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D. Ma, W. Lui, S.-Y. Li, A. C. Y. Lo, D. Wong, K. C. Chan, E. X. Wu, K. K. W. Li, The University of Hong Kong 3T MRI unit; Study on the Safety of Internal Tamponades by Magnetic Resonance Imaging, Electroretinography and Histology Techniques in Animal Models. Invest. Ophthalmol. Vis. Sci. 2009;50(13):3185.
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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.
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.
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.
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.
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