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PubMed2002

[Evidence of silicone oil deposits via high resolution ultrasound].

BACKGROUND: Using biomicroscopy the evidence of deposits of silicone oil in the anterior segment after vitrectomy is limited. We examined the anterior segment by high resolution ultrasound to verify the possibility to identify silicone oil. MATERIALS AND METHODS: Ten patients treated by vitrectomy with instillation of silicone oil were examined by high resolution ultrasound before and after the removal of silicone oil. The duration of silicone oil tamponade was at least 5 months. A 20-MHz-sectorscanner was used for examination. We compared the findings of ultrasound and biomicroscopy with groups of patients with or without pharmacological mydriasis, blue or brown colour of the iris. RESULTS: The patients treated by vitrectomy and instillation of silicone oil showed small high reflective structures at the endothelium, the anterior front of the iris and in the angle. These highly reflective structures were found more often before, less often after operative extraction of silicone oil and could not be shown in the control groups. Using biomicroscopy we could not see an equivalent to all of the highly reflective structures. CONCLUSIONS: The highly reflective structures we found by ultrasound are probably inclusions in endothelial cells, silicone oil-induced calcifications or free particles of silicone oil. High resolution ultrasound with a 20-MHz-sectorscanner can be used for identifying indication and localising of silicone oil in the anterior segment even if biomicroscopic signs are absent.

Anterior Eye Segment↗
PubMed1996

[Clinical experiences after implantation of various lens types in silicon oil tamponade].

BACKGROUND: A tamponade of the vitreous space with silicone oil will obligatory lead to cataract after 6 to 12 months. Today it is easily possible, to implant an artificial lense in silicone oil filled eyes. However the combination of an artificial lense and silicone oil will lead to a strong inflammation in the anterior segment of the eye. PATIENTS AND METHODS: 22 pseudophacic patients with silicone oil tamponade were examined 2 to 6 months after the operation. In 12 patients simple artificial lenses were implanted, in 10 patients heparin modified lenses were implanted. In 10 cases the lens was implanted followed by the insufflation of silicone oil in the vitreous cavity, in 2 cases a lens was implanted in a silicone oil filled eye and the silicon oil was not removed. In 8 cases the implantation of the artificial lens has been performed some months to years before the insufflation of the silicone oil. The indication for the silicon oil tamponade was a PVR retinal detachment in all cases. The following parameters were examined: Reaction of the pupil to light, pupil round or oval in miosis, examination of the fundus peripherie possible after mydriasis, fixation of the iris with parts of the capsula or with the anterior surface of the lens? In addition in 12 cases the postoperative refraction was compared with the results of the biometry, which was performed before the operation. RESULTS: In the cases with a simple lens in about 50% an incomplete miosis or an oval pupil because of fixation of the iris with parts of the capsula or with the anterior surface of the lense could be observed. In the cases with heparin modified lenses these complications could be observed in 20%. In all cases a strong opacification of the capsula was seen. In 8 of 12 cases with combined procedure a small hyperopia was measured, in 4 cases a large deviation was measured. CONCLUSIONS: The implantation of an artificial lens in silicone oil filled eyes is an alternative to the aphacic status with an Ando Iridectomy. Obviously heparin modified lenses have advantages in these cases. Because of the strong cataract formation we suggest to remove the anterior and the posterior capsula in the first operative session and to implant the haptics of the lens into the sulcus. Because of the high rate of complications generally first a stable retina condition should be reached before the implanation of an artificial lens is performed.

Aged↗
PubMed1990

The effects of prior exposure to silicone on capsule formation, histology, and pressure.

Investigations into the effects of prior silicone exposure on subsequent capsule formation around silicone implants assume particular relevance in light of the exponential increase in the medical application of polymers such as silicone. The inert nature of silicone has been in question with regard to its effects on the immune system, specifically whether or not it may act as a hapten or antigen. The present study analyzes the effects of prior silicone exposure on subsequent capsule formation, histological consistency, and pressures when an animal is reexposed to a silicone implant. Twelve female Lewis rats (body weight 250 g) were randomly divided into two groups. Group 1 (n = 6) rats were subcutaneously injected with 2.5 ml of Freund's Complete Adjuvant, Group 2 (n = 6) rats were injected with an equal volume of adjuvant sonicated with silicone gel. At 4 weeks a gel-filled silicone implant was placed subcutaneously in each animal. Capsule pressures were obtained at 4 months and the capsules from 3 rats from Group 2 were excised and examined microscopically. Pressures were measured again at 8 months and all remaining capsules were excised and examined. No statistically significant differences were noted when comparing two profiles over time between silicone-exposed and nonexposed animals in regard to capsule thickness or capsule pressure. However, capsule pressures were significantly lower at 8 months than at 4 months in both groups (p less than 0.034). In this model, significant reductions in capsule pressure were noted in both groups over time, but prior exposure to silicone did not appear to alter capsule histology, thickness, or pressure.

Animals↗
PubMed1996

Silicon tissue assay: are there intracapsular variations?

In previous studies, we were able to demonstrate baseline non-augmented cadaveric silicon tissue values as well as silicone-augmented breast capsular tissue silicon levels from various geographic locations in the United States. One of the limitations of these previous studies was the potential for intracapsular variations in the silicon level and whether a single measurement would be a valid comparison for the entire breast capsule. This study was then undertaken to measure the variations in tissue silicon levels from multiple sites within each breast capsule sampled. Four patients that underwent silicone breast and three tissue expander explantations were evaluated. All the women had silicone implants for breast augmentation and the placement of tissue expanders for reconstruction following mastectomy. A variety of reasons for explantation were noted. Each of the patient's breast capsules were divided into four quadrants (upper inner, upper outer, lower inner, and lower outer). All samples were harvested in a no-touch technique and were sent for silicon tissue assays. Silicon values ranged from 44 to 9,000 micrograms per gram of tissue and were consistent with our previously measured values. We conclude that random samples of breast capsules reflect the variations within the specimen samples, but can be used to measure elevated silicon values accurately. It is our belief that multiple samples do not need to be taken for each capsule measurement and that a previous potential limitation to the measurements has been eliminated.

Adult↗
PubMed1997

Migration of silicone through the fibrous capsules of mammary prostheses.

The usual reaction of the human body to implantation of a silicone prosthesis is formation of a fibrous capsule. Local reactions to silicone outside this fibrous capsule and distant migration of silicone particles have been described. So far, transcapsular migration of silicone particles from the mammary implant through the fibrous capsule of mammary prostheses has not been studied. In this prospective study 71 capsules found in 40 patients were histologically studied. The chi-squared test was applied to evaluate a possible correlation between silicone migration on the one hand and implant age and integrity of the prostheses on the other. The degree of silicone migration was discerned in four stages. Stage 1 represents no silicone particles in the capsule, stage 2 represents migration up to less than half of the capsule thickness, stage 3 shows migration confined to the outer half of the capsule thickness, and stage 4 means transcapsular silicone migration. In only 4 of 71 capsules no migration into or through the capsule was observed. The degree of silicone migration was significantly less in patients in whom the capsule was calcified and was significantly more in patients in whom implantation exceeded 12 years. There was no significant correlation between the status of the prosthesis (intact, bleeding, or ruptured) and the degree of silicone migration.

Adult↗
PubMedDate not supplied

Permeation of silicone oil through a diaphragm in an electrohydraulic ventricular assist system.

This study was designed to investigate the permeation of silicone oil through a pump diaphragm made of Pellethane in the authors' electrohydraulic ventricular assist system (EHVAS) and to evaluate influences on organ function. The permeability of the diaphragm to silicone oil was investigated by in vitro experiments. Influences on organ function were evaluated in five goats with an EHVAS by monitoring serum silicon levels (SSi), blood chemical parameters, and histologic findings. Elevation of silicone oil levels in Pellethane sheets immersed in silicone oil demonstrated that the Pellethane diaphragm was, in fact, permeable to silicone oil. The permeation rate of silicone oil was calculated to be 1.75 ml/year in the authors' EHVAS from the data of a diffusion apparatus test. Serum silicon levels did not increase during the EHVAS pumping, and renal and hepatic function were not affected. No abnormality or deposit suggestive of silicone oil was observed. However, the problem of permeation of silicone oil through the pump diaphragm must be solved to allow for a circulatory assist device for long-term use.

Animals↗
PubMed1998

Efficient in vitro model for immunotoxicologic assessment of mammary silicone implants.

In clinical and experimental studies, silicone gel has been assumed to cause immune alterations that may be related to macrophage activation of silicone implants. However, it has not been proven that the immunotoxicities are caused by the direct contact of macrophages and silicone gel because there has not been an adequate experimental model. In the present study, silicone gel was loaded directly onto Petri dishes and was distributed uniformly to the bottom by centrifugation. Peritoneal macrophages and splenic lymphocytes were cultured either on the silicone-coated plates or on the conventional, normal plates, and their functions were compared with each other. The experiments were repeated three times. The cytotoxic activities of peritoneal macrophages on cancer cells were markedly augmented by cultivation on silicone gel, and the primary T-dependent immunoglobulin M response in which macrophages participated as antigen presenting cells was also enhanced by incubation on silicone gel. However, macrophage-unrelated functions mediated by B and T lymphocytes were not affected by the silicone gel treatment. It was proven that the direct contact of macrophages with silicone gel was a primary cause of acute immune activation that was related to foreign body reaction. In addition, the present in vitro model exhibited similar silicone-induced immunotoxicities in previous animal and clinical studies.

Animals↗
PubMed2001

Pharmacokinetics of the ganciclovir implant in the silicone-filled eye.

PURPOSE: Ganciclovir (GCV) implants are highly effective in delaying the progression of cytomegalovirus (CMV) retinitis. Rhegmatogenous retinal detachments can occur in untreated eyes with CMV retinitis or in eyes treated with anti-CMV therapy, which may include placement of a GCV implant. The clinical management of CMV retinitis and associated retinal detachment often involves the concurrent use of silicone oil and GCV implants. The authors investigated the effect of silicone oil tamponade on intravitreal drug levels achieved with the GCV implant. METHODS: The authors performed gas compression vitrectomy in the right eyes of 29 New Zealand white rabbits. They then inserted a 5-mg GCV implant into the vitreous cavity through an inferotemporal sclerotomy. Saline (1 cc), silicone oil 0.5 cc, or silicone oil 1.0 cc was then injected into the midvitreous cavity of 9, 8, and 12 rabbits, respectively. On postoperative days 21, 42, and 70, the rabbits were killed and the right eyes were immediately collected and stored at -70 degrees C until all samples were obtained. Vitreous was then isolated and drug levels were determined by high-pressure liquid chromatography. RESULTS: Vitreous GCV levels at days 21 and 42 were similar in both the saline-filled and silicone oil-filled eyes. At day 70, GCV levels in both the saline- and silicone-filled eyes were statistically significantly lower than at day 21 (P < 0.05 for all groups). In addition, at day 70, GCV levels in the saline-filled eyes were significantly lower than in silicone-filled eyes (saline versus 0.5 cc oil, P = 0.01; saline versus 1 cc oil, P = 0.09). CONCLUSIONS: Effective GCV levels are maintained in the aqueous phase of the vitreous cavity of eyes with silicone oil tamponade. Ganciclovir levels may be maintained longer in eyes with silicone oil tamponade than in those without. These results support the use of combined GCV implants and silicone oil tamponade in patients with CMV retinitis and associated retinal detachment.

Animals↗
PubMedDate not supplied

Refractive changes in silicone oil-filled pseudophakic eyes.

PURPOSE: We examined the refractive changes in pseudophakic eyes of patients with idiopathic macular hole treated with silicone oil injection. METHODS: Twenty consecutive eyes of 19 patients with idiopathic macular hole who had undergone successful pars plana vitrectomy using silicone oil tamponade were studied retrospectively. Lensectomy with intraocular lens (IOL) implantation was performed on each patient before vitreous surgery. Five biconvex type IOL models were used. After pars plana vitrectomy and fluid-air exchange, silicone oil was injected to replace the air completely. Macular hole closure was confirmed by optical coherence tomography, and silicone oil removal was performed. Manifest refractions before silicone oil filling, with silicone oil filling, and after silicone oil removal were determined. RESULTS: A mean hyperopic shift +/- SD in spherical equivalents of +5.69 +/- 1.71 diopters (P < 0.0001) was observed with silicone oil instillation. In contrast, a mean myopic shift +/- SD of -5.63 +/- 1.33 diopters was observed after silicone oil removal (P < 0.0001). The absolute value of the refractive shift showed a strong correlation with the posterior radius of the IOL (r = 0.699, P < 0.0001). CONCLUSION: IOL models with steeper posterior convex curvature result in larger refractive deviations in patients scheduled for silicone oil instillation.

Aged↗
PubMed2001

Intraocular pressure and silicone oil endotamponade.

PURPOSE: To evaluate intraocular pressure after instillation and eventual removal of silicone oil in patients undergoing pars plana vitrectomy combined with silicone oil endotamponade. METHODS: The study included 198 patients who underwent pars plana vitrectomy with silicone oil endotamponade (5,000 centistoke viscosity), in whom silicone oil was removed and in whom follow-up after oil removal was at least 3 months. All patients were operated on by one of two surgeons. RESULTS: After silicone oil instillation, intraocular pressure increased significantly (P < 0.001) from 12.9 +/- 4.4 mm Hg preoperatively to 16.1 +/- 5.5 mm Hg postoperatively. Intraocular pressure was statistically (P > 0.20) independent of the duration of silicone oil tamponade. Twenty percent of the 198 patients had at least one postoperative intraocular pressure measurement that was higher than 21 mm Hg. Main reasons for increased intraocular pressure were closed inferior iridectomy, iris neovascularisation, silicomacrophagocytic open-angle glaucoma secondary to silicone oil emulsification, and preoperative history of glaucoma. Glaucomatous optic nerve damage was detected in 14 (14 of 198, 7.1%) eyes, including 8 eyes with preoperative antiglaucoma treatment. Silicone oil emulsification occurring in 40 (40 of 198, 20.2%) patients did not statistically influence intraocular pressure after oil removal. Ocular hypotony occurred in 10 (10 of 198, 5.1%) patients after oil release leading to intraocular hemorrhages and loss of vision in 3 patients. CONCLUSION: Clinically significant increased intraocular pressure after pars plana vitrectomy with silicone oil endotamponade occurs relatively rarely, can usually be well controlled by topical antiglaucoma medication, and is reversible in most patients after oil removal. In patients with increased intraocular pressure and silicone oil endotamponade, oil removal may be preferred to invasive antiglaucoma surgery to reduce intraocular pressure.

Adolescent↗
PubMed2002

Setons and serum IgG titers to silicone.

PURPOSE: To determine whether exposure to silicone shunts used in refractory glaucomas increases serum IgG binding to silicone and whether this response is associated with shunt-related complications or poor postoperative intraocular pressure control. METHODS: Sera from 12 patients (13 eyes) who had undergone placement of silicone seton implants were examined for IgG binding to silicone. Patients were monitored postoperatively for the occurrence of complications and intraocular pressure elevation (mean duration of exposure to silicone and follow-up, 25.1 months; range, 2.5-86 months). RESULTS: The levels of serum IgG binding in 4 of the 12 patients were two standard deviations above the mean for control sera. No patients had titers greater than 46 arbitrary units (AU). Four patients developed shunt-related complications; the serum IgG binding to silicone for their sera ranged from 24 to 46 AU. Serum IgG binding values were not significantly correlated with poor postoperative intraocular pressure control, or with a history of autoimmune disease or malignancy, type of glaucoma, previous intraocular surgery, or chronic uveitis. CONCLUSIONS: Although elevation of serum IgG binding to silicone may be noted in some patients receiving silicone seton shunts, individual levels do not seem to predict the development of shunt-related complications. Since the number of patients tested, the frequency of elevated IgG binding values, and the complication rate were relatively low in this study, it is difficult to exclude some clinicopathologic correlations. However, the results are in accord with previous studies of silicone ocular devices suggesting that clinically significant reactions to silicone ophthalmic implants must be rare events, and hence do not necessitate altering the use of these important devices.

Adult↗
PubMed2005

Adhesion of Pseudomonas aeruginosa and Staphylococcus epidermidis to silicone-hydrogel contact lenses.

PURPOSE: The purpose of this study is to compare the adhesion capabilities of the most important etiologic agents of microbial ocular infection to the recently available silicone-hydrogel lenses with those to a conventional hydrogel lens. METHODS: In vitro static adhesion assays of Pseudomonas aeruginosa 10,145, Staphylococcus epidermidis 9142 (biofilm-positive), and 12,228 (biofilm-negative) to two extended-wear silicone-hydrogel lenses (balafilcon A and lotrafilcon A), a daily wear silicone-hydrogel lens (galyfilcon A) and a conventional hydrogel (etafilcon A) were performed. To interpret the adhesion results, lens surface relative hydrophobicity was assessed by water contact angle measurements. RESULTS: P. aeruginosa and S. epidermidis 9142 exhibited greater adhesion capabilities to the extended wear silicone-hydrogel lenses than to the daily wear silicone- and conventional hydrogel lenses (p < 0.05). No statistical differences were found between the adhesion extent of these strains to galyfilcon A and etafilcon A. The biofilm negative strain of S. epidermidis adhered in larger extents to the silicone-hydrogel lenses than to the conventional hydrogel (p < 0.05), but in much lower amounts than the biofilm-positive strain. The water contact angle measurements revealed that the extended wear silicone-hydrogel lenses are hydrophobic, whereas the daily wear silicone- and conventional hydrogel lenses are hydrophilic. CONCLUSIONS: As a result of their hydrophobicity, the extended wear silicone-hydrogel lenses (lotrafilcon A and balafilcon A) may carry higher risk of microbial contamination than both the hydrophilic daily wear silicone-hydrogel lens, galyfilcon A and the conventional hydrogel lens, etafilcon A.

Bacterial Adhesion↗
PubMed2006

Refractive index and equilibrium water content of conventional and silicone hydrogel contact lenses.

PURPOSE: The purpose of the present study was to measure equilibrium water content (EWC) and refractive index of conventional and silicone hydrogel soft contact lenses (SCL) using a hand refractometer and an automated refractometer. METHODS: Sixteen SCL were used in this study including 12 conventional SCL not containing siloxane moieties (equilibrium water content (EWC) range: 38.6-74%) and the four silicone hydrogel based contact lenses currently available (WC range: 24-47%). Two experienced observers performed the measurements in a randomised order being masked by a third party during the three sessions at which the measurements were collected. The Atago N-2E hand refractometer and the CLR 12-70 digital refractometer were used. Data were analysed separately for conventional and silicone hydrogel materials. RESULTS: Measured EWC and refractive index correlate better when measured with the instruments used in this study (r(2) = 0.979, p < 0.001) than the nominal parameters (r(2) = 0.666, p < 0.001). The linear relationship that correlates nominal and measured EWC shows higher spread of data when all lenses are analysed together (r(2) = 0.840) than when conventional hydrogel (r(2) = 0.953) and silicone hydrogel contact lenses (r(2) = 0.967) are analysed separately. Regarding refractive index, the relationship between nominal and measured values when all the lenses are considered together (r(2) = 0.794) becomes weaker when conventional hydrogel are considered separately (r(2) = 0.688), while a stronger relationship is observed for silicone hydrogel lenses (r(2) = 0.939). Hence, hand refractometry overestimates the EWC of silicone hydrogels, while automated refractive index measurements are more accurate in silicone hydrogels than in conventional hydrogels. CONCLUSIONS: New relationships are presented that correlate nominal and measured values of EWC and refractive index for the silicone containing hydrogels. The linear relationships derived fit well to the data. Hand refractometry overestimates the EWC of silicone hydrogel materials and this bias is related to the proportion of siloxane moieties in the material. Conversely, refractive index can be obtained more accurately with automated refractometry for silicone hydrogels than for conventional hydrogels. Present results are of interest in planning future clinical studies involving the measurement of EWC of current hydrogels.

Contact Lenses, Hydrophilic↗
PubMed2001

Outcome after silicone oil removal.

BACKGROUND: Combined with vitreoretinal surgery, silicone oil injection has become a standard technique and improves the prognosis of complex retinal detachment. As silicone oil leads to long term complications, removal of silicone oil from the eye is recommended. To evaluate the outcome after silicone oil removal, retinal redetachment, visual acuity, and complications were analysed. METHODS: The authors analysed 115 consecutive cases of silicone oil removal (115 eyes), all operated by one surgeon. The series consisted of retinal detachments associated with proliferative vitreoretinopathy (103 eyes), proliferative diabetic retinopathy (six eyes), or ocular trauma (six eyes). The mean duration of intraocular silicone oil tamponade was 13.3 months, with a mean postoperative follow up of 1.8 years. RESULTS: Anatomic success after silicone oil removal, defined as a complete retinal attachment, was achieved in 95 of 115 eyes (82.6%). Redetachment occurred in 20 eyes (17.4%), mostly within the first 6 months after silicone oil removal. Including the successfully reoperated eyes, the authors present a final anatomic success rate of 108 eyes (93.9%). Visual acuity improved or remained unchanged in 93 eyes (80.9%). CONCLUSION: While reattachment and complication rates were quite similar to other studies, a better visual outcome was achieved in these cases. The duration of the silicone oil tamponade had no significant effect on the reattachment rate. The authors recommend not to apply standard criteria for the timing of silicone oil removal, but to decide individually, considering the underlying disease, as well as the previous operations.

Adolescent↗
PubMed2004

In vitro analysis of modified surfaces of silicone breast implants.

BACKGROUND: Although silicone breast implants are well tolerated, local complications such as capsular contracture occur because of insufficient integration with surrounding tissues. In this study, cell behaviour on hydrophilized silicone breast implant foils was analysed qualitatively and quantitatively under in vitro conditions in order to provoke the desired responses in a defined environment. METHODS: Silicone breast implant foils with different surface modifications were tested after 24 hours, 5 days and 7 days. The following modifications of silicone implant foils were tested: Unmodified silicone, silicone after-graft polymerisation for polyacrylic acid (pAAc), silicone-pAAc-fibronectin adsorptive, silicone-pAAC-fibronectin covalent, positive and negative controls. Experiments were conducted using cell culture with murine mouse fibroblasts L-929. Cytotoxicity assays were carried out in direct and indirect contact with cells grown on the material. For the viability test and qualitative analysis of cell proliferation on different foils, both fluoresceine-diacetate and ethidiumbromide were used and in addition the morphologic description of hemalaun-stained cells were used. Quantitative cell analysis was carried out using XTT after resuspension. RESULTS: Toxic influence on cell cultures could be excluded for coated and uncoated surfaces in contact with dissolved biomaterials. Unmodified silicone surfaces showed poor cell growth in direct contact. We found a gradual improvement of cell morphology, with the spread and proliferation depending on the type of surface modification. Better results were achieved with covalently coupled fibronectin and GRGDS than with pAAc. CONCLUSION: Covalent immobilisation of hydrophobic silicone rubber can improve the initial cell-biomaterial interactions that are required to aid the successful development of tissue-like structures.

Biocompatible Materials↗
PubMed2002

An interaction between dietary silicon and arginine affects immune function indicated by con-A-induced DNA synthesis of rat splenic T-lymphocytes.

Sporadic reports have appeared that suggest silicon plays a functional role in immune function by affecting lymphocyte proliferation. In addition, there is also considerable interest in supplemental arginine as a modulator of immune function. Therefore, the purpose of this animal experiment was to determine the effect of supplemental compared to adequate arginine on immune function as measured by splenic T-lymphocyte proliferation in the presence of adequate or inadequate dietary silicon. The independent variables were, per gram of fresh diet, silicon supplements of 0 or 35 microg and arginine supplements of 0 or 5 mg. The basal diet contained 2.3 microg silicon/g and 7.82 mg L-arginine/g. After feeding the male rats (nine per treatment group) for 8 wk, spleen lymphoid cells were isolated and cultured with methyl-3[H]thymidine. Supplemental arginine significantly decreased Con-A-induced DNA synthesis of splenic T-lymphocytes, but the response to arginine was influenced by dietary silicon. The decreased DNA synthesis was more marked when rats were fed adequate silicon than when fed inadequate silicon. Also, when arginine was not supplemented, DNA synthesis was higher in lymphocytes from rats fed an adequate silicon diet than rats fed the inadequate silicon diet. These findings support the huypothesis that an interaction between silicon and arginine affects immune function and that inadequate dietary silicon impairs splenic lymphocyte proliferation in response to an immune challenge.

Animal Feed↗
PubMed1994

Egress route of emulsified 20 centistokes silicone oil from anterior chamber of rabbit.

Silicone oil is used in recent clinical practice, however, it may cause adverse reactions in the eyes. When the high viscosity silicone oil is contaminated with low molecular weight silicone oil, the contamination may cause ocular toxicity or elevation of the intraocular pressure. To obtain information on the distribution of this preparation, emulsified 20 centistokes silicone oil was injected into the anterior chamber of rabbit eyes. The silicone oil droplets were visualized by light and electron microscopy by using oil soluble phthalocyanine blue. This copper containing dye remains in the tissue after removal of the silicone oil by organic solvents. Two and 4 weeks after an injection, the silicone emulsion was observed as numerous small vacuoles with blue precipitate at the margin of vacuoles within elongated trabecular endothelial cells, fibroblasts along the route of uveoscleral outflow and cells of the iris. Three hours after the injection, only a few vacuoles were present in these cells. These results demonstrated that the emulsified silicone oil leaves the anterior chamber through the conventional and unconventional routes. Phagocytosis by the trabecular endothelial cells and fibroblasts along the uveoscleral route caused an accumulation of the emulsified silicone oil in these cells. With chronic exposure to emulsified silicone oil, changes in the trabecular meshwork may lead to a reduction in the outflow of aqueous humor and cause glaucoma.

Animals↗
PubMed1993

The adjuvant effect of silicone-gel on antibody formation in rats.

The extent of immunological adjuvancy of silicone-gel, from mammary implants, up to now, has not been determined definitively. This study compares the immune potentiation effects of silicone-gel with that of Freund's adjuvant, using bovine serum albumin (BSA) as the test antigen in rats. Sixty, 250 gr., male Sprague Dawley rats were divided into six groups: I- phosphate buffered saline (PBS) only, II- silicone oil (Dow Corning Medical Grade 360 liquid silicone), III- 50% silicone-gel (McGhan Medical Corp.- mammary implant) in silicone oil, IV- complete Freund's adjuvant (CFA), V- incomplete Freund's adjuvant (IFA), and VI- 50% silicone oil in IFA. Each adjuvant was mixed or emulsified with an equal volume of 50 micrograms of BSA in 150 microliters of PBS. Each immunization was given intramuscularly in a single injection. Cardiac puncture test bleeds were taken at 12, 22, 40 and 56 days post immunization and the serum anti-BSA-antibody was measured by ELISA. The results indicate that silicone-gel is a potent immunological adjuvant, compared to both CFA and IFA. Silicone oil alone is not as potent as adjuvant and seems to inhibit the immune response when mixed with IFA. There thus appears to be a distinct possibility that silicone-gel may also be able to mediate an auto-immune reaction.

Animals↗