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Posterior Capsule Opacification After Phacoemulsification:Annual Review

Abhay R. Vasavada, MS, FRCS (England) and Mamidipudi R. Praveen, DOMS

Purpose: The purpose of this article is to provide a clinical update onposterior capsule opacification (PCO) after phacoemulsification by

reviewing the literature from the last 12 months.

Design: This article is a literature review.Methods: The authors conducted a 1-year literature search in theEnglish language on PCO using PubMed. The period used to conduct

the literature search was from January 1, 2013, to January 1, 2014. The

following search terms were used during the PubMed search: phacoemul-

sification, microcoaxial incision, posterior capsule opacification, long-term

evaluation of intraocular lens (IOL) implantation, IOL edge design and

material, surgical technique, anterior capsule overlap on the IOL optic,diabetes mellitus, myopia, pseudoexfoliation, retinitis pigmentosa, uveitis,

and neodymium: yttrium-aluminum-garnet laser capsulotomy.

Results: This review incorporates original articles that provided freshinsights and updates on PCO. Particular attention was paid to observa-

tional, randomized, controlled clinical trials, as well as analyses of larger

cohorts with a prospective and retrospective study design. Letters to the

editor, unpublished works, experimental trials and abstracts were not

considered.

Conclusions: This annual review provides a brief update on PCOthat might be of interest to the practicing clinical ophthalmologist.

Key Words: phacoemulsification, posterior capsule opacification,

intraocular lens, neodymium:yttrium-aluminum-garnet laser

capsulotomy

(Asia Pac J Ophthalmol2014;3: 235Y240)

Cataract is the leading cause of blindness worldwide, despitethe availability of effective cataract surgery.1,2 In the de-veloped world, cataract treatment and rehabilitation are man-aged satisfactorily, but in developing countries, up to 20 millionindividuals are waiting to undergo cataract surgery and 14,000new patients are added to the list every day.3,4 Manual small-incision cataract surgery and phacoemulsification are the mostfrequently performed surgical procedures in the developedcountries. They provide quick restoration of vision. However,they can lead to complications such as the development ofsecondary cataract, which is also known as posterior capsularopacification (PCO).5Y11 This is a major medical problemimpacting the patients well-being because it can lead to de-creased visual acuity. In spite of improvements in basic researchon the development of cataract, surgical techniques, as well asthe material or the design of the intraocular lens (IOL), the in-cidence of PCO is still 8% to 34.3% in adults and nearly 100%

in children.12Y17 Decreased visual acuity induced by PCO isreported to occur in 20% to 40% of patients 2 to 5 years aftersurgery.8,18 The most common and indeed successful method oftreatment of PCO is to photodisrupt a section of the posteriorcapsule using a high-energy Nd:YAG laser to create a clearregion around the visual axis.19 This treatment is expensive,costing the US Medicare program millions of dollars. It can alsolead to a host of medical complications such as an increase inintraocular pressure, retinal detachment, cystoid macular ede-ma, and, in the extreme cases, pitting of the surface and fractureof the intraocular lens adjacent to the cleared region.20Y22 Thetechnology to perform YAG laser capsulotomy is frequentlyunavailable in underdeveloped countries, adding considerablyto the problems of eradicating cataract-induced blindness inthese countries. The clinical and economic significance of PCOmakes it an important public health problem. In order to preventit, a clear understanding of the pathogenesis is needed.23,24

Posterior capsular opacification is a wound-healing responseof the residual equatorial lens epithelial cells (LECs), which areinevitably left in the bag and then undergo proliferation, migration,and metaplasia. These residual LECs can be clinically differen-tiated into 2 types: fibrotic and regeneratory LECs. Transdiffer-entiation of residual LECs into myofibroblasts causes fibroticPCO. Migration of LECs into the space between the capsule andthe IOL with subsequent proliferation causes regeneratory PCO.Clinically, the anterior LECs surrounding the rhexis express al-

pha smooth muscle actin and become myofibroblasts. The equa-torial cells form Elschnigs pearls. However, a biologicalunderstanding of the reason for this is lacking. Both fibrotic PCOand regeneratory PCO can lead to visual loss once the visual axishas been involved.

This review incorporates only a selected number of articlesinvolving clinical trials in the English-language literature. Allarticles included in this review were listed in PubMed betweenJanuary 2013 and January 2014, including large retrospectiveand prospective, comparative, observational, and randomizedtrials on IOLs, surgical techniques, and ocular diseases after

phacoemulsification. Only clinically relevant, novel, and poten-tially important and original research has been included. Thegoal is to provide a comprehensive and in-depth assessment offindings in the field of PCO.

Posterior Capsule Opacification With CoexistingOcular Disease

There is a noticeable decline in the occurrence of PCO dueto improved surgical techniques and IOL technology. Despitethese improvements, the development of PCO in patients un-dergoing cataract surgery is influenced by the presence ofsystemic conditions such as diabetes, pseudoexfoliation(PEX), uveitis, and retinitis pigmentosa (RP).

Posterior Capsule Opacification

and Pseudoexfoliationstern et al25 carried out a long-term evaluation of patients

for the development of PCO. Patients with and without PEX

ANNUALREVIEW

Asia-Pacific Journal of Ophthalmology & Volume 3, Number 4, July/August 2014 www.apjo.org 235

From the Iladevi Cataract and IOL Research Center, Raghudeep Eye Clinic,Ahmedabad, India.

Received for publication March 25, 2014; accepted July 2, 2014.Reprints: Abhay R. Vasavada, MS, FRCS, Iladevi Cataract and IOL

Research Center, Raghudeep Eye Clinic, Gurukul Rd, Memnagar,

Ahmedabad 380052, India. E-mail: [email protected]* 2014 by Asia Pacific Academy of OphthalmologyISSN: 2162-0989DOI: 10.1097/APO.0000000000000080

Copyright 2014 Asia Pacific Academy of Ophthalmology. Unauthorized reproduction of this article is prohibited.
mailto:[email protected]:[email protected]


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were evaluated using retrospective records of patients with PEX,who had undergone cataract surgery between June 2001 andDecember 2002. The authors compared 44 patients with PEXto 86 patients without PEX to assess the development of PCO6 to 7 years after phacoemulsification. A standardized surgical

procedure was implemented. The images were analyzed using

a software program (POCOman) to determine the extent andseverity of PCO. Using the guidelines available for POCOman,PCO was defined as any formation of pearls or fibrous opacifica-tion, visible on the retroilluminated JPEG-formatted images.

When the analyses were based on the (estimated) edge ofthe IOL and capsulorhexis, there were statistically significantdifferences between the 2 groups concerning severity and per-centage of PCO (Mann-Whitney Utest,P= 0.01 andP= 0.02).There was a lower level of PCO in eyes with PEX. Percentageand severity of PCO within the central 4.0- and 1.3-mm opticalzones were compared between the 2 groups. The results werenot statistically significant. An additional multivariate linearregression analysis was conducted. The percentage and seve-rity of PCO was not statistically significant in both groups.

Neodymium:yttrium-aluminum-garnet capsulotomy was per-formed in 16% (n = 7) of eyes in both groups (chi-square test,P= 0.96). In eyes with PEX undergoing phacoemulsification,there was a reduced risk for incurring an inflammatory re-sponse. The authors assumed that since the initial inflamma-tory response was minimal, it acted as a weaker stimulus forthe development of PCO in eyes with PEX.

This study employed a semiobjective method to assess thelong-term development of PCO in eyes with PEX. Although PEXis associated with a varied spectrum of complications, Ostern et al

provided objective evidence of a decreased incidence of PCOafter cataract surgery. Importantly, they implemented standardizedsurgical techniques for in-the-bag AcrySof IOL fixation and

postoperative medication. This standardization helped objec-

tively evaluate whether the patients with PEX ran the risk ofdeveloping PCO. In conclusion, this study showed that at theend of 6 years, the presence of PEX did not increase the risk ofPCO development when compared with patients without PEX.Patients with PEX did not need PCO treatment more frequentlythan patients without PEX.

Posterior Capsule Opacification andRetinitis Pigmentosa

Dikopf et al,26 in their retrospective observational caseseries, evaluated surgical outcomes in patients with RP undergo-ing phacoemulsification. Generally, it is difficult to predict visualoutcomes when both lenticular and retinal pathologies coexist.There is also a high risk for postoperative complications while

performing surgery on patients with RP. One of these complica-tions is PCO.

In this study, the authors reviewed cataract extraction in alarge group of patients with RP. Special attention was drawn tothe outcomes and complications of surgical intervention. Be-tween 2002 and 2012, 80 eyes of 47 consecutive patients withRP underwent phacoemulsification with IOL implantation.Postoperative records were analyzed for incidence of PCO,

ND:YAG capsulotomy, and surgical complications. The meanfollow-up time was 23.3 months. Sixty-six (82.5%) eyes de-veloped some level of PCO and 42 (52.5%) eyes required aYAG posterior capsulotomy at an average of 10.8 months aftersurgery. Fifteen patients had less than 3 months of follow-up. AKaplan-Meier survival curve was created to better describe the

development of significant PCO and the need for a YAGcapsulotomy. There was a high occurrence of YAG capsulotomyin RP patients with RP after cataract extraction. A majority of the

patients required YAG capsulotomy within a year after surgery.An increased rate of PCO is quite normal in any population ofyoung patients undergoing cataract extraction. However, PCOcan be exacerbated by known disruptions of the blood-ocular

barrier in patients with RP, allowing for high aqueous levels ofinterleukin 1 to accumulate after surgery.

There were high PCO rates in patients with RP due tozonular laxity. It allowed posterior capsule wrinkling proir tocapsular phimosis, providing an effective network for migrationof lens epithelial cells (LEC). Aggressive capsule polishing bysimple or ultrasound aspiration, osmolysis, or even usage of acapsular tension ring was often suboptimal in preventing PCO in

patients with RP. One of the strengths of this study is the use of alarge sample of patients with RPoperated on by a single surgeon.However, the study has its limitations. The most significantlimitation is the use of a retrospective design. Another limitationis the use of both eyes although the use of a single eye of each

patient would have been scientifically more valid. The rates ofPCO and YAG capsulotomy (82.5% and 52.2%, respectively)confirm this known complication of cataract surgery in patients

with RP.

Posterior Capsule Opacification and High Myopia

Zhao et al27 attempted to understand the mechanisms af-fecting the development of PCO in highly myopic eyes by usingultra-long scan depth optical coherence tomography (UL-OCT).They compared highly myopic eyes with emmetropic eyesfor capsule-IOL interactions, including anterior and posteriorcapsule adhesion and configuration of the capsular bend. Vari-ous configurations of capsular bend with the IOL were observedat the last follow-up. They were classified into complete andincomplete capsular bends. Three different types of completecapsular bends by UL-OCT were described postoperatively. Thefirst was anterior adhesion in which the anterior posterior cap-

sule was attached to the anterior side of the optic. The second wasmiddle adhesion in which the anterior posterior capsule was at-tached to the middle of the optic, and the third was posterioradhesion in which the anterior posterior capsule was attached tothe posterior side of the optic. Three different types of incom-

plete capsular bends by UL-OCT were also described postoper-atively. The first was funnel adhesion in which the anterior

posterior capsule was attached to the middle of the optic at adistance from the IOL. The second was parallel adhesion, inwhich the anterior posterior capsule did not attach completely.Finally, the third was furcate adhesion in which the anterior

posterior capsule was separated peripherally although the cap-sular bend was formed at the edge of the IOL.

This prospective study included 40 eyes of 40 patients with

cataract scheduled for phacoemulsification with a single-pieceAcrySof IOL implantation (Alcon Laboratories, Inc, Fort Worth,TX, USA). Among the 40 eyes, 20 were highly myopic (axial length926 mm; high myopia group) and the other 20 were emmetropicwith a normal axial length (22 mm G axial length G 24.5 mm; em-metropia group). Three types of capsular bends with completeadhesion were found in highly myopic eyes. Anterior adhesionwas observed in most cases (70%). In highly myopic eyes, 4capsular bends were observed with middle adhesion, while only1 nasal capsular bend was found with posterior adhesion. Threetypes of capsular bends with incomplete adhesion were foundat the last follow-up in highly myopic eyes. Six capsular bends

presented funnel adhesion, 8 capsular bends presented paralleladhesion, and 1 capsular bend showed furcate adhesion. Three

types of capsular bends with complete adhesion were found inhighly myopic eyes. Anterior adhesion was observed in mostcases (70%). In highly myopic eyes, 4 capsular bends were

Vasavada et al Asia-Pacific Journal of Ophthalmology & Volume 3, Number 4, July/August 2014

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observed with middle adhesion, whereas only 1 nasal capsularbend was found with posterior adhesion. Three types of capsularbends with incomplete adhesion were found at the last follow-upin highly myopic eyes. Six capsular bends presented funnel ad-hesion, 8 capsular bends presented parallel adhesion, and 1capsular bend showed furcate adhesion. There was significantly

less apposition of the posterior capsule against the IOL inhighly myopic eyes when compared to emmetropic eyes. Pos-terior capsular adhesions were delayed in highly myopic eyesduring the follow-up. At the 28-day follow-up, slight PCO wasfound in 5 highly myopic eyes because the posterior capsule didnot adhere completely to the IOL. The rate of posterior cap-sule adhesion in eyes with a high degree of axial myopiawas significantly lower than that observed in emmetropic eyes.The authors speculated possible reasons for this. The IOLs wereimplanted in relatively large capsular bags in the high myopiagroup. The capsular bag diameter correlated positively with theaxial length, while IOL thickness correlated with IOL power.Secondly, a lower IOL power resulted in reduced posterior con-vexity. A large-sized posterior capsule with steep convexity could

affect posterior capsular adhesion to the IOL. These two factorsmay have weakened the ability of the capsule to stretch after IOLinsertion in highly myopic eyes. A noteworthy observation wasthat the types of capsular bend were more heterogeneous in thehigh myopia group and displayed incomplete apposition whencompared to the emmetropia group.

This was a prospective study exploring the dynamics ofPCO development in highly myopic eyes. The study objectivelydocumented the apposition of the posterior capsule to the IOLusing a custom-built, UL-OCT device. The development of PCOcould have been attributed to the incomplete formation of cap-sular bends in highly myopic eyes during the early postoperative

period, coupled with weak adhesion between the posterior cap-sule and the IOL. Capsular bend formation has long been con-

sidered crucial for PCO prevention. The authors furtherspeculated that highly myopic eyes with incomplete capsular

bend could have facilitated LEC migration. Delayed or incom-plete capsule-IOL interaction is believed to increase LEC prolif-eration and migration due to weak adhesion. There are potentiallimitations to this study. First, the authors evaluated the procedurefor only 28 days postoperatively. Secondly, the sample size wastoo small. Thirdly, even though the authors observed the capsule-IOL interaction spatially, it was not possible to calculate thespace due to the technical limitations of OCT.

Posterior Capsule Opacification With AlternateSurgical Techniques

Trypan Blue Injection and PosteriorCapsule Opacification

Today, the focus of combating PCO is on the lysis of LECs.In a prospective, randomized, clinical trial of patients under-going phacoemulsification with foldable IOL implantation,Sharma et al coauthors studied the effect of injecting 0.1%trypan blue into the capsular bag on the development ofPCO.28 Eyes were randomized into 2 groups, the trypan bluegroup or the control group. The trypan blue group received0.2 mL of 0.1% trypan blue (Visiblue; Shah & Shah) injectedsubcapsularly at 2 sites that were 180 degrees apart after cortical-cleaving hydrodissection. The control group received 0.2 mLof a balanced salt solution injected in a similar fashion and asecond injection of balanced salt solution after cortical-cleaving

hydrodissection so that the total quantity of fluid in the bag wasthe same in both groups. A single surgeon performed all surgeriesusing topical anesthesia and a standardized surgical technique.

A foldable hydrophilic acrylic square-edged IOL (CT ASPHINA603P; Carl Zeiss Meditec) was implanted with a wound-assisteddelivery. An anterior segment photograph under full mydriasiswas taken at 6 and 12 months. Posterior capsular opacificationgrading was done. The PCO score was significantly lower inthe trypan blue group when compared to the control group at

6 and 12 months.This study demonstrated the role played by trypan blue in

inhibiting PCO. However, a major limitation is the small samplesize used. Another limitation is that PCO had been evaluated forover 1 year instead of the customary 3-year duration. A studywith a larger sample size carried out over a longer duration iswarranted to conclusively ascertain the long-term effects oftrypan blue on PCO formation.

Phacovitrectomy and PosteriorCapsule Opacification

Iwase et al29 evaluated PCO development in eyes with idio-pathic epiretinal membranes (ERMs) undergoing 20-gauge pha-

covitrectomy (n = 20 eyes), 23-gauge phacovitrectomy (n = 20eyes), and phacoemulsification alone (n = 50 eyes). The durationof follow-up was 24 months. After administration of retrobulbarand peribulbar anesthesia, a half-round fornix-based conjunc-tival incision was created in the 20-gauge phacovitrectomygroup. A 3-mm self-sealing sclerocorneal tunnel was created at12 oclock in eyes in all the groups. A standardized surgicaltechnique of phacoemulsification was implemented. The woundwas not enlarged and the SA60AT IOLs were inserted in thecapsular bag. Sutures were not used to close the sclerocornealtunnel incision. After making 3 scleral ports in the 23-gauge

phacovitrectomy group, vitrectomy and ERM peeling withoutstaining were performed. Each sclerotomy was then closed witha 7.0 suture in the 20-gauge phacovitrectomy group. Finally, the

conjunctival wound was sutured in the 20-gauge phacovitrec-tomy group. Suturing was not required in the 23-gauge phaco-vitrectomy group. The PCO density value was measured usingScheimpflug video photography (EAS-1000; NIDEK, Gamagori,Japan) at 1 week, 1 month, 3, 6, 12, 18, and 24 months after surgery.

The PCO value of the 20-gauge phacovitrectomy groupwas significantly higher than that of the 23-gauge phacovitrec-tomy group at 6, 12, 18, and 24 months after surgery. Similarly,the PCO value in the 23-gauge phacovitrectomy group was signif-icantly higher than that of the cataract surgery group at 24 monthsafter surgery. The same IOL, SA60AT, was implanted in all thecases, indicating that the surgical procedure was the only dif-ference among the groups. In this report, similar procedureswere performed for each ERM case, namely, cataract surgery,

core vitrectomy, and ERM peeling. The reduced incidence ofPCO could be attributed to the small size of the vitrectomy in-struments used, which lowered postoperative intraocular in-flammation. As vitrectomy was less traumatic, the procedure didnot seem to cause strong inflammation. There were no significantdifferences in postoperative intraocular inflammation between the23-gauge phacovitrectomy and the cataract surgery groups. De-spite this, there was an incidence of PCO in the 23-gauge

phacovitrectomy group.To the best of our knowledge, this is the first report quantifying

PCO in phacovitrectomy using non-qualitative methods (EAS-1000, Scheimpflug camera). As selection bias had been mini-mized, the differences between the characteristics of patientsand the kinds of retinal diseases could not affect the resultant

outcomes. Minimization of selection bias is crucial to any studyof this kind. There are many variables that can be associatedwith PCO development such as the occurrence of intraoperative

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and/or postoperative complications, usage of long-acting gastamponade, and postoperative posturing. We speculate that the

posterior pressure in eyes without a vitreous may have preventedcapsular bend formation that requires a sharp optic edge and

posterior pressure. It is, therefore, possible that the IOL edge has aminimal effect in reducing PCO in phacovitrectomy. In addition, a

high level of postoperative inflammation may probably lead toLEC migration and extensive PCO in eyes undergoing phaco-vitrectomy. As this study included only cases with ERMs, theseresults may only apply to similar cases that have not undergoneadditional procedures, such as laser photocoagulation or gas tam-

ponade. Further studies are warranted to examine the developmentof PCO between patients undergoing 25-gauge phacovitrectomyand cataract surgery.

Intraocular Lens and PosteriorCapsule Opacification

Posterior Capsule Opacification With the iMics1NY-60 and AcrySof SN60WF: 3-Year Results of a

Randomized TrialLeydolt et al30 conducted a prospective, randomized, and

controlled study comparing PCO development between twohydrophobic acrylic single-piece, sharp-edged IOLs with afollow-up period of 3 years. One hundred patients (200 eyes)were included in this trial. Each patient randomly received aniMics1 NY-60 IOL (Hoya Corp, Tokyo, Japan) in 1 eye and anAcrySof SN60WF IOL (Alcon Laboratories, Inc, Fort Worth,TX) in the contralateral eye to allow for intraindividual com-

parison. A single surgeon performed the surgeries using a stan-dardized technique. Follow-up examinations were performed at 1week and 3 years after surgery. At each follow-up visit, the amountand type of regeneratory PCO were evaluated. Digital retroillumi-nation images of the posterior capsule were captured. Posterior

capsular opacification levels were analyzed using automatedimage analysis software (Automated Quantification of After-Cataract [AQUA]). At 3 years, the PCO score on a scale from0 to 10 was 3.0 T 2.0 in the iMics1 NY-60 group and 1.9 T 1.4in the AcrySof SN60WF group. The difference between the2 groups was statistically significant (P G 0.001). However,46 eyes (82%) in the iMics1 NY-60 group and 9 eyes (16%) in theAcrySof SN60WF group showed a high level of regeneratoryPCO. After the 3-year follow-up, the rates of Nd:YAG lasercapsulotomy in iMics1 NY-60 was significantly higher whencompared against the AcrySof SN60WF eyes (P G 0.001). Theresults demonstrated that 3 years after surgery, eyes with iMics1

NY-60 IOLs showed a statistically significantly higher PCO score(3.0 T 2.0) and Nd:YAG capsulotomy rate (35.6%) than those with

AcrySof SN60WF IOLs (PCO, 1.9 T 1.4; Nd:YAG, 13.7%). Theauthors did not observe a lower incidence of PCO in the eyeswith the iMics1 NY-60 IOL compared to the eyes with theAcrySof SN60WF IOL. On the contrary, the iMics1 NY-60 IOL

presented a statistically significant higher Nd:YAG capsulotomyrate (35.6%) 3 years after surgery. In conclusion, the presentstudy indicates statistically significant differences in the rateof PCO and Nd:YAG capsulotomy between 2 similarly designedsharp-edged, single-piece IOL models. These disparities can beattributed to differences in their material properties.

The results of this study have shown that IOL materialsplay an important role in PCO formation. The various hydro-phobic acrylic IOLs differ not only in the techniques used in theirmanufacture, but also in the postprocessing modifications of their

surface. It is evident that the properties of the materials used inIOLs impact biological responses such as capsular biocompati-

bility and LEC migration. An analysis of the surface of AcrySof

IOLs revealed a significantly higher magnitude of surface rough-ness or morphological changes. Another important factor is ad-hesion of the IOL surface to the capsular bag mediated byextracellular matrix proteins. Better adhesion is assumed to re-sult in less LEC growth between the IOL surface and the cap-sular bag, causing a lower level of PCO. In vitro studies have

shown that hydrophobic acrylic IOLs bind fibronectin to a sta-tistically significantly greater degree than other IOL materials.Thus, fibronectin seems to act as a biological glue with theseIOLs resulting in a lower level of PCO. A limitation of the presentstudy is that no additional follow-up visits scheduled between 1week and 3 years after surgery. An in-between follow-up visitwould have allowed a PCO value to be estimated for those eyesso as to demonstrate viability of laser capsulotomy at the 3-yearfollow-up.

Posterior Capsule Opacification With 3Intraocular Lenses: 12-year Prospective Study

Most PCO studies have a follow-up duration ranging from

1 to 3 years, and there are a few studies with a 5-year follow-up.There are very few data available in the literature on PCO de-velopment on a long-term basis.

This study was an extended follow-up of a randomizedtrial whose earlier outcomes at 2, 3, and 5 years have already

been reported. Rnbeck et al31 in this prospective study com-pared PCO formation after implantation of 3 IOL models12 years after surgery. Using a randomization protocol, thesurgeon implanted 1 of the following 3 IOLs: a heparin-surface-modified poly (methyl methacrylate) (HSM PMMA) IOL (809C;Pharmacia & Upjohn, Inc.), a foldable silicone IOL (SI-40NB,Allergan, Inc.), or a foldable hydrophobic acrylic IOL (AcrySofMA60BM; Alcon Laboratories, Inc.). At the follow-up exami-nations, 11.3 to 13.4 years postoperatively, POCOman system

was used to analyze PCO in retroillumination images of theposterior capsule. The percentage of PCO in the total area of theposterior capsule inside the capsulorhexis was the PCO fraction.The number of patients undergoing Nd:YAG capsulotomy dur-ing the extended follow-up period and the timing of this treat-ment after surgery were recorded. After 12 years, there was nosignificant difference in the fraction or severity of PCO betweenthe silicone and acrylic IOLs. The HSM PMMA IOL had asignificantly higher PCO fraction than the silicone IOL (P G0.05) but not higher that of the acrylic IOL. There was no dif-ference in the severity of PCO between the HSM PMMA IOLand the other 2 IOLs. The silicone IOL had a higher mediancapsulotomy-free survival (9150 months) than the acrylic IOL(108 months) and the HSM PMMA IOL (53 months). Survival

without Nd:YAG capsulotomy did not differ between the acrylicand the silicone IOLs or between the silicone and the HSMPMMA IOLs; however, overall survival was significantly betterwith the acrylic IOL than with the HSM PMMA IOL (PG 0.001).The PCO evaluation using the retroillumination photographsshowed that over time, the differences between the IOLs becameincreasingly lower. Regarding the overall survival without

Nd:YAG capsulotomy over the entire 12-year postoperative peri-od, the sharp-edged hydrophobic acrylic IOL and the round-edged silicone IOL seemed to induce less PCO than the round-edged HSM PMMA IOL. After approximately 6 to 7 years, thesurvival curve of the silicone IOL crossed that of the hydrophobicacrylic IOL. Subsequently, it had better survival without Nd:YAGcapsulotomy than the hydrophobic acrylic IOL despite its round

edge.The authors observed that these results were in line with

those in their 5-year follow-up study. They attributed the





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efficiency of the silicone IOL in inhibiting PCO in the long runto its material property. The adhesiveness of silicone tovitronectin and collagen type IV was significantly higher thanthe adhesiveness of acrylate to these proteins, 1 week after in-cubation. Silicone is believed to catalyze the process ofmyofibroblastic transdifferentiation and collagenous sealing of the

capsular leaves at the optic edge. This might have resulted inmore permanent sealing at the optic edge so that it could betterwithstand mechanical pressure from proliferating LECs. Inconclusion, after 12 years, there was no difference in PCO oroverall survival without capsulotomy between the acrylic and thesilicone IOLs. The HSM PMMA IOL had a significantly higherPCO fraction than the silicone IOL and a lower overall survivalthan the acrylic IOL.

The PCO inhibitory property of the 3 IOL groups with ashorter follow-up of 2 to 3 years does not apply after 12 years.The PCO scores were not significantly higher with the hydro-

phobic acrylic IOL than with the silicone IOL. The reduced orlost efficiency of the sharp edge of the hydrophobic acrylic IOLis believed to result from late proliferation of LECs leading to

an emerging Soemmerring ring in the peripheral capsular bag.This causes mechanical pressure, breaking the seal between thefused anterior and posterior capsule leaves. The capsular bendat the sharp posterior edge is reversed. This results in a delayed

barrier failure. The LECs can migrate behind the posterior op-tic. There was a slope in the Nd:YAG-free survival curve of thehydrophobic acrylic IOL at 4 to 5 years, indicating that theSoemmerring ring was present from approximately 4 yearsonward as it took weeks to months for the LECs to proliferateand migrate to the visual axis. The current study has a fewlimitations. Due to the lengthy duration of the study, many pa-tients were lost to follow-up. The 3 IOLs differed in material,design, and size. However, despite this, the results are interest-ing and worth reporting.

Posterior Capsule Opacification Between 2 AsphericMicroincision Intraocular Lenses

The use of microincision cataract surgery (MICS) has ne-cessitated the development of a generation of microincisionIOLs that can be implanted through subY2.0-mm incisions. It isimportant that these IOLs perform as well as IOLs designed forconventional incisions. Until recently, available microincisionIOLs did not match the standards of conventional IOLs.

Keeping these factors in view, Nanavaty et al32 designedthis study to evaluate differences in the incidence of PCO be-tween 2 aspheric microincision hydrophilic IOLs (Acri.Smart36A and Akreos MI-60) with a conventional single-piece hydro-

phobic acrylic spherical IOL (AcrySof SN60AT; Alcon Labora-tories, Inc.). All eyes underwent standardized phacoemulsificationfor bilateral cataract performed by a single surgeon. Thecapsulorhexis was fashioned to overlap the IOL optic edge by360 degrees. Either the Acri.Smart 36A (negatively asphericalIOL) or the Akreos MI-60 (aspherically neutral IOL) was injectedthrough a 2.4-mm temporal clear corneal incision in the firsteye. The AcrySof SN60AT IOL was implanted in the fellow eyewithin 3 weeks. All patients were examined postoperatively at 1,3, 6, 12, and 24 months. The digital retroillumination images ofeach of the eyes were analyzed to measure the percentage area ofPCO in the capsulorhexis area. The mean percentage PCO scorewas significantly less with the Acri.Smart 36A IOL when com-

pared with the Akreos MI-60 IOL at 1, 3, and 12 months (P=

0.03,P= 0.02, andP= 0.05, respectively). Further, there was asignificant difference in the percentage of PCO scores at 1 monthand 12 months among all 3 IOLs (P= 0.01 andP= 0.04). At

1 month, the AcrySof SN60AT IOL showed a higher level ofPCO, whereas at 12 months, the Akreos MI-60 IOL showed ahigher level of PCO. It increased linearly with time for theAcri.Smart 36A IOL and the Akreos MI-60 IOL, with a max-imum of up to 16% and 23%, respectively. Further, thecapsulotomy rate was 4.8% (2 out of 42 eyes) with the

Acri.Smart 36A IOL 24 months postoperatively. With theAkreos MI-60 IOL, the authors found a mean PCO scoreof 22.57% T 25.56% at 2 years and 8 eyes (19%) required Nd:YAG capsulotomy for a visually significant PCO. At 2 years,the mean PCO score was lower than 11% for the conventionalAcrySof IOL and 23% for the Akreos MI-60 IOL. With thehydrophilic acrylic microincision IOLs, PCO showed a trendtoward progression over the 2-year follow-up.

Hydrophilic acrylic material and the posterior optic edgedesign of the IOL influence PCO performance. The Acri.Smart36A IOL is a hydrophilic IOL with a hydrophobic surface andis used as a platform for toric, multifocal, and multifocal toricIOLs. It is likely that these variations will have a similar in-cidence of PCO. The Akreos MI-60 IOL has 4 haptics with a

10-degree angulation and a 360-degree square-edged design.These features are intended to prevent PCO. In the presentstudy, high rates of YAG capsulotomy with the Akreos MI-60IOL were found. This could have been due to the differencein material characteristics and design or the posterior opticedge profile. Sharpness of the square edges of the IOL varieswith different IOLs and is dependent on the manufacturing tech-niques. The absence of a square-edged barrier at the optic-haptic

junction of some IOLs may contribute to the migration of LECsthrough the optic-haptic junction. In summary, in this study, theauthors found that the Acri.Smart 36A IOL had better PCO per-formance than the Akreos MI-60 IOL. However, at the two-yearfollow-up, a conventional hydrophobic acrylic IOL had betterPCO performance than both microincision IOLs.

CONCLUSIONSAt present, PCO remains the most common complication

of modern cataract surgery. Posterior capsular opacification iscaused by residual LECs, which are inevitably left in the bagand undergo proliferation and metaplasia. PCO is believed to bemultifactorial and influenced by factors such as age or con-comitant intraocular or systemic diseases, surgical technique,and IOL design. There is considerable interest in the impact ofthe IOL on the development of PCO since the characteristics andthe designs of the IOLs play a crucial role in preventing PCO.Furthermore, differences in PCO performance between IOLs arelikely to reflect their distinction in biomaterials and designs.

Current strategies to prevent PCO focus on IOL design. Clinicalstudies have now clearly defined important parameters. Thesharpness or squareness of the edge profile is of paramountimportance. The square edge seems to prevent LEC migrationinto the central posterior capsule. It forms a pressure barrier as itis pushed against the posterior capsule, thereby increasing fi-

brosis of the bag in the first few weeks after surgery. This helpsprevent PCO no matter which type of IOL is used. Most sur-geons now aim to make the rhexis smaller than the IOL diameter.Another important design feature is that the square edge barriershould be of 360 degrees. A break in the barrier is the Achillesheel, where LECs can penetrate into the posterior capsulethrough the optic-haptic junction. The no space, no cell theoryis known as the main mechanism preventing PCO. Although the

cortex is completely removed, the LECs at the equator couldproliferate and migrate toward the posterior capsule when a po-tential space exists between the capsular bag and the IOL. It is

Asia-Pacific Journal of Ophthalmology & Volume 3, Number 4, July/August 2014 PCO Annual Review (January 2013-January 2014)

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generally believed that delayed or incomplete capsule-IOL in-teraction might increase LEC proliferation and migration due toweak adhesion. Two key factors should be considered: capsular

bend formation and posterior capsule apposition with the IOL.Early and rapid formation of the capsular bend could block LECmigration and proliferation. Tight adhesion between the poste-

rior capsular bag and the IOL could create a second defensivebarrier to inhibit LEC migration and proliferation. Many clinicalstudies have also shown that PCO rates seem to be higher withhydrophilic IOLs in comparison with hydrophobic IOL mate-rials. This is related to an intrinsic property of the hydrophilicmaterial. There is a large amount of experimental works ondestroying LECs at the time of surgery by drug delivery, surgicaltechnique, or physical LEC destruction, but none of these has

been applied in clinical practice lest there be of pharmacologicalbystander damage elsewhere in the eye or the risk of increasedsurgical complications, time or cost. Present research now fo-cuses on modulating LECs rather than destroying them. Last butnot least implantation of IOLs with improved designs and en-hanced surgical techniques have reduced the incidence of PCO.

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