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S.M. Warden, J.B. Christoforidis, D.J. D'Amico; Successful Redirection of Retinal Blood Flow in vivo Following Vascular Cannulation in Rabbits . Invest. Ophthalmol. Vis. Sci. 2005;46(13):4053.
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Purpose: Microvessel manipulation is one application in the emerging field of retinal vascular surgery that could offer new therapies for patients with retinal vascular disease. In vivo studies thus far have largely focused on vessel cannulation and injection of vasoactive substances. However, there have been no studies that clearly illustrate controlled and redirected blood flow from a retinal vessel lumen. In the present study, rabbit retinal vessels were cannulated with borosilicate glass microtips resulting in controlled blood flow through the microcannula. Methods: Rabbits were anesthetized with xylazine and ketamine. A sectoral peritomy and sclerotomy 1 mm superotemporal to the limbus were performed. A trochar was placed in the sclerotomy site allowing for easy access of the microtip into the vitreous cavity. Eppendorf borosilicate glass microtips were designed to have external diameters of 10–20 microns and a beveled and angled end with a heat formed spike. These microtips were inserted into the vitreous while visualizing the rabbit retinal vessels with an operating microscope and direct contact lens. Results: Retinal vessels approximately 30–60 microns in size were cannulated, and controlled flow of blood through the microcannula was demonstrated with minimal or no vitreous hemorrhage. Blood flow could be augmented with the use of negative pressure across a 3–cc syringe connected to the microcannula with polyamide tubing. Veins were easier to cannulate than arteries, which were smaller and more difficult to puncture because of their thickened walls. Conclusions: This study demonstrated that partial diversion of blood flow from a native vessel lumen could be successfully accomplished by means of retinal vessel cannulation. Shunting of venous blood away from a central or branch retinal vein occlusion, or bypass of arterial blood around a thrombus are more advanced retinal vascular procedures that may be feasible in the future. Certain obstacles, such as maintaining patency of the bypass tract and inserting the distal end of the tract into another vessel lumen, need to be overcome.
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