Figure 1. Electroretinographic (ERG) analyses of rod photoreceptor and postreceptor neural function. A: Sample ERG responses from a P25–P26 control rat elicited with green LED (left) and “white” xenon arc (right) full field stimuli. The number of rhodopsin photoisomerizations per rod (R*) produced by each flash is indicated at the end of each trace. Traces are numbered for reference in panels B and C. B: Determination of rod photoreceptor function. Sensitivity of the rods, S_rod, is determined by fit of Equation 3 (red dashes) to the leading edge of ERG a-waves (circles) elicited with bright flashes. For this subject, S_rod was 3.79 R*⁻¹∙s⁻². C: Determination of postreceptor function. The b-waves elicited by dim flashes (left panel) were scaled by the intensity of the flash used to elicit them (middle panel) and the Michaelis–Menten equation with the exponent set to −1 (Equation 4) fit to the resulting scaled response amplitudes (right panel). The limit of the function as intensity approaches zero, Sm, defines postreceptor sensitivity. For this subject, Sm was 224 µV∙R*⁻¹.