Researchers have been testing microelectronic retinal implants as a method of restoring vision in patients rendered blind by degenerative diseases of the retina such as retinitis pigmentosa (RP) and age-related macular degeneration (ARMD).
The system is meant to partially restore useful vision to people who have lost their photoreceptors due to retinal diseases such as retinitis pigmentosa (RP). Tests regarding electrical stimulation of the retinal surface have demonstrated that such stimulation may induce light sensation. Retinal neurons are preserved after death of photoreceptors.
The FDA approved the system as a humanitarian use device; an approval that is limited to fewer than 4,000 people in the United States each year. An artificial retinal implant replicates some of the functions of the retina; helping people blinded with a rare genetic disorder restore vision.
German company “Retina Implant” recently conducted human tests with its 1,500-pixel implant that does not depend on a camera but instead directly harvests light and transmits that data to remaining neurons (“Microchip Restores Vision”). A photodiode array replaces the photoreceptors.
Artificial Retinal Implants Market by Types of Retinal Implants: There are two main types of retinal implants. Epiretinal implants are placed in the internal surface of the retina; while sub retinal implants are placed between the outer retinal layer and the retinal pigment epithelium.
Epiretinal Implants: Epiretinal implants are placed on top of the retinal surface, above the nerve fiber layer; directly stimulating ganglion cells and bypassing all the other retinal layers. An array of electrodes is stabilized on the retina using micro tacks that penetrate into the sclera.
Typically, external video camera onto eyeglasses acquires images and transmits processed video information to the stimulating electrodes via wireless telemetry. The real-time image processing involves reducing the resolution, enhancing contrast, detecting the edges in the image, and converting it into a spatio-temporal pattern of stimulation delivered to the electrode array on the retina.
The advantage of epiretinal implants is that they directly stimulate the retinal ganglion cells; thereby bypassing all the other retinal layers. Epiretinal implants could provide visual perception to individuals even if all the other retinal layers have been damaged.
Subretinal Implants: Subretinal implants sit outside the retina; between the photoreceptor layer and the retinal pigment epithelium; directly stimulating retinal cells and relying on the normal processing of the inner and middle retinal layers.
The implant is mechanically constrained by the minimal distance between the outer retina and the retinal pigment epithelium. A subretinal implant consists of a silicon wafer containing light-sensitive micro photodiodes, which generate signals that directly inject the resultant current into the underlying retinal cells via arrays of microelectrodes.
The advantage of subretinal implant is its simpler design. The light acquisition, processing, and stimulation are all carried out by microphotodiodes mounted onto a single chip, as opposed to the external camera, processing chip, electrode array associated with an epiretinal implant.
Artificial Retinal Implants Market is segmented based on Geographical Regions into North America, Europe, Asia-Pacific, and RoW.
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