Artificial retina now in use

Discussion in 'General Science & Technology' started by cosmictraveler, Oct 10, 2011.

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  1. cosmictraveler Be kind to yourself always. Valued Senior Member

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    Scientists have been trying to build visual prostheses since the 1970s. This past spring the effort reached a crucial milestone, when European regulators approved the first commercially available bionic eye. The Argus II, a device made by Second Sight, a company in California, includes a video camera housed in a special pair of glasses. It wirelessly transmits signals from the camera to a 6 pixel by 10 pixel grid of electrodes attached to the back of a subject’s eye. The electrodes stimulate the neurons in the retina, which send secondary signals down the optic nerve to the brain.

    A 60-pixel picture is a far cry from HDTV, but any measure of restored vision can make a huge difference. In clinical human trials, patients wearing the Argus II implant were able to make out doorways, distinguish eight different colors, or read short sentences written in large letters. And if the recent history of technology is any guide, the current $100,000 price tag for the device should fall quickly even as its resolution rises. Already researchers are testing artificial retinas that do not require an external camera; instead, the photons will strike light-sensitive arrays inside the eye itself. The Illinois-based company Optobionics has built experimental designs containing 5,000 light sensors.

    http://discovermagazine.com/2011/sep/17-brain-see-said-blind-man-artifical-retina
     
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  3. Pincho Paxton Banned Banned

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    Wait till Sony get making them. Black bars at the top, and bottom, and 3 aspect ratios. Subtitles for the hard of hearing, and when you wake up in the morning.... da,da,da,da...da.da..

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  5. chimpkin C'mon, get happy! Registered Senior Member

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    Oh dear...a discount if you let them play adverts in your eyes...

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  7. billvon Valued Senior Member

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    One of the next problems researchers will have to deal with is replicating all the processing currently done in the eye. We tend to think of eyes as "cameras" that accurately relate an X by Y pixel map to the brain, but in fact they do far more than that. Edge detection, motion detection, basic shape detection etc is done in the our eye, and thus even someone who can get a high resolution picture sent to their brain will have serious deficits over a normally-sighted person (but, of course, will still be a dramatic improvement over being blind.0
     
  8. Pincho Paxton Banned Banned

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    Are you sure that's done in the eye, not the brain?
     
  9. chimpkin C'mon, get happy! Registered Senior Member

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    I'm pretty sure that's all done in the brain. Also turning the image right side up and forwards, since the image sent is backwards and upside-down, if I remember correctly...also has a hole in the center where the optic nerve inserts, and our brain typically fills this in for us.
     
  10. billvon Valued Senior Member

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    It can't be. We have 100 times more photoreceptor cells than we have nerves to carry the information to the brain. So compression has to occur. Edge detection is the most dominant form of compression, along with motion detection, color compression etc. What actually ends up hitting our brains looks nothing like a "picture" - it's already been predigested.

    Well, no need to really reverse anything. We perceive that upside down visual signal as normal.
     
  11. Trippy ALEA IACTA EST Staff Member

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    There is a degree of processing that takes place in the Retina - horizontal connections exist between photorecptors, enables (for example) edge detection, it's kind of an XOr process involving the bipolar cells. There is still significant processing in the brain, however, relating to edge detection - I think it basically boils down to a bunch of retinal ganglia say "I can see an edge!" (while others say "I can see a change in depth" or "I can see a change in contrast") and based on which ones are saying what the brain draws a picture of a horizontal line.
    Receptive Fields on Wiki
    Visual System on Wiki
    Visual Perception on Wiki
     
  12. billvon Valued Senior Member

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    Definitely. It's all one integrated system with lots of processing on both sides - which is why I think it will be hard to replace the eye with a camera.
     
  13. cosmictraveler Be kind to yourself always. Valued Senior Member

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    However seeing something is better than not seeing at all I would think. They will make progress with this idea and those who use them will be having better vision than in todays first step model.

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  14. Cifo Day destroys the night, Registered Senior Member

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    Much of the "compression" in the eye produces a lack of acuity in the periphery, and the eye compresses some color data, but the brain performs the rest of these functions.
     
  15. billvon Valued Senior Member

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    Definitely! And your brain is remarkably adaptable; no doubt people will be able to partially adapt to the lack of retinal processing and still be able to detect some motion and edges.
     
  16. Fraggle Rocker Staff Member

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    People have been fitted with lenses that invert the image received by the eye. After a few days their brains start working on the problem and within two weeks the image they "see" is right-side up.
     
  17. herbbread Registered Member

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    I actually don't think the retina would be that hard to replace with a video camera. While some processing does occur there, it's much much less than what we see at cortical stages. There is lateral inhibition which makes things a little bit more complicated, but we can crudely mimic this using various weightings of pixels. It will be slightly different than a camera since, as was pointed out, the photoreceptor density in the center "fovea" is much higher than at the periphery, but this is just a question of engineering your camera sensor to have a similar spatial arrangement.
     
  18. billvon Valued Senior Member

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    The retina does a 100:1 compression to fit the image down the limited number of nerves between the eye and the brain. That means that 99% of the data is "thrown away" so to speak. Fortunately our retina does this in a very clever way, in a way that is actually somewhat similar to the cosine compression that the .JPG format uses i.e. it encodes patterns and edges rather than the straight image. The bad news is that if you take a .JPG and try to look at it as a bitmap (i.e. without decoding it) it looks nothing like the original image.

    The good news is, of course, that both computers and our brains can take the compressed image and re-expand it to recover most of the original image. It's called "lossy compression" since you don't get all the detail back but it's pretty good overall.

    Yeah, a good understanding of how the retina compresses images will let us do the same in the camera's software before it's sent to the brain.
     
  19. Trippy ALEA IACTA EST Staff Member

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    No quite, it's not so much as compression as it is pre-processing - rather than seeing a thick black line as a thick black line, we see an edge that's white on one side, and black on the other, and another edge that's black on one side, and white on the other, and we see that there is black between them (more accurately, we see that there are no changes between them).
     
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