Background:

“Conventional” silicone oil floats upwards in the vitreous cavity. This results in a good tamponade of the upper retina, but leaves the lower retina without an effective tamponade. On the contrary, heavy silicone oil sinks and provides less effective support of the upper retina. In order to support both upper and lower retina double tamponade with perfluorocarbon liquid (PFCL) and silicone oil is used. There is a concern about safety of double tamponade based on the PFCL and silicon oil possible interaction.

Purpose:

To detect physical and chemical interaction of perfluorodecalin and silicon oil, to examine physical properties of silicon oil after the interaction with PFD.

Material & methods:

PFD and silicon oil were mixed together: 6 test tubes were filled with PFD and silicone oil of 1000 centipoise viscosity and 6 test tubes were filled with PFD and silicone oil of 5000 centipoise viscosity. Test tubes were put in thermostat with 36.6 °C and kept for 2, 3 and 4 weeks. After that both PFD and silicon oil from the tubes were studied with nuclear magnetic resonance (NMR) spectroscopy employing spectroscope Varian Inova 500W. NMR spectra 19F, 13C and 1H were analyzed. Viscosimetry of silicon oil from the tubes was performed employing falling-ball method.

Results:

19F, 13C and 1H spectra of all the samples showed no new spikes meaning no new chemical substances were detected in the mixtures. According to 13C spectrum, PFD dissolves in silicon oil gradually, the longer PFD contacts with silicon oil the higher its concentration in the silicon oil. After 4 weeks of contact the silicon oil contains about 1% of PFD. Silicon oil becomes less viscous and heavier-than-water substance. Silicone oil does not dissolve in PFD.

Conclusion:

PFD and silicon oil interact with each other physically but not chemically. Thus safety of double tamponade is not compromised by their interaction. The removal of double tamponade is easy because of silicone oil viscosity decrease. After 4 weeks of double tamponade silicon oil becomes heavier-than-water substance and stops supporting the upper retina.