Chapter 10. Vision: From Eye to Brain

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Scientists at the National Eye Institute (NEI) have found that neurons in the superior colliculus, an ancient midbrain structure found in all vertebrates, are key players in allowing us to detect visual objects and events. This structure doesn’t help us recognize what the specific object or event is; instead, it’s the part of the brain that decides something is there at all. By comparing brain activity recorded from the right and left superior colliculi at the same time, the researchers were able to predict whether an animal was seeing an event. The findings were published today in the journal Nature Neuroscience. NEI is part of the National Institutes of Health. Perceiving objects in our environment requires not just the eyes, but also the brain’s ability to filter information, classify it, and then understand or decide that an object is actually there. Each step is handled by different parts of the brain, from the eye’s light-sensing retina to the visual cortex and the superior colliculus. For events or objects that are difficult to see (a gray chair in a dark room, for example), small changes in the amount of visual information available and recorded in the brain can be the difference between tripping over the chair or successfully avoiding it. This new study shows that this process – deciding that an object is present or that an event has occurred in the visual field – is handled by the superior colliculus. “While we’ve known for a long time that the superior colliculus is involved in perception, we really wanted to know exactly how this part of the brain controls the perceptual choice, and find a way to describe that mechanism with a mathematical model,” said James Herman, Ph.D., lead author of the study.

Keyword: Vision
Link ID: 25723 - Posted: 11.27.2018

National Institutes of Health scientists and their colleagues have found evidence of the infectious agent of sporadic Creutzfeldt-Jakob disease (CJD) in the eyes of deceased CJD patients. The finding suggests that the eye may be a source for early CJD diagnosis and raises questions about the safety of routine eye exams and corneal transplants. Sporadic CJD, a fatal neurodegenerative prion disease of humans, is untreatable and difficult to diagnose. Prion diseases originate when normally harmless prion protein molecules become abnormal and gather in clusters and filaments in the body and brain. Scientists hope that early diagnosis of prion and related diseases—such as Alzheimer’s, Parkinson’s and dementia with Lewy bodies—could lead to effective treatments that slow or prevent these diseases. Scientists from NIH’s National Institute of Allergy and Infectious Diseases (NIAID) collaborated on the research with colleagues from the University of California at San Diego and UC-San Francisco. About 40 percent of sporadic CJD patients develop eye problems that could lead to an eye exam, meaning the potential exists for the contamination of eye exam equipment designed for repeat use. Further, cadaveric corneal transplants from undiagnosed CJD patients have led to two probable and three possible cases of disease transmission, the researchers say. Previous studies have shown that the eyes of CJD patients contain infectious prions, though the distribution of prions among the various components of the eye was not known. To address this question, the scientists recruited 11 CJD patients who agreed to donate their eyes upon death. The researchers found evidence of prion infection throughout the eyes of all 11 deceased patients using real time quaking-induced conversion (RT-QuIC), a highly sensitive test NIAID scientists developed that detects prion seeding activity in a sample as evidence of infection.

Keyword: Prions; Vision
Link ID: 25706 - Posted: 11.21.2018

By Michael Price Patient BAA, who is 35, lost her sight when she was 27. She can still detect light and dark, but for all intents and purposes, she is blind. Now, she—and other formerly sighted people—may one day regain a limited form of vision using electrodes implanted in the brain. In a new study, such electrodes caused parts of BAA’s and other people’s visual cortexes to light up in specific patterns, allowing them to see shapes of letters in their mind’s eyes. The work is a step forward in a field that emerged more than 40 years ago but has made relatively little progress. The findings suggest technical ways to stimulate images in the brain “are now within reach,” says Pieter Roelfsema, a neuroscientist who directs the Netherlands Institute for Neuroscience in Amsterdam and wasn’t involved in the work. Research to electrically spur blind people’s brains to see shapes began in the 1970s, when biomedical researcher William Dobelle, then at The University of Utah in Salt Lake City, first implanted electrodes in the brain to stimulate the visual cortex. Typically, the rods and cones in retinas translate light waves into neural impulses that travel to the brain. Specialized layers of cells there, known as the visual cortex, process that information for the rest of the brain to use. Dobelle’s implants took advantage of a phenomenon known as retinal mapping. The visual field—the plane of space you see when you look out into the world—roughly maps onto a segment of the visual cortex. By electrically stimulating parts of this brain map, Dobelle could cause flashes of light called phosphenes to appear in the minds of people who were blind, but who had experienced at least a few years of vision. By stimulating different electrodes, he could get phosphenes to flash in different parts of a person’s visual field. © 2018 American Association for the Advancement of Science

Keyword: Vision; Robotics
Link ID: 25697 - Posted: 11.17.2018

Nicola Davis Children should be encouraged to spend time outdoors to reduce their risk of becoming shortsighted, experts have said. Shortsightedness is rising around the world, with the condition said to have reached epidemic proportions in east Asia: estimates suggest about 90% of teenagers and young adults in China have the condition. While genetics are thought to play a large role in who ends up shortsighted – a condition that is down to having an overly long eyeball – research also suggests environmental factors are important. Several studies have found children who spend more time outdoors have a lower risk of myopia. While some report that looking into the distance could be important, others say exposure to outdoor light is key. Experts say they have found new factors, and confirmed others, which could affect a child’s risk of becoming shortsighted. These include playing computer games, being born in the summer and having a more highly educated mother. “There is not much you can do about when your child is born … but periods indoors doing indoor activities does increase your risk of myopia,” said Katie Williams, an author of the study by King’s College London. “A healthy balance of time outdoors and a balance during early education is important.” Writing in the British Journal of Ophthalmology, Williams and her colleagues report how they used data from the twins early development study, which followed children born in England and Wales between 1994 and 1996. The project tracked their development, behaviour and education through questionnaires and tests, and studied their genetics. © 2018 Guardian News and Media Limited

Keyword: Vision; Development of the Brain
Link ID: 25653 - Posted: 11.07.2018

By James Gorman If you love spiders, you will really love jumping spiders. (If you hate spiders, try reading this article on dandelions.) O.K., if you’re still here, jumping spiders are predators that stalk their prey and leap on them, like a cat. They are smart, agile and have terrific eyesight. It has been clear for a long time that their vision is critical to the way they hunt, and to the accuracy of their leaps. But a lot has remained unknown about the way their eyes work together. To find out more, Elizabeth Jakob, a spider biologist at the University of Massachusetts, led a team of researchers from the United States, Kenya and New Zealand in an investigation of spider vision. The first step was getting a custom-built spider eye tracker, similar to ones used on humans, to follow a spider’s gaze. Actually, Dr. Jakob had two made, probably the only two in the world. She has one and her colleagues in New Zealand have the other. Jumping spiders have eight eyes. Two big eyes, right in the center of what you might call the spider’s forehead, are the principal ones, and they pick up detail and color. Of the other three pairs, a rear set looks backward, a middle set is as yet a bit of a mystery, and the foremost detect motion. The lenses of the main eyes are attached by flexible tubes to retinas. A camera was set up to look down those tubes and see the activity of the retinas, which look a bit like boomerangs. The inside of the spider’s head was lit by ultraviolet light, which penetrates the outer carapace. But as accurate as the main eyes are, they only see what is in front of them. If they had to find prey, it would be like using a narrow flashlight beam to explore a dark room. Not very efficient. The researchers found that the front pair of secondary eyes, the motion detectors, tell the main pair of eyes where to look. When they were painted over temporarily and the spider was presented with moving images, it had no idea where to look. © 2018 The New York Times Company

Keyword: Vision; Evolution
Link ID: 25648 - Posted: 11.06.2018

Amanda B. Keener If Leonardo da Vinci had a good eye doctor, he might not have become such a great artist. At least that’s what an analysis of paintings and sculptures believed to be modeled after da Vinci suggests. Visual neuroscientist Christopher Tyler of the City University of London examined six pieces of art, including Salvator Mundi and Vitruvian Man. Five of the pieces depict an eye misalignment consistent with a disorder called exotropia that can interfere with three-dimensional vision, Tyler reports online October 18 in JAMA Ophthalmology. Exotropia, in which one eye turns slightly outward, is one of several eye disorders collectively called strabismus. Today, strabismus, which affects 4 percent of people in the United States, is treated with special glasses, eye patches or surgery. Tyler calculated the differences in eye alignment using the same sorts of measurements that an optometrist does when tailoring a pair of glasses. Most of the portraits showed the eyes misaligned, but Vitruvian Man by da Vinci himself did not. As a result, da Vinci may have had intermittent exotropia, present only some of the time and perhaps controllable, Tyler suspects. “The person [with intermittent exotropia] can align their eyes and see in 3-D, but if they’re inattentive or tired, the eye may droop,” he says. If da Vinci could control his exotropia, Tyler speculates that it would have been an artistic advantage. “The artist’s job is to paint on a 2-D surface,” he says. “This can be difficult when you view the world three-dimensionally.” Both eyes need to focus on the same subject for 3-D vision. Many artists shut one eye when viewing their subjects to more easily translate details into two dimensions. But with intermittent exotropia, da Vinci could have switched from 3-D to 2-D and back again with ease. |© Society for Science & the Public 2000 - 201

Keyword: Vision
Link ID: 25596 - Posted: 10.22.2018

Sara Reardon Cuttlefish are masters at altering their appearance to blend into their surroundings. But the cephalopods can no longer hide their inner thoughts, thanks to a technique that infers a cuttlefish’s brain activity by tracking the ever-changing patterns on its skin. The findings, published in Nature on 17 October1, could help researchers to better understand how the brain controls behaviour. The cuttlefish (Sepia officinalis) camouflages itself by contracting the muscles around tiny, coloured skin cells called chromatophores. The cells come in several colours and act as pixels across the cuttlefish’s body, changing their size to alter the pattern on the animal’s skin. The cuttlefish doesn’t always conjure up an exact match for its background. It can also blanket itself in stripes, rings, mottles or other complex patterns to make itself less noticeable to predators. “On any background, especially a coral reef, it can’t look like a thousand things,” says Roger Hanlon, a cephalopod biologist at the Marine Biological Laboratory in Chicago, Illinois. “Camouflage is about deceiving the visual system.” To better understand how cuttlefish create these patterns across their bodies, neuroscientist Gilles Laurent at the Max Planck Institute for Brain Research in Frankfurt, Germany, and his collaborators built a system of 20 video cameras to film cuttlefish at 60 frames per second as they swam around their enclosures. The cameras captured the cuttlefish changing colour as they passed by backgrounds such as gravel or printed images that the researchers placed in the tanks. © 2018 Springer Nature Limited.

Keyword: Vision; Brain imaging
Link ID: 25589 - Posted: 10.18.2018

By Carolyn Y. Johnson Kiara Eldred sometimes compares her nine-month-long scientific experiments, growing tiny human retinas in a laboratory dish, to raising children. Eldred, a graduate student at Johns Hopkins University, starts by growing thousands of stem cells and feeding them nutrients and chemicals that will steer them to develop into the retina, the part of the eye that translates light into the signals that lead to vision. After two weeks of painstaking cultivation, those cells typically generate 20 to 60 tiny balls of cells, called retinal organoids. As they mature, these nascent retinas get dirty and slough off lots of cells, so they also need to be washed off when they’re fed every other day — at least for the first month and a half. After nine months of assiduous care, Eldred has a batch of miniature human retinas that respond to light, are about two millimeters in diameter and are shaped like a tennis ball cut in half. But growing the organoids is only the first step. In a new study in the journal Science, Eldred and colleagues described using this system to understand a fundamental question about vision that has remained surprisingly mysterious: How does color vision develop? © 1996-2018 The Washington Post

Keyword: Vision; Development of the Brain
Link ID: 25565 - Posted: 10.12.2018

Doris Tsao is a neuroscientist who uses brain imaging technology, electrical recording techniques, and mathematical modeling. Though Tsao has explored several aspects of visual processing, such as the perception of depth and color, her most notable line of research has focused on uncovering the fundamental neural principles that underlie one of the brain’s most highly specialized and socially important tasks: recognizing a face. Prior neuroscientific research has identified regions in the inferior temporal cortex of monkeys that are particularly responsive to faces. These earlier studies, however, shed little light on how face-responsive cells within these regions might be organized and integrated into a system. Early in her career, Tsao confirmed with functional magnetic resonance imaging (fMRI) that the visual cortex of the macaque monkey shows face-selective activation in six small “patches” in each hemisphere of the brain. She then used data from fMRI brain scans as a map to guide the placement of single-neuron, electrical recording probes, which demonstrated that certain neurons display highly attuned sensitivity to faces, but not to other categories of objects, and that different patches across the brain’s cortex are integrated in a network dedicated to the visual processing of faces. Through other elegantly designed experiments, Tsao showed that the sensitivity of specific neurons can be further analyzed by measuring their responses to cartoon representations of faces with subtle variations in features and that certain features, such as facial shape and inter-eye distance, elicit particularly frequent and robust responses. © 2018 John D. and Catherine T. MacArthur Foundation

Keyword: Vision
Link ID: 25532 - Posted: 10.05.2018

By Kelly Servick PHILADELPHIA, PENNSYLVANIA—While artificial intelligence (AI) has been busy trouncing humans at Go and spawning eerily personable Alexas, some neuroscientists have harbored a different hope: that the types of algorithms driving those technologies can also yield some insight into the squishy, wet computers in our skulls. At the Conference on Cognitive Computational Neuroscience here this month, researchers presented new tools for comparing data from living brains with readouts from computational models known as deep neural networks. Such comparisons might offer up new hypotheses about how humans process sights and sounds, understand language, or navigate the world. “People have fantasized about that since the 1980s,” says Josh McDermott, a computational neuroscientist at the Massachusetts Institute of Technology (MIT) in Cambridge. Until recently, AI couldn’t come close to human performance on tasks such as recognizing sounds or classifying images. But deep neural networks, loosely inspired by the brain, have logged increasingly impressive performances, especially on visual tasks. That “brings the question back to mind,” says neuroscientist Chris Baker of the National Institute of Mental Health in Bethesda, Maryland. Deep neural networks work by passing information between computational “nodes” that are arranged in successive layers. The systems hone skills on huge sets of data; for networks that classify images, that usually means collections of labeled photos. Performance improves with feedback as the systems repeatedly adjust the strengths of the connections between nodes. © 2018 American Association for the Advancement of Science

Keyword: Attention; Vision
Link ID: 25466 - Posted: 09.18.2018

By Emily Underwood On a moonless night, the light that reaches Earth is a trillion–fold less than on a sunny day. Yet most mammals still see well enough to get around just fine—even without the special light-boosting membranes in the eyes of cats and other nocturnal animals. A new study in mice hints at how this natural night vision works: Motion-sensing nerve cells in the retina temporarily change how they wire to each other in dark conditions. The findings might one day help visually impaired humans, researchers say. Scientists already knew a bit about how night vision works in rabbits, mice, humans, and other mammals. Mammalian retinas can respond to “ridiculously small” numbers of photons, says Joshua Singer, a neuroscientist at the University of Maryland in College Park who was not involved in the new study. A single photon can activate a light-sensitive cell known as a rod cell in the retina, which sends a minute electrical signal to the brain through a ganglion cell. One kind of ganglion cell specializes in motion detection—a vital function if you’re a mouse being hunted by an owl, or a person darting to avoid oncoming traffic. Some of these direction-selective ganglion cells (DSGCs) get excited only when an object is moving upward. Others fire only when objects are moving down, or to the left or right. Together, the cells decide where an object is headed and relay that information to the brain, which decides how to act. © 2018 American Association for the Advancement of Science

Keyword: Vision; Evolution
Link ID: 25449 - Posted: 09.14.2018

By Ben Guarino A blight of bad eyesight plagues urban centers in China and other East Asian countries. In Hong Kong and Singapore, the rate of myopia, or nearsightedness, is as high as 90 percent in young adults. Though things aren't as blurry in the United States — about a third of the population has trouble seeing distant objects — rates have doubled since the 1970s. If current trends continue, half of the world could be myopic by 2050. China blames video games for the eyeglass epidemic and recently took them to task. The state-run Xinhua News Agency wrote this week that the "vision health of our country’s young people has always been of great concern" to Xi Jinping, the Communist Party general secretary and China's president. Chinese media distributors, the New York Times reported Friday, will limit the number of new games approved for sale. By singling out video games, China has taken a somewhat "extreme stance," according to Aaron M. Miller, a pediatric ophthalmologist and a clinical spokesman for the American Academy of Ophthalmology. "There's not a direct correlation or a clear relationship between video games, screen time and nearsightedness development." The scientific literature can offer only a fuzzy picture of myopia's causes. Diet and genes influence myopia; myopic parents are more likely to have myopic children. Behaviors can play a role, too. Some ophthalmologists look to activities lumped together under a term called "near-work" — any prolonged focus on a nearby object, as when reading, checking phones, studying and, yes, watching screens. Researchers have observed higher rates of myopia in college students, post-literate societies and, in one study, people who frequently use microscopes. © 1996-2018 The Washington Post

Keyword: Vision
Link ID: 25412 - Posted: 09.04.2018

By Bahar Gholipour Milena Canning can see steam rising from a coffee cup but not the cup. She can see her daughter’s ponytail swing from side to side, but she can’t see her daughter. Canning is blind, yet moving objects somehow find a way into her perception. Scientists studying her condition say it could reveal secrets about how humans process vision in general. Canning was 29 when a stroke destroyed her entire occipital lobe, the brain region housing the visual system. The event left her sightless, but one day she saw a flash of light from a metallic gift bag next to her. Her doctors told her she was hallucinating. Nevertheless, “I thought there must be something happening within my brain [allowing me to see],” she says. She went from doctor to doctor until she met Gordon Dutton, an ophthalmologist in Glasgow, Scotland. Dutton had encountered this mystery before—in a 1917 paper by neurologist George Riddoch describing brain-injured World War I soldiers. To help enhance Canning’s motion-based vision, Dutton prescribed her a rocking chair. Canning is one of a handful of people who have been diagnosed with the “Riddoch phenomenon,” the ability to perceive motion while blind to other visual stimuli. Jody Culham, a neuroscientist at Western University in Ontario, and her colleagues launched a 10-year investigation into Canning’s remarkable vision and published the results online in May in Neuropsychologia. The team confirmed that Canning was able to detect motion and its direction. She could see a hand moving toward her, but she could not tell a thumbs-up from a thumbs-down. She was also able to navigate around obstacles, reach and grasp, and catch a ball thrown at her. © 2018 Scientific American

Keyword: Attention; Vision
Link ID: 25409 - Posted: 09.01.2018

By Raymond Zhong BEIJING — It started this week with a call to action from China’s leader, Xi Jinping. Too many of the country’s children need glasses, he said, and the government was going to do something about it. It ended on Friday with billions of dollars being wiped from the market value of the world’s largest video game company. New controls on online games were among Chinese authorities’ recommendations for reducing adolescent nearsightedness on Thursday, sending shares in the country’s leading game publisher, Tencent, tumbling the next day. Shares of Japanese game makers like Capcom, Konami and Bandai Namco also fell on Friday, a sign of the size and importance of the Chinese market. The sell-off is the latest in a series of government-related stumbles for Tencent, one of the world’s largest technology companies. Chinese state media has blamed video games for causing young people to become addicted, lowering their grades and worse. An incident last year, in which a 17-year-old in the southern city of Guangzhou died after playing a smartphone game for 40 hours straight, received wide attention. As the biggest game distributor in the world’s biggest game market, Tencent has grown fantastically rich in recent years. It has bought up game developers around the world, including the makers of influential titles such as League of Legends and Clash of Clans. It owns a stake in Epic Games, creator of the international blockbuster Fortnite. Back at home, Tencent also operates China’s most popular messaging app, WeChat, and processes a big chunk of the smartphone payments that are now used to make transactions of all kinds in the country. But over the last year, Tencent's hugely profitable game business has come under fire as Beijing takes a more forceful approach to guiding Chinese culture — a reminder of the state’s growing role in deciding the fortunes of the country’s largest and most innovative private companies. © 2018 The New York Times Company

Keyword: Vision
Link ID: 25406 - Posted: 08.31.2018

Scientists funded by the National Eye Institute (NEI) report a novel gene therapy that halts vision loss in a canine model of a blinding condition called autosomal dominant retinitis pigmentosa (adRP). The strategy could one day be used to slow or prevent vision loss in people with the disease. NEI is part of the National Institutes of Health. “We’ve developed and shown proof-of-concept for a gene therapy for one of the most common forms of retinitis pigmentosa,” said William Beltran, D.V.M., Ph.D., of the University of Pennsylvania School of Veterinary Medicine, Philadelphia, a lead author of the study, which appears online today in the Proceedings of the National Academy of Sciences. Retinitis pigmentosa refers to a group of rare genetic disorders that damage light-sensing cells in the retina known as photoreceptors. Rod photoreceptor cells enable vision in low light and require a protein called rhodopsin for their light-sensing ability. People with adRP caused by mutations in the rhodopsin gene usually have one good copy of the gene and a second, mutated copy that codes for an abnormal rhodopsin protein. The abnormal rhodopsin is often toxic, slowly killing the rod cells. As the photoreceptors die, vision deteriorates over years or decades. Scientists have identified more than 150 rhodopsin mutations that cause adRP, challenging efforts to develop effective therapies. Beltran generated a gene therapy construct that knocks down the rod cells’ ability to produce rhodopsin using a technology known as shRNA (short-hairpin RNA) interference. Gene therapy introduces genetic material, like shRNA, into cells to compensate for abnormal genes or to make a beneficial protein. Often adapted from viruses, vectors are engineered to effectively deliver this genetic material into cells without causing disease.

Keyword: Vision; Genes & Behavior
Link ID: 25358 - Posted: 08.21.2018

Genevieve Fox Paola Peretti is losing her eyesight and she wouldn’t have it any other way. When she was 14, she became very short-sighted, virtually overnight. Three years later came the diagnosis of Stargardt macular dystrophy, a degenerative disease that destroys central vision, damages colour perception and results in blindness. Two years ago, finding herself in a place of both “desperation and hope,” the 32-year-old Italian language teacher and debut novelist decided to step out from the shadow of her hereditary condition, which she only ever aired with her family, and confront her fear of the dark. The Distance Between Me and the Cherry Tree is the result: a captivating, wise and highly visual children’s novel about living in the face of fear. Its heroine, nine-year-old Mafalda, also has Stargardt disease. A bewitching, brave little girl, she will lose her sight completely within six months, as Peretti was expecting to do at some unspecified point in her own life when she began the novel. The eponymous cherry tree is next to Mafalda’s school. Each day, she has to get closer to it before it comes into focus. As her short-sightedness increases, so does her fear of the future. “She is losing her life as she knows it,” says Peretti, who explains that she herself can see “half of what other people see”. Mafalda has blank patches in both eyes, and they get bigger. Peretti has a blank patch in her right eye. I am seated a couple of feet from her as we talk in her publisher’s office. She says I am partially blurred. © 2018 Guardian News and Media Limited

Keyword: Vision; Emotions
Link ID: 25352 - Posted: 08.20.2018

By Kelly Servick Nestled in the backs of our eyes, there are cells that might be able to repair damage from some vision-impairing diseases. But so far, scientists haven’t managed to kick them into gear. Now, a team of researchers claims to have prompted these cells, called Müller glia, to regenerate one type of light receptor cell in the eyes of mice. According to their study, published today in Nature, these new cells could detect incoming light and network with other cells in the eye to relay signals to the brain, a potential step toward reversing certain genetic eye conditions and injuries. But others are skeptical of that claim and argue the signals could have come from existing light-sensing cells in the eye—not new ones. “Nobody more than me wants this to be true,” says Seth Blackshaw, a neuroscientist at Johns Hopkins University’s School of Medicine in Baltimore, Maryland, “but I have serious concerns about this study.” The new work is part of a long effort to regenerate photoreceptors, neurons in the retina that transform incoming light into electrical signals. Cone receptors are responsible for our daytime vision and perception of colors, and the more sensitive rod receptors enable vision in low light. The destruction of these cells—or of the retinal ganglion cells that transmit their signals to the brain—can diminish vision and even cause blindness. © 2018 American Association for the Advancement of Science

Keyword: Vision; Glia
Link ID: 25340 - Posted: 08.16.2018

Scientists say they have found how blue light from smartphones, laptops and other digital devices damages vision and can speed up blindness. Research by the University of Toledo in the US has revealed that prolonged exposure to blue light triggers poisonous molecules to be generated in the eye’s light-sensitive cells that can cause macular degeneration – an incurable condition that affects the middle part of vision. Blue light, which has a shorter wavelength and more energy compared with other colours, can gradually cause damage to the eyes. Dr Ajith Karunarathne, an assistant professor in the university’s department of chemistry and biochemistry, said: “We are being exposed to blue light continuously and the eye’s cornea and lens cannot block or reflect it. “It’s no secret that blue light harms our vision by damaging the eye’s retina. Our experiments explain how this happens, and we hope this leads to therapies that slow macular degeneration, such as a new kind of eye drop.” Macular degeneration, which affects around 2.4% of the adult population in the UK, is a common condition among those in their 50s and 60s that results in significant vision loss. It is caused by the death of photoreceptor, ie light-sensitive cells, in the retina. Age-related macular degeneration is the leading cause of blindness in the US and while it does not cause total blindness, it can make everyday activities such as reading and recognising faces difficult. © 2018 Guardian News and Media Limite

Keyword: Vision
Link ID: 25315 - Posted: 08.10.2018

By Susana Martinez-Conde The house cricket (Acheta domesticus) walked around the arena comfortably, certain of its surroundings. It looked about, perhaps hoping for food or mates, ignoring the scattered, browning, dead leaves. On previous visits to the arena, the cricket had been wary of the dead leaves, not knowing what to make of them. Then, after a prudent interval, it had ventured to feel them with its segmented antennae—tentatively at first, and later with growing confidence. Once the cricket determined the leaves were neither edible nor harmful, it quickly lost interest in them. Now it rarely bothered to explore the leaves, but took no great pains to avoid them either. The cricket’s conviction about the safety of the leaves was its fatal mistake: on this visit, one seemingly dead leaf lying on the arena was no such, but a masquerading ghost mantis (Phyllocrania paradoxa) waiting in ambush. Unaware of the concealed peril, the cricket drew ever closer to the predator. That’s when the mantis struck forth, grasping the cricket by one of its long jumping legs. As the cricket struggled against the mantis’ clutch, the predator started to feed. Dr John Skelhorn, Lecturer in Animal Cognition, has witnessed dozens of similar life-and-death encounters in his lab at Newcastle University’s Institute of Neuroscience. Skelhorn and his colleagues previously found that some animals masquerade as inanimate, inedible objects, to look less appealing to potential predators. Some examples include the orb web spider (Cyclosa ginnaga) and the larva of the giant swallowtail butterfly (Papilio cresphontes), both of which masquerade as bird droppings, and the larva of the feathered thorn moth (Selenia dentaria), which masquerades as a twig. © 2018 Scientific American

Keyword: Vision; Evolution
Link ID: 25299 - Posted: 08.06.2018

By Donald G. McNeil Jr. GETA, Nepal — Fifteen years ago, Shiva Lal Rana walked 20 miles to Geta Eye Hospital to ask doctors to pluck out all his eyelashes. Trachoma, a bacterial infection, had swollen and inverted his eyelids. With every blink, his lashes raked his corneas. “The scratching hurt my eyes so much I could barely go out in the sun to plow,” he said. “I was always rubbing them.” Worse, he feared the fate that others with the infection had suffered. The tiny scratches could accumulate and ultimately blind him. Instead, doctors performed what was then a new operation: They sliced open his eyelids, rolled them back and sutured them with the lashes facing outward again. And they gave him antibiotics to clear up the infection. “My vision is much better now,” said Mr. Rana, a tiny, lively man who guessed he was about 65. “I can recognize people. I can work.” His personal triumph parallels his nation’s. In May, the World Health Organization declared that Nepal had eliminated trachoma as a public health problem, making it the sixth country to do so. In June, Ghana became the seventh. Quietly, in the shadow of fights against better-known diseases like Ebola, AIDS and malaria, the 20-year battle against trachoma is chalking up impressive victories. Those successes, experts say, show the wisdom of advocating and enforcing basic public health practices, rather than waiting for a miracle cure or a new vaccine. © 2018 The New York Times Company

Keyword: Vision
Link ID: 25222 - Posted: 07.18.2018