Posterior Capsular Opacification Formation Research Articles

Revisiting secondary capsulotomy for posterior capsule management in pediatric cataract surgery

To evaluate the development and treatment of visual axis opacification following pediatric cataract extraction with intraocular lens placement (IOL) without primary posterior capsulotomy and anterior vitrectomy (PPC+AV). The medical records of children who underwent cataract extraction and IOL at an academic medical center were reviewed retrospectively for development of posterior capsular opacification (PCO) to identify risk factors for development of treatment-requiring posterior capsular opacification. A total of 63 eyes of 47 children 7months to 16years of age were included. The rate of PCO formation following cataract extraction without PPC+AV was 90%. Of those, 96% required a secondary capsular procedure to clear the visual axis; 55% had a clear visual axis after 1 procedure, almost exclusively with a YAG capsulotomy, and 3.5% did not require any secondary capsular procedure. Younger age was the only statistically significant characteristic associated with both PCO formation and need for more than one secondary capsular procedure. Children <3years of age had an average of 2.1 capsular procedures. Cataract extraction and IOL without PPC+AV leads to an expected high rate of PCO formation, which can be effectively managed with a secondary capsular procedure in all age groups. Leaving the posterior capsule intact at primary surgery is an option to discuss with parents to avoid a more complicated primary surgery.

RGD surface functionalization of the hydrophilic acrylic intraocular lens material to control posterior capsular opacification.

Posterior Capsular Opacification (PCO) is the capsule fibrosis developed on implanted IntraOcular Lens (IOL) by the de-differentiation of Lens Epithelial Cells (LECs) undergoing Epithelial Mesenchymal Transition (EMT). Literature has shown that the incidence of PCO is multifactorial including the patient's age or disease, surgical technique, and IOL design and material. Reports comparing hydrophilic and hydrophobic acrylic IOLs have shown that the former has more severe PCO. On the other hand, we have previously demonstrated that the adhesion of LECs is favored on hydrophobic compared to hydrophilic materials. By combining these two facts and contemporary knowledge in PCO development via the EMT pathway, we propose a biomimetically inspired strategy to promote LEC adhesion without de-differentiation to reduce the risk of PCO development. By surface grafting of a cell adhesion molecule (RGD peptide) onto the conventional hydrophilic acrylic IOL material, the surface-functionalized IOL can be used to reconstitute a capsule-LEC-IOL sandwich structure, which has been considered to prevent PCO formation in literature. Our results show that the innovative biomaterial improves LEC adhesion, while also exhibiting similar optical (light transmittance, optical bench) and mechanical (haptic compression force, IOL injection force) properties compared to the starting material. In addition, compared to the hydrophobic IOL material, our bioactive biomaterial exhibits similar abilities in LEC adhesion, morphology maintenance, and EMT biomarker expression, which is the crucial pathway to induce PCO. The in vitro assays suggest that this biomaterial has the potential to reduce the risk factor of PCO development.

Implication of Smad2 and Smad3 in Transforming Growth Factor-β-induced Posterior Capsular Opacification of Human Lens Epithelial Cells

Purpose: Transforming growth factor-β2 (TGF-β2) is a potent inducer of posterior capsular opacification (PCO), a critical Smad-dependent event. This study was conducted to investigate the contributions of Smad2 and Smad3 to PCO development based on selective over-expression of either Smad2 or Smad3.Methods: We selectively activated the TGF-β/Smad pathway in cell lines transfected with expression plasmids containing Smad2 or Smad3. These cell lines were then analyzed to determine the individual contributions of Smad2 and Smad3 to TGF-β2 treatment response in an in vitro culture of HLE B-3 cells. The effects of Smad2 and Smad3 on cell viability were assessed by MTT and flow cytometry assay. A transwell assay was used to observe the role of Smad2 and Smad3 in the migration of HLE B-3 cells. Western blotting, real-time PCR, and immunocytofluorescence staining were performed to detect the accumulation of ECM proteins and EMT in response to selective Smad2 or Smad3 activation. The presence of soluble collagen I, and fibronectin in the culture medium supernatant were detected by ELISA.Results: Selective Smad3 activation via gene transfection enhanced TGF-β2-responsive growth inhibition and apoptosis. Transwell assay results showed that TGF-β2-induced cell migration was Smad2 dependent and Smad3 independent. Analysis by Western blot, RT-PCR and ELISA demonstrated that the determinant factor in ECM secretion was Smad3 signaling rather than Smad2 signaling. Western blot and RT-PCR showed that the loss of E-Cadherin and acquisition of α-SMA, the hallmark of epithelial-mesenchymal transition (EMT), were both reliant on Smad2 signaling. Immunocytofluorescence staining confirmed the role of Smad2 in the accumulation of α-SMA.Conclusions: Smad2 and Smad3 are both necessary for the formation of PCO. The discovery of additional TGF-β2/Smad signaling mechanisms may provide potential therapeutic targets to help combat PCO.

The Role of Lumican in Ocular Disease

Lumican is keratan sulfate proteoglycan of the small leucine rich proteoglycan family. Through studies in animal models lumican has been found to be critical in maintaining corneal clarity. It maintains ordered collagen fibrils which are vital in keeping the cornea transparent. It may also be important in primary open angle glaucoma influencing aqueous outflow. Lumican deficiency in mice results in increased axial length with fibromodulin deficiency and thinner sclerae. There is evidence suggesting that this characteristic may be pertinent in humans and lumican gene polymorphisms could be related to high myopia. Lumican plays a fundamental role in inflammation and wound healing. It localises macrophages to the site of corneal injury and recruits neutrophils in lipopolysaccharide-induced keratitis in mice. It has also been shown to bind lipopolysaccharide which may be critical in inflammatory diseases such as uveitis. Lumican is also important in wound healing revealing decreased synthesis in scar tissue and mediating Fas-Fas ligand interactions. It is present in human placenta and amniotic membrane suggesting that it may ensure viable amniotic membrane grafts. Lumican may also be involved in the formation of posterior capsular opacification following cataract surgery. Research into the pivotal role of lumican in the pathogenesis of ocular disease has resulted in greater understanding of the key role which proteoglycans play in human disease.

Extracellular matrix and posterior capsular opacification

Posterior capsular opacification (PCO) is one of the major complications of modern cataract surgery.Multiple studies had demonstrated that the extracellular matrix (ECM) plays an important role in the generation and development of PCO.A variety of ECM components,including fibronectin (FN),laminin (LN),collagen,lumican,osteoponin (OPN),decorin,hyaluronic acid and vimentin,affect the biological properties of lens epithelial cells (LECs) through different mechanisms,such as regulating cell migration,adhesion and proliferation.This review focuses on the role of ECM in PCO formation in order to explore the pathogenesis of PCO and provide a potential therapeutic approach for the prevention and management of PCO. Key words: Extracellular matrix; Posterior capsular opacification; Lens epithelial cells

Growth inhibition of human lens epithelial cells by short hairpin RNA in transcription factor forkhead box E3 (FOXE3)

Posterior capsule opacification occurs mainly due to the remnant lens epithelial cell proliferation and migration after cataract surgery. The purpose of this study was to investigate whether small hairpin RNA (shRNA)-mediated gene silencing of transcription factor forkhead box E3 (FOXE3) can be employed to inhibit the expression of FOXE3 and suppress the growth in lens epithelial cells. FOXE3-targeted shRNA was transfected into a human lens epithelial cell line (HLEB-3) using Lipofectamine 2000 reagent. Quantitative PCR was used to confirm the downregulation of FOXE3 mRNA expression following infection of lens epithelial cells, and FOXE3 protein expression levels were evaluated by Western blot analysis and immunofluorescence staining. HLEB-3 cell growth after the transduction was analyzed by cell counting and MTT colorimetric assay. Cell cycle of the HLEB-3 cells was examined by flowcytometric analysis. Compared with the control groups, both mRNA and protein levels of FOXE3 expression were significantly decreased in shRNA-treated groups, and cytostatic effects were obvious within 48 h after transfection. An increased incidence of G1-phase arrest was identified in FOXE3-shRNA transfected HLEB-3 cells. shRNA-mediated gene silencing of FOXE3 could significantly inhibit cell growth and induce the G1-phase arrest in HLEB-3 cells. Formation of posterior capsular opacification might be repressed if lens epithelial cell growth ceases after the FOXE3 gene is silenced with molecular biology technology.

Posterior capsular opacification and intraocular lens surface micro-roughness characteristics: An atomic force microscopy study

ObjectiveSurface roughness parameters of various intraocular lenses (IOLs) biomaterials using atomic force microscopy (AFM) are compared. Variation, if any, in the micro-roughness properties of different IOLs made up of the same biomaterial is also explored. Retrospective analysis of posterior capsular opacification (PCO) incidence has been followed up for a period of four years post IOL implantation to evaluate the correlation of PCO formation with surface roughness of IOLs. DesignExperimental materials study. Materials and participantsSurface characteristics of 20 different IOL models were assessed using AFM. These IOL models were made up of PMMA or HEMA or acrylic hydrophobic or acrylic hydrophilic or silicone. Retrospective analysis of PCO incidence in 3629 eyes of 2656 patients implanted with the same IOL models was performed. MethodsTopological characteristics of 20 different IOLs made up of 5 different biomaterials including (i) PMMA, (ii) HEMA, (iii) acrylic hydrophobic, (iv) acrylic hydrophilic and (v) silicone were evaluated using AFM in the tapping mode. Images were acquired with a resolution of 256×256 data points per scan at a scan rate of 0.5Hz per line and a scan size of 10×10μm. Rate of PCO formation in 3629 eyes of 2656 patients implanted with the five different IOL biomaterials was retrospectively analyzed. ResultsAFM images of IOL optic surfaces showed a collection of pores, grooves, ridges and surface irregularities. Surface roughness parameters of the IOL optics were significantly different on comparing lenses of different materials. Acrylic hydrophobic IOLs had minimum surface roughness while acrylic hydrophilic IOLs showed the highest surface roughness. Different IOL models of the same biomaterial showed varied topological roughness characteristics. Retrospective analyses of PCO formation rate after IOL implantation was carried out, which revealed that rate of PCO incidence, was directly proportional to the increase in surface micro-roughness of IOLs. ConclusionsAFM is a powerful technique for the topological characterization of IOLs. Acrylic hydrophobic IOLs showed minimum surface roughness properties as well as minimum PCO incidence over a period of four years post implantation. It is, therefore, tempting to consider acrylic hydrophobic IOLs over other IOL biomaterials as the ideal biocompatible material for lowering PCO incidence. These results suggest an urgent need for manufacturers to optimize the various steps involved in the fabrication of IOLs.

Comparison of design of intraocular lens versus the material for PCO prevention.

To evaluate the influence of different intraocular lens(IOL) designs made of PMMA on posterior capsular opacification(PCO) and compare with foldable designs. Phacoemulsification and IOL implantation was done in one eye of 24 New Zealand White rabbits, with IOL of two different designs (Square edged or round edge) and two different materials(PMMA or HEMA). After three months, the animals were sacrificed and enucleated. Evaluation of PCO included posterior view, migration of anterior capsular epithelial cells to the posterior capsule following epithelial-mesenchymal transition were assessed by staining the histological sections of posterior capsule by hematoxylin-eosin(HE) and Periodic acid- Schiff (PAS). The IOLs were extracted and stained with HE to evaluate the presence of adherent cells on the lens surface. PCO was highest with round edged rigid lens. There was no significant difference in the PCO between the square edged PMMA and square edged foldable lens. It is the design of the IOL not the material that offers protection on PCO formation.

Cytoskeletal drugs prevent posterior capsular opacification in human lens capsule in vitro

To determine whether the cytoskeletal drugs H-7 and Latrunculin B (LAT-B) inhibit posterior capsular opacification (PCO) in the cultured human lens capsular bag. Following extracapsular cataract (lens) extraction in human donor eyes, the capsular bag was prepared and cultured by standard techniques. Forty-eight capsular bags were studied, of which 13 were treated with H-7 (50, 100 or 300μM), 12 with 1% BSS (vehicle of H-7), 11 with LAT-B (2, 5 or 10μM), and 12 with 0.25% DMSO (vehicle of LAT-B). Forty out of the 48 capsular bags were from paired eyes of 20 donors, with one bag being treated with H-7/LAT-B and the other with BSS/DMSO for each pair, including 20 for the H-7-BSS protocol and 20 for the LAT-B-DMSO protocol. The medium with the cytoskeletal drug/vehicle was replaced every 3-4days for 4weeks. PCO was assessed daily using inverted phase-contrast microscopy, and scored on a 4-point scale. In all cultures with BSS or DMSO, residual lens epithelial cells (LECs) on the anterior capsule migrated to and proliferated on the posterior capsule by 3-7days, and apparent LEC growth on the posterior capsule with severe capsular wrinkling (PCO Grade 3) was seen by 2-3weeks. When treated continuously with H-7 or LAT-B, the migration and proliferation of LECs and the capsular wrinkling were inhibited in a dose-dependent manner, with the inhibition being complete (PCO Grade 0) in the 300μM H-7 (n = 8, p < 0.001) or 10μM LAT-B culture (n = 3, p = 0.002). H-7 and LAT-B dose-dependently inhibited PCO formation in the cultured human lens capsular bags, suggesting that cytoskeletal drugs might prevent PCO formation after surgery in the human eye.

Comparison of Posterior Capsular Opacification between a Combined Procedure and a Sequential Procedure of Pars Plana Vitrectomy and Cataract Surgery

Purpose: To compare posterior capsular opacification (PCO) between a combined procedure and a sequential procedure of pars plana vitrectomy (PPV) and cataract surgery (CS). Methods: The medical records of 89 eyes of 85 patients who underwent PPV and CS were retrospectively reviewed. There were 56 eyes of 52 patients with a combined PPV and CS (the combined surgery group), and 33 eyes of 33 patients with CS in a previously vitrectomized eye (the sequential surgery group). The control group was comprised of 130 eyes of 102 patients who underwent CS alone. All patients were followed up for at least 1 year after CS. The major outcome measures were the PCO rate and the interval between CS and PCO formation. There were no significant differences in age and the incidence of diabetes among the 3 groups. Results: The PCO rate checked at 1 year after CS was 12.5% (7/56) in the combined surgery group, 24.2% (8/33) in the sequential surgery group, and 4.6% (6/130) in the control group. The differences in the PCO rate between the subgroups as well as among the 3 groups were statistically significant (p < 0.05). There were no significant differences in the interval between CS and PCO formation among the 3 groups. Conclusion: This study demonstrates that the PCO rate may be lower in patients who have a combined procedure of PPV and CS than in those who have a sequential procedure.

Documentation of capsular opacification and incomplete cell migration barrier formation by ThinOptX® IOL using Miyake–Apple view

The purpose of this study was to evaluate the in situ relationship of ThinOptX intraocular lens (IOL) in a cadaveric donor eye with posterior capsular opacification (PCO), following report of high PCO rates with this IOL. A cadaveric donor eye implanted with ThinOptX IOL and received at our eye bank was fixed in 10% formalin after retrieval of corneoscleral button. The globe was sectioned at equator and evaluated from the posterior (Miyake-Apple) view. Complete iridectomy was performed and IOL evaluated from the anterior (surgeon's) view. The IOL was well centered in the bag. A thick (Grade 4) Sommering ring was seen with centripetal extension across the IOL edge margin. The anterior capsule showed fibrosis and distortion of the capsulorrhexis margin. It seems from our findings that in some cases, the edge of the ThinOptX IOL may not provide an adequate barrier to epithelial cell migration and PCO formation. This can have clinical implications which need evaluation in large clinical and histopathological studies.

Comparison of capsular opacification and refractive status after placement of three different intraocular lens implants following phacoemulsification and aspiration of cataracts in dogs

To evaluate the effect of lens design and biomaterial on formation of posterior capsular opacification (PCO) and refractive correction. Animals studied Sixty dogs undergoing bilateral phacoemulsification for mature or diabetic cataracts. One randomly selected eye received a rounded edge 41D polymethyl-methacrylate (PMMA) intraocular replacement lens (IOL) and the contralateral eye received either a squared edge 41D hydrophilic acrylic IOL (n = 35) or a squared edge 40D hydrophobic acrylic IOL (n = 25). At the (mean = 79 day) reexamination period, PCO was graded using direct slit-lamp observation and by masked observer evaluation of digital images of the IOLs. Streak retinoscopy and B-mode ultrasound were performed at this period. The PCO score via direct slit-lamp was significantly lower for the hydrophilic acrylic IOL when compared to the PMMA IOL. Masked observer evaluation of digital images revealed that the acrylic IOLs had lower but generally not statistically significant PCO scores than the PMMA IOLs. Streak retinoscopy showed that the PMMA IOL was significantly closer to emmetropia (+0.44 D) when compared to either the hydrophilic acrylic (+0.96 D) or the hydrophobic acrylic (+1.2 D) IOLs. B-mode ultrasonography revealed the center of the hydrophilic acrylic IOL is 0.31 mm closer to the retina and the center of the hydrophobic acrylic IOL is 0.63 mm further from the retina when compared to the center of the PMMA to retina distance. Square edged foldable acrylic IOLs show a predisposition towards generating slightly less PCO than round edged PMMA IOLs in the early postoperative period, however, both acrylic IOLs had greater persistent hyperopia than the PMMA IOLs.

Polylactide-glycoli acid and rapamycin coating intraocular lens prevent posterior capsular opacification in rabbit eyes

Posterior capsular opacification (PCO) is caused by the proliferation and migration of residual lens epithelium cells (LECs) after extracapsular cataract extraction (ECCE). Rapamcin (RAPA) is known to be a potent immunosuppressive drug with anti-inflammatory and anti-proliferative effects. The aim of this study was to investigate the safety and efficacy of rapamycin sustained release from modified intraocular lens (IOLs) in the prevention of PCO in rabbits. Three types of IOLs were used, including the original IOL without modification, IOL with polylactide-glycoli acid (PLGA) coating (PLGA-IOL), and RAPA-loaded PLGA-IOL (RAPA-PLGA-IOL). Sixty New Zealand albino rabbits undergoing phacoemulsification in left eyes were randomly and equally divided into three groups. Group A was implanted with the original IOLs, group B was implanted with the PLGA-IOLs, and group C was implanted with the RAPA-PLGA-IOLs. All of the 60 treated left eyes were examined by a slit-lamp microscope. The concentrations of RAPA in the aqueous humor and blood were determined by high-performance liquid chromatography (HPLC), indicating an vivo release of drug from the polymer carrier. Anterior segment tissue was histologically examined, and wet posterior capsules were weighed. Six months after intervention the PCO was graded. The mean concentrations of RAPA in the aqueous humor from group C at 2 h, 1 days, 3 days, and 7 days after operation were 12.81 +/- 1.27 microg/ml, 14.57 +/- 0.99 microg/ml, 6.39 +/- 0.95 microg/ml, and 1.10 +/- 0.32 microg /ml respectively. The concentrations of RAPA in blood were undetectable. During the early days after the operation, the reactions of the anterior chamber from groups A and B were more severe than from group C. Our findings showed that the initial appearance of PCO in group C was much later than in the other two groups. The wet posterior capsules were weighed to be 0.3735 +/- 0.0943 g (group A), 0.3754 +/- 0.1093 g (group B), and 0.0432 +/- 0.0089 g (group C). Histological observation showed a similar phenomenon, that there was remarkably less accumulation of lens materials on the posterior capsules in group C than in the other two groups. Our findings suggest that the designed RAPA-PLGA-IOL effectively prevented formation and development of PCO for a relatively long duration.

An In Vitro Model of Posterior Capsular Opacity: SPARC and TGF-β2 Minimize Epithelial-to-Mesenchymal Transition in Lens Epithelium

This report presents a novel model for studies of extracellular matrix (ECM) in posterior capsular opacification (PCO) in vitro. Lens epithelial cells (LEC) were cultured with an intraocular lens (IOL) on a surface of type IV collagen in an evaluation of the importance of the ECM-cell interaction in formation of PCO. Abnormal migration, proliferation, and expression of proteins associated with the epithelial-to-mesenchymal transition (EMT) that characterizes PCO were observed in the presence and absence of the matricellular protein SPARC (secreted protein, acidic and rich in cysteine), which regulates matrix-cell interactions. The model for PCO in vitro consisted of an IOL placed on a membrane coated with collagen IV, a major constituent of the lens capsule. LECs from the lenses of wild-type (WT) and SPARC-null (SP-null) mice were cultured in the presence or absence of 10 ng/mL TGF-beta2 and 20 mug/mL recombinant human SPARC (rhSP) for up to 6 days. The migration of LECs was quantified. Labeling with BrdU and the measurement of DNA synthesis were assays for cell proliferation. Expression of the EMT markers, collagen type I, fibronectin, and alpha-smooth muscle actin were assessed using immunocytochemistry or Western immunoblots. LEC migration, proliferation, and the synthesis of EMT markers were enhanced in SP-null compared with WT LECs. TGF-beta2 inhibited the migration and proliferation of both WT and SP-null LECs in the presence of rhSP. TGF-beta2 increased the production of collagen type I, fibronectin, and alpha-SMA. The responses of SP-null LECs were rescued by the addition of recombinant human (rh)SP. A simple IOL culture system was useful for the evaluation of the effects of SPARC and TGF-beta2 on PCO in vitro. The action of TGF-beta2 on LEC migration and proliferation is influenced by SPARC, a regulator of matrix-cell interactions. The results indicate a functional intersection between pathways activated by TGF-beta2 and SPARC in the formation of PCO.

Improved Performances of Intraocular Lenses by Poly(ethylene glycol) Chemical Coatings

Cataract surgery is a routine ophthalmologic intervention resulting in replacement of the opacified natural lens by a polymeric intraocular lens (IOL). A main postoperative complication, as a result of protein adsorption and lens epithelial cell (LEC) adhesion, growth, and proliferation, is the secondary cataract, referred to as posterior capsular opacification (PCO). To avoid PCO formation, a poly(ethylene glycol) (PEG) chemical coating was created on the surface of hydrogel IOLs. Attenuated total reflectance Fourier transform infrared spectroscopy, "captive bubble" and "water droplet" contact angle measurements, and atomic force microscopy analyses proved the covalent grafting of the PEG chains on the IOL surface while keeping unchanged the optical properties of the initial material. A strong decrease of protein adsorption and cell adhesion depending on the molar mass of the grafted PEG (1100, 2000, and 5000 g/mol) was observed by performing the relevant in vitro tests with green fluorescent protein and LECs, respectively. Thus, the study provides a facile method for developing materials with nonfouling properties, particularly IOLs.

Development of posterior capsular opacification after pediatric cataract surgery

Introduction: Children have a higher incidence of posterior capsular opacification (PCO) than adults. We correlate PCO formation with type of cataract in pediatric patients who had cataract surgery with intraocular lens and the posterior capsule left intact (CE/IOL). Methods: Retrospective review of pediatric patients undergoing cataract surgery between 9/1/02 and 8/1/06. Results: One hundred twenty-four patients had cataract surgery during this time. Forty-four patients (63 eyes) had the posterior capsule left intact.

The Efficacy of an Acrylic Intraocular Lens Surface Modified with Polyethylene Glycol in Posterior Capsular Opacification

To investigate if the surface modification of intraocular lens (IOL) is efficient in the prevention of posterior capsular opacification (PCO), the acrylic surface of intraocular lens (Acrysof®) was polymerized with polyethylene glycol (PEG-IOL). The human lens epithelial cells (1×104 cells/mL) were inoculated on PEG grafted or unmodified acrylic lenses for the control. The adherent cells on each IOL surface were trypsinized and counted. The every PEG-IOL was implanted in 20 New Zealand rabbits after removal of crystalline lens. The formations of PCO were checked serially through retroilluminated digital photography, and the severity scores were calculated using POCOman®. The cell adherence patterns on each IOL were examined by scanning electron microscopy. As a result, the mean number of adherent cells of PEG-IOL (3.2±1.1×103) tended to be smaller than that of the acrylic controls (3.6±1.9×103) without a statistical significance (p=0.73). However, the mean severity of PCO formation in PEG-IOL was significantly lower than that in the control during the third to sixth weeks after surgery. Scanning electron microscopy revealed that the more patch-like cells were found firmly attached to the IOL surface in control than in the PEG-IOL. Conclusively, PEG polymerization to the acrylic IOL would possibly lessen the formation of PCO after cataract removal.

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

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

Modification of the surface properties of a lens material to influence posterior capsular opacification

To study the effect of surface properties of materials on cellular behaviour and the formation of posterior capsular opacification (PCO). Polymethylmethacrylate, silicone and a hydrophobic acrylic were plasma treated and used in tissue culture. The changes in surface properties were quantified by dynamic contact angle measurements. Bovine lens epithelial cells (BLECs) were seeded onto these materials and cultured for 1 month. Serial photographs were taken. The cells were then fixed and stained to facilitate counting. Plasma treatment significantly increased the hydrophilicity of surfaces. BLECs grew on all surfaces but significantly more cells adhered to the treated than the untreated surfaces. On the untreated surfaces the BLECs had a fibroblastic morphology whereas on the treated surfaces the cells maintained their epithelial morphology. Posterior capsular opacification is a form of wound healing and the behaviour of lens epithelial cells is central to its progression. Emphasis has been on the elimination of residual lens epithelial cells to combat PCO. This study demonstrated that the phenotype of BLECs was influenced by the surface properties of the intraocular lens materials. Gas plasma treatment of the materials increased their hydrophilicity and allowed the adhered BLECs to maintain their normal epithelial morphology. We believe that controlled growth of lens epithelial cells may reduce the incidence of PCO.

Intraocular lens-capsular bag imaging with ultrahigh-resolution optical coherence tomography: pseudophakic human autopsy eyes

Linnola et al.1 evaluated the capsule–intraocular lens (IOL) interface and posterior capsular opacification formation in 7 human pseudophakic autopsy eyes with a prototype high-resolution optical coherence tomography (OCT). Nevertheless, in light of the knowledge of applied optics, the design of this in vitro study hardly simulates the in vivo situation, and the reproduction of a similar-quality scan in real life is doubtful. Optical coherence tomography is a noninvasive imaging technology capable of producing high-resolution images, but it is not a technique without limitations in clinical application. From the law of physical optics, Podoleanu et al.2 show that variations in lamellar orientation, hydration, and thickness of the cornea can alter the geometry of refraction and have a significant bearing over polarization of OCT images. In scanning the IOL and posterior capsule of a pseudophakic patient, the cornea is the first layer separating air from tissue; if this layer is represented undistorted on OCT, the shape of the deeper layers, including the IOL, is bound to be increasingly blurred as a result of the cumulative effect of different and even unknown indices of refraction up to the depth of interest.2 These image distortions render the morphometric inference (orientation and shape) of the tissue involved impossible.2 Linnola et al. noted that the cornea of all the specimen eyes had been removed so that the authors were practically scanning the IOL/posterior capsule complex directly without the mentioned interference from the usual intervening corneal layers. In face of the high-resolution pictures provided, we wonder whether any image correction algorithm was implemented in the study and whether such an imaging technique can be successfully extrapolated in vivo.