[Real-time measurement of torsional eye movements by video-based technique]

The authors developed a real-time measurement system to analyze torsional eye movements using video-based technique with two small dots on a soft contact lens as the targets. The lens, saturated with physiological saline solution, was made to adhere to the eye by dropping distilled water on it, according to Edelman's method. It was demonstrated that the clear image of the lens marker was sufficient to extract torsional eye information without using complex image processing technique and that the lens attached firmly to the eye during recordings. An engineering work station (Hewlett Packard Inc, HP9000/350) was used for hardware implementation, which required only 15 milliseconds to process one frame of a video image and the torsional angle was able to record and display in real-time rate. The accuracy (precision error) of this measurement, evaluated by simultaneous recordings with dyed dots on the conjunctiva and an error propagation analysis, was better than delta = 0.08 degrees.