A flying-spot laser scanner for tracking eye movements

A novel system has been developed to provide noninvasive and simultaneous measures of horizontal, vertical, and torsional (rotation about the visual axis) movements of the eye. It uses a flying-spot laser scanner to selectively image landmarks on the eye. A horizontal scan through the centre of the pupil locates the left and right edges of the pupil allowing horizontal eye position to be estimated. Similarly, vertical eye position is estimated from a vertical scan through the pupil. A circular scan records striations on the iris from which torsional movement can be estimated from cross-correlation of successive circular scans. The instrument can measure eye movements with a bandwidth of 25 Hz through a range of movement in excess of ±40° horizontally and ±30° vertically. Preliminary trials have demonstrated the feasibility of using a flying spot scanner to track eye movements. It should prove a valuable tool for the investigation of eye movements in neurological disorders