Pupillary Hippus: A Clearly Chaotic and Highly Organized Oscillation

The conventional model for the activity of the pupils is that of a linear control model. This predicts that pupil size would vary inversely with the amount of incoming light and in a constant light would remain a constant size. A typical recording of pupil size under such circumstances, however, shows marked spontaneous activity with an irregular pattern of aperiodic oscillations. Previous works have called this random noise.