Did you know that your eyes can adapt to being open in sea water? When you first open them underwater in the sea, they'll sting like crazy. If you persist - or at least this was the case for me, that effect will go away, and you can open them underwater without pain.
They will still be unfocused, though, of course. From the article, it sounds like you need to practice for a while before the eye learns how to focus underwater:
> Gislen wondered whether the Moken children had a genetic anomaly to thank for their ability to see underwater or whether it was just down to practice. To find out, she asked a group of European children on holiday in Thailand, and a group of children in Sweden to take part in training sessions, in which they dived underwater and tried to work out the direction of lines on a card. After 11 sessions across one month, both groups had attained the same underwater acuity as the Moken children.
Perhaps this only works for children, who seem somehow more biologically adaptable? The body is quite adaptable in general so I would believe it that people who swim regularly could see better underwater. I'm glad to have the science though to study the effect more rigorously.
I come from a Mediterranean island and I spend my summers swimming and diving, always with open eyes. I don't want put my feed on sea urchins or crash with a boat or rock! My eyes only hurt in swimming pools after a while. In the sea, my eyes don't hurt. I'm in my thirties.
I wouldn't say sting like crazy, for me it's a mild irritation that goes away quickly unless the water has a lot of suspended sand. Been swimming in sea water with eyes open since I was young; it used to be more painful.
That's weird. I experience the exact opposite. When I was younger I could keep my eyes open underwater in all sort of condition. Today, they sting like crazy even in fresh water.
Did you know that your eyes can adapt to being open in sea water?
Wow... I didn't know that. Losing my mask and panicking while diving has always been a concern of mine. I'll have to try this out. Regardless of being able to see clearly, it'd be great to just not be bothered by an onslaught of seawater.
>> Losing my mask and panicking while diving has always been a concern of mine.
That's one of those things that take me by surprise when I discuss peoples' relation with the sea. I never thought there was a problem with having your eyes open underwater. I'm Greek and I've spent a lot of time in the sea when I was young, so I must have just gotten used to it.
Mind you, my eyes still get red but I don't actually feel them stinging or experience anything unpleasant.
I can totally understand being worried about panicking in the sea, though, especially if you're diving. I snorkel, and even so, when I go under it's always in the back of my mind that anything can go wrong and I need to keep my wits about me at all times. I've been close to drowning twice too, so yeah. Need to be careful.
Your tears are very salty so seawater actually isnt that different from the water that's already in your eyes. A lot of panic people have in opening their eyes in seawater stems from their experience of chlorinated swimming pools - which absolutely stings like hell!
Yep. But when something goes wrong and you're 80 feet underwater, panic is not far away, and is really risky, since the panic response is unlikely to be the safe thing to do when deep underwater. So anything I can do to become acclimatized to problems is a win.
Practicing (and successfully remediating) this scenario is required for PADI OWD certification. My instructor removed our masks and breathing gear one at a time. We had to reposition the mouthpiece, fetch the mask, perform X number of breaths without a mask, put the mask back on and clear it all while keeping calm and staying level. Doing it in a lake at ~ 20f depth wasn't much more hostile than doing it in a pool. However I wouldn't want to lose my mask during a drift dive, as it could very well be gone quite fast.
Yeah, but taking off my mask still makes my eyes sting, and I certainly wouldn't want to panic 80 feet down. So... despite having done it a number of times, it's heartening to hear that I might be able to get past the sting. If I could just take off my mask at will and not worry about it, that'd be one less thing to worry about.
My last job for 6 years was fixing hydraulics and electrical systems under water, among other things. I am now 51, and at that time, my presbyopia, or farsightedness increased. I wear +1.50 reading glasses topside. Just old age, and the len's inability to accommodate as much as when you are younger. I could open my eyes, maskless in fresh or salt water. And it is not chlorine that burns your eyes in most cases. If you think you smell chlorine, you're mistaken; chlorine is odorless. It is the byproducts of free chlorine that eat abundant organic matter that creates chloramines that you are smelling. A sure indicator they did not maintain a minimum level of free chlorine to begin with.
In any case, I was able to improve my work underwater over those six years. If you discount feeling with my hands, what augmented my ability was not pupil dilation or lens accommodation, but the brain's processing. It has been proven if you concentrate while reading without your reading glasses, you can train your years of reading to recognize the letter shapes in their new blurry appearance. Not magic here, hard work. What I would be interested in is did she change it from merely horizontal and vertical lines? I can easily see the brain also augmenting their ability to accommodate their lens and pupil dilation to make their ability even more impressive. This would explain how the European children may have 'thought' they saw clearer, but it was the brain clarifying their perception and not any lens or pupil dilation in their short study.
I remember hearing from someone who was on a long cruise trip, and on their first day, lost their glasses without hope for replacement. So they just had to cope with the rest of the trip without.
They said that it took a while to learn to cope, but once they did their short-sightedness didn't affect everyday life at all, apart from not being able to read. This included things like playing tennis.
I'm -4.5 in both eyes, and, interestingly, if I take my glasses off I can just about make out the words I'm typing here without adjusting the zoom level; mostly from shape. Zooming in a couple of notches makes the letters appear. Blurry and distorted, but legible (just). I can totally believe that practice would make me reasonably functional.
This is interesting. I am from the Caribbean and my parents a small rock(basically) off the coast of the mainland where your lively hood depended on the sea in one way or the other(fishing, diving, boat building). As a kid I would spend a lot of time in the water there swimming and diving. I felt like my underwater vision was so much better. This might not have been just a feeling then.
I am a urban person that could see underwater, and until now I wasn't aware that it was something that could be learned, I just love diving in pools, and could not afford any equipment, so I got used to diving with eyes open, even in stupid high chlorine pools, and I don't need to mechanically close my nostrils either.
I can do this very easily, and I’ve been able to as long as I can remember. I always assumed everyone could.
Then again, I have weird eyes in general. One has almost perfect vision, the other is really bad (don’t remember the exact prescription, but the big “E” on the vision chart is just a dark blur when I don’t have my single contact in).
Yes. Mentally, I move my point of focus from the monitor "backward" into space -- like an imaginary 3D cursor anchored on my screen, then moving away from me along the ray of my eyesight. Almost as if I was going to peer around the monitor and look for something behind it, except without actual movement. Imagine doing that, and it might help.
It's easier to do with one eye shut than with them both open.
I can do this. I've noticed that it's bringing my focus to a point closer to my face. I guess I can do it the other way because I can refocus, but I've noticed my eyes out of focus close and in focus at distance. I'm curious if this ability correlates with good vision, because my distance vision is ridiculously good.
I can also (through conscious effort) expand my pupil size. Looking in the mirror if, instead of focusing on one point, I try to look at a larger area (without moving my eyes) my pupils will expand.
There are hidden picture books which look like random noise until you manage to focus your eyes 'behind' the book. I could never do that but others could. So I would say yes, you can with some effort.
I mean with just one eye, being able to consciously refocus that eye.
For example, looking at this writing on your screen able to make that go in and out of focus.
I can bring my finger into focus, drawing my focal point in front of the screen, and if then remove my finger I can hold that focus (with about a 50% success rate). Perhaps that is cheating a little ;).
I can do this. It took me a very, very long time to figure out how to explain it to people who have "normal" vision. For what it's worth, I also have diplopia and I'm convinced that they are related.
This image[1] is pretty good. Look at the two squares, and squint a lot, so you see double, and the try to make the pretty far. Now gradually squint less and try to make the two center squares align with each other so you see three squares. When you manage to do that you have the correct focus. Shift your gaze to the image.
I think your friend isn't as lucky as you think. The eye/brain should automatically make the focus as sharp as possible so all that you can do consciously is make it worse.
Then again, if your vision isn't perfect there are tricks like placing pressure on the eyeball or squinting which can change the focus, but are probably not too healthy in the long term.
Best advice is to see an optometrist instead. Although, I have found that they aim to correct vision for 6 metres in red-green light. If you're reasonably young and myopic, ask for a slightly stronger minus power to get better blue vision at infinity (at the risk of more eye strain close up). The extra -0.25 makes a huge difference for me, really allows depth perception to "click" properly.
20/20 (or 6/6 in metres) is awful. I didn't know that until optometrists started moving from cards at a distance (where I could choose which line I wanted to be able to read, thank you very much) to the retinal projection thingies most of them use now. The difference is, as you noted, about -0.25 for myopia in the -3 to -4 dioptre correction range, and it's huge. I'll assume that it's a better set-up than the old way for astigmatism (which was never a problem for me), but settling for "normal" vision when there's an option... I don't think so.
If you know a bit about optics it's not hard to derive. The difference between correction at 6m vs infinity is 1/6 - 1/inf = 0.166.. dioptres.
On top of this, one thing that surprised me was the difference in correction between red, green and blue light. The refractive index of the eye varies according to light frequency such that blue is focused approximately 2 dioptres more than red. If your myopic eyes are corrected for red at infinity, you won't be able to focus on any blue light further than 0.5m away! Not really a concern in the natural world but very noticeable in a server room full of blue LEDs or on a screen with blue text on black.
The difference in power between red and green is less but still useful enough for some vision tests. If you can focus on red traffic lights but green ones are blurry, this is why - consider a stronger power as long as it doesn't strain your near vision.
I'm slightly farsighted, and while I can see without my glasses, I have to make a conscious effort to bring the world into focus if I'm not wearing them and headaches eventually result.
Only trick I know is getting the right prescription glasses...
Huh, I didn't know this was something special. I used to swim underwater with my eyes open all the time when I was little and I could see underwater just fine like the article describes. I just assumed everyone could :).
Although I couldn't do it in salt water, it stung my eyes too much but that might also be due to me learning to swim in pools instead of the sea.
You can see underwater, but you don't see as well as they do:
> The kids had to dive underwater and place their heads onto a panel. From there they could see a card displaying either vertical or horizontal lines. Once they had stared at the card, they came back to the surface to report which direction the lines travelled. Each time they dived down, the lines would get thinner, making the task harder. It turned out that the Moken children were able to see twice as well as European children who performed the same experiment at a later date.
I suspect this is mostly just a question of how much time people spend under water. When I used to swim a lot I did not notice my vision being worse underwater. I could easily read an underwater wrist watch for example.
PS: I still have better than 20/20 vision. But, I think your eyes age faster than most people suggest as I can't see as well even at just 35 vs 15.
Hm. Salt water is (according to my google-fu) denser than fresh water. The article says, "When the eye is immersed in water, which has about the same density as the cornea, we lose the refractive power of the cornea..."
I wonder if this refers to salt or fresh water. Maybe both, if the density delta between the two is trivial.
I know, but the crux of the article seems to be that you shouldn't be able to see underwater even if you can keep your eyes open. I could/can see underwater just fine but only if I can keep my eyes open of course. I cannot keep my eyes open in salt water, but that might be a lack of acclimatization is what I'm saying.
Gislen was able to test a few Moken adults in the same way. They showed no unusual underwater vision or accommodation – perhaps explaining why the adults in the tribe caught most of their food by spear fishing above the surface. “When we age, our lenses become less flexible, so it makes sense that the adults lose the ability to accommodate underwater,” says Gislen.
I had the same experience. It's strange. I always thought that was normal (that you could see better underwater than above water). I don't really like swimming, so I haven't done it more than once or twice as an adult. Now I'm curious if I would have the same experience.
Maybe swimming a lot underwater causes nearsightedness. But then, in the article, I see:
> She thought the first theory was unlikely, because a fundamental change to the eye would probably mean the kids wouldn’t be able to see well above water. A simple eye test proved this to be true – the Moken children could see just as well above water as European children of a similar age.
Yes, of course, the people in Thailand do it to survive.
I was thinking more along the lines of first-world people, especially children. E.g. exposing "European children on holiday in Thailand" to what I stereotype as the fetid waters off the coast of third world countries.
It may be a stereotype, but that doesn't mean it's not true. I'd venture that the phrase "sewage treatment plant" is not part of the vernacular there.
They will still be unfocused, though, of course. From the article, it sounds like you need to practice for a while before the eye learns how to focus underwater:
> Gislen wondered whether the Moken children had a genetic anomaly to thank for their ability to see underwater or whether it was just down to practice. To find out, she asked a group of European children on holiday in Thailand, and a group of children in Sweden to take part in training sessions, in which they dived underwater and tried to work out the direction of lines on a card. After 11 sessions across one month, both groups had attained the same underwater acuity as the Moken children.
Perhaps this only works for children, who seem somehow more biologically adaptable? The body is quite adaptable in general so I would believe it that people who swim regularly could see better underwater. I'm glad to have the science though to study the effect more rigorously.