CIRCADIAN-RHYTHMS IN THE HUMAN PUPIL AND EYELID

The human eye was studied to investigate its use as a noninvasive mark er 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 an d palpebral fissure distances were estimated using a cosine curve-fitt ing technique applied to each 24-h data set. Pupil diameter acrophases occurred randomly throughout the day. The data demonstrated a signifi cant circadian rhythm for both resting and maximum palpebral fissure v alues. 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 sympatheti c innervation to the pineal is paralleled in the eye, and results do n ot demonstrate any applicability of human eye measurements as circadia n markers.