Dynamic accommodation revealed by three dimensional optometer and its control center in a brain

Three dimensional optometer (TDO) can measure dynamic accommodation, eye movement and pupil diameter simultaneously, while subjects are looking at visual objects by moving their eyes. While three-dimensional visual stimulator (TVS) can present independent binocular targets changing its distance, direction and image size. Using the TDO and the TVS, simultaneous accommodation and vergence responses toward a real image and/or a stereoscopic image created by the TVS were measured. It was found that the accommodation toward the stereoscopic image showed peculiar responses that had less amplitude compared with the response toward the real image, and recede movement of accommodation from the initial peak in the response. A 64-channel whole-cortex magnetoencephalography (MEG) system was also used to study the control mechanism of the accommodation by the central nervous system. A special relay lens system has been developed both to impose visual stimuli and to measure accommodation responses with a dynamic refractometer. Using these systems, MEG and accommodation responses were measured simultaneously. Consequently, an accommodation response toward stepwise stimuli was found after about 300 ms from the onset of the stimuli. Two highly synchronized MEG responses probably related to the accommodative control were found at about 100, 200 ms from the onset of the stimuli prior to the accommodative response.