Fig. 10. Full-field electroretinograms (ERGs) to red (top) and blue (middle) light, equal for rod vision, and brighter white stimulus (bottom) from patient with hereditary abetalipoproteinemia (dark-adapted). Responses in left column were obtained before vitamin A therapy, those in middle column at 6 hours, and those on right at 24 hours after vitamin A therapy. Two to three responses to same stimulus are superimposed. Light stimulus begins with each trace. Calibration (lower right) signifies 0.06 mV vertically and 60 msec horizontally. (From Gouras P, Carr RE, Gunkel RD. Retinitis pigmentosa in abetalipoproteinemia: Effects of vitamin A. Invest Ophthalmol Vis Sci 1971;10:790.)