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Zengping Liu, Xinyi Su, Sing Shy Liow, Mein Jin Tan, Zibiao Li, Xian Jun Loh, Caroline Chee, Gopal Lingam; Intraocular biocompatibility evaluation of thermogelling as a vitreous tamponade agent in rabbits. Invest. Ophthalmol. Vis. Sci. 2018;59(9):5923.
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© ARVO (1962-2015); The Authors (2016-present)
Endo-tamponade agents are crucial surgical adjuncts for vitreo-retinal surgery. We described an optimized thermogelling polymer as tamponade, and evaluated its intraocular biocompatibility in vitrectomised eyes of rabbits.
A thermogel consisting of the copolymers of poly(ethylene glycol), poly(propylene glycol), and poly(ε-caprolactone) segments linked together via urethane bonds (named as EPC). Sol-gel transition properties were characterized by rheological analysis. All animal treatments were approved by IACUC of SingHealth, Singapore, and in accordance with the ARVO Statement for the Use of Animals in Ophthalmic and Vision Research. Twenty-three male New Zealand White rabbits weighting 2.5-3kg were used in this study. Three-port, 23G core vitrectomy was performed under a surgical microscope. Posterior vitreous detachment (PVD) was performed with triamcelanone assistance. 15 eyes were injected with sol-state EPC thermogel formulated at 3 different viscosities, e.g. EPC-3%, 7% and 12%. 20% Pluronics F127 hydrogel and irrigation media (balanced salt solution, BSS) were used as controls. The rabbits were followed by slit-lamp, SD-OCT, full field ERG up to 3 months.
The storage and loss moduli showed EPC gel could be injected whilst in sol-state at 4 °C, and rapidly form a gel in-situ within the vitreous cavity at 37 °C. At 7-day post-operation, rabbits implanted with Pluronic F127-20% exhibited sub-retinal fluid accumulation on SD-OCT images. By 2 to 4-week post-operation, rabbits implanted with EPC-12% hydrogel, developed severe sub-acute inflammation associated with elevated intraocular pressure. In EPC-3% filled eyes, we noticed significant retinal thinning and atrophy on both SD-OCT live-imaging and ex-vivo H&E histology, which related to 38.3% reduction in scotopic a-wave and 25.2% reduction in photopic a-wave on ERG at 3 months. On the contrary, EPC-7% filled eyes demonstrated superior long-term biocompatibility, with clear corneas, absence of cataract, normal intraocular pressures, normal retinal thickness and architecture as determined by both SD-OCT and histology, with no significant inflammatory stress in the retina and normal retina function on ERG.
We propose that EPC-7% thermogel can be easily handled and used by the ophthalmic surgeon, and it will radically transform clinical practice of vitreo-retinal surgery as a promising endo-tamponade agent.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
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