Program Director/Principal Investigator (Last, First, Middle): Harvey, Erin M PROJECT SUIVIMARY (See instructions): The visual experience of the uncorrected astigmat provides a unique natural experiment on the effect of chronic blur on visual development. Studies of Tohono O'odham children, 30 to 40% of whom have visually significant astigmatism, provide a unique opportunity for investigation ofthe effects of astigmatism. The first aim is to study the stability of astigmatism in Tohono O'odham children over time, and to determine the anatomical origins of their astigmatism. Measurements of the posterior cornea will provide fundamental data on the origin of the internal astigmatism that often compensates for external (anterior) corneal astigmatism. The second aim is to determine how astigmats perform in the everyday complex visual environment. Specifically, we will examine the relation between astigmatic refractive error and (a) compliance with spectacle correction, (b) accommodation patterns, and (c) performance of complex perceptual tasks. By examining the influence of social, refractive, visual performance, and accommodation factors on compliance, we will provide a uniquely broad analysis of barriers to compliance, will provide essential information for development of strategies to increase treatment compliance in this population, and may identify barriers to compliance that are relevant to astigmats in general. Measures of accommodation under various task demand conditions will allow us to better understand how astigmats compensate for the unique persistent blur introduced by astigmatism, and will allow us to better understand how these strategies impact visual development. Finally, data on how astigmatism influences performance on tasks that require visual motor integration, reading fluency, and global perception of form and motion will provide valuable insight into how astigmatism impacts everyday functioning. In summary, access to this unique population of high astigmats introduces a valuable opportunity to conduct novel studies to further our understanding of the long-term stability and anatomic origins of astigmatism and to explore the effects of astigmatism on functioning in a complex visual environment. RELEVANCE (See instructions): This research will provide the first analysis of the anatomic origins of astigmatism in this population, generate important clinical information for development of guidelines for treatment and prevention of astigmatism-related amblyopia, and will further our understanding of the influence of astigmatism on visual functioning. Results will benefit astigmatic Tohono O'odham children and astigmatic children in general.