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Bionic Eyes Unveiled At Science Exhibition

Discussion in 'JF Doctor' started by X-PASTER, Jul 6, 2011.


    X-PASTER Moderator

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    Bionic Eyes Unveiled At Science Exhibition


    Bionic eyes and the latest invisibility experiments are among the exhibits at a science fair in London.

    Researchers say the bionic eyes, which are on show at the Royal Society Summer Science Exhibition , could be a low-cost way to help tens of thousands of people.

    The prosthetics are worn like glasses and contain a small camera connected to a tiny powerful computer.

    The software recognises objects of significance and uses LEDs within the glasses to light them up, allowing users to see nearby items more clearly.

    Scientists are carrying out a year-long study on the device which it is hoped could provide a non-surgical option those suffering from eye diseases.

    Dr Stephen Hicks, who worked on the research at the University of Oxford, says making the device appealing to wear is crucial.

    He said: "We're aiming to design a visual aid that is as discreet and economical as possible. No one really wants to wear a bulky camera or computer headset.

    "It's very satisfying to think that the relatively low cost of its components should make this device easily available to the people who need it most."

    Harry Potter fans will also be able to see how close they could be to getting their own invisibility cloak, just like the boy wizard.

    Professor Ulf Leonhardt from the University of St Andrews will show his attempts to develop a blueprint for a cloaking device.

    His theory suggests bending light around an object using artificial optical materials in order to provide the ultimate disguise. |

    KAKA A TAIFA JF-Expert Member

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    [h=1]Perceiving Light[/h]
    When light enters the eye, it first passes through the cornea, then the aqueous humor, lens and vitreous humor. Ultimately it reaches the retina, which is the light-sensing structure of the eye. The retina contains two types of cells, called rods and cones. Rods handle vision in low light, and cones handle color vision and detail. When light contacts these two types of cells, a series of complex chemical reactions occurs.

    The chemical that is formed (activated rhodopsin) creates electrical impulses in the optic nerve. Generally, the outer segment of rods are long and thin, whereas the outer segment of cones are more, well, cone shaped. Below is an example of a rod and a cone: [TABLE="align: center"]

    The outer segment of a rod or a cone contains the photosensitive chemicals. In rods, this chemical is called rhodopsin; in cones, these chemicals are called color pigments. The retina contains 100 million rods and 7 million cones. The retina is lined with black pigment called melanin -- just as the inside of a camera is black -- to lessen the amount of reflection. The retina has a central area, called the macula, that contains a high concentration of only cones. This area is responsible for sharp, detailed vision.

    When light enters the eye, it comes in contact with the photosensitive chemical rhodopsin (also called visual purple). Rhodopsin is a mixture of a protein called scotopsin and 11-cis-retinal -- the latter is derived from vitamin A (which is why a lack of vitamin A causes vision problems). Rhodopsin decomposes when it is exposed to light because light causes a physical change in the 11-cis-retinal portion of the rhodopsin, changing it to all-trans retinal. This first reaction takes only a few trillionths of a second. The 11-cis-retinal is an angulated molecule, while all-trans retinal is a straight molecule. This makes the chemical unstable. Rhodopsin breaks down into several intermediate compounds, but eventually (in less than a second) forms metarhodopsin II (activated rhodopsin). This chemical causes electrical impulses that are transmitted to the brain and interpreted as light. Here is a diagram of the chemical reaction we just discussed: [TABLE="align: center"]

    Activated rhodopsin causes electrical impulses in the following way:
    1. The cell membrane (outer layer) of a rod cell has an electric charge. When light activates rhodopsin, it causes a reduction in cyclic GMP, which causes this electric charge to increase. This produces an electric current along the cell. When more light is detected, more rhodopsin is activated and more electric current is produced.
    2. This electric impulse eventually reaches a ganglion cell, and then the optic nerve.
    3. The nerves reach the optic chasm, where the nerve fibers from the inside half of each retina cross to the other side of the brain, but the nerve fibers from the outside half of the retina stay on the same side of the brain.
    4. These fibers eventually reach the back of the brain (occipital lobe). This is where vision is interpreted and is called the primary visual cortex. Some of the visual fibers go to other parts of the brain to help to control eye movements, response of the pupils and iris, and behavior.
    HOW DOESINICEYE HELPSA BLIND EYE TO SEE: In the past 20 years, biotechnology has become the fastest-growing area of scientific research, with new devices going into clinical trials at a breakneck pace. A bionic arm allows amputees to control movements of the prosthesis with their thoughts. A training system called BrainPort is letting people with visual and balance disorders bypass their damaged sensory organs and instead send information to their brain through the tongue. Now, a company called Second Sight has received FDA approval to begin U.S. trials of a retinal implant system that gives blind people a limited degree of vision.

    The Argus II Retinal Prosthesis System can provide sight -- the detection of light -- to people who have gone blind from degenerative eye diseases like macular degeneration and retinitis pigmentosa. Ten percent of people over the age of 55 suffer from various stages of macular degeneration. Retinitis pigmentosa is an inherited disease that affects about 1.5 million people around the globe. Both diseases damage the eyes' photoreceptors, the cells at the back of the retina that perceive light patterns and pass them on to the brain in the form of nerve impulses, where the impulse patterns are then interpreted as images. The Argus II system takes the place of these photoreceptors.

    The second incarnation of Second Sight's retinal prosthesis consists of five main parts:
    • A digital camera that's built into a pair of glasses. It captures images in real time and sends images to a microchip.
    • A video-processing microchip that's built into a handheld unit. It processes images into electrical pulses representing patterns of light and dark and sends the pulses to a radio transmitter in the glasses.
    • A radio transmitter that wirelessly transmits pulses to a receiver implanted above the ear or under the eye
    • A radio receiver that sends pulses to the retinal implant by a hair-thin implanted wire
    • A retinal implant with an array of 60 electrodes on a chip measuring 1 mm by 1 mm The entire system runs on a battery pack that's housed with the video processing unit. When the camera captures an image -- of, say, a tree -- the image is in the form of light and dark pixels. It sends this image to the video processor, which converts the tree-shaped pattern of pixels into a series of electrical pulses that represent "light" and "dark." The processor sends these pulses to a radio transmitter on the glasses, which then transmits the pulses in radio form to a receiver implanted underneath the subject's skin. The receiver is directly connected via a wire to the electrode array implanted at the back of the eye, and it sends the pulses down the wire.
      Optobionics/Getty Images
      *A magnified image of an eye with age-related
      macular degeneration
      When the pulses reach the retinal implant, they excite the electrode array. The array acts as the artificial equivalent of the retina's photoreceptors. The electrodes are stimulated in accordance with the encoded pattern of light and dark that represents the tree, as the retina's photoreceptors would be if they were working (except that the pattern wouldn't be digitally encoded). The electrical signals generated by the stimulated electrodes then travel as neural signals to the visual center of the brain by way of the normal pathways used by healthy eyes -- the optic nerves. In macular degeneration and retinitis pigmentosa, the optical neural pathways aren't damaged. The brain, in turn, interprets these signals as a tree and tells the subject, "You're seeing a tree."
    • It takes some training for subjects to actually see a tree. At first, they see mostly light and dark spots. But after a while, they learn to interpret what the brain is showing them, and they eventually perceive that pattern of light and dark as a tree.
      The first version of the system had 16 electrodes on the implant and is still in clinical trials at the University of California in Los Angeles. Doctors implanted the retinal chip in six subjects, all of whom regained some degree of sight. They are now able to perceive shapes (such as the shaded outline of a tree) and detect movement to varying degrees.
    • The newest version of the system should offer greater image resolution because it has far more electrodes. If the upcoming clinical trials, in which doctors will implant the second-generation device into 75 subjects, are successful, the retinal prosthesis could be commercially available by 2010. The estimated cost is $30,000.
      Researchers are already planning a third version that has a thousand electrodes on the retinal implant, which they believe could allow for facial-recognition capabilities.