The researchers found that 41 percent of the sample had myopia, as compared to 25 percent three decades earlier. While myopia of all levels registered an increase, the data showed that severe myopia was twice as prevalent among younger adults (ages 20 to 39) as among the elderly.

All races included in the study showed a higher prevalence, but increase rates were greater for black participants than for white participants. "Black participants surveyed in 1971 to 1972 may have had less access to educational opportunities than white participants and consequently experienced less exposure to near work (a risk factor for myopia)," the authors wrote. "As racial inequities in educational opportunities decreased, near-work exposure may have increased relatively more in black participants than in white participants."

The 2009 study is hardly the first to suggest that an increase in years of formal education and access to technology across society may account for higher myopia rates in recent years. Ophthalmologists and optometrists have cautioned that close-up activities like reading and using computers, tablets, and smartphones interfere with normal blinking and put a strain on the eyes. When abused, they can lead to double vision, myopia, and serious conditions such as retinal detachment and vision loss. The overuse of handheld electronics such as iPads and tablets by young children is especially worrisome, since their eyes are still developing and are more likely to be affected, according to researchers at the University of California, Berkeley.

Kathryn Rose, a researcher of visual disorders at the University of Sydney's college of health sciences, recently concluded that spending too much time indoors also has a huge impact on eyesight deterioration. Rose said in a CNN interview that she was not sure how time spent using digital media relates to myopia progress, but that outdoor light has been shown to have a positive effect on vision. Studies from the U.S., Singapore, and China confirm a link between the time spent outdoors and the prevention of myopia, Rose said. However, both the level of light and the duration of exposure to outdoor light must reach a certain threshold to have a preventive effect, according to one of her studies. Spending at least 10 to 14 hours outside per week may prevent the early onset of myopia, she concluded.

The sudden surge in myopia cases in the past few decades, as documented by Vitale's 2009 study, prompted researchers and policymakers to look for answers to what may become a costly public health issue. If 25 percent of those aged 12 to 54 years in the U.S. had myopia, direct medical costs and associated productivity losses would amount to more than $2 billion per year; an increase in prevalence to 37 percent would increase the cost to more than $3 billion, according to the National Institutes of Health study.