The BBC recently published an interesting, if somewhat sensationally titled article, “The ‘sea-nomad’ children who see like dolphins.”
The article describes the ability of children from some remote islands in Thailand to see clearly underwater. Any one that has swam underwater with their eyes open knows that at best you can make out blurry shapes.
Experiments conducted with these Thai children showed that they can see twice as well as European children underwater.
The key relevance of the article is the ability of the eye and especially in children to change the shape of the lens, which we refer to as accommodation, to focus at different distances. It is their superior accommodation ability that allows these children to compensate for the blurriness caused by the loss of the refractive power of the cornea when underwater.
So what does this have to do with dolphins ?
“Normally when you go underwater, everything is so blurry that the eye doesn’t even try to accommodate, it’s not a normal reflex,.. “But the Moken children are able to do both – they can make their pupils smaller and change their lens shape. Seals and dolphins have a similar adaptation.” -Anna Gislen , researcher
Unfortunately the experiments also showed that these children lost this amazing accomodation ability as they became older and that by the time they were adults could see no better than their European counterparts.
Age catches up with everyone. This loss of accommodation ability is what causes most people to require glasses as the reach middle age.
Even children that can see like dolphins will eventually need bifocals.