Spontaneous fluctuations in pupil size are not triggered by lens accommodation

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.