We have evaluated a video-based method for measuring binocular horizontal and vertical eye movements of human subjects by comparing it with the magnetic search coil technique. This video tracking system (VTS) uses multiple infrared light sources and small video cameras to simultaneously measure the positions of reflected corneal images and the center of the pupil. The system has a linear range of approximately ±40° horizontally and ±30° vertically, a sampling rate of 120 Hz (180 Hz with the head fixed), and system noise with standard deviation of < 0.04°. The binocular eye-tracking system is light-weight (190 g), being mounted on goggles that, with the eyes in primary position, permit a field of view of 60° horizontally and vertically. The VTS is insensitive to translations of the tracker relative to the eyes. By placing the video preprocessing unit on a cart, eye movements may be recorded while subjects walk through distances up to 100 feet. In comparison with the magnetic search coil technique, the VTS generally provides reliable measurements of horizontal and vertical eye position; eye velocity is noisier than corresponding coil signals, but superior to electro-oculography.
|Number of pages||6|
|Journal||Journal of Neuroscience Methods|
|State||Published - May 1995|
Bibliographical noteFunding Information:
Supported by USPHS grant EY06717, NASA grant NAG9-571, the Department of Veterans Affairs, and the Evenor Armington Fund (to R.J.L.). We are grateful to Dr. M. Eizenman of the El-Mar Corporation and University of Toronto for providing us with details of the EL-MAR tracking device, providing the data on the position noise, linearity, and translation insensitivity of the system, and for critically reading the manuscript. The authors have no commercial interest in the EL-MAR system.
- Eye movement
- Magnetic search coil