[Accommodative resting position and the effect of viewing distance on after-effects of accommodation and the pupil]

The resting position of accommodation is determined by the equilibrium established between sympathetic and parasympathetic tone. To accommodate for near objects is brought about by excitation of the parasympathetic, and distant objects call for excitation of the sympathetic system. To investigate accommodation and pupil after-effects following the 10 min visual task with stereoscopic three dimensional image, the measurements of the dynamic responses of accommodation and pupil were made. When the subjects worked at 0.4 m (closer than their resting state) and at 1 m corresponded to their resting positions, the response delay in accommodative relaxation occurred in each condition. When they worked at outside their resting position (1.5 m and 3 m viewing distances), the significant response delay in contraction in the groups of 1.5 m and 3 m, and the increases of accommodation error and the area of miosis were shown. There was a fact that the after-effect on accommodation and pupillary function was different between in the case of tasks given inside and outside their resting positions.