Abstract
<h3>To the Editor.</h3> —In the course of the third program of the US National Health Survey,<sup>1</sup>the opportunity was taken to estimate incidence of color vision deficiency in a specially selected group, designed to be a fair sample of youths between the ages of 12 and 17 years. Taking into account age, sex, race, family income, geographic region, and population size of place of residence, a stratified probability sample in each of five successive stages was taken; details of the method are given in an appendix.<sup>1</sup>The object of the study was to determine factors of physical and intellectual growth and development. Color vision testing was performed in the total sample by means of a selection of seven Ishihara plates, as suggested by Sloan and Habel.<sup>2</sup>Those failing any of the Ishihara plate tests were then screened with the American Optical Company (AOC)<sup>3</sup>and Hardy-Rand-Rittler (HRR)
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