ABSTRACT
This chapter focuses on small eye-movements that remain during a fixation. It is not easy to make an analogue apparatus that produces a Fourier transform of records that contain many sharp movements as the eye-movement records do. Findlay devised an ingenious method of obtaining a power-spectrum corresponding to the saccadic movements and a power-spectrum corresponding to other movements. Findlay's results suggest that the drifts and tremor constitute a single noise-like disturbance of visual axis. Thomas and co-workers have recorded the variation of velocity of eye-movements with time. They used tranducer systems that differ materially from those used by other workers and found a kind of tremor that has not been reported by others. They have also measured the response of eyeball system when driven by sinusoidal forces and find a reasonance at 37 Hz with a bandwidth of 40 Hz in velocity response. Shaknovich found that this tremor is markedly different in patients suffering from certain kinds of brain tumors.
