Efficacy and safety of capsular bending ring implantation to prevent posterior capsule opacification

ARTICLE

Efficacy and safety of capsular bending ring implantation to prevent posterior capsule opacification Three-year results of a randomized clinical trial Rupert Menapace, MD, Stefan Sacu, MD, Michael Georgopoulos, MD, Oliver Findl, MD, Georg Rainer, MD, Okihiro Nishi, MD

PURPOSE: To determine whether a capsular bending ring (CBR) with a rectangular cross-section and sharp edges moves the barrier to the very equator and avoids contact between the capsulorhexis and optic to prevent posterior capsule opacification (PCO) and anterior capsule fibrosis. SETTING: Department of Ophthalmology, Medical University of Vienna, Vienna, Austria. METHODS: A 0.7 mm high, open poly(methyl methacrylate) CBR was implanted in 60 eyes (patients) in a prospective randomized intraindividual trial. The impact of additional CBR implantation on PCO and anterior capsule fibrosis was compared to that of intraocular lens (IOL) implantation alone using objective scoring. RESULTS: No CBR-related surgical complications occurred. The objective PCO score and area were statistically significantly reduced in the CBR group. In patients with complete follow-up, the mean PCO score (scale 1 to 10) at 1, 2, and 3 years was 0.8, 1.7, and 2.1, respectively, in the CBR group and 2.6, 3.9, and 4.6, respectively, in the no-CBR group. The number of quadrants affected by PCO was 0.9, 1.5, and 1.8 versus 3.2, 3.8, and 3.8. Barrier failures with the CBR were caused by the inherent slight edge blunting and occasional eyelet gaping. Laser capsulotomies were performed in the no-CBR group only. Capsule stress folds and fibrotic anterior capsule opacification were also greatly reduced. The best corrected visual acuity was better in the CBR group. CONCLUSIONS: Capsular bending ring implantation was an effective and safe adjunct to in-the-bag IOL fixation. With improvements in technology and design securing exquisitely sharp edges and circumferential capsular bending independent of the capsular bag diameter, this concept has the potential to prevent PCO and anterior capsule fibrosis. J Cataract Refract Surg 2008; 34:1318–1328 Q 2008 ASCRS and ESCRS

Adding a sharp posterior edge to intraocular lenses (IOLs) has significantly reduced the formation of regeneratory after-cataract on the posterior capsule behind the optic and the subsequent need for neodymium:YAG (Nd:YAG) laser capsulotomy.1–4 However, the barrier effect of sharp-edged IOLs occasionally fails and generally wears off over time. This is caused by 2 weaknesses of the concept. The first is that the persistence of the barrier effect of the posterior optic edge is dependent on the formation of a permanent circumferential capsular bend at the posterior optic edge, which results from capsular bag closure. Capsular fusion and subsequent bend formation are counteracted by broad haptic junctions (junction phenomenon) or by overly 1318

Q 2008 ASCRS and ESCRS Published by Elsevier Inc.

long and rigid loops that ovally distort the capsular bag and are sometimes incomplete (primary barrier failure) for unknown reasons. In the long run, fusion and bending may secondarily be reversed by the proliferative pressure of delayed Soemmering ring formation if collagenous sealing of the capsular leaves at the optic rim is not firm enough to resist redivision (secondary barrier failure). Second, a prerequisite to bend formation is circumferential overlap of the optic by the anterior capsule leaf, which is not always achieved. Incomplete overlap results in early retro-optical lens epithelial cell (LEC) ingrowth. Capsulorhexis–optic overlap that is too small may give way to anterior capsule retraction 0886-3350/08/$dsee front matter doi:10.1016/j.jcrs.2008.04.034

CAPSULAR BENDING RING IMPLANTATION TO PREVENT PCO

with consequent anterior optic buttonholing and fibrosis of the retro-optical posterior capsule, while overlap that is too large unnecessarily reduces the free optic zone, especially when fibrotic capsulorhexis contraction ensues.5 This explains the 10-year cumulative Nd:YAG laser capsulotomy rate of more than 40% found with the most widely used hydrophobic acrylic IOL (L. Vock, MD, et al., ‘‘PCO Preventive Effect of Sharp-Edged Hydrophobic Acrylic IOLs and RoundEdged Silicone IOLs 10 Years After Surgery,’’ presented at the XXV Congress of the European Society of Cataract & Refractive Surgeons, Stockholm, Sweden, September 2007. Abstract available at: http://www. escrs.org/EVENTS/07Stockholm/sessiondetails.asp? idZ1617&categoryZFree&sessiondateZ9/9/2007. Accessed May 15, 2008). Two additional downsides should also be considered. First, the capsular bag outside the optic may fill up with pearls that impede visibility of the peripheral retina for diagnosis and treatment. Second, the sharp optic edge can induce dysphotopsia, which has been judged to be the major postoperative complaint with modern IOLs.6 In 1996, Nishi and Menapace developed a capsular ring implant, the capsular bending ring (CBR), that has a rectangular profile, a thickness of 0.15 to 0.20 mm, and a height of 0.7 mm (Figure 1, A and B). As opposed to the closed endocapsular silicone ring introduced by Hara et al.,7 the newer ring is open and made from poly(methyl methacrylate) (PMMA). The outer ring diameter is 11.0 mm. The ring is not polished more than necessary to avoid incising the capsule during implantation. In addition to shifting the capsular bend into the equator, the high profile prevents the capsular bag from collapsing and the anterior capsule leaf from establishing contact with the optic and posterior capsule (capsular distance ring) (Figure 2). Thus, the following purposes should be met: (1) no ingrowth of equatorial LECs onto the posterior capsule, including the extreme periphery outside the IOL optic rim; and (2) no fibrotic whitening or shrinkage of the anterior capsule leaf. In addition, formation of stretch folds in the posterior capsule

Accepted for publication April 23, 2008. From the Department of Ophthalmology, Medical University of Vienna, Vienna, Austria. No author has a financial or proprietary interest in any material or method mentioned. Corresponding author: Rupert Menapace, MD, University of Vienna Medical School, Department of Ophthalmology, Waehringer Guertel 18-20, 1090 Vienna, Austria. E-mail: rupert.menapace@ meduniwien.ac.at.

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Figure 1. A: Capsular bending ring type 14E. Gonioscopic views (top) and scanning electron microscopy photomicrograph (bottom left) showing slight edge blunting (arrow) after mild tumble polishing. B: Schematic of CBR type 14E.

should be prevented. These features should result in the full preservation of transparency of the posterior capsule and the anterior capsule independent of capsulorhexis–optic overlap and optic-rim design. We performed a prospective randomized bilateral clinical study to evaluate the safety and efficacy of the CBR. PATIENTS AND METHODS Sixty patients with bilateral cataract requiring surgery in otherwise healthy eyes were included in the study. Patients were recruited from a continuous cohort at the Department of Ophthalmology, Vienna General Hospital, Medical University of Vienna. Inclusion criteria were bilateral age-related cataract and good overall physical constitution.

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Figure 2. Mechanism of CBR action: capsule bending in equator. The CBR also counteracts anterior capsule fibrosis and PCO outside the optic rim (CBR Z capsular bending ring; IOL Z intraocular lens).

Exclusion criteria were a history of other ocular disease or intraocular surgery, previous laser treatment, diabetes requiring medical control, glaucoma, and retinal pathology that would make a postoperative visual acuity of 20/40 (decimal equivalent 0.5) or better unlikely. Written consent was obtained from all patients before their entry into the study. All the research and measurements followed the tenets of the Declaration of Helsinki, and the Ethics Committee of the Medical University of Vienna approved the protocol. Each patient received a CBR (type 1-E, Morcher) in 1 eye; no ring was implanted in the other eye to allow an intraindividual comparison. Time between surgeries was between 1 week and 3 weeks. The procedure to be performed on the first operated eye of each patient (CBR yes/no) was randomly assigned before patient recruitment. The Hydroview H60M IOL (Bausch & Lomb) was implanted in all eyes. The IOL has a 3-piece design with a biconvex hydrophilic acrylic optic and PMMA loops. Surgeries were performed by the same surgeon (R.M.) using the following technique: temporal limbo-corneal incision, 5.0 to 5.5 mm capsulorhexis, hydrodissection, phacoemulsification, cortex aspiration, expansion of the capsular bag with a high-viscosity ophthalmic viscoelastic device (OVD) (sodium hyaluronate 1.4% [Healon GV]), wound enlargement to 3.5 to 3.8 mm depending on IOL dioptric power, tangential insertion of a CBR in the capsular bag fornix using a bimanual technique or an injector, and implantation of the IOL with a folding forceps. Until completion of the lens content evacuation, the surgeon was unaware of whether the eye operated on was scheduled to receive a CBR. Diclofenac, phenylephrine 2.5%, tropicamide 0.5%, and cyclopentolate 1% eyedrops were instilled 1 to 2 hours before surgery to achieve maximum mydriasis. Postoperatively, the eyes were treated with prednisolone acetate 0.5% (Ultracortenol) and diclofenac (Voltaren) 4 times a day for 1 month. Patients were examined after 1, 2, and 3 years and the eyes systematically evaluated. Examiners were masked to which eye had received the CBR. For the documentation of regeneratory PCO, retroilluminated digital images focused on the posterior capsule were taken in a standardized fashion with a digital camera setup similar to that used by Spalton et al.8 For objective PCO evaluation of the retroillumination photographs, the Vienna AQUA automated image-analysis system was used. The system’s software calculates the entropy (grade of disorder) on a bit map. This value is converted into a score between 0 and 10 (0 Z clear capsule; 10 Z severe PCO). The fully automated system has been shown to correlate well with

subjective scoring of PCO as well as with the EPCO 2000 semiobjective evaluation system.9 Mean objective PCO scores were obtained for eyes with a CBR (CBR group) and eyes without a CBR (no-CBR group). The results between groups were compared and the differences calculated. The level of statistical significance was determined using the repeated-measures t test and the chi-square test; P values of 0.05 or less were considered statistically significant. Eyes that had an Nd:YAG laser capsulotomy were excluded from evaluation. These dropouts were compensated for by calculating PCO scores for the following 3 assumptions: regeneratory PCO score after Nd:YAG laser capsulotomy (1) remained unchanged (bestcase scenario), (2) increased to maximum of 10 (worst-case scenario), or (3) progressed as observed before (extrapolated scenario), the latter being considered the most likely. The criteria for the necessity of Nd:YAG laser capsulotomy were patient-reported complaints and/or a visual acuity of 20/25 (decimal equivalent Z 0.8) or worse attributable to PCO on slitlamp examination.

RESULTS The mean age of the 60 patients (40 women, 20 men) initially enrolled in the study was 77.3 years G 10.6 (SD) (range 37 to 91 years). There was no statistically significant difference in IOL power between the CBR group and no-CBR group (mean 21.0 G 2.8 diopters [D] versus 21.2 G 2.9 D) (P Z .34). Surgery was uneventful in all eyes. Of the 60 patients, 50 were available for the 1-year follow-up examination. Of the 10 patients not available, 1 had died before the 1-year follow-up, 3 were unable or refused to attend the follow-up, and 6 could not be reached. Forty-three patients presented for the 2-year follow-up evaluation and 31 patients for the 3-year evaluation; 25 patients completed all 3 follow-up evaluations. Objective Posterior Capsule Opacification Score At 1 year, the mean objective regeneratory PCO score (scale 0 to 10) was 0.90 G 0.8 in the CBR group and 2.43 G 1.2 in the no-CBR group (P!.001; n Z 49, PCO data of 1 patient excluded from statistical evaluation for Nd:YAG laser capsulotomy performed elsewhere before 1-year follow-up). Forty-one of the 49 patients (84%) had less regeneratory PCO in the CBR eye, and 8 patients (16%) had similar or slightly more regeneratory PCO in the CBR eye (Figure 3, A). Twenty-nine eyes in the CBR group and 2 eyes in the no-CBR group had a PCO score of less than 1. Maximum observed regeneratory PCO scores were 3.1 in the CBR group and 5.5 in the no-CBR group. At 2 years, the mean objective regeneratory PCO score was 1.64 in the CBR group and 3.62 in the noCBR group (P!.001; n Z 38, PCO data of 5 patients excluded from statistical evaluation for Nd:YAG laser capsulotomy before 2-year follow-up). Thirty-five of

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the 38 patients (92%) had less regeneratory PCO in the CBR eye. At 3 years, the mean objective regeneratory PCO score was 2.2 in the CBR group and 4.1 in the no-CBR group (P!.001; n Z 19, PCO data of 13 patients excluded from statistical evaluation for Nd:YAG laser capsulotomy before 3-year follow-up). Fourteen of the 19 patients (74%) had less regeneratory PCO in the CBR eye. The mean objective regeneratory PCO score in patients who completed all follow-up examinations through 3 years (n Z 25) was 0.8 and 2.6 at 1 year, 1.7 and 3.9 at 2 years, and 2.1 and 4.6 at 3 years in the CBR group and no-CBR group, respectively (P!.001). Figure 3, B, shows the course of PCO scores in both groups over the 3 postoperative years. Post hoc power analysis for the observed standard deviation of the 25 patients (50 eyes) completing all 3 follow-up examinations was performed. A clinically relevant difference of regeneratory PCO score of 1.0 (ie, 10%) could be calculated with a 100%, 98%, and 99% power for 1 year, 2 years, and 3 years, respectively, at an a level of 5%. Of the subgroup of 36 patients subjectively scored at 1 year and 2 years, most of those in the CBR group had no change in PCO and most of those in the no-CBR group had an increase (Figure 3, C). Figure 4 shows the retroillumination images of a representative case from the image data set. Quadrants of the Optic Area Affected by Regeneratory Posterior Capsule Opacification

Figure 3. A: Comparative prevalence of regeneratory PCO at 1 year: 84% of eyes in the CBR group showed less PCO than eyes in the noCBR group. B: Course of PCO score in both groups over 3 years after surgery. Dashed lines bordering shaded areas represent the worstcase and best-case regeneratory PCO scenario in eyes having Nd:YAG laser capsulotomy (inferior line Z regeneratory PCO rate supposed to remain unchanged; superior line Z regeneratory PCO rate supposed to progress to maximum score of 10; bold line Z extrapolated regeneratory PCO score). C: Change in subjective PCO scores from 1 year to 2 years (CBR Z capsular bending ring; PCO Z posterior capsule opacification; rPCO Z regeneratory PCO).

In the CBR group, significantly fewer quadrants of the optic area (0 to 4) were affected by regeneratory PCO on subjective evaluation. A median of 1.0 G 1.2 quadrants of the optic area were affected by regeneratory PCO in the CBR group and 3.0 G 1.1 quadrants in the no-CBR group at the 1-year follow-up (P!.001). In 16 (33%) of 49 patients in the CBR group and 2 (4%) of the 49 patients in the no-CBR group, no quadrant of the optic area was affected by regeneratory PCO (P!.001). In 1 patient (2%) in the CBR group and 18 patients (36%) in the no-CBR group, all 4 quadrants of the optic area were affected by regeneratory PCO (P!.001). Figure 5, A, shows the proportions of eyes with regard to the number of quadrants of the optic area affected by regeneratory PCO 1 year after surgery. Results of patients who completed all follow-up examinations through 3 years (n Z 25) are shown in Figure 5, B. The mean quadrants of the optic area affected by regeneratory PCO was 0.9 in the CBR group and 3.2 in the no-CBR group at the 1-year follow-up; 1.5 and 3.8, respectively, at 2 years; and 1.8 and 3.8, respectively, at 3 years (Figure 5, B, top). The difference

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Figure 4. Example showing the clinical efficacy of the CBR (CBR Z capsular bending ring).

between the 2 groups was highly statistically significant at all follow-ups (P!.001) (Figure 5, B, bottom). Distance of Eyelets Eyelet distance measurements were obtained in 23 eyes (46%) in the CBR group evaluated at 1 week and 1 year. Gonioscopic views and the relative positioning of the eyelets are shown in Figure 6. At 1 week, close eyelet attachment (distance 0.0 to 0.5 mm) was found in 6 eyes (26%). A distance of 0.5 to 1.0 mm was found in 7 eyes (30%) and a distance of 1.0 to 2.0 mm, in 9 eyes (39%). One eye had eyelet overlap. By 1 year, the number of eyes with close eyelet attachment had risen to 16 (70%) and the number of eyes with a distance greater than 1.0 mm had decreased to 3 (13%). Three eyes had eyelet overlap of less than 0.5 mm. In the only eye with an overlap exceeding 0.5 mm, extensive capsulorhexis–optic contact had caused substantial fibrotic shrinkage of the capsulorhexis. Neodymium:YAG Laser Capsulotomy Rate In the no-CBR group, 1 Nd:YAG laser capsulotomy was performed before the 1-year follow-up and 2 capsulotomies were performed after the 1-year follow-up; no eye in the CBR group required Nd:YAG treatment during that time. Before 2 years, 2 additional patients in the no-CBR group required Nd:YAG laser capsulotomy. After the 2-year follow-up, 7 additional patients in the no-CBR group and 1 in the CBR group required a capsulotomy. At the 3-year follow-up, 4 additional eyes in the no-CBR group had an Nd:YAG laser capsulotomy.

Best Corrected Visual Acuity There was no difference between the CBR group and no-CBR group in mean best corrected visual acuity (BCVA) 1 week after surgery. From 1 to 3 years, BCVA was better in the CBR group; the difference was statistically significant at 1 and 2 years (Figure 7).

Differences in Capsular Stress Folds and Capsule–Optic Interspaces Capsular Stress Folds. One week postoperatively, 2 eyes (3.3%) in the CBR group and 47 eyes (78.3%) in the no-CBR group had traction folds in the posterior capsule; the difference was statistically significant. Of the 40 eyes evaluated after 1 year, none in the CBR group and 21 (42%) in the no-CBR group had haptic-induced stress folds in the posterior capsule (P!.001).

Capsulorhexis–Optic Clearance. In the 41 eyes (82%) in the CBR group seen after 1 year, the anterior capsule was at a distinct distance from the anterior optic surface. In the 9 eyes (18%) in the CBR group with capsule–optic contact, the capsulorhexis diameter was smaller than 5.0 mm and/or the lens power was higher and thus the optic was thicker than the average. No eye in the no-CBR group had an interspace.

Posterior Optic–Capsule Distance. A positive interspace between the posterior optic surface and lens capsule occurred in 4 eyes (8%) in the CBR group and 5 eyes (10%) in the no-CBR group.

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B Figure 5. A: Number of quadrants affected by PCO at the last follow-up in patients attending follow-up at 1 year, 2 years, and/ or 3 years. B: Number of quadrants affected in patients with complete follow-up through years 1 to 3 (CBR Z capsular bending ring; rPCO Z regeneratory PCO).

Differences in Anterior Capsule Fibrosis and Capsulorhexis Contraction The differences in fibrotic whitening mirrored the difference in the area of contact between the anterior capsule and optic surface. In the no-CBR group, whitening encompassed the entire area of capsule–optic overlap; however, in the CBR group, it was essentially limited to the capsulorhexis margin. The capsulorhexis diameter was larger in the CBR group than in the no-CBR group 1 week after surgery (6.26 mm versus 5.94 mm) (P Z .006) and 1 year after surgery (6.1 mm versus 5.63 mm) (P Z .0002). Significantly less capsulorhexis contraction occurred in the CBR group than in the no-CBR group at 1 year (Figure 8). The mean intraindividual difference between the capsulorhexis diameter in the CBR group and the no-CBR group increased from 0.3 mm at 1 week to 0.5 mm at 1 year (P Z .07).

Figure 6. A: The CBR eyelets are firmly attached (left) and at a distance to each other (right) depending on capsular bag size and amount of fibrotic shrinkage. Note appropriate fixation of loop in angle between CBR and anterior capsule (arrow). B: Capsule bending ring eyelet distances at 1 week and 1 year.

Differences in Axial Optic Position The mean anterior chamber depth (ACD) measured with laser interferometry was 0.2 mm greater in the CBR group than in the no-CBR group. The difference was statistically significant at 1 week and 1 month. The mean ACD did not change in the CBR group; the chamber slightly flattened in the no-CBR group. The ACD and change in ACD are shown in Figure 9. Intraocular Pressure Postoperatively, intraocular pressure decreased by approximately 4 mm Hg in both groups but did not change thereafter. There was no statistically significant difference at any time between the 2 groups.

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Figure 7. The BCVA 1, 2, and 3 years postoperatively (CBR Z capsular bending ring; BCVA Z best corrected visual acuity).

Figure 8. Fibrotic contraction of anterior capsulorhexis (CBR Z capsular bending ring).

Pupil Diameter

randomized intraindividual comparison trial and reports more detailed results, including fibrotic changes, at 1, 2, and 3 years. In the CBR group, fibrosis of the anterior capsule leaf was only observed when a capsulorhexis opening smaller than the optic and a bulky high-diopter IOL allowed contact between the capsulorhexis rim and the optic surface. In contrast, the no-CBR group had extensive contact-mediated fibrosis of the anterior capsule leaf. The posterior capsule was completely extended by the CBR, while traction folds between the loop ends of the IOL were observed in almost one half of eyes without such a CBR. Although significantly reduced, the CBR did not completely prevent centripetal migration of equatorial LECs. This could be related to 2 factors. First, maximum sharpness of the edges is a key factor for the

At all examinations except preoperatively, there was a statistically significant difference between groups in pupil diameter under full medical dilation (tropicamide 1%, phenylephrine 10%). The mean diameter was 6.1 mm in the CBR group and 6.6 mm in the no-CBR group (Figure 10). DISCUSSION Capsular bending ring implantation led to a significant reduction in regeneratory PCO that persisted through 3 years. The BCVA in the CBR group was better than in the no-CBR group throughout the entire follow-up, although the difference decreased over time and lost statistical significance at 3 years. Because all eyes, including those that had an Nd:YAG laser capsulotomy, were considered, the no-CBR group progressively profited from the cumulative dropout of eyes necessitating Nd:YAG laser capsulotomy. Therefore, the positive impact on BCVA is increasingly underscored for methodological reasons. The safety and efficacy of the type 14-E CBR implantation in terms of PCO prevention over 2 years was shown in an earlier nonrandomized interindividual comparison study.10 The present study is a prospective

Figure 9. Left: The ACD. Right: Change in ACD measured by laser interferometry (CBR Z capsular bending ring; Control Z no-CBR group).

Figure 10. Pupil diameter under full medical dilation (CBR Z capsular bending ring).

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Figure 11. A: Potential fencing-in of equatorial LECs (gray rectangles on posterior capsule inside CBR) is depicted in right half of drawings. With a posterior–convex optic, migrating LECs may access space between the peripheral optic and posterior capsule (top). With tilt due to asymmetric haptic positioning, LECs may advance more centrally (middle). With a convex–plano optic and appropriate haptics, tight apposition of optic and posterior capsule precludes LEC access (no space–no cells). B: Example of retro-optical LEC ingrowth and pearl formation behind tilted optic due to asymmetrical fixation of IOL loops.

barrier function of implants.11 The edges of a PMMA CBR are not fully sharpened but rather are somewhat blunted due to the minimal tumble polishing required to prevent capsule damage when the CBR is implanted (Figure 1, A, inset). The barrier effect, be it by contact inhibition induced by capsular bending12,13 or the mechanical edge pressure exerted on the capsule,14,15 will thereby be reduced. Second, the regeneratory potential emerges from LECs in and adjacent to the lens equator. Theoretically, a CBR may not completely fence out all equatorial cells. If so, some of these cells may end up inside the posterior and inner edge of the ring (Figure 11, A, right top and right middle). In such cases, although delayed because of the small number of LECs fenced in, pearls may eventually form in the patent capsular bag fornix. However, in a recent study using the same surgical technique but an injectionmolded silicone CBR with fully retained sharp edges, regeneratory PCO was completely absent (W. Buehl

MD, et al., ‘‘Effect of Two Different Ring Haptic Silicone IOL Designs on Posterior Capsule Opacification,’’ presented at the XXVth Congress of the European Society of Cataract & Refractive Surgeons, Stockholm, Sweden, September 2007. Abstract available at: http://www.escrs.org/EVENTS/07Stockholm/sessiondetails.asp?idZ1615&categoryZFree&sessiondateZ9/9/2007. Accessed May 15, 2008). This indicates that blunting of the CBR edges, even though kept at a minimum, may be the decisive factor in the barrier failures observed with the PMMA ring. By itself, the lack of capsule fusion significantly changes the biological environment and thus LEC behavior. Therefore, in addition to capsule bending, the inhibitory effect of a CBR against LEC migration and proliferation may be attributed to other mechanisms including cell blocking and cell attracting. When the CBR barrier effect was incomplete, LEC migration was also observed beneath the optic

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Figure 12. A: With the eyelets at a distance in a CBR that is too large, a gateway is opened, allowing equatorial LECs to invade the posterior capsule. B: Example of eyelet gaping leading to sectoral LEC invasion (arrow).

periphery. This migration is allowed by the interspace between the extended posterior lens capsule and the posteriorly convex posterior surface of the biconvex optic of the IOL used in this study (Figure 11, A, top). The width and central extension of this space depend on the convexity of the posterior optic surface, which usually increases with increasing IOL diopter power, and the amount of optic tilt that results when the 2 IOL loops position asymmetrically in the angle between the CBR and the anterior or posterior capsule (Figure 11, A, middle; Figure 11, B; and Figure 6, A, arrows). When the interspace between the peripheral optic and capsule is wide enough, the invading equatorial LECs will form pearls. Within the visual axis, however, vision-disturbing opacities will never form because the optic is always firmly attached against the central posterior capsule.

In some eyes, the capsular bag was too small to fully accommodate the CBR, which resulted in overlapping of the eyelets at the CBR ends. In other eyes, a positive distance was found between the CBR ends. The interindividual variability of eyelet distances at 1 week is explained by the well-known differences in capsular bag diameter,16 while the decrease in distances at 1 year results from fibrotic capsular bag contraction (Figure 6, A). The varying capsular bag contraction has been described and quantified for standard capsular tension rings (CTRs).17 No complications ensued. However, close apposition of both eyelets is desirable to ensure circumferential capsule bending. Otherwise, the capsular bend will be discontinued and a gateway left open for equatorial LEC migration (Figure 12).

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The reason for the larger pupil size in the CBR group is unclear. No signs of increased anterior chamber flare were noticed biomicroscopically. Permanent distension of the capsular bag equator is a possible explanation. The latter is evidenced by the larger anterior capsulorhexis diameter in the CBR group. Following are ways the performance of the CBR can be optimized: 1. Surgical technique. The capsulorhexis should be as large as possible. This makes CBR insertion easier and reduces stress on the capsule and zonules. Bimanual implantation without the use of an injector is preferred. A tangential angle of insertion exerts less zonular stress and capsule entanglement. Optic tilting due to asymmetric fixation with consecutive unilateral widening of the peripheral posterior capsule–optic interspace may be avoided by ensuring symmetric haptic positioning within the angle between the anterior capsule and the CBR at the conclusion of surgery (Figure 11, A, top). 2. Design. The CBR should provide for full circumferential capsular bending independent of varying capsular bag diameter. Closed capsule rings exclude gaping of the ends. A composite closed CTR made from PMMA and acrylic segments has been described.18 However, closed rings cannot fully adapt to any given capsular bag diameter, which can vary significantly (eg, 10.8 G 1.42 mm19 and 10.32 G 0.42 mm20). Within a too large capsular bag, the bending effect may be inefficient. Within a too small capsular bag, vaulting of a closed ring cannot be excluded and a YAG laser capsulotomy might extend due to elastic stretching. Therefore, a modified open CBR (type 1F, Morcher) was designed with only 1 eyelet on the leading end, which has a tip curved like a ski (Figure 13, A, B). The schematic of the ring is shown in Figure 13, A. After insertion, the eyelet is visualized by slightly distending the pupil with a Y-spatula and is then grasped and pulled centrally with a lens hook. When released, the leading end of the CBR settles on and attaches from inside to the eyelet-free trailing end (Figure 13, B, left). The trailing end has a hole that accommodates the bent plunger tip of a special injector (Figure 13, B, right). In addition, the sharpness of the ring edges was enhanced. Encasing a PMMA core with silicone in a mold may be a practical solution, allowing for an open-loop design similar to that of the Morcher 1-F type that adapts to varying capsular bag diameters and has very sharp edges. Further potential improvements concern the design of the IOL to be used with a CBR. Using IOLs with an anterior-convex posterior-plano optic and anteriorly

Figure 13. A: Schematic of the modified CBR type 14F designed by Nishi and Menapace. B: The CBR 14F has a tail without an eyelet, allowing it to accommodate any given capsular bag diameter (left). A small bore permits injector implantation (right).

angulated loops with permanent memory should prevent peripheral retro-optical interspacing and consequent pearl ingrowth. Using loops with a square or rectangular cross-section and with a progressively increasing height toward the periphery or a paddle at the end should prevent asymmetric haptic fixation and thus optic tilting and would also avoid the potential for the IOL loop to cross under the CBR, which may interfere with capsular bending at the posterior CBR edge. Choosing a high-refractive optic material would further decrease the incidence of contact between optic and anterior capsule leaf or capsulorhexis edge and thus further reduce fibrotic whitening and shrinkage. In conclusion, implantation of the CBR was safe and effective over a 3-year follow-up. Other than the creation of a primary posterior capsulorhexis, implantation of a CBR is not an additive, but much more so an alternative approach to the sharp-edged optic because keeping the capsular bag from collapsing inherently obviates capsular bending at the optic rim. As the concept is largely independent of the optic edge design, the latter can be rounded to minimize edge glare and dysphotopsia.6 In the more recent study by Buehl et al. cited above, the efficacy of a CBR made from silicone with an integrated IOL optic was investigated. A similar concept

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CAPSULAR BENDING RING IMPLANTATION TO PREVENT PCO

was evaluated earlier in animal eyes by Hara et al.7,21 A silicone CBR can be manufactured with very sharp edges but must form a closed circle to resist capsule contraction. This implies it would not be able to adapt to variable capsular bag diameters and that the ring may deform and bend inward in an oversized or shrinking capsular bag. In the Buehl et al. study after 4 years, no eye with an adequately sized CBR developed regeneratory PCO. Similarly favorable results with a closed silicone ring were recently published by Hara et al.22 This indicates that implanting a sharp-edged CBR has the potential of fully preventing PCO formation and anterior capsule fibrosis. Efforts must be made to manufacture a CBR that has both very sharp edges and an open-ring design.

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REFERENCES 1. Sacu S, Menapace R, Findl O, Kiss B, Buehl W, Georgopoulos M. Long-term efficacy of adding a sharp posterior 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 2. 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 3. 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 4. Buehl W, Menapace R, Findl O, Neumayer T, Bolz M, Prinz A. Long-term effect of optic edge design in a silicone intraocular lens on posterior capsule opacification. Am J Ophthalmol 2007; 143:913–919 5. Menapace R. Prevention of posterior capsule opacification. In: Kohnen T, Koch DD, eds, Cataract and Refractive Surgery. (Essentials in Ophthalmology). Berlin, Germany; New York, NY, Springer; 101–122 6. Olson RJ. Consultation section: cataract surgical problems. J Cataract Refract Surg 2005; 31:653–654 7. Hara T, Hara T, Yamada Y. Equator ring’’ for maintenance of the completely circular contour of the capsular bag equator after cataract removal. Ophthalmic Surg 1991; 22:358–359 8. Barman SA, Hollick EJ, Boyce JF, Spalton DJ, Uyyanonvara B, Sanguinetti G, Meacock W. Quantification of posterior capsular opacification in digital images after cataract surgery. Invest Ophthalmol Vis Sci 2000; 41:3882–3892. Available at: http:// www.iovs.org/cgi/reprint/41/12/3882. Accessed May 15, 2008 9. Findl O, Buehl W, Menapace R, Georgopoulos M, Rainer G, Siegl H, Kaider A, Pinz A. Comparison of 4 methods for

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First author: Rupert Menapace, MD Department of Ophthalmology, Medical University of Vienna, Vienna, Austria