Tag Archives: myopia

Credit: Pixabay.

To avoid shortsightedness, children should spend more time outdoors

Credit: Pixabay.

Credit: Pixabay.

Shortsightedness, or myopia, is a very common vision problem that can usually be corrected with glasses or contact lenses. Myopic individuals see things up close clearly but objects farther away are out of focus or blurry. Although the condition does not significantly affect an individual’s quality of life (provided glasses are used), what’s worrisome is the high incidence of shortsightedness among people today.

The most important factor for shortsightedness is genetics, but a new study has identified more environmental factors that might explain the steep rise in myopia around the developed world.

Playing outside seems to be the most important thing a child can do to avoid myopia later in life

According to the most recent estimates, around 90% of teenagers and young adults in China have shortsightedness. According to a recent study, shortsightedness among Chinese schoolchildren rose by more than 50 percent between grade one and seven.

Genes play a major role in whether or not a person will develop the condition. However, the astonishing rate with which myopia is affecting school children around the world is much too steep to be explained by heredity alone — genes just don’t change that fast.

It follows that environmental factors are at play, and a new study published in the British Journal of Ophthalmology has both confirmed some established factors and also uncovered new ones.

The researchers at King’s College London used data from the UK-based Twins Early Development Study, which involved 1,991 twins recruited at birth between the years 1994 and 1996. Each individual’s development, behavior, education, and genetics were tracked, allowing the researchers to trace associations between myopia and the participants’ environment. 

According to the results, every extra hour a child spent on computer games each week increased the chance of them having myopia by 3%. This can be explained by the close proximity to screens and time spent indoors as sunlight exposure is critical to good eyesight development. For instance, a study published earlier by a research team at Australia’s Brien Holden Vision Institute found that myopia progression in Chinese children is up to 40% slower in summer, when they are exposed to more sunlight, than in winter.

Speaking of which, the King’s College study found that children born in the summer had almost twice the risk of developing shortsightedness later in life. The authors explain that this may be due to the fact that these children start school earlier in life.

What was surprising to learn was that  children born by fertility treatment had a 37% reduced risk of myopia by the time they were in their mid-teens. Another interesting new factor identified by the researchers was that for every higher level of education the mother had, the risk of her child having myopia rose by 33%. This latter factor may be pinned to the link between myopia and intelligence or to the fact that educated mother may encourage their children to study harder indoors.

“Given the rise in myopia prevalence, likely due to changing environmental pressures in childhood, further studies of this and other cohorts are warranted, in conjunction with genetic data, to continue efforts to produce predictive models that can ascertain who should be targeted for treatments to reduce the future burden of this condition,” the authors concluded.

Why 90% of China’s youth suffer from near-sightedness

To say that Asia is having an eye problem is an understatement. It seems almost too surreal to be true, but almost 9 in 10 Chinese youngsters suffer from myopia, also known as near-sightedness.

Genetics

For a very long time, there was a scientific consensus that myopia was caused by genetics. Studies in the 60s showed a clear connection between genetics and the eye condition, suggesting a strong DNA susceptibility. But it quickly became evident that genes weren’t telling the full story. In 1969, that was shown quite clearly in an Inuit study. In an isolated community, just 2 out of 131 had myopic eyes. But more than half of their children and grandchildren had the condition. Similar studies yielded similar results. Obviously, this was too fast to be a genetic change and so there must have been another reason – lifestyle being the most logical one.

Globally, near-sightedness is the most common eye problem and is estimated to affect 1.5 billion people (22% of the population) but rates vary drastically from one part of the world to the other. Among children, it affects 1.2% of rural Nepalese, 4% of South Africans, 12% of Americans, and 37% in some large Chinese cities.

Myopia in Asia

Myopia or near-sightedness is defined as blurred vision beyond 2m (6.6ft). It is often caused by an elongation of the eyeball that happens when people are young. It is a condition of the eye where light focuses in front, instead of on the retina so objects close to the eye appear normal, whereas objects which are farther away seem blurry.

Diagram of Myopia in the human eye, via National Eye Institute.

The condition is more than an inconvenience. Even though glasses and surgery help, they don’t solve the actual underlying problem, and especially in Eastern Asia, hospitals are bursting with young people suffering from harsh forms of myopia. Sixty years ago, 10–20% of the Chinese population was short-sighted. Today, 90% of all teenagers and young adults are. In Korea’s capital Seoul, a stunning 96.5% of 19-year-old men are short-sighted. Other parts of the world have seen similar trends, but not to this extent and severity. So what changed from past generations, and what is different in China and eastern Asia, compared to Europe or North America?

The usual suspects

The recent increase in incidence has triggered a surge of studies trying to see what’s causing this. The first suspected culprit was reading. The idea seemed to make sense. Reading makes your eyes tired, everyone knows that. Even 400 years ago, German astronomer and optics expert Johannes Kepler blamed his own short-sightedness on all his study. That may have been true, and the idea picked up. By the late 1800s, doctors were recommending headrests to keep a safe distance from books when reading. In modern times, a correlation between studying and myopia has also been reported several times, so that seemed to be the end of it. But it wasn’t.

In the early 2000s, several studies looked at reading behaviors in more detail. They wanted to see how time spent reading influenced myopia – and they found that it didn’t. No matter how they looked at it, reading simply didn’t seem to make people’s eyes worse. Then screens came under scrutiny.

It is well known that computer and phone screen can cause temporary eye problems, but whether or not they can actually lead to myopia has surprisingly not been shown. But something else seemed to fit the data perfectly and explain the pattern: time spent outside.

 

Kids who spent less time outside were much more likely to develop myopia. In 2007, Donald Mutti and his colleagues at the Ohio State University College of Optometry in Columbus reported an unexpected but very strong correlation between time spent outside and near-sightedness. A few years later, another study in Australia came up with the same results: children who spend less time outside were more likely to develop myopia. The final straw was when biologists compared Singaporeans living in Singapore to those living in Australia. They found that 29 percent of the Singaporean students had myopia compared with just 3 percent in Sydney. The main correlation was once again, time spent outside.

“The big difference was the Chinese children in Australia were outdoors a lot more than their matched peers in Singapore,” says Ian Morgan, a retired biologist at Australian National University, who coauthored the 2008 study. “This was the only thing that fit with the huge difference in prevalence.”

Light and sight

Of course, correlation does not imply causation, and what science needs is a mechanism. There are several hypotheses which attempt to explain how this happens. The best one seems to be something called the light-dopamine hypothesis, which states that light stimulates the release of dopamine in the retina, thus ensuring that the retina maintains the correct shape. A study on chicks seems to support this idea. Retinal dopamine is produced based on a day-night cycle, thus telling the eye to switch from rod-based, nighttime vision to cone-based, daytime vision. Thus spending less time outside and more time inside (subjected to artificial light) disrupts this cycle and the good functioning of the eye.

Playing outside might help protect kids’ eyes.

So what’s a good time to spend outside? Ian Morgan, a myopia researcher at the Australian National University in Canberra, estimates that children need to spend around three hours per day. He is currently working on refining his studies and finding a more accurate value. In the meantime, more and more kids are suffering from near-sightedness.

In Asia, this problem was exacerbated by a few other factors, including a fear of glasses.

“Parents, teachers and even some rural doctors think wearing glasses will harm kids’ eyes,” says Dr. Nathan Congdon, an ophthalmologist at Zhongshan Ophthalmic Center at Sun Yat-sen University in the southern city of Guangzhou, who led the new study. “In rural China, only about one-sixth of the kids who need glasses actually have them.”

Needless to say, that’s really not the case. Glasses have been shown to improve academic performance and not do any damage to the eye, as Congdon himself studies. He hopes to be able to convince people in Asia – and everywhere else – that this is the case. Hopefully, he will.

 

Half the world will need glasses by 2050

Nearly half the world’s population, close to some 5 billion people, will develop myopia by 2050 according to a study recently published in the journal Ophthalmology. The paper also estimates that one-fifth of these people will have a significantly increased risk of becoming permanently blind from the condition if recent trends continue.

"Can you come a bit closer? I can't see you yet." Image via flikr @ Paul Stevenson.

“Can you come a bit closer? I can’t see you yet.”
Image via flikr @ Paul Stevenson.

The number of myopia cases is rapidly rising across the globe, making it one of the most common sight-impairment conditions of the modern world. This increase is attributed to “environmental factors (nurture), principally lifestyle changes resulting from a combination of decreased time outdoors and increased near work activities, among other factors,” according to a new study from Brien Holden Vision Institute, University of New South Wales Australia and Singapore Eye Research Institute.

Even worse, if the current trends continue, the paper warns that we’ll see a seven-fold increase in cases from 2000 to 2050. Myopia will also become one of the leading causes of permanent blindness by that date.

But why? Short-sightedness has always been around but never at the scale this study predicts.

It’s mostly due to the way we use our eyes today. For most purposes, our eyes are good at spotting far away objects, but they have been mostly relegated to short distance duty nowadays. Our daily activities involve a lot of “near work activities,” such as using a computer, scrolling on a smartphone or reading. Constantly keeping focus on a short distance leaves the crystalline lens in our eyes set on them, in a sense, and unable to effectively focus on objects farther away.

The authors point out that this has become a major public health issue, one that we’ll have to tackle — preferably sooner rather than later. They suggest that planning for comprehensive eye care services is needed to manage the rapid increase in high myopes (a five-fold increase from 2000), along with the development of treatments to control the progression of myopia and prevent people from becoming highly myopic.

“We also need to ensure our children receive a regular eye examination from an optometrist or ophthalmologist, preferably each year, so that preventative strategies can be employed if they are at risk,” said co-author Professor Kovin Naidoo, CEO of Brien Holden Vision Institute. “These strategies may include increased time outdoors and reduced time spent on near based activities including electronic devices that require constant focussing up close.

“Furthermore there are other options such as specially designed spectacle lenses and contact lenses or drug interventions but increased investment in research is needed to improve the efficacy and access of such interventions.”

Yea so….I’d say investing in the glasses industry will probably net you a nice return in a few years.

But there is an upside to this paper. Don’t want myopia? Drop your laptop and spend some time in the park. Put your smartphone in your pocket and look at the city as you walk to work or school. You might even end up having fun.

The full paper, titled “Global Prevalence of Myopia and High Myopia and Temporal Trends from 2000 through 2050” is available online in the journal Ophthalmology here.

 

myopia children playing

Play outside, kids! Sunlight reduces chances of myopia in children

You often hear people complaining that kids don’t play outside anymore – instead just hanging in the house all day long, playing on the computer (tablet/xbox/whatever). This is a pretty big problem, because there is a myriad of advantages to playing outside; this study has added yet another advantage to that list: playing outside reduces the risk of myopia in kids.

myopia children playing

Playing outside seems to reduce the risk of myopia in children. Image via PicturesNew.

For quite a long time, it was thought that playing in front of the computer instead of playing outside can damage your eyes; this has been proven wrong, but now, research has shown that if you play outside as a kid, you have better chances of not developing myopia, though it’s not clear why.

“We don’t really know what makes outdoor time so special,” said Donald Mutti, the lead researcher of the study from Ohio State University College of Optometry, in a press release. “If we knew, we could change how we approach myopia.”

Myopia (or short-sightedness) is a condition in which the light that comes in the eye does not directly focus on the retina but in front of it, causing the image that one sees when looking at a distant object to be out of focus. The causes of myopia are still elusive and to make things even more interesting, a number of studies have shown the incidence of myopia increases with level of education. Many studies have shown a correlation between myopia and a higher intelligence quotient (IQ). Myopia is also highly hereditary.

But whatever the cause may be, sunlight seems to work against the condition. Previous research showed that UVB light, (invisible ultraviolet B rays), plays a role in the cellular production of vitamin D, which helps the eyes focus light on the retina. But study authors believe there is another reason why playing outside fights against myopia.

“Between the ages of five and nine, a child’s eye is still growing,” said Mutti. “Sometimes this growth causes the distance between the lens and the retina to lengthen, leading to nearsightedness. We think these different types of outdoor light may help preserve the proper shape and length of the eye during that growth period.”

The pupil also seems to play a role here – when exposed to more light (like in the outdoors), the pupil dilates. But not all light comes equally, and natural sunlight seems to yield better effects.

“Our initial research suggests that the pupil responds more if these cells have been exposed to a lot of sunlight in the previous few days.”

The key threshold seems to be 14 hours (or more) a week; even kids who are genetically susceptible to myopia are three times less likely to need glasses provided they are playing in the sun for at least 14 hours a week.

There are many more questions to be answered, but ultimately, the takeaway message is that kids should play outside – if not for their own development and fun, then at least for their eyes.

“I think the research we are doing now will help us finally solve the mystery of the outdoor effect, and maybe help some people avoid a lifetime of wearing glasses,” he said. “In the meantime, I tell parents don’t worry about reading, get their kids outside, but don’t forget … sunscreen.”

Journal Reference: Lisa A. Jones-Jordan, Loraine T. Sinnott, Nicholas D. Graham, Susan A. Cotter, Robert N. Kleinstein, Ruth E. Manny, Donald O. Mutti, J. Daniel Twelker, Karla Zadnik, for the CLEERE Study Group. The Contributions of Near Work and Outdoor Activity to the Correlation Between Siblings in the Collaborative Longitudinal Evaluation of Ethnicity and Refractive Error (CLEERE) Study. Published online before print September 9, 2014, doi: 10.1167/iovs.14-14640

nearsightedness-and-school

Link found between nearsightedness and years spent in school

nearsightedness-and-school

Photo: Igor Mojzes – Fotolia.com

A common stereotype is that people who wear glasses are labeled as nerds, but sooner than later most people from the developed world will end up wearing glasses, if the current trend continues. There are many reasons why more and more suffer from nearsightedness, ranging from urbanization, spending more time indoors and in front of the computer and so on. A new study published in this month’s Ophthalmology journal eyes in on one particular cause for increased rate of nearsightedness – education. Namely, the German team of researchers involved in the study identified that attaining a higher level of education and spending more years in school are two factors associated with a greater prevalence and severity of nearsightedness, or myopia. This is the first study of its kind to demonstrate that environmental factors may outweigh genetics in the development of myopia.

An ever common affliction

If left untreated, myopia can intensify and develop into more severe forms of visual impairments, increasing the risk of developing retinal detachment, myopic macular degeneration, premature cataracts and glaucoma. In the US alone, some 42% of the population is currently affected by nearsightedness, while Asian countries report increasing myopia rates of up to 80 percent. This surge and rapid development rate suggests that environmental factors play a significant role, one that may be more important than genetics.

Researchers at the University Medical Center in Mainz, Germany looked to find if there was any association between myopia development and education. To this end, they examined some 4,658 Germans ages 35 to 74. Their analysis suggests that myopia prevalence increases with education as follows:

  • 24 percent with no high school education or other training were nearsighted
  • 35 percent of high school graduates and vocational school graduates were nearsighted
  • 53 percent of university graduates were nearsighted

Delving deeper, the researchers found that every year of formal education caused severer nearsightedness. This is the first population-based study to find that environmental factors are more important in the development of myopia than genetics, after the researchers also looked at 45 genetic markers, but found it a much weaker factor in the degree of nearsightedness compared to education level.

So, what can people do to avoid becoming nearsighted or worsening their already present condition? The simplest solution is going outside more, according to the researchers.

“Since students appear to be at a higher risk of nearsightedness, it makes sense to encourage them to spend more time outdoors as a precaution,” said Alireza Mirshahi, M.D., lead author of the study.