Quote:
Originally Posted by Rosa
Seems sensible enough. The point I was trying to make is that *maybe* the reason you see so much bad eye sight nowadays isn't because we are inheriting bad eye genes (tho presumably this must happen a bit for the reasons you outline), but simply because we are staring at screens (and books) all the time and its fucking our eyes up (the same way running fucks up your knees):
let me try this one more time. If you are near-sighted, you have a hard time focusing on things that are far away (your focal range is only things very near to you). Near-sightedness is far more common than far-sightedness. in order to focus on near things, you must bend your lens (the disk inside your eyeball... it physically changes shape to help you bring things into and out of focus.. i.e it bends).
My hypothesis was that the increased prevalence of near-sightedness arose because we now spend so much time focusing on near things (our screens and books) and as a result our lenses get stuck in that bent position and have a hard time unbending. in cave-man days they didn't have iproducts or books, and they probably spent a lot more time dynamically adjusting their focus to both look at near things (like each other) and to look at far things (like predators and big-game on the horizon). the difference would be frequency of bending and unbending... keeping it flexible, like a tight little underage gymnast. If this is all the case, then cave-men probably had better vison on average, not so much because they were genetically selecting for it, but rather because of how they used their eyes.
but this is all wild speculation. maybe there are genes for bad vision. must be a bit of that. maybe im totally full of shit. probably.
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guys! Nature published an article TODAY shedding new light on the whole thing!
"The myopia boom
Short-sightedness is reaching epidemic proportions. Some scientists think they have found a reason why."
The myopia boom : Nature News & Comment
looks like I was wrong: "...scientists are beginning to find answers.
They are challenging old ideas that myopia is the domain of the bookish child and are instead coalescing around a new notion: that spending too long indoors is placing children at risk"
"For many years, the scientific consensus held that myopia was largely down to genes. Studies in the 1960s showed that the condition was more common among genetically identical twins than non-identical ones, suggesting that susceptibility is strongly influenced by DNA1. Gene-finding efforts have now linked more than 100 regions of the genome to short-sightedness.
But it was obvious that genes could not be the whole story. One of the clearest signs came from a 1969 study of Inuit people on the northern tip of Alaska whose lifestyle was changing. Of adults who had grown up in isolated communities, only 2 of 131 had myopic eyes. But more than half of their children and grandchildren had the condition.
Genetic changes happen too slowly to explain this rapid change — or the soaring rates in myopia that have since been documented all over the world (see 'The march of myopia'). “There must be an environmental effect that has caused the generational difference,” says Seang Mei Saw, who studies the epidemiology and genetics of myopia at the National University of Singapore.
There was one obvious culprit: book work. That idea had arisen more than 400 years ago, when the German astronomer and optics expert Johannes Kepler blamed his own short-sightedness on all his study. The idea took root; by the nineteenth century, some leading ophthalmologists were recommending that pupils use headrests to prevent them from poring too closely over their books.
...
Researchers have consistently documented a strong association between measures of education and the prevalence of myopia. In the 1990s, for example, they found that teenage boys in Israel who attended schools known as Yeshivas (where they spent their days studying religious texts) had much higher rates of myopia than did students who spent less time at their books4. On a biological level, it seemed plausible that sustained close work could alter growth of the eyeball as it tries to accommodate the incoming light and focus close-up images squarely on the retina.
Attractive though the idea was, it did not hold up. In the early 2000s, when researchers started to look at specific behaviours, such as books read per week or hours spent reading or using a computer, none seemed to be a major contributor to myopia risk. But another factor did. In 2007, Donald Mutti and his colleagues at the Ohio State University College of Optometry in Columbus reported the results of a study that tracked more than 500 eight- and nine-year-olds in California who started out with healthy vision. The team examined how the children spent their days, and “sort of as an afterthought at the time, we asked about sports and outdoorsy stuff”, says Mutti.
It was a good thing they did. After five years, one in five of the children had developed myopia, and
the only environmental factor that was strongly associated with risk was time spent outdoors. “We thought it was an odd finding,” recalls Mutti, “but it just kept coming up as we did the analyses.” A year later, Rose and her colleagues arrived at much the same conclusion in Australia7. After studying more than 4,000 children at Sydney primary and secondary schools for three years, they found that children who spent less time outside were at greater risk of developing myopia...."
check out the article for more details!