Myopia (nearsightedness) is an important public health problem, which entails substantial societal and personal costs. It is highly prevalent in our society and even more frequent in Asian countries; furthermore, its prevalence may be increasing over time. High myopia contributes to significant loss of vision and blindness. At present, the mechanisms involved in the etiology of myopia are unclear, and there is no way to prevent the condition. Current methods of correction require lifelong use of lenses or surgical treatment, which is expensive and may lead to complications. The rationale for this trial, the Correction of Myopia Evaluation Trial (COMET), arises from the convergence of research involving (1) the link between accommodation and myopia in children and (2) animal models of myopia showing the important role of the visual environment in eye growth. A contribution of this research is that blur is a critical component in the development of myopia. The primary aim of COMET, to evaluate the efficacy of progressive addition lenses, a noninvasive intervention, in slowing the progression of myopia, follows from this line of reasoning. These lenses should provide clear visual input over a range of viewing distances without focusing effort by the child. The comparison of myopia progression in children treated with PALs versus single vision lenses will allow the quantification of the effect of PALs on myopia progression during the followup period.