97th DOG Annual Meeting 1999



G. Richard *, R.-R. Grigat **, K. Wiehler **

Microsurgery enables a precise morphological treatment of the ocular structures. However, the 5- to 20- fold magnification results in a reduction of the microscopic field causing a hitherto unsolved problem: Deliberate or involuntary motions of the patient result in a microscopic field that is not centered. Hence, the field of vision can not be used optimally and the illumination and the quality of the image are impaired. This is troublesome also for experienced surgeons. To solve this problem, the University Eye Clinic Hamburg developed in co-operation with the Technical University Hamburg-Harburg and industrial companies a tracking system for the operating microscope.

The computer-assisted tracking of the microscope requires several steps:

1. The video image data in real time are determined from the video image signal of the camera using a framegrabber card.
2. By Hough transformation, the center of the iris in the video image is established.
3. It is of special importance to estimate the accuracy of the data and to suppress faulty results.
4. When the center of the iris has been determined correctly, the data of its position are transferred to a computer which directs the motors of the microscope and tracks the microscope.

This technique has proven a great success although it demands to be accustomed to it. Especially patients operated on under local anaesthesia benefit from it. The increased safety of surgical interventions, which can be achieved using the new system, favours their successful outcome.

* Universitäts-Augenklinik Hamburg-Eppendorf, Martinistr. 52, D-20246 Hamburg, Germany
** Technische Universität Hamburg-Harburg, Abt. Technische Informatik, Harburger Schloßstr. 20, D-21079 Hamburg, Germany