Mitomycin against posterior capsular opacification: an experimental study in rabbits

Microfluidics-based PLGA nanoparticles of ratiometric multidrug: From encapsulation and release rates to cytotoxicity in human lens epithelial cells

Multidrug nanomedicine is an effective therapeutic approach for the treatment of chronic diseases and cancers. However, co-encapsulation and release of drug combination at a fixed ratio by nanoparticles, particularly for long acting ocular formulations, remains challenging. Herein, poly (lactic-co-glycolic acid) nanoparticles ratiometrically co-encapsulating hydrophilic dual drugs, mitomycin C and doxorubicin, was obtained (D/M PLGANPs) by combining microfluidics and the Design of Experiments approaches. The formulation variable of lactide-to-glycolide ratios (L/G 50:50, 75:15 and 85:15) was used to achieve fast, medium and slow drug release rates of D/M PLGANPs. The dissolution of D/M PLGANPs in simulated intraocular fluid exhibited sustained release of dual drugs at the fixed ratio over 7 days, and analysis using the Korsmeyer-Peppas model showed mechanism of drug release to be governed by diffusion. More importantly, in human lens epithelial cells, the drug release rate was negatively correlated with drug potency. The slower drug release from D/M PLGANPs led to lower efficacy of drug combination against pathogenesis of cellular migration and proliferation, the key pathogenic processes of capsular opacification after cataract surgery. Compared to fast (L/G 50:50) and medium (L/G 75:15) drug release rate of D/M PLGANPs, the slow release formulation (L/G 85:15) exhibited the least cellular uptake of the dual drugs and the ratio of drug combination was not maintained intracellularly. The present study implicates the potential of using microfluidics for synthesizing polymeric nanoparticles of ratiometric drug combination and highlights the drug release rate as the critical determinant of efficacy for the long-acting nanomedicine design.

Facile multifunctional IOL surface modification via poly(PEGMA-co-GMA) grafting for posterior capsular opacification inhibition

Posterior capsule opacification (PCO) is a significant complication of intraocular lens (IOL) implantation in cataract surgery, in which the adhesion and proliferation of lens epithelial cells (LECs) on the implanted IOL surface play an important role. The surface modification of IOL to prevent LEC adhesion and proliferation is a practical way to reduce the incidence of PCO. In this study, a multifunctional binary copolymer of poly(ethylene glycol) methacrylate (PEGMA) and glycidyl methacrylate (GMA) was synthesized (poly(PEGMA-co-GMA), PPG) and chemically grafted onto the aminolyzed IOL surface, utilizing the coupling reaction of epoxy and amino groups. Doxorubicin (DOX) was subsequently immobilized on the surface coating via the reaction of epoxy and amino groups as well. Taking advantages of the hydrophilicity of the PEG segments in the copolymer coating and the anti-proliferative effects of the DOX, a multifunctional surface coating was easily established by the synthesized copolymer PPG. Such anti-proliferative drug immobilized hydrophilic coating modification may effectively reduce the cell adhesion and proliferation and thus it is hypothesized to have great potential in PCO inhibition. The synthesis of PPG was confirmed by proton nuclear magnetic resonance spectroscopy (¹H-NMR) and Fourier transform infrared spectroscopy (FTIR). The surface coating immobilization was demonstrated by X-ray photoelectron spectroscopy (XPS). The in vitro drug release profiles and the cell behaviors were also investigated to validate the multifunctional coating inhibition effect on cellular adhesion and antiproliferation. Finally, the in vivo ocular implantation was carried out on rabbit eyes to evaluate the effect of the coating modified IOL on the inhibition of postoperative PCO. It followed that such multifunctional coating modification can effectively inhibit the adhesion and proliferation of LECs and significantly reduce the incidence of PCO. All these results reveal that such PPG copolymer modification provides a facile yet effective way to inhibit PCO formation after IOL implantation.

Drug eluting and hydrophilic intraocular lens surface coating was facilely fabricated via poly(PEGMA-co-GMA) grafting. Such a multifunctional coating reduced posterior capsular opacification incidence after implantation effectively.

Modulation of matrix metalloproteinase activity by EDTA prevents posterior capsular opacification

PURPOSE

To evaluate the effect of ethylenediaminetetraacetic acid (EDTA) on posterior capsular opacification (PCO) of rabbits and to assess its effect on intraocular tissues.

METHODS

Modulation of matrix metalloproteinase (MMP) activity in the aqueous following cataract surgery in rabbits and its prevention by different doses of EDTA was determined by zymography. For evaluation of PCO, lensectomized rabbits were intracamerally injected with single dose of either 5 mg EDTA or normal saline. After one month, the degree of PCO was determined by slitlamp biomicroscopy, Miyake-Apple view, and histology of the lens capsule. The effect of EDTA on intra ocular pressure (IOP), corneal endothelial cells, and the retina was evaluated by tonometry, specular microscopy and scanning electron microscopy, and electroretinography. The concentration of EDTA in the aqueous was determined by high performance liquid chromatography (HPLC) at different time points.

RESULTS

The MMP activity was significantly increased in the aqueous of the operated eyes, and EDTA reduced the degree of increase in a dose-dependent manner. EDTA treatment significantly reduced the degree of PCO (p<0.05). Histopathology of the lens capsule showed a reduction in the number of proliferating and migrating cells as well as MMP2 expression in the EDTA-treated eyes. EDTA treatment did not change the IOP; density, morphology and ultrastructure of the corneal endothelial cells; and electroretinography (ERG). EDTA was detectable in the aqueous humor up to 72 h following a single intracameral injection.

CONCLUSIONS

EDTA reduces the degree of PCO by suppressing the MMP activity and it is not toxic to intra ocular structures at the concentration used.

Downregulation of transforming growth factor-β type II receptor prohibit epithelial-to-mesenchymal transition in lens epithelium

PURPOSE

Transforming growth factor-β (TGF-β) is considered to be essential to induce epithelial-to-mesenchymal transition (EMT) which plays central roles in wound healing in ocular fibrotic complication. The present study investigates whether small interference RNAs (siRNAs) targeting the type II receptor of TGF-β (TβRII) could be used to minimize the TGF-β action.

METHODS

TGF-β receptor type II (TβRII) specific siRNAs designed from the Nakamura human gene sequence were used to transfect the cultured lens epithelial cells (LECs). The optimal transfection of scramble siRNA-Cy3 labeled duplexes in cultured LECs were examined by laser scanning confocal microscope and flow cytometry. TβRII protein expression and transcript levels were analyzed by immunofluorescence, western blotting, and real time PCR, respectively. Western blotting was performed to examine protein expression of fibronectin and alpha-smooth muscle actin (α-SMA). Scratch assay was used to determine cell migration. Cell morphology was observed after transfection by inverted microscope.

RESULTS

The optimal transfection rate of scramble siRNA-Cy3 labeled duplexes was efficient in that nearly to 50% in cultured LECs. TβRII specific siRNAs significantly reduced the receptor transcript and protein expression in cultured LECs. The gene knockdown inhibited LECs transdifferentiation, as it abrogated the expression of fibronectin and α-SMA, and retarded cell migration on the scratch assay. In addition, after transfection with TβRII specific siRNA, the cultured LECs did not show fibroblast-like shape which was one of the feature signs of EMT. Wound scratch assays indicated that the number of cultured LECs migrated into the wounded area was significantly lower in TβRII specific siRNA treated group (12.8 ± 3.27/7.85 mm(2)), compared with normal (57.8 ± 3.06/7.85 mm(2)) and scrambled RNA transfected group (50.8 ± 3.64/7.85 mm(2); p<0.0001).

CONCLUSIONS

Our results provided additional evidence to support that TGF-β pathway was involved in the development of EMT of human posterior capsule opacification, while how TβRII was involved should be further investigated.

The effect of phosphorylated Akt inhibition on posterior capsule opacification in an ex vivo canine model

PURPOSE

To evaluate whether inhibition of phosphorylated Akt (pAkt) would reduce or prevent posterior capsule opacification (PCO) in an ex vivo canine lens capsule model.

METHODS

Normal and cataractous lenses (n=6) were evaluated for pAkt via immunohistochemistry and immunoblotting. Primary cultures of lens epithelial cells (LEC) were exposed to ultraviolet light (UV) to induce pAkt. Cultures were then incubated in 0, 2.5, 5, or 10 µM (n=6) of a novel Akt inhibitor (AR-12) for either 8 or 24 h. Cultures were harvested and pAkt expression and telomerase activity examined by immunoblotting and telomeric repeat amplification protocol (TRAP)-enzyme linked immunosorbent assay (ELISA), respectively. Lens capsules were harvested post-sham cataract surgery and exposed to 0, 2.5, 5, 7.5, or 10 μM (n=8) of AR-12 for a total of 14 days treatment. Additional lens capsules (n=6) were exposed to 10 μM of AR-12 for 1 week followed by media alone for 1 week; or exposed to media alone for 1 week followed by 10 μM of AR-12 for 1 week. Histopathology and immunohistochemical staining were performed to evaluate PCO formation. Analysis of telomerase activity on the lens capsules was performed by TRAP-ELISA.

RESULTS

pAkt protein expression was increased in clinical samples of canine cataracts compared to normal lenses. Following exposure to UV, cultures of LEC significantly (p<0.05) increased expression of pAkt and telomerase activity. Treatment with AR-12 for both 8 and 24 h following UV irradiation significantly (p<0.01) decreased pAkt expression. When UV-exposed LEC were allowed to recover in the presence of either 5.0 or 10.0 µM AR-12, there was a significant (p<0.05) decrease in telomerase activity. In the ex vivo model of PCO, within the region of the capsulorhexis, PCO inhibition was maximally achieved with 10 μM of AR-12. A significant decrease in LEC was noted on the posterior capsules containing 5.0, 7.5, and 10 μM AR-12 compared to the control capsules (p<0.01). Telomerase activity decreased in a dose-dependent manner. One week of treatment with 10 μM AR-12, immediately following capsule excision, was sufficient to inhibit PCO formation, while a delay in exposure to AR-12 after 1 week of media incubation alone did not prevent PCO formation.

CONCLUSIONS

pAkt is known to have roles in cell survival, proliferation, and migration, and this study suggests its inhibition immediately following cataract surgery may be a useful approach to prevent PCO.

Transmission electron microscopy of the rabbit posterior capsule irrigated with thapsigargin and 5-fluorouracil in a sealed-capsule irrigation device

PURPOSE

To investigate, by transmission electron microscopy (TEM), the effect on the posterior capsule of a young rabbit eye of 5-fluorouracil (5-FU) or thapsigargin in a sealed-capsule irrigation device.

SETTING

St Erik's Eye Hospital, Stockholm, Sweden.

METHODS

Clear lens extraction was performed unilaterally in eight 4-week-old rabbits. A sealed-capsule irrigation device was irrigated for 2 min with 20 ml of one of the following: balanced salt solution (BSS; n=2), thapsigargin 300 muM (n=2), 5-FU 50 mg/ml (n=2), or 5-FU 25 mg/ml (n=2). The substances were washed out for 10 s with BSS. The eyes were left aphakic. Six weeks postoperatively, the animals were killed, and the posterior capsule was extracted and fixed for TEM. As a control, we also evaluated the capsules from the two fellow eyes in the BSS group that did not undergo surgery.

RESULTS

The ultrastructure of the posterior capsule in eyes irrigated with 5-FU or thapsigargin did not differ from that in the eyes irrigated with BSS or in the eyes that did not have surgery. The membranes had the same ultrastructure with thin collagen fibres on the anterior and posterior face of the posterior capsule and an amorphic matrix.

CONCLUSION

Thapsigargin or 5-FU used in a sealed-capsule irrigation device does not seem to harm the posterior capsule, which appeared similar to when the capsule is irrigated with BSS.

Prevention of lens epithelial cell growth in vitro using mibefradil-containing PLGA micro particles

The prevention of the posterior capsule opacification is still unsolved. To interfere with proliferating cells the T-type calcium channel antagonist Mibefradil was immobilized in poly-lactic-co-glycolic-acid micro particles which were fixed at a capsular tension ring and tested in a human organ culture model as well as in human lens cells HLE-B3 in vitro. It is feasible to get a release significantly affecting cell viability and growth evaluated by MTT test and cell cycle analysis. In addition, Bionas^® sensor chips were used for time-dependent adhesion experiments in living lens cells. Interestingly, the concentration of Mibefradil which inhibited subconfluent cells is not effective in confluent cells. This is an important feature for the protection of the intact tissue in the eye.

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.

Safety of irrigation with 5-fluorouracil in a sealed-capsule irrigation device in the rabbit eye

PURPOSE

To study the safety of irrigation with 5-fluorouracil (5-FU) in the Perfect Capsule sealed-capsule irrigation device (Milvella, Ltd., Epping, Australia).

SETTING

St. Erik's Eye Hospital, Stockholm, Sweden.

METHODS

Thirty 8-week-old rabbits were divided into 4 groups. Clear lens extraction was performed and the Perfect Capsule was applied in 1 eye in Groups 1, 2 and 3. The sealed system was flushed with balanced salt solution (BSS) in Group 1, 5-FU 50 mg/mL in Group 2, and 5-FU followed by BSS in Group 3. In Group 4, the Perfect Capsule was not applied; instead, 0.2 mL of 5-FU was instilled in the capsule and left there for 30 seconds. An endothelial cell count and pachymetry were performed preoperatively and 24 hours postoperatively. At 24 or 48 hours (half of each group at each time point), the rabbits were killed and the retina and trabecular meshwork histopathologically examined. The endothelial cell count and pachymetry were compared between the Perfect Capsule eye and the control eye in Group 1.

RESULTS

There was no difference between the groups in endothelial cell count (P = .96) or pachymetry (P = .32). Histologic evaluation showed no damage from the 5-FU. The comparison between eyes in Group 1 showed that the use of the Perfect Capsule did not cause more endothelial cell loss (P = .86) or increase pachymetry more (P = .28) than in the control eye.

CONCLUSION

Irrigation with 5-FU 50 mg/mL in the sealed-capsule irrigation device was safe and caused no apparent damage to the adjacent intraocular tissues.

Long-term results of sealed capsule irrigation using distilled water to prevent posterior capsule opacification: a prospective clinical randomised trial

BACKGROUND

We investigated long-term safety and efficacy of sealed capsule irrigation (SCI) during cataract surgery to prevent posterior capsule opacification (PCO).

METHODS

One eye of each of 17 patients (mean age: 70.1+/-9.7 years) who presented with bilateral cataracts was randomly chosen for SCI treatment. After phacoemulsification, the capsular bag was vacuum sealed with the PerfectCapsule device (Milvella) followed by SCI using distilled water for two minutes. No vacuum loss occurred during irrigation. Each patient's fellow eye served as a control. One hydrophilic acrylic intraocular lens model was implanted in all eyes. Five patients had to be excluded due to deep anterior chamber, small pupil or unilateral surgery. Follow-up examinations took place one day and one, three, six, 12 and 24 months after surgery. We evaluated safety parameters, anterior capsule (AC) overlapping and PCO.

RESULTS

Postoperatively, mean best corrected visual acuity, pachymetry, endothelial cell count, intraocular pressure, AC overlapping and PCO showed no statistically significant difference between SCI and the control group (p>0.05, Wilcoxon test).

CONCLUSION

SCI is a safe procedure and enables the specific pharmacological targeting of lens epithelial cells inside the capsular bag. Using distilled water, however, it is not possible to reduce PCO development significantly. Thus, alternative substances should be evaluated.

Mitomycin: clinical applications in ophthalmic practice

Mitomycin (mitomycin C; MMC) is an antibiotic isolated from Streptomyces caespitosus. The drug is a bioreductive alkylating agent that undergoes metabolic reductive activation, and has various oxygen tension-dependent cytotoxic effects on cells, including the cross-linking of DNA. It is widely used systemically for the treatment of malignancies, and has gained popularity as topical adjunctive therapy in ocular and adnexal surgery over the past 2 decades. In ophthalmic medicine, it is principally used to inhibit the wound healing response and reduce scarring of surgically fashioned ostia. Hence, it has been used as adjunctive therapy in various ocular surgeries, such as glaucoma filtering surgeries, dacryocystorhinostomy, corneal refractive surgery and surgeries for ocular cicatrisation. In addition, it has been used as an adjunct in the surgical management of pterygia, ocular surface squamous neoplasia, primary acquired melanosis with atypia and conjunctival melanoma. In many of these surgeries and ophthalmic pathologies, MMC showed a significant beneficial effect.

[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.

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.

[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.

Quantification of posterior capsule opacification with round and sharp edge intraocular lenses

PURPOSE

To quantitatively evaluate and compare intraocular lenses (IOLs) with a round or sharp optic edge design for posterior capsule opacification (PCO).

STUDY DESIGN

Prospective comparative observational case series. PARTICIPANTS/MATERIALS: Photographs from 174 eyes were analyzed for PCO at the Department of Ophthalmology, Ruprecht-Karls-University of Heidelberg, Heidelberg, Germany.

MAIN OUTCOME MEASURES

Part I: 121 eyes of 121 patients were analyzed for quantification of PCO. IOLs evaluated were Corneal ACR6 (n = 21), Alcon Acrysof (n = 20), Allergan AR40 (n = 27), Pharmacia 811 one-piece polymethyl methacrylate (PMMA) IOL (n = 24), and Pharmacia 911A silicone IOL (n = 29). Mean follow-up was 14.01 +/- 2.81 months; mean patient age was 73.2 +/- 7.3 years. The morphologic PCO formation was evaluated for the entire optic and in the central 3-mm zone. Part II: In 53 eyes of 46 patients aged 73.4 +/- 10.8 years with an Alcon Acrysof IOL, PCO formation and capsulorrhexis/optic overlapping were analyzed 34.2 +/- 4 months after cataract surgery using EPCO Software.

RESULTS

Part I: The PCO values of the entire optic were for Corneal ACR6, 1.93 +/- 0.62; PMMA, 0.64 +/- 0.63; AR40, 0.55 +/- 0.28; Alcon Acrysof, 0.145 +/- 0.27; and 0.161 +/- 0.181 for the Pharmacia 911A IOL (P < 0.01). The PCO values of the central 3-mm zone were for Corneal ACR6, 1.64 +/- 0.96; PMMA, 0.49 +/- 0.39; AR40, 0.22 +/- 0.32; Alcon Acrysof, 0.08 +/- 0.21; and 0.06 +/- 0.11 for the Pharmacia 911A IOL (P < 0.01). Part II: Average overlapping of capsulorrhexis and Acrysof IOL optic was 40.5% +/- 12.4%. There was a significant correlation between PCO values and overlapping (r = -0.69, P < 0.001).

CONCLUSIONS

The sharp-edge IOL types (Alcon Acrysof and Pharmacia 911A silicone IOL) resulted in statistically significantly lower PCO values for analysis of the entire optic area and central 3-mm zone. There was no statistically significant difference in PCO values between the two sharp-edge optic IOLs. An overlapping of capsulorrhexis rim and the anterior IOL optic surface of more than 20% resulted in significantly lower PCO values with the Acrysof IOL.

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.

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 cell growth by induction of apoptosis: potential for prevention of posterior capsule opacification

As a model of the cell proliferation occurring in posterior capsule opacification (PCO), lens epithelial cells (LEC) from human and rabbit capsulotomies, and a rabbit LEC line (N/N1003A) were grown in Dulbecco's Minimal Essential Media (MEM) with 10% fetal calf serum. LEC were exposed to the calcium ionophore, calcimycin, and viability was assessed by trypan blue staining, growth by 3H-thymidine incorporation and apoptosis by annexin/propidium iodide staining, calcein AM/ethidium bromide staining and DNA laddering. Human capsulotomy samples were similarly exposed to calcimycin, and apoptosis assayed by calcein AM/ethidium bromide staining. Calcimycin exposure induced apoptosis in both rabbit LEC cultures and human LEC, and changes leading to apoptosis could be detected within 30 minutes of calcimycin treatment. The decrease in viability and growth in human and rabbit LEC was dose-dependent. These data support the further evaluation of apoptosis induction as a possible treatment mechanism to prevent development of PCO following primary cataract surgery in humans.

Prevention of posterior capsule opacification by intraoperative single-dose pharmacologic agents

PURPOSE

To determine whether an intraoperative single dose of dexamethasone, diclofenac, ethylenediaminetetraacetic acid (EDTA), a combination of EDTA and RGD peptide (arginine-glycin-aspartic acid sequence), or mitomycin-C (MMC) is a pharmacological means of preventing or reducing the development of posterior capsule opacification (PCO).

SETTING

Department of Ophthalmology, Celal Bayar University, School of Medicine, Manisa, and Department of Pathology, Dokur Eylül University, School of Medicine, Izmir, Turkey.

METHODS

Fifty-four rabbits were randomly divided into 6 groups. Dexamethasone (4 mg/cc), diclofenac (2.5 mg/cc), EDTA (8 mg/cc), a combination of EDTA and RGD peptide (2.5 mg/cc), or MMC (0.04 mg/cc) was given, 0.1 cc by hydrodissection and 0.9 cc into the capsular bag after phacoemulsification. The sixth group served as a control group. After 3 months, the PCO was graded clinically and the proliferation of lens epithelial cells (LECs) was evaluated histologically.

RESULTS

The drugs were significantly effective in preventing PCO compared with the control (P <.005). Dexamethasone had a weaker effect than the other drugs. In histological analysis, although monolayer LECs in the dexamethasone and diclofenac groups were observed, there was no proliferative activity on the posterior capsules in the EDTA, EDTA+RGD, and MMC groups in contrast to the multilayer cells in the control.

CONCLUSIONS

Intraoperative single-dose application of EDTA, EDTA+RGD peptide combination, and MMC significantly prevented the development of PCO in rabbit eyes. Diclofenac was less effective but also reduced PCO. Although dexamethasone did not prevent the proliferation of LECs, it decreased PCO clinically.

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.

Lens epithelial cell proliferation in human posterior capsule opacification specimens

In previous in vitro studies on capsular bags it was shown that, after a sham extracapsular cataract extraction (ECCE) on human donor eyes, lens epithelial cells (LECs) show, in the short term, a dramatically elevated mitotic activity as compared to that in the intact lens. The long term in vivo proliferation of LECs in human lenses after ECCE and intraocular lens (IOL) implantation has not been studied until now. In the present study, the mitotic activity of LECs in human post-mortem eyes with posterior capsule opacification (PCO) was investigated. Human lenses with signs of PCO were dissected from donor eyes and incubated in MEM, supplemented with fetal calf serum, for 1 day (n = 10) or 7 days (n = 9). Six additional specimens were cultured for 7 days after removal of the IOL and lens fibres. After the incubation period, mitotic activity was estimated using the BrdU procedure and the Ki67 proliferating cell marker. The mean number of BrdU-positive nuclei in the intact PCO specimens was at a level of 7.5 (day 1) and 6.5 (day 7). Removal of the IOL and the lens fibres leads to a ten-fold increase in BrdU positive cells (mean = 84.5). No correlation with donor age was found. The Ki67 observations corroborate the BrdU results. The results demonstrate that after an initial rise in proliferative activity, as shown in the capsular bag model, the mitotic activity of LECs returns to a rate comparable to that in intact cultured non-cataractous lenses. As in control lenses, removal of lens fibres significantly elevated the proliferative activity of the remaining LECs. Suppression by newly formed differentiated lens fibres in the in vivo capsular bag may be responsible for this return to control levels of mitotic activity of LECs in the PCO specimens.

Surgical prevention of posterior capsule opacification. Part 2: Enhancement of cortical cleanup by focusing on hydrodissection

PURPOSE

To experimentally analyze the role and efficacy of hydrodissection in achieving maximal cortical cleanup.

SETTING

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

METHODS

Phacoemulsification and irrigation/aspiration were performed in 10 pairs of human eyes (20 eyes) obtained postmortem. Ten eyes had previous hydrodissection and 10 eyes, no hydrodissection. The time (seconds) required for complete lens substance removal in each procedure was measured. In addition, a qualitative evaluation of difficulty of surgery was noted.

RESULTS

Phacoemulsification required 28.6% less time in eyes with previous hydrodissection than in those without. Irrigation/aspiration time was reduced by 50.9% when hydrodissection was performed. The total time of each procedure required for complete evacuation of the capsular bag was reduced by an average of 37.7% in eyes with hydrodissection. Furthermore, qualitatively the procedure was far easier, less stressful, and caused less posterior capsule stress or rupture when copious hydrodissection was performed.

CONCLUSIONS

Hydrodissection enhances the general safety and efficiency of cortical cleanup, especially at 12 o'clock. Hydrodissection is the best available, practical, immediately implementable, and inexpensive means to help remove equatorial E-cells and thus alleviate the incidence of posterior capsule opacification.

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.

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.

Immunolocalization of prolyl 4-hydroxylase subunits, alpha-smooth muscle actin, and extracellular matrix components in human lens capsules with lens implants

Lens capsules become fibrotic after the extraction of a cataract. To understand this phenomenon, we evaluated the immunolocalization of prolyl 4-hydroxylase (an enzyme involved in procollagen hydroxylation), and extracellular matrix components and cytoskeletal components in a normal human lens capsule and in others with intraocular lenses. Lens capsules containing intraocular lenses were removed from a patient with proliferative vitreoretinopathy and three with proliferative diabetic retinopathy during vitreous surgery. Two circular sections of the anterior capsules with lens epithelial cells were obtained by anterior capsulotomy during cataract surgery. In addition, a lens capsular bag was obtained immediately after phacoemulsification. The lens capsules were processed for light microscopic immunohistochemical detection of the alpha and beta subunits of prolyl 4-hydroxylase, extracellular matrix components (including collagen types, laminin and cellular fibronectin) or cytoskeletal components (such as cytokeratin, vimentin and alpha-smooth muscle actin). Monolayer lens epithelial cells were seen on the inner surface of the normal anterior capsules. Each intraocular lens was found to be fixed in the capsular bag. Light microscopic immunohistochemistry showed that these proliferating cells expressed vimentin and alpha-smooth muscle actin; in contrast, quiescent lens epithelial cells did not stain for alpha-smooth muscle actin. Marked immunostaining for subunits of prolyl 4-hydroxylase was detected in lens epithelial cells proliferating on the capsules, while no or only faint prolyl 4-hydroxylase immunoreactivity was detected in quiescent lens epithelial cells immediately after phacoemulsification. Collagen types I, III and VI and cellular fibronectin were observed diffusely in accumulated connective tissue on a capsule with an intraocular lens. Type IV collagen immunoreactivity was seen both in the capsules and in the connective tissue accumulation on the capsules. Collagen V and laminin were detected in association with cellular proliferation. Collagen VII and VIII and laminin 5 were not seen. We concluded that during wound healing of the lens capsule after cataract extraction, the lens epithelial cells that proliferate on the inner surface of the capsule transform it into a myofibroblastic phenotype, expressing prolyl 4-hydroxylase and alpha-smooth muscle actin. These proliferating cells are involved in the production of collagen on the lens capsule. This results in a postoperative fibrotic process and contraction of the lens capsule.

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.