—Randomized trials of beta carotene or any one vitamin will not be able to answer all questions about the role of all antioxidants in the development or progression of age-related eye disease. The Editorial1 accompanying our article reminds us that the success of the clinical trials in finding an association "depends on giving the appropriate nutrient, in the appropriate dose, for an appropriate period of time, to an appropriate population. Failing to meet any one of these requirements will reduce or eliminate the probability of finding an effect even if one exists." As we discussed in our article, observational studies and clinical trials both can contribute to our understanding of the relationship between antioxidants as well as other nutrients and risk of chronic eye disease.
Seddon JM, Willett W, Sperduto RD. Dietary Carotenoids, Vitamins A, C, and E, and Macular Degeneration-Reply. JAMA. 1995;273(23):1835. doi:10.1001/jama.1995.03520470043026