How do spontaneous pupillary oscillations in light relate to light intensity?

Characteristics of light-induced pupillary oscillations at constant light intensities have been investigated sparsely compared to sleepiness-related pupillary oscillations in darkness. This study presents the first controlled analysis of light-induced pupillary oscillations and their relationship to illumination. Pupillary oscillations of alert subjects were recorded by infrared video pupillography in different background lighting. Although showing obvious relationships of mean frequency and amplitude to light intensity, there were considerable inter- and intra-individual differences in the appearance of light-induced oscillations. As they looked rather similar to sleepiness waves, the question remains to identify light-induced oscillations in day light and to differentiate them from sleepiness-related oscillations.