Feasibility of using experimental high viscosity silicone oils: a pilot study

BACKGROUND: Polydimethyl silicones (silicone oils) are used in complex retinal surgeries, including difficult or recurrent retinal detachments, severe eye trauma, and other indications for long term tamponade. Two major problems with currently available silicone oils are emulsification and recurrent retinal detachment. The primary endpoint of this study was to evaluate the toxicity and safety of high viscosity silicone oils and second, the feasibility of using them with currently available vitrectomy systems. METHODS: In this experimental study, 8 eyes of 8 New Zealand White rabbits underwent vitrectomy. The vitreous cavities of 2 eyes were filled with medical grade 5500 cS silicone oil, 4 eyes with 12,500 cS oil, and 2 eyes with 30,000 cS oil for 3 months, after which the animals were sacrificed and the eyes sent for histopathological examination. The duration required to inject 5 cc each of 1300, 12,500 and 30,000 cS oils, using a commercially available system (Alcon VFC Pac) were also evaluated. RESULTS: Retinal histopathology was comparable in all eyes, with no excess toxic effect or damage seen in eyes with experimental oils. All oils were readily injectable with the VFC Pac system. CONCLUSIONS: High viscosity experimental silicone oils have similar chemical and physical properties to lower viscosity oils currently used. Therefore, toxicities are expected to be similar. In a small pilot sample of 8 rabbit eyes filled with silicone oil for 3 months, histopathology in eyes with 12,500, 30,000 cS or medical grade 5500 cS silicone oil were similar. Injecting these oils using available vitrectomy equipment is feasible. New, high viscosity silicone oils may offer several advantages over currently available oils for some patients.