Smooth pursuit eye movements among storage battery workers.

Eleven male workers in a battery storage plant with lead and erythrocyte protoporphyrin blood actual levels greater than 50 and 100 micrograms %, respectively, and 18 male controls without lead exposure were tested by a clinical pendular eye tracking test (PETT). Each worker underwent a series of lead absorption measurements including blood lead, urinary lead, erythrocyte protoporphyrin, delta-aminolevulinic acid dehydratase activity, and urinary delta-aminolevulinic acid. The SPEMs were evaluated by an eye tracking technique. The subjects followed a horizontally moving target which, in the form of a luminous spot on a dark background, was projected onto a screen placed 1 m from the subject. The maximum predicted eye movement velocity during tracking was about 30 degrees/s. Skin electrodes were applied on the outer canthi of both eyes and SPEM were plotted on a polygraph, recording both the actual eye movements and the corresponding first derivative. Our findings suggest that lead workers display a disorder of motor coordination of SPEMs system, and the PETT is useful, when associated with biochemical data, to evaluate the degree of subclinical damage of nervous system during lead poisoning.