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Researchers Pinpoint Where Brain Unites Eyes' Double Vision PDF
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Ophthalmology and Optometry
Thursday, 30 July 2015

Bas RokersUsing prisms and an advanced brain scanner, Bas Rokers, psychology professor at the University of Wisconsin-Madison, and collaborators at Utrecht University in the Netherlands have found the point in the human brain - very early in image processing in the visual cortex - in which the transformation to a cyclopean view of the world takes place.

According to Rokers, a group of neurons in the visual cortex called the striate cortex, or V1, is handling two sets of pictures from our eyes - one view each from the left eye and the right eye. Move one step down the line to an area called V2, part of the extrastriate cortex, and the neurons have largely shifted to a single picture. The research clears up unsettled questions as to what purpose V2 serves in visual processing.

The researchers tucked people in functional MRI machines, and had them peer into a prismatic device that showed each eye a different image. For example, the left eye would see a vertical black bar slightly to the right of center, while the right eye saw the bar slightly to the left of center. Because the MRI results are sharp enough to discern the different brain activity signatures for each vertical bar, the researchers could compare brain activity when the bars were presented to each eye separately or both eyes together.

The researchers plan to shift their attention to finer layers of V1, as well as to an area called V3, with an eye toward figuring out where the brain brings depth and object shape into focus. Rokers expects that a better understanding of the way images are processed will help with ongoing research into disorders like lazy eye. In amblyopia, the most common cause of vision problems among children around the world, the brain learns to favor the images of a stronger eye over those from one that is weaker or misaligned.

Their work has been published recently in the journal Current Biology.

 
New Study To Investigate Fluid Shift Effects On Visual Capacity In Astronauts PDF
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Ophthalmology and Optometry
Tuesday, 28 July 2015

intracranial pressure testNASA and the Russian Space Agency (Roscosmos) are studying the effects of how fluids shift to the upper body in space and how this adaptation to space flight affects changes in vision. This research will help prepare for a human journey to Mars. The Fluid Shifts investigation is part of the groundbreaking research taking place during the One-Year Mission, in partnership between NASA's Human Research Program and Roscosmos to tackle the complex, unanswered questions of how space flight changes the human body.

"The Fluid Shifts investigation is very complex because it's really a combination of three independent research studies with similar goals but different specific aims," said Michael Stenger, Ph.D. co-principal investigator for NASA's Fluid Shifts investigation. "We brought together investigators from NASA, Henry Ford Medical Center, University of California, San Diego and Wyle Science, Technology and Engineering Group. Additionally, we are working jointly with Roscosmos on the International Space Station to conduct the investigation and are using more crewmembers and crew time on this investigation than ever before."

The investigation tests the hypothesis that the normal shift of fluids to the upper body in weightlessness contributes to increased intracranial pressure and decreased visual capacity in astronauts. It also tests whether this can be counteracted by returning the fluids to the lower body using a "lower body negative pressure" suit, called Chibis, provided by the Russians.

While it sounds simple in theory, everyone responds differently to the upward fluid shift experienced in space flight, and this may explain the varying severity of the visual deficits experienced by astronauts. The physiological part of the investigation is only one challenge to the study.

This is not only the largest investigation on the space station, but one of the most challenging to set up. For the first time, substantial medical equipment is being moved from the U.S. segment to the Russian segment on the space station to perform this investigation.

The main complication is that the Chibis suit is located in the Zvezda service module on the Russian side of the space station and cannot be moved because its medical monitoring equipment and real-time data downlink are in fixed racks. This means all the necessary hardware and equipment from the U.S. side of space station are being relocated from the opposite end of the station to the Russian module.

"From an engineering perspective, the set up for this investigation is no easy task but something we are working through," said Erik Hougland, NASA flight project manager. "The physical and power interfaces are completely different too so we are redesigning these to work and fit the Russian outlets."

This type of experiment may have its share of challenges but according to Stenger the information learned from this study will make it well worthwhile for not only the crew but for patients on Earth as well.

Rather than conducting invasive procedures to measure intracranial pressure such as a lumbar puncture or intraventricular catheter (drilling into the skull), the crew is using and testing new noninvasive techniques and technologies in space. For example, the cerebral and cochlear fluid pressure (CCFP) device and distortion product otoacoustic emissions (DPOAE) are being used in place of the invasive methods to measure changes in intracranial pressure. These devices work by assessing characteristics of sound and pressure waves reflecting off the inner ear, which are reflective of changes in intracranial pressure. In the future, these devices may become available for patients on Earth suffering from elevated intracranial pressure, such as hydrocephalus patients. Additionally, NASA converted the Optical Coherent Tomography (OCT) imaging machine, commonly used in optometrist offices, into a portable camera so it can maneuver in a free floating area.

"We've never actually measured intracranial pressure inflight and its possible role in the Visual Impairment Syndrome," said Stenger. "If we want to stay in space longer than six months to explore, we have to determine what causes these vision changes so that we can begin developing countermeasures to prevent them."

While there is a need for these noninvasive technologies on Earth, NASA's main focus is on the crews in space as it prepares for missions to Mars, which could be a 30-month trip. Several months without gravity is a challenge to the human body, which is why the Fluid Shifts study is so important. More than two-thirds of NASA crewmembers have experienced ocular changes during space flight. This is currently one of NASA's highest priority medical concerns.

The One-Year Mission is the first step in determining the mechanisms associated with visual changes in space flight. NASA's Human Research Program is carefully evaluating how the bodies of Scott Kelly and Mikhail Kornienko respond to a year in space because the opportunity to have humans explore Mars could lead to insights, discoveries and technologies that will further humanity.

 
New Eye Drops Could Dissolve Cataract Without Surgery PDF
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Ophthalmology and Optometry
Friday, 24 July 2015

eye dropsCataracts are the most common cause of blindness worldwide, affecting tens of millions of people, and currently the only treatment is surgical removal of cataractous lenses. The precise mechanisms by which lens proteins both prevent aggregation and maintain lens transparency are largely unknown.

Researchers of The University of California, San Diego have found that eye drops treatment by lanosterol might reduce cataracts. Lanosterol is an amphipathic molecule enriched in the lens. It is synthesized by lanosterol synthase (LSS) in a key cyclization reaction of a cholesterol synthesis pathway. The scientists identified two distinct homozygous LSS missense mutations in two families with extensive congenital cataracts. Both of these mutations affect highly conserved amino acid residues and impair key catalytic functions of LSS. Engineered expression of wild-type, but not mutant, LSS prevents intracellular protein aggregation of various cataract-causing mutant crystallins. Treatment by lanosterol, but not cholesterol, significantly decreased preformed protein aggregates both in vitro and in cell-transfection experiments. The researchers further showed that lanosterol treatment could reduce cataract severity and increase transparency in dissected rabbit cataractous lenses in vitro and cataract severity in vivo in dogs. The study identified lanosterol as a key molecule in the prevention of lens protein aggregation and points to a novel strategy for cataract prevention and treatment.

The study has been published in Nature.

 
Researchers Use Metamaterials To Produce The 'Perfect Lens' PDF
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Ophthalmology and Optometry
Thursday, 23 July 2015

perfect lensResearchers at Michigan Technological University have found a way to possibly solve one of the biggest optical challenges, getting light waves to pass through the lens without getting consumed. The journal Physical Review Letters published their study this July, a continuation of work done by Durdu Güney, a professor of electrical and computer engineering at Michigan Tech.

Metamaterials are often based on natural materials but can be altered to have completely different optical properties. Metamaterials go beyond the limits of natural materials such as glass, plastic, metal or wood. To do that, the bases used for making a metamaterial—like the thin silver films Güney's group uses—are tweaked at the subwavelength scale so that light waves interact with the material in new ways. While no one has created a perfect lens yet, the metal base Güney tests would look more like a traditional glass lens; light would pass through instead of reflecting off the metal.

“Aluminum and silver are the best choices so far in the visible light spectrum, not just for a perfect lens but all metamaterials,” Güney says, explaining that metamaterials have been successfully created with these metals, although they still tend to absorb light waves. “Loss—or the undesired absorption of light—is good in solar cells, but bad in a lens because it deteriorates the waves,” he explains.

The solution to absorption is all in the light waves themselves, which behave strangely in metamaterials. To create their sci-fi light-bending properties, a perfect lens relies on negative index metamaterials. Positive and negative refer to how a material responds to propagating and decaying light waves, which are like the yin and yang of optics. Most materials—positive index materials—allow only propagating light waves to pass through. Negative index metamaterials, on the other hand, don’t just pass through propagating light waves but also amplify the decaying light waves.

“In order for the perfect lens to work, you have to satisfy a lot of electromagnetic constraints,” Güney explains. “We don’t know how exactly the required optical modes [light waves in the material] need to be excited and protected in the lens for the perfect construction of an image.”

This difficulty has led researchers to try numerous modifications of the metamaterial make-up, adding bulk, mode-by-mode nit-picking and increasingly complex models. But Güney and his team propose moving away from the complications and going back to the light itself. In their plasmon-injection scheme (shorted to pi-scheme or π-scheme), the researchers take advantage of knowing which light wave crumbles as it passes through the negative index lens. They use this wave—destined to fail in the lens—to shield the desired light wave, allowing it to pass through unscathed.

“With this approach, you can engineer this sacrificial wave,” Güney says. “It is difficult to construct this wave in other approaches.”

Moving the technology forward could mean more accessible medical technology and lightweight field equipment, just for starters.

“Imaging is one of the key technologies for this work,” Güney says, adding that a perfect lens could make science and medicine real for people. “It will make life easier to understand because people will be able to see it with their own eyes.”

 
Human Color Vision Gives People the Ability to See Nanoscale Differences PDF
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Ophthalmology and Optometry
Monday, 13 July 2015

Human EyeThe human eye is an amazing instrument and can accurately distinguish between the tiniest, most subtle differences in color. Where human vision excels in one area, it seems to fall short in others, such as perceiving minuscule details because of the natural limitations of human optics.

In a paper published recently in The Optical Society’s new, high-impact journal Optica, a research team from the University of Stuttgart, Germany and the University of Eastern Finland, Joensuu, Finland, has harnessed the human eye’s color-sensing strengths to give the eye the ability to distinguish between objects that differ in thickness by no more than a few nanometers — about the thickness of a cell membrane or an individual virus.

This ability to go beyond the diffraction limit of the human eye was demonstrated by teaching a small group of volunteers to identify the remarkably subtle color differences in light that has passed through thin films of titanium dioxide under highly controlled and precise lighting conditions. The result was a remarkably consistent series of tests that revealed a hitherto untapped potential, one that rivals sophisticated optics tools that can measure such minute thicknesses, such as ellipsometry.

“We were able to demonstrate that the unaided human eye is able to determine the thickness of a thin film — materials only a few nanometers thick — by simply observing the color it presents under specific lighting conditions,” said Sandy Peterhänsel, University of Stuttgart, Germany and principal author on the paper. The actual testing was conducted at the University of Eastern Finland. 

 
Researchers Manage to Detect Eye Diseases using Smartphone PDF
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Ophthalmology and Optometry
Thursday, 09 July 2015

Researchers at the Medical and Surgical Center for Retina developed software that detects eye diseases such as diabetic macular edema using a smartphone. The system is aimed at general physicians who could detect the condition and refer the patient to a specialist.

The software was developed in collaboration with biomedical engineers and uses the camera of the phone to detect any abnormality in the thickness of the retina. "The idea is to detect and prevent diseases in general practice. We are not replacing the specialist, we want to know which patients have a disease and make an early detection," says Dr. Juan Carlos Altamirano Vallejo, medical director of the Medical and Surgical Center for Retina.

He adds that the technology is designed for general physicians, "who support the health system in Mexico and, even without in-depth knowledge of ophthalmology, can, with this tool, detect certain abnormalities and send the patient to the specialist."

Using the software will reduce costs and streamline the Mexican health system. With just having the app on the cell phone and focusing the camera on the eye, immediate results will be obtained. "We start off the fact that it is much cheaper to prevent than to cure blindness."

The app also has utility in rural communities, where expertise areas such as ophthalmology have not arrive yet because equipment to detect these diseases are expensive and so far only the visiting specialist can do this kind of diagnosis.

"It will help those that when they go to the eye doctor are already blind, we needed to go a step back, to know who is at risk and needs to go to a specialist. Not wait for a doctor," says Altamirano Vallejo.

 
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