Optically-navigable operating microscope for image-guided surgery.

In computer-assisted surgery (CAS), optical digitizing is state-of-the-art. Unfortunately standard navigation instruments, e.g. small, LED-equipped pointers are frequently shadowed by the operating microscope when the camera-array is ceiling- or rack-mounted. Thus, for microsurgery, a navigation module consisting of a reference panel mounted onto the housing of the microscope and an object distance measuring unit attached in front of the objective lens was developed. By means of this navigation module the microscope can be located in space with an accuracy of +/- 1-2 mm. Focusing errors due to the high depth of view of modern microscopes and individual refraction anomalies are eliminated by laser distance measurement. This device has been clinically tested since September 1994 and a typical case is reported.