Spectral sensitivity changes with time of day Figure ERG responses to test wavelengths spanning the visible spectrum were measured in dark-adapted animals day and night. The smooth curve is a nomogram for a rod photopigment based on microspectrophotometric measurements. In the vicinity of 610 nm, the spectral sensitivity of the b-wave does not change significantly from day to night, indicating that this is an isosbestic region. The shift of peak spectral sensitivity to longer wavelengths during the day is associated with an approsimately sixfold or 0.8 log unit decrease in sensitivity. More than 100-fold decreases in sensitivity were detected for the responses to shorter wavelength flashes.
Rods dominate at night while cones dominate during the day.
ERGs were recorded from a single eye. Many of the physicians at University Hospital are also professors at one of the Upstate Medical University's four colleges.