Pupillometric discrimination of insomniacs.

Unlike the multiple sleep latency test, pupillometry does not require sleep to test sleepiness, which may be an advantage in assessing insomniacs. Pupillometry was employed to study possible differences in daytime sleepiness between insomniacs and noninsomniacs. Thirty self-defined insomniacs and an equal number of noninsomniacs, age 30-50 yr, submitted to four 10-min pupillometry sessions distributed from early morning to bedtime. The sessions consisted of infrared television monitoring of the pupil in a totally dark, nonstimulating environment. Insomniacs exhibited significantly smaller pupil diameters than noninsomniacs, and this effect persisted in all sessions. However, the size of effect averaged about 0.5 mm, and this was judged to be a small magnitude. Heightened subjective sleepiness discriminated the insomniacs in only the midday session. The absence of polysomnography was a methodologically limiting factor. Theoretical and clinical implications of these data were discussed.