Is monocular perception of depth through the rigid endoscope a disadvantage compared to binocular vision through the operating microscope in paranasal sinus surgery?

Vision through the endoscope is strictly monocular. Perception of depth (stereopsis) during ethmoid surgery through the operating microscope would be expected to be superior due to binocular view. To investigate whether monocularity of the endoscope is a disadvantage in paranasal sinus surgery, we compared stereoacuity in a model of the nasal cavity using a headlamp, an operating microscope, and a 0 degree-Hopkins-endoscope. Twenty volunteers were asked to touch defined points in a spatial model of the nasal cavity. Due to the configuration of the model, which allowed binocular vision of all contact points with headlamp, performance was significantly better than with optical instruments. Manipulations were performed faster with the endoscope than with the microscope. Under microscopic guidance more faults in point sequence were made than with the endoscope. Various monocular phenomena obviously allow sufficient spatial orientation through the endoscope, so that monocularity of the endoscope appears not to be a disadvantage for quick and safe manipulations during functional endoscopic sinus surgery.