Der Einflu\ sinusförmiger Leuchtdichteänderungen auf die mittlere Pupillenweite und auf die subjektive Helligkeit

Summary

The mean diameter of the human pupil was measured during stimulation of the eye with light of sinusoidally varying intensity and during stationary illumination with the corresponding average intensity. Continuous records of the pupil diameter were obtained using an electronic pupillometer. The light stimuli were electronically controlled by utilizing the Faraday effect and applied under “open loop” conditions. The pupil responded with a net contraction to modulation of the light intensity within a range of modulation frequencies up to 30 c/sec. The net contraction was maximal between 1 and 3 c/sec, but remained significant at high frequencies, which did not result in a periodic light reflex any more. The higher the modulation degree and the average intensity, the larger the net contraction. The dependence of the net contraction upon the modulation frequency is very similar to that of the subjective brightness (Brücke effect), although certain difficulties are encountered in attempting a direct comparison of the two phenomena.