A new, heavier-than-water silicone oil:: a solution of perfluorohexyloctane in polydimethylsiloxane

PURPOSE. To prepare and explore new solutions of semifluorinated alkane in silicone oil, which have a specific gravity slightly higher than silicone oil and vitreous fluid (referred to in the following as heavier-than-water silicone oils (HWSs), and to investigate, in vitro, whether HWSs can be used to plug retina holes, while allowing dehydration of the subretinal space. METHODS. HWS solutions were prepared with silicone oil 5000 and perfluorohexyloctane (F6H8). The stability was investigated under different conditions. The viscosity was determined by means of a capillary viscometer. The surface and interface tension were measured using the ring method. RESULTS. HWSs are insoluble in an aqueous medium. Densiron (R) 68 (HWS 1.06) is a transparent homogeneous liquid which is slightly heavier (1.06 g/cm(3)) than water and has a refractive index close to that of vitreous liquid. Densiron 68 (HWS 1.06) has a low viscosity (1480 mPas) and interface tension (40.82 mN/m), making it an effective tamponade in the surgical treatment of an inferior detached retina. In addition, the interfaces between Densiron 68 and other perfluorocarbon liquids are clearly visible. However, the interface layer between Densiron 68 and water is not clear. Finally, all HWSs are stable over the long term at ambient temperatures, as well as physically and thermally resistant. CONCLUSIONS. Due to its physiochemical properties, Densiron (R) 68 could meet the requirements for a heavier-than-water tamponade.