The prosthetic device Argus II is a new prototype of artificial retinal system that is developing and testing to restore vision in patients with congenital or acquired blindness due to degeneration photoreceptors in the retina.
The apparatus consists of an implant that is implanted through microsurgery on the innermost layer of the retina in which are contained the ganglion cells. The prototype does not present light-sensitive areas, uses of glasses and an antenna, receives the image of the external environment, translating it into electrical signals, through a camera unit and a data processing –VPU – positioned externally to the body. Then, the small electrodes placed on the device directly stimulates the inner ganglion cell axons that make up the optic nerve. At this point the information translated, and proceeds to the visual cortex through the normal routes of nerve transmission. It is therefore necessary that the neural structures downstream of the retina are intact and functional in the patient so that this type of implant to be effective. Dr. Mark S. Humayun, who had already participated in the development of prostheses MARC, has used the experience gained to continue to expand the project to develop an artificial visual prosthesis that can restore partial sight. The new research group, called “Intraocular Retinal Prosthesis Group”, based at the Doheny Retina Institute at the University of Southern California, is a collaboration between Dr. Humayun and the Dr. Eugene de Juan . The team supervised the planning of a cutting-edge device to restore vision and has relied on private company Second Sight for much of the subsidy and the construction material of the device.
The Argus II bionic eye, converts the sequence of video frames captured by a room miniaturized, housed in the goggles of the patients, into a series of electrical impulses that are sent wirelessly to the electrodes implanted on the surface of the retina. These pulses are spurred remaining healthy cells of the retina causing the perception of forms of light in the brain. The patient then learn to interpret these signals. Argus II uses therefore two basic components, a one extraocular and intraocular. The electronic extraocular houses, is surgically attached to the temporal skull where a small cable subcutaneous, place more or less behind the ear, connects all’electrode array, intraocular. The Argus II implantation procedure involves placing surgically under general anesthesia of the internal components of the prosthesis.
The electronic case is grafted temporal area of the skull where the connecting cable that functions as an antenna is passed through a groove in the skull, within the space periocular then, via an incision of the sclera it reaches the inside of the eye .
The electrode array is placed on the retina, near the ganglion cells. After the operation is tested electrode conductivity, to make sure that all wires and connections are intact. The first tests, carried out at the operation, were to look at the screen of a computer and identify elements blacks and whites, with different orientations. The patient’s ability to correctly identify the direction of the lines and the difference between horizontal and diagonal lines, quickly demonstrates that the Argus II prosthesis epiretinale allows a restoration of function of central vision by non-existent in the first patient. Moreover doctors are convinced that, with practice and rehabilitation, vision continues to improve. Recently, last June, the Argus II bionic eye has been grafted onto a patient 80 year old English, Ray Flynn, who had long since lost his sight due to a dry macular degeneration related to age and allowed the man to again see silhouettes of people and objects. The project – which lasted 4 hours – by Dr. Paulo Stanga, consultant ophthalmologist and surgeon vetroretinico, was performed at the Manchester Royal Eye Hospital and the first tests were judged a success. As stated by Dr. Stanga:
Advances of Mr. Flynn have remarkable really you can see the silhouettes of people and objects. Ray Flynn is the first patient with this disease that has been grafted Argus II and is part of a test that we are conducting to determine whether blind patients with a total loss of central vision due to dry age-related macular degeneration may benefit by an artificial retina.