Slowing myopia progression or eventually preventing myopia onset could potentially affect approximately 60 million children in the United States alone. While the consequences of myopia are rarely sight-threatening, the quality of life for myopic patients is negatively affected and the health care costs to treat myopia are astronomical (approximately $4.6 billion in 1990). The National Eye Institute recognizes the need to "evaluate the efficacy of potential treatments for delaying the onset or for slowing the progression of myopia, such as lenses that alter peripheral defocus."