High levels of astigmatism exist among Native American peoples. While the prevalence of astigmatism is well studied, its developmental course and visual consequences are poorly understood. the goal of the proposed research is to establish the relation between astigmatism and visual development in native american children, and to determine the optimum strategy to mitigate detrimental effects of astigmatism in this population. A three-state research protocol is proposed: Stage 1: the prevalence of corneal, internal, and total astigmatism (as well as prevalence of reduced acuity and meridional amblyopia) will be examined in preschool children 6 months to 6 + years of age who are members of a Native American tribe (the Tohono O'Odham Nation) in which a high prevalence of astigmatism is present. Stage 2: spectacle correction will be provided based on guidelines resulting from a poll of 334 pediatric eye care practitioners. All children whose astigmatism, myopia, hyperopia, or anisometropia is of a magnitude that would be corrected by 99% of those polled will be classified as High risk for refractive amblyopia and will have spectacles prescribed. children whose astigmatism would be corrected by 50% to 98% of those polled will be in the Moderate Risk group; these children will be randomly assigned to receive spectacle correction or no spectacle correction. the remaining children will be in the Low Risk group and will not receive spectacles. Stage 3: Follow-up assessment of refractive effort and visual acuity will be performed at intervals of one, two and three years, to determine whether spectacle correction reduces the prevalence of below-normal best-corrected acuity. the primary analysis will be ca comparison of best-corrected acuity results from children who were randomized to spectacle correction with results from those who were randomized to no spectacle correction. It is hypothesized that the proportion of children with below normal acuity will be smaller in the group of children randomized to spectacles than in the group of children randomized to no spectacles. This study will show the effect of astigmatism on visual development and will determine whether correction of astigmatism during the preschool years prevents the development of refractive amblyopia, or produces an alteration in emmetropization.
