Evaluation of daunomycin toxicity on lens epithelium in vitro

Changes in lognormal shape parameter guide design of patient-specific radiochemotherapy cocktails

Uptake of radiopharmaceuticals and chemotherapeutic drugs is nonuniform at the microscopic level. Their distributions are typically lognormal, suggesting that failure in chemotherapy and targeted radionuclide therapy may be attributable, in part, to the characteristics of this biologically ubiquitous distribution. The lognormal problem can be overcome by using cocktails of 2 or more agents, tailored such that at least 1 agent is strongly incorporated by every cell in the target population. Therefore, critical assessment of the tissue uptake of each cocktail component is warranted.

METHODS

Cellular incorporation of the α-particle-emitting radiochemical ((210)Po-citrate) and 2 anticancer drugs (daunomycin and doxorubicin) was determined using flow cytometry. The role of their lognormal distribution in clonogenic cell survival was evaluated.

RESULTS

The shape parameter of the lognormal distribution was found to be correlated to both intracellular agent concentration and cell survival. Although no difference emerged between the shape parameters for citrate within the first 2 logs of cell kill, those for daunomycin and doxorubicin changed significantly.

CONCLUSION

Changes in the value of the lognormal shape parameter and slope of the cellular drug uptake curves can be used to rapidly screen radiopharmaceuticals and other cytotoxic agents to formulate more effective cocktails for cancer therapy.

Two-photon absorption-controlled multidose drug release: a novel approach for secondary cataract treatment

Tens of millions of cataract surgeries are done every year and the number is increasing heavily. Posterior capsule opacification is the major postoperative complication with an incidence of 10 to 50% within 5 years, depending on the age of the patient. We present a novel approach for secondary cataract treatment in a noninvasive manner. Photochemically triggered drug release from a polymer enables repeated drug applications for cataract treatment years after implantation of the intraocular lens, just when needed. However, light in the visible spectral range must pass through the lens but must not induce drug release. We demonstrate that two-photon absorption photochemistry is a powerful tool to overcome this problem. With wavelengths in the visible regime, a photochemical reaction that requires energies in the UV is triggered. The high intensities needed for this process never occur in any lighting condition in daily lives, but may be easily obtained with focused laser beams routinely used in ophthalmology. The properties of the therapeutic system are specified and the function is demonstrated by in-vitro cell tests. Noninvasive multidose photochemically triggered drug release from implanted intraocular lenses carrying a drug depot may be a therapeutic as well as an economic choice to established treatments of secondary cataracts.

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.

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.

Use of a polylysine-saporin conjugate to prevent posterior capsule opacification

PURPOSE

To determine the feasibility of applying a polylysine-saporin (PLS) conjugate to the lens capsule at surgery to prevent lens epithelial cell (LEC) proliferation and posterior capsule opacification (PCO).

SETTING

Department of Research & Development, Bausch & Lomb Surgical, and Department of Ophthalmology, Saint Louis University, St. Louis, Missouri, USA.

METHODS

Fluorescein-labeled polylysine was applied to the lens capsule of rabbits after phacoemulsification and analyzed histologically to determine the extent of binding to the lens capsule and surrounding tissues. The cytotoxin saporin was conjugated to polylysine using bifunctional cross-linkers. This PLS conjugate was applied to LECs in culture and to the lens capsules of rabbits. These eyes were monitored for PCO.

RESULTS

Polylysine primarily bound to the lens capsule membranes, with little or no binding to surrounding tissues. When PLS was added to LECs in culture, it was internalized and destroyed the cells. Of 9 rabbit eyes treated with PLS during surgery, 1 remained free of PCO for the life of the animal (40 weeks), while 6 showed a delay of cortical regrowth approximately 2 to 3 times that of control eyes.

CONCLUSIONS

Polylysine bound selectively to the lens capsule membrane. The PLS conjugation resulted in a toxic agent that targeted the lens capsule and destroyed proliferating LECs. The application of a PLS conjugate during surgery may prevent 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.

Relationship between intraocular lens biomaterials and posterior capsule opacification

PURPOSE

To determine whether posterior capsule opacification (PCO) is influenced by intraocular lens (IOL) material.

SETTING

A British teaching hospital eye department.

METHODS

Ninety eyes were prospectively randomized to receive a poly(methyl methacrylate) (PMMA), silicone, or AcrySof IOL. All lenses had 6.0 mm optics and PMMA haptics. A standardized surgical protocol was performed by a single surgeon using an extracapsular technique with capsulorhexis. Patients having surgical complications were excluded and all patients had standardized medication and follow-up. Posterior capsule opacification was assessed by a digital retroillumination camera using a dedicated software program based on the analysis of texture in the image and calculated as the percentage area of opacified capsule. Data were analyzed 2 years postoperatively.

RESULTS

There was a significant difference in percentage of PCO at 2 years among the three lens types (P < .0001). The AcrySof lenses were associated with less PCO (median 11.75%) than PMMA (43.65%) and silicone (33.50%) lenses (P < .001 and P = .025, respectively). The difference between PMMA and silicone lenses was not statistically significant.

CONCLUSION

Intraocular lenses made from AcrySof were associated with a significantly reduced degree of PCO.

Transferrin in after-cataract and as a survival factor for lens epithelium

The Fe-transport protein, transferrin (Tf), is synthesized and secreted by whole lenses and cultured lens epithelial cells. Because of Tf's central role in cell growth and proliferation, its participation in lens cell proliferation following cataract extraction was explored using a rabbit model of after-cataract. Varying amounts of the central anterior lens capsule were removed (0, 35, or 80%) following extraction of the lens. The Tf content of and secretion by after-cataract lens capsular sacs containing regenerated lens tissue was determined ex vivo at 0, 3, 5, 7 and 9 weeks post-surgery. In all cases Tf content of and secretion by the lens sacs was higher than that of their contralateral controls (whole lenses). Tf secretion was up to 5-fold higher and metabolic labeling studies indicated secretion of newly synthesized Tf. The sacs contained up to 10 times the concentration of Tf as the control lenses. Human lens after-cataract capsular bags also secreted Tf. The function of Tf as a survival factor was tested on cultured lens epithelial cells. Cells cultured in serum-free medium had a survival rate of only 20-34% if the medium was changed each day. If the medium was never changed during this period, the survival rate was 43-52%, suggesting secretion of essential growth factors by these cells. Addition of 200 microg ml-1 Tf to the medium during each daily change increased survival to levels attained when the medium was not changed. Addition of Tf antibodies to the culture medium during each daily change decreased cell survival to 14%. Apparently Tf acts as a survival factor for lens epithelia and its synthesis is up-regulated in after-cataract lens sacs. These factors suggest that Tf may play an important role in the pathogenesis of lens epithelial cell proliferation and after-cataract formation following cataract surgery.

Caffeic acid phenethyl ester to inhibit posterior capsule opacification in rabbits

PURPOSE

To assess whether caffeic acid phenethyl ester (CAPE) prevents posterior capsule opacification (PCO) by suppressing the transformation of the lens epithelial cells.

SETTING

Departments of Ophthalmology, Chemistry, and Pathology, Turgut Ozal Medical Center, University of Inonu, Malatya, Turkey.

METHODS

Twenty pigmented island rabbits having phacoemulsification in their right eyes were randomized into two groups. In group 1, 10 micrograms/ml of CAPE was added to the anterior chamber irrigating solution and a 1% solution of CAPE was injected subconjunctivally for 3 weeks postoperatively. The irrigating solution in Group 2 (control) did not include CAPE. The development of PCO was assessed weekly and its density was graded by slitlamp biomicroscopy. Histologic analysis was performed 3 months after surgery.

RESULTS

Group 1 had clear capsules or minor PCO. Group 2 developed more severe PCO or complete opacification. The difference between the two groups was statistically significant (P = .04).

CONCLUSION

These preliminary results indicate that CAPE is effective in suppressing PCO in pigmented rabbits and may be beneficial in clinical use in humans because it has no documented harmful effects on normal cells.

Inhibition of migrating lens epithelial cells by blocking the adhesion molecule integrin: a preliminary report

PURPOSE

To evaluate the preventive effect of blocking integrins by sustained release of RGD peptide (arginine-glycin-aspartic acid sequence) or a combination of RGD peptide and ethylenediaminotetraacetic acid (EDTA) on lens epithelial cell (LEC) migration.

SETTING

Nishi Eye Hospital, Jinshikai Medical Foundation, Osaka, Japan.

METHOD

A polylactic-glycolic acid disk containing 4% RGD or a combination of 23% EDTA and 10% RGD was implanted in the capsular bag in five rabbit eyes following standard cataract surgery. The release rate in vitro was 4.4 microg/h for RGD peptide alone and 7.8 and 7.6 microg/h for combined EDTA and RGD peptide, respectively. The contralateral eye received a disk without agents as a control.

RESULTS

After 1 month, a slight inhibition of LEC migration onto the posterior capsule was observed histopathologically in eyes receiving RGD peptide. A significant inhibition was observed in eyes with combined EDTA and RGD.

CONCLUSIONS

Application of RGD peptide and EDTA and RGD peptide may inhibit LEC migration by inhibiting the integrins expressed on the LECs. Blocking adhesion molecules expressed on LECs may reduce posterior capsule opacification.

Heparin eyedrops to prevent posterior capsule opacification

PURPOSE

To evaluate whether heparin eyedrops prevent or reduce posterior capsule opacification (PCO) after extracapsular cataract extraction (ECCE) with intraocular lens (IOL) implantation.

SETTING

Institute of Ophthalmology, University G. d'Annunzio, Chieti, Italy.

METHODS

This 4 year, prospective, case-controlled study evaluated 200 patients who had ECCE and implantation of the same type of posterior chamber IOL. Patients were randomly assigned to receive topical heparin eyedrops postoperatively (heparin group, n = 100) or not to receive the eyedrops (control group, n = 100). Postoperative cell response, cellular precipitates on the IOL, and presence of PCO were evaluated.

RESULTS

There were no significant differences between groups in postoperative inflammation. The incidence of cellular precipitates was significantly lower in the heparin group than in the control group (P < .001). A neodymium:YAG (Nd:YAG) posterior capsulotomy was done in 7 patients in the heparin group and 14 in the control group (P = .15). During the first 24 months after surgery, the heparin group had a significantly lower incidence of Nd:YAG capsulotomy (P < .05) and fibrotic PCO (P = .02).

CONCLUSION

Topical heparin eyedrops were effective in reducing fibrotic PCO in the long term, indicating their usefulness in the postoperative management of ECCE.

Inhibition of posterior capsule opacification by an intraocular-lens-bound sustained drug delivery system: an experimental animal study and literature review

PURPOSE

To find a way to prevent or significantly reduce posterior capsule opacification (PCO) with modern phacoemulsification and in-the-bag intraocular lens (IOL) implantation.

SETTING

Department of Ophthalmology and Institute for Pharmaceutical Technology and Biopharmacy, Ruprecht-Karls-University of Heidelberg, Germany.

METHODS

We evaluated the effects of an IOL-bound sustained drug delivery system (SDDS) consisting of the carrier substance poly-DL-lactid and the drug daunorubicin or indomethacin. The system was applied to the IOL surface and implanted in rabbit eyes. At 8 weeks postoperatively, PCO wet mass was determined. Toxic and inflammatory effects were documented by histopathology.

RESULTS

The average PCO wet mass was 54.6 mg in the control group, 28.6 mg with daunorubicin, and 64.1 mg with indomethacin. Statistical analysis showed a significant reduction of PCO with daunorubicin (Mann-Whitney U-test, P = .025) and no PCO-reducing effect with indomethacin. Light microscopy of the specimens revealed mild inflammation, especially at the limbus, and some endothelial cell loss in the daunorubicin group and iris and ciliary body inflammation in the indomethacin group.

CONCLUSION

In the rabbit eye, slow release of daunorubicin reduced PCO formation by approximately 50%. It must be determined whether the endothelial side effects are specific to the rabbit species or whether the human cornea is as sensitive. The principle of the IOL-bound SDDS and the evaluation procedure can be standardized and used for systematic tests in the future.

Effect of intraocular sustained release of indomethacin on postoperative inflammation and posterior capsule opacification

PURPOSE

To assess whether the sustained release of indomethacin significantly reduces postoperative inflammation and posterior capsule opacification (PCO).

SETTING

Nishi Eye Hospital, Jinshikai Medical Foundation, Osaka, Japan.

METHODS

A 7 mm diameter, 1 mm thick polylactic-polyglycolic acid disk containing 7 mg of indomethacin was implanted in five rabbit eyes after continuous curvilinear capsulorhexis and phacoemulsification. The disk and an IOL placed above it were implanted in the capsular bag. The contralateral eyes, which served as controls, received a disk without indomethacin and the same type IOL in the same manner.

RESULTS

The indomethacin was fully released within 3 weeks in vitro, a release rate of about 14 micrograms/h. Postoperatively, aqueous flare intensity was significantly lower at days 2, 3, and 4 and at weeks 1, 2, and 3. Prostaglandin E2 was not detectable in the aqueous humor of the indomethacin-treated eyes on day 3 and at week 4. In the control eyes, mean concentration was 491 pg/ml +/- 54 (SD) and 990 +/- 243 pg/ml, respectively. Histopathological examination showed no significant decrease in PCO.

CONCLUSION

Although sustained release of indomethacin significantly decreased inflammation, it did not reduce PCO.

Inhibition of migrating lens epithelial cells by sustained release of ethylenediaminetetraacetic acid

PURPOSE

To evaluate the effect of the sustained-release of ethylenediaminetetraacetic acid (EDTA) chelating Ca++ on lens epithelial cell (LEC) migration.

SETTING

Nishi Eye Hospital, Jinshikai Medical Foundation, Osaka, Japan.

METHODS

Polylactic-glycolic acid disks containing 10% EDTA were placed in saline solution for about 2 weeks in vitro. About 60% (7 micrograms/hour) of the EDTA was released during that time. The disks with a posterior chamber intraocular lens placed above were implanted in the capsular bag in five rabbit eyes after continuous curvilinear capsulorhexis and phacoemulsification. A disk without EDTA and the same lens type were placed in the bag in the contralateral eyes, which served as controls.

RESULTS

After 2 to 3 months, opacification in the central posterior capsule was significantly reduced in all eyes that received the disk with EDTA.

CONCLUSION

The deprivation of Ca++ disrupted interaction between the posterior capsule and migrating LECs by inactivating the adhesion molecule integrin synthesized by LECs, significantly reducing LEC migration onto the posterior capsule.

Effect of indomethacin-coated posterior chamber intraocular lenses on postoperative inflammation and posterior capsule opacification

We implanted indomethacin-coated intraocular lenses (IOLs) in rabbit eyes to ascertain how the sustained release of the drug affects postoperative inflammation and posterior capsule opacification (PCO). A preoperative resolution test showed that 1% indomethacin-coated IOLs placed in balanced salt solution released a mean 14.0 +/- 0.6 micrograms of the drug within 24 hours. Postoperatively, aqueous flare intensity in eyes with 0.1% indomethacin-coated IOLs and in eyes with 1.0% indomethacin-coated IOLs was significantly less at day 2 and at days 2 and 3, respectively, than in control eyes with uncoated lenses. In another group of eyes, histopathological examination showed that those with 1.0% indomethacin-coated lenses had significantly less PCO than the contralateral control eyes with uncoated IOLs.

Daunomycin as an inhibitor of human lens epithelial cell proliferation in culture

Posterior capsule opacification is still a major complication of both extracapsular cataract extraction and phacoemulsification. We evaluated the effects of the anti-proliferative agent daunomycin on cultured human and bovine lens epithelial cell viability and proliferation. After ten minutes of exposure, low concentrations of the agent markedly inhibited the proliferation of both cell types. The calculated LD50 for the drug against human cells was 2.20 micrograms/ml and against the bovine cells was 0.38 microgram/ml. The bovine cells appeared to be slightly more susceptible to the drug's effects, although this difference was not marked. Our results indicate that daunomycin is a potent inhibitor of both human and bovine lens epithelial cells in the laboratory.

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

We investigated the effect of colchicine in a sustained drug delivery system on posterior capsule opacification (PCO) in rabbit eyes. A polymer matrix wafer, which diffused colchicine at a steady rate, was implanted in the capsular bag of 34 eyes after the lens material was removed by endocapsular phacoemulsification. Three different drug concentrations were used in the rabbit eyes, which were compared with control eyes containing the polymer matrix wafer without colchicine. The mean PCO score was highest in the control group without colchicine and increased steadily over 12 weeks. The rate of PCO formation in all eyes treated with colchicine was significantly lower than in the control group. There was no statistically significant improvement in PCO inhibition with the higher colchicine dosages. Side effects included inflammatory anterior chamber reaction and corneal and retinal complications and were most notable with the highest drug concentration. Slow release of colchicine reduces PCO formation in the rabbit. The optimal biocompatible dosage must be carefully determined and warrants further investigation.

Risk factors for posterior capsular pearling after uncomplicated extracapsular cataract extraction and plano-convex posterior chamber lens implantation

We retrospectively reviewed 542 consecutive cases of extracapsular cataract extraction with implantation of a plano-convex laser ridge posterior chamber intraocular lens. We were interested in the incidence and probability of the development of postcapsular epithelial pearling that required laser capsulotomy and the risk factors associated with it. After four years of follow-up, 21% of all cases had developed pearling. Over the same period, the probability of pearling, as determined by the Kaplan-Meier curves, was 29% with a 95% confidence interval between 22% and 36%. After one year of follow-up, the probability of pearling was 5%; after two years, 15%; after three years, 24%. Younger age (50 years or less), larger optic, and smaller IOL were identified as significant risk factors when each of these factors was analyzed separately. When all risk factors were studied together, and after applying confounding statistics, only younger age was identified as a significant risk factor (P = .003).

Posterior capsule opacification

A complication of extracapsular cataract extraction with or without posterior chamber intraocular lens (PC-IOL) implantation is posterior capsule opacification. This condition is usually secondary to a proliferation and migration of residual lens epithelial cells. Opacification may be reduced by atraumatic surgery and thorough cortical clean-up. Clinical, pathological and experimental studies have shown that use of hydrodissection, the continuous curvilinear capsulorhexis and specific IOL designs may help reduce the incidence of this complication. Capsular-fixated, one-piece all-polymethylmethacrylate PC-IOLs with a C-shaped loop configuration and a posterior convexity of the optic are effective. Polymethylmethacrylate loops that retain "memory" create a symmetric, radial stretch on the posterior capsule after in-the-bag placement, leading to a more complete contact between the posterior surface of the IOL optic and the taut capsule. This may help form a barrier against central migration of epithelial cells into the visual axis. Various pharmacological and immunological methods are being investigated but conclusive data on these modalities are not yet available.

Systematic surgical procedures to secure more stable in-the-bag intraocular lens fixation

Several conditions have to be fulfilled to retain the integrity of the capsular bag for a long period after intraocular lens fixation: (1) The anterior capsular window should be small (5 mm) and round, with no radial tears; (2) the equator of the capsular bag should be almost circular; (3) the retained capsular wall should be transparent and (4) it should have no deformity. To meet these conditions, systematization of several innovative procedures is required. The system that we propose comprises continuous circular capsulorhexis (Neuhann and Gimbel), hydrodelamination (Brint), roundel phacoemulsification (Hara and Hara), new IOL designs, and intraoperative extensive lens epithelial cell removal. A description of each procedure is presented.