A new large-scale study revealed that 9.6 million or nearly four percent of adults in the United States are suffering from myopia or severe nearsightedness, with nearly 820,000 of those experiencing progressive high myopia and more than 41,000 having myopic choroidal neovascularization that could cause long-term vision loss.

The number of nearsighted people in the United States has increased from 25 percent in the early 1970s to 40 percent around the turn of the millennium.

The study, published in the journal Ophthalmology, is the first ever large-scale study ever-done to calculate the real-world prevalence myopic choroidal neovascularization in the United States.

According to the study, women have higher prevalence of myopia with 527,000, compared to 292,000 men suffering from the same condition. Also, the prevalence rate of myopic choroidal neovascularization is two times higher than men.

"Prior to this study, we really had no idea how many people had myopic choroidal neovascularization, which can be devastating," said Jeffrey Willis, M.D., Ph.D., a retina fellow at the UC Davis Eye Center and a clinical research fellow at Genentech and lead author of the study, said in a statement. "I think the findings emphasize the growing issue of nearsightedness and the burden it creates in terms of medical complications that cannot be fixed with just glasses or contacts."

For the study, researchers look into the diagnostic data from 8,865 participants in the National Health and Nutrition Examination Survey (NHANES) from 2005 through 2008. They also took into account the 2014 data of 2.6 million individuals in the Academy's IRIS Registry. They then applied the prevalence to 2014 U.S. Census Bureau population numbers to accurately calculate real-world prevalence of myopic choroidal neovascularization.

The IRIS Registry only comprehensive database of ophthalmic patient outcomes in the United States containing clinical information from 88 million office visits to 13,739 ophthalmologists and eye care professionals.

"The sheer size of the IRIS Registry gives us tremendous research capabilities we did not possess before in ophthalmology," said retina specialist David W. Parke, II, M.D., CEO of the American Academy of Ophthalmology and a co-author of the study, in a press release.