AJP - Regulatory, Integrative and Comparative Physiology, Vol 271, Issue 2 320-R324, Copyright © 1996 by American Physiological Society
Circadian rhythms in the human pupil and eyelid
R. T. Loving, D. F. Kripke and L. K. Glazner
Department of Psychiatry, University of California, San Diego 92093, USA.
The human eye was studied to investigate its use as a noninvasive marker of
circadian phase state. Subjects were measured every 30 min over 24 h to
observe bilateral changes in pupil size and palpebral fissure. Twelve males
and twelve females (ages 18-29 yr, mean = 21.6 yr) were studied around the
clock while they remained within a light-controlled facility (< 100
lux). The acrophases (maximums) for pupil diameters and palpebral fissure
distances were estimated using a cosine curve-fitting technique applied to
each 24-h data set. Pupil diameter acrophases occurred randomly throughout
the day. The data demonstrated a significant circadian rhythm for both
resting and maximum palpebral fissure values. However, palpebral fissure
acrophases were widely distributed, with the largest portion of the peaks
occurring between 10:00 A.M. and 10:00 P.M.. These data did not support the
hypotheses that sympathetic innervation to the pineal is paralleled in the
eye, and results do not demonstrate any applicability of human eye
measurements as circadian markers.
