The Luminance-Response Function of the Dark-Adapted Rabbit Electroretinogram

The Naka-Rushton equation of the form, R = Rmax Iⁿ/(Iⁿ+Kⁿ), has been used to describe the b-wave luminance-response function of the scotopic electroretinogram. Rmax is the asymptotic value of the b-wave amplitude as a function of stimulus luminance I, K is the luminance that produces a b-wave amplitude that is one-half Rmax, and n is a dimensionless constant that controls the slope of the function. These three parameters are often used in research laboratories, since it can show selective changes in each parameter. The present study describes these parameters (Rmax = 354 ± 28 uV, n = 0.80 ± 0.06, log K = -2.26 ± 0.15 log ed. sec / m² ) and the values obtained from the derivative analysis of Naka-Rushton equation (Anastasi et al)in 20 normal pigmented rabbit eyes. However, Naka-Rushton equation accurately describes the function only at low to moderate flash luminances. At high flash luminances, a second amplitude increase appears in the function.