Eccentricity and the Ferry-Porter law.

Is the flicker limit governed by the Ferry-Porter law or by some other law? We previously obtained strong evidence for the wide applicability of the Ferry-Porter law and for its variation with eccentricity [J. Opt. Soc. Am. A 7, 743 (1990)]. Raninen and others [Vision Res. 28, 785 (1988); 31, 1875 1875 (1991)] have questioned our analysis of the data and our conclusions. We show that their criticism of the Ferry-Porter law is based on specious analyses and that their own data support the Ferry-Porter formulation. We also provide further evidence that the slope of the Ferry-Porter function increases markedly with eccentricity, implying that the inherent temporal properties of the retina grow more rapid with distance from the fovea.