Visual prosthesis: Difference between revisions
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==Ongoing projects== |
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===Argus Retinal Prosthesis (Second Sight and the Doheny Eye Institute (USC))=== |
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Drs. Mark Humayun <ref name="Humayun''>[http://www.usc.edu/programs/neuroscience/faculty/profile.php?fid=45 Mark Humayun]</ref> and Eugene DeJaun were the original inventors of the active epi-retinal prosthesis <ref name="epi-retinal prosthesis |
Drs. Mark Humayun <ref name="Humayun''>[http://www.usc.edu/programs/neuroscience/faculty/profile.php?fid=45 Mark Humayun]</ref> and Eugene DeJaun were the original inventors of the active epi-retinal prosthesis <ref name="epi-retinal prosthesis"/>[http://artificialretina.energy.gov/howartificialretinaworks.shtml]</ref> and demonstrated proof of principle in acute patient investigations at Johns Hopkins University in the early 90s. In the late 90s Second Sight was formed to develop a chronically implantable retinal prosthesis. Their first generation implant had 16 electrodes and was implanted in 6 subjects between 2002 and 2004. Five of these subjects still use the device in their homes today. These subjects, who were all completely blind prior to implantation, can perform a surprising array of tasks using the device. More recently, the company announced that it has received FDA approval to begin a trial of its second generation, 60 electrode implant, in the US.<ref name="Second Sight Trial Announcement"/>[http://www.2-sight.com/Argus_II_IDE_pr.htm]</ref> <ref name="BBC">{{cite news |
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| author=Jonathan Fildes |
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| title=Trials for bionic eye implants |
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Revision as of 16:35, 18 April 2007
For the non-functional prosthetic or glass eye see Ocular prosthetic.
A visual prosthetic or bionic eye is a form of neural prostheses intended to partially restore lost vision or amplify existing vision. It usually takes the form of an externally-worn camera that is attached to a stimulator on the retina, optic nerve, or in the visual cortex, in order to produce perceptions in the visual cortex.
History
Scientific research since at least the 1950s has investigated interfacing electronics at the level of the retina, optic nerve, thalamus, and cortex. Visual prosthetics, which have been implanted in patients around the world both acutely and chronically, have demonstrated proof of principle, but do not yet offer the visual acuity of a normally sighted eye.
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 developement (due to ease of access to the retina among other considerations), vision loss due to degeneration of photoreceptors (retinitis pigmentosa, choroideremia, geographic atrophy macualr degeneration) is 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 blindess. Persons born with blindness may lack a fully developed optical nerve, which typically develops prior to birth.[citation needed]
Technological considerations
Visual prosthetics are being developed as a potentially valuable aide for individuals with visual degradation. The visual prosthetic in humans remains investigational, while visual prosthetics have been implemented in other animals. Visual prosthetics providing a level of visual acuity comparable to that of a camera are currently undergoing research trials in rats. Bionic visual implants have demonstrated the ability to partially recover lost sight in rats during laboratory testing.[citation needed]
Ongoing projects
Argus Retinal Prosthesis (Second Sight and the Doheny Eye Institute (USC))
Drs. Mark Humayun [1] and Eugene DeJaun were the original inventors of the active epi-retinal prosthesis [2][1]</ref> and demonstrated proof of principle in acute patient investigations at Johns Hopkins University in the early 90s. In the late 90s Second Sight was formed to develop a chronically implantable retinal prosthesis. Their first generation implant had 16 electrodes and was implanted in 6 subjects between 2002 and 2004. Five of these subjects still use the device in their homes today. These subjects, who were all completely blind prior to implantation, can perform a surprising array of tasks using the device. More recently, the company announced that it has received FDA approval to begin a trial of its second generation, 60 electrode implant, in the US.[3][2]</ref> [4] . Additonally they have planned clinical trials worldwide, all getting underway in 2007. Three major US government funding agencies (National Eye Institute, Department of Energy, and National Science Foundation) have supported the work at Second Sight and USC.
Microsystem-based Visual Prosthesis (MIVIP)
Designed by Claude Veraart at the University of Louvain, this is a spiral cuff electrode around the optic nerve at the back of the eye. It is connected to a stimulator implanted in a small depression in the skull. The stimulator receives signals from an externally-worn camera, which are translated into electrical signals that stimulate the optic nerve directly.[5]
Implantable Miniature Telescope
Although no truly a active prosthesis , an Implantable Miniature Telescope is one type of visual implant that has met with some success in the treatment of end-stage age-related macular degeneration.[6][7][8] This type of device is implanted in the eye's posterior chamber and works by increasing (by about three times) the size of the image projected onto the retina in order to overcome a centrally-located scotoma or blind spot.[7][8]
Harvard/MIT Retinal Implant
Joseph Rizzo and John Wyatt at MIT and the Massachusetts Eye and Ear Infirmary have developed a stimulator chip that sits on the retina and is in turn stimulated by signals beamed from a camera mounted on a pair of glasses. The stimulator chip decodes the picture information beamed from the camera and stimulates retinal ganglion cells accordingly. [5]
Artificial Silicon Retina (ASR)
The brothers Alan Chow and Vincent Chow have developed a microchip containing 3500 solar cells, which detect light and convert it into electrical impulses, which stimulate healthy retinal ganglion cells. The ASR requires no externally-worn devices. [5]
The Dobelle Eye
Similar in function to the Harvard/MIT device, except the stimulator chip sits in the primary visual cortex, rather than on the retina. One subject has had the system implanted in his brain since 1978 with no ill effects. [5] The status of this project is unknown after the passing of Dobelle.
The Virtual Retinal Display (VRD)
Laser-based system for projecting an image directly onto the retina. This could be useful for enhancing normal vision or bypassing an occlusion such as a cataract, or a damaged cornea. [5]
Other projects
Other notable researchers include Richard Normann and David Bradley at University of Chicago, Ed Tehovnik at MIT.
References
- ^ Mark Humayun
- ^ Cite error: The named reference
epi-retinal prosthesiswas invoked but never defined (see the help page). - ^ Cite error: The named reference
Second Sight Trial Announcementwas invoked but never defined (see the help page). - ^ Jonathan Fildes (16 February 2007). "Trials for bionic eye implants". BBC.
- ^ a b c d e James Geary (2002). The Body Electric. Pheonix.
- ^ Chun DW, Heier JS, Raizman MB. (2005). "Visual prosthetic device for bilateral end-stage macular degeneration". Expert Rev Med Devices. 2 (6): 657–65. PMID 16293092.
{{cite journal}}: CS1 maint: multiple names: authors list (link) - ^ a b Lane SS, Kuppermann BD, Fine IH, Hamill MB, Gordon JF, Chuck RS, Hoffman RS, Packer M, Koch DD. (2004). "A prospective multicenter clinical trial to evaluate the safety and effectiveness of the implantable miniature telescope". Am J Ophthalmol. 137 (6): 993–1001. PMID 15183782.
{{cite journal}}: CS1 maint: multiple names: authors list (link) - ^ a b Lane SS, Kuppermann BD. (2006). "The Implantable Miniature Telescope for macular degeneration". Curr Opin Ophthalmol. 17 (1): 94–8. PMID 16436930.