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KYLE PACKER, Sien Chen, Larry Andreo, Jake Lowry, Steve Zumbrun; Novel Anterior Chamber Tube Shunt with Tissue Autograft. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):2706.
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© ARVO (1962-2015); The Authors (2016-present)
To construct an anterior chamber tube shunt with saphenous vein autografts and compare functional outcomes with those of Ahmed valve implants.
Twelve adult male New Zealand White rabbits were divided into two cohorts of six rabbits in this study, the first arm includes autograft vs the control fellow eye. We harvested saphenous venous grafts to serve as a functional reservoir in a tube shunt system. The venous graft was secured to an Ahmed model TE tube extender and implanted beneath the conjunctiva following the standard method aqueous drainage device insertion. The second arm includes Ahmed model FP8 valves vs the control fellow eye. The rabbits were housed in an IACUC approved facility for 60 days postoperatively and received a standard medication regimen. 30 minutes prior to sacrifice, the rabbits were sedated and 1cc of cationic ferritin tracer was injected in the operated eye via intracameral method. The operated eye was enucleated and half of the graft site was excised and flash frozen in liquid nitrogen for ELISA analysis. The remainder of the graft site was tagged with a 6.0 nylon suture and placed in formalin fixative for 24h prior to pathologic sectioning.
We assayed four main outcome measures. (1) Intraocular pressure on operated eye vs. the control fellow eye. (2) Patency of tube shunt apparatus at 2 months evaluated histologically with cationic ferritin tracer and Prussian Blue stain. (3) Histologic evidence of inflammation and fibrosis in and around the apparatus at 2 months with H&E stain. (4) Immunologic assay for TNF alpha in the draining aqueous humor. Initial results on six rabbits with Ahmed implants and four rabbits with autografts demonstrate a stastically significant difference in intraocular pressure among control, Ahmed, and autograft eyes. Histologic samples are in process. Initial ELISA of aqueous humor TNFalpha measurements shows a stastically significant difference between control and Ahmed eyes and between control and autograft eyes. One autograft rabbit has not completed the protocol at submission date.
Study is ongoing, however our hypothesis is that inflammation and fibrosis will be decreased in this design compared to standard designs as the immune system will recognize the graft as ‘self’ and not as a foreign body. With decreased fibrosis, the flow of aqueous humor can be maintained providing an improved functional outcome compared to standard surgical therapy.
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