Rod influence on thresholds using different detection criteria during dark adaptation

Abstract

Following adaptation to intense long wavelength (LW) light, dark adaptation was measured with an extrafoveal 660 nm test flash using three different criteria: reporting the test flash as present (detection threshold), as colored (the chromatic threshold), and as red (the color-specific threshold). The detection threshold followed the typical dark adaptation course. The chromatic threshold first fell to a steady level but then rose to a higher level. The color-specific threshold first dropped, and then rose. These threshold rises are attributed to the action of rods since they do not occur in the fovea and are delayed following adaptation to short wavelength light of equal photopic, and stronger scotopic, intensity to the LW light adaptation.