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PubMed2000

Foldable silicone versus poly(methyl methacrylate) intraocular lenses in combined phacoemulsification and trabeculectomy.

PURPOSE: To compare the outcome of phacotrabeculectomy with implantation of poly(methyl methacrylate) (PMMA) or foldable silicone intraocular lenses (IOLs). METHODS: Thirty patients were randomized to receive a 5.5 mm PMMA IOL through a 5.0 mm incision or a foldable silicone IOL (Allergan SI-30) through a 3.2 mm incision. Visual acuity, intraocular pressure (IOP), bleb survival, inflammation, endothelial cell changes, and complications were examined at intervals up to 6 months. RESULTS: There was no difference between the 2 groups in final visual outcome, final IOP control, bleb survival, and endothelial cell changes. Two months after surgery, there was significantly more inflammation in the silicone IOL group than in the PMMA group (P <. 05). The silicone group had a significantly higher combined complication rate including iris capture, choroidal effusion, and epiretinal membrane formation (P <.05). CONCLUSIONS: Foldable silicone IOLs were comparable to conventional PMMA lenses in visual outcome, IOP control, bleb formation, and endothelial changes. However, some silicone lenses are associated with an increased risk of recurrence of inflammation and a higher final complication rate in combined cataract and filtration surgery.

Aged↗
PubMed2002

Relationship of AcrySof acrylic and PhacoFlex silicone intraocular lenses to visual acuity and posterior capsule opacification.

PURPOSE: To compare the changes in visual acuity and the development of posterior capsule opacification (PCO) with AcrySof acrylic intraocular lenses (IOLs) (Alcon Laboratories) and second-generation PhacoFlex silicone IOLs (Allergan ). SETTING: Eye Associates of New Mexico and Southwest Colorado, Albuquerque, New Mexico, USA. METHODS: Medical charts of patients having cataract extraction with implantation of an AcrySof MA30BA or MA60BM (MA30/60) or PhacoFlex SI-30NB or SI-40NB (SI-30/40) IOL between January 1995 and June 1997 were abstracted. Analyzed were the changes in visual acuity and development of PCO 1 month postoperatively and at the last available ophthalmologist visit or the visit before neodymium:YAG (Nd:YAG) capsulotomy. RESULTS: Patients with MA30/60 acrylic IOLs were significantly older, had a worse preoperative best corrected visual acuity (BCVA), and had more concomitant ocular diseases than those with SI-30/40 silicone IOLs. The change in BCVA from preoperatively to 1 month postoperatively was equivalent in the 2 lens groups. The BCVA declined from 1 month postoperatively to the last recorded or pre-Nd:YAG visit. This decline was greater in eyes with SI-30/40 silicone IOLs than in those with MA30/60 acrylic IOLs. Although the decrease in BCVA between IOL types was not significantly different, eyes with a SI-30/40 silicone IOL were significantly more likely to develop PCO and have Nd:YAG capsulotomy. Eyes developing PCO had a statistically significant decline in BCVA from 1 month postoperatively to the last/pre-Nd:YAG visit. CONCLUSIONS: The MA30/60 acrylic lenses were associated with lower PCO and Nd:YAG capsulotomy rates than second-generation SI-30/40 silicone IOLs. Patients with MA30/60 IOLs also tended to have less of a decrease in visual acuity than patients with SI-30/40 silicone lenses, probably as a result of the difference in PCO rates between groups.

Acrylic Resins↗
PubMed1988

Clinical endothelial cell loss following phacoemulsification and silicone or polymethylmethacrylate lens implantation.

This study is a comparison of endothelial cell loss seen by two surgeons using the same surgical technique (posterior chamber phacoemulsification) with posterior chamber implants of two different materials (silicone and polymethylmethacrylate [PMMA]). One hundred four silicone lenses were implanted following phacoemulsification and compared with 160 PMMA lenses implanted during the same period. A significant feature of these procedures was the incidence of endothelial cell loss of greater than 1,200 cells/mm2. This occurred in 12.0% of cases with PMMA implants and in 15.4% of cases with silicone implants. When silicone implants were analyzed by insertion technique, flat insertion had only 7.7% cell loss of over 1,200 cells/mm2 whereas folding-bar insertion (14.3%) and syringe-style insertion (16.9%) showed a significant increase in the incidence of cell loss. Pachymetric results coincided with endothelial cell counts. Although silicone implants inserted flat produced less endothelial cell loss than PMMA implants inserted flat, silicone implants inserted folded produced greater loss. Improved insertion techniques should be developed.

Adult↗
PubMedDate not supplied

Predicted and actual refraction after intraocular lens implantation in eyes with silicone oil.

OBJECTIVE: To determine the difference between the predicted and postoperative refraction in eyes with silicone oil that had extracapsular cataract extraction (ECCE), and intraocular lens (IOL) implantation. SETTING: Ophthalmology department providing primary, secondary, and tertiary care in central Israel. METHODS: Eight patients with silicone-oil-filled eyes following vitreoretinal procedures had ECCE and IOL implantation. The IOL power calculation was performed with the modified SRK II, the SRK/T, and the Holladay emmetropia/ametropia formulas, using the axial length of the eye, measured prior to the silicone oil injection, and the keratometric readings. The predicted and postoperative refractions were compared. RESULTS: The postoperative refraction was more hyperopic than predicted by an average of 4.08 diopters (D) for the SRK II formula, 3.91 D for the SRK/T formula, and 4.01 D for the Holladay emmetropia/ametropia formula. Removing the silicone oil from two eyes several months after cataract extraction reduced the deviation from the predicted refraction to 0.25 and 0.80 D. CONCLUSION: The presence of silicone oil in the vitreous space induces a hyperopic shift in eyes having ECCE and IOL implantation. This hyperopic shift should be considered when calculating the IOL power if a long-term tamponade with the oil is planned. If the silicone oil is to be removed shortly after the cataract extraction, the IOL power should be calculated solely from the formula.

Adult↗
PubMed1997

Ocular growth in newborn rabbit eyes implanted with a poly(methyl methacrylate) or silicone intraocular lens.

PURPOSE: To examine eye growth in lensectomized infant rabbits implanted with a poly(methyl methacrylate) (PMMA) or a silicone intraocular lens (IOL). SETTING: S:t Eriks Eye Hospital, Karolinska Institute, Stockholm, Sweden. METHODS: Two groups of 3-week-old rabbits were used. In Group 1 (n = 13), lensectomy was performed in both eyes. In one randomly selected eye, a +30 diopter (D) heparin-surface-modified (HSM) PMMA IOL was implanted in the capsular bag; the other eye was left aphakic. In Group 2 (n = 10), a +21 D HSM PMMA IOL was implanted in one randomly selected eye and a +21 D silicone IOL was implanted in the other. Axial length, corneal diameter, corneal thickness, and intraocular pressure (IOP) were measured in all eye preoperatively and 1, 2, and 3 months after surgery. The wet mass of the after-cataract was measured 3 months after surgery. The ciliary body with the ciliary processes and the peripheral retina were examined histologically after formalin fixation. The two IOL types were compressed to 7.0 MM, corresponding to the diameter of the 3-week-old rabbit lens. RESULTS: In Group 1, the axial length was significantly decreased in the eye with an HSM PMMA IOL compared with the fellow aphakic eye (P < .01, two-way analysis of variance [ANOVA]). No significant difference in corneal diameter, corneal thickness, or IOP was found between the eyes. The wet mass of the dissected after-cataract was significantly less in the eye implanted with an IOL. Two animals had an elevated IOP with secondary glaucoma in their aphakic eye and were excluded from the study. In Group 2, axial length in eyes with the HSM PMMA IOL was less than in the eyes with the silicone IOL (P < .25, two-way ANOVA). No difference in corneal diameter, corneal thickness, or IOP was found. The amount of after-cataract was not altered. Histologically, the eyes with the HSM PMMA IOL showed retinal degeneration, neovascularization of the ciliary body accompanied by a large number of inflammatory cells, and tumid ciliary processes. The eyes with the silicone IOL showed only minor changes. The aphakic eyes presented even less histological change. The compression test demonstrated that three time the compression force was needed to squeeze the HSM PMMA lens than the silicone IOL. CONCLUSION: The results suggest that in the young rabbit eye, implanting a regular size HSM PMMA IOL destroys intraocular tissues and reduces eye growth significantly. Replacing the PMMA IOL with a silicone IOL improves the ocular growth.

Animals↗
PubMed1999

Capsule contraction after continuous curvilinear capsulorhexis: poly(methyl methacrylate) versus silicone intraocular lenses.

PURPOSE: To evaluate the progressive contraction of the anterior capsule opening after in-the-bag implantation of 2 types of intraocular lenses (IOLs). SETTING: Department of Ophthalmology, University of Brest, Brest, France. METHODS: In this prospective study, 32 single-piece poly(methyl methacrylate) (PMMA) (Pharmacia 812 C) and 30 3-piece silicone IOLs with PMMA haptics (Allergan SI-40NB) were implanted in the bag after standardized phacoemulsification performed by the same surgeon. All patients were older than 70 years, and none had zonular weakness. The surface of continuous curvilinear capsulorhexis (CCC) was measured 1, 30, and 150 days postoperatively using a 3 charge-coupled device camera and a digitized computer analysis system. RESULTS: A significant progressive constriction was observed at 150 days in 70% in the silicone group and 32% in the PMMA group. In addition, CCC contraction was greater in silicone group (P < .05). The mean surface decrease was 4.20 mm2 in the silicone group and 1.53 mm2 in the PMMA group. There was no correlation between sex, age, initial capsulorhexis area, final capsule shrinkage. In some eyes, especially in those with a single-piece PMMA IOL (41%), there was no constriction, but fine changes in the capsule opening were seen. CONCLUSION: Evolutive anterior capsulorhexis modifications were observed in all patients; however, the contraction rate was statistically higher in the silicone group. These results suggest that silicone IOL implantation should be avoided in eyes at risk for CCC constriction.

Aged↗
PubMed1998

Monitoring specific interaction of low molecular weight biomolecules on oxidized porous silicon using ellipsometry.

Porous silicon dioxide surfaces have been used for monitoring the specific affinity binding of low molecular weight molecules to streptavidin. Streptavidin was immobilized to the porous silicon dioxide surface by spontaneous adsorption at pH 7.4. Binding of biotin and an oligopeptide synthesized by means of combinatorial chemistry were monitored with an in situ null ellipsometer. Measurements were also done with hydroxy-azobenzene-2-carboxylic acid and DL-6-8-thioctic acid amide. The performance of porous silicon dioxide as a potential surface in biosensor applications was compared with a planar silicon dioxide surface. Porous silicon dioxide showed a 10-fold amplification of the response compared to planar silicon dioxide. It was possible to monitor the binding of biotin and the oligopeptide in the concentration range 2-40 microM. A response time as low as 30 s was obtained for the oligopeptide at 40 microM.

Adsorption↗
PubMed2003

Got silicon? The non-essential beneficial plant nutrient.

Research on a possible nutritional role for the element silicon has been hampered by the diverse beneficial effects that it has on monocots and dicots, and the subsequent difficulties in focusing studies on a single genetic model system. Although deemed a non-essential nutrient for the majority of plants, the benefits of silicon include increasing pest and pathogen resistance, drought and heavy metal tolerance, and the quality and yield of agricultural crops. Although the pathways and molecular mechanisms by which silicon is absorbed and deposited in plants are still unclear, recent progress has been achieved through the use of rice mutants that are deficient in silicon uptake. Additionally, the application of electron-energy-loss spectroscopy (EELS) allows one to determine the composition of silica deposits conclusively. Thereby shedding light upon the role of silicon in heavy metal tolerance. With the complete sequence of the genomes for a dicot (Arabidopsis) and a monocot (rice) available for large-scale genetic analysis, the future bodes well for a more complete understanding of the biological role of silicon and its mode of transport into and through plants.

Adaptation, Physiological↗
PubMed2003

Macro-/nanoporous silicon as a support for high-performance protein microarrays.

The present work demonstrates the possibilities of using macroporous silicon as a substrate for highly sensitive protein chip applications. The formation of 3D porous silicon structures was performed by electrochemical dissolution of monocrystalline silicon. The fabricated macroporous silicon network has a rigid spongelike structure showing high uniformity and mechanical stability. The microfluidic properties of the substrates were found to be essential for a good bioassay performance. Small spot area, good spot reproducibility, and homogeneous spot profiles were demonstrated on the substrates for immobilized aRIgG. Water contact angles were measured on the porous surface and compared to that of planar silicon, silanized glass, and ordinary microscope glass slides. The effect of the porous surface on the performance of a model IgG-binding immunoassay is presented. aRIgG was microdispensed onto the chip surface forming a microarray of spots with high affinity for the target analyte. The dispensing was performed using an in-house-developed piezoelectric flow-through dispenser. Each spot was formed by a single droplet (100 pL) at each position. The macroporous silicon allowed a high-density microarraying with spot densities up to 4400 spots/cm2 in human plasma samples without cross-talk and consumption of only 0.6 pmol of antibodies/1-cm2 array. Antigen levels down to 70 pM were detected.

Antibodies↗
PubMed2006

Total platinum concentration and platinum oxidation states in body fluids, tissue, and explants from women exposed to silicone and saline breast implants by IC-ICPMS.

Ion chromatography-inductively coupled plasma-mass spectrometry was used to determine the total platinum concentration and platinum oxidation states in samples from women exposed to silicone and saline breast implants. Samples included the following: whole blood, urine, hair, nails, sweat, brain tissue, breast milk, and explants. Mean Pt concentration in samples from women exposed to silicone breast implants were as follows: whole blood, 568.1 +/- 74.77 pmol/L (n = 9); urine, 1.77 +/- 0.847 mug/g of creatinine (n = 10); hair, 2.13 +/- 2.984 ng/g (n = 9); nails, 0.88 +/- 0.335 ng/g (n = 9); sweat, 1.90 +/- 1.691 ng/g (n = 9); breast milk, 1.09 +/- 0.316 mug/L (n = 6). Pt in explanted silicone breast implant gel (n = 9) occurred mainly in the +2, +4, and +6 oxidation states. Pt in whole blood (n = 7) and breast milk samples (n = 6) from women exposed to silicone breast implants occurred mainly in the +2 and +4 oxidation states. Saline breast implant fluid (n = 2) did not contain detectable levels of Pt. This is the most comprehensive report, to date, to show that women exposed to silicone breast implants have Pt levels that exceed that of the general population, and the first report, to date, to document the various Pt oxidation states present in samples from women exposed to silicone breast implants.

Adult↗
PubMed2004

Effects of silicone acrylate on morphology, kinetics, and surface composition of photopolymerized acrylate mixtures.

Films (ca. 150 microm thick) of twelve acrylate mixtures, which contained various proportions of hydrocarbon acrylates [mainly oligo(ethylene glycol) diacrylate, (OEGDA)] and small amounts of a silicone hexaacrylate (in proportion of 5% or less), were cured on a nickel substrate, and X-ray photoelectron spectroscopy analysis of the nickel-side surface compositions showed that for formulations with and without the silicone hexaacrylate, this surface was enriched with OEGDA and saturated (up to 50%) with the silicone hexaacrylate, respectively. The silicone hexaacrylate phase-separated and formed micelles which migrated to the resin-nickel interface. Silicone hexaacrylate, inherently less reactive, also significantly slowed the photopolymerization of the mixtures. The sequential homopolymerization of OEGDA and silicone hexaacrylate in a formulation was elicited using real-time Fourier transform infrared spectroscopy. The design-of-experiment approach was used to quantify the influence of the components on gelation time and the nickel-side surface composition as well as provide the statistical models to predict these two properties for new compositions.

Acrylates↗
PubMed2007

Identification and dynamics of proteins adhering to the surface of medical silicones in vivo and in vitro.

Silicone has been used in medical practice as a paradigmatic implant material for decades despite significant detrimental side effects. Our targeted proteomics approach was aimed at identification of the proteins adsorbed to the surface of silicone because they have been characterized as key components in the onset and perpetuation of local immune reactions to silicone. The composition of the proteinacious film, the dynamics of protein deposition, and protein modifications after adsorption were analyzed both in vivo and in vitro. Differential analysis of protein deposition was performed, followed by protein identification with mass spectrometry, database matching, and Western blots. Thus far, we have identified the 30 most abundant proteins deposited on the surface of silicone, the largest known inventory of such proteins so far. Structural and extracellular matrix proteins predominated, followed by mediators of host defense, metabolism, transport, and stress related proteins. In addition, several biochemical modifications of fibronectin, vitronectin, and heat shock protein 60 were detected. Our analyses also revealed previously undetected proteins deposited on the surface of silicone. As tentative initiators and/or modulators of the response to silicone, they are therefore valuable candidates for prognosis and therapy.

Adsorption↗
PubMed1997

Bacterial evolution and silicon.

This review examines the possible role of silicon in molecular evolution. It is possible silicon participated in early molecular evolution by providing a stable mineral surface or gel structure where the assembly and replication of primitive genetic information occurred. However, as molecular evolution proceeded, silicon was not required in the evolution of C-based organisms. Silicon can be accumulated by diatoms and other living organisms such as silicoflagellates, some xanthophytes, radiolarians and actinopods and plants such as grasses, ferns, horseradish, some trees and flowers, some sponges, insects and invertebrates and bacteria and fungi. Silicon also has a role in synthesis of DNA, DNA polymerase and thymidylate kinase activity in diatoms. It is not unreasonable to examine the role of silicon in early molecular evolution as it may have been part of a micro-environment in which assembly of genetic information occurred.

Animals↗
PubMed1999

Silicone-covered metal stents: an in vitro evaluation for biofilm formation and patency.

Self-expanding metal stents are being used more commonly to prevent biliary tract obstruction. Silicone-covered self-expanding metal stents (Wallstent, Schneider, Inc.) have been developed to prevent tumor ingrowth. Biofilm formation and occlusion material in silicone-covered self-expanding metal stents compared to standard polyethylene stents were examined in an in vitro model. Matched pairs of polyethylene and silicone-covered metal stents were perfused with infected bile for 8, 12, and 16 weeks at a rate of 0.5 cc/min at 37 degrees C. Two reservoirs fitted with silicone-covered metal stents had ampicillin/sulbactam added and were perfused for 16 weeks. The stents were then analyzed by scanning electron microscopy and light microscopy for biofilm formation and presence of occlusion material. The two ampicillin/sulbactam-treated stents showed no biofilm formation. Biofilm was seen on all of the remaining stents. There was a difference in occlusion thickness between the 8- and 16-week polyethylene stents, and no difference between the biofilm thickness at 8, 12, or 16 weeks in the silicone-covered metal stents. Silicone-covered self-expanding metal stents will likely extend patency rates in malignant obstructive jaundice by providing a larger lumen for bile flow and allowing cyclical antibiotics to prevent bacterial biofilm formation.

Ampicillin↗
PubMed2004

Outcome of complex retinal detachment surgery after silicone oil removal.

BACKGROUND AND OBJECTIVE: To evaluate anatomical prognosis after silicone oil removal. PATIENT AND METHODS: Sixty-eight eyes which underwent silicone oil removal were enrolled into the study. The underlying ocular pathology for pars plana vitrectomy, surgical methods, and time of silicone oil removal were analysed. RESULTS: Sixteen of 68 eyes (23.5%) redetached following the removal of silicone oil. According to etiology redetachment rates: PVR C 9.5% (2/21), PVR D 25% (4/16), trauma without intraocular foreign body 27.3% (3/11), with intraocular foreign body 33.3% (2/6), giant retinal tear 37.5% (3/8), and proliferative diabetic retinopathy with tractional retinal detachment 33.3% (2/6). The rate of redetachment was 22% in patients with encircling band and 27.8% without encircling band. Retina was redetached in the first 10 days in 81.3% of patients after silicone oil removal. CONCLUSION: The residual vitreoretinal traction especially at the vitreous base is the most likely reason for retinal redetachment after silicone oil removal, which is most commonly seen during the first 10 days.

Adolescent↗
PubMed2004

Comparative investigation of the biocompatibility of various silicon nitride ceramic qualities in vitro.

There is a controversy about the biocompatibility of silicon nitride ceramics contained in the literature, which appears to be related to a factor of the individual chemical composition of different qualities of silicon nitride ceramics and of the different surface properties. This study attempts to investigate the cytotoxicity of different qualities of industrial silicon nitride ceramics applying an L929-cell culture model in a direct contact assay combined with a cell viability assessment. Five different qualities of industrial standard silicon nitride ceramics were chosen for in vitro testing. The chemical composition was determined by EDS analysis. Different biomedically approved aluminium oxide qualities, a titanium alloy, glass and polyvinylchloride (PVC) served as control materials. L929 mice fibroblasts were incubated directly on the materials for 24 h, stained with bisbenzimide and propidium iodine for double fluorochromasia viability testing, and evaluated by inversion-fluorescence microscopy to control cell morphology, viability and cell counts compared to empty well values. Scanning electron microscopy was applied to additionally investigate cell morphology. There was no observation of cytotoxic effects on the silicon nitride ceramic samples; moreover cell morphology remained the same as on aluminium oxide and titanium. Viability testing revealed the presence of avital cells exclusively on PVC, which served as a negative control. Cell counts on all polished surfaces showed significantly higher numbers, whereas some rough surface samples showed significantly lower numbers. We conclude that silicon nitride ceramics show no cytotoxic effects and should be considered for biomedical application owing to its favourable physiochemical properties, especially its superior resistance to mechanical stress, which would be useful for compression loaded conditions. Polished surfaces would appear to promote advanced biocompatibility.

Aluminum Oxide↗
PubMed1999

Pachometry before and after vitrectomy with silicone oil injection.

PURPOSE: To evaluate differences in central corneal thickness (CCT) before and after vitrectomy with injection of silicone oil as vitreous substitution material in order to determine whether silicone oil causes more frequent and/or pronounced corneal decompensation than other substitution materials. METHODS: CCT was measured by ultrasonic pachometry in 42 eyes. 25 eyes received injection of silicone oil and 17 eyes C3F8, atmospheric air or saline. Measurements were performed 24 hours pre operatively, during anaesthesia pre operatively and 24 hours, 48 hours and five months post operatively. RESULTS: A progressive central corneal thickening could be demonstrated in both groups. Eyes which received silicone oil showed maximum CCT increase of 0.083 mm (14.1%) 48 hours post operatively. At follow-up CCT had decreased to baseline value in both groups. Silicone oil did not induce CCT changes that were significantly different from those induced by other substitution materials. CONCLUSION: Silicone oil injection in detachment surgery induces reversible corneal decompensation to the same degree as other substitution materials within the first five months post operatively.

Adult↗
PubMed1999

Scanning laser polarimetry via intravitreal silicone oil.

PURPOSE: To investigate whether scanning laser polarimetry, a promising new technique for early detection of glaucomatous nerve fiber loss, is a suitable method to measure retinal nerve fiber layer thickness in eyes with intravitreal silicone oil. PATIENTS AND METHODS: Eleven eyes of 11 consecutive patients two days to 16 months after successful vitrectomy and intravitreal silicone oil injection and 12 eyes of 12 consecutive subjects, who never had any vitreoretinal surgery were examined using the GDx Nerve Fiber Analyzer. Three individual images were computed to a mean image using the software in each case. RESULTS: "Variance", a software-provided parameter, which represents the differences between the individual images used to calculate the mean image was higher in the "silicone oil" group (unpaired t test for different variances, p = 0.02). Good-quality mean images with a "Variance" value similar to that of the control eyes were obtained in seven of the 11 cases. Characteristic artifacts caused by intravitreal silicone oil were observed in five of the 11 cases. CONCLUSION: Successful scanning laser polarimetry is possible after vitrectomy and intravitreal silicone oil injection, and may help to monitor the retinal nerve fiber layer of these eyes in case of silicone oil induced glaucoma.

Adult↗