Posts tagged vision
Articles and news from the latest research reports.
Nearly 100 years after a British neurologist first mapped the blind spots caused by missile wounds to the brains of soldiers, Perelman School of Medicine researchers at the University of Pennsylvania have perfected his map using modern-day technology. Their results create a map of vision in the brain based upon an individual’s brain structure, even for people who cannot see. Their result can, among other things, guide efforts to restore vision using a neural prosthesis that stimulates the surface of the brain. The study appears in the latest issue of Current Biology, a Cell Press journal.
When Your Eyes Tell Your Hands What to Think: You’re Far Less in Control of Your Brain Than You Think
You’ve probably never given much thought to the fact that picking up your cup of morning coffee presents your brain with a set of complex decisions. You need to decide how to aim your hand, grasp the handle and raise the cup to your mouth, all without spilling the contents on your lap.
A new Northwestern University study shows that, not only does your brain handle such complex decisions for you, it also hides information from you about how those decisions are made.
"Our study gives a salient example," said Yangqing ‘Lucie’ Xu, lead author of the study and a doctoral candidate in psychology at Northwestern. "When you pick up an object, your brain automatically decides how to control your muscles based on what your eyes provide about the object’s shape. When you pick up a mug by the handle with your right hand, you need to add a clockwise twist to your grip to compensate for the extra weight that you see on the left side of the mug.
"We showed that the use of this visual information is so powerful and automatic that we cannot turn it off. When people see an object weighted in one direction, they actually can’t help but ‘feel’ the weight in that direction, even when they know that we’re tricking them," Xu said.
Surgeons at UC Davis Medical Center have successfully implanted a new telescope implant in the eye of a patient with end-stage age-related macular degeneration (AMD), the most advanced form of the disease and a leading cause of blindness in older Americans.
The device, approved by the Food and Drug Administration in 2010, is the only medical/surgical option available that restores a portion of vision lost to the disease. UC Davis Health System’s Eye Center, in collaboration with the Society for the Blind, is one of the few in California and the nation to offer the innovative procedure.
Duchess the elephant has UK’s first cataract op
Zookeepers are carefully monitoring an elephant who was the first in the UK to undergo an eye operation, to discover how much of her sight has returned.
Duchess was said to be recovering well after yesterday’s operation to remove a cataract from her left eye.
Paignton Zoo’s 42-year-old African elephant had her right eye removed in 2011 because of glaucoma, and has lately become practically blind.
Neil Bemment, curator of mammals and director of operations at the zoo, said staff had high hopes for the operation’s success. “It couldn’t have gone better,” he said. “She went down very smoothly under the anaesthetic and the operation went as well as we could hope.”
Mr Bemment said Duchess was still “disorientated” from the procedure and was being kept out of view with plenty of reassurance from staff.
"Her sight had deteriorated to the point where she could only tell the difference between light and shade," Mr Bemment said. "We’re hoping that his will restore her sight for most distances. She won’t be able to read about herself in the newspaper, but we’re hopeful that she will be more familiar in her surroundings."
(Source: thisisdevon.co.uk)
Vision cells, not brain, to blame for colour blindness
The real culprits of colour blindness are vision cells rather than unusual wiring in the eye and brain, recent research has shown.
The discovery brings scientists a step closer to restoring full colour vision for people who are colour blind – a condition that affects close to two million Australians, says Professor Paul Martin from The Vision Centre and The University of Sydney.
It may also help pave the way for an answer to one of the most common causes of blindness – age-related macular degeneration (AMD), which accounts for half of the legal blindness cases in Australia.
“There are millions of cones in our eyes – vision cells that pick up bright light and allow us to see colour,” Prof. Martin says. “They are nicknamed red, green and blue cones because they are sensitive to different wavelengths of light.
“We now know that in the macular region of the eye, each cone has its own ’private line’ into the optic nerve and the brain. Just as a painter can mix from three tubes of paint to produce a wide and vivid palette, our brain uses the ‘private lines’ from the three cone types to create thousands of colour sensations.
Scientists previously thought that full colour vision depends on specialised nerve wiring in the eye and brain, but animal studies show that the wiring is identical for monkeys whether they have normal or abnormal colour vision, Prof. Martin says.
“This tells us that there’s nothing wrong in the brain – it’s only working with the signals that it receives on the ‘private lines’,” he says. “So the only difference in normal and abnormal colour vision is caused by the first stage of sight, which points to faulty cones. Either they have failed to develop, or else they are picking up abnormal wavelengths.
“Now that we know faulty wiring isn’t the cause, we can concentrate on fixing the cones, which are controlled by genes – and thus prone to mutation or mistakes during cell replication. There are already promising results from gene therapy as a way to restore full colour vision in colour blind monkeys.”
“While we have still have some way to go, the benefits of this gene therapy – if successful – can potentially extend beyond providing complete colour vision,” he says.
“If we can get these genes to work in human eyes, it means that the same approach might be possible for other visual problems – including blinding diseases such as macular degeneration.”
"In macular degeneration, energy supplies to the macula can’t keep up with demand. So the ‘private line’ system must be very energy-intensive. Gene therapy could be used to turn down the cones’ energy demand, or to increase energy supply from supporting cells to cone cells,” Prof. Martin says.
“Together with clinical researchers at the Save Sight Institute, we are now working hard to find out exactly how many ‘private lines’ there are in humans. That can point us to where energy demand is highest and we can target gene therapy to the right place.
"So animal research on ‘private lines’ for colour vision has given new clues for understanding one of the most important visual diseases – macular degeneration – in humans."
(Source: scinews.com.au)
Teaching the Blind to Find Their Way by Playing Video Games
Computer based video games are receiving great interest as a means to learn and acquire new skills. As a novel approach to teaching navigation skills in the blind, we have developed Audio-based Environment Simulator (AbES); a virtual reality environment set within the context of a video game metaphor. Despite the fact that participants were naïve to the overall purpose of the software, we found that early blind users were able to acquire relevant information regarding the spatial layout of a previously unfamiliar building using audio based cues alone. This was confirmed by a series of behavioral performance tests designed to assess the transfer of acquired spatial information to a large-scale, real-world indoor navigation task. Furthermore, learning the spatial layout through a goal directed gaming strategy allowed for the mental manipulation of spatial information as evidenced by enhanced navigation performance when compared to an explicit route learning strategy. We conclude that the immersive and highly interactive nature of the software greatly engages the blind user to actively explore the virtual environment. This in turn generates an accurate sense of a large-scale three-dimensional space and facilitates the learning and transfer of navigation skills to the physical world.
The eyes may be windows into the soul, but following their movement also could allow doctors to make quick, accurate diagnoses for disorders like autism, schizophrenia, or attention deficit hyperactivity disorder, various research projects suggest.
Eye tracking, which records where subjects focus when watching visual displays, could diagnose brain disorders more accurately than subjective questionnaires or medical examinations do, researchers say. Exams are expensive and time-consuming, and subjective tests have been known to wrongly identify healthy people or misdiagnose disorders.
To make sense of all that people see, the brain filters huge amounts of visual information, fills in gaps and focuses on certain objects. That complex task uses many mental circuits, so differences in what people choose to look at ― differences so subtle that only a computer can spot them ― could provide unprecedented insight into common neurological problems.
EnChroma glasses designed to compensate for color-blindness
While many people may think that being color blind means seeing everything in black-and-white, such a condition is in fact quite rare. Instead, the majority of people who are classified as color blind are capable of color vision, but they have difficulty distinguishing red and green as distinct colors. EnChroma’s Cx sunglasses are designed to help in these cases, by selectively reducing the transmission of given wavelengths of light, thus allowing red and green to stand out.
The key to the sunglasses’ performance is a proprietary coating on the lenses. Said to be harder and more scratch-resistant than glass, it can be tweaked in production to filter certain wavelengths that cause “color confusion.” The result is an improved signal-to-noise ratio in the perception of colors, in which red and green don’t just appear as variations of yellowy-brown – as an example.
Depending on their specific type of red-green color vision deficiency, users can choose between two different models of the sunglasses, designed to filter different wavelengths of light. There are also models that simply boost the intensity of all colors (for use by normally-sighted users), and that boost colors while also blocking UV rays.
People who are completely incapable of seeing any colors will unfortunately not be helped by any of the models. Also, because they are sunglasses, their color correction feature only works in bright light.
EnChroma’s Cx sunglasses should be available as of the middle of next month. Expect to pay at least US$800 for a complete set of glasses, or $700 for the lenses alone.
Researchers identify mechanism that leads to diabetes, blindness
The rare disorder Wolfram syndrome is caused by mutations in a single gene, but its effects on the body are far reaching. The disease leads to diabetes, hearing and vision loss, nerve cell damage that causes motor difficulties, and early death.
Now, researchers at Washington University School of Medicine in St. Louis, the Joslin Diabetes Center in Boston and the Novartis Institutes for BioMedical Research report that they have identified a mechanism related to mutations in the WFS1 gene that affects insulin-secreting beta cells. The finding will aid in the understanding of Wolfram syndrome and also may be important in the treatment of milder forms of diabetes and other disorders.
The study is published online in the journal Nature Cell Biology
“We found something we didn’t expect,” says researcher Fumihiko Urano, MD, PhD, associate professor of medicine in Washington University’s Division of Endocrinology, Metabolism and Lipid Research. “The study showed that the WFS1 gene is crucial to producing a key molecule involved in controlling the metabolic activities of individual cells.” That molecule is called cyclic AMP (cyclic adenosine monophosphate).
Insulin-secreting beta cells in the pancreas (above) cannot make enough cyclic AMP in patients with Wolfram syndrome. As a result, the pancreas produces and secretes less insulin, and the cells eventually die.
In insulin-secreting beta cells in the pancreas, for example, cyclic AMP rises in response to high blood sugar, causing those cells to produce and secrete insulin.
“I would compare cyclic AMP to money,” Urano says. “You can’t just take something you make to the store and use it to buy food. First, you have to convert it into money. Then, you use the money to buy food. In the body, external signals stimulate a cell to make cyclic AMP, and then the cyclic AMP, like money, can ‘buy’ insulin or whatever else may be needed.”
The reason patients with Wolfram syndrome experience so many problems, he says, is because mutations in the WFS1 gene interfere with cyclic AMP production in beta cells in the pancreas.
“In patients with Wolfram syndrome, there is no available WFS1 protein, and that protein is key in cyclic AMP production,” he explains. “Then, because levels of cyclic AMP are low in insulin-secreting beta cells, those cells produce and secrete less insulin. And in nerve cells, less cyclic AMP can lead to nerve cell dysfunction and death.”
By finding that cyclic AMP production is affected by mutations in the WFS1 gene, researchers now have a potential target for understanding and treating Wolfram syndrome.
“I don’t know whether we can find a way to control cyclic AMP production in specific tissues,” he says. “But if that’s possible, it could help a great deal.”
Meanwhile, although Wolfram syndrome is rare, affecting about 1 in 500,000 people, Urano says the findings also may be important to more common disorders.
“It’s likely this mechanism is related to diseases such as type 2 diabetes,” he says. “If a complete absence of the WFS1 protein causes Wolfram syndrome, perhaps a partial impairment leads to something milder, like diabetes.”
(Source: news.wustl.edu)
Animation of bionic eye being developed in Melbourne, Australia by the Bionic Vision Australia consortium.