Cone electroretinographic change during light adaptation in retinitis pigmentosa

Cone electroretinograms (ERGs) to 30-Hz full-field white light were recorded after dark adaptation from 33 patients with retinitis pigmentosa and 8 normal subjects over a period averaging 8.5 min. Most patients and all normal subjects showed increases in amplitude that approached or reached maximum by the end of the recording. Regression analyses revealed that patients with smaller baseline amplitudes tended to show larger and faster increases in relative amplitude than patients with larger baseline amplitudes, whose amplitude changes over time were comparable to those seen in normal subjects. These findings suggest that both the magnitude and kinetics of cone ERG amplitude change to a light-adapting, flickering stimulus are related directly to the level of cone malfunction in retinitis pigmentosa.