A new study comparing Americans’ vision today to what it was like nearly 40 years ago says that our nation’s eyesight is getting worse as myopia, or nearsightedness, continues to become more prevalent. The study, led by Susan Vitale, appears in the Archives of Ophthalmology.
Vitale and colleagues used data from the National Health and Nutrition Examination Survey (NHANES) to compare the percentage of black and white Americans aged 12 to 54 with myopia in 1971-1972 and 1999-2004 [Reuters]. In the early 1970s only a quarter of people were nearsighted, but by the study’s 1999 to 2004 window that number had shot up to 42 percent.
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Sharks and humans seem more and more alike with each new scientific find. Not only do some sharks have hunting patterns that resemble those of serial killers, but now scientists have discovered that the hammerhead shark’s distinctive head shape allows it to see like a human.
Binocular vision occurs when the fields of two eyes overlap, allowing the accurate perception of depth and distance. It is especially important for predators which need to judge the distance to their prey [BBC News]. Researcher Stephen Kajiura, a sensory biologist, suggests that the stereo vision helps the sharks hunt prey like squid that dart around in three dimensions. The wide set eyes also allow the sharks to see through 360 degrees of vision, according to the researchers, who published their findings in The Journal of Experimental Biology.
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Contact lenses provide a number of convenience advantages over glasses, but one they come up short in one area—you can’t get contacts that automatically adjust to the sun’s UV light and darken, like the photochromic lenses many bespectacled people enjoy. But that could soon change: Researchers in Singapore led by Jackie Ying have now created a contact lens that responds to UV light.
Transition lenses for glasses are coated with a dye that is transparent when out of the sun, but responds to UV light by changing shape and darkening. Few previous attempts have been made to design transition contact lenses, largely because it’s difficult to apply dye coatings uniformly to the delicate, soft surface of a contact lens. Ying and her colleagues got around this by developing a contact lens that embeds dyes uniformly throughout the material [Technology Review].
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Some migratory birds that have to navigate across continents have an extremely useful tool at their disposal–an internal compass that points unerringly towards magnetic north. Researchers already knew that some birds possess these biological compasses, but their mechanism has been unclear. “This is basically the sixth sense of biology, but no one knows how it works…. The magnetic sense is by far the least understood sense in the natural world,” [Science News], says study coauthor Henrik Mouritsen.
Now, researchers have determined that light-sensing cells in the eye convey the crucial message to a special visual center of a robin’s brain, called cluster N. Special proteins called cryptochromes in the birds’ eyes may mediate this light-dependent magnetic sensing, Mouritsen says. Light hitting the proteins produces a pair of free radicals, highly reactive molecules with unpaired electrons. These electrons have a property called spin which may be sensitive to Earth’s magnetic field. Signals from the free radicals may then move to nerve cells in cluster N, ultimately telling the birds where north is [Science News].
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A new discovery about how mantis shrimp process light could give rise to new and more powerful consumer electronics, according to a new study. Mantis shrimp possess the animal kingdom’s most complicated eyes, capable of distinguishing between 100,000 colors — 10 times as many as humans — and seeing circular polarized light, or CPL, which can’t be detected by any other creature [Wired.com]. Circular polarized light is one of two forms of polarized light, or light waves that travel in a specific plane.
The specialized CPL detecting cells in shrimp eye are similar to the optical detectors found in DVD players; each can convert polarized light into other forms so it can be stored or processed. However, shrimp eyes can do this with all colors of circular polarized light across the spectrum, according to the study in Nature Photonics. The detectors in DVD and CD players can only recognize circular polarized light in a few colors. The research team thinks that in the future, optics devices might be beefed up by chemically engineered crystals that could mimic the light polarizing cells of the mantis shrimp eye.
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Looking for an easy, cheap way to spy on your neighbors? Researchers are working on a device that may be just the thing, which uses a simple wireless network to “see” through a wall and detect people moving around in the room beyond. But paranoid apartment-dwellers will be glad to know that the system still has plenty of limitations. At the moment the system can only track movement within a three-foot range, and it can only sense motion–it can’t put together a picture of what or who’s moving.
The system relies on the variations of radio signals in a wireless network. The signal strength at any point in a network is the sum of all the paths the radio waves can take to get to the receiver. Any change in the volume of space through which the signals pass, for example caused by the movement of a person, makes the signal strength vary. So by “interrogating” this volume of space with many signals, picked up by multiple receivers, it is possible to build up a picture of the movement within it [Technology Review]. The paper describing the technology has been posted on the arXiv pre-print server, and has not yet been peer-reviewed.
The device could be more than a boon for voyeurs or robbers. The researchers argue that the technology could be used in search and rescue operations, with emergency teams using the same radio technology used by Wi-Fi networks to build a web of sensors around a disaster site, revealing the location of victims and survivors [Telegraph].
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Image: Joey Wilson and Neal Patwari
For two squirrel monkeys nicknamed Dalton and Sam, life has gotten a lot more colorful. Researchers used gene therapy to correct the color blindness of the two adult monkeys, giving them the ability to distinguish between red and green for the first time. The fascinating accomplishment suggests that scientists may someday be able to cure other kinds of blindness in humans. And because the treated monkeys were “middle aged”, it challenges the assumption that gene therapies cannot work in adults because their brain connections are too set in their ways to change beneficially [New Scientist].
The field of gene therapy, in which a malfunctioning gene in a patient’s body is replaced with a functional one, fell into disarray one decade ago following the death of an 18-year-old in a clinical trial. But since then scientists have regrouped, using animal studies to probe the technique’s safety. Last year, researchers progressed to the point of safety trials in humans for the treatment of one rare eye condition called Leber congenital amaurosis, and were able to dramatically improve the patients’ sight. Those results were stunning, but they were also achieved in children, whose still-growing brains can rewire themselves on the fly in response to new sources of visual stimuli [Wired.com].
In the new study, published in Nature, the researchers used a type of squirrel monkey in which the males lack a visual pigment called L-opsin. Its absence renders the monkeys color-blind, unable to distinguish reds and green. Most of the females, on the other hand, see in full color. So the scientists got to wondering: what would happen if they gave a boy squirrel monkey the same opsin that girls have [Scientific American]. They used a harmless virus to ferry in the gene that makes opsin, injecting the virus behind the monkeys’ retinas.
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A person can witness an event in real life, see a doctored video of the same event, and then convince themselves that what they saw on the video is what actually happened, according to a recent study that casts doubt on the reliability of eyewitness testimony.
Psychologists set up an experiment where they filmed two people sitting side by side–one experimental subject and one researcher pretending to be a participant–playing a gambling game where they bet phony money on whether or not they could answer multiple choice questions correctly. They were told that the person with the most money at the end would win a prize.
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It’s a movie cliche: the moment when the lost traveler intersects a set of footprints, only to realize that the prints where made by his very own boot soles. The hero then realizes, with plunging heart, that he’s been walking in circles while trying to walk a straight course through the featureless expanse. Now a small study has shown that the cliche is true. Without the sun, a compass or a landmark, people trying to follow a straight course through a forest or a desert ended up back where they started [HealthDay News].
In the first experiment, six participants tried to follow a straight course through a forest in Germany, in an area where the land is flat and the trees quickly begin to look alike. The two subjects who walked on a sunny day stayed on a fairly straight course (as tracked by a GPS device), except for the first 15 minutes when the sun was behind the clouds. But the four who walked on an overcast day repeatedly traveled in circles, sometimes crossing their own paths after only 10 minutes. Says lead researcher Jan Souman: “They didn’t really believe when we showed them afterwards…. I think that’s certainly a point to take away, people may feel very confident about the direction where they’re going but it’s not certain” [ABC News].
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Three patients with severe damage to the corneas of their eyes have achieved dramatic improvements in their vision thanks to contact lenses coated with their own stem cells. While the study was extremely small and the results are quite preliminary, the unequivocal improvement seen in the three patients has given doctors hope that the treatment may work for many patients with damaged corneas. Two of the three patients were legally blind in the treated eye; they can now read big letters on the eye chart. The third could read the top few rows of the chart but is now able to pass the vision test for a driving license [The Australian].
The cornea is the transparent layer that covers the eye – but it can lose transparency, damaging sight. In the most serious cases, people can need cornea grafts or transplants. Corneal disease can be caused by genetic disorders, surgery, burns, infections or chemotherapy. In this study, all three patients had damage to the epithelium – the layer of cells covering the front of the cornea [BBC News].
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Specialized cells found only on flower petals have the same basic function as nonslip mats that prevent people from slipping in the shower, a new study has determined. The bumpy cells, called conical cells, help bees come in for a landing on the flower petals and find their footing, so they can get down to the important business of pollination.
Conical cells had been something of a botanical mystery, with most researchers assuming they played a visual role. One hypothesis held that by modifying the spectral properties of the petal, the cells enabled the plant to appear brighter to pollinators [The Scientist]. In the study, will be published in a forthcoming issue of Current Biology, researchers showed that the conical cells’ main function is to provide friction, and that bees can detect them by touch. The first experiment used two kinds white snapdragons that looked identical to both human and bee eyes, but one was a mutant with flat cells instead of conical. The bees initially went to both flower types, but after 20 visits they chose the blossoms with conical cells more than 80 percent of the time.
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A group of geneticists has peered into the eyes of nocturnal animals, and say they may have found the secret to these animals’ keen night vision: light-sensing cells with unusually structured DNA that turns each cell’s nucleus into a tiny lens.
The researchers were examining mice’s rod cells, the cells in the retina of the eye that operate under low light. Usually, they say, active genes are clustered in the center of each cell’s nucleus for convenient access to cellular machinery. But rod cells in the mouse retina shove active genes to the outside of the nucleus, the researchers found. The center of the nucleus is instead occupied by densely-packed inactive DNA called heterochromatin. Mice put this type of DNA front and center in their rod cells. “Everything that must be inside is outside, and everything that should be outside is inside,” [lead researcher Boris] Joffe says. “It was an absolutely heretic finding” [Science News].
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Scientists have found that manipulating a person’s sense of touch can confuse their sense of sight, an intriguing finding that suggests that touch and vision are integrated in the human brain…. For decades, instructors in medical schools have taught students that the senses —including vision, touch and sound — are interpreted in different, discrete parts of the brain, says Michael Beauchamp of the University of Texas Medical School at Houston. “Now it turns out what we’re teaching them is wrong,” he says. “There’s a lot more cross talk between the modalities” [Science News].
In the experiment, which will be published in an upcoming Current Biology, researchers used a postage stamp-sized device that used tiny pins to stroke the test subject’s finger in either an upward or downward direction. When subjects watched a stationary stripe on a computer screen after a machine stroked their fingertips, the motion of the stroking created the illusion that the stripe was moving [ScienceNOW Daily News].
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Stroke patients with damaged vision may be able to restore their sight with the help of computer exercises based on the phenomenon known as blindsight–when a person with vision loss senses something they cannot actually see [Reuters]. Lead researcher Krystel Huxlin explains that people with blindsight may not be able to consciously perceive a visual stimulus, yet when they’re forced to answer questions about it their answers are often correct.
Researchers studied patients whose strokes had damaged their primary visual cortex, and whose impaired vision limits some everyday activities like reading and driving. “This is a type of brain damage that clinicians and scientists have long believed you simply can’t recover from. It’s devastating, and patients are usually sent home to somehow deal with it the best they can” [CBC], says Huxlin. The primary visual cortex is the gateway to the rest of the brain for most of the visual information that comes through the eyes, Huxlin said. That area passes visual information along to dozens of other parts of the brain, which then makes sense of the information, allowing people to see [Bloomberg].
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Who says shoot-’em-up video games are a waste of time? A new study has found that playing action video games dramatically increases the players’ ability to detect subtle shades of gray. Says lead Daphne Bavelier: “Normally, improving contrast sensitivity means getting glasses or eye surgery — somehow changing the optics of the eye…. [But when] people play action games, they’re changing the brain’s pathway responsible for visual processing. These games push the human visual system to the limits and the brain adapts to it,” Bavelier said [Reuters]. The study also found that more sedate games that don’t require precisely aimed actions, like The Sims 2, do not confer a similar benefit.
The researchers say that eye doctors could one day write prescriptions for Nintendo: The finding raises the prospect that people with amblyopia, which affects contrast perception, could be treated with games. A trial has begun to test that theory. Amblyopia, sometimes known as “lazy eye”, affects around 3 per cent of people in western populations and happens when the brain fails to correctly register signals from one eye [New Scientist]. Contrast sensitivity, which is crucial for activities such as night driving, is also one of the first elements of vision to be affected by aging.
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