Scotopic vision deficits in young monkeys exposed to lead

Rhesus monkeys were reared on diets designed to produce blood lead concentrations of 14 (untreated), 55, or 85 micrograms per 100 milliliters for the first year of life. Eighteen months later, blood lead levels were normal in all animals. At this time, however, visual discrimination performance in the 85-microgram group was impaired under dim light relative both to their own performance under bright light and to the performance of the other groups under all light levels used. We interpret these results to reflect a deleterious, enduring impairment of scotopic visual function (night blindness) as a result of early lead intoxication.