Intraocular lens materials and styles: a review

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.

Optical Quality Variation of Different Intraocular Lens Designs in a Model Eye: Lens Placed Correctly and in an Upside-Down Position

INTRODUCTION

Intraocular lenses (IOLs) may lose their optical quality if they are not correctly placed inside the capsular bag once implanted. One possible malpositioning of the IOL could be the implantation in an upside-down position. In this work, three aspheric IOLs with different spherical aberration (SA) have been designed and numerically tested to analyse the optical quality variation with the IOL flip, and misalignments, using a theoretical model eye.

METHODS

Using the commercial optical design software OSLO, the effect of decentration and tilt was evaluated by numerical ray tracing in two conditions: in their designed position and flipped with respect to the planned position (IOL is implanted upside down). The theoretical model eye used was the Atchison model eye. Seven IOL designs of +27.00 diopters were used: a lens with negative SA to correct the corneal SA, a lens to partially correct the corneal SA, and a lens to not add any SA to the cornea (aberration-free IOL). These lenses were designed with the aspherical surface located on the anterior and posterior IOL surface. A lens with no aspherical surfaces was also included. For the optical quality analysis, the modulation transfer function (MTF) was used, together with the Zernike wavefront aberration coefficients of defocus, astigmatism, and primary coma.

RESULTS

Off-centring and tilting the IOL reduced overall MTF values and increased wavefront aberration errors. With the IOL correctly positioned within the capsular bag, an aberration-free IOL is the best choice for maintaining optical quality. When the IOL is flipped inside the capsular bag, the optical quality changes, with the aberration-free IOL and the IOL without aspheric surfaces providing the worst results. With the lens in an upside-down position, an IOL design to partially correct corneal SA shows the best optical quality results in decentration and tilt, in terms of MTF and wavefront aberrations.

CONCLUSION

The aberration-free IOL is the best choice when minimal postoperative errors of decentration or tilt are predicted. With IOL flip, the negative SA lens design is the best choice, regarding the root mean square wavefront aberrations. However, in a proper IOL implantation, the IOL designed to partially compensate the corneal SA including asphericity on its posterior surface is the better possible option, even in the presence of decentration or tilt.

Effect of decentration, tilt and rotation on the optical quality of various toric intraocular lens designs: a numerical and experimental study

Toric intraocular lenses (T-IOLs) may lose their optical quality if they are not correctly positioned inside the capsular bag once implanted. In this work, T-IOLs with cylinder powers of +1.50, +4.50 and +7.50 D and differing degrees of spherical aberration have been designed, manufactured and tested in vitro using a commercial optical bench that complies with the requirements of standard ISO 11979-2. Moreover, the effect of tilt and rotation on optical quality was assessed by means of numerical ray tracing on an astigmatic eye model, while the effect of decentration was evaluated numerically and experimentally.

Application of Collagen I and IV in Bioengineering Transparent Ocular Tissues

Collagens represent a major group of structural proteins expressed in different tissues and display distinct and variable properties. Whilst collagens are non-transparent in the skin, they confer transparency in the cornea and crystalline lens of the eye. There are 28 types of collagen that all share a common triple helix structure yet differ in the composition of their α-chains leading to their different properties. The different organization of collagen fibers also contributes to the variable tissue morphology. The important ability of collagen to form different tissues has led to the exploration and application of collagen as a biomaterial. Collagen type I (Col-I) and collagen type IV (Col-IV) are the two primary collagens found in corneal and lens tissues. Both collagens provide structure and transparency, essential for a clear vision. This review explores the application of these two collagen types as novel biomaterials in bioengineering unique tissue that could be used to treat a variety of ocular diseases leading to blindness.

Delayed surface opacification of a hydroview intraocular lens

The insertion of an intraocular lens during cataract surgery is routine but delayed opacification of hydrophilic foldable intraocular lenses (IOLs) has been increasingly noticed as a late post-operative complication. Such opacification may present with reduced visual acuity and can be diagnosed with slitlamp biomicroscopy. Lens explantation may be required. We report an 89-year-old female presenting with opacification of a Hydroview IOL and correlate the clinical findings of the lens in situ with the light microscopy of the explanted lens, as well as transmission electron microscopy (TEM), scanning electron microscopy (SEM) and elemental analysis. Pathological analysis of an explanted IOL may assist in a better understanding of the condition and may become relevant in medico-legal proceedings.

Polymeric Materials for Eye Surface and Intraocular Applications

Ocular applications of polymeric materials have been widely investigated for medical diagnostics, treatment, and vision improvement. The human eye is a vital organ that connects us to the outside world so when the eye is injured, infected, or impaired, it needs immediate medical treatment to maintain clear vision and quality of life. Moreover, several essential parts of the eye lose their functions upon aging, causing diminished vision. Modern polymer science and polymeric materials offer various alternatives, such as corneal and scleral implants, artificial ocular lenses, and vitreous substitutes, to replace the damaged parts of the eye. In addition to the use of polymers for medical treatment, polymeric contact lenses can provide not only vision correction, but they can also be used as wearable electronics. In this Review, we highlight the evolution of polymeric materials for specific ocular applications such as intraocular lenses and current state-of-the-art polymeric systems with unique properties for contact lens, corneal, scleral, and vitreous body applications. We organize this Review paper by following the path of light as it travels through the eye. Starting from the outside of the eye (contact lenses), we move onto the eye's surface (cornea and sclera) and conclude with intraocular applications (intraocular lens and vitreous body) of mostly synthetic polymers and several biopolymers. Initially, we briefly describe the anatomy and physiology of the eye as a reminder of the eye parts and their functions. The rest of the Review provides an overview of recent advancements in next-generation contact lenses and contact lens sensors, corneal and scleral implants, solid and injectable intraocular lenses, and artificial vitreous body. Current limitations for future improvements are also briefly discussed.

Antibacterial Coatings for Improving the Performance of Biomaterials

Biomedical devices have become essential in the health care. Every day, an enormous number of these devices are used or implanted in humans. In this context, the bacterial contamination that could be developed in implanted devices is critical since it is estimated that infections kill more people than other medical causes. Commonly, these infections are treated with antibiotics, but the biofilm formation on implant surfaces could significantly reduce the effectiveness of these antibiotics since bacteria inside the biofilm is protected from the drug. In some cases, a complete removal of the implant is necessary in order to overcome the infection. In this context, antibacterial coatings are considered an excellent strategy to avoid biofilm formation and, therefore, mitigate the derived complications. In this review, the main biomaterials used in biomedical devices, the mechanism of biofilm formation, and the main strategies for the development of antibacterial coatings, are reviewed. Finally, the main polymer-based strategies to develop antibacterial coatings are summarized, with the aim of these coatings being to avoid the bacteria proliferation by controlling the antibacterial mechanisms involved and enhancing long-term stability.

Ionizing Radiation for Preparation and Functionalization of Membranes and Their Biomedical and Environmental Applications

The use of ionizing radiation processing technologies has proven to be one of the most versatile ways to prepare a wide range of membranes with specific tailored functionalities, thus enabling them to be used in a variety of industrial, environmental, and biological applications. The general principle of this clean and environmental friendly technique is the use of various types of commercially available high-energy radiation sources, like ⁶⁰Co, X-ray, and electron beam to initiate energy-controlled processes of free-radical polymerization or copolymerization, leading to the production of functionalized, flexible, structured membranes or to the incorporation of functional groups within a matrix composed by a low-cost polymer film. The present manuscript describes the state of the art of using ionizing radiation for the preparation and functionalization of polymer-based membranes for biomedical and environmental applications.

Comparison of two devices to simulate vision with intraocular lenses

Introduction

The simulation of vision with intraocular lenses (IOLs) prior to the clinical validation is of great interest for manufacturers as well as clinicians. We have tested the influence of different IOLs on the perception of contrast using different devices.

Materials and methods

A Rassow telescope and the VirtIOL have been used to assess the contrast sensitivity function (CSF) through monfocal IOL (CT Asphina 409 MP, IOL 1), multifocal IOL (AT LISA tri 839 MP, IOL 2) and extended-depth-of-focus-IOL (TECNIS Symfony ZXR00, IOL3) in 21 participants, aged between 22 and 29 years. Contrast sensitivity (CS) was tested at various spatial frequencies (3–30 cycles per degree), using the Tuebingen contrast sensitivity test.

Results

All tested IOL reduced the CS when compared to measurements with a trial lens correction of refractive errors. The analysis of the area under the curve of the contrast sensitivity function (AUC-CSF) revealed a significant reduction compared to the trial lens correction in case the Rassow telescope was used (IOL 1: P=0.008; IOL2: P<0.001; IOL3: P<0.001) and the same was true for the VirtIOL device for IOL2 and IOL3 (IOL2: P<0.001; IOL3: P<0.001), but not for IOL1 (P=0.192). Interdevice analysis of the AUC-CSF revealed significant differences for IOL1 and IOL2 (IOL1: P=0.025; IOL2: P<0.001), while no difference was found for IOL3 (P=0.092). Bland–Altman analysis as well as intraclass correlations coefficients indicated only weak interdevice agreement for the tested IOL.

Conclusion

The assessment of the interdevice analysis for the Rassow telescope and the VirtIOL device revealed only a minor agreement between the two devices. In order to investigate vision with IOLs prior to a clinical validation, the use of the VirtIOL device is recommended.

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.

Refractive outcomes in nanophthalmic eyes after phacoemulsification and implantation of a high-refractive-power foldable intraocular lens

PURPOSE

To evaluate the refractive and postoperative outcomes of a high-power foldable intraocular lens (IOL) in nanophthalmic eyes.

SETTING

Six ophthalmic surgical centers in Canada.

DESIGN

Retrospective case series.

METHODS

Consecutive charts of nanophthalmic patients having cataract extraction and insertion of the CT Xtreme D IOL were reviewed. Demographic and clinical data were collected, including age, sex, axial length (AL), minimum keratometry (K) value and maximum K value, corneal white-to-white (WTW), anterior chamber depth, lens thickness (LT), and complications. The following preoperative and operative data were collected: uncorrected distant visual acuity (UDVA), corrected distant visual acuity (CDVA), sphere, cylinder, and spherical equivalence (SE). The primary outcome measure was change in SE. The secondary outcome measures were changes in UDVA and CDVA.

RESULTS

A total of 21 eyes from 13 patients with a mean follow-up time of 9.6 ± 8.5 months were studied. Mean preoperative data were: age (51.4 ± 15.2 years), AL (16.63 ± 0.68 mm), minimum K value (46.20 ± 2.26 D), maximum K value (47.55 ± 2.34 D), anterior chamber depth (2.60 ± 0.49 mm), WTW (11.08 ± 1.38 mm), LT (4.70 ± 0.97 mm), and IOL power implanted (+49.9 ± 3.3 diopters [D]). SE improved from +16.11 ± 3.26 D preoperatively to +2.00 ± 2.37 D postoperatively (P < .0001). UDVA improved from 1.47 ± 0.30 logMAR preoperatively to 0.74 ± 0.43 logMAR postoperatively (P = .016). CDVA did not change significantly. Five eyes (23.8%) had serious postoperative complications. Of these eyes, 2 had malignant glaucoma, 2 had vitreous hemorrhages, and 1 eye had a vitreous hemorrhage with retinal detachment resulting in visual acuity of no light perception.

CONCLUSION

Implanting foldable high-power IOLs in a series of nanophthalmic eyes yielded significant improvement in UDVA and SE. Cataract surgery in these eyes carries increased risk.

FINANCIAL DISCLOSURE

Iqbal Ike K. Ahmed is a consultant to Carl Zeiss Meditec AG. No other author has a financial or proprietary interest in any material or method mentioned.

Posterior Capsule Opacification 9 Years after Phacoemulsification with a Hydrophobic and a Hydrophilic Intraocular Lens

Purpose

To compare the development of posterior capsule opacification (PCO) and survival rate without capsulotomy after implantation of a hydrophobic or hydrophilic acrylic intraocular lens (IOL) at the 9-year postoperative follow-up.

Methods

One of 3 experienced cataract surgeons performed standard phacoemulsification in one eye of 120 patients with cataract. The patients were randomized to implantation of either a hydrophobic acrylic IOL or a hydrophilic acrylic IOL. Both IOLs had sharp posterior edges. Retroillumination images of PCO were obtained with a fundus camera 9 years postoperatively and analyzed semiobjectively using POCOman computer software.

Results

Seventy-eight of the 120 patients completed the 9-year follow-up examination. Patients implanted with the hydrophilic IOL had significantly (p<0.001) more and denser PCO. The survival rate without Nd:YAG capsulotomy was significantly higher (p<0.001) in eyes with the hydrophobic IOL.

Conclusions

After 9 years, more and denser PCO developed in eyes with the hydrophilic IOL than the hydrophobic IOL. The survival rate without the need for capsulotomy was higher in eyes with the hydrophobic IOL.

Fast in situ enzymatic gelation of PPO-PEO block copolymer for injectable intraocular lens in vivo

Foldable intraocular lenses (IOLs) have been utilized to substitute natural lens of cataract patients. In this study, we developed a fast, in situ gelable hydrogel requiring no toxic agent as an injectable IOL material. A 4-armed PPO/PEO-phenol conjugate by a non-degradable linker was synthesized to form a hydrogel in situ by horseradish peroxidase. The gelation time and modulus could be controlled, ranging from 20 s to 2 min and from 1 to 43 kPa. The adhesion of human lens epithelial cells on the hydrogel was significantly reduced compared to that on commercial IOLs. The hydrogels were injected into the rabbit eyes to evaluate the in vivo biocompatibility for 8 weeks. Corneal endothelial cell loss and central corneal thickness were comparable with the common IOL implantation procedure. Histologically, the cornea and retina showed the intact structure. The change of refraction after application of pilocarpine was +0.42 D preoperatively and +0.83 D postoperatively, which may indicate the maintenance of accommodation amplitude.

Synthesis, characterization, and in vitro evaluation of a hydrogel-based corneal onlay

Blindness due to opacity of the cornea is treated by corneal transplantation with donor tissue. Due to the limited supply of suitable donor corneas, the need for synthetic corneal equivalents is clear. Herein we report the design and in vitro characterization of a hydrogel-based implant; this implant will serve as a permanent, transparent, space-filling onlay with a two-layer design that mimics the native corneal stratification to support surface epithelialization and foster integration with the surrounding tissue. The top layer of the implant was composed of a 2-hydroxyethylmethacrylate hydrogel containing methacrylic acid as the co-monomer (HEMA-co-MAA) with tunable dimensions and compressive modulus ranging from 700-1000 kPa. The bottom layer, which constitutes the bulk of the implant and is designed to provide integration with the corneal stroma, is a dendrimer hydrogel with high water content and compressive modulus ranging from 500-1200 kPa. Both hydrogels were found to possess optical and diffusion properties similar to those of the human cornea. In addition, composite implants with uniform and structurally sound interfaces were formed when the gels were sequentially injected and cross-linked in the same mold. HEMA-co-MAA hydrogels were covalently modified with type I collagen to enable corneal epithelial cell adhesion and spreading that was dependent upon the collagen coating density but independent of hydrogel stiffness. Similarly, dendrimer hydrogels supported the adhesion and spreading of corneal fibroblasts upon modification with the adhesion ligand arginine-glycine-aspartic acid (RGD). Fibroblast adhesion was not dependent upon dendrimer hydrogel stiffness for the formulations studied and, after in vitro culture for 4 weeks, fibroblasts remained able to adhere to and conformally coat the hydrogel surface. In conclusion, the tunable physical properties and structural integrity of the laminated interface suggests that this design is suitable for further study. The judicious tuning of material properties and inclusion of bioactive moieties is a promising strategy for promotion of implant epithelialization and tissue integration.

Spectral analysis and comparison of mineral deposits forming in opacified intraocular lens and senile cataractous lens

This preliminary report was attempted to compare the chemical components of mineral deposits on the surfaces of an opacified intraocular lens (IOL) and a calcified senile cataractous lens (SCL) by vibrational spectral diagnosis. An opacified intraocular lens (IOL) was obtained from a 65-year-old male patient who had a significant decrease in visual acuity 2-years after an ocular IOL implantation. Another SCL with grayish white calcified plaque on the subcapsular cortex was isolated from a 79-year-old male patient with complicated cataract after cataract surgery. Optical light microscope was used to observe both samples and gross pictures were taken. Fourier transform infrared (FT-IR) and Raman microspectroscopic techniques were employed to analyze the calcified deposits. The curve-fitting algorithm using the Gaussian function was also used to quantitatively estimate the chemical components in each deposit. The preliminary results of spectral diagnosis indicate that the opacified IOL mainly consisted of the poorly crystalline, immature non-stoichiometric hydroxyapatite (HA) with higher content of type B carbonated apatites. However, the calcified plaque deposited on the SCL was comprised of a mature crystalline stoichiometric HA having higher contents of type A and type B carbonate apatites. More case studies should be examined in future.

Determination of albumin sorption to intraocular lenses by radiolabeling and confocal laser scanning microscopy

PURPOSE

To determine albumin adsorption profiles and penetration depth of 3 intraocular lens (IOL) materials over time using confocal laser scanning microscopy (CLSM) and radiolabeling.

SETTING

Centre for Contact Lens Research, School of Optometry, and Department of Biology, University of Waterloo, Waterloo, Ontario, Canada.

METHODS

Poly(methyl methacrylate) (PMMA), silicone, and foldable hydrophilic acrylic IOLs were incubated in 0.5 mg/mL bovine serum albumin (BSA) for 1, 7, and 14 days. The BSA was conjugated with lucifer yellow VS to allow identification of the protein location by fluorescent imaging with CLSM. Next, the protein uptake was quantified using 2% (125)I-labeled BSA.

RESULTS

Confocal laser scanning microscopy showed increasing BSA uptake for silicone and PMMA IOLs after 14 days of incubation (P<.05), with an apparent penetration depth of 8.7 microm +/- 1.9 (SD) and 9.2 +/- 1.4 microm, respectively. For hydrophilic acrylic IOLs, BSA was detected at a depth of 38 +/- 7.4 microm after 1 day, followed by an increase to 192.7 +/- 16.2 microm after 14 days. Despite the penetration depth into the hydrophilic acrylic IOLs, quantitative results confirmed that PMMA and hydrophilic acrylic deposited significantly less BSA (mean 278.3 +/- 41.7 ng and 296.5 +/- 33.1 ng, respectively) than silicone IOLs (mean 392.6 +/- 37.6 ng) (P<.05).

CONCLUSIONS

Silicone and PMMA IOL materials showed BSA sorption near the lens surface only, while BSA penetrated deep into the hydrophilic acrylic IOL matrix. Combining the qualitative CLSM method and quantitative radiolabeling technique provided detailed information on protein interactions with implantable biomaterials.

Hydrogels for tissue engineering and delivery of tissue-inducing substances

This manuscript presents hydrogels (HGs) from a tissue engineering perspective being especially written for those who are approaching this field by offering a concise but inclusive review of hydrogel synthesis, properties, characterization methods, and applications.

Two opacification patterns of the same hydrophilic acrylic polymer: case reports and clinicopathological correlation

We report 2 intraocular lenses (IOLs) manufactured from the same hydrophilic acrylic polymer by Ioltech that developed optic opacification. In both cases, the postoperative course after implantation of the IOLs was complicated by significant inflammatory reaction with fibrin formation in the anterior chamber. Pathologic analyses of the explanted IOLs were consistent with dystrophic calcification leading to optic opacification, but the pattern was different between the 2 IOL designs. Patient-related factors might have been responsible for this complication.

Biocompatibility testing of novel multifunctional polymeric biomaterials for tissue engineering applications in head and neck surgery: an overview

Biomaterial research and tissue engineering are rapidly growing scientific fields that need an interdisciplinary approach where clinicians should be included from the onset. Biocompatibility testing in vitro and in vivo comprise the agarose-overlay test, the MTT test, direct cell seeding tests and the chorioallantoic membrane test for angiogenic effects, among others. Molecular biology techniques such as real-time polymerase chain reaction and microarray technology facilitate the investigation of tissue integration into biomaterials on a cellular and molecular level. The physicochemical characterization of biomaterials is conducted using such methods as X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). Excellent biocompatibility and biofunctionality were demonstrated for a series of recently developed multifunctional biodegradable, polymeric biomaterials both in vitro and in vivo. Novel, multifunctional polymeric biomaterials offer a highly specific adjustment to the physiological, anatomical and surgical requirements and can thereby facilitate new therapeutic options in head and neck surgery.

Free volume study on calcification process in an intraocular lens after cataract surgery

An opacified intraocular lens explanted from a patient in the postoperative period after phacoemulsification was investigated to find the cause of opacification. From the UV-visible and energy dispersive X-ray spectroscopy (EDS) measurements, the opacification in the present case seems to be due to calcification of the intraocular lens and not due to modification in the UV absorber material of the lens. The average free volume size of the intraocular lens both in unimplanted and explanted state were obtained from positron lifetime spectroscopy (PLS). Further, the combined FTIR and PLS results indicate that calcium gets into the free volume cavities of the intraocular lens matrix as a cationic moiety, may be in the form of Ca(++). The small decrease in glass transition temperature of the calcified lens seems to indicate the plasticizing action of calcium ions. The present results could be of some use in the design of the intraocular lens material in which calcification would be minimum.

Calcification of intraocular hydrogel lens: evidence of dystrophic calcification

PURPOSE

To report and describe the surface calcification of three cases of implanted intraocular hydrogel lens.

METHODS

Three surgically extracted hydrogel intraocular lenses were studied by light and transmission electron microscopy as well as by energy dispersion X-ray microanalysis.

RESULTS

The lens surfaces were covered by granular deposits of calcium phosphate, clearly delineated by von Kossa and alizarin stains for calcium. Transmission electron microscopy showed the deposits to be located within the superficial lens material to a depth of 7 microm and to be associated with what appear to be traces of cellular material including basement membrane and plasmalemma. To the authors' knowledge there has been only one other transmission electron microscopic study. Energy dispersion X-ray microanalysis showed the deposits to contain calcium and phosphorous in all cases.

CONCLUSIONS

This study confirms and extends the previous reports of five cases of calcification of hydrogel intraocular lenses. The exact mechanism of calcification remains obscure but evidence suggesting cell-mediated dystrophic calcification of the lens surface is presented. Further study is required to monitor the incidence and development of this phenomenon.

Evidence of octacalcium phosphate and Type-B carbonated apatites deposited on the surface of explanted acrylic hydrogel intraocular lens

Fourier-transform infrared (FTIR) microspectroscopy combining with attenuated total reflection (ATR) microsampling technique and micro-Raman spectrophotometer were used to detect the deposited materials on the surface of acrylic hydrogel intraocular lens (IOL) with or without ocular implantation. Surface morphology and the interface of this IOL were further examined by a confocal laser scanning microscope. The brand-new IOL exhibited a very smooth, transparent and featureless surface, but the explanted IOL had an irregular cerebriform-like opaque appearance. Both FTIR/ATR and Raman microspectroscopic analyses showed the deposits on the surface of acrylic hydrogel IOL after ocular implantation to consist of octacalcium phosphate (OCP) and Type B carbonated apatites, leading to the opalescence of acrylic hydrogel IOL. Both vibrational microspectroscopic examinations also confirmed the mineralization still in progress on the surface of acrylic hydrogel IOL after ocular implantation for 2 years.

Calcification of modern foldable hydrogel intraocular lens designs

PURPOSE

To report and compare clinical and pathological features of hydrophilic acrylic intraocular lenses (IOLs) of three major designs, explanted from patients who had visual disturbances caused by opacification of the lens optic.

METHODS

Eighty-seven hydrophilic acrylic IOLs (25 Hydroview, 54 SC60B-OUV, and 8 Aqua-Sense lenses) were explanted and sent to our center. Most patients became symptomatic during the second year after cataract surgery. A fine granularity was observed on the surface of the lens optic in the case of Hydroview. With the SC60B-OUV and Aqua-Sense lenses, the opacity resembled a nuclear cataract. Gross examination, light microscopy and staining with alizarin red and the von Kossa method (for calcium) were performed. Some lenses were submitted for scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS).

RESULTS

Light microscopic and SEM analyses revealed the presence of irregular granular deposits on the external optical surfaces of Hydroview lenses. With the SC60B-OUV lenses, the opacity was caused by the presence of multiple fine, granular deposits within the lens optic, distributed in a line parallel to the anterior and posterior curvatures of the optic, with a clear zone just beneath its external surfaces. The Aqua-Sense lenses exhibited both patterns simultaneously. The deposits in all cases stained positive with alizarin red and von Kossa method. EDS also demonstrated the presence of calcium and phosphates within the deposits.

CONCLUSION

Differences in the water content of the hydrophilic acrylic materials used in the manufacture of these three lens designs may be responsible for the different patterns of calcium precipitation. Careful clinical follow up of patients implanted with these lenses is necessary to determine if this phenomenon is rare and sporadic or may be more widespread.

Ripple-like intraocular lens damage from a neodymium:YAG laser

We report a case of accidental intraocular lens (IOL) damage during a neodymium:YAG laser capsulotomy. After a single pulse of 0.9 mJ of laser energy, a large area of ripple-like opacity with more than 10 concentric circles surrounding a small hole in a 2.0 diopter IOL was noted. The opacity extended more than one fourth of the IOL diameter and caused a significant visual effect.

Hydrophilic acrylic intraocular lens optic and haptics opacification in a diabetic patient: bilateral case report and clinicopathologic correlation

OBJECTIVE

To report clinicopathologic and ultrastructural features of two opacified single-piece hydrophilic acrylic intraocular lenses (IOLs) explanted from a diabetic patient.

DESIGN

Interventional case report with clinicopathologic correlation.

SETTING

A 64-year-old white female underwent phacoemulsification and implantation of a single-piece hydrophilic acrylic lens (SC60B-OUV; Medical Developmental Research, Inc., Clear Water, FL) in October 1998 in the left eye and in July 1999 in the right eye. The best-corrected visual acuity after surgery was 20/60 in the left eye and 20/50 in the right eye. The patient had a marked decrease in visual acuity in June 2000 as a result of a milky, white opalescence of both lenses. Intraocular lens explantation and exchange was performed in both eyes and the explanted IOLs were submitted to our center for detailed pathologic, histochemical, and ultrastructural evaluation. They were stained with alizarin red and the von Kossa method for calcium, and also underwent scanning electron microscopy and energy dispersive radiograph spectroscopy to ascertain the nature of the deposits leading to opacification.

MAIN OUTCOME MEASURES

Documentation of calcium deposits confirmed by histochemical stains and surface analyses.

RESULTS

Opacification of the IOL was found to be the cause of decreased visual acuity. The opacification involved both the IOL optic and the haptics in the left eye and was confined to the IOL optic in the right eye. Histochemical and ultrastructural analyses revealed that the opacity was caused by deposition of calcium and phosphate within the lens optic and haptics.

CONCLUSIONS

There are two features that distinguish this case from those reported earlier. This is the first clinicopathologic report of lens opacification that has involved completely the lens optic and the haptics. Second, these two explanted IOLs document the first bilateral case. This process of intraoptic and haptic opacification represents dystrophic calcification of unknown cause. Diabetic patients appear to be more severely and more often affected by lens opacification. Long-term follow-up of diabetic patients implanted with this IOL design should be maintained by surgeons and manufacturers.

Posterior capsule opacification and Nd:YAG capsulotomy rates after implantation of silicone, hydrogel and soft acrylic intraocular lenses: a two-year follow-up study

PURPOSE

To compare the posterior capsule opacification (PCO) and neodymium:YAG (Nd:YAG) laser posterior capsulotomy rates associated with three different posterior chamber foldable intraocular lenses (IOL).

METHODS

We retrospectively evaluated the rates of PCO and Nd:YAG laser capsulotomy in 1150 eyes two years after standard phacoemulsification with a no-stitch 3.5mm clear corneal incision (CCI) and in-the-bag implantation of one of three types of IOL: 190 eyes received a one-piece round-edged hydrogel IOL (Hydroview H60M, Bausch & Lomb); 475 eyes a three-piece round-edged silicone IOL (AMO PhacoFlex SI-40NB, Allergan); 485 eyes a three-piece square-edged soft acrylic lens (AcrySof MA60MA, Alcon).

RESULTS

The PCO and Nd:YAG laser capsulotomy rates were respectively 43.15% and 20.5% in the Hydroview H60M group, 27.57% and 9.68% in the AMO PhacoFlex SI-40NB group, 10.5% and 2.47% in the AcrySof MA60MA group.

CONCLUSIONS

PCO and Nd:YAG laser capsulotomy rates were significantly higher in the Hydroview H60M group and significantly lower with the AcrySof MA60MA lenses, which combine a bioactive constitutive material with the square-edged optic design.

Permanent blue discoloration of a hydrogel intraocular lens by intraoperative trypan blue

A 79-year-old white man had cataract surgery in the right eye with implantation of an Acqua intraocular lens (IOL) (Mediphacos). Trypan blue 0.1% was used during surgery to stain the anterior capsule and enhance the contrast during capsulorhexis. Seven days after surgery, the patient presented with "dark and double" vision (monocular diplopia). The IOL was decentered superiorly and appeared dark blue. The lens was explanted 2 months after surgery and sent for gross and microscopic analyses in a dry state and after hydration. The same analyses were performed on 2 unused lenses of the same design that had been immersed in diluted trypan blue solutions (0.01% and 0.001%). On the explanted lens, the dark blue staining was denser in the optic, especially in its periphery. The blue discoloration could not be removed after 24 hours of lens immersion in a balanced salt solution at 37 degrees C. Permanent staining of the unused lenses was also obtained after immersion in the trypan blue solutions.

Use of bipolar diathermy to prevent posterior capsule opacification(1)

PURPOSE

To determine the feasibility of using directed bipolar diathermy to eliminate or reduce the formation of new cortical lens material following phacoemulsification in a rabbit model.

SETTING

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

METHODS

A rabbit model for posterior capsule opacification (PCO) was used. A continuous curvilinear capsulorhexis was performed followed by phacoemulsification to remove cortical lens material. In 2 experimental groups, modified bipolar instruments were used to apply diathermy to residual lens epithelial cells using an intracapsular or extracapsular method of application. Postoperative clinical examinations were at 1, 3, and 7 days and then weekly up to 60 days. Selected animals were followed for a longer period. Capsule integrity was evaluated by measuring the pressure required to rupture the capsule in similarly treated porcine eyes.

RESULTS

Diathermy prevented PCO in 4 of 4 eyes in the intracapsular treatment group and 4 of 5 in the extracapsular group. Eyes remained free of new lens cortex for the life of the animal, which was as long as 18 months. New cortical material was detected after 35 days in 1 animal in the extracapsular group. Mean time for the formation of observable cortical material was 29 days +/- 5 (SD) in the control animals. Physical measurements did not detect a reduction in capsule integrity with diathermy treatment. The extracapsular treatment method resulted in fewer iris complications.

CONCLUSIONS

Directed diathermy has the potential to eliminate secondary cataract formation with minimal damage to collateral tissues.

Glistening formation in an AcrySof lens initiated by spinodal decomposition of the polymer network by temperature change

PURPOSE

To examine the effect of temperature change on the structural alteration and glistening formation in an AcrySof intraocular lens (IOL).

SETTING

Department of Chemical Science and Engineering, Faculty of Engineering, Kobe University, Kobe, Japan.

METHODS

The equilibrium water content of a Wagon-Wheel-packaged AcrySof IOL was determined at various temperatures by the gravimetrical method. Alterations in the microscopic structure of the lens were analyzed in situ with a reflecting microscope without staining, while the temperature of the lens was changed at different rates.

RESULTS

Microvacuoles of 1.0 to 20.0 microm formed in the bulk of a swollen AcrySof IOL as the temperature decreased. The morphology of the vacuoles was similar to that of glistening particles observed in vivo. The size and density of the glistening-like vacuoles varied depending on the magnitude and rate of the temperature decrease. The glistening-like vacuoles were imprinted in the bulk of the IOL during the preceding cooling process in aqueous humor.

CONCLUSIONS

Glistenings formed in the bulk of an AcrySof IOL as the medium temperature decreased. The mechanism may involve spinodal decomposition of the swollen polymer network, which initiates the formation of microvacuoles consisting of water and loosely packed network chains.

Influence of glistenings on the optical quality of acrylic foldable intraocular lens

AIMS

To assess the influence of glistenings on the optical quality of acrylic foldable intraocular lens.

METHODS

Several degrees of glistenings in the optic were experimentally created by immersing the lens in water at 37 degrees C for 48 hours and then at 25 degrees C for 24 hours. Optical bench tests were carried out in water including measurements of spectral transmittance with the spectrophotometer, intensity of forward scattering using the integrating sphere photometer, modulation transfer function, and resolving power at various contrasts with and without the veiling glare light source.

RESULTS

Glistenings of 1+ to 4+ degrees were created, among which the 4+ glistenings seemed to be extremely intense and thought to be beyond the range of clinical settings. Clinically feasible level of glistenings, up to 3+, did not adversely influence spectral transmittance, scattering, modulation transfer function, and resolving power at various contrasts. The 4+ glistenings caused mild to moderate deteriorations of the optical quality of the lens.

CONCLUSION

The optical quality of the acrylic foldable intraocular lens is not significantly affected by the level of glistenings usually seen in the clinical setting.

Dense opacification of the optical component of a hydrophilic acrylic intraocular lens: a clinicopathological analysis of 9 explanted lenses

PURPOSE

To report clinical, pathological, histochemical, ultrastructural, and spectrographic analyses of explanted hydrophilic acrylic intraocular lenses (IOLs) obtained from patients who had visual disturbances caused by postoperative opacification of the lens optic.

SETTING

Center for Research on Ocular Therapeutics and Biodevices, Storm Eye Institute, Medical University of South Carolina, Charleston, South Carolina, USA, and Ege University, Alsancak Izmir, Turkey.

METHODS

Nine hydrophilic IOLs (SC60B-OUV, MDR Inc.) were explanted from 9 patients with decreased visual acuity. Most patients became symptomatic approximately 24 months after uneventful phacoemulsification and IOL implantation. Opacification was noted and appeared clinically to be associated with a fine granularity within the substance of the IOL optic. The IOLs were forwarded to the center and examined by gross and light microscopy. Full-thickness cut sections of the optics were stained with 1% alizarin red and the von Kossa method (special stains for calcium). Some were submitted for scanning electron microscopy and energy dispersive x-ray spectroscopy.

RESULTS

Microscopic analyses revealed multiple fine, granular deposits of variable sizes within the lens optics, usually distributed in a line parallel to the anterior and posterior curvatures of the optic, with a clear zone just beneath the optic surface. The deposits stained positive with alizarin red and the von Kossa method. Energy dispersive x-ray spectroscopy of the internal substance of sectioned IOLs demonstrated the presence of calcium within the deposits.

CONCLUSION

This is the first clinicopathological report of optic opacification occurring with this hydrophilic acrylic IOL model. Studies of similar cases with this lens should be done to determine the incidence and possible mechanisms of the phenomenon.

Posterior capsule opacification and lens epithelial cell layer formation: Hydroview hydrogel versus AcrySof acrylic intraocular lenses

PURPOSE

To quantitatively compare the incidence of visually significant posterior capsule opacification (PCO) and lens epithelial cell (LEC) layer formation on the anterior surface of Hydroview hydrogel and AcrySof acrylic foldable intraocular lenses (IOLs) after implantation.

SETTING

Single-surgeon ophthalmology practice, Orange Base Hospital, and Dudley Private Hospital, Orange, New South Wales, Australia.

METHODS

This retrospective study comprised 166 eyes of 150 patients (after exclusions) who had cataract extraction and insertion of a foldable IOL in the capsular bag by a single surgeon using a standardized phacoemulsification technique from December 1997 to September 1998. The mean follow-up was 13.1 months (range 6.0 to 23.6 months). The eyes were divided into 2 groups based on the type of IOL implanted: Storz Hydroview H60M (81 eyes) or Alcon AcrySof MA30BA (85 eyes). A neodymium:YAG posterior capsule laser capsulotomy (PC YAG) was performed for an objective decrease in Snellen best corrected visual acuity (BCVA) of more than 1 line, significant visual symptoms, or both. This was used as a measure of visually significant PCO. An Nd:YAG anterior surface clearance (ASC YAG) was done for LEC layer formation anterior to the IOL to better visualize or facilitate treatment of PCO. The rates of PC YAG and ASC YAG after Hydroview and AcrySof IOL implantation were statistically compared.

RESULTS

Forty-five eyes (55.6%) in the Hydroview IOL group and 3 eyes (3.5%) in the AcrySof IOL group required a PC YAG; the risk difference was 52.0% (P <.001). An ASC YAG was required in 27 eyes (33.3%) in the Hydroview group and 1 eye (1.2%) in the AcrySof group; the risk difference was 32.2% (P <.001). Survival analysis demonstrated that the only independent predictor of the incidence of PC YAG and ASC YAG over time was IOL type, with the Hydroview IOL group having a statistically significantly higher incidence of both procedures.

CONCLUSION

There was a greater incidence of visually significant PCO and LEC layer formation on the anterior surface of Hydroview IOLs than of AcrySof IOLs.

Noninvasive Raman spectroscopic identification of intraocular lens material in the living human eye

PURPOSE

To develop a safe noninvasive technique for identifying the material of intraocular lenses (IOLs) implanted in patients.

SETTING

Center for Biomedical Engineering and the Department of Ophthalmology and Visual Sciences, University of Texas Medical Branch, Galveston, Texas, USA.

METHODS

Raman spectroscopy was used to noninvasively identify the type of IOL implanted after previous cataract surgery in 9 eyes of 6 patients who were legally blind as a result of eye disease. Three IOLs were characterized: poly(methyl methacrylate) (PMMA) (n = 5), acrylic (n = 3), and silicone (n = 1). Confocal Raman spectroscopy was used with a laser power of 95 microW and exposure time of 1 second.

RESULTS

Distinct spectral peaks associated with each type of IOL were obtained. These included spectra peaks at 2840 cm(-1), 2946 cm(-1), and 3000 cm(-1) for PMMA; 2917 cm(-1), 2939 cm(-1), and 3055 cm(-1) for acrylic; and 2900 cm(-1), 2961 cm(-1), and 3048 cm(-1) for silicone. The procedure was well accepted by patients, and there were no complications.

CONCLUSIONS

The specific Raman spectra of the IOLs allowed for noninvasive determination of IOL material with the use of a safe light dose and an exposure time of 1 second.

Silicone oil-intraocular lens interaction: which lens to use?

AIM

To determine a suitable intraocular lens for implantation in patients at high risk of lens exposure to silicone oil in their lifetime.

METHODS

PMMA, AcrySof, AR40, AQUA-Sense, and Raysoft lenses were examined. Each lens was immersed for 5 minute intervals in balanced salt solution (BSS), in stained silicone oil, and again in BSS before being photographed in air and in BSS. Percentage silicone oil coverage of the lens optic was determined.

RESULTS

The mean percentage coating (MPC) for the lens biomaterials ranged from 5.2% to 21.5%. The Raysoft lens had significantly less oil coverage when statistically compared with the other lens types (p < 0.001).

CONCLUSION

A Raysoft (Rayner) lens is a suitable lens for implantation in patients who are at risk of severe vitreoretinal disease.

Postoperative deposition of calcium on the surfaces of a hydrogel intraocular lens

OBJECTIVE

To report clinical, pathological and histochemical features of 5 Hydroview intraocular lenses (IOLs) explanted from five patients who had visual disturbances caused by postoperative deposits on the lens surfaces.

DESIGN

Noncomparative small case series with clinicopathologic and histochemical correlations.

PARTICIPANTS

Five hydrophilic IOLs explanted from five different patients. All patients presented with decreased visual acuity and glare circa 12 months after uneventful phacoemulsification and IOL implantation, associated with a red-brown granularity on the optical surfaces of the IOLs.

METHODS

The lenses were explanted, fixed in buffered formaldehyde and examined by gross and light microscopy.

MAIN OUTCOME MEASURES

Staining of the IOLs with 1% alizarin red and with the von Kossa method (both stains for calcium). Two additional IOLs were also stained and included as controls.

RESULTS

The optical surfaces of all five IOLs were covered by a layer of irregular granular deposits, composed of multiple fine, translucent spherical-ovoid granules. The deposits stained positive for calcium in all cases. No deposit or positive staining was observed on the IOLs haptics. Staining of the control IOLs was also negative.

CONCLUSION

This is the first histopathological report of calcified deposits on the surfaces of this hydrogel IOL model. Further studies on other similar cases with this lens should be done to determine the incidence and possible mechanisms of this phenomenon.