Background: Extracranial-intracranial bypass is a challenging procedure that requires special microsurgical skills and an operative microscope. The exoscope is a tool for neurosurgical visualization that provides view on a heads-up display similar to an endoscope, but positioned external to the operating field, like a microscope. The authors carried out a proof-of-concept study evaluating the feasibility and effectiveness of performing microvascular bypass using various new exoscopic tools. Methods: We evaluated microsurgical procedures using a three-dimensional (3D) endoscope, hands-free robotic automated positioning two-dimensional (2D) exoscope, and an ocular-free 3D exoscope, including surgical gauze knot tying, surgical glove cutting, placental vessel anastomoses, and rat vessel anastomoses. Image quality, effectiveness, and feasibility of each technique were compared among different visualization tools and to a standard operative microscope. Results: 3D endoscopy produced relatively unsatisfactory resolution imaging. It was shown to be sufficient for knot tying and anastomosis of a placental artery, but was not suitable for anastomosis in rats. The 2D exoscope provided higher resolution imaging, but was not adequate for all maneuvers because of lack of depth perception. The 3D exoscope was shown to be functional to complete all maneuvers because of its depth perception and higher resolution. Conclusion: Depth perception and high resolution at highest magnification are required for microvascular bypass procedures. Execution of standard microanastomosis techniques was unsuccessful using 2D imaging modalities because of depth-perception-related constraints. Microvascular anastomosis is feasible under 3D exoscopic visualization; however, at highest magnification, the depth perception is inferior to that provided by a standard operative microscope, which impedes the procedure
