Inhibition of posterior capsule opacification: the effect of colchicine in a sustained drug delivery system

The Effects of Three-Piece or Single-Piece Acrylic Intraocular Lens Implantation on Posterior Capsule Opacification

Purpose

To evaluate the development of posterior capsule opacification (PCO) in patients implanted with 5.5 mm optics, single-piece or three-piece acrylic intraocular lens (IOL) in cataract surgery prospectively.

Methods

This study was carried out on 267 eyes of 249 patients implanted with three-piece, 5.5 mm optics, acrylic IOL and 252 eyes of 244 patients implanted with single-piece, 5.5 mm optics, acrylic IOL by phacoemulsification technique between September 2001 and February 2003. A total of 519 eyes of 493 patients were prospectively evaluated for PCO development during the 25-month period. All the patients were analyzed periodically with anterior segment retroillumination photography. The data provided were analyzed with chi-square method.

Results

The results between the two groups for PCO development were not statistically significant. However, there was a prominent opacification of the posterior capsule where the optic and haptic junction of IOL was positioned in some patients implanted with single-piece IOL. During the follow-up period, no patients implanted with either three-piece or single-piece acrylic IOL required Nd:YAG laser capsulotomy.

Conclusions

Biocompatibility and reduced rate of PCO development are among the leading features of new generation IOLs. The intracapsular implantation of 5.5 mm optics acrylic IOLs resulted in decreased incidence of PCO and therefore greater patient satisfaction. Further studies investigating the effects of IOL optics, haptic structure and length, capsulorrhexis size, and IOL material and design features on PCO development will clarify the subject.

Effect of an MG132-Sustained Drug Delivery Capsular Ring on the Inhibition of Posterior Capsule Opacification in a Rabbit Model

PURPOSE

To design an MG132-sustained drug delivery capsular ring (SDDCR) and investigate its effect on the inhibition of posterior capsule opacification (PCO) in a rabbit model.

METHODS

The SDDCRs were prepared by forming a slice of film made by the mixture of poly lactic-co-glycolic acid (PLGA) and MG132 on the surface of capsular tension rings (CTRs). The drug-loading capacity, entrapment efficiency, and in vitro release of the drug-containing film were detected. Eighteen New Zealand white rabbits were operated with phacoemulsification and MG132-SDDCRs/PLGA-CTRs/CTRs implantation in the single eye. The images of the anterior segments were acquired at certain days, and the epithelial-mesenchymal transition (EMT) markers were detected by western blot and immunofluorescence.

RESULTS

The drug-loading capacity and entrapment efficiency of MG132-SDDCRs were 1.15% ± 0.04% and 66.16% ± 0.027%, respectively, and the drug released well within a month. The PCO degree of the MG132-SDDCR group was significantly lower than the other groups. The expression of alpha-smooth muscle actin, fibronectin, vimentin, and collagen-I was lower, and the expression of E-cadherin (E-cad) was higher in the MG132-SDDCR group than the other groups.

CONCLUSIONS

MG132-SDDCRs could be established successfully. The PCO process was prevented, and the expression of EMT markers was inhibited by the implantation of MG132-SDDCRs, indicating that this could be a potential treatment against PCO.

Prevention of posterior capsular opacification

Posterior capsular opacification (PCO) is a common complication of cataract surgery. The development of PCO is due to a combination of the processes of proliferation, migration, and transdifferentiation of residual lens epithelial cells (LECs) on the lens capsule. In the past decades, various forms of PCO prevention have been examined, including adjustments of techniques and intraocular lens materials, pharmacological treatments, and prevention by interfering with biological processes in LECs. The only method so far that seems effective is the implantation of an intraocular lens with sharp edged optics to mechanically prevent PCO formation. In this review, current knowledge of the prevention of PCO will be described. We illustrate the biological pathways underlying PCO formation and the various approaches to interfere with the biological processes to prevent PCO. In this type of prevention, the use of nanotechnological advances can play a role.

Nanostructured lipid carrier surface modified with Eudragit RS 100 and its potential ophthalmic functions

This study was carried out to evaluate the ocular performance of a cationic Eudragit (EDU) RS 100-coated nanostructured lipid carrier (NLC). The genistein encapsulated NLC (GEN-NLC) was produced using the melt-emulsification technique followed by surface absorption of EDU RS 100. The EDU RS 100 increased the surface zeta potential from -7.46 mV to +13.60 mV, by uniformly forming a spherical coating outside the NLC surface, as shown by transmission electron microscopy images. The EDU RS 100 on the NLC surface effectively improved the NLC stability by inhibiting particle size growth. The obtained EDU RS 100-GEN-NLC showed extended precorneal clearance and a 1.22-fold increase in AUC (area under the curve) compared with the bare NLC in a Gamma scintigraphic evaluation. The EDU RS 100 modification also significantly increased corneal penetration producing a 3.3-fold increase in apparent permeability coefficients (Papp) compared with references. Draize and cytotoxicity testing confirmed that the developed EDU RS 100-GEN-NLC was nonirritant to ocular tissues and nontoxic to corneal cells. These results indicate that the NLC surface modified by EDU RS 100 significantly improves the NLC properties and exhibits many advantages for ocular use.

Shikonin inhibits the proliferation of human lens epithelial cells by inducing apoptosis through ROS and caspase-dependent pathway

Shikonin is a compound from the herbal plant Lithospermum erythrorhizon that has been proved to possess powerful anti-proliferative effect on many kinds of cancers and to be safe in in vivo study. Posterior capsular opacification (PCO), the most frequent complication of cataract surgery, is mainly caused by the uncontrolled proliferation of retained human lens epithelial cells (HLEs). In this study, we investigated the effect of shikonin on the proliferation of HLEs and explored its underlying mechanism of action. Shikonin significantly inhibited the proliferation of HLEs in a dose- and time-dependent manner. Its anti-proliferative effect was exerted through induction of apoptosis. Reactive oxygen species (ROS) generation played an essential role in this apoptotic process. Interestingly, scavenging of ROS completely blocked the apoptosis induced by shikonin. In addition, the treatment of shikonin in HLEs significantly increased the ratio of Bax/Bcl-2, disrupted mitochondria membrane potential (MMP) and activated caspases. The inhibition of caspase largely blocks the apoptosis. The changes of MAPK pathway were also demonstrated. Shikonin effectively inhibited the phosphorylation of ERK, while it activated the phosphorylation of JNK and p38. These results suggested that shikonin inhibited the proliferation of HLEs by inducing apoptosis through ROS generation and the caspase-dependent pathway and the MAPK pathway was also involved.

Design, characterization, and in vitro cellular inhibition and uptake of optimized genistein-loaded NLC for the prevention of posterior capsular opacification using response surface methodology

This study was to design an innovative nanostructured lipid carrier (NLC) for drug delivery of genistein applied after cataract surgery for the prevention of posterior capsular opacification. NLC loaded with genistein (GEN-NLC) was produced with Compritol 888 ATO, Gelucire 44/14 and Miglyol 812N, stabilized by Solutol(®) HS15 by melt emulsification method. A 2(4) central composite design of 4 independent variables was performed for optimization. Effects of drug concentration, Gelucire 44/14 concentration in total solid lipid, liquid lipid concentration, and surfactant concentration on the mean particle size, polydispersity index, zeta potential and encapsulation efficiency were investigated. Analysis of variance (ANOVA) statistical test was used to assess the optimization. The optimized GEN-NLC showed a homogeneous particle size of 90.16 nm (with PI=0.33) of negatively charged surface (-25.08 mv) and high encapsulation efficiency (91.14%). Particle morphology assessed by TEM revealed a spherical shape. DSC analyses confirmed that GEN was mostly entrapped in amorphous state. In vitro release experiments indicated a prolonged and controlled genistein release for 72 h. In vitro growth inhibition assay showed an effective growth inhibition of GEN-NLCs on human lens epithelial cells (HLECs). Preliminary cellular uptake test proved a enhanced penetration of genistein into HLECs when delivered in NLC.

Doxorubicin-loaded MePEG-PCL nanoparticles for prevention of posterior capsular opacification

AIMS

Cytotoxic drugs are considered as potent candidates for the prevention of posterior capsular opacification (PCO), but the toxicity incited to healthy intraocular structures is a major concern. In this study, the authors evaluated the effect of PEG methyl ether-block-poly(ε-caprolactone) (MePEG-PCL) doxorubicin (DOX)-loaded nanoparticles (NPs) for prevention of PCO and their influence on intraocular tissues.

METHODS

MePEG-PCL DOX NPs were prepared and characterized. The cytotoxic effect of DOX NPs on lens epithelial cells was compared with free drug. Its effect on PCO prevention following single subconjunctival delivery to lensectomized rabbits was assessed. Toxicity to intraocular structures was evaluated by specular microscopy, electroretinography and histopathology. The availability of DOX in aqueous humor was determined by HPLC.

RESULTS

The cytotoxic effect of DOX NPs was higher compared with free DOX due to prolonged retention within the cells. A significant reduction in degree of PCO was observed in DOX NP-treated eyes compared with untreated controls. There was no significant change in the density and morphology of corneal endothelial cells or the histology of intraocular structures. Electroretinographs of treated eyes did not change compared with the pretreatment values. DOX could be detected by HPLC in the aqueous humor up to 48 h following single subconjunctival injection.

CONCLUSION

The authors conclude that DOX-loaded MePEG-PCL NPs show promise as a new approach to selectively kill highly proliferative lens epithelial cells in vivo following cataract surgery, while sparing normal tissue.

Study of antiproliferative effects of synthetic substances against lens epithelial cell line (SRA 01/04)

A cataract is a clouded area of the eye, which impairs vision. Cataracts can be caused by a natural hardening of the lens in the elderly, or may be the result of eye injury. However there is a treatment by extracapsular surgery, almost 50% of operations are followed by another posterior capsule opacification. This secondary cataract is due to abnormal cellular proliferation. Pharmacologic inhibition of this cellular proliferation would be a very promising treatment. The objective of our study is to test some antiproliferative drugs, less toxic than those currently used such as 5-FU or mytomycin C. We have investigated the in vitro effects of several molecules (V0 and its derivatives) on a proliferative human lens epithelial cell line (SRA 01/04). During a first step, we have measured the IC50 of each molecule. After this first screening, we have studied the kinetic of the cell growth with or without the molecules at different concentration. Then, flow cytometry was used to determine the phase of the cell cycle at which the proliferation stopped. This study has shown that 3 molecules V19, V1, and A190 have an interesting profile in vitro and were selected to analyze their mechanism of action.

Safety and efficacy of intracapsular tranilast microspheres in experimental posterior capsule opacification

PURPOSE

To evaluate the safety and efficacy of a sustained-release agent designed to reduce posterior capsule opacification (PCO).

SETTING

Department of Ophthalmology, EENT Hospital, Fudan University, Shanghai, Peoples Republic of China.

METHODS

Free tranilast (TFree) was incorporated into polylactic acid microspheres and then tested using a rabbit model of PCO. Twenty-nine rabbits were randomized into 5 groups treated with balanced saline solution (BSS control); TFree; or 0.5, 1.0, or 2.0 mg tranilast microspheres (TMicro). Standard phacoemulsification cataract surgery, including manual aspiration of all visible soft lens matter, was performed in all groups. The selected test agent was then injected into the lens capsule. Postoperative clinical examinations were performed at 1, 3, 7, 14, 30, 60, and 90 days. Posterior capsule opacification was quantified using high-resolution computer image analysis at 1, 2, and 3 months. Histological examination was performed at 3 months.

RESULTS

Eyes treated with TMicro had significantly less PCO than the eyes in the BSS and TFree groups. While the BSS control eyes had increased PCO over 3 months, eyes in the TMicro group had reduced PCO over time in a dose-dependent fashion. Histological examination showed reduced lens epithelial cell proliferation in the TMicro groups, with no manifest damage to the cornea, iris, or retina compared with the BSS controls. There was a transient increase in postoperative inflammation in all tranilast-treated groups compared with the BSS controls.

CONCLUSION

Sustained-release intracapsular tranilast reduced PCO in an experimental model of PCO, suggesting further investigation of its therapeutic potential is justified.

[Posterior capsule opacification after phacoemulsification in patients with rheumatoid arthritis]

PURPOSE

To assess the posterior capsule opacification (PCO) rate after phacoemulsification with polyacrylic intraocular lens (IOL) implantation in patients with rheumatoid arthritis (RA) compared with the controls, and to assess whether preoperative activity of RA is associated with a higher incidence of PCO.

METHODS

24 eyes of 20 RA patients operated in a period of 4 years were included in our study. A control group of 20 eyes from 20 health subjects were also included in our study. All procedures were performed by a single surgeon with the same surgical technique and postoperative medication.

RESULTS

One year postoperatively in two eyes (8.3%) of RA-patients lens epithelial cells (LEC) migration of grade 1 was observed, in controls also in two eyes (10%). No correlation was observed between age, duration of RA or preoperative activity of RA and the PCO rate.

CONCLUSION

Following acrylic IOL implantation, the PCO rate one year after surgery was 8.3% in RA patients and 10% in controls. RA patients present no higher risk for PCO development than controls.

Evaluation of the effects of hydrodissection with antimitotics using a rabbit model of Soemmering's ring formation

BACKGROUND

Regeneration/proliferation of lens material within the capsular bag still is the most frequent complication after cataract surgery. We aimed to evaluate the effects of hydrodissection with low doses of antimitotics on the overall regeneration/proliferation of lens material in rabbit eyes, using a model allowing the lens material to be confined to the equatorial region of the capsular bag, facilitating its quantification.

METHODS

Twelve albino rabbits underwent bilateral phacoemulsification. Their eyes were randomized to receive 0.4 cc of balanced salt solution, 5-fluorouracil (12.5 mg/mL) or mitomycin C (0.1 mg/mL) during hydrodissection. They were left aphakic, so the capsulorhexis would fuse with the posterior capsule postoperatively. After 4 weeks, killing/enucleation was performed. Regeneration/proliferation of lens material within the equatorial capsular bag (Soemmering's ring) was graded from the Miyake-Apple view (0-4). Its area was also calculated (microm(2)) from direct measurements performed on histological sections.

RESULTS

The capsulorhexis margin fused with the peripheral posterior capsule, so the central posterior capsule remained clear. There was no significant difference among the groups (Kruskal-Wallis test) regarding Soemmering's ring gross grading (P = 0.511), number of lens epithelial cell layers lining the inner surface of the capsular bag (P = 0.310) and Soemmering's ring microscopic cross-sectional area (P = 0.638).

CONCLUSIONS

The effect of different solutions on after-cataract should be assessed in terms of overall regeneration/proliferation of lens material within the capsular bag, in addition to posterior capsule opacification. When administered in low doses during hydrodissection, 5-fluorouracil and mitomycin C did not show a significant inhibitory effect on after-cataract formation in rabbit eyes.

[New methods for the prevention of posterior capsule opacification]

Even though tremendous advances have been made especially during the last 10-15 years in terms of surgical techniques and improvement of implant technology, posterior capsule opacification (PCO) still remains a serious long-term complication. New clinical and laboratory studies (especially of autopsy eyes) have improved our understanding of how IOL design and material influence PCO. Sharp edge optic designs of IOLs of various materials have been shown to significantly reduce secondary cataract. The application of pharmacological substances selectively into the capsular bag is now possible due to the development of the PerfectCapsule System for vacuum-sealed capsule irrigation. Major advances in other areas of biotechnology and immunology including gene therapeutic methods offer totally new approaches for the future in the elimination of lens epithelium cells from the capsular bag. This survey gives an update on current and future means and trends to reduce or prevent PCO formation.

Efficacy of various drugs in the prevention of posterior capsule opacification: experimental study of rabbit eyes

PURPOSE

To assess the efficacy of various drugs in the prevention of posterior capsule opacification (PCO) in a closed capsular bag technique.

SETTING

Ophthalmic Biophysics Center, Bascom Palmer Eye Institute, University of Miami School of Medicine, Miami, Florida, USA.

METHODS

Lens material was removed using phacoaspiration or phacoemulsification through a microcapsulorhexis according to the hardness of the crystalline lens correlated with the weight and age of the rabbits. A mixture of an ophthalmic viscosurgical device (sodium hyaluronate 1.4% [SHA]) and a drug was injected into the empty capsular bag, allowed to remain inside for 3 minutes, and removed. The capsular bag was rinsed with balanced salt solution (BSS) and refilled with SHA. In a group of rabbits, the capsulorhexis was sealed with a minicapsulorhexis valve (MCV). Rabbits were treated with 1 of the following: SHA (control), BSS, mitomycin-C (MMC, 0.2 mg/mL), ethylenediaminetetraacetic acid (EDTA) (10 mM and 15 mM), 5-fluorouracil (5-FU, 33 mg/mL), acetic acid (3%, 0.3%, and 0.003%), and distilled water.

RESULTS

Upon completion of the study, the control and treated eyes had PCO and new lens material (not residual). Anterior capsule proliferation was observed in eyes treated with 5-FU. The order of PCO appearance (earliest to latest) was as follows: 15 mM EDTA, SHA, MMC, acetic acid 0.3%, acetic acid 3%, BSS, distilled water (small animals; no MCV), acetic acid 0.003%, 5-FU, 10 mM EDTA, and distilled water (large animals; MCV). The earliest appearance was day 1 postoperatively and the latest, day 47.

CONCLUSIONS

Distilled water and 10 mM EDTA treatments were the most efficient in retarding the appearance of PCO.

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.

Inhibition of human lens epithelial B-3 cell proliferation by adenovirus-mediated transfer of antisense c-myc construct

PURPOSE

To investigate the effects of adenovirus-mediated transfer of antisense c-myc construct on human lens epithelial B-3 (HLE B-3) cell proliferation, apoptosis and cell cycle.

METHODS

HLE B-3 cell cultures were transduced with replication-defective adenovirus bearing either a nuclear-targeted beta-galactosidase (Ad-lacZ) or an antisense c-myc construct (Ad-AS-myc). The presence of beta-galactosidase activity in the transduced cultures was detected by immunohistochemical X-Gal staining, while c-myc mRNA and protein expression levels were evaluated by RT-PCR and Western blot analysis. HLE B-3 cell proliferation within 96 h after the transduction was analyzed by cell counting and MTT colorimetric assay. Apoptosis and cell cycle of the HLE-B3 cells were examined by flow-cytometric analysis.

RESULTS

The mean transduction efficiency was 80% for HLE B-3 cells. Downregulation of c-myc mRNA and protein expression was noticed at 48, 96 and 144 h after the transduction with Ad-AS-myc. Cytostatic effects of Ad-AS-myc in HLE B-3 cells were obvious within 96 h after the transduction. An increased incidence of apoptosis and G1-phase arrest was identified in the Ad-AS-myc-transduced HLE B-3 cells.

CONCLUSIONS

HLE B-3 cells were successfully transduced with adenovirus-mediated antisense c-myc construct. Ad-AS-myc transduction could significantly inhibit cell proliferation and induce cell apoptosis and G1-phase arrest in HLE B-3 cells. It may provide a novel approach for prevention of posterior capsular opacification.

Methods of assessment of patients for Nd:YAG laser capsulotomy that correlate with final visual improvement

BACKGROUND

This paper attempts to clarify the usefulness of various simple pre-operative measures in estimating the potential for a visually successful capsulotomy.

METHODS

24 patients attending for capsulotomy had pre-operative measures of glare with BAT tester, visibility of posterior pole and grading of posterior capsular pearls and fibrosis seen at slit lamp. Visual function was measured before and after standardised capsulotomy. Correlations of the various preoperative measures with eventual visual function improvements were calculated.

RESULTS

Pearls at slit lamp and poor posterior pole visualisation were all correlated with improvements in visual acuity and contrast sensitivity after capsulotomy. Amount of fibrosis visible at slit lamp and glare assessment were not correlated with vision improvements after laser.

CONCLUSION

Of the various measures that are taken prior to Nd : YAG capsulotomy, some correlate with eventual visual improvement but for others no clinical utility was found. Practitioners should note these findings as they are especially of use in more questionable or high-risk cases to help determine whether referral for PCO treatment by Nd: YAG capsulotomy is likely to benefit the patient.

Analysis of cytoskeletal proteins in posterior capsule opacification after implantation of acrylic and hydrogel intraocular lenses

PURPOSE

To analyze selected lens cytoskeletal proteins in posterior capsule opacification (PCO) 2 weeks after intraocular lens (IOL) implantation in rabbits.

SETTING

Department of Ophthalmology, Dokkyo University School of Medicine, Tochigi, Japan.

METHOD

Eight 10-week-old albino rabbits were prepared and anesthetized for phacoemulsification and aspiration of the crystalline lens and implantation of an acrylic or a hydrogel IOL. Two weeks postoperatively, the rabbits were killed and the IOLs removed for immunohistochemistry. Deparaffinized tissue sections were processed with antibodies against alpha-smooth muscle actin (alpha-SMA) and beta-crystallin to observe the types of PCO with the 2 IOL types. The proteins in the PCO tissue and the normal lens were homogenized, centrifuged, and analyzed using SDS-polyacrylamide gel electrophoresis (SDS-PAGE) densitometric analysis and Western immunoblotting for actin and vimentin.

RESULTS

Immunohistochemistry demonstrated a fibroblastic cell type expressing alpha-SMA and partial regeneration of epithelial cells, resulting in a lenticular structure that stained irregularly for beta-crystallin. The immunoreactivity of fibroblast-like cells to beta-crystallin appeared weaker than that of the regenerated lenticular structure. SDS-PAGE showed variability in the content of cytoskeletal proteins in the insoluble fractions of the PCO. Degradation of the cytoskeletal components was greater with the acrylic IOL than with the hydrogel IOL.

CONCLUSION

Cytoskeletal proteins expressed during the formation of PCO and IOL implantation may have potential as therapeutic target proteins to improve the biocompatibility of IOLs.

In vitro model for the study of human posterior capsule opacification

PURPOSE

To develop and evaluate a model for the organ culture of human lens capsules that reduces problems inherent in preexisting models for the study of in vitro posterior capsule opacification (PCO).

METHODS

Human lenses (N = 110) were isolated from donor eyes and supported externally within a lens holder system by medical-grade cyanoacrylate glue, allowing visualization of the entire capsular bag. After capsulorhexis and lens extraction were performed, the capsule specimens were maintained at physiological conditions for up to 4 weeks. The area of lens epithelial cell (LEC) coverage over the posterior capsule surface was determined objectively on a daily basis using a graticule. Lens epithelial cell behavior was correlated with clinical data and other in vitro PCO models.

RESULTS

Cyanoacrylate glue did not appear to be toxic to LECs at the concentration used. The amount of viable epithelium after nuclear extraction was dependent on the age and postmortem time of the specimen. Viable LEC cultures were obtained from eyes up to 9 days postmortem. The time from death to culture or from enucleation to culture did not influence LEC viability if it was fewer than 5 days. The LEC proliferation rates and confluence times were age dependent and correlated closely between pairs of eyes.

CONCLUSIONS

Results show that the lens holder model is a more physiological method for supporting the capsule and is a robust, reproducible system for the study of LEC migration and proliferation. It allows visualization within the entire capsular bag. Intraocular lenses can be implanted in this system in a way that more closely resembles the in vivo scenario. This model can be used to evaluate therapeutic measures to prevent PCO.

The effect of capsulorhexis size on development of posterior capsule opacification: small (4.5 to 5.0 mm) versus large (6.0 to 7.0 mm)

PURPOSE

The most common surgically related cause of reduced vision after extracapsular cataract extraction is posterior capsule opacification (PCO), which occurs in up to 50% of eyes following cataract extraction. This study examined whether small capsulorhexes of 4.5 to 5.0 mm, which lie completely on the 5.5 mm intraocular lens (IOL), and large capsulorhexes of 6.0 to 7.0 mm, which lie completely off the lens optic, are effective in preventing PCO development.

METHODS

In this prospective study, 496 eyes of 367 patients underwent standardized phacoemulsification with capsulorhexis and capsular bag foldable acrylic IOL implantation. The patients were randomly assigned to receive either a small capsulorhexis of 4.5 to 5 mm to lie completely on the IOL optic or a large capsulorhexis of 6 to 7 mm to lie completely off the lens optic. Retroillumination photographs were taken at 6 months and then yearly.

RESULTS

Throughout the follow-up, there was less PCO in the small capsulorhexis group than in the large capsulorhexis group. CONCLUSIONS.:Small capsulorhexes were associated with less wrinkling of the posterior capsule and less PCO than were large capsulorhexes. PCO after IOL implantation has a multifactored pathogenesis. Small (4.5 to 5.0 mm) capsulorhexis and capsular bag implantation of 5.5 mm acrylic IOL are likely to reduce the PCO incidence when compared with the 6.0 to 7.0 mm capsulorhexis. The significance of the IOL optic diameter in association with the capsulorhexis size should also be documented by further studies.

Lens epithelial cells express CD95 and CD95 ligand treatment induces cell death and DNA fragmentation in vitro

PURPOSE

Despite advances in intraocular lens design and material, posterior capsule opacification remains one of the major problems in modern cataract surgery. Therefore, the use of antiproliferative agents has been advocated. CD95 ligand (CD95L, Fas, Apo-1) is a death ligand that triggers apoptosis in susceptible target cells. Apoptosis allows for the safe disposal of cells without damaging the surrounding tissue. The goal of this study was to characterize and evaluate CD95L-induced cell death in cultured lens epithelial cells (LEC).

METHODS

Expression of CD95 in untreated porcine LEC was investigated by flow cytometry. Cell death after CD95L or CD95 agonistic antibody treatment was assessed by crystal violet assay and DNA fragmentation was measured by comet assay.

RESULTS

The presence of CD95 was observed in LEC. CD95L treatment resulted in a time--and concentration-dependent killing of LEC, which was synergistically enhanced by the addition of cyclohexamide. CD95L treatment induced DNA fragmentation.

CONCLUSIONS

The present study confirms the use of apoptosis-inducing CD95L in the inhibition of LEC proliferation. Further studies are needed before clinical application of CD95L to inhibit posterior capsule opacification will be feasible.

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.

Posterior capsule opacification and Nd:YAG capsulotomy rates after implantation of silicone, hydrogel and soft acrylic intraocular lenses: a two-year follow-up study

PURPOSE

To compare the posterior capsule opacification (PCO) and neodymium:YAG (Nd:YAG) laser posterior capsulotomy rates associated with three different posterior chamber foldable intraocular lenses (IOL).

METHODS

We retrospectively evaluated the rates of PCO and Nd:YAG laser capsulotomy in 1150 eyes two years after standard phacoemulsification with a no-stitch 3.5mm clear corneal incision (CCI) and in-the-bag implantation of one of three types of IOL: 190 eyes received a one-piece round-edged hydrogel IOL (Hydroview H60M, Bausch & Lomb); 475 eyes a three-piece round-edged silicone IOL (AMO PhacoFlex SI-40NB, Allergan); 485 eyes a three-piece square-edged soft acrylic lens (AcrySof MA60MA, Alcon).

RESULTS

The PCO and Nd:YAG laser capsulotomy rates were respectively 43.15% and 20.5% in the Hydroview H60M group, 27.57% and 9.68% in the AMO PhacoFlex SI-40NB group, 10.5% and 2.47% in the AcrySof MA60MA group.

CONCLUSIONS

PCO and Nd:YAG laser capsulotomy rates were significantly higher in the Hydroview H60M group and significantly lower with the AcrySof MA60MA lenses, which combine a bioactive constitutive material with the square-edged optic design.

Bag-in-the-lens implantation of intraocular lenses

PURPOSE

To report a new intraocular lens (IOL) and an IOL implantation concept, the bag-in-the-lens implantation technique, designed to prevent posterior capsule opacification (PCO).

SETTING

The University of Antwerp, Department of Ophthalmology, Edegem, Belgium, and the Netherlands Ophthalmic Research Institute, Department of Morphology, Amsterdam, The Netherlands.

METHODS

After identical curvilinear capsulorhexes are created in both the anterior and posterior capsules, the capsules are inserted in a flange of the IOL, thus the term bag-in-the-lensas opposed to the currently used lens-in-the-bagtechnique. The IOL was implanted in an in vitro human capsular bag model and in 10 eyes of 9 patients with cataract. Lens epithelial cell (LEC) outgrowth and PCO formation were observed.

RESULTS

When both capsular blades were well stretched around the IOL optic, the in vitro capsular bag model showed LEC proliferation only within the space of the remaining lens bag. The LEC proliferation was limited, and there was no tendency toward proliferation approaching the visual axis. In all 10 eyes, the optical axis remained clear during a follow-up between 4 and 15 months.

CONCLUSIONS

This new IOL prevented LEC proliferation in vitro and seems promising in vivo. Target patients are those at risk of PCO including those with congenital cataract, uveitis, diabetes, or cataract extraction combined with vitrectomy.

Intracapsular ring sustained 5-fluorouracil delivery system for the prevention of posterior capsule opacification in rabbits: a histological study

PURPOSE

To evaluate the efficacy of an intracapsular ring releasing 5-fluorouracil (5-FU) in preventing posterior capsule opacification (PCO) in rabbit eyes.

SETTING

Center for Research on Ocular Therapeutics and Biodevices, Storm Eye Institute, Medical University of South Carolina, Charleston, South Carolina, USA, and Chu Morvan, Department d'Ophtalmologie, University of Brest, France.

METHODS

Seventeen rabbits were divided into 3 groups: Group 1, 6 rabbits (6 eyes), had phacoemulsification only (control group); Group 2, 6 rabbits (6 eyes), had phacoemulsification with implantation of an open-loop hydrogel intracapsular ring; Group 3, 5 rabbits (5 eyes), had phacoemulsification with implantation of a ring with sustained release of 0.25 microg/h of 5-FU for 9 days. All eyes were followed for 8 weeks before enucleation. Capsular bag shrinkage and the position of the intracapsular ring were assessed, and central and peripheral PCO was evaluated for intensity and area by stereomicroscopy from a posterior (Miyake-Apple) view. The residual equatorial lens epithelial cells (LECs) were counted by the same observer in histological sections. Transmission electron microscopy (TEM) of the cornea, capsular bag, and retina was done to evaluate the toxicity of 5-FU.

RESULTS

No significant difference was seen in the degree of capsular bag shrinkage in the 3 groups. The intracapsular ring was decentered in 2 eyes (1 each in Groups 2 and 3). There was a statistically significant difference (P <.05, Student t test) between Group 1 and Groups 2 and 3 in the area and intensity of central PCO. There was no difference between Groups 2 and 3 in the intensity of central PCO. No evidence of 5-FU toxicity to intraocular structures (cornea, capsular bag, and retina) was demonstrated on TEM analysis.

CONCLUSION

Implantation of an intracapsular ring may prevent central PCO after cataract surgery by mechanically blocking LEC migration toward the central visual axis. The potential pharmacological effect of 5-FU in PCO prevention was not demonstrated.

Inhibition of lens epithelial cells by Fas-specific antibody activating Fas-Fas ligand system

PURPOSE

To detect cell specific apoptosis factors, Fas and Fas ligand, and the common intracellular apoptosis modulators, interleukin-1 beta converting enzyme (ICE)-like protease (caspase 1), Bcl-2, Bcl-xL and Bax in lens epithelial cells (LEC) of human cataracts. To study the effects of Fas-stimulating monoclonal antibody on inhibition of LEC proliferation.

METHODS

Reverse-transcriptase-polymerase chain reaction (RT-PCR) was used to detect Fas, Fas ligand, caspase 1, Bcl-2, Bcl-xL and Bax, after cDNA was synthesized from the total RNA isolated from human cataractous LEC obtained by capsulotomy during cataract surgery. Fas-stimulating monoclonal antibody was added at the concentrations of 10, 30, 100, 300 and 1000 ng/ml to the incubation medium of human cataractous LEC; and the specimens were incubated for 24 h at 37 degrees C with 5% CO(2) circulation and 100% humidity. The specimens were then stained with Hoechst 33342, and the number of apoptotic cells was counted.

RESULTS

Fas, caspase 1, Bcl-2, Bcl-xL and Bax mRNA were detected by RT-PCR. Fas ligand mRNA was not detected by RT-PCR. At each concentration, Fas-stimulating monoclonal antibody significantly inhibited LEC proliferation.

CONCLUSIONS

Human cataractous LEC expressed mRNA of Fas and various modulators of apoptosis pathways. Fas-stimulating monoclonal antibody may have the potential to prevent posterior capsule opacification after cataract surgery by inhibiting LEC proliferation.

Low-dose-rate ionizing irradiation for inhibition of secondary cataract formation

INTRODUCTION

Secondary cataract formation limits visual function after cataract surgery. Various experimental methods utilizing the pharmacologic inhibition of lens epithelial cell proliferation have been proposed. However, diffusion into the anterior chamber may lead to damage of corneal endothelial cells. This study evaluated the inhibition of lens epithelial cell proliferation with a capsular bag ring, labeled with a beta-emitting radioisotope.

METHODS AND MATERIALS

In vitro studies using rabbit lens epithelial cells were performed to investigate the dose-dependent effect of irradiation. Based on these results, P-32-labeled PMMA rings were implanted into the capsular bag of NZW rabbits in vivo after phacoemulsification. Animals were examined for development of posterior capsule opacification over a period of 12 weeks following surgery. Radiation damage to the surrounding ocular tissue was subsequently analyzed in histologic sections using TUNEL assay and proliferation marker.

RESULTS

Irradiation of lens epithelial cells in vitro with >5 Gy resulted in a dose-dependent decrease in the number of cells. BrdU testing demonstrated a near complete inhibition of cell proliferation. In vivo, implantation of P-32-labeled PMMA rings led to inhibition of epithelial cell proliferation and secondary cataract formation but was not able to fully inhibit aberrant differentiation of some remaining cells. Histologic examination showed no evidence of radiation damage of the ciliary body or the corneal endothelium.

CONCLUSIONS

Low-dose beta irradiation exhibits the potential for inhibition of lens epithelial cell proliferation both in vitro and in vivo. Further investigation of various nuclides and their radiation profiles is needed to optimize the prevention of posterior capsule opacification due to epithelial cell proliferation.

Experimental studies of capsular equator rings of soft latex

PURPOSE

To determine the efficacy of wide equatorial rings of various materials in reducing posterior capsule opacification (PCO) and maintaining the circular contour of the capsular equator in a rabbit model.

SETTING

Laboratory for Intraocular Microsurgery and Implants, Goldschleger Eye Research Institute, Tel-Aviv University, Sheba Medical Center, Tel-Hashomer, Israel.

METHODS

Closed rings made of poly(methyl methacrylate), Teflon(R), polyurethane, and latex were introduced into the capsular bags of rabbit eyes after removal of the lens material. The soft latex rings were deemed the only practical rings for atraumatic implantation through a small incision. Latex rings of 2 dimensions with rectangular edges were implanted in 8 rabbits. One eye served as a control after lens removal and no ring implantation. The eyes were followed for up to 5 months and then evaluated by light microscopy.

RESULTS

Posterior capsule opacification was minimal or absent in all animals implanted with the latex rings. Mild to moderate inflammatory reaction was noted in most eyes. It was caused by the ring material or secondary to long-standing pressure on the ciliary tissue. The rings also maintained well the circular contour of the capsular bags.

CONCLUSIONS

Equatorial rings of soft latex with sharp rectangular edges were effective in minimizing PCO and maintaining the shape of the capsule after lens removal in rabbits. Soft rings made of a biocompatible material may be effective in humans.

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.

The effect of photodynamic therapy with bacteriochlorin a on lens epithelial cells in a capsular bag model

Photodynamic therapy (PDT) with bacteriochlorin a(BCA) has proved to be a successful treatment for many cancers and to be cytocidal for different cell lines in culture. The present study aimed to investigate in vitro the potential of this treatment for killing lens epithelial cells (LECs) left in the human capsular bag after extracapsular cataract extraction (ECCE). Capsular bags were prepared from donor eyes using an ECCE procedure and incubated in various concentrations of bacteriochlorin a(1.6-50 microg ml(-1)) during various incubation periods (2-10 min). Subsequently, the capsules were illuminated during various exposure times (2-15 min) with a diode laser (wavelength 760 nm). After treatment, the capsular bags were cultured for 7 days in Eagle's minimal essential medium supplemented with 2% fetal calf serum. The specimens were fixed in glutaraldehyde/paraformaldehyde and examined with routine light microscopy, Hoechst staining for DNA and transmission electron microscopy. Proliferation of LECs on the posterior capsule was assessed in flat mounts. Capsular bags receiving BCA without illumination and capsular bags receiving illumination only served as controls.BCA alone or light alone have no effect on structure and proliferative activity of LECs. At a threshold protocol of incubation in BCA at 10 microg ml(-1)for 10 min and subsequent illumination for 15 min, proliferative activity of cells is largely arrested and nearly all LECs on the capsule exhibit severe signs of apoptosis. Photodynamic therapy with bacteriochlorin a induces cell death and suppression of proliferation inlens epithelial cells and could be a promising means of prevention of posterior capsule opacification.

Adhesion of fibronectin, vitronectin, laminin, and collagen type IV to intraocular lens materials in pseudophakic human autopsy eyes. Part 2: explanted intraocular lenses

PURPOSE

To evaluate fibronectin, vitronectin, laminin, and collagen type IV adhesion to poly(methyl methacrylate) (PMMA), silicone, hydrophobic soft acrylate, and hydrogel intraocular lenses (IOLs) in human pseudophakic autopsy eyes.

SETTING

Center for Research on Ocular Therapeutics and Biodevices, Storm Eye Institute, Medical University of South Carolina, Charleston, South Carolina, USA.

METHODS

Thirty-two autopsy eyes containing PMMA, silicone, soft acrylate, or hydrogel IOLs were assessed. The IOLs were explanted from the capsular bag, and both sides of the IOLs were immunohistochemically stained for fibronectin, vitronectin, laminin, or collagen type IV. The number of cells on the IOL surfaces was counted. The capsular bag from 1 eye containing a soft acrylate IOL was examined for fibronectin and vitronectin.

RESULTS

Hydrophobic soft acrylate IOLs had significantly more fibronectin adhering to their surfaces than PMMA (P <.01) or silicone (P <.01) IOLs, as well as more vitronectin. Silicone IOLs had more collagen type IV adhesion than the other IOLs (P <.05-.06). Collective protein adhesion differed significantly between soft acrylate IOLs and PMMA and silicone IOLs, but not between PMMA and silicone IOLs.

CONCLUSIONS

The greater amount of protein on the hydrophobic soft acrylate (AcrySof(R)) IOLs seems to support an adhesive mechanism for their attachment to the capsular bag. Fibronectin and vitronectin have functional domains to bind them to lens epithelial cells and the collagenous capsule. This kind of attachment could be a true bioactive bond and may be 1 reason the PCO and neodymium:YAG capsulotomy rates are lower in eyes with a soft acrylate IOL.

Adhesion of fibronectin, vitronectin, laminin, and collagen type IV to intraocular lens materials in pseudophakic human autopsy eyes. Part 1: histological sections

PURPOSE

To evaluate fibronectin, vitronectin, laminin, and collagen type IV adhesion to poly(methyl methacrylate) (PMMA), silicone, hydrophobic soft acrylate, and hydrogel intraocular lenses (IOLs) in pseudophakic human autopsy eyes.

SETTING

Center for Research on Ocular Therapeutics and Biodevices, Storm Eye Institute, Medical University of South Carolina, Charleston, South Carolina, USA.

METHODS

Thirty-eight autopsy eyes containing PMMA, silicone, hydrophobic acrylate, or hydrogel IOLs were assessed. Histological sections were prepared from each eye, and immunohistochemical analyses were performed for fibronectin, vitronectin, laminin, and collagen type IV. One hundred fifty-two specimens were analyzed.

RESULTS

A sandwich-like structure (anterior or posterior capsule/fibronectin/1 cell layer/fibronectin/IOL surface) was seen in 12 of 14 autopsy eyes with soft acrylate IOLs, 3 of 10 with a PMMA IOL (P =.0094), 1 of 10 with a silicone IOL (P =.0022), and 0 of 4 with a hydrogel IOL (P =. 0041). The thicker fibrocellular tissue on the inner surface of the anterior or posterior capsule that was in contact with silicone IOLs was lined with collagen type IV. Vitronectin and laminin were not found at the fibrocellular tissue-IOL interface in any specimen.

CONCLUSIONS

This study seems to confirm the sandwich theory of posterior capsule opacification in eyes with an IOL and suggests that fibronectin may be the major extracellular protein responsible for the attachment of hydrophobic soft acrylate (AcrySof(R)) IOLs to the capsular bag. This may represent a true bioactive bond between the IOL and lens epithelial cells or between the IOL and the capsular bag and may be one reason the PCO and neodymium:YAG capsulotomy rates are lower in eyes with a soft acrylate IOL.

Quantitative measurement of the PCCC area in the postoperative period

BACKGROUND/AIMS

The major complication of extracapsular cataract extraction (ECCE) is posterior capsule opacification (PCO). Posterior continuous circular capsulorhexis (PCCC) seems to be very promising in preventing PCO. This study was aimed at determining if the PCCC area changes as a function of time and if pearl formation could influence it.

METHODS

24 eyes of 23 patients underwent ECCE with PCCC. Retroillumination photographs were taken at 6 months and then yearly. To measure the PCCC area, the computerised program EPCO (evaluation of posterior capsule opacification) was used. The ratio of the PCCC area in relation to the IOL surface was calculated for the different time stages and the presence of pearl formation was noted. Firstly, proportional changes in diameter were compared in PCCC areas measured after 6 months and after 1 year (group I, n=13) and after 1 year and 2 years (group II, n=14). Secondly, PCCC areas were compared between two time stages in patients with (group III, n=19) and without pearl formation (group IV, n=8).

RESULTS

No statistically significant difference was found in diameter change in either group. The PCCC area remains stabile between 6 months to 1 year and 1 year to 2 years. No differences are found between eyes with or without pearl formation.

CONCLUSIONS

The PCCC area remains stable as a function of time and is not influenced by pearl formation.

Comparative evaluation of plate haptic lenses with smaller and larger positioning holes

PURPOSE

To evaluate the visual outcome, intraoperative problems and postoperative complications of plate haptic intraocular lenses with smaller foot plate positioning holes and larger holes.

METHODS

Fifty eyes of 50 patients underwent clear corneal phacoemulsification with implantation of either small hole plate haptics (25 eyes) or large hole plate haptic lenses (25 eyes). The intraoperative complications were noted and the postoperative parameters were evaluated on the first day, 1 week, 1 month, 3 months, 6 months and 12 months. These included the best corrected visual acuities, intraocular lens (IOL) decentring, diameter of anterior capsulorhexis and posterior capsule opacification.

RESULTS

The mean duration of follow-up was 14.8+/-2.1 months in the group with the small foot plate positioning holes (Chiron C10UB) lens and 15.6+/-3.2 months in the group with the large feet plate positioning holes (Chiron C11UB) lens. The was no significant difference in the visual acuities of the two groups. The mean IOL decentring was 0.42+/-0.28 mm in the C10UB lenses and 0.24+/-0.10 mm in the C11UB lenses (P = 0.05). The mean diameter of the anterior capsulorhexis was 4.68+/-0.23 mm in the former, while it was 4.21+/-0.68 mm in the latter (P = 0.0027). The posterior capsule opacification was significantly increased in the C11UB group (P = 0.0298). Neodymium : yttrium aluminium garnet (Nd: YAG) laser capsulotomy was required in 8% of the C10UB group, compared to 28% in the C11UB group.

CONCLUSION

Results are similar with the two types of plate haptic lenses. The lenses with larger holes have a significantly higher posterior capsule opacification and more anterior capsulorhexis contracture, although the IOL decentring is less with these lenses.

Adhesion of soluble fibronectin, laminin, and collagen type IV to intraocular lens materials

PURPOSE

To evaluate soluble fibronectin, laminin, and collagen IV adhesion to poly(methyl methacrylate) (PMMA), heparin-surface-modified (HSM) PMMA, silicone, acrylate, and hydrogel intraocular lenses (IOLs).

SETTING

Department of Medical Biochemistry, University of Oulu, Oulu, Finland.

METHODS

Seventy-five IOLs were incubated for 24 hours at 37 degrees C with radioactive iodine labeled soluble fibronectin, laminin, or collagen type IV. Twenty-five IOLs were analyzed for each protein, 5 of each type. The amount of absorbed protein was measured with a gamma counter and expressed as counts per minute (cpm).

RESULTS

Fibronectin bound best to the acrylate IOL; the differences between the acrylate and the other materials, except PMMA, were significant (P < .01 to .001; PMMA P = .31). Although significantly more laminin bound to acrylate than to PMMA, HSM PMMA, or silicone (P < .05 to .001), hydrogel had the highest overall binding of this protein (P < .001 to .0001). Hydrogel also had significantly higher binding of type IV collagen than the other IOLs (P < .01 to .0001).

CONCLUSIONS

It can be hypothesized that if an IOL has more fibronectin bound to it, the IOL can also attach to the capsule better as it consists mainly of collagen. The stronger binding of fibronectin and laminin to acrylate IOLs could be an explanation for the better adhesion of the acrylate IOL to the anterior and posterior capsules and thus for the lower rate of posterior capsule opacification.

Effect of tranilast eyedrops in preventing posterior capsule opacification: preliminary report

PURPOSE

To evaluate the effect of tranilast eyedrops in preventing fibrous opacification of the posterior lens capsule after cataract extraction and intraocular lens (IOL) implantation.

SETTING

The Second Department of Ophthalmology, Toho University School of Medicine, Tokyo, and Shohzankai Medical Foundation, Miyake Eye Hospital, Nagoya, Japan.

METHODS

This study comprised eyes having continuous curvilinear capsulorhexis and phacoemulsification/aspiration followed by implantation of a posterior chamber IOL in the capsular bag. In this prospective, randomized, controlled, and double-masked trial, tranilast 0.5% (Rizaben) eyedrops (15 eyes) or its placebo eyedrops (20 eyes) were given 4 times a day for 3 months after surgery. An anterior eye segment analysis system (EAS 1000, Nidek Co., Ltd.) was used to evaluate the degree of fibrous posterior capsule opacification (PCO) 1 week and 1 and 3 months after surgery.

RESULTS

The mean PCO density in the tranilast group was 17.1 cct +/- 4.6 (SD), 20.0 +/- 3.6 cct, and 23.0 +/- 7.7 cct (cct = computer compatible tape) at 1 week and 1 and 3 months, respectively. In the control group, it was 18.2 +/- 5.3, 30.2 +/- 7.8, and 38.4 +/- 8.0 cct, respectively. There was a significant difference in the 1 and 3 month findings between the 2 groups (P < .001).

CONCLUSION

Tranilast was effective in preventing fibrous PCO at an early postoperative stage. The possible mechanisms of its effect may be prevention of collagen synthesis by minimizing transforming growth factor type beta released during lens epithelial cell metaplasia.

Phacoemulsification and modern cataract surgery

The techniques and results of cataract surgery have changed dramatically during the past three decades. In the USA, we have moved from intracapsular cataract extraction as the preferred technique to almost exclusively extracapsular techniques. Smaller incisions have become the standard, with phacoemulsification now being the method of choice for most surgeons. Along with these advances have come improved intraocular lens materials and designs, especially well suited for use with smaller incisions. Phacoemulsification as a method to remove the cataractous lens was first proposed more than 20 years ago. Advances in techniques and equipment have led to a dramatic increase in the popularity of phacoemulsification with increased safety and efficiency. Viscoelastic agents have been developed synchronously with modern phacoemulsification techniques, playing an integral role in the success of this new technology. Improved surgical techniques for removing the anterior lens capsule have decreased the incidence of both intraoperative and postoperative capsular complications. Nucleus removal, formerly performed primarily in the anterior chamber, is now performed in the posterior chamber, decreasing damage to the corneal endothelium. Improved wound construction allows many wounds to be left unsutured, and smaller wounds allow shorter recovery time and greater intraoperative control and safety. Intraocular lenses can have smaller optic sizes and still maintain accurate centration. Foldable intraocular lenses can take advantage of the smaller incision, even further shortening the time to visual recovery. Continual evolution of this technology promises to further improve patient outcomes after cataract surgery.

Update on fixation of rigid and foldable posterior chamber intraocular lenses. Part II: Choosing the correct haptic fixation and intraocular lens design to help eradicate posterior capsule opacification

PURPOSE

Posterior capsule opacification (PCO) is one of the most common complications of cataract surgery, and there is an urgent need to reduce its incidence. Its main treatment, neodymium:YAG (Nd:YAG) laser posterior capsulotomy, may be associated with significant morbidity and is expensive. In this study, the authors ascertain the effect of posterior chamber intraocular lens (PC-IOL) fixation and various IOL designs (rigid polymethyl methacrylate [PMMA] optic and small-incision foldable designs) on the pathogenesis of PCO.

DESIGN

Prospective analysis of pseudophakic eyes obtained postmortem.

PARTICIPANTS

A total of 3493 eyes with PC-IOLs obtained postmortem and received between 1984 and 1998.

METHODS

Miyake-Apple posterior photographic technique.

MAIN OUTCOME MEASURES

Peripheral Soemmering's ring, central PCO in the visual axis, and eyes that have had Nd:YAG laser posterior capsulotomy were analyzed and scored, and these findings were correlated with the type of fixation and IOL design.

RESULTS

The degree of formation of peripheral Soemmering's ring was not influenced by IOL fixation. The acrylic design revealed relatively low Soemmering's ring scores. In contrast, central PCO and Nd:YAG laser capsulotomy scores were consistently influenced by fixation. The scores were significantly lower in eyes with in-the-bag fixation. The bag-bag fixated acrylic-PMMA design and the three modern silicone IOL designs analyzed in this study had less central PCO and lower posterior capsulotomy scores than did the PMMA IOLs.

CONCLUSIONS

The formation of peripheral PCO (the Soemmering's ring), the precursor of clinically significant, vision-threatening PCO, is not significantly influenced by the haptic fixation pattern. It is much more dependent on the quality and thoroughness of surgical cortical cleanup. Reduction of Soemmering's ring is an important goal because the retained regenerative cortical cells within this lesion are the cells of origin of PCO. The acrylic IOL design was associated with a lessor amount of peripheral Soemmering's ring as compared with all other designs. In sharp contrast to peripheral PCO, fixation of the IOL was a highly significant factor affecting the formation and quantity of central PCO-the clinically significant opacity behind the IOL optic, measured in this series either by scoring an intact retro-optical membrane or by documenting the presence of a Nd:YAG laser posterior capsulotomy orifice. The quantity of central PCO was consistently much lower in eyes with in-the-bag fixated IOLs compared with lenses with one or both haptics out of the bag. This is best explained by the fact that secure in-the-bag fixation positions the IOL optic in the best possible position to create a barrier effect. The lowest PCO rates were generally noted with the acrylic and modern silicone IOL designs.

Posterior capsule opacification. Part 1: Experimental investigations

Posterior capsule opacification (PCO) is the most frequent complication associated with decreased vision after cataract surgery. Previous methods of preventing PCO have not proven to be practical, effective, and safe for routine clinical procedure, but some novel concepts and methods have recently been developed. This 2-part review looks at clinical and experimental investigations of PCO, focusing on developments since 1992. Clinical aspects will be presented in a later issue. This paper addresses (1) in vitro models for PCO research; (2) pathophysiology and molecular biology of lens epithelial cells (LECs); (3) prevention of PCO. Of special interest are methods of culturing human LECs obtained by capsulotomy during cataract surgery, including those obtained with an intact capsular bag, to provide an in vitro model for investigating the pathophysiology of LECs; the effect of a sharp bend in the lens capsule that induces contact inhibition of migrating LECs; more specific inhibition of migrating LECs using an immunotoxin, b-FGF-saporin, or EDTA and RGD-peptides.

Reproducibility of posterior capsule opacification measurement using Scheimpflug videophotography

PURPOSE

To examine the intraobserver and interobserver reproducibility in measuring posterior capsule opacification (PCO) using a Scheimpflug videophotography system.

SETTING

Hayashi Eye Hospital, Fukuoka, Japan.

METHOD

Twenty eyes with PCO and 10 without PCO had 5 independent measurements 15 minutes apart performed by 3 observers. The eyes without PCO were selected within 1 week after surgery. Intraobserver and interobserver reproducibility were evaluated using the coefficient of variation and intraclass correlation coefficient.

RESULTS

The median coefficients of variation of the 3 observers were 11.6%, 11.3%, and 9.8%, respectively, which indicates an acceptably low observer variability. The intraobserver correlation coefficients of the 3 observers were all more than 0.95, and the interobserver correlation coefficient was 0.976, which indicates excellent reproducibility.

CONCLUSION

The results of intraobserver and interobserver reproducibility of PCO measurement using the Scheimpflug videophotography system indicate it would be effective for use in research and clinical management of PCO.

Decrease of capsular opacification with adjunctive mitomycin C in combined glaucoma and cataract surgery

OBJECTIVE

The authors investigated the incidence of capsular opacification requiring YAG capsulotomy after primary trabeculectomy combined with phacoemulsification and implantation of all polymethylmethacrylate intraocular lenses.

DESIGN

A prospective randomized study.

PARTICIPANTS

One hundred seventy-four eyes of 174 nonselected patients with primary open-angle glaucoma (POAG) were randomized to either no adjunctive mitomycin C (MMC) control group of 93 eyes of 93 patients) or adjunctive subconjunctival MMC (MMC group of 81 eyes of 81 patients) during the primary glaucoma triple procedure (PGTP).

INTERVENTION

Primary glaucoma triple procedure with and without MMC and YAG laser capsulotomy for posterior capsular opacification (PCO) was performed.

MAIN OUTCOME MEASURES

The incidences of YAG capsulotomy for PCO were compared between the control and MMC groups and also between the control group and the MMC subgroups (1 minute, 3 minutes, and 5 minutes of MMC application) using Kaplan-Meier analysis with Mantel-Cox log-rank test. Cox proportional hazard regression analysis also was performed to identify significant factors affecting capsular opacification.

RESULTS

The control and MMC groups were similar in preoperative characteristics. However, the probability of PCO requiring YAG capsulotomy was significantly lower in the MMC group than in the control group (P = 0.004). Among the MMC subgroups, MMC application for 3 minutes was most effective and significant when compared with that of the control group (P = 0.002). Although not as significant as the intraoperative use of MMC (P = 0.002), old age (P = 0.026) and presence of diabetes mellitus (P = 0.035) were also identified as significant beneficial factors for decreasing the incidence of YAG capsulotomy for PCO in Cox proportional hazard regression analysis.

CONCLUSION

Intraoperative subconjunctival MMC application during combined glaucoma and cataract surgery has a beneficial effect of inhibiting PCO after combined surgery in patients with POAG. Thus, after intraoperative subconjunctival application of MMC at the concentration of 0.5 mg/ml for 3 minutes, the aqueous MMC level must have been great enough to inhibit the lens epithelial cell proliferation to result in a long-term decrease in PCO.

In vivo quantitative measurement of posterior capsule opacification after extracapsular cataract surgery

PURPOSE

To introduce a new in vivo quantitative measurement of posterior capsule opacification (PCO) after extracapsular cataract surgery and also to analyze the correlation between opacification density and the patient's visual acuity.

METHODS

Prospectively, the opacification density value in the central 3-mm portion of the posterior capsule was quantitated by means of an area densitometry with the Scheimpflug photography system (EAS-1000). The EAS-1000 examination was performed on 40 eyes with clinically significant PCO both before and after undergoing Nd:YAG laser posterior capsulotomy, and on 10 eyes without PCO. The correlation between the opacification density value and the visual acuity was analyzed with a linear regression analysis.

RESULTS

The mean opacification density values +/- SD were 48.8 +/- 29.5 computer-compatible tapes (CCT) steps in the PCO group before capsulotomy, 15.5 +/- 7.8 CCT steps in the PCO group after capsulotomy, and 12.9 +/- 4.9 CCT steps in the non-PCO group. The mean opacification density value in the PCO group before capsulotomy was significantly greater than that in the PCO group after capsulotomy or than that of the non-PCO group. A linear regression analysis determined that the opacification density value also correlated well with the visual acuity (R2 = .808).

CONCLUSIONS

We have established a new in vivo quantitative measurement of PCO. Because the opacification density value obtained by this measurement correlated well with the patient's visual acuity, we consider this measurement to be useful in both the research and clinical management of PCO.