Fig. 2. Electroretinogram (ERG) responses for a normal subject and four patients with retinitis pigmentosa (ages 13, 14, 14, and 9). Responses were obtained after 45 minutes of dark adaptation to single flashes of blue light (left column) and white light (middle column). Responses (right column) were obtained to 30 cps (or 30 Hz) white flickering light. Calibration symbol (lower right corner) signifies 50 msec horizontally and 100 μV vertically. Rod b-wave implicit times in column 1 and cone implicit times in column 3 are designated with arrows. (From Berson EL. Retinitis pigmentosa and allied diseases: electrophysiologic findings. Trans Am Acad Ophthalmol Otolaryngol 1976;81: 659.)