By Dr. Mercola
Nearsightedness is incredibly common, affecting an estimated 40 percent of Americans and up to 90 percent of young adults in Asian countries.1 According to research published in 2009, rates of nearsightedness in the U.S. have risen by 66 percent since the early 1970s.2
A 2015 study estimated up to one-third of the world's population may be nearsighted by the end of the decade — that's 2.5 billion people.3 The following year, a meta-analysis of 145 studies predicted nearly half of the world will be nearsighted by the year 2050.4
Just what might be causing this rapid mass-deterioration of vision? One longstanding theory was that excessive reading at close distance (particularly in poor lighting) could lead to nearsightedness by altering growth and shape of the eyeball.
As computers and smartphones grew in popularity, squinting at computer screens has received a majority of the blame.
The "bookworm theory" first emerged centuries ago when German astronomer Johannes Kepler claimed his studies caused his nearsightedness. It seemed plausible enough, especially as rates of the condition skyrocketed in regions like Shanghai, where teens spend about 14 hours a week on homework.5
However, once investigated further, the bookwork theory came up short. When researchers looked at number of books read per week or hours spent using a computer among children in Singapore, no significant link to nearsightedness was actually found.6
According to the authors, "neither reading nor parental myopia history were associated with values for anterior chamber depth, corneal curvature or lens thickness."
They went on to suggest that "corneal curvature and lens thickness may be subject to unrelated postnatal growth control mechanisms." Interestingly, a number of studies now suggest one of these control mechanisms might be sun exposure.
What Causes Nearsightedness?
Nearsightedness (myopia), is a vision problem in which close objects appear clear but distant objects are blurry. This condition is thought to be caused by refractive errors in your eye. Refraction is the bending of light as it passes through one object to another.
When light rays are refracted through your eye's cornea and lens, they become focused on the retina, which then converts the light into messages sent through the optic nerve to your brain, which then interprets the messages into images.
Refractive errors occur when the shape of your eye prevents light from focusing properly on your retina. This can occur by changes in the shape of your eye, such as the length of your eyeball or shape of your cornea, and/or changes in your lens due to aging. But what exactly is responsible for these changes?
Two studies, the first published in 20077 and the second in 2008,8 found that rates of nearsightedness in children appeared to be closely linked to the amount of time spent outdoors. The greater the number of hours spent playing outside, the lower the risk of nearsightedness.
In other words, keeping kids indoors and/or instilling a fear of sun exposure (for skin cancer reasons) may be at the heart of the world's growing myopia problem. Remarkably, according to a British survey, 75 percent of children in the U.K. spend less time outdoors than prison inmates!9
Sun Exposure Needed for Optimal Vision
Most recently, British researchers investigated the connection between the time spent outdoors and vision among the elderly.10,11,12 As reported by The New York Times:13
"Researchers … gave vision exams to more than 3,100 older European men and women and interviewed them at length about their education, careers and how often they remembered being outside during various stages of their lives.
This biographical information was then cross-referenced with historical data about sunlight, originally compiled for research on skin cancer and other conditions.
Strong correlations were found between current eyesight and volunteers' lifetime exposure to sunlight, above all UVB radiation …
Those who had gotten the most sun, particularly between the ages of 14 and 19, were about 25 percent less likely to have developed myopia by middle age. Exposure to sunlight up to the age of 30 also conferred a protective benefit."
Importantly, this relationship remained even after controlling for time spent reading, showing that gazing at screens or books is more or less unrelated to myopia, while sun exposure appears to be a primary factor. The question is how does light actually affect the structure of the eye?
Since blood tests were drawn, they could conclude that the reduction in myopia was NOT related to vitamin D.
As noted by lead author Katie Williams, a clinical research fellow at King's College London, "People with myopia have long eyeballs, so there must be something in sunlight that affects how the eye grows, especially in childhood."
On a side note, they did find a correlation between myopia and lutein concentrations in the blood. Lutein, found in egg yolks and leafy greens, is known for its protective influence on eyesight and the prevention of age-related macular degeneration (AMD).
Here, those with the highest levels of lutein had a 43 percent lower risk of myopia compared to those with the lowest levels.
As for how sunlight affects eye development, animal research14 published in 2010 suggests bright light exposure helps protect your eyes by stimulating the growth of key elements in the retina, and by increasing the functioning of antioxidants in the eye.
An even earlier study, published in 2008,15 showed that infrared light — found in sunlight — activates cytochrome oxidase, a photosenstive molecule located in your mitochondria. Activating this molecule led to increased cellular activity in the retina, and an increase in antioxidant properties.
Meanwhile, research has shown that cytochrome C oxidase deficiency is a factor in age-related macular degeneration (AMD), which is a primary cause of blindness.16
Outdoor Playtime May Significantly Reduce Your Child's Risk of Myopia
Another recent study,17 this one from Canada, found that spending just one more hour outdoors each week may decrease a child's risk of myopia by 14 percent.
To reach this conclusion, the scientists conducted eye exams on 166 first through eighth grade students. In grade 1, 6 percent had myopia. By age 13, that percentage skyrocketed to 29 percent.
The parents were then interviewed to ascertain the amount of time each child typically spent outdoors each week. Again, this turned out to be a major predictive factor for myopia.
Previous research by Ian Morgan, Ph.D., of the Australian National University suggests that exposure to light levels of at least 10,000 lux for three hours a day may protect children from nearsightedness.18
This is the amount of light you would be exposed to on a bright summer day. An indoor classroom, by comparison, would only provide about 500 lux.
Yet another study showed that by encouraging Taiwanese children at one school to spend their daily 80-minute break outdoors, rates of myopia dropped to 8 percent compared to 18 percent at another nearby school.19
According to optometrist Donald Mutti, Ph.D., children who are genetically predisposed to nearsightedness are 300 percent less likely to need glasses if they spend at least 14 hours a week outdoors.20
In Singapore, public health campaigns have even been introduced encouraging children to get outdoors to prevent nearsightedness. The slogan? "Keep myopia away, go outdoors and play!"21
Indeed, it seems clear that the more time children spend outdoors, the lower their risk of nearsightedness becomes, and the more we learn about the influence of sunlight on human biology and health, the more this connection makes sense.
Bright Light Is Important for Overall Health
When full-spectrum light (i.e. sunlight) enters your eyes, it not only goes to your visual centers enabling you to see, it also goes to your brain's hypothalamus where it impacts your entire body. For starters, your hypothalamus controls body temperature, hunger and thirst, water balance and blood pressure. It also controls your body's master gland, the pituitary, which secretes many essential hormones, including those that influence your mood.
Your "body clock" is also housed in tiny centers located in the hypothalamus, controlling your body's circadian rhythm. This light-sensitive rhythm is dependent on natural cycles of light and darkness, to function optimally. Consequently, anything that disrupts these rhythms, like inadequate sunlight exposure to your body (including your eyes) or chronic exposure to unopposed blue light from artificial lights, has a far-reaching impact on your body's ability to function.
Some experts even believe that "malillumination" to light is what malnutrition is to food. The best way to get exposure to healthy full-spectrum light is to do it the way nature intended, by going outside, exposing your bare skin — and "bare" eyes — to the sun on a regular basis.
Sunlight Is Also Important for the Prevention of Blindness
As explained by Dr. Alexander Wunsch, a world class expert on photobiology, full-spectrum light such as sunlight is also a significant factor in blindness and optimal health. More specifically, the widespread use of energy efficient light-emitting diodes (LEDs) may be setting the stage for an avalanche of AMD in coming decades. The reason for this is because LED lighting has no near-infrared light, emitting primarily blue light, and this has biological consequences that impair your vision over time.
The heat generated by incandescent light bulbs (which is infrared radiation) is actually highly beneficial to your health, and hence worth the extra energy cost. In your eyes, the near-infrared light range primes the cells in your retina for repair and regeneration from the damage blue light causes in the retina. Meanwhile, LEDs, which have virtually no infrared and an excess of blue light, generates reactive oxygen species (ROS) instead.
You do need some blue light, especially in the morning for melatonin production, but you need it to be balanced with the healing and repairing red and near-infrared frequencies, like it is in natural sunlight.
This explains why LEDs are so harmful for your eyes and overall health. The same applies to electronic screens such as TVs, computers, tablets and smartphones. They all emit primarily blue light, and the excess ROS generation may have a great deal to do with the deterioration of vision. The blue light is also deleterious for your circadian rhythm. Electronic screens should be avoided at least a couple of hours before bedtime to avoid suppressing melatonin production.
Interestingly, research22 shows that infrared light exposure may even reverse AMD. Even more remarkable, infrared light over the thyroid area has been shown to reverse hypothyroidism! It seems the more we learn about light, the more crucial it appears to be for biological functioning and optimal health. It's important to realize that light is actually a significant part of the equation for biological energy production, specifically at the mitochondrial ATP level. Hence it affects your overall health, not just your eyes.
Importantly, full-spectrum light — light that includes the near-infrared spectrum (750 to 1400 nanometers [nm]) — generates structured water in your cells, which plays an important role in biological functioning, including your cardiovascular function. To learn more about this, please see my interview with Dr. Thomas Cowan. I also discuss this in my recent article, "Water Supports Health in Ways You May Never Have Suspected."
In summary, to protect your eyesight and overall health, be sure to get bright sun exposure especially in the early part of the day and, when indoors, use clear (not white-coated) incandescent light bulbs in areas where you spend most of your time. Candles can also be used, especially at night, and are even better and healthier than incandescents.
I also believe it is imperative to use blue-blocking glasses after sunset, unless the only light exposure you have is candles. Once you have your glasses on, it doesn't matter what kind of light bulbs you use.
Candles — Another Healthy Light Alternative
Candles are even a better light source than incandescent bulbs, as there is no electricity involved and is the light our ancestors have used for many millennia, so our bodies are already adapted to it. The only problem is that you need to be careful about using just any old candle, as most are toxic.
As you may or may not know, many candles available today are riddled with toxins, especially paraffin candles. Did you know that paraffin is a petroleum by-product created when crude oil is refined into gasoline? Further, a number of known carcinogens and toxins are added to the paraffin to increase burn stability, not including the potential for lead added to wicks, and soot invading your lungs.
To complicate matters, a lot of candles, both paraffin and soy, are corrupted with toxic dyes and fragrances; some soy candles are only partially soy with many other additives and/or use GMO soy. The candles I use are non-GMO soy, which is clean burning without harmful fumes or soot, is grown in the U.S. and is both sustainable and renewable. They're also completely free of dyes. The soy in these candles is not tested on animals and is free of herbicides and pesticides.
It's also kosher, 100 percent natural and biodegradable. The fragrances are body-safe, phthalate- and paraben-free and contain no California prop 65 ingredients. You can search online for healthy candles, but if you like, you can use the ones I found at www.circleoflifefarms.com. This is not an affiliate link and I earn no commissions on these candles; I just thought you might benefit from the ones I now use in my home.
How to Make Digital Screens Healthier
When it comes to computer screens, it is important to reduce the correlated color temperature down to 2,700 Kelvin (K) — even during the day, not just at night. It's even better to set it below 2000K or even 1000K. Many use f.lux to do this, but I have a great surprise for you as I have found a FAR better alternative that was created by Daniel Georgiev, a 22-year-old Bulgarian programmer that Ben Greenfield introduced to me.
He was using F.lux but became frustrated with the controls. He attempted to contact the F.lux programmers but they never got back to him, so he created a massively superior alternative called Iris. It is free, but you'll want to pay the $2 and reward him with the donation. You can purchase the $2 Iris mini software here.
Iris is better because it has three levels of blue blocking below f.lux: dim incandescent, candle and ember. I have been using ember after sunset and measured the spectrum and it blocked nearly all light below 550 nm, which is spectacular, as you can see in the image below when I measured it on my monitor in the ember setting. When I measured the f.lux at its lowest setting of incandescent it showed loads of blue light coming through, as you can clearly see in the second image below.
So, if you are serious about protecting your vision you will abandon f.lux software and switch to Iris. I have been using it for about three months now, and even though I have very good vision at the age of 62 and don't require reading glasses, my visual acuity seems to have dramatically increased. I believe this is because I am not exposing my retina to the damaging effects of blue light after sunset.
Diet Also Plays a Role in Nearsightedness and AMD
When it comes to protecting your vision, your diet also plays an important role, as your eyes need certain nutrients in order to function properly. Dark leafy greens are particularly important, as they're rich in carotenoids like zeaxanthin and lutein. Zeaxanthin is an antioxidant carotenoid found in your retina, but it cannot be made by your body, so you must get it from your diet.
Other important nutrients include animal-based omega-3 fats, vitamins A, C and E, and zinc.23 AMD, as well as cataracts, are largely driven by free radical damage, and may in many cases be largely preventable through antioxidant-rich foods such as:
Your diet can also influence your risk for nearsightedness. According to Loren Cordain, Ph.D., an evolutionary biologist at the Colorado State University in Fort Collins, elevated insulin levels affect the development of your eyeball, making it abnormally long, thereby causing near-sightedness.24
Cordain found that when hunter-gatherer societies change their lifestyles and introduce grains and carbohydrates, they rapidly develop (within a single generation) myopia rates that equal or exceed those in western societies.
The reason for this is because high insulin levels from excess carbohydrates can increase insulin resistance and disturb the delicate choreography that normally coordinates eyeball lengthening and lens growth. And if the eyeball grows too long, the lens can no longer flatten itself enough to focus a sharp image on the retina.
This theory is also consistent with observations that you're more likely to develop myopia if you are overweight or have adult-onset diabetes, both of which involve elevated insulin levels. Following my nutrition plan will help normalize your insulin level by reducing, or eliminating, excess sugar and processed grains from your diet. To learn more about which foods can help safeguard your vision, please see my previous articles, "Eat Right to Protect Your Eyesight," and "The Best Foods for Healthy Eyes."
How the Bates Method May Improve Your Nearsightedness
If you're already nearsighted, all is not lost. According to Greg Marsh, a certified natural vision coach, clear vision is achievable even if you're already wearing strong corrective lenses. The method Greg teaches was initially conceived by Dr. William H. Bates, over 100 years ago.
A board-certified ophthalmologist at the top of his field, Bates taught his method to many, and it was so effective that it ended up being banned in New York after the optometrists lobbied the local politicians. So how does the Bates Method work? Marsh explains:
"Basically, there are six muscles on the outside of your eye, and they're moving it around ... Ideally, these muscles are easily following visual interests ... The problem is — it could be for emotional reasons, physical stress or whatever — you start to strain. Once you start to strain, your vision starts to go."
The action of straining essentially squeezes your eyeballs, contorting them. This makes your vision blurry, as it alters where the field of vision "lands" on your retina. Now you have three basic choices:
- Find out what's stressing you, making you strain. Let it go, relax and get your vision back. Bates developed ingenious tools for doing just that
- Get laser in-situ keratomileusis (LASIK), which permanently alters your focal length
- Get corrective lenses. The problem with corrective lenses is that now you're creating permanent strain
The Bates Method isn't really an exercise; it's more of a mental approach. It's also worth noting that the Bates Method is clearly NOT a medical approach. You still need to see your regular eye doctor for checkups. One of the most famous Bates Method techniques is palming. Look around and notice the level of clarity of your vision at present.
Then, simply place the center of your palms over your eyes. Relax your shoulders. You may want to lean forward onto a table or a stack of pillows, to facilitate relaxation. Relax like this for at least two minutes. Then remove your hands, open your eyes and notice whether anything looks clearer. Usually, it will.
The Bates Method is really quite simple, yet it requires patience and a certain amount of finesse. Remember, the goal is not to "train" or exercise your eyes to make them stronger. The goal is to relax them. Greg's program provides thorough instructions that can help you get there. Also, remember that your mindset is important.
Bates was also a proponent of sunning the eyes to help correct vision problems,25 and recent research suggests he was on the right track 100 years ago. It just goes to show that, as humans, we cannot extract ourselves too far from the natural world.
Indeed, we depend on the natural order of things to thrive, and that includes being exposed to sunlight during the daytime, and avoiding light exposure once the sun has set. Altering this natural order has consequences for our health, including but certainly not limited to our vision.