01-09-2016, 12:32 PM
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visual prosthesis, often referred to as a bionic eye, is an experimental visual device intended to restore functional vision in those suffering from partial or total blindness.A bionic eye mimics the function of the retina to restore sight for those with severe vision loss. It uses a retinal implant connected to a video camera to convert images into electrical impulses that activate remaining retinal cells which then carry the signal back to the brain. An external camera is worn on a pair of dark glasses which sends the images in digital form to the radio receiver placed in the eye. The radio receiver is attached to the implant chip on the retina. The implantation is of two types, epiretinal implant and subretinal implant, based on whether the implant is placed on or behind the retina.
Who is working on the bionic eye project?
Bionic Vision Australia (BVA) is a consortium of world leading Australian researchers, collaborating to
develop an advanced bionic eye. It brings together people from the Bionics Institute (BI), The University of Melbourne, The University of New South
Wales, the Centre for Eye Research Australia (CERA) and the National Information Communications Technology Australia (NICTA). The Royal Victorian
Eye and Ear Hospital is the clinical partner of the BVA collaboration and is the planned site for the first retinal implant.
Biological considerations
The ability to give sight to a blind person via a bionic eye depends on the circumstances surrounding the loss of sight. For retinal prostheses, which are the most prevalent visual prosthetic under development (due to ease of access to the retina among other considerations), patients with vision loss due to degeneration of photoreceptors (retinitis pigmentosa, choroideremia, geographic atrophy macular degeneration) are the best candidate for treatment. Candidates for visual prosthetic implants find the procedure most successful if the optic nerve was developed prior to the onset of blindness. Persons born with blindness may lack a fully developed optical nerve, which typically develops prior to birth, though neuroplasticity makes it possible for the nerve, and sight, to develop after implantation.
How does it work?
Components:
A digital camera that's built into a pair of glasses. It captures images in real time and sends images to a microchip.
A video-processing microchip that's built into a handheld unit. It processes images into electrical pulses representing patterns of light and dark and sends the pulses to a radio transmitter in the glasses.
A radio transmitter that wirelessly transmits pulses to a receiver implanted above the ear or under the eye
A radio receiver that sends pulses to the retinal implant by a hair-thin implanted wire
A retinal implant with an array of 60 electrodes on a chip measuring 1 mm by 1 mm.
The entire system runs on a battery pack that's housed with the video processing unit. When the camera captures an image -- of, say, a tree -- the image is in the form of light and dark pixels. It sends this image to the video processor, which converts the tree-shaped pattern of pixels into a series of electrical pulses that represent "light" and "dark." The processor sends these pulses to a radio transmitter on the glasses, which then transmits the pulses in radio form to a receiver implanted underneath the subject's skin. The receiver is directly connected via a wire to the electrode array implanted at the back of the eye, and it sends the pulses down the wire.
When the pulses reach the retinal implant, they excite the electrode array. The array acts as the artificial equivalent of the retina's photoreceptors. The electrodes are stimulated in accordance with the encoded pattern of light and dark that represents the tree, as the retina's photoreceptors would be if they were working (except that the pattern wouldn't be digitally encoded). The electrical signals generated by the stimulated electrodes then travel as neural signals to the visual center of the brain by way of the normal pathways used by healthy eyes -- the optic nerves. In macular degeneration and retinitis pigmentosa, the optical neural pathways aren't damaged. The brain, in turn, interprets these signals as a tree and tells the subject, "You're seeing a tree."