Seeing the Light: Why Sun Exposure May Be Good for Your Eyes
Having immersed myself in all things Primal for so long, I find myself viewing nearly everything through the prism of human evolution. Is this food, activity, environmental stimulus, or social more an evolutionary novelty? If so, might it possibly conflict with or impede our pursuit of good health? Is it benign? An improvement, even?
Grok logic will only get you so far. It’ll give you a nudge in the right direction – that is, headed straight to honest inquiry and further research – but it’s not enough. You shouldn’t rest on your laurels if Grok logic suggests what you’re doing is right, and you shouldn’t make big changes just because Grok logic suggests you’re doing something wrong. Instead, use those insights to generate hypotheses, then try to explore them. Research, read, ask more questions. At least, that’s what I try to do. It’s awfully tempting to just go with conjecture (especially if it turns out to be right on a fairly regular basis!).
That little preamble was just my way of setting up yet another question with roots in evolutionary conjecture: does the avoidance of sunlight via indoor living, sunglasses, and general heliophobia have an impact on eyesight, and more specifically nearsightnedness? Going purely by Grok logic and what we know about sunlight’s interaction with other aspects of our health, I think it’s a reasonable question. To whit:
Sunlight and skin – Sunlight exposure is required for vitamin D synthesis. When UVB hits our exposed skin, vitamin D is synthesized and distributed throughout our body. Vitamin D is an essential pro-hormone, necessary for musculoskeletal health, immune system robustness, as well as protection from heart disease and cancer.
Sunlight and circadian rhythm – We need exposure to light at certain times of the day in order to regulate our circadian rhythms. Without daytime/morning light, or with too much evening light, our internal clocks – and general health – go awry.
Given those two extremely basic, widely-accepted interactions between sunlight and our bodies, coupled with the fact that the eye’s express function is to interact directly with light, I think Grok logic regarding the sun and our eye health might be onto something. But we can’t be sure, remember, without confirming through other sources.
So let’s look into those other sources.
I’m sure you’ve heard of myopia. You may have it yourself or know someone who does. In case you don’t, myopia is nearsightedness, which is characterized by blurry vision when looking at distant objects. If it weren’t so easily countered with prescription eyeglasses, myopia would probably be classified as a public health epidemic. It’s that common, and it’s getting worse.
In fact, the latest statistics indicate that 41.6% of Americans aged 12-54 suffer from myopia, way up from 25% in the early 1970s. That’s an awfully big percentage of the tribe that can’t throw a spear, shoot an arrow, spot prey, or see the enemy coming from afar. That’s a ton of squinters who require assistance. In other words, if myopia were just an unfortunate part of growing old (to the ripe old age of 12!), we probably wouldn’t have made it this long.
No, there’s probably an environmental component to the rise of myopia. Genetics could play a part in determining susceptibility to myopia, and probably do, but an environmental factor is likely to be a trigger for the “myopia gene’s” expression. Could sunlight be just such an environmental factor?
Kathryn Rose, a visual disorder researcher, thinks so. First, she points to the weak or inconsistent epidemiology that attempts to link time spent on the computer, watching television, reading, and studying to the development of myopia, instead suggesting that the real problem is lack of sunlight. In cases where digital media usage or inside work appears to be associated with myopia, Rose thinks it’s actually a measure of displaced outdoor time.
Then she points toward the epidemiology exploring the link between time spent outdoors and myopia prevention, which is much stronger. Let’s take a look at a few studies:
In Chinese school children, myopia progression was inversely correlated with outdoor activity.
Near work (studying, reading) did not correlate with myopia progression, but American kids who played fewer sports outdoors had more myopia.
In Taiwanese rural children, outdoor activities might be “an important protecting factor for myopia.”
In teens from Singapore, outdoor activity appeared to protect against myopia progression.
Parental myopia status interacts with risk, too, though. In one study, kids with two myopic parents were at the greatest risk of developing myopia themselves, more so if they did not engage in outdoor sports. Kids with no myopic parents and who played a lot of sports outside had the lowest risk. Genetic predisposition expressed by an environmental trigger, anyone?
Of course, any good Primal thinker knows that epidemiology, like Grok logic, only goes so far. It’s certainly interesting, and it can inspire new avenues of inquiry, but science cannot live on epidemiology alone. You need something else to look into, like perhaps a physiological mechanism. Rose’s proposed mechanism was retinal dopamine, a “known stimulator of eye growth whose release is stimulated by light.” A lack of retinal dopamine – from avoiding the outdoors – means excessive eye growth. This is bad, for the eye is a delicate, extremely complex structure with many components, and a lot can go wrong if those components grow faster and bigger than they’re supposed to grow. Like the progression of myopia, which is characterized by excessive eye growth.
But wait – isn’t excessive amounts of light one of the big issues with modern living? Even if we stay indoors most of the day working, browsing, or watching TV, we’re still parked in front of a screen beaming light into our eyes and we’re still immersed in artificial overhead lighting. If all that light is enough to disrupt our circadian rhythms and ruin our sleep patterns, why isn’t it enough to stimulate retinal dopamine release?
It’s the magnitude. Try looking up at the sun in the afternoon. I mean really give it a good, long look. You can’t do it (in fact, that is definitely bad for your eyesight!) for more than a second or two, tops. If you squint, you might make three. Now try the same with an illuminated lightbulb. It’s easy and nearly painless. It doesn’t compare. To quantify the massive gulf between sunlight and artificial light, let’s look at another study. Researchers trying to study the link between light exposure and myopia exposed chicks to various amounts of light. Normal laboratory lighting was 500 lux, “intense” laboratory lighting was 15,000 lux, and sunlight was 30,000 lux. Only intense lab light and sunlight were able to retard the development of myopia, while normal lab lighting – which is still quite bright and very similar to standard office lighting conditions – did not adequately protect. Oh, and good news for you sunglass wearers: the chicks who were continuously exposed to bright lighting while wearing “translucent diffusers” also showed resistance to eye lengthening and myopia.
To get an idea of how many lux you can expect to “get” in various situations, check out the Wikipedia article on the subject. Prepare to marvel at the insane brightness of the outdoors and the comparatively piddling illumination found indoors. Note that direct sunlight is ridiculously bright (up to 130,000 lux), while just being outside in “full daylight” will provide plenty of light for your retinal dopamine labs. No need to stare at the sun or avoid dark forests. Just be outdoors and the sun will take care of the rest. If you can see stuff, that means light is getting to your eyes, it’s from the sun (and thus bright enough) and you’re good to go.
Of course, us oldsters might be too far gone for sunlight to have an effect on nearsightedness. Myopia develops early (hence the inclusion of 12 year-olds in myopia statistics), so it’s absolutely crucial that kids get plenty of time outdoors. I’d say “as much as possible,” but if you want a specific number, Kathryn Rose suggests between 10-14 hours a week as a bare minimum. Barring that, I suppose you could blast your toddler in the face with a halogen bulb every couple hours. No, but really: let those kids get outside, get dirty, play with bugs, climb stuff, and get some sun. Although the chick study showed that sunglasses may not be problematic, I don’t think kids need ‘em, and they might still interfere with normal eye development. They’d just fall off, anyway, unless you hooked the kid up with some Horace Grant-style goggles.
Given all that, I think it’s safe to say that sunlight exposure probably plays a role in the development of nearsightedness. It’s not the only player – physiology is rarely that simple – but it appears to be a major factor. Anyway, I think we’ll have a better idea in the coming years. My Pubmed trawling pulled up a ton of very recent studies on the subject, all in the last few years or so, so we can probably expect more definitive answers in the near future.
Are you nearsighted? Did you play a lot outdoors as a kid? What’s your family history of myopia – do your parents have it too? Let me know in the comment section!
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Posted By: Mark Sisson
An issue like this gets pretty complicated. On the one hand if the statistics are truly accurate, then there is obviously some social factor at large which is contributing to the general increase in myopia. Does this effect certain geographic regions however? It would be tough to really make the conjecture that people are spending more time in-doors that lets say 50 years ago.
Personally I developed myopia when I was twelve, spend almost all my time outside, my parents are big nature buffs, and that obviously didnt make a difference in my vision impairments.
There are so many factors that effect individuals which could lead to a greater chance of myopia. Spending more time outside may in fact be better. These kind of tests should be recreated in different regions however, such as iceland and nordic countries where they go through months of continual light and continual dark.
I grew up in farm country in NZ and spent a huge amount of time outdoors playing in the dirt, but my eyes suck
But it runs in the family and we had poor nutrition too.
I think there’s too many confounding effects here to isolate sunlight as the main reason why spending more time outdoors correlates with less myopia, and why the rates are increasing.
The eye appears to regulate it’s own growth… by generating varying growth hormone levels in response to focus. In our natural environment, we would have had much less opportunity for up-close focusing, so the system evolved to operate in an environment with predominantly distant focusing. If instead your dominant activity is up-close focusing, this system cannot regulate eye growth correctly. High insulin levels from a high-carb diet also seem to disrupt the system (Cordain et al http://pmid.us/11952477).
So at the same time we’ve been going outdoors less, focusing up close more, and getting more sunlight. Myopia rates could be increased by some or all of these, plus as-of-yet unidentified factors.
Myself, I developed myopia around age 13 despite spending much more time playing outdoors than most children. But I *also* spent virtually all of my indoor time focusing very closely: reading or on the computer.
Glad to see the insulin link. If hyperinsulinemia is warping lens development, those who were spent more time active outdoors would be expected to be less susceptible to the same high carb diet. Perhaps this also explains the rise in the glasses-IQ association–a strangely intuitive but false stereotype that psychologists have struggled to explain. Sunlight may play a role but I think it is far more likely that time indoors means time spent reading or playing video games instead of running and playing outside. And since everyone in The Zoo is suffering from excessively carb-rich diets, exercise will show a protective effect. If this hypothesis is true, it may appear to be an interaction between diet and exercise. But if excessive insulin is the culprit, anything that increases it (refined grains, sitting) will be bad and anything that decreases it (exercise, fasting) will be better.
These studies showed that statistically the kids who spent more time outdoors were less nearsighted. Any one person may still become nearsighted no matter how much time spent outdoors, but on average, fewer will become so.
Both of my parents have perfect eyesight, as does my sister. Despite an entire life spent outdoors (in TX), but habitually reading anything I could get my hands on since 4, things started going blurry for me in high-school, but I’ve remained at 3.25 since then. I’m staying away from corrective keratome procedures, as it’s still too “new” to log long-term effects, for my comfort.
My family seems to be the exception to this theory. I have six siblings and two parents, ranging in age from 43 to 82. I note this because, as children, all we ever did was play outside. After all, there was no such thing as cable TV or any other electronic distractions. Even in the winter, we were outside in the snow. My father worked as a landscape contractor for 30 plus years, and most of us worked with him during the summers.
Eight out of nine of us have required vision correction. I used to wear -10 and -12 contact lenses before I had LASIX 13 years ago. I still get lots of sun, take fermented cod liver oil and high vitamin butter oil daily, and eat a primal diet. Even so, I recently had to get my first pair of glasses since my surgery.
Obviously, in my family’s case, genetics is a strong influence.
I played a lot outside as a kid. One of my eyes is near sided and the other is far sided. Its kind of crazy.
wonder how much it has to do with only having to focus on things within a 20ft (or smaller) radius when you’re indoors all the time.
After discovering that my niece and nephew had been in a foster home for 2 years I took them both into my home. At the ages of 6 and 3 they had spent all their lives with a junk food diet, computers, TV’s, Gameboys – anything to keep them quiet – firstly by their parents and then their foster carer. Luckily both children were ‘skinny’ but their other problems started to add up – the 3 year old was in 12-18 month clothing, who couldn’t get warm, couldn’t walk more than 100 yards before becoming exhaused and the 6 year old had, hypermobility, fallen arches and severe myopia – that hadn’t been dealt with. The optician felt that with all the changes these poor children had gone through he would let her settle in her new home and new school and review it then, not wanted to add to the stigma of wearing glasses in a new school.
6 months later – My boy had caught up, in height and weight, to within 6 months of his age and my girl – hypermobility was sorted, arches had developed and no longer needed glasses. The optician was astonished – he had never seen anyone’s eyesight return to near normal. He continued to examine every 6 months for another year, then to yearly. We are now 5 years down the line and still no glasses are required!! The change in their lifestyle? Real food – meat, veg, limited TV, outdoor play, bare feet whenever possible, sun caps not sun glasses, walking a mile to school and back every day, scooters, bikes, skipping ropes. I truly believe their change in lifestyle saved them in more ways than one.
Yes! Which is why it’s a bit unfortunate that there are several photos of you wearing sunglasses – and Richard Nikoley too.
I think there’s a much larger genetic component as opposed to an exposure component. For example, people within the LDS religion have what I would consider an abnormally high incidence of eyesight issues – I’ve never seen more children in glasses than in SLC.
Very interesting. I am definitely outdoorsy and played a lot outside but I’m still very nearsighted.
I am extremely nearsighted, and I played outside constantly (and mostly barefoot) as a kid. I was also fed properly. I have one myopic parent and one with normal vision. I’m inclined to agree more with Loren Cordain on this one — I think it’s something to do with sugar and carbs making IGF-1 levels surge, which in turn elongates the eyeballs. Combine that with some genetics, and you have a perfect setup for myopia.
I am nearsighted–became that way at the age of 21. Lived in the tropics and had plenty of sun exposure until age 18, at which time I arrived in the Northeast of this country for college. Needed glasses within 3 years–coincidence or not? It was about the same age as my father first needed glasses for myopia. Interesting hypothesis. My daughter is severely nearsighted–since before age 7. I didn’t consciously keep her from going outside to play, and she did, but she also was and is a bookworm and spent a lot of time indoors reading. My son still has 20/20 vision and did and does spend oodles of time outdoors, so my experience at least doesn’t contradict the hypothesis!
Doesn’t surprise me at all. I am a freelance writer and editor, so I stare at a computer screen all day long. When I work at home, I prefer to work next to a window rather than turn on a lamp. My vision is 20/30 (farsighted), and I’m just fine without glasses. Right now, I am working at a client’s office, in an interior room with no access to natural light. Working under fluorescent light all day is really rough on my eyes. I need to wear +1 readers (optometrist’s suggestion) just to get through the day. I go outside at lunchtime just for a few minutes to give my eyes a break. Sunlight really helps.
Very interesting article. I wonder if at 30, my nearsightedness can be even slightly abated by getting more sunlight. I’ve been getting ALOT more sunlight lately (I have trouble sleeping and am trying to get a bigger dose to see if it helps), it will be interesting if my eyesight has improved at all on my next eye test.
Both of my parents are myopic, my Mother has worn glasses since she was 11 or 12. Neither my sister or I wear glasses. We were outside all the time when we were young.
As children, we spent pretty much all of our time outdoors; playing indoors just wasn’t done in those days in my neighborhood (during the 50s.) Sadly, I’m myopic and have been since an early age. My brother was far-sighted. Must be in the genes.
I doubt this, too. I noticed my eyes getting bad while I was a caddy the summer before my 8th grade year. If you don’t know what being a caddy is like, it’s basically spending all day, every day during the summer outside carrying a 40lb golf bag. Plenty of good sun for 10-14 hours every day. I did it the summer before as well.
The African kids have many other factors going on besides playing outside all day. In addition to caddying, I played video games at night on a small screen for a couple hours, or I watched TV, or I read. All of those things, when done for long periods without breaks/refocusing, can weaken your eye muscles. I doubt the kids mentioned above have access to those activities as often, which is why their eyesight is better overall.
Got myself some sweet pterygiums from not wearing sunglasses!
Not cool..
http://en.wikipedia.org/wiki/Pterygium_(conjunctiva)
Sunlight is certainly important and may impact the development of myopia as you suggest. However, Loren Cordain, Ph.D. has made reference to hyperinsulinism contributing to myopia. Perhaps those who played outdoors as children but still became myopic were eating a Standard American Diet with too many simple carbs, milk, candy, etcetera, all which boost insulin levels. Good sun exposure may not have been enough to overcome dietary trauma.
I’m extremely nearsighted. I started getting that way in the 3rd or 4th grade, and my vision got worse until I reached my full growth as a teenager. I played outside a lot as a kid; everybody did back in those days. After I started wearing glasses, I probably did become more of an indoors person, but it was a gradual process. My sense is that developing an interest in “close work” like reading was more an effect than a cause of nearsightedness. I really didn’t become much of a reader until I’d been myopic for several years. My father had 20-20 vision, only needing glasses for reading when he became middle-aged. My mother is slightly nearsighted. My theory is that someone as myopic as I am would not have survived to reproduce in primitive times. But in modern times, I did, and one of my kids is as nearsighted as I am, and the other is mildly nearsighted.
I have done a lot of work in 3rd world countries. One thing that I noticed that the adults that I worked with, that grew up in near poverity had great eyesight. 20/20 or better. In addition to the sunlight theory, I wonder if that since their parents could not afford glasses at an early age, if their eyesight corrected itself as they grew older?
In other words, kids bodies change and perhaps blurred vision at some point is just part of the growth process. If you put a crutch (glasses) on during that growth process, it keeps the eyes and muscles from developing as they should.
My eyesight started to deteriorate (myopia) when I moved from Brisbane in Australia (lots of sunshine and an outdoors lifestyle) to the UK back in 2005. Every six months (and sometimes more frequently) I’d have to get re-tested, and sure enough, a new prescription was required.
Three months ago I moved to Malta and within a month noticed that my vision was improving. Today, I’m walking down the street, watching television etc quite well, without glasses!
Sure, some things are slightly fuzzy, and legally I wouldn’t be able to drive without glasses as I still can’t read a number/license plate clearly at 20 feet, but it’s a HUGE improvement and I put it down to the better quality light.
Seems bogus to me, growing up in Florida I was outside a lot and theres plenty of sun around. In fact, I would be one to argue that I think the bright Florida sun may have caused my condition because its not like I had money to wear sunglasses between the ages of 6-12 (when I found out I was nearsighted). My eyes were always very sensitive to the sun and I always sneeze if I look in the general direction of the sunlight when I first walk out into it. I always remember the hottest and brightest afternoons having problems being outside, especially in the heat of the day when the sun was super bright, but I wanted to be playing outside so I just endured it. I always wear sunglasses now to prevent my eyes from straining and since that time my eyes stopped getting worse until I had them corrected with laser surgery earlier this year. I will always wear sunglasses to protect my eyes outdoors. The bright sun hurts your eyes, it doesn’t help them in any way.
Myopic? Check (-9 now)
When? First glasses around age 9
Parents? One myopic, but half mine.
Outdoors as a kid? Check.
Grew up before PC and outside the US, where there was not much of any TV either.
Easily did the 10-18h outside per week, so the link in my case is weak…
Myopic? Check (-10 now)
When? First glasses around age 9
Parents? One myopic, but now at only half mine.
Sibling, ditto me.
Outdoors as a kid? Check, plenty.
Grew up before PC and outside the US, where there was not much of any TV either.
Easily did the 10-18h outside per week, so the link in my case is weak, as seems to be the case for many of the other posters with similar constellation.
I worked outside as a child on a working farm, we irrigated our fields, and of course I took care of that from the age of 12. So in addition to being short-sighted, 20-400 in my left eye, I have a cataract growing on my right lens (as well as all sorts of precancerous growths on my arms). Gee THANKS!
I don’t know, Mark. Neither of my parents are nearsighted, nor are any of my siblings. I am and also astigmatic. I grew up in a foreign country and literally lived and played outdoors constantly–in a very sunny country.
I understand that stress can play a big role in unleashing myopia, and there were some stressful aspects to my childhood in that my parents didn’t always get along, nor did I get along very well with one parent–who was stressed for various reasons. Asian kids are very stressed by very high scholastic standards and pressures.
Well as far as genes are concerned I was pretty much destined to develop myopia – the wearing of glasses or contacts is rife in my family, and has been for a few generations, beyond the two world wars in fact. But as far as immediate family goes, my dad developed myopia in his teens, my mother even now (in her late 60s) only needs reading glasses. My eldest brother had perfect eyesight, my next brother has slight myopia (he’s supposed to wear glasses, but doesn’t as he forgets about them, due to only really needing them for watching television), my next brother after him has perfect eyesight, and I developed myopia in my mid-teens – it stayed fairly mild, like my brother for about a decade, and since has been gradually worsening (thanks left eye for being weaker than the right and confusing my poor brain LOL). As kids (as far as I know, cos I’m the baby and there’s a lot of years between me and my brothers) all of us but the youngest of my brothers spent as much time as possible outside as kids, my mum often goes on about making us all go out to either play or help her with the garden as soon as it was warm enough for us kids to go out in just our underpants (usually April-ish), maybe only for an hour or so, but it was every day, for about 6 months of the year (we still got plenty of outdoors time the rest of the year, but we were a little more covered up!) from babies til we got to the age where we started wanting to do our own thing; for me that was around age 9 and I retreated to my room… I knew my eyesight was changing when we went on holiday one year and during the journey, I couldn’t make out trees in detail on the horizon, or read signposts before my parents whilst travelling in the car. Not long after that, I started getting headaches at school, as I couldn’t read the board, even sat at the very front of the class. So did 6 years of being mostly indoors trigger that gene in me, I wonder… However, interestingly, although I still don’t get outside as much as I would like, I do willingly spend much more time outdoors than I used to, and yet my eyes are STILL getting worse. I’m actually due to see the optician this summer for a check-up and I will be interested to know if there’s been any change…