There are far more Americans diagnosed with nearsightedness than just three decades ago, according to a report released Tuesday.
Also known as myopia, nearsightedness is when the eyes cannot focus correctly, resulting in the blurring of distant objects. Fortunately, it is easily remedied with corrective eyeglasses, contact lenses or refractive surgery.
It is still a mystery as to why an increasing number of Americans are becoming nearsighted.
“At this time, we really don’t know how to prevent myopia,” Dr. Susan Vitale of the National Eye Institute, part of the National Institutes of Health in Bethesda, Maryland, noted in a telephone interview with Reuters Health.
“It’s really important to get regular eye examinations from an eye care professional,” she said.
Vitale and her colleagues used data from the National Health and Nutrition Examination Survey (NHANES) to compare the percentage of black and white Americans between the ages of 12 to 54 with myopia in 1971-1972 and 1999-2004.
The same methods were implemented to determine myopia during both time periods. “We wanted to make it as similar as possible to get a feel for whether the prevalence was actually increasing or not,” Vitale explained.
They discovered that between 1971 to 1972, 25% of Americans from ages 12 to 54 had myopia. This number jumped to 42% in the 1999-2004 period.
In the 1999-2004 period, the prevalence of myopia was about 66% higher, the investigators wrote in the most recent issue of Archives of Ophthalmology.
Vitale did not find this to be a surprise, considering reports from Asia, Australia, Africa, and Israel that suggest that the prevalence of myopia is increasing in those regions, she told Reuters Health.
“This is something that has been on the radar for a while,” Vitale said, “but it’s the first time that we have tried to nail it down as carefully as possible in the US.”
The differences in myopia rates were astounding among black people, in whom the 1999-2004 rates were “more than double” the rates in the earlier time period. Among the white participants, the 1999-2004 rates were 63% higher than those in 1971-1972. In 1999-2004, myopia rates in both genders were 64% and 69% higher, respectively, than in 1971-1972.
It is still unclear what exactly causes myopia, but there are several risk factors, including being born prematurely or genetics. “If your parents are myopic, you are more likely to be myopic,” Vitale said.
Other studies have also linked myopia to activity that requires close examination, such as reading, sitting at a computer screen, or using small electronic devices. Vitale said this is a “reasonable” possibility, considering how much work and entertainment patterns have changed over the past 30 years.
She also mentioned a study in Australia which found evidence that children who spent the most time outdoors were the least likely to suffer from myopia.
“Outdoors you have different lighting conditions and you are looking at distant objects instead of near objects,” Vitale noted, and these are both contributing risk factors for myopia.
Though the treatment of myopia is relatively simple, the costs add up when taking its prevalence into account. Vitale and colleagues said in the report, “If 25 percent of those aged 12 to 54 years had myopia, the associated annual cost would be more than $2 billion; an increase in prevalence to 37 percent would increase the cost to more than $3 billion.”
They concluded that by determining modifiable risk factors for the development of myopia, it could ultimately lead to the development of cost-effective options.
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