Shanxi boy Xiao Binbin was cruelly gouged out of both eyes, recently a hospital for its free surgery to implant prosthetic eyes. So, like the case of small Binbin, can further in the future through more advanced “electronic eye” surgery to help it “see” the world. Zheng Bin, deputy chief physician of Suzhou City Optometric Hospital, analyzed that the “electronic eye” is the “electronic visual prosthesis” that scientists are actively conducting research. At present the little Bin Bin may not be able to accept the “electronic eye” surgery.
According to reports, the formation of human vision requires a complete visual pathway, including the refractive system of the eye, the retina, the visual pathway and the visual center of the brain. When people look at external objects, the object image focused on the retina, stimulating the visual cells to produce electrical signals, and through the nerve fibers to the brain. Therefore, each visual cell is followed by a nerve fiber that travels to the corresponding point in the brain center. For example, the image of a cup, after stimulating a piece of visual cells, causes the nerve fibers connected to them to transmit electrical signals and excite the corresponding brain tissues, which, through a series of complex biochemical reactions, form the concept of the shape, color, etc. of the cup. Thus, the generation and transmission of electrical signals is the basis of vision formation. Theoretically, the image of a cup can be produced if these sites can be selectively stimulated in the retina, optic nerve and brain centers. In fact, retinal stimulation sites are the easiest to find, and there is no technology that can accurately locate the correspondence between optic nerve fibers or brain cortical cells and object images, so the idea of selective stimulation in the latter two to produce similar images is still difficult to achieve.
The visual prosthesis is an optoelectronic conversion device that works similarly to a cochlear implant, i.e., a camera replaces the microphone of the cochlear implant and is converted into an electrical signal when receiving external light stimulation. At the same time, it should have the ability of selective stimulation, that is, it can only excite the nerve corresponding to the image and transmit the electrical signal; if once the irrelevant nerve is stimulated, it may not be able to produce a similar image for the object.
Currently, depending on the implantation and stimulation site of the visual prosthesis, the visual prosthesis is divided into three major categories: optic cortex prosthesis, optic nerve prosthesis, and retinal prosthesis. Among them, retinal prosthesis is the most actively researched in recent years. The prosthesis is surgically implanted in front of the retina or under the retina, and the chip directly senses the object stimulation and generates electrical signals to directly stimulate the visual cells in the corresponding area, which enters the brain along the original normal visual pathway to produce vision. Therefore, the more dense the stimulation points are, the clearer the image will be. However, the results so far have only enabled blind people to see the blurred outlines of objects, which is still very far from the desired colorful and clear vision. Currently, its clinical application is limited to eyes blinded by lesions in the outer layer of the retina, such as retinitis pigmentosa. Therefore, for cases like Binbin’s, where the retina is missing, the main consideration is to be able to install a visual cortex prosthesis in the future, which mainly obtains images through a miniature camera mounted on glasses, and then converts them into wireless signals in an extracorporeal device that transmits them to electrodes and chips implanted in the head, stimulating the visual area of the brain to “see” objects. However, this procedure requires craniotomy, and there is a risk of bleeding and infection after surgery; at the same time, the voltage generated by the stimulation may cause pain or seizures in patients. The difficulty is that it is not possible to selectively stimulate points in the brain to produce similar images, which is an important concern at this time.
Another type of prosthesis is the optic nerve prosthesis, which stimulates the optic nerve stump to produce the effect of “optical illusion”. However, the implantation of this prosthesis still requires craniotomy, still cannot resolve the visual correspondence, and has limited spatial resolution, so there are still many problems to be solved. According to the current research progress, some scientists expect that there may be a breakthrough in the next 5-10 years. This is also the reason why Binbin cannot receive the “electronic eye” surgery.