Abstract: Electrodes located at predetermined locations about a patient's eye sense electrical signals indicative of eye movement. The sensed signals are coupled to amplification circuitry operated from a battery power supply. The battery power supply and battery operated amplification circuitry have a floating common reference to reject electromagnetic interference. An optocoupler isolates the battery operated circuitry and the patient from non-battery operated circuitry which provides a signal representative of the sensed signal to drive a recording pen of a chart recorder. Corrective compensation responsive to variations in the sensed signal caused by electrode to skin surface contact changes and circuit changes maintains a zero central fixation reference potential.