Incidence of cataracts in rhesus monkeys treated with whole-body irradiation.

The incidence of cataract formation was investigated in rhesus monkeys exposed to different doses of whole-body irradiation. Application of 850-900 rad (8.5-9 Gy) caused cataracts in 17% of the monkeys within 3 years after treatment; after 10 to 15 years, incidence increased to 100%. "Young" lenses showed a significantly lower incidence than "adult" lenses, although no differences in the stage of cataractogenesis could be demonstrated. Sex differences did not play a role in incidence and severity of cataracts. Lower doses (400 rad or 4 Gy) did not cause cataracts. In view of the close similarity between monkeys and humans, these results indicate that a single dose of 850-900 rad, sometimes employed in the treatment of acute myeloid leukemia in children, carries a strong risk of cataract development.