Rod-cone dystrophy associated with a rod system electroretinogram obtained under photopic conditions

A 14-year-old girl with a history of night blindness and poor visual acuity was examined. Cystic-appearing lesions were apparent in the fovea, and pigmentary changes were observed in the midperipheral retina. Electroretinograms (ERGs) recorded from the dark- and light-adapted eye were similar in waveform, implicit time, and approximate amplitude. Results of examination of the spectral characteristics of the light-adapted ERG demonstrated that the recordings represented activity of the rod system, despite the presence of a background field, which eliminates the response of the rod system in normal subjects.