[How good is spatial orientation with rigid endoscopic optics? Study of micromanipulation in the nasal cavity]

Rigid endoscopes are used as an alternative to the operating microscope for visual control during paranasal sinus surgery. Since the view through the endoscope is monocular, perception of depth (stereopsis) through the operating microscope must be expected to be superior due to the binocular view afforded. To investigate whether monocular visualization through an endoscope is a disadvantage in paranasal sinus surgery, we compared stereoacuity in a model of the nasal cavity, using a head lamp, an operating microscope and a 0 degree Hopkin's endoscope. Twenty volunteers had to touch defined points in a spatial model of the nasal cavity. Under binocular vision with a head lamp, performance was significantly better than with the microscope or the endoscope. Manipulations were performed with the same speed under microscopic and endoscopic control, although under microscopic guidance more faults in point sequence were made than with the endoscope. Various monocular phenomena seem to allow sufficient spatial orientation through the endoscope, so that monocular visualization does not appear to be a disadvantage for quick and safe manipulations during functional endoscopic sinus surgery.