Benchmarking different brands of perfluorocarbon liquids.

PURPOSE: To compare the analytical quality characteristics of currently available CE-marked perfluorocarbon liquids (PFCL) applied intraoperatively during vitreoretinal surgery. METHODS: Twenty-one samples of 8 brands of perfluorooctane (PFO) and 25 samples of 13 brands of perfluorodecalin (PFD) were analysed. Gas chromatography coupled with mass spectroscopy (GC/MS) was used to determine the content of the main product. The amount of reactive and underfluorinated impurities was analysed and expressed as an H-value using fluoride selective potentiometry after a chemical transformation reaction to detect impurities that triggered both acute and latent toxic effects. UV-active substances were determined in order to draw conclusions on the integrity of primary packaging components. Moreover, we controlled for any 1H-PFO contamination in PFO, as it is known to modify PFO's surface characteristics. RESULTS: Significant differences in the tested products' purity profiles were detected. The PFO batches revealed H-values ranging from < 10 to 1230 ppm and 1H-PFO concentrations ranging from < 1 to 376 ppm. Leachable substances from packaging components cause UV absorption in the 0.1 to > 3 AU range. The PFD batches revealed H-values ranging from < 10 to 70 ppm and leachables from packaging components resulting in absorbances in the 0 AU to 3.2 AU range. CONCLUSION: The quality characteristics of the analysed PFCL vary significantly, not only among different brands but among batches from the same manufacturer as well. Manufacturers should communicate the purity of their products in an understandable and clear manner. This would require providing a complete certificate of analysis focussing especially on quality characteristics to enable vitreoretinal surgeons to differentiate between the effects from the PFCL itself and those from impurities.

Benchmarking different brands of silicone oils.

PURPOSE: To compare the analytical quality characteristics of currently available CE-marked silicone oils used as ocular endotamponades in vitreoretinal surgery. METHODS: Thirty-four samples of 12 brands were analysed. To assess the quality characteristics of silicone oils, we measured the oligosiloxane content and polydispersity, widely accepted as purity parameters. UV-active substances (> 220 nm) were analysed to draw conclusions about the integrity of primary packaging components. RESULTS: We identified significant differences in the impurity profiles of the products tested, which revealed oligosiloxane contents ranging from < 0.1 to 491 ppm, polydispersity ranging from 1.6 to 3.0 and UV-active substances (> 220 nm) ranging from 0.2 to 3.8 AU. CONCLUSION: The quality characteristics of the analysed silicone oils vary significantly not only among different brands but also among batches of the same manufacturer. Manufacturers should communicate the purity and quality characteristics of their products in an understandable and clear manner. This involves providing a complete certificate of analysis with special focus on quality characteristics, to enable the vitreoretinal surgeon to differentiate between the effects of the silicone oil itself and those of impurities.

The phenomenon of "sticky" silicone oil.

BACKGROUND: To investigate the reasons for difficulties removing silicone oil from the vitreous cavity due to putative adherence to the retina. METHODS: Gas chromatography-coupled mass spectroscopy of the headspace (GC/MS/HS) and gel permeation chromatography (GPC) were used to detect volatile compounds in silicone oil samples explanted from patients, qualitatively as well as quantitatively. Surface and interfacial tensions of the explanted samples were measured using the pendent-drop technique. To simulate the removal of silicone oil from the vitreous cavity, the contact between silicone oil and differently treated surfaces and various aspiration techniques were tested in vitro. RESULTS: The median concentration of perfluorodecalin in seven "sticky" samples was 2.4 times higher than in 14 non-sticky samples. In the sticky samples, the median surface tension of the aqueous phase was lower. The difficulty of aspirating silicone oil could be reproduced in vitro by reducing the surface tension of the aqueous environment of the silicone oil. CONCLUSION: The observed stickiness of silicone oil seems to be a matter of reduced surface tension of the surrounding aqueous material and/or contamination of silicone oil with perfluorocarbon liquid, which creates interruption of the material flow, giving the impression of adherence of the silicone oil to the retina.

Interaction of different ocular endotamponades as a risk factor for silicone oil emulsification.

PURPOSE: To investigate the influence of other substances used intraoperatively in vitreoretinal surgery on the emulsification of silicone oil in patients' eyes. METHODS: Gas chromatography coupled mass spectroscopy of the headspace (GC/MS/HS) was used to detect volatile compounds in silicone oil samples explanted from patients qualitatively as well as quantitatively. Surface and interfacial tensions of the explanted samples were measured using the pendent drop technique. RESULTS: Some samples of nonemulsified explanted silicone oil were not different in their content of volatile substances measured by GC-MS/HS. In all explanted samples of emulsified silicone oil volatile substances could be detected, which do not exist or are at the detection limit in native silicone oil for ophthalmic use. The majority of contaminants are heavy liquids, cleaning substances, and oligosiloxanes. CONCLUSION: The contact of silicone oil with all types of substances should be reduced to a minimum. Reuse of tubing sets must be avoided. If a direct exchange between heavy liquids and silicone oil seems necessary, turbulence at the interfaces must be avoided and the contact time between these two endotamponades must be kept as short as possible. If these precautions are obeyed, the risk of emulsification of silicone oil used as an ocular endotamponade can be significantly reduced, down to the influence of individual patients' conditions.

Preparation and processing of vitreoretinal instrumentation and equipment as a risk factor for silicone oil emulsification.

PURPOSE: To investigate possible sources for the induction of silicone oil emulsification in patients' eyes. METHODS: The contaminants on a ready-to-use standard set of vitreoretinal instruments cleaned and sterilized in an eye clinic were determined. The determination of detergents was carried out according to a standardized procedure, which uses ultrapurified water to rinse the equipment in question, followed by a measurement of the conductivity. Silicone oil remnants were determined using Fourier transformed infrared spectroscopy. RESULTS: Ionic components of detergents and remnants of silicone oil could be detected on instrumentation deemed sterile, clean, and ready-to-use. CONCLUSION: During routine cleaning and sterilization of vitreoretinal instruments and accessories, remnants of silicone oil and detergents can persist and trigger emulsification of silicone oil, which came into contact with these contaminated devices during instillation of the endotamponade.