Even with glasses on, the ability to embed is probably good enough to recognize small letters on a page. The text on most computer screens is about 3 millimeters long and 2 mm wide (12 x .08 inches). As he reads this single sentence, he is probably unaware of the thousands of visual information collected by the eyes every second. In filming, millions of cells work as photoreceptors that react to light, just like a camera does to capture images.
The retina is a thin layer of nerve tissue that covers the back wall of the eye. Some of these cells move to receive light, while others interpret information and send messages to the brain via the optic nerve, and this is part of the process that enables vision. In damaged or dysfunctional retinas, photoreceptors stop working, causing blindness. By some estimates, there are more than 10 million people worldwide affected by retinal diseases that lead to vision loss. Until now, those who lost sight of retinal disease had little hope of reclaiming it. However, technological advances can restore most eyesight. Several groups of scientists have developed silicon microchips that can create artificial vision. This article contains information about how the retina works and why blindness from retinal disease no longer means vision loss.
How Does the Retina Work?
The eye is one of the most amazing organs in the body. To understand how artificial vision is created, it is important to know the important role the retina plays in how we see. A simple explanation for what happens when looking at an object is as follows:
• Light scattered from the object enters the cornea.
• Light is reflected on the retina.
• The retina sends messages to the brain via the optic nerve.
• The brain interprets what the object is.
The retina is complex in itself, and this thin membrane at the back of the eye is a vital part of vision. Its main function is to take images and transmit them to the brain, and these are the three main types of cells in the eye that help perform this function. These three main cells are as follows:
• Ganglion cells
There are about 125 million rods and cones in the retina that act as the eye’s photoreceptors. The rods are the most numerous of the two photoreceptors, with more cones than 18 to 1 in number. The sticks can operate in low light (detect a single photon) and create black and white images without much light. When there is enough light, cones give us the ability to see the color and details of objects. Cones are responsible for letting you read this article because they allow us to see in high resolution. Information received by the rods and cones is then transmitted to about 1 million ganglion cells in the retina. These ganglion cells interpret messages from rods and cones and send information to the brain via the optic nerve. There are a number of retinal diseases that attack these cells and can lead to blindness. The most important of these diseases are retinitis pigmentosa and age-related macular degeneration. Both of these diseases attack the retina, rendering rods and cones inoperable, causing either peripheral vision loss or complete blindness. However, none of these retinal diseases have been found to affect ganglion cells or the optic nerve. This means that if scientists can develop artificial cones and rods, information can be sent to the brain for interpretation.
Creating Artificial Vision
The current path scientists have followed to create artificial vision was established in 1988 by Dr. It was shaken when Mark Humayun showed that by stimulating the nerve ganglia behind the retina with an electric current, a blind person could see light. This test has proven that the nerves behind the retina still work even if the retina has degenerated. Based on this information, scientists began to create a device that could translate images and electrical pulses that could restore vision. Today, such a device is very close to reaching millions of people who have lost their sight against retinal disease. Artificial silicone retina was developed in FDA clinical trials as of 2007, [Optobionics (ASR), Groves, and achieved improvements in vision in 10 subjects over a two-year period.
The ASR is an extremely small device, smaller than the surface of a pencil eraser. It has a diameter of only 2 mm (.078 inches) and is thinner than a human hair. There is a good reason for its microscopic size. This is why an artificial retina must be small enough to function so that doctors can implant it into the eye without damaging other structures in the eye. The most important development in artificial retina research was the Ministry of Energy’s creation of the Artificial Retina Project, led by Mark Humayun. ARP is a group of public and private companies, universities and research laboratories that has put together efforts to perfect a nano-sized device. Since 2002, six blind volunteers have been attached to the device, which has been successful in helping them detect light, dark and large objects, and the ARP has two more devices in testing.
How Does Artificial Silicone Retina Work?
ASR can transform solar cells containing 3,500 microscopic pulses into light, mimicking the electric taper and rod-like function. To place this device in the eye, surgeons make three small incisions in the white part of the eye, no larger than the diameter of a needle. Through these incisions, he inserts a miniature cutting and vacuuming device that removes the gel in the middle of the eye and replaces it with salt water. Then, a point opening is opened in the retina where they inject fluid from the back of the eye to lift up part of the retina, creating a small pocket in the subretinal space for the device to fit. The retina is then resealed over the ASR. Any microchip needs power to work, and the amazing thing about ASR is that it gets all the power it needs from the light entering the eye. As previously learned, light entering the eye is directed to the retina. This means that when the ASR implant is placed behind the retina, it receives all the light that enters the eye. This solar power eliminates the need for any wires, batteries or other secondary devices to power it.
Another microchip device to restore partial vision is being developed by a research team from Johns Hopkins University, North Carolina State University and North Carolina-Chapel Hill University. This device, called the artificial retina component chip (ARCC), is very similar to ASR. Both are made of silicon and both are powered by solar energy. Also, the ARCC is a very small device measuring 2mm square with a thickness of 02mm (.00078 inches), and however, there are significant differences between devices. Unlike ASR, which is placed between layers of retinal tissue, ARCC is placed on top of the retina. Because it is so thin, light entering the eye is allowed to pass through the device to hit the photosensors on the back of the chip. However, this light is not the power source of the ARCC. Instead, a second device connected to a pair of glasses is a solar cell that powers the directional laser. The laser must be powered by a small battery pack.
According to the researchers, ARCC allows visually impaired patients to see 10 by 10 pixel images that are the size of a single letter on this page. However, the researchers said they could develop a chip version that would allow a 250 by 250 pixel array to allow those who were once blind to read a newspaper.