Fluctuations in pupil size and lens accommodation are measured concurrently
under open loop conditions, constant illumination and far fixation. In 12/
17 trials no correlation was measured between the fluctuations in pupil siz
e and lens accommodation. For the remaining 5/17 trials no lag was observed
between the changes in pupil size and lens accommodation indicating that t
his correlation does not arise as a consequence of a near response. These o
bservations suggest that under conditions of constant illumination and far
fixation, the supranuclear centers controlling the near response are not ac
tive. (C) 2000 Elsevier Science Ltd. All rights reserved.