Keys to Visual Prostheses
Before moving on to more information, here are three important points to remember.
Point 1: An Electric Device
This visual prosthesis artificially creates vision. So, how is our innate vision created? It is created by fine and delicate but rational human body mechanisms.
Lots of factors are involved in this, and one of the most important elements is the electricity within human body. The fact is vision is also an electrical phenomenon.
In developing this visual prosthesis, we focused on this electricity. In case that problems arise in the generation and transmission of the electrical signals in the body due to an illness, this visual prosthesis aims to support the body to make use of the electrical signals when vision is not working properly. The system electrically stimulates body tissue and provides aid so that the transmission of electrical signals is resumed. The cell that creates electrical signals related to vision is called a photoreceptor. It is located in the retina deep in the eye. Nerve cells transmit visual information from the retina to the brain, mainly via electrical signals.
How we see
Point 2: An Implant‒type Medical Device
The visual prosthesis is a system device comprising several devices, each with a specific function. Some devices are implanted into the eye or body by surgery. When in use, implanted devices and devices externally worn operate together as a system.
Medical devices that are put into human body for extended periods are called implants. In recent years, electric devices that operate in the body are being clinically used in diverse fields, and the research and development of novel implant technology such as this visual prosthesis is actively conducted.
Examples of implant devices in clinical use
Implant devices must function without fail in the unique environment of the human body, and must be safe and reliable. Implant device development requires a large number of basic research studies for safe interface with organs or tissue in which it is implanted. For example, material used for implants must be tested under diverse conditions to investigate the state and possibility of change in features during and after manufacturing. In some cases, new material development may be necessary.
Point 3: Artificial Vision by the Visual Prosthesis are Created by Points of Light.
Vision that is achieved with the visual prosthesis is quite different from innate vision. Images artificially created will be crude and roughly contoured like a simple electrical billboard that is displayed with limited number of points of light.
Sample image of the letter N with the visual prosthesis
You may ask, "How good will this roughly contoured image be for the user?" However, even this rough image is predicted to enable individuals "to read large print" or "to find an obstacle," based on various tests and simulative studies. Even though the visual image is not equivalent to innate vision, the system enables patients to expand their range of activity, and increase independence. For this reason, the development of the system as a new medical device is supported and expected throughout the world.