Biocompatibility of intraocular lens materials

Current State of the Art and Next Generation of Materials for a Customized IntraOcular Lens according to a Patient-Specific Eye Power

Intraocular lenses (IOLs) are commonly implanted after surgical removal of a cataractous lens. A variety of IOL materials are currently available, including collamer, hydrophobic acrylic, hydrophilic acrylic, PHEMA copolymer, polymethylmethacrylate (PMMA), and silicone. High-quality polymers with distinct physical and optical properties for IOL manufacturing and in line with the highest quality standards on the market have evolved to encompass medical needs. Each of them and their packaging show unique advantages and disadvantages. Here, we highlight the evolution of polymeric materials and mainly the current state of the art of the unique properties of some polymeric systems used for IOL design, identifying current limitations for future improvements. We investigate the characteristics of the next generation of IOL materials, which must satisfy biocompatibility requirements and have tuneable refractive index to create patient-specific eye power, preventing formation of posterior capsular opacification.

Innovation in the Development of Synthetic and Natural Ocular Drug Delivery Systems for Eye Diseases Treatment: Focusing on Drug-Loaded Ocular Inserts, Contacts, and Intraocular Lenses

Nowadays, ocular drug delivery still remains a challenge, since the conventional dosage forms used for anterior and posterior ocular disease treatments, such as topical, systemic, and intraocular administration methods, present important limitations mainly related to the anatomical complexity of the eye. In particular, the blood-ocular barrier along with the corneal barrier, ocular surface, and lacrimal fluid secretion reduce the availability of the administered active compounds and their efficacy. These limitations have increased the need to develop safe and effective ocular delivery systems able to sustain the drug release in the interested ocular segment over time. In the last few years, thanks to the innovations in the materials and technologies employed, different ocular drug delivery systems have been developed. Therefore, this review aims to summarize the synthetic and natural drug-loaded ocular inserts, contacts, and intraocular lenses that have been recently developed, emphasizing the characteristics that make them promising for future ocular clinical applications.

Biomimetic materials based on zwitterionic polymers toward human-friendly medical devices

This review summarizes recent research on the design of polymer material systems based on biomimetic concepts and reports on the medical devices that implement these systems. Biomolecules such as proteins, nucleic acids, and phospholipids, present in living organisms, play important roles in biological activities. These molecules are characterized by heterogenic nature with hydrophilicity and hydrophobicity, and a balance of positive and negative charges, which provide unique reaction fields, interfaces, and functionality. Incorporating these molecules into artificial systems is expected to advance material science considerably. This approach to material design is exceptionally practical for medical devices that are in contact with living organisms. Here, it is focused on zwitterionic polymers with intramolecularly balanced charges and introduce examples of their applications in medical devices. Their unique properties make these polymers potential surface modification materials to enhance the performance and safety of conventional medical devices. This review discusses these devices; moreover, new surface technologies have been summarized for developing human-friendly medical devices using zwitterionic polymers in the cardiovascular, cerebrovascular, orthopedic, and ophthalmology fields.

Rapid and Economical Drug-Eluting IOL Preparation via Thermoresponsive Agarose Coating for Effective Posterior Capsular Opacification Prevention

Posterior capsular opacification (PCO), the highest incidence complication after cataract surgery, is mainly due to the attachment, proliferation, and migration of the residual lens epithelial cells (LECs). Although the drug-eluting IOLs have been proved to be an effective way to prevent PCO incidence, its preparations are time consuming and require tedious preparation steps. Herein, the thermoreversible agarose is adopted to prepare drug-eluting IOL. Such functional coating can be obtained easily by simple immersion in the antiproliferative drug containing hot agarose and taken out for cooling, which not only does not affect the optical property but also can effectively decrease the PCO incidence after intraocular implantation. As a result, the proposed agarose coating provides a rapid and economical alternative of drug-eluting IOL fabrication for PCO prevention.

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.

A transparent hydrophilic anti-biofouling coating for intraocular lens materials prepared by "bridging" of the intermediate adhesive layer

The attachment of bio-foulants, including unwanted cells, proteins, and bacteria, to a medical device such as an intraocular lens can lead to implantation failure. Hydrophilic polymers are often used as surface modifiers in the fabrication of anti-biofouling coatings, but a hydrophilic coating can easily become swollen and peel off the substrate. In this study, we chose polymethyl methacrylate (PMMA) as the representative material of intraocular lenses because PMMA has better biocompatibility, a higher refractive index, better optical clarity, lighter weight, more stable performance, and lower cost than other intraocular lens materials. We fabricated polyvinyl alcohol (PVA) coatings with or without a "bridge", that is, an intermediate adhesive layer (AL), to increase the adhesion bonding effect between the anti-biofouling coating and the substrate. The results indicated that the prepared coatings were transparent and noncytotoxic. Moreover, the anti-adhesion properties of the cells and the resistance properties to nonspecific protein adsorption of PMMA modified by both AL and PVA coatings were better and more durable compared with the sample only modified with a physically dipped PVA coating. The coating prepared by AL "bridging" provides a new strategy for the preparation of a transparent hydrophilic anti-biofouling coating suitable for PMMA intraocular lens materials.

Light scattering in intraocular lenses explanted 15 to 40 years after surgery

The optical quality of intraocular lenses (IOLs) of different materials that have been implanted from 16 to 44 years in human eyes was studied. The IOLs were explanted due to other causes than loss of transparency. The scattered light from the IOLs was assessed in two angular regimes by using dark field images (for wide angles) and the optical integration method (for narrower angles). No evident differences were found in the scattering intensities processed from the dark images. The explanted lenses presented slightly increased amounts of straylight between 1 and 5.1° when compared to a reference new unused lens.

Delayed postoperative opacification of three hydrophobic acrylic intraocular lens: A scanning electron microscopic and energy dispersive spectroscopic study

Purpose:

The aim of this study was to report scanning electron microscopic (SEM) and energy dispersive spectroscopic (EDS) findings of three specimens of opaque hydrophobic acrylic intraocular lens (IOL) explanted in delayed postoperative period for visual indications.

Methods:

Clinical data and photographs from each subject were obtained. Explanted IOLs were examined under gross and light microscopy followed by SEM coupled with EDS.

Results:

All three subjects underwent IOL implantation following senile cataract extraction at an average age of 64.3 ± 0.3 years, and the IOLs were in situ for a duration of 11.3 ± 4.04 years. The IOL explantation and exchange were done due to late postoperative opacification of the IOL and significant visual deterioration. The milky iridescent opacity affected the full thickness of IOL optics in the first two specimens and in the third only two surfaces were involved. SEM detected surface cracks in the first specimen, typical conglumated surface, pores and accumulation of crystals with surface deposit of nano-particles on the second specimen and uneven surface erosion in the third specimen. SEM detected mainly sodium (Na) and chloride (Cl) spikes. All patients recovered normal vision following IOL exchange.

Conclusion:

SEM features of the IOL optics and absence of calcium and phosphate spikes in EDS and other findings were consistent and suggestive of hydrolytic biodegradation of hydrophobic acrylic IOL polymer in ocular media and was responsible for delayed postoperative opacification of the hydrophobic IOLs and visual loss.

Intraocular Lens with Mussel-Inspired Coating for Preventing Posterior Capsule Opacification via Photothermal Effect

Phacoemulsification with implantation of intraocular lens (IOLs) has been widely applied as a standard treatment for cataract, which is the leading cause of vision impairment. However, it still remains a critical challenge to prevent posterior capsule opacification (PCO) in terms of postoperative visual quality. Herein, we report IOLs with mussel-inspired coatings for inhibiting lens epithelial cells and then preventing PCO through photothermal conversion effect. The mussel-inspired coatings are deposited on the nonoptical surface areas of IOLs, endowing the modified IOLs with efficient photothermal conversion property. The temperature can be facilely raised to 50-60 °C for the photothermal IOLs (PT-IOLs) by near-infrared (NIR) laser irradiation at a safe intensity of 0.3 W/cm². These PT-IOLs display high capability of inhibiting lens epithelial cells (LECs) in vitro. Therefore, under routine NIR laser irradiation, New Zealand white rabbits implanted with the PT-IOLs demonstrate significantly lower evaluation of PCO (EPCO) scores than the control groups. The overall results indicate that our PT-IOLs provide a promising choice for the clinical prevention of PCO, thus opening a way to maintain the postoperative visual qualities for cataract patients.

Simulating Outcomes of Cataract Surgery: Important Advances in Ophthalmology

As the human eye ages, the crystalline lens stiffens (presbyopia) and opacifies (cataract), requiring its replacement with an artificial lens [intraocular lens (IOL)]. Cataract surgery is the most frequently performed surgical procedure in the world. The increase in IOL designs has not been paralleled in practice by a sophistication in IOL selection methods, which rely on limited anatomical measurements of the eye and the surgeon's interpretation of the patient's needs and expectations. We propose that the future of IOL selection will be guided by 3D quantitative imaging of the crystalline lens to map lens opacities, anticipate IOL position, and develop fully customized eye models for ray-tracing-based IOL selection. Conversely, visual simulators (in which IOL designs are programmed in active elements) allow patients to experience prospective vision before surgery and to make more informed decisions about which IOL to choose. Quantitative imaging and optical and visual simulations of postsurgery outcomes will allow optimal treatments to be selected for a patient undergoing modern cataract surgery.

Surface Modification of Intraocular Lens with Hydrophilic Poly(Sulfobetaine Methacrylate) Brush for Posterior Capsular Opacification Prevention

Purpose: The intraocular lens (IOL) is a common, yet important, implantable device used in treatment of cataract in clinics. However, the unexpected adhesion of postoperative residual lens epithelial cells (LECs) often causes serious complications, such as posterior capsular opacification (PCO), which lead to vision loss again. In this investigation, a poly(sulfobetaine methacrylate) (PSBMA) brush coating was fabricated on an IOL to generate a hydrophilic surface coating on the IOL for enhanced cell adhesion resistance so as to decrease PCO incidence. Methods: The PSBMA brush coating on the IOL surface was fabricated using surface-initiated reversible addition-fragmentation chain transfer polymerization. X-ray photoelectron spectroscopy (XPS) was used to demonstrate the surface coating preparation. The water contact angle (WCA) measurement was used to test surface hydrophilicity. In vitro LEC culture was use to evaluate the cell behavior on the IOL material surfaces, with or without PSBMA coating modification. Finally, animal cataract surgeries were carried out to evaluate in vivo biocompatibilities and anti-PCO effects. Results: The XPS and WCA measurements illustrate successful surface modification and good surface hydrophilicity. The in vitro cell culture results show that the hydrophilic PSBMA polymer brush coating evidently decreases adhesion and proliferation of LECs. Results of the in vivo cataract surgery with intraocular implantation show that PSBMA modification on the IOL surface does not induce side effects in nearby tissues, whereas posterior capsular hyperplasia can be evidently reduced. Conclusion: The PSBMA brush surface-modified IOL has good in vivo biocompatibility and it can effectively reduce the incidence of postoperative PCO.

Drug-Eluting Hydrophilic Coating Modification of Intraocular Lens via Facile Dopamine Self-Polymerization for Posterior Capsular Opacification Prevention

Posterior capsular opacification (PCO) is the most important complication in cataract phacoemulsification and intraocular lens (IOL) implantation surgery, mainly stemming from the adhesion, proliferation, and transdifferentiation of the postsurgically residual lens epithelial cells (LECs). Previous investigations mainly focused on the hydrophilic surface modification of the IOLs for PCO prevention, such as heparinization. However, the long-term clinical investigations show that there is no significant difference between pristine and heparinized IOLs. In the present study, a synergetic coating with properties of drug-eluting and hydrophilicity was designed and modified onto the IOL surface via facile dopamine self-polymerization. The antiproliferative drug doxorubicin (DOX) was loaded when a polydopamine (PDA) coating was formed on the IOL surface. The hydrophilic 2-methacryloyloxyethyl phosphorylcholine (MPC) could be subsequently grafted onto the drug-loaded PDA coating surface easily. The hydrophilic outer layer could slow down drug-eluting from underneath the drug-incorporated coating. In vitro and in vivo investigations demonstrated that such multifunctionalized coating-modified IOLs could not only thoroughly and effectively prevent PCO development by induced cell apoptosis but also render safety and biocompatibility to the surrounding tissues.

Intraocular Lenses: Overview of Designs, Materials, and Pathophysiologic Features

This article provides an overview of intraocular lenses (IOLs) currently used in cataract surgery. Aspects presented include design features related to IOL construction and sites of fixation; optic, filter, and haptic materials; as well as pathophysiologic features of uveal biocompatibility, capsular biocompatibility, and postoperative IOL opacification. This overview also includes supplementary (add-on; piggyback) lenses implanted in eyes that are already pseudophakic and considerations on IOLs used in the pediatric population. Different IOLs are made available to surgeons each year, including lenses with increasingly complex design characteristics owing to advancements in manufacturing and surgical techniques.

Transient crystalline lens deposits following the insertion of a phakic sulcus-fixated collamer intraocular lens in a hyperopic eye

Purpose

The purpose of this study was to report crystalline lens deposit formation following ICL implantation for the correction of hyperopia.

Observations

A 23-year-old male presented at the American University of Beirut Medical Center in 2008 seeking refractive surgery for hyperopia. His cycloplegic refraction was +7–1.25 × 115° and +7–1.00 × 115° in the right and left eyes, respectively, yielding a vision of 20/20 bilaterally. The patient underwent right eye insertion of a non-toric phakic sulcus-fixated collamer lens 2 weeks after undergoing peripheral iridotomies. The early postoperative course was complicated by anterior chamber inflammation and the appearance of diffuse whitish precipitates on the anterior surface of the crystalline lens, hypotony, and a mid-dilated mildly reactive pupil. With the prompt administration of topical and systemic steroids, the anterior chamber reaction subsided, and the anterior capsular deposits gradually resolved peripherally with some remaining centrally over the course of several weeks. The patient's visual acuity at 6 months was 20/20.

Conclusionsand importance

Adequate viscoelastic removal and minimal iris stimulation seem to be essential to avoid this condition in hyperopic implants that lack a central port. Additionally, prompt treatment can minimize visual impairment and hasten visual recovery.

Systematic Study on the Biomechanical Stability of C-Loop Intraocular Lenses: Approach to an Optimal Design of the Haptics

To study the main design parameters that affect the mechanical stability of C-loop intraocular lenses, leading to an optimal design that minimizes the axial displacement, tilt and rotation. A total of 144 geometrical variations were studied on a 1-piece, non-angulated, C-loop hydrophobic acrylate intraocular lens. The study was performed in a finite element modeling simulation. The suitable set of variations was determined using a mixed-factorial analysis, allowing to analyse the impact of the different designs on the mechanical stability of the lens (compression force, axial displacement, tilt and rotation). The design parameters under study were: the length, width, thickness and opening angle of the haptic, the haptic-optic junction and the start of the haptic curvature. The compression (or reaction) force is affected by the haptic width, the haptic-optic junction, and the interaction between both. The axial displacement is mainly affected by the width and thickness of the haptic, and the size of the haptic-optic junction as well. The tilt is affected by the haptic thickness and the interaction between the haptic curvature and the haptic-optic junction. The rotation is affected by the start of the haptic curvature, the haptic-optic junction and the haptic width. The haptic-optic juntion is one of the most influential parameters affecting the four responses studied of the C-Loop IOL. The smaller the haptic-optic juntion, the better biomechanical stability.

Incidence of posterior capsular opacification requiring Nd:YAG capsulotomy after cataract surgery and implantation of enVista® MX60 IOL

PURPOSE

To evaluate incidence of posterior capsule opacification requiring Nd:YAG capsulotomy over 3 years in a large series of eyes implanted with the enVista^® MX60 Intraocular Lens (IOL).

METHODS

A university-based, single-center, observational study of patients' medical records was conducted. Uneventful cataract surgery patients with in-the-bag implantations of the enVista^® MX60 IOL with a minimum of 24 months follow-up were included in the study. Exclusion criteria were insufficient follow-up (<24 months), intraoperative complications and combined surgery. The primary outcome measure was rate of YAG laser capsulotomy, while secondary outcome measures were time to YAG laser capsulotomy and rate of glistenings.

RESULTS

A total of 245 eyes of 143 patients received the MX60 IOL and were followed in the same center. Of these, 226 eyes were included in the study. Mean age was 80.7±8.3 years and M/F ratio was 42/101 (29.4/70.6%). The mean preoperative distance (logMAR) visual acuity was 0.67±0.5, while postoperatively it was 0.31±0.5 and 0.32±0.5 at the last visit. The Mean±SD follow-up time (min-max) was 35.2±7.2, (24-48.4) months. The incidence of Nd:YAG capsulotomy over 3 years was 5/226 (2.2%). Average time between surgery and Nd:YAG capsulotomy was 32.17 months. Univariate analysis of age, gender, presence of comorbidity and baseline visual acuity found no predictive factors for capsulotomy. No glistenings were reported at any postoperative visit.

CONCLUSION

The three-year cumulative incidence of PCO requiring Nd:YAG laser capsulotomy was 2.2% for the enVista^® MX-60 IOL, with no glistenings observed during follow-up. This low rate confirms the excellent safety profile of this IOL.

Does Nd:YAG Capsulotomy Increase the Risk of Retinal Detachment?

Laser capsulotomy is accepted as a standard and effective treatment for posterior capsule opacification. It is generally believed that neodymium:YAG (Nd:YAG) capsulotomy is related to an increased risk of retinal detachment (RD). The aim of this study was to evaluate the association between Nd:YAG capsulotomy and risk for developing RD. A PubMed and Medline search was conducted using the terms "retinal detachment" and "Nd:YAG laser capsulotomy." Of the articles retrieved by this method, all publications in English and abstracts of non-English publications were reviewed. The literature analysis presented no convincing evidence supporting the association between Nd:YAG capsulotomy and increased risk for developing RD. The existing discrepancy between some studies might be related to inadequate group sizes, short observation period, and co-existing disorders. We also reviewed the possible risk factors for RD after Nd:YAG capsulotomy and found no association with preceding surgical approach, existing posterior vitreous detachment, and intraocular lens design. Myopic patients should be treated with caution, as it cannot be concluded that Nd:YAG capsulotomy does not increase RD rate in this cohort. Treatment energy should be as low as possible, as high energy levels and anterior hyaloid damage might increase the chance for RD development. Cataract surgery itself is a potential RD risk factor, particularly after intraoperative capsule complications.

Advances and challenges of intraocular lens design [Invited]

Phacoemulsification technique with intraocular lens implantation has been a common treatment for cataract patients. With rising demand among the public, new technologies for lens design have emerged to minimize intraocular aberrations, improving visual quality to the largest extent. This paper systematically reviews the development of materials applied in lens manufacturing, the different categories of intraocular lenses, and respective design principles. The advantages and potential drawbacks of intraocular lenses are illustrated in the paper, and prospective research to improve the design are presented in the end.

Biomaterial Influence on Intraocular Lens Performance: An Overview

There is strong evidence that the IOL material is the factor having the greatest impact on posterior capsule opacification (PCO), anterior capsule opacification (ACO) development, and glistening formation after cataract surgery, even though there are other IOL features—such as haptic material and design and edge and optic design—that also have some influence. We reviewed the published literature describing the adverse events that are mainly related to the intraocular lens (IOL) material, such as PCO, ACO, and the subsequent capsule contraction, as well as glistening formation. The adverse events presented in this overview are the most common ones in clinical practice, and therefore, they are generally included in the clinical protocols for IOL evaluation.

Comparison of two Nd:YAG laser posterior capsulotomy: cruciate pattern vs circular pattern with vitreous strand cutting

AIM

To investigate the effects and safety of neodymium: yttrium-aluminium-garnet (Nd:YAG) laser posterior capsulotomy with vitreous strand cutting.

METHODS

A total of 40 eyes of 37 patients with symptomatic posterior capsular opacity (PCO) were included in this prospective randomized study and were randomly subjected to either cruciate pattern or round pattern Nd:YAG posterior capsulotomy with vitreous strand cutting (modified round pattern). The best corrected visual acuity (BCVA), intraocular pressure (IOP), refractive error, endothelial cell count (ECC), anterior segment parameters, including anterior chamber depth (ACD) and anterior chamber angle (ACA) were measured before and 1mo after the laser posterior capsulotomy.

RESULTS

In both groups, the BCVA improved significantly (P<0.001 for the modified round pattern group, P=0.001 for the cruciate pattern group); the IOP and ECC did not significantly change. The ACD significantly decreased (P<0.001 for both) and the ACA significantly increased (P=0.001 for the modified round pattern group and P=0.034 for the cruciate group). The extent of changes in these parameters was not significantly different between the groups.

CONCLUSION

Modified round pattern Nd:YAG laser posterior capsulotomy is an effective and safe method for the treatment of PCO. This method significantly changes the ACD and ACA, but the change in refraction is not significant. Modified round pattern Nd:YAG laser posterior capsulotomy can be considered a good alternative procedure in patients with symptomatic PCO.

Improvement of Uveal and Capsular Biocompatibility of Hydrophobic Acrylic Intraocular Lens by Surface Grafting with 2-Methacryloyloxyethyl Phosphorylcholine-Methacrylic Acid Copolymer

Biocompatibility of intraocular lens (IOL) is critical to vision reconstruction after cataract surgery. Foldable hydrophobic acrylic IOL is vulnerable to the adhesion of extracellular matrix proteins and cells, leading to increased incidence of postoperative inflammation and capsule opacification. To increase IOL biocompatibility, we synthesized a hydrophilic copolymer P(MPC-MAA) and grafted the copolymer onto the surface of IOL through air plasma treatment. X-ray photoelectron spectroscopy, atomic force microscopy and static water contact angle were used to characterize chemical changes, topography and hydrophilicity of the IOL surface, respectively. Quartz crystal microbalance with dissipation (QCM-D) showed that P(MPC-MAA) modified IOLs were resistant to protein adsorption. Moreover, P(MPC-MAA) modification inhibited adhesion and proliferation of lens epithelial cells (LECs) in vitro. To analyze uveal and capsular biocompatibility in vivo, we implanted the P(MPC-MAA) modified IOLs into rabbits after phacoemulsification. P(MPC-MAA) modification significantly reduced postoperative inflammation and anterior capsule opacification (ACO), and did not affect posterior capsule opacification (PCO). Collectively, our study suggests that surface modification by P(MPC-MAA) can significantly improve uveal and capsular biocompatibility of hydrophobic acrylic IOL, which could potentially benefit patients with blood-aqueous barrier damage.

Bottom-up fabrication of zwitterionic polymer brushes on intraocular lens for improved biocompatibility

Intraocular lens (IOL) is an efficient implantable device commonly used for treating cataracts. However, bioadhesion of bacteria or residual lens epithelial cells on the IOL surface after surgery causes postoperative complications, such as endophthalmitis or posterior capsular opacification, and leads to loss of sight again. In the present study, zwitterionic polymer brushes were fabricated on the IOL surface via bottom-up grafting procedure. The attenuated total reflection-Fourier transform infrared and contact angle measurements indicated successful surface modification, as well as excellent hydrophilicity. The coating of hydrophilic zwitterionic polymer effectively decreased the bioadhesion of lens epithelial cells or bacteria. In vivo intraocular implantation results showed good in vivo biocompatibility of zwitterionic IOL and its effectiveness against postoperative complications.

Surface PEGylation of intraocular lens for PCO prevention: An in vivo evaluation

Posterior capsular opacification (PCO) is a common complication in cataract surgery. The development of PCO is attributed to the combination of adhesion, migration, proliferation, and transdifferentiation of the residual lens epithelial cells (LEC) onto the interface of intraocular lens (IOL) material and lens posterior, in which the initial adhesion is the beginning step and plays important roles. In the present study, hydrophilic polyethylene glycol (PEG) was immobilized onto IOL surface via plasma-aided chemical grafting procedure. The attenuated total reflection - Fourier transform infrared (ATR-FTIR) and contact angle (CA) - measurements indicate the successful surface PEGylation, as well as the excellent hydrophilicity of the surfaces. Compared with pristine IOL, the PEGylation does not influent its optical property, whereas the initial adhesion of LEC is greatly inhibited. In vivo ocular implantation results show that the PEGylated IOL presents good in vivo biocompatibility, and can effectively prevent the PCO development.

Late Opacification of a Hydrophilic Acrylic Intraocular Lens in Europe

Purpose

To describe the clinical and microscopic findings in 2 different patients of 2 cases of late opacification of the hydrophilic acrylic intraocular lens (IOL) Ioflex.

Methods

Two eyes of 2 patients (73 and 74 years old) had an uneventful phacoemulsification surgery with implantation of the Ioflex IOL (power +21.5 D). At 5 years after surgery, a dense IOL opacification was detected in both cases with significant visual degradation. The IOLs were explanted and analyzed by microscopy.

Results

In both cases, a satisfactory visual recovery was achieved (corrected distance visual acuity of 6/9 and 6/12). Microscopic examination of the explanted IOLs revealed multiple small granules on the surface/subsurface of the lens. Although histochemical or surface analyses were not performed, the aspect appears consistent with a process of calcification of this lens design. Other findings included few surface contaminants, such as fibers, crystals that may correspond to dry viscoelastic and/or salt solutions, as well as pigments and dust-like deposits.

Conclusions

Opacification of the posterior chamber hydrophilic acrylic IOL Ioflex probably related to calcification can appear several years after its implantation and requires IOL exchange due to the significant visual loss induced. More studies are required to understand the causes of this complication.

Bottom-Up Fabrication of PEG Brush on Poly(dimethylsiloxane) for Antifouling Surface Construction

Poly(dimethylsiloxane) silicones have found many applications in biomedical devices, whereas their surface hydrophobicity always brings about unexpected bioadhesion, causing complications of the implanted biomedical devices. In this work, surface-initiated reversible addition-fragmentation chain transfer (SI-RAFT) polymerization was utilized to generate PEG brushes on silicone surface, obtaining highly hydrophilic surface coatings. Such PEG brush coated silicone presents excellent antifouling to protein, cells, and bacteria, which may have great potential in implantable biomaterial surface modifications.

Case Report: Explantation of A Binkhorst Iridocapsular Lens >30 Years After Implantation in an Eye With Pseudoexfoliation Syndrome

An 86-year-old man with a Binkhorst 2-loop intraocular lens (IOL) that was implanted in the pupillary sphincter 33 years earlier was examined. The pupil of the implanted eye with the Binkhorst IOL was irregular and the eye had pseudoexfoliation (PEX) syndrome. Pupillary erosion resulted from rubbing of the IOL edge against the pupillary sphincter with PEX material. The IOL was removed because of visual distortion and intense pseudophakodonesis. Gross and light microscopic analyses showed no irido-fibro-lenticular adhesions over the lens or fragments of iris tissue attached to the lens. Scanning electron microscopy showed several pores of different sizes. No inflammatory cells were present, suggesting that the IOL was well tolerated.The case suggested that the pupillary ruff was not a good location for implantation of an IOL in an eye with PEX. Caution is recommended before implanting or suturing an IOL close to the pupillary border in eyes with PEX during cataract surgery.

Intraocular Lens Opacification After Endothelial Keratoplasty as Analyzed by Environmental Scanning Electron Microscopy

PURPOSE

To describe a case of hydrophilic intraocular lens (IOL) opacification based on IOL analysis after Descemet stripping automated endothelial keratoplasty.

METHODS

A 60-year-old woman had uneventful phacoemulsification after the implantation of a hydrophilic IOL (Akreos-Adapt; Bausch & Lomb) into both eyes. Because of postoperative corneal decompensation in the right eye, 2 Descemet stripping automated endothelial keratoplasty operations were performed within 1 year. After the second procedure, the graft was not well attached, requiring an intracameral injection of air on day 3. After 1 year, opacification was observed on the superior 2/3 of the anterior surface of the IOL, along with a significant decrease in visual acuity. The IOL was explanted 6 months after the opacification.

RESULTS

Environmental scanning electron microscopy followed by x-ray microanalysis revealed an organic biofilm on the surface of the IOL.

CONCLUSIONS

To our knowledge, this is the first reported case in which the material deposited on the lens is organic rather than calcific.

Lens status influences the association between CFH polymorphisms and age-related macular degeneration: findings from two population-based studies in Singapore

Aims

To determine the differential effects of genetic polymorphism in CFH and ARMS2 on risk of age-related macular degeneration (AMD) between phakic vs. pseudophakic/aphakic eyes.

Methods

9,529 eyes of 4,918 participants from the Singapore Malay Eye Study and Singapore Indian Eye Study were analyzed. Participants had detailed eye examinations, including slit-lamp examinations and dilated fundus photography. AMD grading was performed according to the Wisconsin age-related maculopathy grading system. Lens status was defined. Single nucleotide polymorphisms (SNPs) rs10801555 (Y402H) within CFH and rs3750847 in ARMS2 were assessed. The main outcome measure was early AMD or any AMD.

Results

No significant associations between the CFH Y402H genotypes and early AMD were found in phakic individuals. In contrast, among pseudophakic/aphakic individuals, the CFH Y402H risk genotypes were significantly associated with higher odds of early AMD, with an OR of 1.57 (95% CI: 1.07–2.29) for GA genotype and 2.40 (95% CI: 1.25–4.61) for AA genotype, compared to those with GG genotype. There was significant interaction between pseudophakic/aphakic status and CFH Y402H variant on risk of early AMD (p = 0.037), adjusting for age, gender, and the first 5 genetic principal components. No significant interaction was found between lens status and ARMS2 rs3750847.

Conclusions

CFH genetic polymorphism and pseudophakic/aphakic status may have a potential synergistic effect on early AMD, suggesting roles for the complement system and related pathways in the pathogenesis of AMD in eyes after cataract surgery.

Hydrated polysaccharide multilayer as an intraocular lens surface coating for biocompatibility improvements

A swollen polysaccharide multilayer was coated on an IOL to inhibit LEC adhesion and proliferation, thus decreasing PCO incidence after implantation.

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.

[Posterior capsule opacification, capsular bag distension syndrome, and anterior capsular phimosis: A retrospective cohort study]

OBJECTIVE

To determine the incidence and the risk factors involved in the development of the three main postoperative capsular complications: posterior capsule opacification (PCO), capsular bag distension syndrome (CBDS), and anterior capsular phimosis syndrome (ACP).

SUBJECTS, MATERIAL AND METHODS

A retrospective cohort study was conducted on 801 patients submitted to cataract surgery in the ophthalmology unit of Hospital del Henares (Madrid) from March 2, 2009 to February 28, 2010. Computerized clinical charts were reviewed during July 2012. PCO was studied using the Kaplan-Meier method (log rank test).

RESULTS

A total of 167 patients developed PCO. No association could be demonstrated between PCO and age, sex, diabetes mellitus, phaco technique, IOL model, tamsulosin intake, glaucoma, and age-related macular degeneration. Three patients developed CBDS, all of them have received and Akreos Adapt AO(®) (Bausch & Lomb). Two of them were young men who had received surgery for posterior subcapsular cataracts. Three patients developed ACP, 2 of whom had received a MicroSlim(®) IOL (PhysIOL).

CONCLUSIONS

No association was found between PCO and any of the studied variables. Male gender, young age, subcapsular cataract and large non-angulated lens such as Akreos Adapt AO(®) could be associated with CBDS. ACP could be more frequent when microincision IOLs (like MicroSlim(®)) are implanted.

Capsular contracture by silicone breast implants: possible causes, biocompatibility, and prophylactic strategies

The most common implanted material in the human body consists of silicone. Breast augmentation and breast reconstruction using silicone-based implants are procedures frequently performed by reconstructive and aesthetic surgeons. A main complication of this procedure continues to be the development of capsular contracture (CC), displaying the result of a fibrotic foreign body reaction after the implantation of silicone. For many years, experimental and clinical trials have attempted to analyze the problem of its etiology, treatment, and prophylaxis. Different theories of CC formation are known; however, the reason why different individuals develop CC in days or a month, or only after years, is unknown. Therefore, we hypothesize that CC formation, might primarily be induced by immunological mechanisms along with other reasons. This article attempts to review CC formation, with special attention paid to immunological and inflammatory reasons, as well as actual prophylactic strategies. In this context, the word “biocompatibility” has been frequently used to describe the overall biological innocuousness of silicone in the respective studies, although without clear-cut definitions of this important feature. We have therefore developed a new five-point scale with distinct key points of biocompatibility. Hence, this article might provide the basis for ongoing discussion in this field to reduce single-publication definitions as well as increase the understanding of biocompatibility.

Drug/Medical Device Combination Products with Stimuli-responsive Eluting Surface

Drug-eluting medical devices are designed to improve the primary function of the device and at the same time offer local release of drugs which otherwise might find it difficult to reach the insertion/implantation site. The incorporation of the drug enables the tuning of the host/microbial responses to the device and the management of device-related complications. On the other hand, the medical device acts as platform for the delivery of the drug for a prolonged period of time just at the site where it is needed and, consequently, the efficacy and the safety of the treatment, as well as its cost-effectiveness are improved. This chapter begins with an introduction to the combination products and then focuses on the techniques available (compounding, impregnation, coating, grafting of the drug or of polymers that interact with it) to endow medical devices with the ability to host drugs/biological products and to regulate their release. Furthermore, the methods for surface modification with stimuli-responsive polymers or networks are analyzed in detail and the performance of the modified materials as drug-delivery systems is discussed. A wide range of chemical-, irradiation- and plasma-based techniques for grafting of brushes and networks that are sensitive to changes in temperature, pH, light, ionic strength or concentration of certain biomarkers, from a variety of substrate materials, is currently available. Although in vivo tests are still limited, such a surface functionalization of medical devices has already been shown useful for the release on-demand of drugs and biological products, being switchable on/off as a function of the progression of certain physiological or pathological events (e.g. healing, body integration, biofouling or biofilm formation). Improved knowledge of the interactions among the medical device, the functionalized surface, the drug and the body are expected to pave the way to the design of drug-eluting medical devices with optimized and novel performances.

Posterior capsule opacification following 20- and 23-gauge phacovitrectomy (posterior capsule opacification following phacovitrectomy)

PURPOSE

To compare the development of posterior capsule opacification (PCO) for idiopathic epi-retinal membrane cases between 20- and 23-gauge phacovitrectomy.

METHODS

Cataract surgery of phacoemulsification with the SA60AT implantation and 20- or 23-gauge vitrectomy was performed for 20 patients in both groups. Cataract surgery alone was performed for 50 patients as the control. The PCO density values were measured using Scheimpflug video photography at 1 week, 1, 3, 6, 12, 18, and 24 months after surgery. The number of eyes that required Nd:YAG laser capsulotomy was also examined.

RESULTS

The mean PCO value in the 20-gauge phacovitrectomy group increased significantly with time (P<0.001), whereas those in the 23-gauge phacovitrectomy group and the cataract surgery group did not show any significant change. Furthermore, the PCO value in the 20-gauge phacovitrectomy group was significantly greater than that in the 23-gauge phacovitrectomy group at 6, 12, 18 (P<0.05), and 24 months (P<0.01) after surgery. The PCO value in the 23-gauge phacovitrectomy group was significantly greater than that in the cataract surgery group 24 months after surgery (P<0.05). The rate of capsulotomy in the 20-gauge phacovitrectomy group was significantly higher than that in the cataract surgery group (P=0.007), whereas there was no significant difference between the 23-gauge phacovitrectomy group and the cataract surgery group.

CONCLUSION

PCO rate in eyes with the 23-gauge phacovitrectomy was lower than in those with the 20-gauge phacovitrectomy, and PCO rate even in the 23-gauge phacovitrectomy was higher than in those with cataract surgery.

Study on the surface properties of surface modified silicone intraocular lenses

AIM

To prepare a new-type soft intraocular lens (IOL) that silicone intraocular lenses (IOLs) were modified by surface modification technique to assess IOLs biocompatibility.

METHODS

With the technique of ion beam combined with low temperature and low pressure plasma, the surface characteristics of the IOLs including physical and optical properties were determined by the instruments of IOLs resolution, UV/VIS scanning spectrophotometer, contact angle measurement system, electron spectroscopy for chemical analysis (ESCA) and scanning electron microscope (SEM).

RESULTS

The color of titanium (Ti) modified IOLs was light yellow and that of titanium nitride (TiN) modified IOLs was light brown. The absorptive degree of ultraviolet rays and the hydrophilicity of the surfaces of modified IOLs were increased, and appeared suitable chemical compositions. The resolution of unmodified and modified IOLs reached normal standard. The surfaces of unmodified and Ti-modified IOLs appeared uniform. The surfaces of TiN-modified IOLs presented fine porcelain structure.

CONCLUSION

The optical properties of all IOLs and the surface morphology of the modified IOLs were not affected by modification processes. The surface properties of the modified IOLs were improved.

Postcataract surgical inflammation

PURPOSE OF REVIEW

To describe the epidemiology, pathogenesis, and recent developments in the diagnosis and management of postcataract surgery inflammation.

RECENT FINDINGS

In patients with pre-existing uveitis, control of inflammation with topical and/or systemic therapy for 3 months preoperatively continues to be important in lessening the risk of postoperative inflammation and complications. During cataract surgery, intraocular lens selection in these patients is important. Recent literature suggests that modern intraocular lenses (IOLs), particularly hydrophilic or hydrophobic acrylic lenses, generally have good uveal biocompatibility in uveitic patients. The postoperative course can be complicated by inflammation and cystoid macular edema (CME), and in uveitic patients, intensive perioperative steroid treatment can lessen these complications. Recent studies show that in uveitic patients, the improvement in CME and inflammation after intravitreal triamcinolone is better than after orbital floor triamcinolone injection, but that a single intraoperative orbital floor injection of triamcinolone is as effective as a 4-week course of postoperative oral prednisolone. Although postoperative inflammation in uveitic patients may be due to recurrence of uveitis, one must recognize other important potential causes of postoperative inflammation and treat accordingly.

SUMMARY

Most patients with postcataract inflammation have good visual outcomes provided that the cause is recognized and that there is adequate perioperative planning in patients predisposed to inflammation.

[Phacoemulsification and acrylic intraocular lens in uveitis: a comparative study]

OBJECTIVE

To describe the outcomes of phacoemulsification with the implant of an acrylic intraocular lens (IOL) in cataracts of adult patients with and without uveitis

METHODS

Descriptive retrospective comparative study of 35 patients (45 eyes) with uveitis (group 1) and 38 (44 eyes) control patients (group 2), who were operated on by the same surgeon, and were homogeneous as regards sex, surgical technique, IOL (hydrophobic or hydrophilic) and follow-up. The pre-surgical characteristics of risk, the difficulties and intra-surgical and postsurgical complications, the date of posterior capsulotomy (PC) and the pre- and post-surgical visual acuity (VA), were analysed.

RESULTS

In both groups the coaxial phacoemulsification was used in 75% of the eyes, bimanual microincision cataract surgery (MICS) in 20% and micro-coaxial in the rest. The pre-surgical risk factors (P = .002, OR 6.83), the surgical difficulties and complications (P = .001, OR 7.54) and postsurgical complications (P = .069, OR 3.42) were more frequent in the uveitis group. In both 93% and 91% respectively of eyes improved 2 or more lines of VA. After an average follow-up of 4.9 years in both groups, 22.7% and 32% eyes (log-rank P = .357) needed PC. The hydrophilic IOLs needed PC earlier than the hydrophobic ones (log rank P = .001), neither the location nor the uveitis course influenced the PC rate.

CONCLUSIONS

The consequences because of previous ocular inflammation make cataract surgery in uveitis more difficult, but with postsurgical complications, visual results and need of PC similar to our patients without inflammation.

Drug-Eluting Intraocular Lenses

Notable advances in materials science and in surgical techniques make the management of cataract by replacement of the opaque crystalline with an intraocular lens (IOL), one of the most cost-effective interventions in current healthcare. The usefulness and safety of IOLs can be enhanced if they are endowed with the ability to load and to sustain drug release in the implantation site. Drug-eluting IOLs can prevent infections and untoward reactions of eye tissues (which lead to opacification) and also can act as drug depots for treatment of several other ocular pathologies. Such a myriad of therapeutic possibilities has prompted the design of drug-IOL combination products. Several approaches are under study, namely combination of the IOL with an insert in a single device, soaking in drug solutions, impregnation using supercritical fluids, coating with drug/polymer layers, and covalent grafting of the drug. The advantages/limitations of each technique are discussed in the present review on selected examples. Although more in vivo data are required, the information already available proves the interest of some approaches in ocular therapeutics.

F-heparin modified intraocular lenses in Rhesus monkeys

AIM

In order to improve the biocompatibility of intraocular lenses (IOL), the polymethylmethacrylate (PMMA) IOL was modified with F-heparin.

METHODS

The PMMA IOL was modified with F ions and heparin by the technique of ion beam combined with low temperature and low pressure plasma. The monkeys (20 eyes) with cataract partly were randomly classified into 2 groups and implanted with PMMA IOL and modified IOL respectively for 180 days. All of the eyes were examined by slit-lamp microscope at postoperative 15, 30, 60, 90, 180 days. The extracted IOL was analyzed with computer image analysis, light microscope (LM) and scanning electron microscope (SEM) at postoperative 180 days.

RESULTS

The early inflammatory reactions postoperatively include anterior chamber exudation and aqueous cell count. The modified IOL group showed less than the non-modified IOL group. The late foreign body cell reaction that adhered to the surface of non-modified IOL was more predominant. The morphologic and pathological changes of posterior capsule opacification (PCO) in monkeys' eyes included fibrosis-type, pearl-type and soemmerring's ring. There was a significant difference between the two groups.

CONCLUSION

F-heparin modified IOL has good uveal and capsular biocompatibility.