Recent cascaded-integrator models do not fit the sine-wave flicker thresholds as well as we might wish, but neither does the Ferry-Porter law. In fact, the Ferry-Porter function is not physically realizable as a linear model. By modifying it to yield realizable responses like those of the cascaded integrator, we obtain a much simpler model, which appears to be a special case of the photochemical diffusion mechanism proposed by Ives and more recently by Veringa. This model is a good fit, not only to the flicker data, but also to human phase-shift measurements obtained by the phosphene method. We infer that receptor-cell properties probably control the high-frequency linear filtering of flicker waveforms.
D. H. KELLY, "Diffusion Model of Linear Flicker Responses," J. Opt. Soc. Am. 59, 1665-1670 (1969)