97th DOG Annual Meeting 1999

K407

VIRTUAL VITRECTOMY COMPUTER SIMULATION OF AN INTRAOCULAR EYE SURGERY

C. Wagner1, M. Schill1, M. Hennen1, B. Jendritza2, M. C. Knorz2, H.-J. Bender3

We present a computer-based medical training workstation for the simulation of a vitrectomy. The project aims to improve training and rehearsal of eye surgeons. The surgeon manipulates two original instruments inside a mechanical model of the eye. The instrument positions are tracked by ccd cameras and monitored by a PC which then renders the scenery using a computer graphical model of the eye and the instruments. Stereoscopic images are presented to the user through two small lcd displays that are mounted to the system and emulate the stereo microscope used in real operations. The simulator offers the training of intra-ocular navigation as well as first approaches to interaction with pathological tissues (e.g. membrane peeling in diabetic retinopathy).

The simulator incorporates a model of the operation table, a mechanical eye, three ccd cameras for the position tracking, the stereo display and a computer. Like the real eye in its orbital cavity the mechanical eye provides three rotational degrees of freedom. The functionality of the eye muscles is modeled with springs. The three cameras are mounted under the operation table. With a mirror their field of view is redirected onto the mechanical eye. Instruments and mechanical eye are marked with small light sources. Using the stereoscopic back projection with the images from two of the three cameras the positions of the instruments and the orientation of the mechanical eye in space is determined. The third ccd device is used to enhance the accuracy of the tracking.

We use an off-the-shelf PC for the calculations. It computes the tissue reaction, the computer graphical model of the scenery and the stereoscopic back projection. The simulation runs at 15 to 20 frames per second and provides a realistic impression of the surgery. It includes the cold light source which can be moved inside the eye and the shadow of the vitrector on the retina which is important for navigational purposes.

1 Lehrstuhl für Informatik V, Universität Mannheim, B6 26, D-68131 Mannheim,
2 Universitäts-Augenklinik, Klinikum Mannheim gGmbH, D-68135 Mannheim,
3 Institut für Anästhesiologie, Klinikum Mannheim gGmbH, D-68135 Mannheim


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