Sensing Hand Tremor in a Vitreoretinal Microsurgical Instrument

An instrument for intraoperative sensing of surgeons’ hand tremor during vitreoretina l microsurgery has been developed. Real-time monitoring of tremor is useful to surgeons for purposes of training, adjustment of technique, monitoring of fatigue, and deciding when or whether to perform certain procedures. The instrument incorporates six inertial sensors (three accelerometers and three rate gyros), mounted at the back end of the handle, to detect translation and rotation in six degrees of freedom. The accelerometer data are integrated to obtain translational velocity, and the gyro data are integrated to determine the time-varying rotation matrix needed to transform the instrument motion to a fixed frame of reference. Instrument tip velocity in three dimensions is computed using this information. The displacement amplitude of the tremor is then approximated analytically from the velocity data, approximating it as a sinusoid. Four preliminary tests are presented: 1-dof translation (no rotation); 1-dof translation with amplitude modulation; 3-dof translation (no rotation); 6-dof motion (translation and rotation). The instrument presently estimates oscillations at physiological tremor frequencies with less than 7% error. Funding is provided by the Johnson & Johnson Focused Giving Program. The authors are grateful to Mr. Peter Berkelman and Dr. Ralph Hollis for the use of the Magnetic Levitation Haptic Interface. Copyright © 1999 Cameron N. Riviere