The Children wo see clearly underwater...

"When the tide came in, these children began to swim, but do not like what I've seen before, they were more under water than above water, they should have their eyes wide open -... It was like a little dolphin"
In the depths of the island island in the Andaman Sea and the west coast of Thailand's small tribes lived was called the People's Moken, also known as sea nomads. Children spend most of the day in the sea and dive for food. And uniquely adapted for the job - because they can see under water. It was found that with a little practice, see the unique can be accessed by anyone youth.
In 1999, Anna Gislen at the University of Lund in Sweden, exploring different aspects of the vision, and when a colleague suggested that it might be interested in learning about the unique features of the tribe Moken people. "I was sitting in a dark laboratory for three months, so I thought:" Yes, why do not you go to Asia instead, "says Gislen.

Gislen and her daughter, at the age of six years, he went to Thailand and integrated into the community of Moken people who live mainly in houses sitting on poles. When the tide came in Moken people children splashed in the water and dive down to pick up the food, which lies meters below that Gislen or daughter can see. "They had their eyes wide open, fishing and oyster shells and sea cucumber, no problems at all," she says.
Gislen experimental setup to test how well they see the children really were under water. The children were delighted with the merger, Gislen says: "They think it was just a fun game."

Children were submerged and put their heads on a plate. From there they could see the line card display vertically or horizontally. Once you look at a map, they returned to the surface to determine the direction in which it moved the line. Every time he fell to the ground, the line to get thinner, making it more difficult. It turns out that people Moken children can see twice as well as European children, who performed the same experiment at a later date.
What happened? To clearly see the ground, you'll be able to refract the light that enters the eye on the retina. The retina is sitting in the back of the eye and comprises specialized cells that convert light signals into electrical signals that the brain interprets as images.
Refract light, when it gets to the human eye, as the outer cornea contains water, which makes it a little more dense than the air outside the eye. The inner lens refracts the light to go on.
When the eye is immersed in water, which has about the same density as that of the cornea, refractive power of the cornea to lose, so the picture is very clear.

Gislen realized that in order to clearly see the Moken children's underwater, and should be either taken some adjustments, which fundamentally changed the course of action of their eyes, or they have learned to use in different ways under the water her eyes.
I thought that the first theory is likely because the fundamental changes in the eye can mean that children can not see much more than water. Simple eye test found that it's true - Moken children can see exactly the same as the water of European children of the same age group.
He had to have some sort of manipulation in the eye, and I thought Gislen. There are two ways that you can theoretically improve submarine vision. You can change the shape of the lens - which is called the accommodation - or you can make the pupil smaller, which increases the depth of field.
Pupil size is easy to measure - and showed that it could limit their students as much as possible the known human performance. But this alone can not fully explain the visibility improved. This led Gislen believe that the lens arrangement is also involved.
"We had to do a mathematical calculation to work out the extent of the lens and adapt to them in order to learn as much as possible," says Gislen. It is found that children must be able to accommodate a much greater extent than one would expect to see under water.
"Usually, when you go under water, everything is clear, so that the eye does not even try to adjust, this is not a normal reaction," says Gislen. "But the people Moken children are able to do both -., Which may be provided to students and the minimum change in the shape of the lens seals and dolphins have a similar adaptation."
I was able to test a small number of adults in the same way Moken Gislen. He did not show any unusual vision under water or place of residence - probably explains the adult in the tribe why most food caught spearfishing above the surface. "As we age, the lens becomes less flexible, so it makes sense that adults lose their ability to absorb the water," says Gislen.
Gislen wondered if Moken children have a genetic anomaly to thank for their ability to see under the water, or is it 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, in which the dive under the water and tried to work on the trend line on the map. After 11 sessions per month, and it was both teams did the same device under water and Moken children.
"It was different for each child, but at some point in their vision would improve at once," says Gislen. "I asked them if they were doing something else, and said:" No, I can see nothing but the best now. "
I noticed, however, that European children will experience redness of the eyes, and watch out for the salt in the water when it seemed that the Moken children have any such problem. "So, maybe there is some adjustment there, that will allow them to dive up to 30 times without any irritation," she says.
Gislen recently returned to Thailand to visit the families of Moken people, but has changed dramatically. In 2004, a tsunami created by a powerful earthquake in the Indian Ocean, which destroyed much of the nation and the Moken people. Since then, the Thai government has worked hard to move around the earth, and build the house that inward and hire tribal members to work in the national park. "It is difficult," says Gislen. "You want to help keep people's safety and security and to give them the best part of modern culture, but they are losing their own culture."
Unfortunately, the children may be in the experiments Gislen and last tribe have the ability to see clearly underwater. "I just do not spend much time in the sea anymore," she says, "so I doubt that any of the children who grow up in these days in the tribe has the vision is normal."