**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}.