Silicone oil insulation effects on flash electroretinogram and visual evoked potential in patients with retinal detachment / Efectos del aislamiento del aceite de silicona sobre el electrorretinograma flash y el potencial evocado visual en pacientes con desprendimiento de retina

Background: Silicone oil is used as endotamponade following vitreoretinal surgery to maintain the retina reattached when indicated. This study investigates the hypothesis that silicone oil causes insulation effects on the retina by affecting its response to light. Methods: Electrophysiological responses to a flash stimulus were recorded using full-field electroretinography (ERG) and visual evoked potentials (VEP). Recordings were performed in 9 patients who underwent surgery for retinal detachment, before (1–2 days) and after (2–3 weeks) silicone oil removal (SOR) in both the study and the control eye. Flash ERG and VEP recordings were performed according to the ISCEV standard protocol. Results: Statistically significant differences were found in the study eye in the amplitudes of the ERG responses and their corresponding ratios, i.e. the amplitude after SOR over the amplitude before SOR, in all conditions tested. No differences were observed in the control eye. The mean ratio of photopic ERG response was 3.4 ± 2.4 for the study and 1.0 ± 0.3 for the control eye (p<0.001). The mean ratio of ERG flicker response was 3.1 ± 2.4 and 1.0 ± 0.3, respectively (p = 0.003). Scotopic flash ERG ratio was 5.0 ± 4.4 for the study and 1.3 ± 0.6 for the control eye (p = 0.012). No differences were observed for the amplitude and latency of flash VEP response after SOR. Conclusions: Silicone oil causes a reduction in flash ERG responses; no effect was found on flash VEP responses. ERGs in eyes filled with silicone oil should not be considered representative of retinal functionality, in contrast to VEPs, which are not affected by silicone oil presence.(AU)

Comparison of clinical performance of obturating materials in pulpectomies: A randomized clinical trial.

BACKGROUND: Chemomechanical debridement is insufficient to disinfect all bacteria from the root canals of primary teeth, and obturation of canals with an appropriate material thus acquires excellent importance and remains a critical step in the ultimate success of pulpectomy. AIM: The aim of the study was to compare and evaluate Endoflas, Metapex, and a mixture of calcium hydroxide (CH) and zinc oxide (ZnO) as obturating materials (OMs) in primary mandibular second molars. MATERIALS AND METHODS: Seventy-five mandibular second primary molars requiring pulpectomies were identified in children aged 4-8 years. They were randomly allocated to the three treatment groups according to the type of OM received using the block randomization technique. After the completion of chemomechanical debridement, the canals were filled with Endoflas, Metapex, and CH-ZnO mixture, respectively. The intergroup clinical and radiographic comparison was made based on Coll and Sadrian criteria to decipher their clinical performance at 1, 3, and 6 months. RESULTS: No statistically significant differences between the groups were observed at any evaluation time interval (P > 0.05). At 6 months, the clinical success rates were 95.2% in Endoflas, 96% in Metapex, and 95.8% in the CH and ZnO mixture groups, respectively. The materials, however, behaved differently in different clinical situations. CONCLUSION: Based on the observations, all three OMs showed similar clinical success in maintaining tooth functioning, but their use can be restricted to indications. However, prospective studies with longer follow-ups with more stringent eligibility criteria are required to reach more definitive conclusions.

Impact of duration of silicone oil tamponade on foveal and parafoveal thickness in rhegmatogenous retinal detachment: a retrospective cohort study.

PURPOSE: To detect and analyze the influence of the duration of tamponade with silicone oil on the foveal and parafoveal thickness in cases of rhegmatogenous retinal detachment. METHODS: This is a retrospective cohort study of 64 eyes with rhegmatogenous retinal detachment in one eye who underwent pars plana vitrectomy (PPV) with silicone oil injection during the period between January 2019 and December 2021. The patients were divided into 2 groups. Group A with early removal of the silicone oil after 3-4 months and Group B with late removal of the silicone oil (SOR) after 6-8 months. The 2 groups were compared as regards the central foveal (CFT) and parafoveal (PFT) thickness changes from baseline, just before SOR, and after SOR. Changes in best corrected visual acuity (BCVA), relative risk of severe thinning. It was conducted at Kasr Alainy Hospital. RESULTS: 64 eyes were enrolled in the study. Group A included 36 eyes, and group B included 28 eyes. The mean CFT changed insignificantly from 253 ± 52 µm to 252 ± 48 µm after SOR in group A; while it changed significantly from 211 ± 52 µm to 202 ± 46 µm after SOR in group B. The mean PFT decreased insignificantly from 299 ± 39 µm to 297 ± 40 µm in group A, while it decreased significantly from 284 ± 46 µm to 273 ± 44 µm in group B. Lines of improvement of BCVA were 4.11 ± 1.88 in group A, and 2.00 ± 1.24 in group B. Relative risk of severe foveal thinning after SOR was 14.3, and severe parafoveal thinning was 15.43, in group B compared to group A. CONCLUSION: Longer period of silicone oil tamponade may carry a higher risk for severe foveal and parafoveal thinning after silicone oil removal. TRIAL REGISTRATION: The study was registered at clinical trial.gov under the title of (Duration of silicone oil tamponade on foveal and parafoveal thickness in Rhegmatogenous Retinal Detachment) with an ID NCT05817630 at April 2023 "retrospectively registered".

Contamination Profile of Different Formulations of Silicone Oil Tamponade Before and After Intraocular Permanence for Rhegmatogenous Retinal Detachment.

Purpose: The purpose of this study was to search for contaminants in silicone oil tamponades removed from eyes treated for retinal detachment, and to correlate chemical results with some clinical/functional parameters of the considered eyes. Methods: We examined a sequential cohort of eyes grouped according to the tamponade received: (1) Siluron2000 (S2), (2) RS-OIL ECS5000 (S5), and (3) Densiron Xtra (DX). Samples were collected at the beginning of the scheduled removal and analyzed by untargeted headspace gas-chromatography mass spectrometry (HS-GC-MS). Visual acuity and optic coherence tomography assessments were obtained before and after the tamponade removal. Results: Forty-one samples were analyzed: 22 belonging to the DX group, 13 to the S2 group, and 6 to the S5 group. For each group, a mixture of uninjected commercial preparation was analyzed as the reference. Different siloxanes and fluorinated compounds including perfluorodecalin (PFCL) were the most prevalent chemicals, found in 55% to 100% of the intraocular samples of the 3 groups. Some siloxanes were present also in the control matrices, whereas PFCL was only in the extracted tamponades. In the DX group, the concentration of hexamethylcyclotrisiloxane showed an inverse correlation trend with the duration of its permanence inside the eye (P = 0.054). Different alkanes, propanol, and acetaldehyde were identified only in the control matrices. Conclusions: Several contaminants including siloxanes were identified in the intraocular samples and in the control matrices. A time-related ocular uptake of some of these is conceivable. PFCL was also highly present but only in intraocular samples. Translational Relevance: After intraocular permanence silicone oils (SOs) have various unlabeled contaminants with some relevant differences with the commercial formulation chemical profile.

Effect of silicone oil versus gas tamponade on macular layer microstructure after pars plana vitrectomy for macula on rhegmatogenous retinal detachment.

PURPOSE: To analyze structural changes in the macular retinal layers and sub-foveal choroidal thickness (SFCT) in eyes after macula-on rhegmatogenous retinal detachment (RRD) repair by pars plana vitrectomy with either silicone oil (SO) or gas tamponade, and the effect of these changes on visual acuity. PATIENTS AND METHODS: Retrospective study which included 26 eyes in the SO Group and 32 in the Gas Group. Optical coherence tomography (OCT) scans of the affected eyes were obtained before surgery, and 3 months after PPV in the Gas Group, and during silicone oil in situ and 3 months after SO removal, in the SO Group. Qualitative assessment of photoreceptor layer and foveal contour, along with quantitative assessment of macular retinal thickness and SFCT was performed. Postoperative OCT macular microstructural changes were recorded and correlated to corrected distance visual acuity (CDVA). Intraocular pressure (IOP) was measured preoperative and at 3 months post operative. RESULTS: There was a 2-line loss (from 20/28 preoperatively to 20/40 at final follow-up) of CDVA in the SO Group (p=0.051), while there was no statistically significant change in CDVA in the Gas Group (p=0.786). There was no significant correlation between CDVA loss and duration of silicon tamponade (r=-0.031, p=0.893). There was a statistically significant increase in IOP from its baseline to final follow-up of 0.7 mmHg in the SO Group (p=0.023) while there was no statistically significant change in IOP in the Gas Group. During silicone oil tamponade, there was approximately 11% and 5% of retinal and sub-foveal choroidal thinning respectively, which was moderately resolved following silicone oil removal. 20% (5/24) of eyes in the SO Group had qualitative flattening of foveal contour during SO tamponade that resolved after SO removal. CONCLUSION: Thinning of the macula was noticed after macula-on RRD repair with SO tamponade. Such thinning was only partially reversible after the removal of SO.

Silicone-geranium essential oil blend for long-term antifouling coatings.

This study explores the potential of geranium essential oil as a natural solution for combating marine biofouling, addressing the environmental concerns associated with commercial antifouling coatings. Compounds with bactericidal activities were identified by 13Carbon nuclear magnetic resonance (13C NMR). Thermogravimetric analysis (TGA) revealed minimal impact on film thermal stability, maintaining suitability for antifouling applications. The addition of essential oil induced changes in the morphology of the film and Fourier transform infrared spectroscopy (FTIR) analysis indicated that oil remained within the film. Optical microscopy showed an increase in coating porosity after immersion in a marine environment. A total of 18 bacterial colonies were isolated, with Psychrobacter adeliensis and Shewanella algidipiscicola being the predominant biofilm-forming species. The geranium essential oil-based coating demonstrated the ability to reduce the formation of Psychrobacter adeliensis biofilms and effectively inhibit macrofouling adhesion for a duration of 11 months.

Friction Dynamics of Human Skin Treated with Oil under Nonlinear Motion.

Moisturization causes physiological changes that improve the barrier function of human skin and mechanical changes, including skin friction characteristics. This study evaluated petrolatum- or silicone oil-treated human skin to determine the effect of moisturizing on the friction dynamics. The friction force on the human skin was measured using a contact probe with a sinusoidal motion. The contact probe was used to rub the skin of the upper arm of 20 subjects. The water content of the stratum corneum, softness, and barrier function of the skin were measured using a corneometer, cutometer, and tewameter, respectively. Both oils reduce the frictional force on the human skin. Simultaneously, silicone oil also reduced the delay time δ, which is the standardized time difference between the frictional force response to contact probe movement. Three typical friction patterns were also discovered, which were significantly changed by the treatment with oil. These changes were attributed to the lubrication effect and elimination of adhesion at the true contact point between the skin and the contact probe.

Functional and perfusion changes associated with silicone oil tamponade after macula-off rhegmatogenous retinal detachment surgery: an optical coherence tomography angiography/microperimetry study.

PURPOSE: The current study utilizes microperimetry and optical coherence tomography angiography (OCTA) to assess the optic nerve head vasculature, retinal microvasculature, and retinal sensitivity before and after silicone oil (SO) removal. METHODS: This prospective observational case series study involved 30 eyes subjected to silicone oil endotamponade. Microperimetry and OCTA were utilized to assess the vascular density (VD) of the macula and optic nerve head, as well as the retinal sensitivity (RS), of the participants preoperatively and 1 month following SO removal. The correlation between the various parameters of OCTA and microperimetry was evaluated. RESULTS: There was a significant improvement in the postoperative best-corrected visual acuity (BCVA) (p-value < 0.001) and the postoperative total RS, which was 6.38 ± 2.34 dB as compared to a mean preoperative total RS of 5.04 ± 2.06 dB (p-value < 0.001) and showing a significant increase in all rings. However, there was no significant difference in the pre and postoperative macular VD. On the other hand, there was a significant increase in the postoperative VD of the whole disk and the peripapillary capillary plexus, p-values < 0.001 and 0.002, respectively. CONCLUSION: The removal of SO resulted in significant improvements in retinal sensitivity, vision, and optic nerve perfusion. However, no significant change was observed in macular VD. CLINICAL TRIALS: gov Identifier: NCT04928196.

On recycling earth pressure balance shield muck with residual foaming agent: defoaming and antifoaming investigations.

Earth pressure balance (EPB) shield is increasingly employed in metro tunnel construction, and causes a series of environmental, safety, and resource waste problems due to the disposal of a considerable amount of muck. In situ recycling of EPB shield muck is an effective solution, whereas the foam is generated by residual foaming agents used as the muck conditioning material during tunnelling, which often adsorbs clay particles and overflows the flocculation tank. To achieve defoaming and antifoaming during the reuse of muck, this study prepared novel eco-friendly silicone oil-polyether defoamers by condensation, compounding, and shear emulsification. Defoaming and antifoaming performances of different defoamers were tested using a modified Ross-Miles method and a scale model of field flocculation systems. The results indicated that a high efficiency in defoam and antifoam was characterized by chemical grafting of nano-SiO2 from silicone oils, uniform distribution and large size of grains, low viscosity, and surface tension. The defoamer dosage of 0.002-0.004 wt% near critical micelle concentration (CMC) for each defoamer is reasonable. Overall, the prepared hydroxyl silicone oil-glycerol polyoxypropylene ether (H-G) defoamer compared with other silicone oil-polyether defoamers and commercial defoamers presents the highest defoaming and antifoaming efficiency. Considering the effects of EPB shield muck, the H-G defoamer is least affected by the compound materials and increasing concentration of the commercial foaming agent. Nevertheless, the stability of the H-G emulsion system is weaker than that of the dimethyl silicone oil-glycerol polyoxypropylene ether (D-G) emulsion system after 1 month of sealed storage.

Incidental Finding of Suprachoroidal Space's Silicone Oil Migration: A Tumor-Mimicking Lesion and Its Clinical Management.

The migration of silicone oil into the suprachoroidal region is a rare complication of vitrectomy. A 70-year-old man was admitted to our ocular oncology unit with a choroidal elevation in the nasal area, as well as signs of pars plana vitrectomy surgery performed about 5 years ago for retinal detachment. The patient underwent ocular ultrasound, visual field test, fluorangiography, and magnetic resonance imaging, which led to the diagnosis of silicone oil migration in the suprachoroidal space. Silicone oil may move into the suprachoroidal area, mimicking choroidal neoformation. It is important to have a comprehensive diagnosis and then set up the appropriate treatment. [Ophthalmic Surg Lasers Imaging Retina 2024;55:104-108.].

Evaluating Clinical Safety and Analytical Impact of Subvisible Silicone Oil Particles in Biopharmaceutical Products.

Silicone oil is a commonly used lubricant in pre-filled syringes (PFSs) and can migrate over time into solution in the form of silicone oil particles (SiOPs). The presence of these SiOPs can result in elevated subvisible particle counts in PFS drug products compared to other drug presentations such as vials or cartridges. Their presence in products presents analytical challenges as they complicate quantitation and characterization of other types of subvisible particles in solution. Previous studies have suggested that they can potentially act as adjuvant resulting in potential safety risks for patients. In this paper we present several analytical case studies describing the impact of the presence of SiOPs in biotherapeutics on the analysis of the drug as well as clinical case studies examining the effect of SiOPs on patient safety. The analytical case studies demonstrate that orthogonal techniques, especially flow imaging, can help differentiate SiOPs from other types of particulate matter. The clinical case studies showed no difference in the observed patient safety profile across multiple drugs, patient populations, and routes of administration, indicating that the presence of SiOPs does not impact patient safety.

Inferior implant of XEN63 Gel stent in a refractory open-angle glaucoma due to silicone oil tamponade: A case report.

BACKGROUND: To discuss the efficacy of an inferior implant of XEN 63 gel stent in a patient with refractory glaucoma after trabeculectomy failure and vitreoretinal surgery with silicone oil tamponade. CASE DESCRIPTION: We report the case of a 73-year-old man with a history of refractory open glaucoma with trabeculectomy failure. He experienced recurrent retinal detachments with silicone oil tamponade, with uncontrolled intra-ocular pressure (IOP) after silicone oil removal. Due to the presence of oil emulsion in the anterior chamber, the chosen location for XEN 63 implantation was the infero-temporal quadrant. Mild hyphema and vitreous hemorrhage were seen post-operatively, but were self-limiting. At week 1, the intraocular pressure was 8 mmHg with a well-formed bleb seen in anterior segment optical coherence tomography (AS-OCT). At 6 month follow up, the patient maintained a IOP of 12 mmHg without topical hypotensive drugs. Slit lamp examination revealed a widespread, developed bleb with no signs of inflammation. CONCLUSION: In this case of refractory glaucoma in a vitrectomized eye with previous oil tamponade, the inferior placement of the XEN 63 gel stent delivered an adequate intraocular pressure even at 6-months follow up, with a diffuse functional infero-nasal bleb seen with AS-OCT.

Aqueous misdirection syndrome post silicone oil removal in a vitrectomized eye - a case report.

PUROPSE: Aqueous misdirection syndrome (AMS) is an aggressive post-operative glaucoma unresponsive to conventional measures with grave outcomes. In this report, we describe a rare case of AMS following silicon oil removal in a vitrectomized eye. METHODS: A diabetic patient with tractional retinal detachment underwent pars plana vitrectomy with silicon oil injection. Following retinal reattachment, silicon oil removal was performed at three months. Post oil removal she developed increased intraocular pressure with shallowing of both the peripheral and central anterior chamber suggestive of AMS. RESULTS: Initial medical management with anti-glaucoma medications and cycloplegics was not beneficial. A pars plana lensectomy with complete anterior hyaloidectomy along with a surgical peripheral iridectomy helped relieve the aqueous misdirection. CONCLUSION: AMS can rarely occur following vitrectomy and is likely secondary to intact anterior hyaloid. Lensectomy along with zonulo-hyaloido-iridectomy is essential. This report highlights the occurrence of this rare complication and its effective management.

Characterization of Silicone from Closed System Transfer Devices and its Migration into Pharmaceutical Drug Products.

Closed System Transfer Devices (CSTDs) are increasingly used in healthcare settings to facilitate compounding of hazardous drugs but increasingly also therapeutic proteins. However, their use may significantly impact the quality of the sterile product. For example, contamination of the product solution may occur by leaching of silicone or particulates from the CSTDs. It was therefore the aim of the present study to identify and quantify the types of silicone oil in a panel of typically used CSTDs. Particles found after simulated CSTD compounding processes were evaluated using Light Obscuration and Micro-Flow Imaging and were confirmed to be silicone oil particles. The number of particulates shed from CTSDs was in single cases exceeding pharmacopeial limits for a final parenteral product. Using X-ray microtomography, lubrication was shown to be primarily applied at connecting parts of the CSTD. Quantitative and qualitative analysis by Fourier transform infrared spectroscopy (FTIR) revealed a total released amount between 0.8 and 16 mg per CSTD of polydimethylsiloxane or polymethyltrifluoropropylsiloxane per CSTD. While pronounced differences in total silicone content between CSTDs were observed, it did not fully correlate with particle contamination in the test solutions, potentially due to variations in CSTD design. The impact of typical surfactants in biological formulations on silicone migration into product was additionally evaluated. We conclude that CSTDs may compromise final product quality, as (different types of) silicone oil may be released from these devices and contaminate the administered product.

Comparative Study of Sorption Phenomena Between Three Medications and Syringes Made of Cyclic Olefin Copolymer or Polypropylene.

INTRODUCTION: Medical syringes are widely used in hospitals to store and administer drugs, and the contact time between the drugs and these syringes can vary from a few minutes to several weeks like for pharmaceutical preparations. The aim of this comparative study was to evaluate the potential sorption phenomena occurring between three drugs (paracetamol, diazepam and insulin aspart) and polypropylene syringes (PP) or syringes made of Cyclic Olefin Copolymer (COC). MATERIALS AND METHODS: 50 mL 3-part syringes made of either COC with crosslinked silicone on the barrel inner surface (COC-CLS) and a bromobutyl plunger seal, or PP lubricated with silicone oil (PP-SOL) with a polyisoprene plunger seal were used. RESULTS: COC-CLS syringes induced less sorption of diazepam and insulin than PP-SOL syringes and the plunger seal material seemed to be the main cause of these interactions. An alkalinization of the medications in contact with the PP-SOL syringes was observed. It could be caused by leachable compounds and should be investigated further. CONCLUSION: This work shows once again that it is essential to consider content-container interactions to help improve the safe use of parenteral drugs.

Long-term complications according to silicone oil type. A single center cohort study.

PURPOSE: To study the incidence of macular edema (ME), ocular hypertension (OHT), emulsification and migration to the anterior chamber (AC) of silicone oil (SO) in patients after complex retina surgery, stratified by SO type. METHODS: Retrospective, cohort study. Patients who underwent retina surgery with SO injection and extraction in our center were included. We compared the complication rates of ME, OHT, emulsification and migration to the AS according to SO type (1300cSt, 5700cSt and heavy SO). Data on age, sex, emulsification time, duration of the tamponade, previous retina surgeries and diagnosis were also gathered and included in a multivariate analysis. RESULTS: We included 163 patients (mean age of 64.8 years; mean duration of the tamponade: 11 months). Rates of emulsification, ME, OHT and SO migration to the AC were similar in all groups (p = 0.998, 0.668, 0.915 and 0.360). ME was the most frequent complication (33.3-47.8%), which resolved after SO extraction in 77.6% of cases. The majority of cases with OHT persisted (61.7%). Emulsification was related to younger age (OR 0.94) and longer duration of the tamponade (OR 1.04). The odds of SO migration to the AC increased with emulsification (OR 2.78), recurrent retinal detachment (OR 0.99) and aphakia (OR 4.05). CONCLUSIONS: We propose SO extraction as the preferred treatment for ME during SO tamponade. SO extraction should be performed sooner in younger patients to avoid emulsification. In selected patients, we suggest a longer duration of the tamponade up to 11 months with a reasonable safety profile, regardless of the SO type.

Silicone oil tamponade induced vasculitis- a rare manifestation of toxic posterior segment syndrome.

AIM: To report silicone oil tamponade induced vasculitis in the early post operative period - a rare manifestation of 'Toxic Posterior Segment Syndrome' after pars plana vitrectomy for rhegmatogenous retinal detachment. CASE DESCRIPTION: A 50-year-old gentleman presented with vasculitis after a pars plana vitrectomy with silicone oil tamponade on the first post-operative day. He was started on oral steroids (1 mg/ kg) tapered sequentially every week. All signs of vasculitis resolved over a period of one month after which the silicone oil was removed. The patient maintained a visual acuity of 20/90 even after 3 months. There was no recurrence of vasculitis observed thereafter. CONCLUSION: Silicone oil induced vasculitis is a rarely described entity, especially as a manifestation of toxic posterior segment syndrome. This differential must be kept in mind even on the first post-operative day in cases where silicone oil has been used for tamponade.