Mechanical energy from intraocular instruments cause emulsification of silicone oil.
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AIM: The complications of intraocular silicone oil include emulsification, which may lead to vision-threatening disorders such as keratopathy, secondary glaucoma and retinopathy. The authors study the effect of mechanical energy from surgical instruments on the emulsification of silicone oil. METHODS: Three different handpieces (phacofragmentation, phacoemulsification, high-speed vitrectomy) were placed at the interface of balanced salt solution and silicone oil (1000 and 5000 cst, 200 fluid; Dow Corning). The phacofragmentation handpiece was evaluated over different ultrasound powers and duration. Emulsification was quantified with phase-contrast microscopy and manual counting of digital photographs by a masked examiner. In addition, phacoemulsification was performed in the anterior chamber of a human ex vivo eye with full-fill silicone oil. RESULTS: Emulsification increases with higher phacofragmentation power and duration and is greater for 1000 cst silicone oil. Emulsification of silicone oil occurs with phacoemulsification and high-speed vitrectomy handpieces. CONCLUSIONS: The energy from surgical handpieces is sufficient to result in silicone oil emulsification. (+info)
Results of high-density silicone oil as a tamponade agent in macular hole retinal detachment in patients with high myopia.
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BACKGROUND: To evaluate the use of high-density silicone oil (HDSO) as a tamponade agent for retinal detachment secondary to myopic macular hole. METHODS: 12 eyes of 12 patients with macular hole retinal detachment underwent pars plana vitrectomy, internal limiting membrane peeling and HDSO tamponade. No posturing was required postoperatively and HDSO was removed 3-4 months later. Outcome measures included macular hole closure and retinal attachment rates, best-corrected visual acuity (BCVA), and intraoperative and postoperative complications. RESULTS: The mean age of the patients was 67.8 years and the mean spherical equivalent refractive error was -13.4 diopters. After the removal of HDSO, 10 (83%) eyes had macular hole closure with retinal reattachment without any tamponade. One eye had retinal reattachment after re-operation and the other refused further surgery. At the last follow-up, the median BCVA improved from 20/800 to 20/600 (p = 0.046). A transient increase in intraocular pressure was observed in 5 (42%) eyes and one eye each developed mild oil emulsification and transient peripheral choroidal detachment. None of the eyes was found to have severe intraocular inflammation postoperatively. CONCLUSIONS: HDSO seemed to be an effective tamponade agent for myopic macular hole retinal detachment. Further prospective controlled studies seem warranted. (+info)
Changes in spherical aberration after lens refilling with a silicone oil.
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PURPOSE: It may be possible to restore accommodation to presbyopic human eyes by refilling the lens capsular bag with a soft polymer. In the present study, optical changes were measured that occurred in a pig eye model after the refilling of the capsular bag. METHODS: The optical power and spherical aberration in 10 isolated pig lenses were measured under different conditions. They were first determined by using a scanning laser ray-tracing technique over an effective pupil size of 6 mm. Second, the contours of the anterior and posterior lens surface were photographed, and a mathematical ray-tracing was performed by using a polynomial fit through the digitized surface contours, to determine optical power and spherical aberration. Third, the lenses were refilled with a silicone oil until their preoperative lens thickness was reached, and scanning laser ray-tracing, contour photography, and mathematical ray-tracing were repeated. Comparisons between the measurements were made to determine how the change from a gradient refractive index to a homogeneous refractive index influenced spherical aberration. The influence of the change in lens contour on spherical aberration after lens refilling was also studied. RESULTS: The natural lenses had a higher lens power than the refilled lenses (49.9 +/- 1.5 D vs. 36.8 +/- 1.5 D; P < 0.001). Moreover, there was a change in sign from negative spherical aberration before lens refilling (-3.6 D) to positive spherical aberration after lens refilling (7.9 D; P < 0.001). The comparison between scanning laser ray-tracing of the natural lens and mathematical ray-tracing of the photographed surface contours of the natural lens to determine the effect of refractive index substitution (i.e., replacement of a gradient refractive index by a homogeneous refractive index) showed a significant change in spherical aberration from -3.6 +/- 2.0 to 11.0 +/- 2.1 D (P < 0.001). The change in lens contour did not result in a significant change in spherical aberration (P = 0.08) before and after lens refilling with an equal refractive index. CONCLUSIONS: The lower lens power of refilled pig lenses compared to natural lenses was due to the lower refractive index of the refill material. Refilling pig lenses with the silicone oil used in this study resulted in an increase in spherical aberration. This increase was mainly caused by the change from a gradient refractive index to a homogeneous refractive index. The change in lens curvature after lens refilling did not result in an increase in spherical aberration. The influence of lens refilling on spherical aberration of human lenses must be determined in similar experiments in human eyes. (+info)
In vivo retinal tolerance of various heavy silicone oils.
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PURPOSE: Heavy silicone oils are currently under investigation as a permanent tamponade in eyes with inferior PVR. This study was an investigation of Densiron 68 (Fluoron GmbH, Neu-Ulm, Germany) and several new heavy silicone oil admixtures on the basis of the perfluoroalkanes F4H5 (perfluorobutylpentane), F4H6 (perfluorobutylhexane), and F4H8 (perfluorobutyloctane) with respect to their long-term tolerance in a rabbit model. METHODS: Because of the better solubility of the F4Hn-species (n = 5-8) in comparison to F6H8, we used F4H5, F4H6, and F4H8 to generate highly viscous, heavy silicone oils (HSO). After vitrectomy and fluid-air exchange, the left eye of each of five rabbits per group was filled with HSO 68-1500 (Densiron 68), HSO 45-5000, HSO 45-3000, HSO 46-5000, HSO 46-3000, HSO 48-5000, or HSO 48-3000, or pure F4H5, F4H6, or F4H8. Detailed clinical investigation, ERG testing, and histologic evaluation were performed throughout a 3-month follow-up. RESULTS: Densiron 68 and HSOs based on F4H5, as well as the three control oils (silicone oil of 1000, 3000, and 5000 mPa . s) were well tolerated over 3 months. Histologically, the retina was unaffected. In contrast, intraocular inflammation, cataract formation, and retinal detachment and degeneration were noticed in all groups with HSOs based on F4H6 or F4H8. CONCLUSIONS: Biocompatibility of the new HSOs is dependent on the lipophilic behavior (R(F)/R(H) ratio) and furthermore on the molecular dimension of the used semifluorinated alkanes (SFAs). HSOs on the basis of F4H5 may have advantages over silicone oils, on the basis of F6H8, for use as a tamponade agent for the inferior retina in difficult retinal situations. (+info)
Nuclear magnetic resonance analysis of emulsified silicone oil RMN-3 (Oxane HD).
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BACKGROUND: Oxane HD is a mixture of 5700 cs silicone oil and RMN-3 (a partly fluorinated olefin), which has a specific gravity greater than water, thereby enabling endotamponade of inferior retinal breaks. Droplets of emulsified oil were found in the anterior chamber of two patients with complex retinal detachments who had been treated with Oxane HD. Samples removed from these two eyes were analysed in order to investigate the nature of the emulsified substance. METHODS: Samples were dissolved in CDCl3 and, if necessary, dried using magnesium sulphate. Nuclear magnetic resonance (NMR) was used to compare these samples with the unused commercial product. RESULTS: NMR analysis of the samples removed from the anterior segment of both eyes were mainly silicone oil with only trace amounts of RMN-3. Samples taken from different areas of an unused syringe of Oxane HD demonstrated varying concentrations of the RMN-3 compound within the silicone oil. CONCLUSION: First, the mixture of RMN-3 and silicone oil is not homogenous either in vitro or in vivo. Second, emulsified oil found in the anterior chamber is composed almost entirely of silicone oil, containing only trace amounts of RMN-3. (+info)
Is silicone oil optic neuropathy caused by high intraocular pressure alone? A semi-biological model.
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BACKGROUND: Silicone oil endotamponade is used for the repair of complicated retinal detachments. Cataract, glaucoma and corneal endothelial dysfunction are the most frequent complications of silicone oil tamponade. Clinical and histopathological studies have revealed that silicone oil can penetrate into the optic nerve and into the brain. The mechanism by which silicone oil moves from intraocular into the optic nerve is still under debate. To investigate the effect of intraocular pressure only, a post-mortem experimental histological study was performed to determine whether silicone oil penetration from the globe into the optic nerve after vitrectomy and silicone oil instillation is a purely pressure-related phenomenon. Although a post-mortem study excludes physiological processes, it serves as a model for the study of pure physical forces onto biological structures. METHODS: The study was carried out on 20 human eyes with their optic nerves attached. All specimens had been harvested from patients without known eye disease. The vitreous body was removed with a syringe and the globe was filled with silicone oil. A lipophil fluorescence marker (Bodipy) was added in 8 eyes. The mean intraocular pressure after silicone oil filling measured 40 mm Hg and the globes stayed under pressure for up to 16 weeks. The eyes and optic nerves were stained with H&E and examined with light, phase-contrast and fluorescence microscopy. RESULTS: None of the 20 specimens examined showed silicone oil in the retrolaminar portion of the optic nerve. CONCLUSIONS: Migration of silicone oil into the optic nerve was not demonstrated in this human post-mortem study. Therefore other factors, such as pre-existing glaucomatous damage to the disc region and/or active transport mechanisms must be involved in the development of silicone oil-associated optic neuropathy. (+info)
Retreatment of full-thickness macular hole: predictive value of optical coherence tomography.
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AIM: To determine whether the efficacy of re-operation for idiopathic full-thickness macular hole (FTMH) remaining open after initial surgery with internal limiting membrane (ILM) peeling is correlated with macular hole configuration as determined by optical coherence tomography (OCT), macular hole size, macular hole duration before the first operation, or type of tamponade (gas or silicone oil). METHODS: A retrospective consecutive interventional case series of 28 patients (28 eyes) with a persisting macular hole after vitrectomy, ILM peel, and gas tamponade. 28 patients underwent repeat surgery involving vitrectomy and gas (n = 15) or silicone oil tamponade (n = 12) or no tamponade (n = 1). Autologous platelet concentrate (n = 22), autologous whole blood (n = 1), or no adjuvant (n = 5) was used. Preoperative OCT was undertaken in all eyes. The main outcome measures were anatomical closure and improvement of best-corrected visual acuity (BCVA). RESULTS: Anatomical closure was achieved in 19 of 28 eyes (68%). BCVA improved in 12 eyes, remained unchanged in nine, and worsened in seven. BCVA improved in 11 of 19 eyes with anatomical closure, and in one of eight eyes without closure. Anatomical closure and improvement of BCVA correlated with preoperative macular hole configuration on OCT, with higher rates of closure (18 of 20 eyes versus one of eight eyes, p = 0.001) and greater improvement of BCVA (p = 0.048) in eyes with a cuff of subretinal fluid at the break margin. Macular hole size, type of tamponade, macular hole duration before the first operation, or preoperative BCVA did not significantly correlate with visual or anatomical outcome. CONCLUSION: Macular hole configuration seems to be a strong prognostic indicator of anatomical closure and may help identify those patients most likely to benefit from re-operation. (+info)
Vitrectomy for circumscribed choroidal hemangioma with exudative retinal detachment refractory to transpupillary thermotherapy.
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We report successful surgical management of a circumscribed choroidal hemangioma with exudative retinal detachment refractory to transpupillary thermotherapy (TTT). A 33-year-old man with symptomatic serous macular detachment in the left eye (Snellen acuity: 20/200) secondary to a paramacular choroidal hemangioma was treated with TTT. The nonresponsive detachment was subsequently managed by vitrectomy, endophotocoagulation and silicon-oil tamponade. It resulted in complete resolution of the tumor and the detachment. Silicon oil was removed at four months. Visual acuity improved to 20/80 by the last follow-up visit at 10 months without any recurrence. (+info)