Power spectra for ocular drift and tremor.

Eye position during fixation has been measured without contact and the power spectrum of drift and tremor eye movements has been estimated. In the 0-40 Hz frequency range power declines with frequency roughly as 1/f2. In the 40-100 Hz frequency range the dominant spectral component is a broad spectral peak with a peak amplitude of about 6 arc sec. The shape of the broad spectral peak is dependent on the fixation direction. A model that explains qualitatively the shape of the power spectra function is presented. It is suggested that tremor eye movements are by-products of the clock-like firing of motor neurons.