Fundus pigmentation and the dark-adapted electroretinogram

Abstract

Dark-adapted electroretinograms were obtained over a 3.6-log range of stimulus intensities from 17 black and 15 white normal subjects. Subjects were grouped on the basis of light or dark fundus pigmentation, determined from digitized fundus photographs. B-wave amplitudes for each group were fitted by the Naka-Rushton equation, and the measures Vmax, log K, and n were determined. The luminance-response functions revealed that subjects with light fundi had larger b-wave amplitudes at all luminance levels. There was a significant difference between groups for Vmax and n but not for log K. A comparison of b-wave implicit times showed no significant difference between subjects with dark and light fundi. Ancillary tests and multiple regression analysis suggested that the relationship between Vmax and fundus pigmentation could not be attributed to age, gender, refractive error, axial length or intraocular pressure. The results have implications for the collection of normative electroretinographic data and for the interpretation of electroretinogram results.