MINNEAPOLIS (WCCO) — In the last 30 years, the number of us who are nearsighted has doubled. So, why do so many of us need glasses? The answer may have something to do with what we’re seeing so much of.

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According to one study, in the 1970s, 25 percent of Americans were nearsighted. Now, 42 percent are. The Vision Council of America also says that 75 percent of adults use some sort of vision correction.

Dr. Marcie Nichols from Perspectives Vision Clinic of Minneapolis says, in this case, perception is reality.

“It’s partly genetics and it’s partly visual stress. The way we use our eyes over the past 30 years has increased dramatically,” Nichols said.

For example, many are now looking at phones, computers and playing video games for hours.

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Some studies suggest the sun may be another factor to focus on. Eyes originated when we spent most of our days outside now we’re living indoors in artificial light. Bright outside light helps developing eyes keep the right distance between the lens and retina, which helps us focus. However, dim lighting doesn’t do the same thing.

“It’s not necessarily the sunlight perhaps, but it’s more they are spending more time outside instead of reading,”Nichols said.

Nichols believes the biggest reason we are seeing clearly comes down to options.

“There is definite increased awareness and need for vision correction and there’s greater access to care, obviously,” she said.

There’s an exercise Doctor Nichols suggests called the “20/20 rule” to help your vision. For every 20 minutes you spend looking at something, look away for 20 seconds and try to focus on something far away.

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On a related note, doctors say carrots do help your vision. They contain Vitamin A which is absorbed by your retinal cells.