A study recently published in the Archives of Ophthalmology shows that the proportions of Americans affected by myopia has grown considerably in the last 30 years or so. Based on comparable measuring methods, they accounted for 41.6 percent of the population between the ages of 12 and 54 during the 1999-2004 period, compared with 25 percent in 1971-72. The data were obtained through the National Health and Nutrition Survey.