One of the most well-known and well-developed projects comes from the Department of Ophthalmology and the Department of Biomedical Engineering at my alma mater, the University of Southern California. Led by Dr. Mark Humayun and Dr. James Weiland, with teams from USC, Caltech, UC Santa Cruz, and the National Science Foundation, with Second Sight Medical Products, Inc., the 10-year old project consists of a glasses-mounted camera, an implanted wireless receiver, and a small electrode array attached to the back of the retina. The camera captures an image and converts it into an electric signal, which is sent to the receiver implanted inside the eye. The receiver sends the signal to the electrode array, which emits electrical pulses perceived by the user as small points of light.
Current research includes developing an intraocular camera which would be placed into the space that the (now-useless) lens occupies. Users of the current glasses-mounted camera must move their heads to scan an object. An intraocular camera will allow users to move their eyes to scan an object in a more natural manner. Another ongoing project is increasing the number of electrodes on the array. The first model (Argus I) had 16 electrodes, allowing the user to basically see only a 4x4 field of pixels. The latest model has 60 electrodes, allowing the user to see much greater detail.
Other notable approaches include the Implantable Miniature Telescope (IMT), developed by Dr. Isaac Lipshitz with VisionCare. The IMT takes one's central field of vision and enlarges it up to 3x. In this way, the image is not focused on the damaged part of the retina but is projected over other healthy parts of the retina, which reduces the blind spot that those with AMD suffer from.
Another unique approach is the Artifical Silicon Retina, developed by Drs. Alan and Vincent Chow. The ASR is implanted in the sub-retinal space in the eye and the unique composition of the device converts light into electrical current without the need of any external devices, basically mimicking the function of photoreceptors. However, it is shown that the device is not theoretically practical for neural stimulation. Moreover, Optobionics, the company that developed the ASR, ceased operations in May 2007.
Visual prostheses are exciting devices with numerous engineering challenges to overcome. The physiology of the eye only allows for an implant no larger than 5mm. The curvature of the eye presents challenges in developing electrode arrays with equal retinal stimulation. And as with almost any implant, there are issues of power and telemetry requirements. However, there is so much devoted to researching visual prostheses that we will undoubtedly have some amazing "bionic eyes" in the near future.
Learn More:
No comments:
Post a Comment