Genetic Epidemiology of Refractive Error

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Project Summary/Abstract Refractive error is the most common eye disorder in the world, and its public health and economic impact are considerable. Treatment of the U.S population for refractive error costs twice as much as glaucoma and 10x the amount for AMD or diabetic retinopathy and is a major burden to the U.S. public health system. Current treatments for refractive error are not directed at the secondary complications. Such complications include choroidal neovascularization, retinal detachment and glaucoma. Glaucoma is a complication of myopia; prevalence of glaucoma is 4.2% in eyes with low myopia and 4.4% of eyes with moderate to high myopia compared to 1.5% of eyes without myopia. Individuals with hyperopia are 40% more likely to develop ocular hypertension than those who are emmetropic. Retinal detachment is increased in eyes with refractive error; risk of retinal detachment is increased 4-10 fold in myopic eyes. Finally, the risk for choroidal neovascularization is increased from 2-fold for mild myopia to 9-fold for severe myopia. Current treatments do not prevent the ocular complications secondary to refractive error because they are not targeted at stopping progression of refractive error. Previous attempts to control progression of refractive error with optical and drug approaches have met with limited success. There is extensive evidence for significant heritable components for hyperopia and myopia. If one can identify the genes involved in these disorders, one can identify unsuspected disease mechanisms, develop animal models of these mechanisms and use these models to develop and test new treatments, identify interactions of these genes with modifiable environmental risk factors, and treat people very early in the course of the disease to prevent secondary complications. One of the major challenges now facing biomedical research is the discovery of specific disease mechanisms that underlie heritable disorders that display a complex mode of inheritance. This includes complex eye diseases such as refractive error. An appealing hypothesis is that sequence variations play an important role in refractive error similar to other complex diseases. Advances in genetic technology and bioinformatics have made it possible to perform experiments that examine hundreds of thousands of genetic variants in large numbers of individuals and to determine their location and significance in influencing disease. We and others have conducted experiments to identify genetic loci for refractive error in families using microsatellite markers followed by single nucleotide polymorphisms for fine mapping. In this proposal, we will extend our previous work to facilitate the discovery of additional genes involved in refractive error. This work will take advantage of already acquired DNA samples from thousands of well-characterized patients. Our work has the potential of discovering novel sequences and genes that interact with environmental risk factors, as well as categories of sequence elements that play a primary or modifying role in refractive error.