heparin-surface-modified PMMA; Hydrogel Z hydrophilic acrylic; IOL Z intraocular lens; PCO Z posterior capsule opacification; PMMA Z poly(methyl methacrylate); POCO Z posterior capsule opacification: semi-objective PCO scoring system *First author

no significant difference in BCDVA between the 2 groups (mean difference in visual acuity 0.05 [decimal], 95% confidence interval [CI] 0.18 to 0.08). The same study found a significantly higher PCO score in the round-edge group (mean difference in PCO score 28.3 [scale 0 to 100]; 95% CI 40.95 to 15.65) and a significantly higher Nd:YAG capsulotomy rate in the round-edge group (odds ratio 0.24; 95% CI 0.07 to 0.85). Sharp Versus Round Optic Edges in Acrylic Intraocular Lenses Two studies reported BCDVA.5,7 Visual acuity was significantly better in the sharp-edge group in one study5 and slightly, but not significantly, better in the second study.7 The mean difference was 0.06 (95% CI 0.01 to 0.12). This result is inconclusive due to statistical heterogeneity. Three studies7,14,26 reported PCO scores, all of them favoring the sharpedge group (mean overall effect 10.47; 95% CI 17.23 to 3.72; result inconclusive). Two studies5,7

reported Nd:YAG rates; both favored the sharp-edge group (odds ratio 0.07; 95% CI 0.02 to 0.32). Sharp Versus Round Optic Edges in Silicone Intraocular Lenses Visual acuity was significantly better in the sharpedge group in one study29; there was no difference in visual acuity in another.15 The mean difference was 0.06 (95% CI 0.00 to 0.12; result inconclusive). Five studies15,21,26,27,29 reported PCO scores; all favored the sharp-edge group. The mean overall effect was 8.24 (95% CI 14.04 to 2.44; result inconclusive). Four studies15,21,27,29 reported Nd:YAG rates; all favored the sharp-edge group. The mean overall effect (odds ratio) was 0.18 (95% CI 0.04 to 0.72). Sharp Versus Round Optic Edges Without Consideration of the Intraocular Lens Material Seven studies reported visual acuity results; 5 favored the sharp-edge group5,7,16,19,29 and there was

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Comparison: Outcome:

Sharp versus round optic edges (all materials)

BCDVA

Study

Sharp

Round

N

Mean (SD)

N

Mean (SD)

Weighted Mean Difference (Random)

Weighted Mean Difference (Random)

95% CI

95% CI

Buehl 2004

40

1.00 (0.13)

40

1.00 (0.19)

Buehl 2005

31

0.95 (0.15)

31

0.85 (0.25)

0.00 [ -0.07, 0.07 ] 0.10 [ 0.00, 0.20 ]

Findl 2005

32

0.76 (0.27)

32

0.81 (0.28)

-0.05 [ -0.18, 0.08 ]

Hayashi 2004

95

0.96 (0.20)

95

0.84 (0.25)

0.12 [ 0.06, 0.18 ]

Hayashi 2005

69

0.97 (0.20)

69

0.92 (0.20)

0.05 [-0.02, 0.12 ]

Kücüksümer 2000

21

0.93 (0.10)

21

0.75 (0.29)

0.18 [0.05, 0.31 ]

Sundelin 2005

57

0.83 (0.21)

59

0.59 (0.45)

Figure 1. Forest plot of mean difference in BCDVA between IOLs with round and sharp optic edges. The results of the available randomized controlled studies are shown as squares centered on the point estimate of the result of each study. The horizontal line shows the 95% CI. No overall effect estimate is shown because of statistical heterogeneity between studies.

0.24 [0.11, 0.37 ] -1.0

-0.5

0

0.5

1.0

Favours Round Favours Sharp

a forest plot of the mean difference in Nd:YAG laser capsulotomy rates between the groups.

no significant difference between the groups in 2 studies.6,15 The overall mean difference was 0.09 (95% CI 0.02 to 0.15; result inconclusive). Figure 1 shows a forest plot of the mean difference in BCDVA between sharp- and round-edged IOLs. Fifteen studies6,7,11,14,15,16,17,19,21,24,26,27,29,30,33 reported PCO scores; all but one favored the sharp-edge group. Three of the studies did not report SD values, including the one study that favored the round-edge group.24 The mean overall effect for the 11 remaining studies was 8.65 (95% CI 10.72 to 6.59; result inconclusive). Figure 2 shows a forest plot of the mean difference in PCO score between the groups. Eleven studies5,6,7,11,15,17,21,27,29,30 reported Nd:YAG rates; 10 favored the sharp-edge group and 1, the round-edge group.24 The mean overall effect (odds ratio) was 0.19 (95% CI 0.11 to 0.35). Figure 3 shows

Comparison: Outcome:

One-Piece Versus 3-Piece Acrylic Intraocular Lenses Three studies22,23,25 reported visual acuity results with 1-piece and 3-piece acrylic IOLs and found no significant difference between the groups. The mean difference was 0.0 (95% CI 0.04 to 0.04). Six studies reported PCO scores; 2 favored the 3-piece IOL,25,33 and the other 4 found no significant difference between the groups.12,13,22,23 The overall mean difference was 0.48 (95% CI 0.02 to 10.24). Figure 4 shows a forest plot of the mean difference in PCO score between 1-piece and 3-piece IOLs. There was no significant

Sharp versus round optic edges (all materials)

PCO score 0-100

Study

Sharp

Weighted Mean Difference (Random) 95% CI

Round

Weighted Mean Difference (Random) 95% CI

N

Mean (SD)

N

Mean (SD)

Buehl 2002

45

11.00 (7.50)

45

21.90 (12.70)

Buehl 2004

40

7.10 (6.50)

40

14.00 (11.30)

-6.90 [ -10.94, -2.86 ]

Findl 2005

32

22.90 (32.00)

32

51.20 (17.60)

-28.30 [ -40.95, -15.65 ]

-10.90 [ -15.21, -6.59 ]

Hayashi 1998

73

16.00 (10.30)

69

26.30 (12.20)

-10.30 [ -14.02, -6.58 ]

Hayashi 2004

95

9.00 (6.00)

95

20.00 (12.00)

-11.00 [ -13.70, -8.30 ]

Hayashi 2005

69

10.20 (3.00)

69

15.30 (4.00)

-5.10 [ -6.28, -3.92 ]

× Hollick 1999 Kücüksümer 2000 Mester 2004 × Pohjalainen 2002 Sacu 2004b

19

10.20

23

56.10

Not estimable

21

4.00 (10.30)

21

44.00 (30.00)

-40.00 [ -53.57, -26.43 ] -0.90 [ -1.66, -0.14 ]

73

0.20 (1.20)

73

1.10 (3.10)

16

15.60

22

11.40

Not estimable

53

6.50 (10.50)

53

23.30 (18.80)

-16.80 [ -22.60, -11.00 ]

Sacu 2005

24

12.00 (6.00)

24

24.00 (14.00)

-12.00 [ -18.09, -5.91 ]

Sundelin 2005

57

0.75 (5.54)

59

9.44 (17.98)

-8.69 [ -13.50, -3.88 ]

40

5.80

43

15.50

Not estimable

84

0.40 (0.20)

42

3.10 (0.50)

-2.70 [ -2.86, -2.54 ]

× Wejde 2003 Zemaitiene 2004

-100

-50

Favours Sharp

0

50

100

Favours Round

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Figure 2. Forest plot (similar to Figure 1) of PCO score difference between IOLs with round and sharp optic edges. Weighted mean differences were not calculated for the 3 studies marked with ‘‘x’’ because of missing SDs. No overall effect estimate was calculated due to statistical heterogeneity between studies.

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Comparison: Outcome:

Sharp versus round optic edges (all materials)

YAG capsulotomy rate

Study

Buehl 2004

Sharp

Round

Odds Ratio (Random)

Weight

n/N

n/N

95% CI

(%)

Odds Ratio (Random) 95% CI

0/40

1/40

3.4

0.33 [ 0.01, 8.22 ]

Buehl 2005

1/31

12/31

7.8

0.05 [ 0.01, 0.44 ]

Findl 2005

4/32

12/32

21.8

0.24 [ 0.07, 0.85 ]

Hayashi 1998

2/73

25/139

16.2

0.13 [ 0.03, 0.56 ]

Hayashi 2005

1/69

9/69

8.0

0.10 [ 0.01, 0.80 ]

Hollick 1999

0/19

3/22

3.8

0.14 [ 0.01, 2.95 ]

Mester 2004 Pohjalainen 2002 Sacu 2005

1/73

2/73

6.0

0.49 [ 0.04, 5.56 ] 4.35 [ 0.17, 114.05 ]

1/16

0/22

3.3

0/24

4/24

4.0

0.09 [ 0.00, 1.83 ]

Sundelin 2005 0/57

9/59

4.3

0.05 [ 0.00, 0.81 ]

Wejde 2003

3/38

20/95

21.5

0.32 [ 0.09, 1.15 ]

Total (95 % CI)

472

606

100.0

0.19 [ 0.11, 0.35 ]

0.1

0.2

0.5

1

Favours Sharp

2

5

Figure 3. Forest plot (similar to Figure 1) of difference in Nd:YAG capsulotomy rate between IOLs with round and sharp optic edges. The diamond at the bottom of the plot represents the overall estimate of the metaanalysis and the CI. The center of the diamond represents the pooled point estimate, and the horizontal tips represent the CI. Significance is achieved at the set level if the diamond is clear of the line of no effect.

10

Favours Round

Total events: 13 (Sharp), 97 (Round) Test for heterogeneity: chi-square = 8.35, df = 10,p = 0.59,I2 = 0.0% Test for overall effect: z = 5.41, p < 0.00001

Poly(Methyl Methacrylate) Intraocular Lenses With Ridge Versus Without Ridge

difference in the Nd:YAG rate in 3 studies (odds ratio 0.48; 95% CI 0.02 to 10.24).12,13,25

No study reporting visual acuity data that met the inclusion criteria of this review was found. One study31 found less presence of PCO in the group with a laser ridge 1 year after surgery (odds ratio 0.55; 95% CI 0.33 to 0.9). Three studies18,31,32 reported Nd:YAG rates; one favored the no-ridge group.32 However, the pooled estimate of effect did not show a significant difference between the groups (odds ratio 1.37; 95% CI 0.88 to 2.16).

One-Piece Versus 3-Piece Poly(Methyl Methacrylate) Intraocular Lenses There was no significant difference in the Nd:YAG capsulotomy rate in 1 study20 that compared 1-piece and 3-piece PMMA IOLs (odds ratio 0.94; 95% CI 0.59 to 1.51). Convex-Plano Versus Plano-Convex (Reverse Optic) Intraocular Lenses (Extracapsular cataract extraction)

DISCUSSION

One study28 found a significantly lower PCO incidence in the reverse-optic group (odds ratio 2.63; 95% CI 1.16 to 5.96). In the same study, which used an ECCE technique, there was no significant difference in the Nd:YAG rate at 1 year (odds ratio 1.18; 95% CI 0.51 to 2.72). Comparison: Outcome:

This systematic review included 26 prospective randomized and controlled clinical trials that looked at the effect of the IOL design on the development of PCO after cataract surgery. We compared visual acuity data, PCO scores, and Nd:YAG capsulotomy rates.

1-piece versus 3-piece design (Acrylic)

PCO score 0-100

Study

Bender 2004 × Bilge 2004

1-piece

Weighted Mean Difference (Random)

3-piece

N

Mean (SD)

N

Mean (SD)

38

9.90 (12.20)

94

11.40 (14.90)

95% CI

Weighted Mean Difference (Random) 95% CI -1.50 [ -6.41, 3.41 ]

252

10.07

267

10.56

Not estimable

Nejima 2004

20

12.50 (3.90)

20

11.30 (3.90)

1.20 [ -1.22, 3.62 ]

Sacu 2004a

52

15.00 (3.30)

52

12.00 (4.00)

3.00 [ 1.59, 4.41 ]

Zemaitiene 2004

38

0.60 (0.20)

46

0.30 (0.10)

0.30 [ 0.23, 0.37 ]

Nejima 2006

32

10.94 (2.34)

32

10.94 (2.34)

0.00 [-1.15, 1.15 ] -100

-50

Favours 1piece

0

50

100

Favours 3piece

J CATARACT REFRACT SURG - VOL 34, NOVEMBER 2008

Figure 4. Forest plot (similar to Figure 1) of PCO score difference between 1-piece and 3-piece acrylic IOLs. Weighted mean difference was not calculated for the study marked with ‘‘x’’ because of the missing SD. No overall effect estimate was calculated due to statistical heterogeneity between studies.

1984

REVIEW/UPDATE: IOL DESIGN AND PCO

It should be mentioned that the PCO scoring systems varied largely among the studies. Some authors used subjective scoring techniques, and some used objective methods or both. Objective methods should be preferred for evidence-based studies because the results can be compared more easily and usually do not depend on the examiner. A comparison of 4 commonly used scoring techniques has been published by our group.10 Apart from the PCO scores and Nd:YAG laser capsulotomy rates, there was little evidence of patient-related quality of life in the reviewed reports. However, it has been shown that many PCO scores correlate well with the PCO-induced loss of visual acuity and/or contrast sensitivity.34–37 Despite the different scoring techniques, we were able to convert the results to a common PCO score ranging from 0 (no PCO) to 100 (maximum PCO score) in most cases to calculate the overall effect (mean difference). However, we were unable to include the results of several studies in the metaanalysis because of missing SDs. In addition to the difference in PCO scoring methods, different follow-up periods were used in the studies. Nevertheless, we decided to combine the data in all studies, provided the follow-up was at least 1 year. Otherwise, there would have been too many subgroups and a metaanalysis of the data would not have been possible for most of the comparisons. As most studies did not report long-term results, only the 1-year data could be used for the metaanalysis. However, from several long-term studies performed by our group, we know that the PCO score difference between groups (especially between round- and sharp-edged IOL optics) usually remains significant over several years.5,6 Analysis of both PCO scores and visual acuity data is also complicated by the fact that Nd:YAG capsulotomies may lead to a bias in many studies due to missing visual acuity or PCO score values. The best way to handle this problem would be to estimate the missing PCO scores after a capsulotomy38; however, in most studies, there was no information about how the problem of Nd:YAG drop-outs was handled. We could provide clear evidence that sharp-edged IOLs develop significantly less PCO than round-edged IOLs of the same optic material. Looking at the pooled results of all studies comparing sharp and round optic edges (regardless of the optic material), there was also a clear difference between the 2 IOL edge designs, not only in PCO scores and Nd:YAG rates, but also in BCDVA. There was no clear evidence for a significant effect of a laser ridge in PMMA IOLs on the development of PCO (pooled results). In conclusion, this metaanalysis based on Cochrane methodology has shown that due to the highly significant difference between round and sharp IOL optics,

IOLs with sharp (posterior) optic edges should be preferred to round-edged IOLs of the same material for reduction of PCO and Nd:YAG capsulotomy rates and maximization of visual acuity. However, most round-edged IOL types have disappeared from the market. It has also become obvious that it is important to use a standardized method to quantify PCO. A common PCO scoring method would make the comparison of trials easier. REFERENCES 1. Riaz Y, Mehta JS, Wormald R, et al. Surgical interventions for age-related cataract. Cochrane Database Syst Rev 2006 Oct 18;(4);CD001323 2. Schaumberg DA, Dana MR, Christen WG, Glynn RJ. A systematic overview of the incidence of posterior capsule opacification. Ophthalmology 1998; 105:1213–1221 3. Javitt JC, Tielsch JM, Canner JK, Kolb MM, Sommer A, Steinberg EP. National outcomes of cataract extraction; increased risk of retinal complications associated with Nd:YAG laser capsulotomy; the Cataract Patient Outcomes Research Team. Ophthalmology 1992; 99:1487–1497; discussion by CP Wilkinson, 1497–1498 4. Apple DJ, Solomon KD, Tetz MR, Assia EI, Holland EY, Legler UFC, Tsai JC, Castaneda VE, Hoggatt JP, Kostick AMP. Posterior capsule opacification. Surv Ophthalmol 1992; 37:73– 116 5. Buehl W, Findl O, Menapace R, Sacu S, Kriechbaum K, Koeppl C, Wirtitsch M. Long-term effect of optic edge design in an acrylic intraocular lens on posterior capsule opacification. J Cataract Refract Surg 2005; 31:954–961 6. Findl O, Buehl W, Menapace R, Sacu S, Georgopoulos M, Rainer G. Long-term effect of sharp optic edges of a polymethyl methacrylate intraocular lens on posterior capsule opacification: A randomized trial. Ophthalmology 2005; 112:2004–2008 7. Hayashi K, Hayashi H. Posterior capsule opacification in the presence of an intraocular lens with a sharp versus rounded optic edge. Ophthalmology 2005; 112:1550–1556 8. Findl O, Buehl W, Bauer P, Sycha T. Interventions for preventing posterior capsule opacification. Cochrane Database Syst Rev 2007;(3):CD003738 9. Higgins JPT, Green S, eds. Assessment of study quality. Cochrane Handbook for Systematic Reviews of Interventions 4.2.6 [updated September 2006. In: The Cochrane Library. Chichester, UK, John Wiley & Sons; Section 6, Issue 4, 2006 10. Findl O, Buehl W, Menapace R, Georgopoulos M, Rainer G, Siegl H, Kaider A, Pinz A. Comparison of 4 methods for quantifying posterior capsule opacification. J Cataract Refract Surg 2003; 29:106–111 11. Hayashi H, Hayashi K, Nakao F, Hayashi F. Quantitative comparison of posterior capsule opacification after polymethylmethacrylate, silicone, and soft acrylic intraocular lens implantation. Arch Ophthalmol 1998; 116:1579–1582 12. Bender LE, Nimsgern C, Jose R, Jayaram H, Spalton DJ, Tetz MR, Packard RB, Meacock W, Boyce J. Effect of 1-piece and 3-piece AcrySof intraocular lenses on the development of posterior capsule opacification after cataract surgery. J Cataract Refract Surg 2004; 30:786–789 ¨ , Akin T, U ¨ nsal U. The effects of three-piece or 13. Bilge AH, Aykan U single-piece acrylic intraocular lens implantation on posterior capsule opacification. Eur J Ophthalmol 2004; 14:375–380 14. Buehl W, Findl O, Menapace R, Rainer G, Sacu S, Kiss B, Petternel V, Georgopoulos M. Effect of an acrylic intraocular

J CATARACT REFRACT SURG - VOL 34, NOVEMBER 2008

1985

REVIEW/UPDATE: IOL DESIGN AND PCO

15.

16.

17.

18.

19.

20.

21.

22.

23.

24.

25.

26.

27.

lens with a sharp posterior optic edge on posterior capsule opacification. J Cataract Refract Surg 2002; 28:1105–1111 Buehl W, Menapace R, Sacu S, Kriechbaum K, Koeppl C, Wirtitsch M, Georgopoulos M, Findl O. Effect of a silicone intraocular lens with a sharp posterior optic edge on posterior capsule opacification. J Cataract Refract Surg 2004; 30:1661–1667 Hayashi K, Hayashi H. Posterior capsule opacification after implantation of a hydrogel intraocular lens. Br J Ophthalmol 2004; 88:182–185 Hollick EJ, Spalton DJ, Ursell PG, Pande MV, Barman SA, Boyce JF, Tilling K. The effect of polymethylmethacrylate, silicone, and polyacrylic intraocular lenses on posterior capsular opacification 3 years after cataract surgery. Ophthalmology 1999; 106:49–54; discussion by RC Drews, 54–55 Hu¨tz W. Prospektive Studie u¨ber den Nachstar nach 5 Jahren bei Intraokularlinsen mit und ohne Laserridge. [Secondary cataract in intraocular lenses with and without laser ridge, a prospective study with 5 years follow-up.]. Klin Monatsbl Augenheilkd 1993; 203:104–107 ¨ F. Posterior capKu¨c¸u¨ksu¨mer Y, Bayraktar S x, S xahin S, Yılmaz O sule opacification 3 years after implantation of an AcrySof and a MemoryLens in fellow eyes. J Cataract Refract Surg; 26:1176–1182 Martin RG, Sanders DR, Souchek J, Raanan MG, DeLuca M. Effect of posterior chamber intraocular lens design and surgical placement on postoperative outcome. J Cataract Refract Surg 1992; 18:333–341 Mester U, Fabian E, Gerl R, Hunold W, Hu¨tz W, Strobel J, Hoyer H, Kohnen T. Posterior capsule opacification after implantation of CeeOn Edge 911A, PhacoFlex SI-40NB, and AcrySof MA60BM lenses; one-year results of an intraindividual comparison multicenter study. J Cataract Refract Surg 2004; 30:978–985 Nejima R, Miyata K, Honbou M, Tokunaga T, Tanabe T, Sato M, Oshika T. A prospective, randomised comparison of single and three piece acrylic foldable intraocular lenses. Br J Ophthalmol 2004; 88:746–749 Nejima R, Miyai T, Kataoka Y, Miyata K, Honbou M, Tokunaga T, Kawana K, Kiuchi T, Oshika T. Prospective intrapatient comparison of 6.0-millimeter optic single-piece and 3-piece hydrophobic acrylic foldable intraocular lenses. Ophthalmology 2006; 113:585–590 Pohjalainen T, Vesti E, Uusitalo RJ, Laatikainen L. Posterior capsular opacification in pseudophakic eyes with a silicone or acrylic intraocular lens. Eur J Ophthalmol 2002; 12:212–218 Sacu S, Findl O, Menapace R, Buehl W, Wirtitsch M. Comparison of posterior capsule opacification between the 1-piece and 3-piece Acrys of intraocular lenses; two-year results of a randomized trial. Ophthalmology 2004; 111:1840–1846 Sacu S, Menapace R, Buehl W, Rainer G, Findl O. Effect of intraocular lens optic edge design and material on fibrotic capsule opacification and capsulorhexis contraction. J Cataract Refract Surg 2004; 30:1875–1882 Sacu S, Menapace R, Findl O, Kiss B, Buehl W, Georgopoulos M. Long-term efficacy of adding a sharp posterior

28.

29.

30.

31.

32.

33.

34.

35.

36.

37.

38.

optic edge to a three-piece silicone intraocular lens on capsule opacification: five-year results of a randomized study. Am J Ophthalmol 2005; 139:696–703 Sellman TR, Lindstrom RL. Effect of a plano-convex posterior chamber lens on capsular opacification from Elschnig pearl formation; International Cataract Surgery Study Group. J Cataract Refract Surg 1988; 14:68–72 Sundelin K, Shams H, Stenevi U. Three-year follow-up of posterior capsule opacification with two different silicone intraocular lenses. Acta Ophthalmol Scand 2005; 83:11–19 Wejde G, Kugelberg M, Zetterstro¨m C. Posterior capsule opacification: comparison of 3 intraocular lenses of different materials and design. J Cataract Refract Surg 2003; 29:1556– 1559 Westling AK, Calissendorff BM. Factors influencing the formation of posterior capsular opacities after extracapsular cataract extraction with posterior chamber lens implant. Acta Ophthalmol (Copenh) 1991; 69:315–320 Winther-Nielsen A, Johansen J, Pedersen GK, Corydon L. Posterior capsule opacification and neodymium:YAG capsulotomy with heparin-surface-modified intraocular lenses. J Cataract Refract Surg 1998; 24:940–944 Zˇemaitiene_ R, Jasˇinskas V, Barzdziukas V, Auffarth GU: [Prevention of posterior capsule opacification using different intraocular lenses (results of one-year clinical study)]. [Lithuanian] Medicina (Kaunas) 2004; 40:721–730 Buehl W, Sacu S, Findl O. Association between intensity of posterior capsule opacification and visual acuity. J Cataract Refract Surg 2005; 31:543–547 Buehl W, Sacu S, Findl O. Association between intensity of posterior capsule opacification and contrast sensitivity. Am J Ophthalmol 2005; 140:927–930 Hayashi K, Hayashi H, Nakao F, Hayashi F. Correlation between posterior capsule opacification and visual function before and after neodymium: YAG laser posterior capsulotomy. Am J Ophthalmol 2003; 136:720–726 Meacock WR, Spalton DJ, Boyce J, Marshall J. The effect of posterior capsule opacification on visual function. Invest Ophthalmol Vis Sci 2003; 44:4665–4669. Available at: http://www. iovs.org/cgi/reprint/44/11/4665. Accessed July 10, 2008 Buehl W, Heinzl H, Mittlboeck M, Findl O. Statistical problems caused by missing data resulting from neodymium:YAG laser capsulotomies in long-term posterior capsule opacification studies; problem identification and possible solutions. J Cataract Refract Surg 2008; 34:268–273

First author: Wolf Buehl, MD Department of Ophthalmology Medical University of Vienna, Vienna, Austria

J CATARACT REFRACT SURG - VOL 34, NOVEMBER 2008