In vivo retinal tolerance of various heavy silicone oils

Heavy silicone oils are currently under investigation as a permanent tamponade in eyes with inferior PVR. This study was an investigation of Densiron 68 (Fluoron GmbH, Neu-Ulm, Germany) and several new heavy silicone oil admixtures on the basis of the perfluoroalkanes F4H5 (perfluorobutylpentane), F4H6 (perfluorobutylhexane), and F4H8 (perfluorobutyloctane) with respect to their long-term tolerance in a rabbit model.

Because of the better solubility of the F4Hn-species (n = 5-8) in comparison to F6H8, we used F4H5, F4H6, and F4H8 to generate highly viscous, heavy silicone oils (HSO). After vitrectomy and fluid-air exchange, the left eye of each of five rabbits per group was filled with HSO 68-1500 (Densiron 68), HSO 45-5000, HSO 45-3000, HSO 46-5000, HSO 46-3000, HSO 48-5000, or HSO 48-3000, or pure F4H5, F4H6, or F4H8. Detailed clinical investigation, ERG testing, and histologic evaluation were performed throughout a 3-month follow-up.

Densiron 68 and HSOs based on F4H5, as well as the three control oils (silicone oil of 1000, 3000, and 5000 mPa . s) were well tolerated over 3 months. Histologically, the retina was unaffected. In contrast, intraocular inflammation, cataract formation, and retinal detachment and degeneration were noticed in all groups with HSOs based on F4H6 or F4H8.

Biocompatibility of the new HSOs is dependent on the lipophilic behavior (R(F)/R(H) ratio) and furthermore on the molecular dimension of the used semifluorinated alkanes (SFAs). HSOs on the basis of F4H5 may have advantages over silicone oils, on the basis of F6H8, for use as a tamponade agent for the inferior retina in difficult retinal situations.