II Quantum Fluctuations in Vision

Publisher Summary This chapter deals with the quantum fluctuations in vision. The theoretical concept that visual detectability is governed by chemical mass action laws and chemical equilibrium between intact and bleached regenerating retinal pigment, is instead receiving all the attention. This is remarkable as it can have been clear from the onset that such an approach is incompatible with the “few-quanta-only’’ concept. A whole framework of theoretical ideas and corresponding experimental studies has been founded on the basic concept that the visual detection capacity is limited by quantum fluctuations. Further, light intensities on the retina can be measured by diverting a fixed fraction to a physical light detector but quantal hits on the retina cannot be measured that way, because of their statistical spatial and temporal nature. Therefore, it was of paramount importance when the first announcements of electrophysiological confirmations of so-called quantum bumps appeared. The chapter also discusses the electrophysiological evidence of the quantum events.