What Is a Visual Prosthesis?

Artificial vision refers to the method of using retinal repair technology to implant an integrated circuit chip into the eye to help the blind restore vision.

Chinese name: Artificial vision
Foreign name: artificial vision

Technology: Retinal repair
Features: Implanting an integrated circuit chip into the eye
Meaning: Helping blind people regain sight

Introduction to artificial vision

There are two commonly used methods of artificial vision: one is called "artificial retina technology"; the other is "electrically stimulated visual center technology". The former is based on the patient's visual conduction pathways and visual central non-dysfunction, while the latter has no special requirements for visual conduction pathways, so it has broader application prospects. It is currently estimated that 90% of blind patients belong to the latter case.

The study of artificial vision first began in the 1950s. In 1956, American scientist Tassiker discovered that a photosensitive selenium battery implanted under the retina can produce a light sensation. From the 1960s to the 1970s, scientists observed through a series of experiments that the visual system can be activated by external electrical stimuli. Studies on primary retinal pigment degeneration have found that even if the photoreceptor cells are damaged, functional nerve cells still exist in the inner retinal tissue to transmit and process information. By the 1980s and 1990s, scientists began to study artificial visual stimulators.

Artificial vision standard

The ideal visual prosthesis should have the following criteria:

The prosthesis should be movable;

Such prostheses should use existing visual pathway devices to provide artificial vision;

Can reproduce very close to normal vision.

How artificial vision works

A miniature camera mounted on the frame of a blind person captures external image information and transmits a signal along a wire to an integrated circuit chip mounted on the inner surface of the retina. The latter consists of a signal processor and nearly 100 made of platinum. It is composed of disc-shaped microelectrodes. After the signal is processed, it is transmitted to the nerve cells below the inner surface of the retina via microelectrodes, and the latter completes the remaining signal transmission until it reaches the visual center of the cerebral cortex to form vision.

Artificial vision difficulties

1. Whether the implanted chip can stay in the eyes for a long time is a question. Because the eye is a very delicate organ, the long-term retention of foreign implants can cause infections at any time, and the ultimate goal of the researchers is to permanently install such a chip in the eye. In addition, the long-term erosion of the chip by various electrolyte components in body fluids will also shorten the life of the chip.

2. The adaptability of the implanted chip is also a problem, especially when the eyeball rotates quickly, can the thin sheet made of silicon move freely with the inner surface of the retina without scratching the retina, which becomes a problem The key is.

3. The strength of the electric impulse at the contact point between the microelectrode and the inner surface of the retina. Nerve cells known to receive electrical impulses are located 50-100 microns below the inner surface of the retina. To cross this distance, the intensity of the electric impulses from the electrodes must be large enough to ensure that the underlying nerve cells can be effectively activated. But this electric impulse generates some heat. If the intensity is too high, it is likely to burn the retina.

4. Design dimensions of microelectrodes. The researchers' goal is to make the images seen by the blind as clear as possible. This requires each microelectrode to be as small as possible, and the stimulus range of its electrical impulses is concentrated as much as possible, so that the number of nerve cells stimulated in a unit area is as large as possible, and the transmitted information will be more abundant . The problem is that too concentrated electrical impulses can also generate high temperatures.

5. The cerebral cortex will receive signals from the implanted chip and restore them to image information to generate vision.

Artificial vision progress

In 2008, Japan developed an artificial vision device that can transmit visual signals to the brains of blind and visually impaired people.

A pair of sunglasses used in this device is equipped with a scanning camera and an electronic device, which can convert the image of the object in front of the eye into digital signals. The electrodes implanted into the vitreous body of the eye through minimally invasive surgery can stimulate the visual nerves based on these digital signals. When the resulting optic nerve signal reaches the brain, the patient can "see" the image again.

The clarity of the image perceived by the patient depends on the number of implanted electrodes, which acts as a pixel of a digital camera. The more the number of electrodes, the clearer the perceived image.

At present, this artificial vision device has 9 implanted electrodes. Japanese experts plan to use a new generation of 49-electrode device in 2008 to make the images perceived by patients clearer.

This device is only suitable for those who have lost the ability to transmit retinal light signals, such as those with pigmented retinitis, autoimmune retinopathy or age-related eye diseases. Japanese experts hope to bring the device to market in 2012.