If a digital camera is used for analogy, the cornea and lens of the human eye are equivalent to the lens, the retina behind the eyeball is a photosensitive device, the optic nerve is equivalent to the line connecting the photosensitive device and the memory card, and the visual cortex at the back of the brain is Memory card and post-processing software. Diseases such as retinitis pigmentosa or age-related macular degeneration can cause the retina to lose its function, making the camera unable to perceive any image; while Second Sight in the United States is trying to replace the lost retina with electronics. Help these patients regain basic vision.
This technique is artificial retinal technology. It is similar to the principle of a cochlear implant—using a nerve that is still stimuli, allowing the brain to receive signals and that the senses are still working. In the past 20 years, hundreds of thousands of people have acquired hearing through cochlear implants, but the progress of artificial retina has been somewhat stagnant.
This is because the vision system is much more complicated. About 80% of the information we get comes from vision. People have not been able to produce cameras with comparable performance to the human eye, and the exact correspondence between photoreceptor cells and optic nerves is still a mystery. Taking into account the technical limitations - artificial retina chips are generally only a few square millimeters in size, and the thickness is less than 100 microns - it is quite difficult to get accurate vision like the human eye.
Although as early as 1924, it was discovered that the use of electrical stimulation in the visual cortex produced illusory vision, but it was not until 1967 that artificial vision devices implanted in the visual cortex were developed. However, the visual quality produced by this method is very poor, and research in this field has begun to gradually shift from visual cortical implantation to retinal implantation. In the past 30 years, many research institutions and manufacturers have invested in this field, and research ideas have been divided into two categories: subretinal implantation and extraretinal implantation technology.
The subretinal implantation technique is to implant the chip into the region between the retinal nerve sensory epithelium and the pigment epithelium, instead of using the light-sensing cell to sense the illumination, directly using the coding and decoding mechanism of the retina itself to convert the electrical signal into vision. It still uses the patient's own "lens", just like changing a photosensor for a digital camera. This technology requires an external power supply unit, which is difficult to operate and has a small range of use, but does not require a camera to be attached. The main investigators of subretinal implantation techniques are the research team of Alan Chow of the University of Chicago and the Eberhart Zrenner team of the University of Tübingen, Germany. The University of Tübingen has developed a prototype of this device, which has 1500 electrodes, powered by a wireless power supply behind the ear, and the team has conducted ten implant tests.
The extraretinal implantation technique is to attach the electrode array to the outer surface of the retina, and directly stimulate the nerve cells with signals transmitted from the outside, which is equivalent to completely replacing the lens and the photosensitive device. The main researchers in this field are the University of Bonn, Germany, Hopkins University, MIT and Harvard University, and the Doheny Eye Institute at the University of Southern California. The second vision company's artificial retina technology was developed on the basis of the Dohany Institute.
In 1998, Dr. Robert Greenberg and Sam Williams founded the Second Vision Company. Sam himself, a patient with retinitis pigmentosa, lost confidence in public research in this area, so he decided to develop artificial retinal devices that could be put into commercial use. Sam died in 2009, and did not have time to wait until the day when his goal was achieved. But his legacy will benefit many people.
Argus is the name of the giant eye in Greek mythology. The artificial retina system under its name consists of a small camera, a microcomputer and some wireless communication tools. In 2002, at the inspiration of an invention by the University of Southern California's Dohany Eye Institute, Argus I was developed with 16 electrodes. Between 2002 and 2004, a total of 6 experimental implants were performed. These patients have a simple sense of light that can determine the movement of an object and distinguish objects from the background.
For this type of technology, the more electrodes you have, the more points you can see. The Argus II now has 60 electrodes. Since 2006, it has regained basic vision for 40 patients, some of whom have been able to distinguish between objects, shapes, and even prints in large prints. Although the user needs a certain degree of training to understand what the light point in the field of vision means, but it is better than groping in the dark world.
Argus II is not a cure for blindness, but a cure for some specific retinal diseases. According to statistics compiled by the World Health Organization, the global visually impaired population exceeds 45 million, and one person deteriorates on average every 5 seconds. It is estimated that by 2020, the visually impaired population will increase to 76 million; and as the population ages Development, the number of patients with age-related macular degeneration will also increase. What Argus II can do is to help these patients get a better quality of life.
The artificial retina will begin trials in hospitals in London, Manchester, Paris and Geneva, and will be sold in the United States once approved by the US Food and Drug Administration. Second Vision hopes to sell 100 implanted devices in the first year, each at a price of $100,000. “Although this price looks a bit high,†Dr. Greenberg said, “but this is actually about the same price as the first cochlear implant.†He hopes that Argus II will be included in the government's subsidy program, so that prices will become easier. accept.
Currently, the company has applied for 76 patents in the United States. Now that they have prepared the Argus III animal experiment, the new generation of artificial retina will have hundreds of electrodes.
Although Argus can only let people see some light spots, its future will not be limited. The technology that has just been introduced to the market will not be the final version, and these spots have already shown hope.
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