The pupillary light reflex cannot be used to measure sleepiness.

The pupillary light reflex (PLR) has been considered by some researchers to be responsive to changes in levels of sleepiness. However, no previous studies have tested this hypothesis with the dramatic variation of sleepiness across a complete circadian cycle. In this experiment, 20 normal individuals (age: 18-48 years) underwent a 27-hr constant routine, during which they were kept awake except for a 15-min nap opportunity every hour. Sleepiness was assessed both subjectively, by the Stanford Sleepiness Scale, and objectively, by a modified version of the Multiple Sleep Latency Test. The PLR in response to a flash of light was recorded every 2 hr, immediately before a nap period. Results showed that baseline pupil diameter became smaller with progressive sleep restriction, but there were no changes in any of the parameters of the PLR despite significant fluctuations in sleepiness. Some of the changes in the PLR were significantly related to changes in baseline pupil diameter. When baseline diameter was partialled out, there was still no effect of sleepiness on the PLR. The results suggest that the PLR cannot be used as a measure of sleepiness.

[1]  M. Pressman,et al.  Relationship of autonomic nervous system activity to daytime sleepiness and prior sleep. , 1989, Sleep.

[2]  E. Hoddes,et al.  The history and use of the Stanford sleepiness scale , 1971 .

[3]  J. Penney,et al.  Dopamine‐receptor autoradiography of human narcoleptic brain , 1992, Neurology.

[4]  J. Lauber,et al.  Sleepiness, circadian dysrhythmia, and fatigue in transportation system accidents. , 1988, Sleep.

[5]  W W Tryon,et al.  Pupillometry: a survey of sources of variation. , 1975, Psychophysiology.

[6]  I. E. Loewenfeld,et al.  Disintegration of central autonomic regulation during fatigue and its reintegration by psychosensory controlling mechanisms. II. Reintegration; pupillographic studies. , 1952, The Journal of nervous and mental disease.

[7]  Roger Broughton,et al.  Pupillometric assessment of excessive daytime sleepiness in narcolepsy-cataplexy. , 1991, Sleep.

[8]  I. E. Loewenfeld,et al.  Electronic pupillography; a new instrument and some clinical applications. , 1958, A.M.A. archives of ophthalmology.

[9]  M. Carskadon,et al.  The multiple sleep latency test: what does it measure? , 1982, Sleep.

[10]  B. Goldwater.  Psychological significance of pupillary movements. , 1972, Psychological bulletin.

[11]  I. E. Loewenfeld,et al.  Pupillary Movements During Acute and Chronic Fatigue A New Test for the Objective Evaluation of Tiredness , 1963 .

[12]  M. Pressman,et al.  Senile miosis: the possible contribution of disordered sleep and daytime sleepiness. , 1986, Journal of gerontology.

[13]  I. E. Loewenfeld,et al.  Types of central autonomic innervation and fatigue; pupillographic studies. , 1951, A.M.A. archives of neurology and psychiatry.

[14]  Pupillometry in clinical psychophysiological diagnostics: methodology and proposals for application in psychiatry. , 1992, The Israel journal of psychiatry and related sciences.

[15]  Influence of retinal adaptation upon the pupillary reflex to light in normal man. II. Effect of adaptation to dim illumination upon pupillary reflexes elicited by bright light. , 1961, American journal of ophthalmology.

[16]  I. E. Loewenfeld,et al.  II. Reintegration. Pupillographic Studies , 1952 .