In our day to day life we see many blind people, although reason behind their blindness may be different. But now the technology is available which become the boon for the blind people & is Bionic Eye. Particularly for the people who got the retinal disorders like retinitis pigmentosa & macular degeneration etc. The bionic eye or the artificial retina is designed to interface & function with retina that has partial outer retina degeneration. Rods & cones, millions of them are is the back of every healthy human eye. They are biological solar cell in the retina. That solar cells convert light in to electrical impulses, impulses that travel along the optic nerve to brain where images are formed with out them we are blind.
The device commented here has basically two main types. The first one is silicon base chip & second one is ceramic photo sensors. Optobionics designed artificial silicon midrochip & SVEC (Space Vacuum Epitaxy Centre) in the Housten are experimenting with thin photosensitive ceramic films that respond to light much as rods & coins do. The silicon microchip mentioned above when surgically implanted under the retina in a location known as ‘Sub retinal space’. The ASR (Artificial Silicon Retina) chip is designed to produced visual signals similar to this produced by photoreceptor layer. This artificial photoelectric signal from the ASR microchip are in a position to induce biological visual signals in the remaining functional retinal cells. Which may be processed & send via optic nerve to the brain. The technology mentioned in a paper is so simple & precious too. It belongs to the research in Biomedical Instrumentation field going on every day in our world of innovations.
INTRODUCTION :--
The biomedical instrumentation is the field in which various solutions for the medical problems is served. Which is vast too ; also precious in some areas .
Here we are introducing the technological trend in biomedical system i.e. the BIONIC EYE ;the bionic eye is the artificial retinal part or retina which replaces the damaged one retinal cells in our eye .its implantation may be quite complex but it is working . First device which is introduced is of silicon which works properly but it reacts unfavorably with our eye fluids ;and next one is of ceramic films in this that problem is not present .this technique will offer various opportunities in the near future for the researchers in the various field ‘who are searching for solutions to the various retinal disorders in our eye.
THE HUMAN EYE
The area of the retina that receives and processes the detailed images and then sends them via the optic nerve to the brain is referred to as the macula. The macula is of significant importance in that this area provides the highest resolution for the images we see. The macula is comprised of multiple layers of cells which process the initial “analog” light energy entering the eye into “digital” electrochemical impulses.
RETINAL DISORDERS :--
There are two types of retinal degenerative disease:
* Retinitis pigmentosa (RP) and
* Age-related macular degeneration (AMD)
We describe these below in more detail.
The narrowing of the field of vision into “tunnel vision” can sometimes result in complete blindness. Some specific forms of RP and related conditions include Usher’s Syndrome, Leber’s Congenital Amaurosis, Stargardt’s Disease, Cone-RodDystrophy,Best’sDisease,Choroideremia, and Gyrate Atrophy.
SILICON CHIP SERVING AS BIONIC EYE :-----
The ASR microchip is a silicon chip 2mm in diameter and 25 microns thick, less than the thickness of a human hair. It contains approximately 5,000 microscopic solar cells called “microphotodiodes,” each with its own stimulating electrode. These microphotodiodes are designed to convert the light energy from images into electricalchemical impulses that stimulate the remaining functional cells of the retina in patients with AMD and RP types of conditions. The ASR microchip is powered solely by incident light and does not require the use of external wires or batteries. When surgically implanted under the retina—in a location known as “subretinal space”—the ASR chip is designed to produce visual signals similar to those produced by the photoreceptor layer. From their subretinal location, these artificial “photoelectric” signals from the ASR microchip are in a position to induce biological visual signals in the remaining functional retinal cells which may be processed and sent via the optic nerve to the brain. In preclinical laboratory testing, animal models implanted with the ASR devices responded to light stimuli with retinal electrical signals (ERGs) and sometimes brainwave signals (VEPs). The induction of these biological signals by the ASR chip indicated that visual responses had occurred. In past and present collaboration with the Hines, Cleveland and Atlanta Veterans Administration Medical Centers, Rush-Presbyterian St. Luke’s Medical Center and Stanford University’s Nano Fabrication Facility, Optobionics has been researching and developing means to further improve the function and biocompatibility of the ASR microchip.
In retinopathy of prematurity (RLF and ROP), the ASR microchip cannot stimulate the retina if an irreparable “funnel detachment” of the retina has occurred. Even if the retina can be surgically “flattened” and lacks significant scarring, there is still only a very limited possibility of vision improvement because of complications due to amblyopia. Amblyopia is caused when portions of the seeing part of the brain fail to develop in the absence of signals of clear vision from the eyes. The ASR microchip’s potential to provide improved vision is, therefore, much less likely in cases of early vision loss (such as Leber’s Congenital Amaurosis) compared with late vision loss types of RP. It is noted, however, that some patients experience improved vision in an amblyopic eye if, for some reason, vision in the better-seeing eye is lost thus an amblyopic eye is sometimes considered to be a “backup” eye.
Macular holes are conditions that we have not evaluated closely and cannot offer a definitive response to at this time.The microsurgical procedure consists of a standard ophthalmic operation called a vitrectomy and a retinotomy, plus the implantation of the chip, itself. The surgeon starts by making three tiny incisions in the white part of the subject’s eye, through which instruments are inserted. Through these incisions, the surgeon replaces the vitreous gel in the middle of the eye with saline. The surgeon then makes an opening in the retina through which fluid is injected: the fluid lifts up a portion of the retina from the back of the eye and creates a small pocket in the “subretinal space” just wide enough to accommodate the ASR® microchip. The surgeon then slides the implant into the subretinal space, much as one might slip a tiny coin into a pocket. Finally, the surgeon introduces air into the middle of the eye to gently push the retina back down over the implant. Over a period of one or two weeks, the air bubble is resorbed and replaced by fluids created within the eye.
The procedure typically takes about 2 hours. In January 2000, the US government’s Food and Drug Administration (FDA) authorized Optobionics to implant our Artificial Silicon Retina device in up to ten retinitis pigmentosa patients in a two-year safety and fesibility study.
In two-year clinical trials that began in June 2000, Optobionics implanted its microchip into the subretinal space of ten patients with RP, to study its safety and feasibility in treating retinal vision loss. At this time Optobionics is correlating and assessing clinical data from all these patients No patient has shown signs of implant rejection, infection, inflammation, erosion or retinal detachment related to the implanted microchip.
• The durability of the ASR chip in this location and the long-term safety, feasibility, and suitability of this procedure, however, are yet to be determined. A paper containing results of the first six patients, entitled The Artificial Silicon Retina Microchip for the Treatment of Vision Loss From Retinitis Pigmentosa, has been published in the April 2004 issue of Archives of Ophthalmology. This device is experimental and is not available for commercial sale. Also, we are not staffed to examine individual patients outside our clinical trials and do not offer other experimental treatments for RP and AMD.
THE STRATA BEHIND THE CERAMIC DEVICE :
"The Space Vacuum Epitaxy Center is a NASA-sponsored Commercial Space Center (CSC) at the University of Houston. NASA's Space Product Development (SPD) program, located at the Marshall Space Flight Center, encourages the commercialization of space by industry through 17 such CSCs. At the SVEC, researchers apply knowledge gained from experiments done in space to develop better lasers, photocells, and thin films technologies with both commercial and human promise. A schematic diagram of the retina a light-sensitive layer that covers 65% of the interior surface of the eye. SVEC scientists hope to replace damaged rods and cones in the retina with ceramic microdetector arrays. Image
courtesy A.
Ignatiev.Scientists at Johns Hopkins University, MIT, and elsewhere have tried to build artificial rods and cones before, notes Ignatiev. Most of those earlier efforts involved silicon-based photo-detectors. But silicon is toxic to the human body and reacts unfavorably with fluids in the eye -- problems that SVEC's ceramic detectors do not share. "SVEC ”conducting preliminary tests on the ceramic detectors for bio compatibility, and they appear to be totally stable" he says. "In other words, the detector does not deteriorate and [neither does] the eye.
"All of the nutrients feeding the eye flow from the back to the front," says Ignatiev. "If you implant a large, impervious structure [like the silicon detectors] in the eye, nutrients can't flow" and the eye will atrophy. The ceramic detectors are individual, five-micron-size units (the exact size of cones) that allow nutrients to flow around them.Artificial retinas constructed at SVEC consist of 100,000 tiny ceramic detectors, each 1/20 the size of a human hair. The assemblage is so small that surgeons can't safely handle it. So, the arrays are attached to a polymer film one millimeter by one millimeter in size. A couple of weeks after insertion into an eyeball, the polymer film will simply dissolve leaving only the array behind. The first human trials of such detectors will begin in 2002. Dr. Charles Garcia of the University of Texas Medical School in Houston will be the surgeon in charge."An incision is made in the white portion of the eye and the retina is elevated by injecting fluid underneath," explains Garcia, comparing the space to a blister forming on the skin after a burn. "Within that little blister, we place the artificial retina. " These first-generation ceramic thin film micro detectors, each about 30 microns in size, are attached to a polymer carrier, which helps surgeons handle them. The background image shows human cones 5- 10 microns in size in a hexagonal array. Image courtesy A. Ignatiev.Scientists aren't yet certain how the brain will interpret unfamiliar voltages from the artificial rods and cones. They believe the brain will eventually adapt, although a slow learning process might be necessary -- something akin to the way an infant learns shapes and colors for the first time. "It's a long way from the lab to the clinic," notes Garcia. "Will they work? For how long? And at what level of resolution? We won't know until we implant the receptors in patients. The technology is in its infancy."Ignatiev has received over 200 requests from patients who learned of the studies from earlier press reports. "I'm extremely excited about this," he says. He cautions that much more research is needed, but
"it's very promising. "
CONCLUSION:--
Both the the silicon one and ceramic film based developed by optobionic and svec respectively which restore vision in blind patients suffered by retinal disease specially retinitis pigmentosa (RP) , age related macular degeneration (AMD) and possibly other retinal conditions .
Download this Seminar Report
0 comments:
Post a Comment
Thanks for your Valuable comment