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At least 991 records · Page 55Linked to original sources
PubMed1997

Surgical management of posteriorly dislocated silicone plate haptic intraocular lenses.

PURPOSE: To report a large series of delayed posterior dislocation of silicone plate haptic intraocular lenses after Nd:YAG laser capsulotomy and discuss the surgical management of this complication. METHODS: We reviewed the records of 11 consecutive patients (11 eyes) with delayed onset of posterior dislocation of a plate haptic silicone intraocular lens. The cause of the posterior capsular defect, time to dislocation, surgical management techniques, complications, and visual outcome were recorded. RESULTS: In eight of the 11 eyes, the silicone plate haptic intraocular lens dislocated an average of 1.8 months (range, 0 to 6.5 months) after Nd:YAG posterior capsulotomy. The other three eyes had surgical complications at the time of cataract extraction that compromised posterior capsular or zonular integrity and led to silicone plate haptic intraocular lens dislocation from 9 weeks to 6 months (mean, 3.6 months) postoperatively. Surgical management consisted of pars plana vitrectomy with intraocular lens repositioning (six eyes) or exchange (five eyes). The average follow-up period after intraocular lens repositioning or exchange was 6.5 months (range, 1 to 14 months). Best-corrected visual acuity at the last follow-up examination measured 20/40 or better in all but one eye that had preexisting macular disease. CONCLUSIONS: Cataract surgeons and patients should be aware of the potential for plate haptic silicone intraocular lenses to undergo delayed posterior dislocation through capsular defects. This complication can be managed effectively with vitrectomy and either repositioning or exchange of the implant. Postoperative visual acuity is generally excellent, and complications are minimal.

Adult↗
PubMed1994

Silicone intubation without intranasal fixation for treatment of congenital nasolacrimal duct obstruction.

PURPOSE: We assessed the efficacy and morbidity of silicone intubation without intranasal fixation to treat congenital nasolacrimal duct obstruction. METHODS: Forty eyes of 30 consecutive patients underwent silicone intubation to treat congenital nasolacrimal duct obstruction. The ends of the silicone tubing were tied together with a single square knot and were allowed to retract into the nose without intranasal fixation. Tubing removal was performed in the office via the medial canthus in all patients. No attempt was made to reposition prematurely dislodged tubing. RESULTS: The success rate for this series was 38 (95%) of 40 eyes in 29 (97%) of 30 patients. Of seven eyes that required unplanned early tubing removal for dislocated tubing, five eyes nevertheless showed complete resolution of nasolacrimal duct obstruction. Only one patient underwent a second silicone intubation under general anesthesia. CONCLUSIONS: Silicone intubation without the use of intranasal fixation is an effective strategy for treating congenital nasolacrimal duct obstruction. It spares most patients from a second procedure under general anesthesia and achieves success rates comparable to previous studies in which more complex techniques were used.

Child↗
PubMed1993

Dystrophic calcification of silicone scleral buckling implant materials.

In six patients, removal of solid silicone scleral buckling implant materials that had been in place between eight and 21 years disclosed gray-white deposits firmly adherent to the silicone. Four of the six patients had culture-proven infections, whereas two had no evidence of infection and had negative cultures. One of these two patients, however, had intermittent pain, which was the indication for removal of the implant. Analysis of the deposits disclosed that they were calcium phosphate. The exact mechanism responsible for the calcification on the silicone material is unknown. Dystrophic calcification can occur without infection in injured tissue wherein extracellular deposits of devitalized cells, blood cells, and lipids may act as a nidus for calcification. In the presence of infection, bacteria may serve as such a nidus. Additionally, it is possible that biofilm produced by the bacteria had a role in the deposition of calcium phosphate, as well as in its firm adhesion to the silicone materials. We considered the possibility of similar deposits developing on intraocular silicone lenses.

Adolescent↗
PubMed1997

Silicone-coated polypropylene hollow-fiber oxygenator: experimental evaluation and preliminary clinical use.

BACKGROUND: A membrane oxygenator consisting of a microporous polypropylene hollow fiber with a 0.2-microm ultrathin silicone layer (cyclosiloxane) was developed. Animal experimental and preliminary clinical studies evaluated its reliability in bypass procedures. METHODS: Five 24-hour venoarterial bypass periods were conducted on dogs using the oxygenator (group A). In 5 controls, bypass periods were conducted using the same oxygenator without silicone coating (group B). As a preliminary clinical study, 14 patients underwent cardiopulmonary bypass with the silicone-coated oxygenator. RESULTS: Eight to 16 hours (mean, 12.2 hours) after initiation of bypass, plasma leakage occurred in all group B animals, but none in group A. The O2 and CO2 transfer rates after 24 hours in group A were significantly higher than at termination of bypass in group B (p < 0.005 and p < 0.03, respectively). Scanning electron microscopy of silicone-coated fibers after 24 hours of bypass revealed no damage to the silicone coating of the polypropylene hollow fibers. In the clinical study, the oxygenator showed good gas transfer, acceptable pressure loss, low hemolysis, and good durability. CONCLUSIONS: This oxygenator is more durable and offers greater gas transfer capabilities than the previous generation of oxygenators.

Animals↗
PubMed2001

Biocompatibility of silicon-based arrays of electrodes coupled to organotypic hippocampal brain slice cultures.

In this study we examined the passive biocompatibility of a three-dimensional microelectrode array (MEA), designed to be coupled to organotypic brain slice cultures for multisite recording of electrophysiological signals. Hippocampal (and corticostriatal) brain slices from 1-week-old (and newborn) rats were grown for 4-8 weeks on the perforated silicon chips with silicon nitride surfaces and 40 microm sized holes and compared with corresponding tissue slices grown on conventional semiporous membranes. In terms of preservation of the basic cellular and connective organization, as visualized by Nissl staining, Timm sulphide silver-staining, microtubule-associated protein 2 (MAP2) and glial fibrillary acidic protein (GFAP) immunostaining, the slice cultures grown on chips did not differ from conventionally grown slice cultures. Neither were there any signs of astrogliosis or neurodegeneration around the upper recording part of the 47-microm-high platinum-tip electrodes. Slice cultures grown on a separate set of chips with platinum instead of silicon nitride surfaces also displayed normal MAP2 and GFAP immunostaining. The width of the GFAP-rich zone (glia limitans) at the bottom surface of the slice cultures was the same ( approximately 20 microm) in cultures grown on chips with silicon nitride and platinum surfaces and on conventional insert membranes. The slice cultures grown on chips maintained a normal, subfield differentiated susceptibility to the glutamate receptor agonist N-methyl-D-aspartate (NMDA) and the neurotoxin trimethyltin (TMT), as demonstrated by the cellular uptake of propidium iodide (PI), which was used as a reproducible and quantifiable marker for neuronal degeneration. We conclude that organotypic brain slice cultures can grow on silicon-based three-dimensional microelectrode arrays and develop normally with display of normal subfield differentiated susceptibilities to known excito- and neurotoxins. From this it is anticipated that the set-up, designed for recording of electrophysiological parameters, can be used for long-term studies of defined neuronal networks and provide valuable information on both normal, neurotoxicological and neuropathological conditions.

Animals↗
PubMed2004

Retinal toxicity of intravitreal ganciclovir in rabbit eyes following vitrectomy and insertion of silicone oil.

BACKGROUND: Although intravitreal ganciclovir dosages up to 500 microg have been demonstrated to be safe in some studies, other studies have shown toxic retinal effects in rabbit eyes without silicone oil at lower dosages. In current clinical practice, the same dosage of intravitreal antiviral agent is given regardless of whether there has been retinal detachment repair with silicone oil. We performed a study to investigate, in rabbit eyes following vitrectomy and silicone oil insertion, the retinal toxicity of serial intravitreal injections of ganciclovir, using dosages previously found not to produce significant toxic effects in nonvitrectomized eyes. METHODS: Twenty-eight eyes of 14 New Zealand pigmented rabbits underwent pars plana vitrectomy and silicone oil insertion. One eye of each animal received an intravitreal ganciclovir injection twice weekly for 2 weeks. The other eye received 0.1 mL of normal saline as a control. Three dosages of ganciclovir (50, 100 or 200 microg/0.1 mL) were used in three groups of three to six animals. Scotopic electroretinography and histologic examination were performed 2 weeks postoperatively. RESULTS: No differences in scotopic b-wave threshold (p = 0.23, 0.78 and 0.50 for ganciclovir dosages of 50, 100 and 200 microg/0.1 mL respectively, Mann-Whitney U test) or in light microscopy findings were noted between the treatment and control eyes at any dosage of ganciclovir. Surgical complications were observed in eight eyes; the data for these eyes were not used for analysis. INTERPRETATION: Ganciclovir dosages of up to 200 microg/0.1 mL appear to be safe for serial intravitreal injection in rabbit eyes following vitrectomy and silicone oil insertion.

Animals↗
PubMed2003

Penetration and loading of human serum albumin in porous silicon layers with different pore sizes and thicknesses.

Human serum albumin was adsorbed into porous silicon layers with thickness up to 3 microm and with different mean pore radius in the range 4.5-10 nm. The adsorbed amount of protein was quantified by I(125) radioactive labeling techniques and ellipsometry. The results show that albumin penetrated into the pores when the mean pore radius was larger than 5.5 nm, but could not totally occupy the available surface area when the layer thickness was larger than 1 microm. Loading of albumin both into porous layers and onto plane silicon as a function of albumin concentration was also investigated. These measurements show that loading of protein increased with protein concentration at least up to 10 mg/ml for porous silicon and up to 1 mg/ml for plane silicon. The maximum deposition into the type of porous layers used here was 28 microg/cm(2), compared to 0.36 microg/cm(2) for plane silicon.

Adsorption↗
PubMed1999

Wettability of silicone rubber maxillofacial prosthetic materials.

STATEMENT OF PROBLEM: Maxillofacial prosthetic materials that contact skin or mucosa should have good wettability. A material that is easily wetted will form a superior lubricating layer between the supporting tissues and, thus, reduce friction and patient discomfort. The surface energy of a maxillofacial prosthetic material will give an indication of the amount of energy available for adhesion and of the susceptibility of the material to bacterial adhesion. PURPOSE: This study evaluated the wettability and surface energies of a range of commercially available silicone rubber maxillofacial prosthetic materials. MATERIAL AND METHODS: Contact angles and surface energies were measured by using a dynamic contact angle measuring technique. Four commonly used silicone maxillofacial materials were tested and their properties compared with those of an acrylic resin denture base material and a widely used denture soft lining material. RESULTS: There were no significant differences in the wettability of the silicone rubber materials. All materials were significantly less wetted than the denture acrylic resin material. There were no significant differences in the surface energies of the silicone rubber materials, but all were significantly lower than denture acrylic resin material. CONCLUSIONS: The Cahn dynamic contact angle analyzer was a quick and reproducible method for determining the contact angles and surface energies of maxillofacial materials. Further work is needed to improve the wettability of silicone rubber materials used for maxillofacial prostheses, thus, reducing their potential to produce friction with tissues.

Acrylic Resins↗
PubMed1997

Clinical and laboratory evaluation of a new thin-walled self-expanding tracheobronchial silicone stent: progress and pitfalls.

BACKGROUND: Although widely established in the management of malignant airway lesions, currently available tracheobronchial prostheses made of silicone have their drawbacks resulting from rigidity and wall thickness. Therefore we present clinical follow-up data obtained with a novel thin-walled expandable prototype silicone airway stent (Polyflex stent, Willy Rüsch AG, Kernen, Germany) in 19 patients. METHODS: Seventeen of 19 patients had tracheobronchial complications of infiltrating cancer: five had respiratory-digestive fistulas, 14 had mixed-type obstructions (mucosal infiltration plus extrinsic compression), and two had diffuse tracheal hemorrhages from the tumor surface (three patients had more than one complication). Two of 19 patients had benign postintubation stricture and malacia. Overall, 33 stents were implanted either simultaneously or in a consecutive manner. Scanning electron microscopy was performed both on prototype stents and on other available silicone stents for comparison. RESULTS: The treatment improved the patients' clinical condition substantially. The mechanical properties of the new prosthesis were excellent. Important stent-associated side effects were early mucus retention (n = 7), infolding of the inner silicone layer (n = 2), and stent dislodgment (n = 2). As of February 1997, 10 patients have died of causes unrelated to stent placement. Seven patients with malignant airway disease are still alive from 2 weeks up to 7 months after initial treatment. Scanning electron microscopy of explanted and unused prototypes suggested that an extremely ragged luminal microstructure may contribute to the firm adhesion of secretory material and that technical smoothing of the surface avoids such complications. CONCLUSIONS: The novel self-expandable silicone airway stent may be a promising addition to commonly used stent types. Short-term and medium-term management of fistulas, tumor surface bleeding, and strictures (malignant and benign) is satisfactory. Scanning electron microscopy of stents provides information on peculiar features of microstructure and material that may be of use in clinical research and technical innovation.

Adult↗
PubMed1993

Bladder outlet reconstruction: fate of the silicone sheath.

The placement of a 1.5 cm. wide silicone sheath around a newly constructed urethra/bladder neck to ensure maintenance of repair length and to facilitate future placement of a sphincter cuff was reported by our institution in 1985. We present our long-term followup and new recommendations for use of the silicone sheath. A total of 15 silicone sheaths was placed between March 1981 and July 1984. Of the sheaths 14 were placed at the time of urinary reconstruction around the Young-Dees-Leadbetter bladder neck repair and 1 was placed after erosion of an artificial urinary sphincter cuff. Of the 15 sheaths 10 have eroded into the urethra and 4 sheaths remain in situ. Another sheath was replaced 2 years after its original insertion with an artificial urinary sphincter cuff. Mean time to erosion was 48.2 months, with a range of 2 to 108 months. Long-term followup of 10 patients revealed that 4 ultimately required ligation of the bladder neck and construction of continent stoma after erosion, 1 is dry after placement of a bulbar artificial urinary sphincter, 2 remain dry after removal of the eroded sheath alone, 2 required bladder neck revision to achieve continence after erosion and the most recent patient remains diverted with a suprapubic tube. All 4 patients with sheaths still remaining are dry without evidence of erosion (mean duration 116 months). These long-term results using a silicone wrap around a newly constructed bladder neck reveal an unacceptably high rate of erosion. Therefore, we no longer recommend or support the use of the silicone sheath in the manner we have described for bladder neck reconstruction.

Adolescent↗
PubMed1999

Influence of glass composition on the properties of glass polyalkenoate cements. Part I: influence of aluminium to silicon ratio.

Hydrolysis of aluminium-oxygen-silicon bonds is thought to be the first step in the setting reaction of polyalkenoate cements and the aluminium to silicon ratio of the glass is widely believed to be a dominant factor determining cement properties. The properties of glass polyalkenoate cements based on the generic glass composition (6 + X)SiO2 x (4 - X)Al2O31.5P2O5 x 4CaOCaF2 with varying aluminium to silicon ratio were studied. Setting and working times of the cement pastes, compressive strength, un-notched fracture strength, Young's modulus, fracture toughness and toughness were evaluated for the cements. In contrast to previous studies the aluminium to silicon ratio was not found to influence the cement properties significantly. The high phosphorus content of the glasses studied is thought to reduce the influence of the aluminium to silicon ratio of the glass, as a result of phosphorus locally charge balancing four coordinate aluminium ions in the glass network, as well as providing an additional mechanism of degradation in the form of hydrolysable phosphorus-oxygen bonds.

Aluminum Compounds↗
PubMed2003

Comparison of silicone oil versus gas tamponade in the treatment of idiopathic full-thickness macular hole.

PURPOSE: To compare anatomic and functional outcomes of macular hole surgery with either silicone oil or C(3)F(8) gas tamponade. DESIGN: Retrospective comparative interventional study. PARTICIPANTS: Fifty-four eyes of 51 patients underwent pars plana vitrectomy for macular holes. Thirty-one eyes were treated with silicone oil tamponade, and 23 eyes were treated with C(3)F(8) tamponade. METHODS: Demographics, preoperative and postoperative characteristics, and complications were analyzed. MAIN OUTCOME MEASURES: Preoperative and postoperative visual acuity, initial hole closure, number of persistent or recurrent holes, number of reoperations, and final hole closure. RESULTS: The silicone oil and gas tamponade groups were demographically similar. The rate of hole closure after one operation with oil tamponade was significantly lower than that with gas tamponade (65% vs. 91%; P = 0.022). The percentage of patients undergoing a second operation was significantly higher in the oil group (35% vs. 4%; P = 0.006). However, with reoperations, the final rate of hole closure was similar between the oil and gas groups (90% vs. 96%; P = 0.628). The final median visual acuity for the gas group was significantly better than for the oil group (20/50 vs. 20/70; P = 0.047). CONCLUSIONS: C(3)F(8) gas proved to be a more effective tamponade than silicone oil with respect to achieving initial closure of macular holes. Eyes receiving an oil tamponade required significantly more reoperations to achieve a similar rate of hole closure compared with eyes undergoing a gas tamponade. Final visual acuity was better for gas-operated eyes than for silicone-operated eyes.

Aged↗
PubMed1992

A survey of intraocular silicone oil use in the United States.

PURPOSE: This survey was conducted to determine the pattern of usage of intravitreal silicone oil in the United States. METHODS: A questionnaire was sent to 542 members of the Retina and Vitreous Societies in December 1990, and again 6 weeks later in an attempt to improve the response rate. RESULTS: Two hundred eighty-seven questionnaires (53%) were returned. Ninety-eight percent of the respondents perform vitreous surgery, and 61% of them use silicone oil. This survey determined the degree of participation in Food and Drug Administration (FDA)- and institutional review board-approved protocols and the most common indications for use of silicone oil. Ninety-six percent of the respondents indicated that the use of silicone oil represented an acceptable standard of care. CONCLUSION: Silicone oil is widely used in the United States despite its lack of FDA approval.

Drug Utilization↗
PubMed1999

The effect of polymethylmethacrylate, silicone, and polyacrylic intraocular lenses on posterior capsular opacification 3 years after cataract surgery.

OBJECTIVE: To compare the visual outcome, neodymium:YAG (Nd:YAG) capsulotomy rates, and percentage of posterior capsular opacification (PCO) seen with polymethylmethacrylate (PMMA), silicone, and polyacrylic intraocular lens implants 3 years after surgery. DESIGN: Randomized, prospective trial. PARTICIPANTS: Ninety eyes of 81 patients were examined at a British teaching hospital. INTERVENTION: Ninety eyes were prospectively randomized to receive a PMMA, silicone, or polyacrylic (AcrySof, Alcon, Fort Worth, TX) implant. All lenses had 6-mm disc optics with PMMA haptics. A standardized surgical protocol was performed by a single surgeon using an extracapsular technique with capsulorhexis; any surgical complications were excluded and all patients had standardized postoperative medication and follow-up. MAIN OUTCOME MEASURES: Patients were seen at 6 months and 1, 2, and 3 years after surgery. At 3 years, logarithm of the minimum angle of resolution (LogMAR) visual acuity and Pelli-Robson contrast sensitivity were measured and YAG capsulotomy rates determined. Posterior capsular opacification was assessed objectively by digital retroillumination imaging using dedicated software and calculated as the percentage area of opacified capsule. RESULTS: At 3 years, the overall follow-up rate was 71%: 19 patients were available for examination with polyacrylic lens implants, 22 with silicone, and 23 with PMMA. There was a significant difference in percentage PCO at 3 years among the lens types (P = 0.0001). Polyacrylic lenses were associated with less PCO (10%) than silicone (40%) and PMMA lenses (56%). The YAG capsulotomy rate was 0% for polyacrylic, 14% for silicone, and 26% for PMMA (P = 0.05). The visual acuity and contrast sensitivity were not significantly different among the three groups if patients with age-related macular degeneration and those requiring YAG capsulotomies are excluded. CONCLUSIONS: Intraocular lenses made from polyacrylic are associated with a significantly reduced degree of PCO and lower YAG rates.

Acrylates↗
PubMed2003

Biocompatibility of layer-by-layer self-assembled nanofilm on silicone rubber for neurons.

Electrostatic layer-by-layer (LbL) self-assembly, a novel method for ultrathin film coating has been applied to silicone rubber to encourage nerve cell adhesion. The surfaces studied consisted of precursor layers, with alternating cationic poly(ethyleneimine) (PEI) and anionic sodium poly(styrenesulfonate) (PSS) followed by alternating laminin and poly-D-lysine (PDL) layers or fibronectin and PDL layers. Film growth increased linearly with the number of layers. Every fibronectin/PDL and laminin/PDL bilayer was 4.4 and 3.5 nm thick, respectively. All layers were more hydrophilic than the unmodified silicone rubber surface, as determined from contact angle measurements. Of the coatings studied, a PDL layer was the most hydrophilic. A multilayer film with composition [PSS/PEI]3+[fibronectin/PDL]4 or [PSS/PEI]3+[laminin/PDL]4 was highly favorable for neuron adhesion, in contrast to bare silicone rubber substrate. The film coated on silicone rubber is biocompatible for cerebellar neurons with active viability, as shown by lactate dehydrogenase (LDH) assay and fluorescence cellular metabolism observations. These results demonstrate that LbL self-assembly provides an effective approach to apply films with nanometer thickness to silicone rubber. Such only few nanometer thick films are biocompatible with neurons, and may be used to coat devises for long-term implant in the central nervous system.

Animals↗
PubMed2003

Surface modification of an experimental silicone rubber maxillofacial material to improve wettability.

OBJECTIVES: Good wettability of maxillofacial prosthetic materials is important so that a lubricating layer is formed with supporting tissues thus reducing patient discomfort. The purpose of the study was to surface modify an experimental silicone rubber material in order to improve wettability. METHODS: Samples of experimental silicone rubber were surface modified by first argon plasma treatment followed by chemisorption of ethyleneoxy functional silanes. These were compared with the same silicone rubber which had ethyleneoxy functional surfactants incorporated into the polymer matrix. In all cases contact angles, tear strength and water uptake were measured. RESULTS: Surface modified materials had comparable contact angles to surfactant modified silicone rubber all being significantly lower than the unmodified material. Surface modified materials, however, had a significantly higher tear strength and lower water uptake in comparison to surfactant modified materials. CONCLUSIONS: Argon plasma treatment followed by chemisorption of ethyleneoxy functional silanes proved an effective way of improving the wettability of an experimental silicone rubber maxillofacial prosthetic material without altering bulk properties.

Materials Testing↗
PubMed2002

Comparative examination of complaints of patients with breast-cancer with and without silicone implants.

OBJECTIVE: To measure the relationship between silicone breast implants and various symptoms using a control group. STUDY DESIGN: A matched-pair-analysis of 96 women with breast-cancer (32 with silicone implants (K I); 64 without implants (K II)) was performed with help of a standardized questionnaire in respect to 50 single criteria. The condition of implants was monitored by MR-imaging. RESULTS: Athralgias and myalgias were not significantly more frequent in K I. Only six symptoms were reported significantly more often in patients with implants. Positive correlation with implant rupture was given only for the numb feeling/tingling sensation in extremities (P=0.02). There was no correlation between silicone implants and the symptoms of the "chronic-fatigue syndrome" nor any other described silicone-induced disease. CONCLUSIONS: According to our analysis many of the symptoms examined here are present in middle-aged women regardless of silicone implants and underlying disease.

Adult↗
PubMed2003

Systematic review: efficacy of silicone microimplants (Macroplastique) therapy for stress urinary incontinence in adult women.

OBJECTIVE: To assess the efficacy of silicone microimplants (Macroplastique; polydimethylsiloxane) therapy for stress urinary incontinence in adult women, using a systematic review of identified studies. MATERIALS AND METHODS: A computer-aided and manual search for published studies investigating silicone microimplants therapy for stress urinary incontinence in adult women. The methodological quality of the included studies was assessed using criteria based on generally accepted principles of interventional research. RESULTS: Only two RCTs, only published as an abstract, were found. Eleven pre-experimental or observational studies were identified. Overall, the methodological quality was low. The main methodological shortcomings of the studies were: no random allocation procedure, lack of prestratification on prognostic determinants, no blinding, small sample sizes, and lack of proper analysis and presentation of results. There was variability in the indication for implantation, implantation procedure, rate and volume of silicone microimplants. The use of different outcome measures in most of the trials made comparison between studies difficult. CONCLUSIONS: Because of the low methodological quality of included studies, results should be interpreted with caution and no firm conclusions about the efficacy of silicone microimplants were possible. Randomized clinical trials, using valid and reliable subjective and objective measurements, are necessary to establish the efficacy of silicone microimplants therapy in treating stress urinary incontinence in adult women.

Adult↗