The effect of stimulus size on human cyclofusional response

Abstract

Objective measurement of human cyclofusional response was carried out using a binocular eye movement monitoring device and a wide angle (50° field of view) tachistoscope. We studied the effect of stimulus size on the central and motor components of cyclofusional response. The results show a slight increase of cyclofusional thresholds corresponding to an increase in stimulus size from 10° to 50°. The torsional disparity contained in the 50° stimulus evoked substantial cyclovergent eye movements and the response also contained a significant central (non-motor) component. Reducing the stimulus size from 50° to 10° diminishes the magnitude of the motor response to a 5° torsional disparity. The data thus show the importance of wide field stimulation for evoking a significant motor component in cyclofusional response.