Two mechanisms of vergence eye-movement and accommodation in human eyes are connected to each other constructing a control system which is called the accommodation-vergence eye-movement control system. The response of this controll system was measured when a subject watched a moving target displayed on a stereoscope. The relation between vergence and accommodation in this case is different from that measured when a subject watches a real three-dimensional object. However it is infered that

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... exists substantially no difference between the characteristics of the control system in these two cases. Then we concluded that the characteristics of the connecting mechanism between vergence and accommodation did not change according to the characteristics of inputs. And we proposed a fundamental linear model of the accommodationvergence eye-movement control system. Changes of the characteristics of the control system with time in stereoscopic vision were measured, and their relation to asthenopia was discussed.