A study of the human rod and cone electroretinogram a-wave component

Abstract

The study of the electrical response of the retina to a luminous
\nstimulus is one of the main fields of research in ocular electrophysiology. The
\nfeatures of the first component (a-wave) of the retinal response reflect the
\nfunctional integrity of the two populations of photoreceptors: rods and cones. We
\nfit the a-wave for pathological subjects with functions that account for possible
\nmechanisms governing the kinetics of the photoreceptors. The paper extends a
\nprevious analysis, carried out for normal subjects, in which both populations are
\nactive, to patients affected by two particular diseases that reduce the working
\npopulations to only one. The pathologies investigated are Achromatopsia, a
\ncone disease, and Congenital Stationary Night Blindness, a rod problem. We
\npresent evidence that the analysis of a pathological a-wave can be employed to
\nquantitatively measure either cone or rod activities and to test hypotheses about
\ntheir responses. The results show that the photoreceptoral responses differ in the
\ntwo cases and functions implying a different number of photocascade stages are
\nnecessary to achieve a correct modeling of the early phototransduction process.
\nNumerical values of the parameters characterizing the best-fit functions are given
\nand discussed.