Fig. 18. Dark adaptation in an individual with Vitamin A deficiency (VAD) before during, and after 75 days of therapy with 15,000 IU of Vitamin A taken daily. The VAD patient initially had a delayed and slowed recovery of both cone and rode sensitivity that was exacerbated at high levels of bleaching. By 75 days, this patient's dark adaptation curves were identical to those of a normal (not shown). (Cideciyan AV, Pugh EN, Lamb TD et al: Rod plateaux during dark adaptation in Sorby's fundus dystrophy and vitamin A deficiency. Invest Ophthalmol Vis Sci 38:1786, 1997.)