New retinal prosthesis works like a solar cell
According to the report of the Physicist Organization Network on May 13, Stanford University School of Medicine developed a retinal prosthesis similar to a solar cell system that can be surgically implanted below the retina to help patients recover from blindness due to degenerative eye disease. vision. The related papers were published in the "Natural and Photonics" magazine published today.
In patients with retinal degenerative diseases such as age-related macular degeneration and retinitis pigmentosa, the retinal photoreceptor cells slowly degenerate, eventually leading to blindness, but the internal optic nerve is not damaged, and signals from photoreceptors can be transmitted to the brain. Retina prostheses can help patients see the light again.
The researchers said that their new retina prosthesis device has a pair of specially designed eyepieces, equipped with a miniature camera and a microcomputer for processing visual data streams. The resulting image is displayed on a miniature liquid crystal display embedded in the eyepiece. The monitor emits Near-infrared laser pulses project the playback image onto an optoelectronic silicon chip that is implanted under the retina and is only as thin as 1/3 of a hair. The photodiode on the chip generates an electrical current that causes the retinal signal to be transmitted to the brain, thereby allowing the patient to gain vision.
"It works like a solar cell, converting light into electricity. The difference is that the current is induced in the retina," said Daniel Paranke, one of the senior authors of the paper and associate professor of ophthalmology. The retina is like a film or a digital chip. Photoreceptor cells are one pixel. They used photodiodes instead of photoreceptor cells. Each pixel resembles a small solar cell. When exposed to light, it generates an electric current that excites the optic nerve cells in the inner layer of the retina. This creates a cascade effect that activates the outer ganglion cells of the retina and sends visual information to the brain for the patient to see.
Other types of retinal prosthesis are currently in clinical trials, but the transplant procedure for these devices is very cumbersome. A coil, cable, or antenna is implanted in the eye to provide power and information to the implanted retina. The latest equipment uses near-infrared light to transmit images, does not require any wire and cable, and is very thin and easy to implant. "Surgery just implants a small bag under the retina and puts a photovoltaic cell in it," said Palank, and the photovoltaic cell can also be arranged in large numbers in the eye to provide a broader view.
In the experiment, the team produced a pencil-tip chip containing hundreds of photodiodes and used the retinas of normal and blind mice as degenerating retina models. They placed the chip under the retina and placed a multi-electrode array on the ganglion cell layer to detect current activity. After the light pulse is emitted, both the visible light and the near-infrared light generate a current in the photodiode.
The ganglion of normal mice responded to visible light as expected, and produced a similar response to near-infrared light. In the retina of a blind mouse, normal light causes only a weak response, and near-infrared light triggers a strong reaction that almost reaches the level of the normal mouse retina.
Preliminary experimental data show that the visual signal is reaching the brain, and the current experiment is still in progress. Stanford University has applied for a patent on two technologies in this system. (Chang Lijun)
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