The other primary objective of this trial was to assess the antioxidant effects of beta-carotene (50 mg on alternate days) on cataract development. In addition, factors that have been suggested to be cataractogenic were assessed in prospective cohort studies. These factors included age, blood pressure, blood cholesterol, height, diabetes, medication use, cigarette smoking, and history of previous eye trauma or surgery. In addition, the possible associations between history of vitamin E and selenium intake and cataract were explored.