Robert DiMartino, OD, Professor Emeritus at the University of California, Berkeley, School of Optometry and a board member of BerkeleyWellness.com, warns about the effects of overuse of laptop computers, tablets, cell phones, and now iWatches on our vision. With the growing popularity of mobile devices, most of us spend more and more of our time interacting with the world on small glowing screens. While there are many benefits to having the world at our fingertips, spending too much time focusing up close may be harming our eyes. Dr. DiMartino explains the threat and what we can do to keep our eyes healthy.
First, is there evidence that vision problems are on the rise?
Absolutely. Several studies have tracked a dramatic increase in myopia, or near-sightedness, among people in Asian countries, especially China. Sixty years ago, only 10 to 20 percent of the Chinese population was near-sighted. Today 90 percent of children and young adults have myopia, according to research. And now we’re seeing the same trend in the west. A growing number of people are becoming nearsighted. And the degree of nearsightedness is becoming more extreme. So there’s an increase both in the prevalence and the magnitude of myopia.
Is myopia associated with any other eye conditions?
If you develop myopia, you’re at increased risk of at least two other eye conditions: glaucoma and retinal detachment. Let me explain why. People become nearsighted because their eyeball has grown longer, so light entering the eye can’t focus directly on the retina as it does with a normal shaped eye. When the eye elongates, it also stretches the retina, which increases the risk of retinal detachment. Elongation also causes subtle changes to the structure of the eye, increasing the danger of glaucoma.
Why are people’s eyes changing shape?
We think it may be because we’re spending so much time focusing close-up. When a young person looks at a close target, he or she has to increase the power of the eyes’ focusing system. The eyes go through a process we call accommodation. The optical power of the eye increases to bring the near object into focus. When we spend a lot of time looking at a near target, there is a constant demand on the eye to focus that image. The eye tries to adapt to what is now the new normal, which is this close viewing distance. It elongates so that the light from close objects is more effectively focused on the back of the eye. That’s great for close viewing. But when we look at distant objects, because the eye has elongated, we can’t focus as well.
There may also be another factor at work. When we focus on near objects, there are areas on the retina where the image is defocused. Those areas of defocus may stimulate the eye to accommodate by growing, adding to the problem of myopia.
You mentioned young people. Is this mostly a problem when the eye is developing?
We’re certainly seeing increases in myopia among younger and younger people. But we’re also seeing it in adults. In fact, we see that one of the consequences of going to law school is that students may become more nearsighted. Students graduate with a law degree and greater myopia than they had when they first enrolled. It’s a casualty of the profession, because they spend most of their waking hours reading, often on a screen.
People have been reading books up close for centuries. What’s particularly harmful about mobile screens?
Some researchers are convinced that the blue light from laptop and mobile screens is a particularly powerful stimulus that may hasten the problem. I’m old-fashioned enough to think that books are easier on the eyes than mobile devices, because the contrast is better on a page. But the bigger problem, I think, is that with the advent of mobile devices, we spend so much more time focusing up close, and so much less time outside, focusing on distant objects. Our eyes need a balance between focusing up close and focusing at a distance in order to remain healthy.
Is the remedy for nearsighted as simple as spending more time outside?
I don’t want to suggest that laptops and smartphones are the only cause of all myopia. But it’s clear the risk is higher for children and young adults who spend most of their time looking at the world up close. And when children spend more time outdoors, their risk is lower. The recommendation is to encourage kids to play outside as well as work on their computers or videogames. It’s important to seek a balance where we're doing distant tasks as well as near tasks. As we’ve shifted from playing baseball and hide-and-seek to playing video games, we’re constantly stimulating the eye to become myopic. We need to encourage a better balance of activities that use close focus, like reading, and activities that use distant focus, like sports, hiking, and spending time outside.
Would you set a specific limit on how much time people should spend doing close-up work?
I don’t think we have a specific number. It’s a little like asking, “How much sugar should kids eat?” I can’t tell you. But I can tell you that if they eat too much sugar, it’s not going to be good for them. The message I want to get across is that throwing and catching a baseball or taking a hike is as important to a child’s healthy development as sitting in front of a computer screen. And the same goes for adults.
Is there anything else we can do to protect our eyes while using laptops or cell phones?
If you’re doing a lot of close-focus work, it may be helpful to wear contact lenses or glasses with a little magnification to make it easier to focus. This is still controversial. But the idea is that by making it easier to focus up close, the eye is less likely to become elongated. We don’t have enough experience yet to know if this works, but we tried it in my own family, and I think it helped. My wife, who is also an optometrist, became nearsighted as a young adult. I became nearsighted in 5th grade. My two children certainly were at risk for myopia, because genetics plays a powerful role in this condition. Research has identified dozens of genes linked to nearsightedness. So at a young age, we gave them reading glasses and asked them to wear them whenever they were reading, working on the computer, or doing any other extended close activity. Now, at age 24 and 22, they have normal vision, neither near-sighted nor far-sighted. I can’t prove that the glasses helped them avoid myopia, but I think they probably did.
Lots of websites promote eye exercises to prevent or improve myopia. Are exercises useful?
Eye exercises make people feel as if they’re doing something, taking a proactive step. And they can’t do any harm. But there’s no evidence that eye exercises prevent myopia. As I’ve said, the best thing you can do is take plenty of breaks from your laptop or mobile device to get out into the world, to balance close and distant focusing. I’m more and more convinced that finding that kind of balance, in many areas of life, is the key to being healthy.
This opinion does not necessarily reflect the views of the UC Berkeley School of Public Health or of the editorial board at BerkeleyWellness.com.