In vivo redirection of retinal blood flow into borosilicate micro-cannulas in rabbits

Background: Microvascular manipulation is one application in the emerging field of retinal vascular surgery that could lead to new therapeutic approaches for retinal disease. Research in this field has largely focused on vessel cannulation and injection of vasoactive substances. This study expands on applications for retinal vessel manipulation by demonstrating that redirection of retinal blood flow in vivo can be achieved through retinal vessel cannulation in a rabbit model. Methods: Dutch-belted rabbits were anesthetized, and a sectoral peritomy and sclerotomy 1 mm from the superotemporal limbus were performed. Borosilicate glass microtips with external diameters of 10-20 μm were introduced into the vitreous through the sclerotomy site. Using an operating microscope and a direct contact lens for visualization, we cannulated the rabbits' retinal vessels, and blood flow was redirected through the microtips. Results: Retinal vessels approximately 30-60 μm in size were cannulated, and controlled blood flow through the microcannula was demonstrated with minimal or no vitreous hemorrhage. Though still achievable, flow after arterial cannulation was more difficult to demonstrate. Conclusions: This study demonstrates that partial diversion of blood flow from a native vessel lumen could be successfully accomplished by retinal vessel cannulation. This early work indicates that more advanced retinal vascular procedures, such as vessel bypass around a thrombus or shunting blood towards an area of ischemic retina, may be feasible in the future.