Study on the safety of internal tamponades by magnetic resonance imaging, electroretinography and histology in animal model

Abstract

PURPOSE: Silicone oil is often used as a tamponade agent in surgical treatment of severe rhegmatogenous retinal detachment with proliferative vitreoretinopathy in order to stabilize and provide long-term support for the retina. This study aimed to investigate the longitudinal safety of two kinds of silicone oil: Siluron 2000 (density=0.97) and Densiron 68 (density=1.06) as well as their effects on retinal function using MRI scan, electroretinography (ERG), and histological assessment. METHODS: Ex-vivo: Pig eye model with MRI imaging is used. Freshly harvested pig eyes were filled with silicone oil during the 3-port pas plana vitrectomy (PPV). Immediately after the procedure, 7T T2W MRI imaging was conducted. In-vivo: rabbit model was used for longitudinal study. 3-month old female New Zealand white rabbits underwent 3-port PPV on the right eye with silicone oils filled. 3T T2W MRI imaging and ERG measurement were performed at 1 week and 3 months after PPV. Flash ERG using Ganzfeld system and contact-lens electrode was performed after dark adaptation for 20 minutes, with the forehead as reference and the contralateral ear as ground. Animals were sacrificed 3 months after PPV and their eyes were enucleated for histology after removal of the silicone oil.. Serial sections were stained with hematoxylin and eosin. RESULTS: The MRI scan of pig eyes and post-surgery rabbit eyes showed clear silicone oil bubbles surrounded by an aqueous environment. The a-wave, b-wave and implicit time of ERG signals showed no significant difference between the silicone oil-filled eyes and the control eyes for both Siluron 5000 and Densiron 68. Histology data indicated no significant reduction of retinal ganglion cell number for both silicone oils. CONCLUSIONS: The high-resolution MRI is proved to be a convenient method to reveal the post-operative therapeutic effect of intraocular tamponade agent on retinal re-attachment. Both ERG and histology data indicated good safety and efficacy of both Siluron 2000 and Densiron 68 in our rabbit model.