Ergonomics of surgical microscopes for the sitting position as determined by ocular-corpus length

BACKGROUND: The sitting position is favorable for microsurgical procedures applied to posterior midline pathologies in both the supra- and infratentorial regions. The dimensions of the microscope corpus affect the device’s comfort and handling in the hands of the microneurosurgeon for such procedures. A shorter microscope corpus provides more favorable intraoperative ergonomics for surgical practice. METHODS: Evaluation of the most comfortable microscope for its application in microsurgical procedures in the sitting position as determined by ocular-corpus length. RESULTS: Six modern surgical microscopes were tested and evaluated regarding their ocular-corpus lengths and working distances: the Mitaka MM90, Zeiss Kinevo 900, Zeiss Pentero 900, Leica M530, Zeiss Neuro NC4, and Möller-Wedel Hi-R 1000. The ocular-corpus lengths vary between 270 and 380 mm. The Mitaka MM90 microscope has the shortest ocular-corpus length at 270 mm. CONCLUSION: The ocular-corpus length determines the predominant part of the lever arm, which affects the fatigue of the surgeon. By virtue of its short ocular-corpus length, the Mitaka MM90 is currently the most favorable microscope for microsurgical procedures using a sitting position.