Whether Apple's new tablet computer marks a revolution in personal computing or misses that mark entirely, one thing is clear: Whoever buys the iPad, which lands on April 3, will spend more time than ever in front of a screen. The rest of us aren't far behind. Smaller and faster microchips continue to consolidate the movie theater, the television, and the book onto a single viewing plane, and one that's getting progressively closer to our eyes. As our viewing technology evolves—from the desktop to the laptop, the smartphone, and now the tablet—we're being sucked ever closer, and for increasing periods of time, to the flickering glow of our screens.
Manufacturers, in response, have tried to make our intimate relationships with their devices less physically demanding. In the realm of electronic reading, the iPad will compete with Amazon's Kindle, Barnes & Noble's Nook, and the Sony Reader—each of which displays text in E Ink, a technology that mimics certain aspects of the printed page. Those companies argue that E Ink makes reading more ergonomic than it would be on self-illuminated screens like the iPad or your personal computer. They boast of having displays that "go easy on your eyes," "with the same appearance and readability" of regular paper. There's no doubt that a long session of computer-based reading can leave your eyes irritated and your brain woolly. But are self-illuminated screens really to blame? And will long days and nights curled up with the iPad only make things worse?
Let's tackle the gravest concern: that reading off a computer might give us something worse than tired eyes. For years, doctors have wondered if monitors might cause permanent vision damage. It's a tempting charge. Consider that the prevalence of myopia has risen by two-thirds in the United States since the 1970s and that the shocking spread of nearsightedness coincides almost exactly with the perfusion of computers in our workplaces and homes. Several studies from the 1980s and early '90s found specific correlations between myopia and computer use or sitting close to the television. There's also evidence from extremely late adopters: Myopia among Alaskan Inuits, for instance, reportedly skyrocketed after they were introduced to television.
The most recent and rigorous research, however, has refuted the early studies: Screens don't cause myopia. A 1996 review concluded that "there is no compelling evidence" of computer use producing or aggravating myopia any more than other forms of "nearwork"—like reading, data entry, and embroidery. So working in front of a monitor could make you shortsighted, but so might staring at an old-fashioned book. To figure out how any form of reading might affect the eyes, doctors needed to track subjects over several years and compare their rates of myopia to the number of hours they spent reading, watching TV, using the computer, or playing video games.
Researchers in one study, published in 2007, followed 514 non-myopic California third-graders for five years. By eighth grade, just over 20 percent of the children had become nearsighted. The most important factor distinguishing those children from others was genetic: Children were five times as likely to develop myopia if they had two myopic parents instead of none, and twice as likely if just one parent was nearsighted. The amount of time they spent doing "nearwork" was irrelevant. Those findings largely confirm a similar study, published in 2006, of nearly 1,000 Singaporean children. In that case, children who developed myopia read just as many books as the others. Though genetics were less powerful in the Singapore study, parents' eyesight still predicted whether a child would develop myopia better than any other factor. (Among adults, the story is the same.)
But the root causes of myopia are still a mystery, and some researchers haven't let go of the idea that reading—on a printed page or a computer monitor—can damage your vision. Most prominently, Norwegian ophthalmologists found myopia was more likely to develop among undergraduates who spent the most time studying. Even so, they found no link between television or computer use and myopia. And a limitation of almost all these myopia studies is their heavy reliance on surveys, rather than direct observation, to measure time spent reading or sitting at the keyboard.
There's plenty of evidence, however, that books, computers, and televisions can give us what ophthalmologists call "transient myopia"—that bleary-eyed, slow-to-focus feeling you get after a long stretch of reading. To focus on anything close, our eyeballs rotate toward each other, so that their sight lines converge at the point of interest. Then, a ring of muscle behind each iris contracts, allowing each lens to bulge into a more spherical shape. In their resting state, our eyes tend to focus about 2 feet ahead of us and cross paths about 2 feet farther, though those distances can vary greatly. Just an hour of reading (from a page or a screen) at 20 centimeters' distance shifts these resting states several inches closer to our nose, causing a temporary lack of focus on distant objects. Transient myopia won't cause permanent nearsightedness, but it's a major inconvenience—and not one to be taken lightly, given how much time we spend reading and staring at screens.