Tamponade properties of double-filling with perfluorohexyloctane and silicone oil in a model eye chamber

Background. The use of perfluorohexyloctane as a heavier-than-water tamponade for long-term use is limited by its tendency to dispersion and associated intraocular inflammation. Double-filling with silicone oil and F6H8 produces a united, two-layer bubble, appearing as a single bubble. This has been proposed as a method of improving the utility of F6H8 as a tamponade. Methods. A surface modified polymethylmethacrylate model eye chamber was double-filled with perfluorohexyloctane and silicone oil to approximate a 90% fill. The proportion of silicone oil was increased in a stepwise fashion. A qualitative comparison of surface contact at each stage was made. Chambers with one, two or no indent were used. Dispersion by agitation of the chamber was assessed. Results. With less than 20% silicone oil it was difficult to force the two liquids to make contact. With more oil they united in the form of a single bubble joined at an interface. Once joined, the sides of the single bubble were drawn away from the wall of the chamber. As the proportion of silicone oil increased the area of lost contact increased and progressed inferiorly. Compared to F6H8 alone the double-fill reduced dispersion. Conclusion. Silicone oil and F6H8 can unite to form a single bubble that changes the effectiveness of either tamponade agent on their own. The double-fill needs to have enough silicone oil to form a single bubble, but this needs to be kept as low as possible to avoid progressive loss of lateral tamponade. It does not provide good simultaneous superior and inferior tamponade. The double-fill reduces dispersion.