A fundamental step-transition in retinal function at low light intensities

ABSTRACT There appears to be a fundamental step‐transition in retinal function at low light intensities, close to the scotopic‐mesopic transition. This step‐transition is observed for elements of the retinal dark‐light switch, which has been described in the chicken retina. Over the same range of light intensities, there is a step‐transition in photoreceptor retinomotor movements and in the coupling of horizontal and All amacrine cells, which suggests a switch in retinal circuitry from rod‐processing to cone‐processing regimes. A similar step‐transition in pineal function suggests that the retinal step‐transition signals to the central circadian systems. Finally, this step‐transition may also inhibit eye growth, and thus be responsible for the reported diurnal rhythm in eye growth. Disturbances to this step‐transition may be the initial cause of disordered eye growth in the form‐deprivation myopia paradigm.