Posterior capsule opacification after phacoemulsification: foldable acrylic versus poly(methyl methacrylate) intraocular lenses

Intraocular lens optic edge design for the prevention of posterior capsule opacification after cataract surgery

BACKGROUND

Posterior capsule opacification (PCO) is a clouding of the posterior part of the lens capsule, a skin-like transparent structure, which surrounds the crystalline lens in the human eye. PCO is the most common postoperative complication following modern cataract surgery with implantation of a posterior chamber intraocular lens (IOL). The main symptoms of PCO are a decrease in visual acuity, 'cloudy', blurred vision and reduced contrast sensitivity. PCO is treated with a neodymium:YAG (Nd:YAG) laser to create a small opening in the opaque capsule and regain a clear central visual axis. This capsulotomy might cause further ocular complications, such as raised intraocular pressure or swelling of the central retina (macular oedema). This procedure is also a significant financial burden for health care systems worldwide. In recent decades, there have been advances in the selection of IOL materials and optimisation of IOL designs to help prevent PCO formation after cataract surgery. These include changes to the side structures holding the lens in the centre of the lens capsule bag, called IOL haptics, and IOL optic edge designs.

OBJECTIVES

To compare the effects of different IOL optic edge designs on PCO after cataract surgery.

SEARCH METHODS

We searched CENTRAL, Ovid MEDLINE, Ovid Embase, Latin American and Caribbean Health Sciences Literature Database (LILACS), the ISRCTN registry, ClinicalTrials.gov and the World Health Organization (WHO) International Clinical Trials Registry Platform (ICTRP) up to 17 November 2020.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) that compared different types of IOL optic edge design. Our prespecified primary outcome was the proportion of eyes with Nd:YAG capsulotomy one year after surgery. Secondary outcomes included PCO score, best-corrected distance visual acuity (BCDVA) and quality of life score at one year. Due to availability of important long-term data, we also presented data at longer-term follow-up which is a post hoc change to our protocol.

DATA COLLECTION AND ANALYSIS

We used standard methods expected by Cochrane and the GRADE approach to assess the certainty of the evidence.

MAIN RESULTS

We included 10 studies (1065 people, 1834 eyes) that compared sharp- and round-edged IOLs. Eight of these studies were within-person studies whereby one eye received a sharp-edged IOL and the fellow eye a round-edged IOL. The IOL materials were acrylic (2 studies), silicone (4 studies), polymethyl methacrylate (PMMA, 3 studies) and different materials (1 study). The studies were conducted in Austria, Germany, India, Japan, Sweden and the UK. Five studies were at high risk of bias in at least one domain. We judged two studies to be at low risk of bias in all domains. There were few cases of Nd:YAG capsulotomy at one year (primary outcome): 1/371 in sharp-edged and 4/371 in round-edged groups. The effect estimate was in favour of sharp-edged IOLs but the confidence intervals were very wide and compatible with higher or lower chance of Nd:YAG capsulotomy in sharp-edged compared with round-edged lenses (Peto odds ratio (OR) 0.30, 95% CI 0.05 to 1.74; I² = 0%; 6 studies, 742 eyes). This corresponds to seven fewer cases of Nd:YAG capsulotomy per 1000 sharp-edged IOLs inserted compared with round-edged IOLs (95% CI 9 fewer to 7 more). We judged this as low-certainty evidence, downgrading for imprecision and risk of bias. A similar reduced risk of Nd:YAG capsulotomy in sharp-edge compared with round-edge IOLs was seen at two, three and five years but as the number of Nd:YAG capsulotomy events increased with longer follow-up this effect was more precisely measured at longer follow-up: two years, risk ratio (RR) 0.35 (0.16 to 0.80); 703 eyes (6 studies); 89 fewer cases per 1000; three years, RR 0.21 (0.11 to 0.41); 538 eyes (6 studies); 170 fewer cases per 1000; five years, RR 0.21 (0.10 to 0.45); 306 eyes (4 studies); 331 fewer cases per 1000. Data at 9 years and 12 years were only available from one study. All studies reported a PCO score. Four studies reported the AQUA (Automated Quantification of After-Cataract) score, four studies reported the EPCO (Evaluation of PCO) score and two studies reported another method of quantifying PCO. It was not possible to pool these data due to the way they were reported, but all studies consistently reported a statistically significant lower average PCO score (of the order of 0.5 to 3 units) with sharp-edged IOLs compared with round-edged IOLs. We judged this to be moderate-certainty evidence downgrading for risk of bias. The logMAR visual acuity score was lower (better) in eyes that received a sharp-edged IOL but the difference was small and likely to be clinically unimportant at one year (mean difference (MD) -0.06 logMAR, 95% CI -0.12 to 0; 2 studies, 153 eyes; low-certainty evidence). Similar effects were seen at longer follow-up periods but non-statistically significant data were less fully reported: two years MD -0.01 logMAR (-0.05 to 0.02); 2 studies, 311 eyes; three years MD -0.09 logMAR (-0.22 to 0.03); 2 studies, 117 eyes; data at five years only available from one study. None of the studies reported quality of life. Very low-certainty evidence on adverse events did not suggest any important differences between the groups.

AUTHORS' CONCLUSIONS

This review provides evidence that sharp-edged IOLs are likely to be associated with less PCO formation than round-edged IOLs, with less Nd:YAG capsulotomy. The effects on visual acuity were less certain. The impact of these lenses on quality of life has not been assessed and there are only very low-certainty comparative data on adverse events.

Quantification of Inflammation Following Nd:YAG Laser Capsulotomy and Assessing the Anti-inflammatory Effects of Nepafenac 0.1% and Betamethasone 0.1

Purpose: To quantify the intraocular inflammation, measured using laser flare photometry (LFP), after Nd:YAG capsulotomy and compare the effects of different topical anti-inflammatory regimes.Methods: A single-center, prospective, randomized controlled study, which included 90 eyes of 90 patients with visually significant posterior capsular opacification. In all patients, Nd:YAG capsulotomy was done and was then randomized into three groups: (A) Topical betamethasone 0.1%; (B) Topical nepafenac 0.1%; and (C) Control group: did not receive any anti-inflammatory agent post capsulotomy.Results: There was a significant increase in the mean LFP values 2 h following laser capsulotomy (p < 0.001) and then declined gradually and came back to pre-laser values by 2 weeks in all three groups. The mean LFP values, central macular thickness, and best corrected visual acuity were comparable among groups. None developed central macular edema.Conclusion: Intraocular inflammation following Nd:YAG capsulotomies is minimal and transient. Routine use of prophylactic anti-inflammatory agents may be avoided.

Biomaterial Influence on Intraocular Lens Performance: An Overview

There is strong evidence that the IOL material is the factor having the greatest impact on posterior capsule opacification (PCO), anterior capsule opacification (ACO) development, and glistening formation after cataract surgery, even though there are other IOL features—such as haptic material and design and edge and optic design—that also have some influence. We reviewed the published literature describing the adverse events that are mainly related to the intraocular lens (IOL) material, such as PCO, ACO, and the subsequent capsule contraction, as well as glistening formation. The adverse events presented in this overview are the most common ones in clinical practice, and therefore, they are generally included in the clinical protocols for IOL evaluation.

Refractive Lens Exchange Combined with Primary Posterior Vitrectorhexis in Highly Myopic Patients

Purpose. To evaluate efficacy and safety of primary vitrectorhexis for posterior capsulotomy in highly myopic patients undergoing refractive lens exchange. Methods. The study is a prospective nonrandomized interventional study. The study comprised 60 eyes of 60 myopic patients. All patients underwent refractive lens exchange (RLE) and foldable IOL implantation combined with primary posterior capsulotomy. We used a 23-gauge vitrectomy probe for the creation of the posterior capsule opening. We followed the patients for one year. Results. During surgery, the IOLs remained well centered in the capsular bag after creation of the capsulotomy. Postoperatively, we did not report any complications related to lens centration or changes in the posterior capsulotomy size. No eye required YAG laser posterior capsulotomy and no cases of retinal detachment (RD) occurred during the follow-up period. Conclusion. Primary posterior vitrectorhexis during RLE is an efficient method in preventing the occurrence of posterior capsular opacification (PCO) and the need for YAG laser posterior capsulotomy with its possible complications.

Posterior capsular opacification in diabetic and nondiabetic canine patients following cataract surgery

Posterior capsular opacification (PCO) is the most common postoperative complication of contemporary cataract surgery. Limited information is available regarding PCO formation and factors that influence PCO development in the dog. Two hundred sixty-five eyes (144 from diabetic dogs and 121 from dogs with breed-related cataracts) were prospectively evaluated for PCO formation for up to 12 months postoperatively. The mean age of all dogs in the study was 7.77 years and diabetic dogs were significantly older than dogs with breed-related cataracts. There were 73 males (61 neutered, 12 intact) and 74 females (70 neutered, 4 intact) in the study. Statistical analysis was performed based on age, breed/size, gender, stage of cataract at the time of surgery, PCO score at each time point, breed-related vs. diabetic cataract, right eyes compared to left eyes, and presence/absence of uveitis. Age and gender did not significantly influence PCO formation. Small and medium-sized breeds developed significantly more PCO in comparison to the large/giant breeds at 2 weeks and 2-4 months postoperatively, but the differences were not significant at later time points. There was an overall significant increase in PCO formation in eyes with early immature cataracts when compared to other stages of cataract up to 4 months postoperatively but not at later time points. There were no statistical differences in PCO score at 6 months or at 1 year postoperatively in eyes with breed-related and diabetic cataracts. Right eyes did not differ from left eyes in PCO score. PCO score significantly increased over time in breed-related and diabetic groups and in the overall population. No difference was found in the degree of PCO formation in eyes with inflammation prior to or after surgery compared with those without inflammation. In summary, age, gender, presence of inflammation, and cause of cataract (breed-related vs. diabetes mellitus) do not influence the development of PCO in canine cataract dogs. Small and medium-sized breeds develop significant PCO earlier than larger breeds. It is important to note that all eyes from all dogs in this study developed PCO in a time dependent manner.

Comparison of posterior capsule opacification between fellow eyes with two types of acrylic intraocular lens

PURPOSE

To compare the degree of posterior capsule opacification (PCO) and visual function between fellow eyes that received two different types of hydrophobic acrylic intraocular lenses (IOLs).

METHODS

Forty-five patients underwent bilateral phacoemulsification and implantation of an Alcon AcrySof IOL (MA60AC) in one eye and an AMO Sensar IOL (AR40e) in the fellow eye. The PCO density value was measured using the Scheimpflug videophotography system at 1, 6, 12, and 24 months after surgery. The incidence of eyes that required a neodymium:YAG (Nd:YAG) laser capsulotomy, visual acuity, and contrast sensitivity with and without a glare source were also examined.

RESULTS

The mean PCO value did not show a significant increase in either the AcrySof MA60AC or Sensar AR40e IOL groups, and was similar between the two groups throughout the 24-month follow-up period. The incidence of Nd:YAG laser capsulotomy was also the same between the groups. No significant difference was found in mean visual acuity between the two IOL groups during the follow-up, and there was no significant difference in photopic or mesopic contrast visual acuity with and without a glare source at 1 and 24 months after surgery.

CONCLUSION

The degree of PCO in eyes with an AcrySof IOL are almost the same as that in eyes with a Sensar IOL, with the results that visual acuity and contrast sensitivity with and without glare are similar.

Influence of optic edge design, optic material, and haptic design on capsular bend configuration

PURPOSE

To assess and classify capsular bend configuration at the optic rim and its association with posterior capsule (PCO) and anterior capsule opacification (ACO) and capsulorhexis contraction with various intraocular lenses (IOLs).

SETTING

Department of Ophthalmology, Medical University of Vienna, Vienna, Austria.

METHODS

A total of 659 post-cataract surgery eyes of 370 patients from different prospective randomized studies were evaluated. All eyes had standardized phacoemulsification surgery with implantation of an IOL in the capsular bag. The IOLs had a sharp or round optic edge design and were made of silicone, acrylic, or poly(methyl methacrylate) optic materials. One year postoperatively, the configuration of the capsular bend at the optic rim was assessed at the slitlamp, and standardized slitlamp images of ACO and fibrotic PCO were taken. One week, 1 year, and 3 years postoperatively, digital retroillumination images were taken for objective quantification of regeneratory PCO and the capsulorhexis area. The outcome measures were the type of capsular bend configuration, ACO score (0% to 100%), regeneratory PCO score (0 to 10), fibrotic PCO score (0 to 3), and amount of capsulorhexis contraction (mm(2)).

RESULTS

Four main types of capsular bend configuration were classified: parallel, "Y," right angle, and wrapping. The right-angle type was observed in the most cases (52%). Eyes with a wrapping capsular bend configuration had significantly less PCO, more capsulorhexis contraction, and more ACO than eyes with the other configurations. Wrapping capsule configuration was seen most often (55%) in round-edged silicone IOLs that had a thin optic rim.

CONCLUSION

The design and material of IOLs influenced the long-term capsular bend configuration at the optic rim. The right-angle type was the most common capsular bend configuration. Intraocular lenses with silicone optic material and a thin optic rim caused a wrapping capsule configuration and resulted in more capsulorhexis contraction and ACO, but less PCO.

Posterior Capsule Opacification in the Presence of an Intraocular Lens with a Sharp versus Rounded Optic Edge

PURPOSE

To compare the degree of posterior capsule opacification (PCO) and visual function in eyes implanted with an acrylic intraocular lens (IOL) with a sharp posterior optic edge with that in eyes implanted with an IOL with a rounded optic edge.

DESIGN

Randomized clinical trial.

PARTICIPANTS

Seventy-five consecutive patients scheduled for bilateral phacoemulsification were assigned randomly to 1 of 2 groups. One group received an acrylic IOL with a sharp edge (Sensar AR40e, AMO, Santa Ana, CA) in the left eye and an acrylic IOL of the same optic material and loops but with a rounded-edge optic (Sensar AR40) in the right eye. The other group received the sharp-edged IOL in the right eye and the rounded-edge IOL in the left eye. Sixty-nine patients (92%) completed follow-up.

INTERVENTION

All patients underwent implantation of a sharp-edged IOL in 1 eye and a rounded-edge IOL in the fellow eye.

MAIN OUTCOME MEASURES

The PCO value of these patients was measured using the Scheimpflug videophotography system at 1, 3, 6, 12, 18, and 24 months after surgery. The incidence of eyes that required a neodymium:yttrium-aluminum-garnet (Nd:YAG) laser posterior capsulotomy was examined. Visual acuity and contrast sensitivity with and without a glare source also were evaluated.

RESULTS

The mean PCO value in the sharp-edge IOL group was significantly less than that in the rounded-edge IOL group throughout the follow-up period. The incidence of Nd:YAG capsulotomy also was significantly less in the sharp-edge group than in the rounded-edge group (P = 0.0095). No significant difference was found in mean visual acuity during the 24 months of follow-up. However, contrast visual acuity with and without glare was significantly better in the sharp-edge group than in the rounded-edge group at 24 months after surgery.

CONCLUSIONS

The degree of posterior capsule opacification in eyes with an acrylic IOL with a sharp posterior optic edge is significantly less than that in eyes with a rounded-edge IOL, and the sharp-edge optic led to better contrast sensitivity with and without glare.

Effect of bag-in-the-lens implantation on posterior capsule opacification in human donor eyes and rabbit eyes

PURPOSE

To evaluate bag-in-the-lens implantation by studying the feasibility of implanting a new type of intraocular lens (IOL) and the occurrence of posterior capsule opacification (PCO) in human postmortem eyes and in eyes of living rabbits.

SETTING

Department of Ophthalmology, University of Antwerp, Belgium, and Netherlands Research Institute of Amsterdam, Amsterdam, The Netherlands.

METHODS

The IOL was implanted in 10 postmortem human donor eyes (in vitro study) and in 17 eyes of 10 rabbits (in vivo study). The postmortem capsular bags were cultured for 4 to 6 weeks, and the rabbits were killed 1 to 5 months after implantation. All capsular bags with the bag-in-the-lens were examined by light microscopy and scanning electron microscopy.

RESULTS

The IOL design was highly effective in restricting lens epithelial cell (LEC) proliferation in the remaining lens bag in human donor eyes and in rabbit eyes. In eyes in which the capsules were not positioned well within the groove of the IOL, LEC proliferation and PCO occurred.

CONCLUSION

Bag-in-the-lens implantation was highly effective in preventing PCO in vitro and in vivo provided the anterior and posterior capsules were secured properly in the peripheral groove of the IOL.

Preventing recurrent opacification of the visual pathway after pediatric cataract surgery

PURPOSE

To determine the rate of secondary opacification of the visual pathway following pediatric cataract surgery in children between the ages of 10 months and 7 years.

METHODS

The medical records of children less than 7 years old who underwent lens aspiration, posterior chamber intraocular lens (IOL) implantation, primary pars plana posterior capsulectomy, and anterior vitrectomy were reviewed retrospectively. Twenty-six eyes in 19 children were included in the study. All procedures were performed by an anterior segment surgeon and a vitreoretinal surgeon. Main outcome measures were the prevalence of re-opacification of the visual pathway and of early postoperative complications.

RESULTS

The visual pathway remained clear in 25 of 26 eyes (96%) after pediatric cataract surgery combined with primary pars plana posterior capsulectomy and anterior vitrectomy. The mean age at surgery was 46 +/- 23 months (+/-SD). Secondary opacification of the visual pathway occurred in one eye (4%), requiring another surgical procedure. At last follow-up (mean, 26 months; range, 6 to 79 months), the visual pathway was clear in all 26 eyes (100%). No cases of clinically significant IOL displacement or of retinal detachment were noted.

CONCLUSIONS

For children undergoing pediatric cataract surgery between the ages of 10 months and 7 years, IOL implantation combined with primary pars plana posterior capsulectomy and anterior vitrectomy is effective in preventing re-opacification of the visual pathway.

A prospective, randomised comparison of single and three piece acrylic foldable intraocular lenses

AIMS

To compare the postoperative performance of single and three piece acrylic foldable intraocular lenses (IOLs).

METHODS

20 patients underwent bilateral cataract surgery with a single piece SA30AL IOL in one eye and a three piece MA30BA IOL in the other eye. The eyes were randomly assigned to either a single or three piece lens. The amount of IOL decentration and tilt, area of anterior capsule opening, and degree of posterior capsule opacification were measured using the Scheimpflug anterior segment analysis system (Nidek EAS-1000). Visual acuity and contrast sensitivity were examined. Measurements were performed by masked examiners before and 1 day, 1 week, 1, 3, 6, and 18 months after surgery.

RESULTS

There were no significant differences between the two groups (p>0.05, paired t test) in the amount of IOL decentration, IOL tilt, area of anterior capsule opening, degree of posterior capsule opacification, best corrected visual acuity, and contrast sensitivity throughout the 18 month follow up period.

CONCLUSION

The single and three piece acrylic foldable IOLs are equally stable in the eye after surgery.

Posterior capsule opacification after implantation of CeeOn Edge 911A, PhacoFlex SI-40NB, and AcrySof MA60BM lenses

PURPOSE

To perform an intraindividual comparison of posterior capsule opacification (PCO) with 2 foldable intraocular lenses (IOLs) and a foldable acrylic IOL 1 year after in-the-bag implantation.

SETTINGS

Seven German ophthalmology centers.

METHODS

In an open prospective randomized multicenter study, each center intraindividually compared a high-refractive-index, sharp-edged optic silicone IOL (CeeOn Edge 911A, Pharmacia) with a high-refractive-index, round-edged optic silicone IOL (PhacoFlex SI-40NB, Allergan) or a sharp-edged optic acrylic IOL (AcrySof MA60BM, Alcon). Of 288 randomized patients, 247 had standard phacoemulsification with in-the-bag IOL implantation in both eyes by the same surgeon. One eye of each patient received a CeeOn Edge IOL and the fellow eye, an AcrySof or PhacoFlex IOL. A morphologic evaluation of PCO was performed using the Evaluation of Posterior Capsule Opacification (EPCO) system 1 to 2 weeks and 11 to 14 months after surgery. The digital pictures were evaluated by an independent investigator who was blind to the type of IOL. Intraindividual differences in EPCO scores were statistically evaluated by a 1-sided binomial test at an alpha-level of 5%.

RESULTS

One year after surgery, 127 patients with the AcrySof IOL and 102 patients with the PhacoFlex IOL in the control eye were reexamined. Functional results, safety, and handling were not significantly different between the 3 IOLs. All reexamined eyes had a very low PCO grade. The EPCO values revealed less PCO in eyes with the CeeOn Edge IOL than in eyes with the AcrySof or PhacoFlex IOL, but the difference was not statistically significant. A neodymium:YAG laser capsulotomy was performed in 1 eye with a CeeOn Edge IOL, 1 eye with an AcrySof IOL, and 2 eyes with a PhacoFlex IOL.

CONCLUSIONS

The EPCO PCO grade was low 1 year after implantation of CeeOn Edge 911A, PhacoFlex SI-40NB, and AcrySof MA60BM IOLs; there was no statistically significant difference between the IOLs. The impact of IOL material and edge design on PCO development might be relevant in a long-term follow-up of this study.

Functional outcomes of acrylic intraocular lenses in pediatric cataract surgery

PURPOSE

To evaluate the functional outcomes of in-the-bag implantation of acrylic intraocular lenses (IOLs) with posterior continuous curvilinear capsulorhexis (PCCC), without PCCC, with PCCC and anterior vitrectomy, and with PCCC and optic capture in pediatric cataract surgery.

SETTING

Pediatric Ophthalmology Service, Guru Nanak Eye Centre, New Delhi, India.

METHODS

Forty-two eyes of 25 children were included in this prospective study. All eyes had in-the-bag implantation of an AcrySof IOL (Alcon). Twenty-five eyes had had an anterior continuous curvilinear capsulorhexis (ACCC) (Group A). Seventeen eyes had PCCC along with ACCC (Group B), 4 had anterior vitrectomy combined with PCCC (Group C), and 6 had PCCC with IOL optic capture through the PCCC (Group D). Secondary opacification of the visual axis, visual acuity, and possible complications were observed and analyzed.

RESULTS

The mean age of the patients was 78 months (range 36 to 144 months). The mean follow-up was 13 months (range 6 to 18 months). Four eyes (16%) in Group A developed visually significant posterior capsule opacification (PCO) involving the central visual axis and required secondary capsulotomy. All eyes in Groups B, C, and D had a clear visual axis at the last follow-up and did not require a secondary procedure. Minimal postoperative inflammation (ie, aqueous flare and IOL deposits ) was seen in all groups. The mean preoperative decimal best corrected visual acuity (BCVA) in Groups A, B, C, and D was 0.095, 0.055, 0.174, and 0.039, respectively. Postoperatively, the BCVA was 0.54, 0.66, 0.66, and 0.66, respectively.

CONCLUSIONS

An optimal-sized ACCC followed by in-the-bag implantation of a foldable acrylic IOL helped maintain a clear visual axis by delaying the onset of PCO and leading to milder PCO. The benefits of a foldable acrylic IOL in pediatric cataract surgery can be increased by combining it with PCCC, with or without anterior vitrectomy, or with optic capture of the IOL.

Anterior capsule relationship of the AcryS of intraocular lens optic and posterior capsule opacification

OBJECTIVE

To evaluate the relationship of the anterior capsule and the AcrySof MA30BA intraocular lens (IOL) and its impact on the development of central posterior capsule opacification (PCO).

DESIGN

Prospective, randomized, controlled trial.

PARTICIPANTS

Two hundred two patients with senile cataracts received an AcrySof IOL between July and December 1998 at Iladevi Cataract and IOL Research Center, Ahmedabad, India.

INTERVENTION

Patients were randomized prospectively to receive 1 of the 3 possibilities of anterior capsule and IOL optic relationship: group 1, total anterior capsule cover (360 degrees ) of the optic; group 2, no anterior capsule cover (360 degrees ) of the optic; group 3, partial anterior capsule cover (<360 degrees ) of the optic. After surgery, slit-lamp video photography was performed every 6 months for 3 years. Analyses of variance and chi-square tests were used to compare treatment groups.

MAIN OUTCOME MEASURES

Incidence of PCO in the 3 groups. The posterior capsule was divided into 3 zones: peripheral, central 3 mm, and midperipheral (the space between the peripheral and the central zones).

RESULTS

The average follow-up was 35.3 +/- 1.52 months in all the groups. At 3 years, the rate of central PCO was 6.4% in group 1, 7.1% in group 2, and 5.9% in group 3 (P = 0.9). Midperipheral PCO was present in 24.2% in group 1, 16% in group 2, and 20.6% in group 3 (P = 0.9). Peripheral PCO was seen in 100% of patients in all groups. The neodynium:yttrium-aluminum-garnet laser (Nd:YAG) posterior capsulotomy rate was 0% in all groups.

CONCLUSIONS

There was no significant difference in the incidence of development of central PCO among the 3 groups. No patient experienced central PCO that required Nd:YAG capsulotomy. When using the AcrySof IOL model MA30BA, the relationship of the anterior capsule and the IOL does not seem to be a factor that relates to the development of central PCO.

Cumulative probability of neodymium: YAG laser posterior capsulotomy after phacoemulsification

PURPOSE

To retrospectively analyze the cumulative probability of neodymium:YAG (Nd:YAG) laser posterior capsulotomy after phacoemulsification and to evaluate the risk factors.

SETTING

Ando Eye Clinic, Kanagawa, Japan.

METHODS

In 3997 eyes that had phacoemulsification with an intact continuous curvilinear capsulorhexis, the cumulative probability of posterior capsulotomy was computed by Kaplan-Meier survival analysis and risk factors were analyzed using the Cox proportional hazards regression model. The variables tested were sex; age; type of cataract; preoperative best corrected visual acuity (BCVA); presence of diabetes mellitus, diabetic retinopathy, or retinitis pigmentosa; type of intraocular lens (IOL); and the year the operation was performed. The IOLs were categorized as 3-piece poly(methyl methacrylate) (PMMA), 1-piece PMMA, 3-piece silicone, and acrylic foldable.

RESULTS

The cumulative probability of capsulotomy after cataract surgery was 1.95%, 18.50%, and 32.70% at 1, 3, and 5 years, respectively. Positive risk factors included a better preoperative BCVA (P =.0005; risk ratio [RR], 1.7; 95% confidence interval [CI], 1.3-2.5) and the presence of retinitis pigmentosa (P<.0001; RR, 6.6; 95% CI, 3.7-11.6). Women had a significantly greater probability of Nd:YAG laser posterior capsulotomy (P =.016; RR, 1.4; 95% CI, 1.1-1.8). The type of IOL was significantly related to the probability of Nd:YAG laser capsulotomy, with the foldable acrylic IOL having a significantly lower probability of capsulotomy. The 1-piece PMMA IOL had a significantly higher risk than 3-piece PMMA and 3-piece silicone IOLs.

CONCLUSIONS

The probability of Nd:YAG laser capsulotomy was higher in women, in eyes with a better preoperative BCVA, and in patients with retinitis pigmentosa. The foldable acrylic IOL had a significantly lower probability of capsulotomy.

Use of Nd:YAG laser capsulotomy

Surgery for cataract removal has become successively refined such that posterior capsular opacification is the most common problem presenting after modern cataract extraction. Various techniques and treatments exist to manage patients with posterior capsular opacification using Nd:YAG capsulotomy. There are many possible variations in initial assessment, pre-laser treatments, laser techniques, and follow-up routines. The literature on the use of Nd:YAG laser for capsulotomy was reviewed and interpreted. This article presents the currently available knowledge in a format that allows the practitioner to tailor an evidence-based protocol for treating patients with symptomatic posterior capsule opacification.

Hydrophobic acrylic versus heparin surface-modified polymethylmethacrylate intraocular lens: a biocompatibility study

BACKGROUND

The implant of intraocular lenses (IOLs) following cataract surgery induces a foreign-body reaction to the IOL and a response on the part of the lens epithelial cells (LECs). The purpose of this study was to compare these aspects after the implantation of two different IOL materials.

METHODS

Thirty-six cataract patients were randomised to receive two different foldable lens: an acrylic hydrophobic IOL (Acrysof MA30BA) and a heparin surface-modified (HSM) polymethylmethacrylate IOL (Pharmacia & Upjohn 809C) after phacoemulsification. Slit-lamp biomicroscopy with specular technique was used to assess the inflammatory cell adhesion on the anterior IOL surface, anterior capsule opacification (ACO) and membrane growth from the rhexis edge at 7, 30, 90, 180 and 360 days after surgery.

RESULTS

The 809C group showed a higher percentage of patients with slight inflammatory cell adhesion on the anterior cell surface and a higher small cellular density during the whole follow-up period. The epithelioid cell response was greater in the 809C group than the Acrysof group but the difference between the two groups was not statistically significant. The ACO increased during the follow-up in both groups but was significantly higher in the 809C group.

CONCLUSION

Acrysof lenses are more biocompatible than HSM IOLs, showing a lower grade of inflammatory cell adhesion and ACO. The implantation of these lenses may be particularly indicated in patients with pathologies predisposing to blood-aqueous barrier damage.

Inhibition of lens epithelial cell migration at the intraocular lens optic edge: role of capsule bending and contact pressure

PURPOSE

To evaluate the inhibitory effect of a sharp intraocular lens (IOL) optic edge, a sharp capsule bend, and contact pressure between the optic edge and posterior capsule on lens epithelial cell (LEC) migration.

SETTING

Department of Ophthalmology, Kyorin University, Tokyo, Japan.

METHODS

This in vitro laboratory study evaluated a tumble-polished convex-plano IOL (CP group), an AcrySof IOL (Alcon) with a sharp edge (AS group), a new IOL with a round ridge (RR group), and a new IOL with a sharp ridge (SR group). The 2 new IOLs have high ridges and high angled loops that create firm contact between the ridge and posterior capsule. After sham cataract surgery, an IOL and a capsular tension ring (CTR) were implanted in the capsular bag of rabbit eyes. The extracted capsular bags containing the CTR and IOL were cultured. The inhibitory effect of each IOL on cell migration was analyzed. Furthermore, LEC migration on the posterior capsule was compared in culture between capsules having a sharp right angle and those with gradually curving bends.

RESULTS

The inhibitory effect on cell migration was statistically greatest in the SR group followed by the RR, AS, and CP groups. A sharp capsule bend did not inhibit cell migration.

CONCLUSIONS

The results suggest that inhibition of cell migration at the optic edge is regulated by the degree of contact pressure between the optic edge and posterior capsule. A sharp capsule bend might indicate strong contact but does not in itself inhibit cell migration.

Single-action implantation of a 3-piece acrylic intraocular lens with an injector

We report a method to insert a 3-piece AcrySof MA30BA acrylic foldable intraocular lens (IOL) (Alcon) in a single action using a Monarch II (Alcon) injector. The technique was used in 134 eyes. The incision widths ranged from 3.00 to 3.75 mm. The IOLs were successfully inserted in the capsular bag. Complications included cracks in the IOL optic in 3 eyes (3%), haptic damage in 3 eyes (3%), and inadequate self-sealing of the incision in 18 eyes (13%).

Mathematical modeling of the forces between an intraocular lens and the capsule

PURPOSE

To model the pressure relationship between an intraocular lens (IOL) and the capsular bag.

SETTING

Department of Physics, Kings' College, London University, London, United Kingdom.

METHODS

A mathematical model was made of the forces between the capsule and IOL showing that the pressure related to the local radius of curvature of the IOL at any given point. The local radius of curvature for round-edged and square-edged IOLs was measured from electron micrographs of the IOL profiles, and the corresponding pressure profiles were calculated and compared.

RESULTS

The pressure between an IOL and the capsular bag was proportional to the quotient of the tension in the capsule divided by the local radius of curvature of the IOL, with a constant of proportionality that depended on the coefficient of friction between the capsule and IOL. Measuring the local radius of curvature of the 2 IOL types suggested a pressure increase of at least 69% +/- 6% at the optic edge with the square-edged IOL.

CONCLUSIONS

The mathematical model predicted that IOLs with square-edged optic profiles exerts higher pressure on the posterior capsule than IOLs with round-edged optic profiles. The higher pressure may form a physical barrier to lens epithelial cell migration onto the posterior capsule.

Systems of analysis of posterior capsule opacification

This paper demonstrates the wide variety of systems for the analysis of posterior capsular opacification (PCO). No single system has been proved to be a gold standard and it is difficult to comment on the advantages of one system over another with the limited current knowledge on the effects of PCO on vision. There are few studies that actually compare the different systems of analysis. Researchers must ensure that the systems they use for PCO analysis are objective and must give maximum consideration to ensuring potential systematic errors are reduced to a minimum. Further research is required into how the various types and locations of PCO affect vision and how well different systems of analysis perform.

Failure of a discontinuous bend to prevent lens epithelial cell migration in vitro

PURPOSE

To assess the effect of substrate geometry (discontinuous bend) on lens epithelial cell (LEC) growth in vitro.

SETTING

Department of Ophthalmology, St. Thomas' Hospital, London, United Kingdom.

METHODS

Culture wells with central depths of 0.4 mm, 1.0 mm, or 3.0 mm and a sharp square-edged profile (discontinuous bend) or a round-edged profile (continuous bend) were produced from a block of poly(methyl methacrylate). Freshly harvested bovine LECs were attached to the center of each well and cultured using standard techniques. Observations were made of whether LECs grew out of the wells and of the time required to do so.

RESULTS

Lens epithelial cells migrated out of all the wells. There was no significant difference in the rate at which they migrated out of round-edged and square-edged wells.

CONCLUSIONS

In vitro, a sharp discontinuous bend did not appear to induce contact inhibition of migrating LECs nor did it significantly hinder the rate at which LECs migrated. Therefore, a discontinuous bend in the lens capsule in isolation is unlikely to be responsible for the observed reduction in posterior capsule opacification associated with the use of square-edged IOLs.

Effect of a capsular tension ring on intraocular lens decentration and tilting after cataract surgery

PURPOSE

To evaluate the effect of a capsular tension ring (CTR) on the tilting and decentration of intraocular lenses (IOLs) after cataract surgery.

SETTING

Department of Ophthalmology, Ilsan Paik Hospital, Inje University, Kyunggyi-do, Korea.

METHODS

Cataract surgery was performed in both eyes of 20 patients ranging in age from 57 to 75 years. The 40 eyes were divided into 2 groups based on whether a CTR (Lucid Korea) was implanted. Each patient received a CTR in 1 eye only. All IOLs (AcrySof MA60BM, Alcon) were implanted in the capsular bag after a continuous curvilinear capsulorhexis smaller than the IOL optic was created and phacoemulsification performed. The extent of IOL tilting and decentration was measured with the EAS-1000 anterior eye segment analysis system 7, 30, and 60 days after surgery.

RESULTS

The extent of IOL decentration was statistically significantly less in eyes with both an IOL and CTR than in those with an IOL only. The mean decentration in the CTR-IOL group was 0.38 mm +/- 0.16 (SD) at 7 days, 0.43 +/- 0.15 mm at 30 days, and 0.42 +/- 0.17 mm at 60 days. The mean values in the IOL-only group were 0.49 +/- 0.11 mm, 0.53 +/- 0.14 mm, and 0.57 +/- 0.16 mm, respectively. The amount of IOL tilting was also significantly less in the CTR-IOL group. The mean tilting in the CTR-IOL group was 2.22 +/- 0.46 degrees at 7 days, 2.36 +/- 0.50 degrees at 30 days, and 2.47 +/- 0.40 degrees at 60 days. The mean values in the IOL-only group were 3.14 +/- 0.65 degrees, 2.91 +/- 0.67 degrees, and 3.06 +/- 0.56 degrees, respectively.

CONCLUSION

These results indicate that the CTR reduces undesirable postsurgical IOL movement for at least 60 days.

Survey of intraocular lens material and design

Modern cataract surgery is constantly evolving and improving in terms of lens material and design. Researchers and physicians strive to obtain better refractive correction with smaller wound size and minimizing host cell response to limit the proliferation of lens epithelial cells leading to opacification of the lens capsule. Intraocular lens material varies in water content, refractive index, and tensile strength. Intraocular lens design has undergone revisions to prohibit lens epithelial cell migration and reflection of internal and external light. The evolution of intraocular lens and extracapsular cataract surgery has lead to faster postoperative recovery and better visual outcomes.

Risk factors for secondary membrane formation after removal of pediatric cataract

PURPOSE

To evaluate the incidence of secondary membrane formation, factors that lead to its development, and the frequency of procedures to treat these membranes in children after cataract surgery.

SETTING

Department of Pediatric Ophthalmology, Children's Hospital of Pittsburgh, Pittsburgh, Pennsylvania, USA.

METHODS

Clinical records of 152 patients (190 eyes) who had cataract extraction between January 1986 and 1996 were reviewed retrospectively. The mean follow-up was 6 years (range 2 to 13 years). Cataract surgery was performed through a limbal incision in all cases. Twenty-eight eyes had a primary posterior capsulectomy, and 120 eyes had posterior capsulectomy combined with an anterior vitrectomy. In 42 eyes, the posterior capsule was left intact. Nineteen eyes received a primary intraocular lens (IOL), 15 eyes received a secondary IOL, and 156 eyes were rehabilitated with spectacles or contact lenses.

RESULTS

Seventy-two eyes (37.9%) developed secondary membrane a mean of 8.9 months postoperatively (range 3 weeks to 53 months). Membranes occurred in 78.6% of eyes with an intact posterior capsule, 42.9% with posterior capsulectomy, and 22.5% with combined posterior capsulectomy and anterior vitrectomy. Secondary membrane formation was associated with not performing a posterior capsulectomy with anterior vitrectomy (P < .001) and the presence of a primary IOL (P < .001). Younger age at surgery increased the chance of secondary membrane formation in patients who had posterior capsulectomy and anterior vitrectomy (P < .01).

CONCLUSIONS

The younger the child at cataract surgery, the greater the risk of secondary membrane. Primary posterior capsulectomy combined with an anterior vitrectomy decreased but did not eliminate the incidence of secondary membrane.

Posterior capsule opacification with AcrySof and poly(methyl methacrylate) intraocular lenses. Comparative study with a 3-year follow-up

PURPOSE

To evaluate whether reports of reduced posterior capsule opacification (PCO) rates with AcrySof intraocular lenses (IOLs) are applicable to a mixed group of cataract patients in everyday surgical practice.

SETTING

Department of Ophthalmology, Kärnsjukhuset, Skövde, Sweden.

METHODS

A retrospective study comparing a study group receiving an AcrySof IOL (n = 145) and a group receiving a poly(methyl methacrylate) (PMMA) IOL (n = 153) was performed. The follow-up was 3 years in both groups. The performance of a neodymium:YAG laser capsulotomy was used as the end point for clinically significant PCO.

RESULTS

Nine capsulotomies (6.2%) were performed in the AcrySof group and 34 (22.2%) in the PMMA group. The difference in the capsulotomy rate between the 2 groups was highly significant (P <.001). The relative risk was 3.6 times higher in the PMMA group.

CONCLUSIONS

There was a significant difference in the frequency of capsulotomy between AcrySof and PMMA IOLs in a mixed group of cataract patients in everyday clinical practice. This finding indicates the importance of the IOL type in PCO formation.

Influence of glistenings on the optical quality of acrylic foldable intraocular lens

AIMS

To assess the influence of glistenings on the optical quality of acrylic foldable intraocular lens.

METHODS

Several degrees of glistenings in the optic were experimentally created by immersing the lens in water at 37 degrees C for 48 hours and then at 25 degrees C for 24 hours. Optical bench tests were carried out in water including measurements of spectral transmittance with the spectrophotometer, intensity of forward scattering using the integrating sphere photometer, modulation transfer function, and resolving power at various contrasts with and without the veiling glare light source.

RESULTS

Glistenings of 1+ to 4+ degrees were created, among which the 4+ glistenings seemed to be extremely intense and thought to be beyond the range of clinical settings. Clinically feasible level of glistenings, up to 3+, did not adversely influence spectral transmittance, scattering, modulation transfer function, and resolving power at various contrasts. The 4+ glistenings caused mild to moderate deteriorations of the optical quality of the lens.

CONCLUSION

The optical quality of the acrylic foldable intraocular lens is not significantly affected by the level of glistenings usually seen in the clinical setting.

Combined refractive lensectomy and laser in situ keratomileusis to correct extreme myopia

Refractive lensectomy followed by laser in situ keratomileusis (LASIK) was performed in both eyes of a severely myopic patient. An uncorrected visual acuity of 20/20 was achieved in the right eye with a manifest refraction of plano -0.25 x 65. Intentional monovision correction of the left eye left a manifest refraction of -0.75 diopter. Best corrected visual acuity improved by 1 Snellen line to 20/20 in both eyes. Follow-up evaluation will be required to assess the long-term refractive stability and the incidence of retinal detachment after combined refractive lensectomy and LASIK.

Posterior capsule opacification and anterior capsule opacification

Posterior capsule opacification (PCO) is still the most frequent complication of cataract surgery. A variety of studies has led to a better understanding of the pathogenesis of PCO, and strategies of molecular biology have produced new therapeutic options, such as immunological techniques or gene therapeutic approaches. Surgical strategies and intra-ocular lens-dependent factors also are capable to reduce the rate of PCO. In-the-bag implantation of intra-ocular lenses with a sharp optic edge seems to be effective in inhibiting equatorial lens epithelial cell migration to the center of the posterior capsule. Several PCO documentation systems have been developed that will lead to more exact and better comparable recording of PCO rates. In the year 2000, PCO or secondary cataract is still the most frequent complication after extracapsular cataract surgery. In a 1998 meta-analysis, PCO rates of 11.8% 1 year after extracapsular cataract surgery with intraocular lens implantation, 20.7% after 3 years, and 28.4 % after 5 years have been reported. For the United States, it has been estimated that the overall expenses for treatment of PCO are only exceeded by the costs for cataract treatment itself. In the past decade, a lot of experimental and clinical studies have been performed on this topic. They have led to 1) to a better understanding of the pathogenesis of the development of anterior and posterior capsule opacification; 2) more objective and better comparable systems of documentation and analysis of PCO; and a number of 3) surgical and 4) pharmaceutical strategies to prevent PCO.