Prolonged staring at the computer screen does not cause shortsightedness also known as myopia. At least, no more than reading, writing and doing other near work activities. What does actually cause myopia?
Heredity and Living in a Big City
To start with, let me me mention that progressing myopia is more of a problem before you reach 30 years. When you stop growing, you still can have worsening myopia, but these cases are pretty rare and linked to some other, often more serious, health issues like diabetes. So, if you are grown-up, you can relax. Unless you have children or grandchildren below 30.
The Orinda Longitudinal Study of Myopia, having tracked 514 children from California from 1989 until 2001, allowed scientists to figure out which factors lead to developing shortsightedness. Analysis of this study performed by the researches at the University of Ohio showed that the main risk factor was genes: if one of parents is myopic, the chances that the child will be myopic too are 2.2 times higher than if no parent was shortsighted. If both parents had myopia, the risk of myopia for their child was 5.4 times higher!
Another factor is the level or urbanization in the area: the higher it is the more myopic its inhabitants are.
Other factors are much more controllable, but sometimes less certain.
Spending Too Much Time Indoors
The number of hours spent indoor was a good predictor of shortsightedness in the future, according to the above-quoted study.
The amazing results have been produced by another study that compared two groups of seven year olds: one from Sydney (124 children) with another one from Singapore (628 children). To rule out genetic factors, all kids were of Chinese ancestry and both groups had roughly the same share of children having shortsighted parents. The gender breakdown of both groups was about the same too (50% females in Singaporean group versus 53% females in the Sydney group). The diets were also very similar: both groups stuck to the Chinese cuisine with some elements of Western food.
Myopic happened to be 29% Singaporeans and only 3% Sydneans. Surprisingly, Sydneans spent more time reading than Singaporeans did. Not only that. They also spent more time writing. If that were not enough, the kids in Sydney played computer games more than in Singapore. In total, Sydneans spent on writing, reading, and playing computer games 6.4 hours a week more than Singaporeans. Australians watched a little bit less TV than Singaporean children, by 1.3 hours, which can hardly explain their significant better vision.
The only noticeable difference between Australians and Singaporeans was their level of outdoor and sport activities. Singaporeans spent on average 3 hours a week outdoor and practicing sport, while Australian kids spent on the same 13.8 hours a week. That is 4.5 times more!
Another study conducted among 12-year old Australians found that time spent outdoors was much more important than engagement in sports. Indoor sporting activity had no effect, whereas outdoor sports and outdoor leisure activities showed the association with better vision. As researchers noted, “it is not clear whether the effect of time spent outdoors is a result of the greater viewing distances or the brighter light typical of outdoor daylight hours. Brighter light could reduce the development of myopia through pupil constriction, resulting in less visual blur, or through stimulation of the release of dopamine from the retina, which is known to act as an eye growth inhibitor.“ (Abnormal eye growth is a physiological reason of shortsightedness). Whatever the mechanism is, this correlation is too strong and obvious to be ignored. Spend more time outside!
As Kathryn Rose of the University of Sydney, one of the authors of above-mentioned studies, told CNN, they “have consistently found a preventative effect for between 10-14 hours outside per week in addition to any hours spent outside during school time, while 3-6 hours per week has not been associated with any effect.”
A little deeper went a Taiwanese study having found that those living in highly urbanized areas especially benefit from outdoor activities. It also suggested that vision-related benefits of outdoor activities were not significant, though still existing, for people living in low urbanized areas.
What About Reading?
Some studies actually did find that reading as well as other forms of near work activity is associated with higher risks of myopia. Studies also found that the higher your education and IQ levels are, the more chances you are going to be shortsighted.
Some personal comments:
– the relative risks of myopia associated with reading and writing is little as compared to hereditary and environmental factors and the time spent indoor,
– the risks are found to be so inconsistent that according to some studies like the above mentioned one, “after controlling for sports and outdoor hours per week and parental myopia history, reading hours per week was no longer a statistically significant factor” of developing myopia. The study comparing Singaporean and Sydneans children effectively came to the same conclusion,
– I am having a hard time imagining that you would choose to minimize the risk for your vision at the expense of your reading.
To lessen the dangers associated with reading, try to maintain a good distance between your eyes and the paper. The more the better. Do not overdo, though: the distance should be comfortable and cause no eyestrain.
Can You Read By Dim Light?
This is a kind of gray area. No reliable epidemiological study has ever proved or ruled out that reading by poor lighting will damage your vision.
On one hand, the British Medical Journal simply called the “fearful idea that reading in dim light could ruin one’s eyesight” a myth. So did the Harvard Medical School. Those publications are very reputable, and if it were not about our children’s health, I would have stopped here. But since reputable guys gave no convincing arguments, I kept digging and found Howard C. Howland, a professor emeritus at the Cornell University, PhD in Biological Science, who worked for many years on the development of refractive state in children and youngsters.
Mr. Howland states that reading in low light can make you more nearsighted. In low light, the pupil has to open up wider, which changes where light normally hits the retina, blurs the image, and sends to the eye a signal to grow longer, so the image will hit the right place on the retina. That can cause myopia. He adds that damage is more likely to occur in young people, where eyes are still developing. I do not know about you, but, until good studies prove he is wrong, I am not going to save on power by jeopardizing my kids’ vision.
On the other hand, the British and the Harvardians made me a little bit more relaxed when I see my kids occasionally read by dim light.
All studies I perused proved no link between watching TV and physical shortsightedness. Some even show that the nonmyopic watch TV more than the myopic do. That seems to deal with IQ and education, which are negatively correlated with both watching TV and good vision.
iPads vs. Computers
If you spend enough time in front of the computer, you have likely experienced symptoms the computer vision syndrome including headaches, blurred vision, dry eyes, neck and shoulder pains. They decline after you stop working at the computer, but sometimes they may linger for a while and make your life much less comfortable. No long-term impact of the computer usage (separately from any near work activity) on your vision has been found.
The reasons of the syndrome are poor lighting, glare on the computer screen, improper viewing distances and poor seating posture, but the major contributor is dry eye meaning that your eye cannot maintain a healthy coating of tears. Unless you are reading a tearful novel, your eyes looking at the screen for some reason blink much less than when you talk or walk. In the case of the stationary computer, this is usually exacerbated by the position making you keep your eyes open wider than you normally do. Wide open eyes means that they are more exposed to drying air.
When you read from the laptop or mobile device, your position is usually more comfortable and your screen is lower, so you do not need to represent an anime character with your eyes wide open. The only issue with mobile devices is that the text can be too small, which may cause another type of eyestrain. If possible, make it larger and enjoy your reading!
Western Diet vs. Your Vision
The eye is a complicated organ accustomed to the food people had eaten for millennia before the industrial revolution. According to studies, low levels of calcium, fluoride and selenium increase risk of progressive myopia. Children consumed less protein, fat, vitamins B1, B2 and C, phosphorus, iron, and cholesterol were found to be prone to myopia. On the other hand, vitamin E slows the progression of myopia in children.
Some Western diet staples, namely refined starches such as breads and cereals, increase insulin levels, which makes the eyeball abnormally long and causes shortsightedness, suggests a study conducted by the team at the Colorado State University. The study found that as soon as recently acculturated hunter-gatherers (at Inuit and Pacific islands) adopted Western diets their rates of myopia skyrocketed from 1-2% to 50% within a couple of decades. These epidemics had usually been blamed on the increase in reading, but as the researches showed, the incidence of myopia remained low in societies that adopted Western lifestyles but not Western diets. “In the islands of Vanuatu they have eight hours of compulsory schooling a day,” says the author of the research, “yet the rate of myopia in these children is only two per cent.” The difference is that Vanuatuans eat fish, yam and coconut rather than white bread and cereals. The theory is also consistent with observations that people are more likely to develop myopia if they are overweight or have adult-onset diabetes, both of which involve elevated insulin levels.