Biointerface multiparametric study of intraocular lens acrylic materials

Self-assembled coating with a metal-polyphenolic network for intraocular lens modification to prevent posterior capsule opacification

Posterior capsule opacification (PCO) is a main complication after cataract surgery and intraocular lens (IOLs) implantation and is attributed to residual lens epithelial cells (LECs) migrating to the IOL surface and posterior capsules. IOL surface modification has been a newly-developing research filed in recent years; however, the applicability and economical acquisition of modified materials remain unsolved. In this study, we first applied a metal-polyphenolic network coating with a self-assembly technique on the IOL surface by using tannic acid (TA) combined with AlCl3, which are easily acquire and applying on the IOL surface to solve the IOL transmittance affair. Using wound healing and Transwell assay to verify AZD0364 inhibits cell migration (P< 0.05), the lipopolysaccharide-induced macrophage inflammation model to verify pterostilbene (PTE) inhibits the inflammatory reaction (P< 0.01). By optimizes its self-assembly coating parameters and calculating its drug release kinetics, we successfully loaded these two drugs on the coating, named TA (AZD0364/PTE) IOL. Its surface morphology characteristics were analyzed by scanning electron microscope, x-ray photoelectron spectrometer and water contact angle. The optical performance was carefully investigated by optical instruments and equipment (n= 3). Thein vitroresults showed that TA (AZD0364/PTE) IOL can significantly inhibit cell adhesion and acute inflammation (n= 3,P< 0.0001). Importantly, afterin vivoimplantation for 28 d with eight rabbits PCO models in two groups, the TA (AZD0364/PTE) IOL group maintained clear refracting media and decreased the inflammatory reaction compared with the original IOL group (P< 0.05). This study provides a new applicable and economical strategy for preventing PCO and offers a reference for the next generation of IOLs that benefit cataract patients.

Recent Advances of Intraocular Lens Materials and Surface Modification in Cataract Surgery

Advances in cataract surgery have increased the demand for intraocular lens (IOL) materials. At present, the progress of IOL materials mainly contains further improving biocompatibility, providing better visual quality and adjustable ability, reducing surgical incision, as well as dealing with complications such as posterior capsular opacification (PCO) and ophthalmitis. The purpose of this review is to describe the research progress of relevant IOL materials classified according to different clinical purposes. The innovation of IOL materials is often based on the common IOL materials on the market, such as silicon and acrylate. Special properties and functions are obtained by adding extra polymers or surface modification. Most of these studies have not yet been commercialized, which requires a large number of clinical trials. But they provide valuable thoughts for the optimization of the IOL function.

Research Progress Concerning a Novel Intraocular Lens for the Prevention of Posterior Capsular Opacification

Posterior capsular opacification (PCO) is the most common complication resulting from cataract surgery and limits the long-term postoperative visual outcome. Using Nd:YAG laser-assisted posterior capsulotomy for the clinical treatment of symptomatic PCO increases the risks of complications, such as glaucoma, retinal diseases, uveitis, and intraocular lens (IOL) pitting. Therefore, finding how to prevent PCO development is the subject of active investigations. As a replacement organ, the IOL is implanted into the lens capsule after cataract surgery, but it is also associated with the occurrence of PCO. Using IOL as a medium for PCO prophylaxis is a more facile and efficient method that has demonstrated various clinical application prospects. Thus, scientists have conducted a lot of research on new intraocular lens fabrication methods, such as optimizing IOL materials and design, and IOL surface modification (including plasma/ultraviolet/ozone treatment, chemical grafting, drug loading, coating modification, and layer-by-layer self-assembly methods). This paper summarizes the research progress for different types of intraocular lenses prepared by different surface modifications, including anti-biofouling IOLs, enhanced-adhesion IOLs, micro-patterned IOLs, photothermal IOLs, photodynamic IOLs, and drug-loading IOLs. These modified intraocular lenses inhibit PCO development by reducing the residual intraoperative lens epithelial cells or by regulating the cellular behavior of lens epithelial cells. In the future, more works are needed to improve the biosecurity and therapeutic efficacy of these modified IOLs.

Effect of time and temperature-dependent changes of IOL material properties on IOL: Lens capsule interactions

Posterior Capsule Opacification (PCO) is the most common complication associated with Intraocular Lens (IOL) implantation. Based on the assumption that the interactions between an IOL and the lens capsule (LC) may influence the extent of PCO formation, a new in vitro model was developed to quantify the adhesion force of an IOL to simulated LC using a custom-designed micro-force tester. Using this system, we examined the influence of temperature (room temperature vs. body temperature) and incubation time (0 vs. 24 h) on the adhesion force between IOLs and LCs. The results show that, in line with clinical observations of PCO incidence, the adhesion force increased at body temperature and with increase in incubation time in the following order, Acrylic foldable IOLs > Silicone IOLs > PMMA IOLs. By examining the changes of surface properties as a function of temperature and incubation time, we found that acrylic foldable IOLs showed the largest increase in their hydrophilicity and reported the lowest surface roughness in comparison to other IOL groups. Coincidentally, using a newly established macromolecular dye imaging system to simulate cell migration between IOLs and LC, we observed that the amount of macromolecular dye infiltration between IOLs and LCs was in the following order: PMMA IOLs > Silicone IOLs > Acrylic foldable IOLs. These results support a new potential mechanism that body temperature, incubation time, surface hydrophilicity and smoothness of IOLs greatly contribute to their tight binding to LCs and such tight binding may lead to reduced IOL: LC space, cell infiltration, and thus PCO formation.

Intraocular lenses as drug delivery devices

Cataract surgery is one of the most common and safe surgical procedures nowadays. However, it is not free of risks as endophthalmitis, ocular inflammation and posterior capsule opacification (PCO) can appear as post-surgery complications. The usual eye drop therapy used as prophylaxis for the former two complications has limited bioavailability. In turn, the prevention of PCO involves an adequate surgical technique and a careful choice of intraocular lens (IOL) design and material. Also, different drugs have been tested to reduce incidence of PCO, but no prophylaxis demonstrated to be completely effective. In the past few years, IOLs have been proposed as drug delivery devices to replace or/assist the usual eye drop therapy in the post-operatory period. The great advantage of drug loaded IOLs would be to ensure a continuous drug delivery, independent of patient's compliance without requiring any further action besides IOL implantation. The biggest challenge of drug loaded IOLs production is to achieve a controlled and extended release that meet therapeutic needs without inducing toxicity to the surrounding ocular tissues or affecting the physical properties of the lens. This review starts by addressing the possible complications after cataract surgery, as well as the most commonly adopted prophylaxis for each of them. The various types of IOLs are described and their main advantages/disadvantages are discussed. The different strategies pursued to incorporate drugs into the IOLs and control their release, which include soaking the IOL in the drugs solution, supercritical impregnation, surface modifications, and attachment of drug reservoirs to the IOL, among others, are reported. For each strategy, a summary of the publications is presented, which includes the target complication, the types and amounts of released drugs and the IOL materials. A brief description of each individual study is given afterwards. Optimization of drug loaded IOLs through mathematical modelling and possible issues raised by their sterilization are also tackled. At the end, the future commercialization of drug loaded IOLs is commented.

An in vitro system to investigate IOL: Lens capsule interaction

Posterior capsule opacification (PCO) is the most common complication associated with intraocular lens (IOL) implantation. Unfortunately, current in vitro models cannot be used to assess the potential of PCO due to their failure to simulate the posterior curvature of the lens capsule (LC) and IOL, a factor known to affect PCO pathogenesis in clinic. To overcome such a challenge, a new system to study IOL: LC interaction and potentially predict PCO was developed in this effort. It is believed that the interactions between an IOL and the lens capsule may influence the extent of PCO formation. Specifically, strong adhesion force between an IOL and the LC may impede lens epithelial cell migration and proliferation and thus reduce PCO formation. To assess the adhesion force between an IOL and LC, a new in vitro model was established with simulated LC and a custom-designed micro-force tester. A method to fabricate simulated LCs was developed by imprinting IOLs onto molten gelatin to create simulated three dimensional (3D) LCs with curvature resembling the bag-like structure that collapses on the IOL post implantation. By pushing the LC mold vertically downward, while measuring the change in position of the bending bar with respect to its start position, the adhesion force between the IOLs and LCs was measured. An in vitro system that can measure the adhesion force reproducibly between an IOL and LC with a resolution of ~1 μN was established in this study. During system optimization, the 10% high molecular weight gelatin produced the best LC with the highest IOL: LC adhesion force with all test lenses that were fabricated from acrylic foldable, polymethylmethacrylate (PMMA) and silicone materials. Test IOLs exerted different adhesion force with the 3D simulated LCs in the following sequence: acrylic foldable IOL > silicone IOL > PMMA IOL. These results are in good agreement with the clinical observations associated with PCO performance of IOLs made of the same materials. This novel in vitro system can provide valuable insight on the IOL: LC interplay and its relationship to clinical PCO outcomes.

[Posterior capsule opacification, glistenings and visual outcomes: 3 years after implantation of a new hydrophobic IOL]

PURPOSE

To evaluate the visual outcomes, the incidence of glistenings and posterior capsule opacification in a series of consecutive eyes with a new blue light-filtering hydrophobic acrylic intraocular lens (IOL) SETTING: Service d'ophtalmologie, clinique Beausoleil, avenue de Lodève, Montpellier.

DESIGN

Retrospective, cross-sectional study.

METHODS

This study included a series of 66 eyes that underwent routine cataract surgery with PODEye (PhysIOL SA, Liège, Belgium) monofocal IOL implantation between May 2011 and November 2011. These eyes were compared for glistenings with patients implanted with Acrysof material IOL (Alcon, Fort Worth, USA) who had a routine postoperative examination between January 2015 and August 2015. The safety of the IOL was assessed by visual acuity outcomes, as well as rotational stability, centration and postoperative medication. The incidence and severity of glistenings were evaluated with the slit lamp. Glistenings and PCO were graded subjectively (0=absent; 1=moderate; 2=dense). Follow-up was 3 years.

RESULTS

The mean visual acuity after PODEye implantation was 0.98±0.05 (n=50) in decimal notation at 1 year, 0.98±0.06 at 1 week, (n=66), 1.00±0.01 at 3 weeks (n=64) and 0.99±0.02 at 3 months (n=59). The IOL displayed stable positioning in all axes. Glistenings of grade 2 were absent in the G-Free/PODEye group, whereas they were significantly present in the Acrysof group. One out of 43 eyes at 3-year follow-up underwent YAG capulotomy at 37 months. Sixty-six percent of eyes had no PCO (grade 0) at 3 years.

CONCLUSIONS

The PODEye IOL was safe and stable. Glistenings grade 2 or more were not found with this blue light-filtering hydrophobic acrylic IOL. PCO occurrence was low at three years.

Scanning electron microscopic characteristics of manually loaded and preloaded foldable acrylic intraocular lenses

PURPOSE:

To compare surface alterations between preloaded and manually loaded intraocular lens.

METHODS:

Scanning electron microscope was utilized to evaluate surface alteration and deposits in four different types of intraocular lenses: preloaded hydrophobic acrylic, preloaded hydrophilic acrylic, manually loaded hydrophobic acrylic, and manually loaded hydrophilic acrylic. Six lenses with different powers (+6 D, +22 D, and +29 D) were used from each category, to represent different thickness categories of the intraocular lenses.

RESULTS:

In total, 30 intraocular lenses have been evaluated in this study: 4 from the control group (2 hydrophobic and 2 hydrophilic lenses) and 12 from the preloaded intraocular lens and manually loaded groups (6 hydrophilic and 6 hydrophobic lenses with different powers). Surface deposits were found in eight hydrophobic intraocular lenses compared to a single intraocular lens with scattered deposits on the optical surface of a hydrophilic intraocular lens. In manually loaded intraocular lens group, five hydrophobic and one hydrophilic intraocular lenses showed identifiable marks on the optical surface. In the preloaded intraocular lens group, three hydrophobic intraocular lenses showed identifiable marks on the optical surface and three hydrophobic intraocular lenses showed surface wrinkling. All hydrophilic intraocular lenses revealed no identifiable marks.

CONCLUSION:

Surface alterations and deposits are a common finding in both preloaded and manually loaded intraocular lenses. Water content of acrylic intraocular lenses is an important factor predisposing to these changes, and hydrophobic intraocular lenses are more vulnerable than hydrophilic lenses. The impact on the final visual outcome needs further studies.

Pathology and immunohistochemistry of capsular bag in spontaneously late dislocated capsular bag-intraocular lens complex

Purpose:

Our study aims to evaluate the morphology, histopathology, and immunohistochemistry of the spontaneously late dislocated capsular bag-intraocular lens (CB-IOL) complex. Various etiologies and possible pathogenesis of the event are also discussed.

Methods:

This was a tertiary-care setting and retrospective observational case series. The surgically explanted intact specimens of spontaneously late dislocated CB-IOL complex were studied. The demographics, duration of pseudophakia, IOL design/material, and specimen measurements were noted. Fresh specimens were photographed, and computer software was used for measurements. After processing, a detailed microscopic examination was carried out for three different sections of each specimen with hematoxylin and eosin (H and E), Masson's-trichrome, and immunohistochemistry stain for vimentin. The Mann–Whitney U-test was used for the statistical analysis.

Results:

Of 12 specimens, the mean CB and capsulorhexis opening size were 8.32 ± 0.8 mm and 3.62 ± 0.61 mm, respectively. The average CB-IOL complex size of our study was significantly lower than the studies reported in the literature (P ≤ 0.001). All (n = 12, 100%) were acrylic IOLs with 11 (91.67%) having single-piece design. All specimens on H and E stain showed extensive subepithelial fibrosis while Masson's trichrome staining showed that none had any pseudoexfoliation material. The circumferential sphincter-like fibrous tissue arrangement was seen in all specimens. Immunohistochemical expression of vimentin suggested the mesenchymal metaplasia of epithelial A-cells.

Conclusion:

Significant fibrotic contraction of the CB and phimosis of capsulorhexis may cause a progressive zonular tear. This is probably the most important etiology of spontaneous late dislocation of the CB-IOL complex.

Physicochemical and surface properties of acrylic intraocular lenses and their clinical significance

To analyze and compare several commercially available acrylic intraocular lenses (IOLs) with particular regard to their clinical significance, we examined the physicochemical and surface properties of four currently available acrylic IOLs using static water contact angle, atomic force microscopy (AFM), Raman spectroscopy, and differential scanning calorimetry (DSC) measurements. The hydrophobic acrylic IOLs, ZA9003, and MA60BM, had contact angles ranging from 77.9° ± 0.65° to 84.4° ± 0.09°. The contact angles in the hydrophilic acrylic (970C) and heparin-surface-modified (HSM) hydrophilic acrylic IOLs (BioVue) were 61.8° ± 0.45° and 69.7° ± 0.76°, respectively. The roughness of the IOL optic surface differed depending on the type of IOL (p < 0.001). The surface roughness of BioVue had the lowest value: 5.87 ± 1.26 nm. This suggests that the BioVue IOL may lead to reduced cellular adhesion compared to the unmodified IOLs. All IOLs including those composed of acrylic optic materials from different manufacturers showed distinct Raman spectra peaks. The glass transition temperatures (T_g) for the hydrophobic acrylic IOLs were between 12.5 and 13.8 °C. These results suggest that the intraoperative and postoperative behavior of an IOL can be predicted. This information is also expected to contribute greatly to the industrial production of reliable biocompatible IOLs.

A new method using insert-based systems (IBS) to improve cell behavior study on flexible and rigid biomaterials

In vitro studies about biomaterials biological properties are essential screening tests. Yet cell cultures encounter difficulties related to cell retention on material surface or to the observation of both faces of permeable materials. The objective of the present study was to develop a reliable in vitro method to study cell behavior on rigid and flexible/permeable biomaterials elaborating two specific insert-based systems (IBS-R and IBS-F respectively). IBS-R was designed as a specific cylindrical polytetrafluoroethylene (PTFE) system to evaluate attachment, proliferation and morphology of human gingival fibroblasts (HGFs) on grade V titanium and lithium disilicate glass-ceramic discs characteristics of dental prostheses. The number of cells, their covering on discs and their morphology were determined from MTS assays and microscopic fluorescent images after 24, 48 and 72 h. IBS-F was developed as a two components system to study HGFs behavior on guided bone regeneration polyester membranes. The viability and the membrane barrier effect were evaluated by metabolic MTS assays and by scanning electron microscopy. IBS-R and IBS-F were shown to promote (1) easy and rapid handling; (2) cell retention on biomaterial surface; (3) accurate evaluation of the cellular proliferation, spreading and viability; (4) use of non-toxic material. Moreover IBS-F allowed the study of the cell migration through degradable membranes, with an access to both faces of the biomaterial and to the bottom of culture wells for medium changing.

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.