Dynamic measures of vergence accommodation.

Dynamic measures of vergence accommodation (VG-ACC) are necessary for complete analysis of the triadic near response but are difficult to obtain because eyeball rotation affects accommodative measures. A dynamic optometer that uses the third Purkinje image is shown to be insensitive to small eye rotations and permits dynamic measures of VG-ACC responses. Such measures are presented to demonstrate the feasibility of this method. Average latency measures of 260 msec for VG-ACC fall between the latency of 160 msec for disparity vergence and the latency of 380 msec for accommodation. Additional dynamic features of VG-ACC resemble those of other components of the near triad.