Bypassing Occluded Retinal Main Vessel Segments in Isolated Arterially Perfused Caprine Eyes

Purpose: To investigate the feasibility of bypassing occluded segments of retinal arterial and venous main vessels in isolated, arterially perfused caprine eyes. Materials and Methods: Eyecups of isolated caprine eyes were used. From each, the ophthalmic artery was separated and cannulated. Krebs solution was then perfused into the retinal vessel to displace blood via the ophthalmic artery. All microvascular manipulations were performed via an open-sky approach under an operating microscope. A retinal main vessel was blocked by vascular ligation at the site just in advance of the vessel's first branching. Two openings, several millimeters apart, were created by means of vascular punctures into both the main vessel and the branch wall straddling the occlusive site. Catheterization was achieved using a flexible polyimide tube, with each end inserted into the vessel wall opening. A sealed connection between the vessel and tube was obtained by vascular ligation with sutures. Bypassing of the occluded segment of the retinal vessel was thus achieved, and the patency of the vascular bypass confirmed by intravascular staining. Results: Maneuvering of the retinal vascular bypass was accomplished using a combination of vascular puncturing, catheterization, and ligation. Good results were obtained in 18 of 25 (72%) caprine eyes. Conclusions: The feasibility of bypassing an occluded segment of a retinal main vessel was successfully demonstrated in isolated arterially perfused caprine eyes. These in vitro findings may be used as a reference for future experiments in the living eye.