Interpretations of Naka-Rushton parameters from patients with ADRP and CRD.

Abstract

Since the Naka-Rushton eq was first shown to fit the change in trouh-to-peak b-wave amplitude with flash intensity1,2, it has been fitted to b-wave data from a large number of patients. The parameters estimated from these fits, the semisaturation intensity (K) and the maximum response (Vmax) are affected in different ways by different diseases. Fig. 1, from Birch et a13, shows the deviations from the normal parameters for 41 patients with cone-rod dystrophy (CRD) or autosomal dominant retinitis pigmentosa (ADRP) retaining measurable rod ERGs. Each data point represents an individual patient and shows the change in log K and the change in log Vmax from the log of the mean normal. Typical of diseases of the receptors, these patients show large changes