Humans have experienced motion sickness and possessed the knowledge of stereopsis since classical antiquity. Knowledge of stereopsis dates back to approximately 300 B.C., when Euclid first recognized the concept of depth perception in human vision. Further, the motion sickness is including a sensation of wooziness and nausea that has been documented since approximately 400 B.C., when it was mentioned in the Aphorisms of Hippocrates. Stereoscopic images that utilize binocular stereopsis can frequently cause viewers to experience unpleasant symptoms including visual fatigue. Despite the increased use of three-dimensional (3D) display technologies and numerous studies on 3D vision, there is insufficient accumulation of researches to clarify the effects of 3D images on the human body. Therefore, the safety of viewing virtual 3D images is an important social issue. Inconsistency between convergence and lens accommodation is suspected as a cause of which motion sickness induced by stereoscopic viewing have not yet been identified. A system to simultaneously measure the convergence and lens accommodation is constructed to characterize the 3D vision. Fixation distances were compared between the convergence and lens accommodation while a subject repeatedly viewed 3D video clips. The results indicated that the accommodative power did not correspond to the distance of convergence after 90 s of continuously viewing 3D images. Presently, the relationship between this inconsistency and the unpleasant symptoms remains unclear. Therefore, we introduce empirical research on the motion sickness that can contribute to developments in the relevant fields of science and technology.