Identification of intraocular lens-adsorbed proteins in mammalian in vitro and in vivo systems

Role of fibronectin and IOL surface modification in IOL: Lens capsule interactions

Posterior Capsule Opacification (PCO) is one of the most common complications of cataract surgery. While studies have shown that IOL material properties and fibronectin adsorption may affect IOL-induced PCO in the clinical setting, the mechanism governing such interactions is not totally understood. Since strong adhesion forces between IOLs and posterior capsules (PCs) have been shown to impede cell infiltration and thus reduce PCO formation, this study was designed to assess whether fibronectin adsorption and IOL material properties would impact the IOL:PC adhesion force and cell infiltration using a PCO predictive in vitro model and a macromolecular dye imaging model, respectively. Our results showed that fibronectin adsorption significantly increased the adhesion forces and reduced simulated cell infiltration between acrylic foldable IOLs and the PC at physiological temperature in comparison to fibronectin-free controls. This fibronectin-mediated strong IOL: PC bond may be contributing to low PCO rates in the clinic for acrylic foldable IOLs. In addition, acrylic foldable IOLs coated with Di(ethylene glycol) (Diglyme), a hydrophilic coating known to reduce protein adsorption, was tested for its ability to alter adhesion force and cell infiltration. We observed that IOLs coated with Diglyme coating greatly reduced surface hydrophobicity and fibronectin adsorption of acrylic foldable IOLs. Furthermore, Diglyme coated IOLs showed significantly reduced adhesion force and increased simulated cell infiltration at the IOL:PC interface. The overall results support the hypothesis that IOL surface properties and their ability to adsorb fibronectin may have great impact on the IOL:PC adhesion force. A tight binding between IOLs and PC may contribute to the reduction of cell infiltration and thus the PCO incidence rate in the clinic.

Fouling in ocular devices: implications for drug delivery, bioactive surface immobilization, and biomaterial design

The last 30 years has seen a proliferation of research on protein-resistant biomaterials targeted at designing bio-inert surfaces, which are prerequisite for optimal performance of implantable devices that contact biological fluids and tissues. These efforts have only been able to yield minimal results, and hence, the ideal anti-fouling biomaterial has remained elusive. Some studies have yielded biomaterials with a reduced fouling index among which high molecular weight polyethylene glycols have remained dominant. Interestingly, the field of implantable ocular devices has not experienced an outflow of research in this area, possibly due to the assumption that biomaterials tested in other body fluids can be translated for application in the ocular space. Unfortunately, progression in the molecular understanding of many ocular conditions has brought to the fore the need for treatment options that necessitates the use of anti-fouling biomaterials. From the earliest implanted horsehair and silk seton for glaucoma drainage to the recent mini telescopes for sight recovery, this review provides a concise incursion into the gradual evolution of biomaterials for the design of implantable ocular devices as well as approaches used to overcome the challenges with fouling. The implication of fouling for drug delivery, the design of immune-responsive biomaterials, as well as advanced surface immobilization approaches to support the overall performance of implantable ocular devices are also reviewed.

Scanning Electron Microscopy and Energy Dispersive Spectroscopy Findings in Explanted Pmma and Hydrophilic Acrylic Intraocular Lenses

Purpose

To investigate the presence of calcium (Ca) aggregates influencing biocompatibility and the factors that affect calcium accumulation in explanted intraocular lenses (IOL) and to analyze the Ca distribution in an opacified hydrophilic acrylic lens.

Methods

Surface irregularities and aggregates of 13 IOLs were studied with scanning electron microscopy, and their relative concentrations with energy dispersive spectroscopy (EDS). Relationships of distribution between Ca and silicone (Si) and nitrogen (N) and between N and Si and Na, and the influence of Si on Ca accumulation and the effect of differences in lens material on the distribution of N, and the effect of endophthalmitis on the distribution of Ca were evaluated statistically. EDS analyses were performed on the surface and cross-section of the opacified lens.

Results

The statistically significant relationships between the distribution of Ca and N, and between the distribution of N and Na, the significant effect of Si on the Ca accumulation, significant relationship between endophthalmitis and the Ca accumulation in the aggregates were shown. The EDS analysis of the opacified IOL, Ca and P peaks were shown from the whole surface, Ca, O peaks were determined from cross-sections over a 70–80 μm distance.

Conclusions

In the aggregates influencing IOL biocompatibility, presence of proteins was determined to be more important than the presence of Si regarding the distribution of Ca, while the presence of Si affected the accumulation of Ca. Opacification, caused by the Ca accumulation within the lens, was found to result from Ca penetrating from lens pores.

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.

Optical coherence tomography of intraocular lens implants and their relationship to the posterior capsule: a pilot study comparing a hydrophobic acrylic to a plate-haptic silicone type

BACKGROUND

Optical coherence tomography (OCT) has been used to examine the anterior as well as the posterior segment and can be used to examine the intraocular lens (IOL) and their relationship to the posterior capsule in vivo.

OBJECTIVES

To use OCT to examine two of the IOLs and some of the features related to the development of posterior capsular opacification (PCO).

METHODS

This is a pilot study of a prospective (n = 12) and a retrospective (n = 14) series of patients who had uneventful phacoemulsification and IOL implantation of either hydrophobic acrylic (Acrysof; Alcon) or plate-haptic (PH) silicone (C11UB; Chiron, Bausch & Lomb) IOLs. The outcome of interest was the ability of OCT to clearly delineate the outline of the IOL optics and their appositional relationship to the posterior capsule.

RESULTS

OCT showed that hydrophobic acrylic IOLs had a better defined outline than PH silicone IOLs. It also showed close apposition between hydrophobic acrylic optics and the mid-peripheral part of the posterior capsule and the absence thereof with PH silicone IOLs.

CONCLUSIONS

Hydrophobic acrylic implants have better definition on the OCT scans than PH silicone and they develop close apposition to the posterior capsule. The latter feature is consistent with the 'no space, no cell, no PCO' concept and what is known about the effect of the implant material and design on the rate of PCO.

Adhesion of soluble fibronectin, vitronectin, and collagen type IV to intraocular lens materials

PURPOSE

To evaluate soluble fibronectin, vitronectin, and collagen type IV adhesion to poly(methyl methacrylate) (PMMA), fluorine-surface-modified PMMA, silicone, hydrophobic and hydrophilic acrylate, and hydrogel intraocular lenses (IOLs) and determine whether hydrophobic and hydrophilic acrylate materials have different fibronectin-adhesion properties.

SETTING

Department of Medical Biochemistry, University of Oulu, Oulu, Finland.

METHODS

One hundred fifty IOLs were incubated for 1 week at 37 degrees C with radioactive-iodine-labeled soluble fibronectin, vitronectin, or collagen type IV. Fifty IOLs were analyzed for each protein, 5 from each of 10 different IOL models (PMMA, Alcon MC60BM; fluorine-surface-modified PMMA, Chiron Fluorilens Centra-55F; silicone, Allergan Medical Optics SI-40NB and Pharmacia and Upjohn CeeOn 911A; hydrophobic soft acrylate, Alcon AcrySof MA60BM and SA30AL and AMO Sensar; hydrophilic soft acrylate, Ioltech Stabibag and Bausch and Lomb BL27; and hydrogel, Bausch and Lomb Hydroview. The amount of adherent protein was measured with a gamma counter at 1 and 7 days and expressed as counts per minute.

RESULTS

At 1 week, significantly more fibronectin was bound to the hydrophobic acrylate IOLs than to the 2-hydroxyethyl methacrylate (HEMA) containing hydrophilic acrylate IOLs (P <.05 to.0001). Significantly more vitronectin was bound to the 2 silicone IOLs than to any other IOL (P <.01 to.0001) at 7 days. Collagen type IV adhered best to the hydrophilic acrylate IOLs, which were significantly different (P <.01 to.0001) than the other IOLs at 1 and 7 days.

CONCLUSIONS

Each IOL material had a different affinity to each protein. Significant binding to 1 protein does not indicate that the IOL will bind significantly to all proteins; instead, each protein should be studied separately. Fibronectin bound significantly better to hydrophobic acrylate IOLs than to hydrophilic acrylate IOLs, suggesting that the HEMA-containing IOLs should be classified with the hydrogel IOL group.

Adhesion of fibronectin, vitronectin, laminin, and collagen type IV to intraocular lens materials in pseudophakic human autopsy eyes. Part 2: explanted intraocular lenses

PURPOSE

To evaluate fibronectin, vitronectin, laminin, and collagen type IV adhesion to poly(methyl methacrylate) (PMMA), silicone, hydrophobic soft acrylate, and hydrogel intraocular lenses (IOLs) in human pseudophakic autopsy eyes.

SETTING

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

METHODS

Thirty-two autopsy eyes containing PMMA, silicone, soft acrylate, or hydrogel IOLs were assessed. The IOLs were explanted from the capsular bag, and both sides of the IOLs were immunohistochemically stained for fibronectin, vitronectin, laminin, or collagen type IV. The number of cells on the IOL surfaces was counted. The capsular bag from 1 eye containing a soft acrylate IOL was examined for fibronectin and vitronectin.

RESULTS

Hydrophobic soft acrylate IOLs had significantly more fibronectin adhering to their surfaces than PMMA (P <.01) or silicone (P <.01) IOLs, as well as more vitronectin. Silicone IOLs had more collagen type IV adhesion than the other IOLs (P <.05-.06). Collective protein adhesion differed significantly between soft acrylate IOLs and PMMA and silicone IOLs, but not between PMMA and silicone IOLs.

CONCLUSIONS

The greater amount of protein on the hydrophobic soft acrylate (AcrySof(R)) IOLs seems to support an adhesive mechanism for their attachment to the capsular bag. Fibronectin and vitronectin have functional domains to bind them to lens epithelial cells and the collagenous capsule. This kind of attachment could be a true bioactive bond and may be 1 reason the PCO and neodymium:YAG capsulotomy rates are lower in eyes with a soft acrylate IOL.

Posterior capsular opacification with hydrogel, polymethylmethacrylate, and silicone intraocular lenses: two-year results of a randomized prospective trial

PURPOSE

To compare the visual outcome, percentage of posterior capsular opacification, and laser capsulotomy rates with polymethylmethacrylate, silicone, and hydrogel intraocular lens implants at 1 and 2 years postoperatively.

METHODS

Ninety-three eyes of 93 patients were randomized to receive a polymethylmethacrylate, silicone, or hydrogel intraocular lens implant. A standardized surgical protocol was followed by a single surgeon using phacoemulsification with capsulorhexis; any patients with surgical complications were excluded, and all patients received standardized medication and follow-up. Patients were examined at days 1 and 7, months 1, 3, and 6, and years 1 and 2 after surgery. At each assessment, best-corrected logMAR visual acuity and Pelli-Robson contrast sensitivity were measured. Posterior capsular opacification was objectively assessed by digital retroillumination imaging with the use of a dedicated software program and calculated as the percentage area of opacified capsule. Laser capsulotomy was performed if the eye had lost 2 lines of visual acuity with a clinically opaque capsule.

RESULTS

At 2 years postoperatively, the mean percentage area of posterior capsular opacification for hydrogel lenses was 63%; for polymethylmethacrylate, 46%; and for silicone, 17%. Hydrogel intraocular lenses were associated with 17% more posterior capsule opacification than were polymethylmethacrylate lenses (95% confidence interval, 1-33; P =. 037) and 45% more than were silicone lenses (95% confidence interval, 33-58; P <.0001) at 2 years. Polymethylmethacrylate lenses had 28% more posterior capsule opacification than silicone lenses (95% confidence interval, 13-43; P <.0001) at 2 years. Twenty-eight percent of patients with hydrogel intraocular lenses required an Nd:YAG laser posterior capsulotomy at 2 years, compared with 14% with polymethylmethacrylate, whereas no patients with silicone lenses needed a capsulotomy (P =.014). Visual acuity was not significantly different among the three groups, but patients with silicone intraocular lenses had significantly better contrast sensitivity than those with hydrogel lenses (P =.046).

CONCLUSIONS

Intraocular lenses made of this specific hydrogel were associated with a significantly higher degree of posterior capsular opacification and more laser capsulotomies than polymethylmethacrylate and silicone intraocular lenses.

Evaluation of foldable intraocular lenses in patients with uveitis

OBJECTIVE

To evaluate various foldable posterior chamber intraocular lenses (IOLs) after phacoemulsification in patients with uveitis.

DESIGN

A prospective, noncomparative, interventional case series.

PARTICIPANTS

Forty-nine consecutive patients (60 eyes) with various types of uveitis (anterior, n = 20; posterior, n = 1; panuveitis, n = 37, intermediate, n = 2).

INTERVENTION

All patients underwent phacoemulsification with foldable posterior chamber IOL implantation. All eyes were free of active inflammation at the time of surgery. A variety of IOL biomaterials were implanted: acrylic (n = 30), silicone (n = 17), and hydrogel (n = 13).

MAIN OUTCOME MEASURES

Detailed examination was performed by one masked observer. Several parameters were compared for each implant biomaterial, including level of best corrected Snellen visual acuity at final follow-up, presence of posterior synechiae, anterior capsular phimosis, posterior capsule opacification, and the degree of cellular deposits on the IOL optic.

RESULTS

There were 26 males and 23 females, aged 9 to 83 years (mean, 48 years). Follow-up ranged from 1 to 33 months (mean, 17.03 months). At final follow-up, 56 eyes (93.3%) had an improvement in visual acuity compared with preoperative levels as follows: 34 eyes (56.6%) achieved an improvement of four or more Snellen lines, and 44 eyes (73.3%) achieved 20/30 or better. Giant cells, observed on the IOL optic in 19 eyes (31.7%), were most often seen on the acrylic biomaterial at the 1-month follow-up, although this was not found to be statistically significant. Scratch marks produced by the lens-introducing forceps were seen in 24 eyes (40.0%), mainly on the acrylic and hydrogel optics. Posterior capsule opacification (PCO) occurred in 49 eyes (81.7%), with only 5 eyes requiring laser capsulotomy. There was no association between PCO and the various lens biomaterials. Other causes for reduced visual acuity included glaucomatous optic neuropathy (n = 5) and cystoid macular edema (n = 8).

CONCLUSIONS

The use of foldable IOLs in eyes with uveitis is safe, but the optimal biomaterial has yet to be found.

Adhesion of soluble fibronectin, laminin, and collagen type IV to intraocular lens materials

PURPOSE

To evaluate soluble fibronectin, laminin, and collagen IV adhesion to poly(methyl methacrylate) (PMMA), heparin-surface-modified (HSM) PMMA, silicone, acrylate, and hydrogel intraocular lenses (IOLs).

SETTING

Department of Medical Biochemistry, University of Oulu, Oulu, Finland.

METHODS

Seventy-five IOLs were incubated for 24 hours at 37 degrees C with radioactive iodine labeled soluble fibronectin, laminin, or collagen type IV. Twenty-five IOLs were analyzed for each protein, 5 of each type. The amount of absorbed protein was measured with a gamma counter and expressed as counts per minute (cpm).

RESULTS

Fibronectin bound best to the acrylate IOL; the differences between the acrylate and the other materials, except PMMA, were significant (P < .01 to .001; PMMA P = .31). Although significantly more laminin bound to acrylate than to PMMA, HSM PMMA, or silicone (P < .05 to .001), hydrogel had the highest overall binding of this protein (P < .001 to .0001). Hydrogel also had significantly higher binding of type IV collagen than the other IOLs (P < .01 to .0001).

CONCLUSIONS

It can be hypothesized that if an IOL has more fibronectin bound to it, the IOL can also attach to the capsule better as it consists mainly of collagen. The stronger binding of fibronectin and laminin to acrylate IOLs could be an explanation for the better adhesion of the acrylate IOL to the anterior and posterior capsules and thus for the lower rate of posterior capsule opacification.

Evaluation of teflon-coated intraocular lenses in an organ culture method

An amorphous and transparent form of Teflon is proposed as a coating of polymethylmethacrylate (PMMA) intraocular lenses (IOLs), rendering them highly hydrophobic. We used an organ culture method to evaluate cell adhesion, proliferation, and migration on Teflon-coated IOLs. Corneal explants from 14-day-old chicken embryos were placed on a semisolid culture medium and covered with uncoated PMMA (n = 36) and Teflon-coated PMMA (n = 36) IOLs and two controls, Thermanox (n = 84) and latex (n = 36). After incubation (7 days at 37 degrees C), a digital imaging system was used to measure the areas of the cell migration layers on the materials. The cells were then removed with tripsin-ethylenediaminetetraacetic acid and the cells detached at times up to 75 min were counted (Coulter(R) Multisizer System). The values were used to construct a cell disconnecting curve for each material. The areas of cell migration layers on uncoated and Teflon-coated IOLs were significantly different (p <.05). Cell disconnecting curves demonstrated that cells adhered less strongly to Teflon-coated IOLs than to the other materials. This organ culture method demonstrated that the coating of PMMA IOLs with Teflon AF(R) is correlated with antiadhesive and antiproliferative properties.

In vitro protein adsorption to 2 intraocular lens materials

PURPOSE

To study in vitro protein adsorption to poly(methyl methacrylate) (PMMA) and foldable AcrySof intraocular lenses (IOLs).

SETTING

Department of Ophthalmology, United Medical and Dental Schools of Guy's and St. Thomas' Hospitals, London, United Kingdom.

METHODS

Poly(methyl methacrylate) (Alcon Surgical, model MC60BM) and AcrySof (Alcon Surgical, model MA60BM) IOLs were incubated in physiological concentrations of radiolabeled albumin or fibronectin at 37 degrees C for periods between 5 minutes and 1 week. The IOLs were removed and rinsed in buffered saline, and the amount of adsorbed protein was calculated by measuring the radioactivity with scintillation spectrometry.

RESULTS

The adsorption of both proteins occurred rapidly over the first 2 hours; the rate of adsorption was concentration dependent. Quantitative differences were found: PMMA lenses bound significantly greater quantities of albumin. Initial fibronectin adsorption to both materials was similar, but increased adsorption to AcrySof IOLs was found at days 1 and 7.

CONCLUSIONS

The differences in protein absorption to PMMA and AcrySof IOLs in vitro may contribute to the differences in the biological response to these IOLs, including the lower rates of posterior capsule opacification associated with acrylic lenses.

Protein adsorption onto ceramic surfaces

Ceramics seldom have been used as blood-contacting materials. However, alumina ceramic (Al2O3) and polyethylene are incorporated into the pivot bearings of the Gyro centrifugal blood pump. This material combination was chosen based on the high durability of the materials. Due to the stagnant flow that often occurs in a continuous flow condition inside a centrifugal pump, pivot bearing system is extremely critical. To evaluate the thombogenicity of pivot bearings in the Gyro pump, this study sought to investigate protein adsorption, particularly albumin, IgG, fibrinogen, and fibronectin onto ceramic surfaces. Al2O3 and silicon carbide ceramic (SiC) were compared with polyethylene (PE) and polyvinylchloride (PVC). Bicinchoninic acid (BCA) protein assay revealed that the amount of adsorbed proteins onto Al2O3 and SiC was significantly less than that on PVC. The sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) indicated that numerous proteins adsorbed onto PVC compared to PE, Al2O3, and SiC. Identification of adsorbed proteins by Western immunoblotting revealed that the adsorption of albumin was similar on all four materials tested. Western immunoblotting also indicated lesser amounts of IgG, fibrinogen, and fibronectin on Al2O3 and SiC than on PE and PVC. In conclusion, ceramics (Al2O3 and SiC) are expected to be thromboresistant from the viewpoint of protein adsorption.

Relationship between intraocular lens biomaterials and posterior capsule opacification

PURPOSE

To determine whether posterior capsule opacification (PCO) is influenced by intraocular lens (IOL) material.

SETTING

A British teaching hospital eye department.

METHODS

Ninety eyes were prospectively randomized to receive a poly(methyl methacrylate) (PMMA), silicone, or AcrySof IOL. All lenses had 6.0 mm optics and PMMA haptics. A standardized surgical protocol was performed by a single surgeon using an extracapsular technique with capsulorhexis. Patients having surgical complications were excluded and all patients had standardized medication and follow-up. Posterior capsule opacification was assessed by a digital retroillumination camera using a dedicated software program based on the analysis of texture in the image and calculated as the percentage area of opacified capsule. Data were analyzed 2 years postoperatively.

RESULTS

There was a significant difference in percentage of PCO at 2 years among the three lens types (P < .0001). The AcrySof lenses were associated with less PCO (median 11.75%) than PMMA (43.65%) and silicone (33.50%) lenses (P < .001 and P = .025, respectively). The difference between PMMA and silicone lenses was not statistically significant.

CONCLUSION

Intraocular lenses made from AcrySof were associated with a significantly reduced degree of PCO.

Deposition of extracellular matrix on silicone intraocular lens implants in rabbits

PURPOSE

To examine the deposition of extracellular matrix on silicone intraocular lenses (IOLs) implanted experimentally into rabbit eyes by electron microscopy and to determine the immunolocalization of extracellular matrix components, including collagen types and cellular fibronectin, on these IOLs.

METHODS

We performed phacoemulsification and aspiration of the crystalline lens and implanted a foldable silicone IOL in the capsular bag of one eye of each of 26 adult albino rabbits under general anesthesia. After 8 weeks the animals were killed and the eyes were enucleated. The silicone IOLs were processed for electron microscopy and for immunohistochemical detection of collagen types I, III, and IV and cellular fibronectin.

RESULTS

Electron microscopy revealed deposition of a presumed cell matrix complex on the optic portion of all silicone IOLs, as well as the adhesion of presumed macrophages and foreign-body giant cells. Cellular deposits showed immunoreactivity for cellular fibronectin. Fibrous or membranous deposits exhibited immunoreactivity for cellular fibronectin and collagen types I and III. A few type IV collagen-immunoreactive deposits were also seen.

CONCLUSION

Deposits of extracellular matrix components were observed on silicone IOLs. These deposits may form the scaffolding for the adhesion and proliferation of cells. These matrix components appeared to be the products of cells adhering to the surfaces of IOLs, including lens epithelial cells, macrophages and foreign-body giant cells, indicating that the process of granulation was incomplete.

Deposition of extracellular matrix on intraocular lenses in rabbits: an immunohistochemical and transmission electron microscopic study

BACKGROUND

We examined by transmission electron microscopy the accumulation of extracellular matrix on intraocular lenses (IOLs) implanted experimentally into rabbit eyes, and evaluated the immunolocalization of such extracellular matrix components as collagen types I, III, and IV, and cellular fibronectin on these IOLs.

METHODS

Phacoemulsification and aspiration of the crystalline lens were performed and an IOL was implanted into the capsular bag of each eye of each of 16 adult albino rabbits under general anesthesia. After up to 12 weeks, the animals were killed and the IOLs were removed. Specimens were processed for transmission electron microscopy or for immunohistochemical detection collagen types I, III, and IV, and cellular fibronectin.

RESULTS

Transmission electron microscopy revealed an accumulation of extracellular matrix between the residual anterior lens capsule and the surface of an IOL explanted 4 weeks after surgery. Collagen types I and III and cellular fibronectin were detected immunohistochemically on each IOL in association with cellular deposits. Type IV collagen-immunoreactive matrix was not seen on the optic portion, but was detected on the haptic portion of one of six IOLs examined.

CONCLUSION

Each component of the extracellular matrix that is deposited on the IOL supplies scaffolding for the adhesion and proliferation of cells. These components are considered to be produced by cells such as lens epithelial cells and macrophages that adhere to the IOL surface.

Lens epithelial cell outgrowth and matrix formation on intraocular lenses in rabbit eyes

PURPOSE

To evaluate the presence and distribution of lens epithelial cells (LECs) and extracellular matrix on intraocular lenses (IOLs) implanted in the capsular bag in rabbit eyes.

SETTING

Department of Ophthalmology, Wakayama Medical College, Wakayama, Japan.

METHODS

Five adult albino rabbits had phacoemulsification and IOL implantation in both eyes. Two or 11 months later, the animals were killed by intravenous pentobarbital. The IOLs were removed and observed under scanning and transmission electron microscopy.

RESULTS

In addition to the macrophages and giant cells on the IOLs, all eyes had a monolayer of flattened cells growing out from the residual anterior lens capsule and a fibrous meshwork of extracellular matrix. Unlike those of a macrophagic origin, these cells had no central cytoplasmic elevation of nuclei and few cell surface microvilli and were considered to be proliferating LECs.

CONCLUSION

Lens epithelial cells are involved in the eye's cellular reaction to IOLs and in the formation of extracellular matrix on IOLs. Further study of LEC behavior on IOLs should be done to improve IOL biocompatibility.

Extracellular matrix on intraocular lenses

We examined the distribution of extracellular matrix components in the proteinaceous matrix on explanted IOLs using immunohistochemistry to clarify the nature of proteinaceous deposits on the surfaces of IOLs. We examined 15 polymethylmethacrylate (PMMA) IOLs and one silicone IOL explanted from patients. The IOLs were immunostained for cellular fibronectin, types I and IV collagen, and vitronectin. Various amounts of fibronectin, types I and IV collagen, and vitronectin were detected in the extracellular matrix on all IOLs with cellular deposits. Types I and IV collagen and cellular fibronectin were present in the extracellular matrix and were probably the products of cells adhering to the IOLs. Vitronectin in the fibrous extracellular matrix appeared to represent an adsorption material derived from the aqueous humor. These proteinaceous deposits associated with cellular deposits indicate unsuccessful formation of granulation tissue and could influence IOL biocompatibility.