Retinal malfunction, due to degenerative retinal diseases, is a leading cause of blindness and visual impairment. Implantation of a retinal prosthesis is a technology for restoring some useful vision in individuals suffering from retinal-related blindness.
The retina is a multi-layered light-sensitive structure that lines the posterior, inner part of the eye. The retina contains photoreceptor cells, for example rods and cones, which capture light and convert light signals into neural signals transmitted through the optic nerve to the brain. Rods are responsible for light sensitive, low resolution black and white vision, whereas cones are responsible for high resolution color vision. Most cones lie in the fovea, which defines the center of the retina.
U.S. Pat. No. 6,976,998 to Rizzo et al. describes an externally powered ocular device that is described as a safe and effective retinal prosthesis. The device is described as performing all functions needed of a retinal prosthesis with electronic components that are placed outside the wall of an eye, are powered wirelessly by an external power source, and which provide a patient with a view determined by natural motion of the eye and triggered by natural incident light converging at the retina. An externally powered, light-activated, sub-retinal prosthesis is described in which natural light entering the eye conveys visual details to the sub-retinal prosthesis, while wireless radiofrequency transmission provides the power needed to stimulate the retina, which would be insufficient if it were obtained from the intensity of incoming light alone.
U.S. Pat. No. 4,628,933 to Michelson describes a visual prosthesis for blindness due to retinal malfunction which includes a compact device having a close-packed array of photosensitive devices on one surface thereof. A plurality of electrodes extends from the opposed surface of the device and are connected to the outputs of the photosensitive devices. The device is adapted to be inserted in the posterior chamber of the eye, generally disposed at the focal plane of the optical pathway and impinging on the retina. Anchoring means secure the device with the electrodes operatively connected to the neuron array at the surface of the retina to stimulate the neurons in a pattern corresponding to the illumination pattern of the photosensitive array. The device is powered by externally induced electromagnetic or radio frequency energy, and is encased in a biologically inert housing. An amplifier array may be interposed between the sensing elements and the electrodes to amplify, shape, and time-process the visual signals.
U.S. Pat. No. 6,298,270 to Nisch describes a retina implant that has a substrate with a surface for applying same to a retina. The substrate comprises electrodes for stimulating cells within the retina. The electrodes are provided on the surface and are exposed to visible light impinging on the retina such that stimuli are exerted on the cells by the electrodes. The implant, further, comprises a photovoltaic layer responsive to non-visible light. The stimuli are locally switched utilizing a voltage generated by the photovoltaic layer.
U.S. Pat. No. 6,507,758 to Greenberg et al. describes a device for directly modulating a beam of photons onto the retinas of patients who have extreme vision impairment or blindness. Its purpose is to supply enough imaging energy to retinal prosthetics implanted in the eye which operate essentially by having light (external to the eye) activating photoreceptors, or photo-electrical material. The device is described as providing sufficient light amplification and does it logarithmically. While it has sufficient output light power, the output light level still remains at a described safe level. Most embodiments include balanced biphasic stimulation with no net charge injection into the eye. Both optical and electronic magnification for the image, as for example, using an optical zoom lens, is incorporated. It is described as being otherwise infeasible to zoom in on items of particular interest or necessity. Without proper adjustment, improper threshold amplitudes would obtain, as well as uncomfortable maximum thresholds. Therefore, to adjust for these, a way is described as providing proper adjustment for the threshold amplitudes and maximum comfortable thresholds. Furthermore, to the extent that individual stimulation sites in the retina give different color perceptions, upon stimulation, then colors of the viewed scene is correlated with specific stimulation sites to provide a certain amount of color vision.
U.S. Pat. No. 6,324,429 to Shire et al. describes a chronically-implantable retinal prosthesis for the blind, which is described as restoring some useful vision to patients. The epiretinal devices are described as thin, strong, and flexible and constructed of or encapsulated in known biocompatible materials, which are described as having a long working life in the eye's saline environment. The function of the implants is to electrically stimulate the ganglion cell layer at the surface of the retina using controlled current sources. The implant has planar form and is described as flexible and exceptionally low mass, minimizing patient discomfort and fluid drag. These physical attributes are described as substantially reducing the potential of harm to the most delicate structure of the eye, the retina, and therefore enhance the long term safety and biocompatibility of the device. Since no micro-cables are required to be attached to the device, and its overall form and edges are rounded, the device is described as not stressing the retina during chronic implantation. A provision is also made for nutrients to reach the retinal cells underneath the device to assure their long-term health. The device is meant to process and retransmit images and data to the ganglion cells on the retina surface.
U.S. Pat. No. 5,935,155 to Humayun et al. describes a visual prosthesis comprising a camera for perceiving a visual image and generating a visual signal output, retinal tissue stimulation circuitry adapted to be operatively attached to the user's retina, and wireless communication circuitry for transmitting the visual signal output to the retinal tissue stimulation circuitry within the eye. To generate the visual signal output, the camera converts a visual image to electrical impulses which are sampled to select an image at a given point in time. The sampled image signal is then encoded to allow a pixelized display of it. This signal then is used to modulate a radio frequency carrier signal. A tuned coil pair having a primary and a secondary coil is used to transmit and receive the RF modulated visual signal, which is then demodulated within the eye. The retinal stimulation circuitry includes a decoder for decoding the visual signal output into a plurality of individual stimulation control signals, which are used by current generation circuitry to generate stimulation current signals to be used by an electrode array having a plurality of electrodes forming a matrix. The intraocular components are powered from energy extracted from the transmitted visual signal. The electrode array is attached to the retina via tacks, magnets, or adhesive.
U.S. Pat. No. 7,047,080 to Palanker et al. describes a self-sufficient retinal prosthesis powered by intra-ocular photovoltaic cells illuminated only by ambient light. Photovoltaic cells can be disposed at the periphery of the retina or in the anterior chamber of the eye. An adaptive retinal prosthesis is also provided, such that the number of pixels energized in the prosthesis is selected according to the variable available power from ambient light.
US Patent Application Publication 2006/0282128 to Tai et al. describes intraocular retinal prosthesis systems, and methods for fabricating such prostheses. A prosthesis device includes a cable region that connects an electrode array region with a power and data management region. The electrode array region includes one or more arrays of exposed electrodes, and the power and data management region includes various power and control elements. The power and data management elements, in one aspect, include an RF coil or coils and circuit arrangements and/or chips configured to provide drive signals to the electrodes via a cable and receive power and signals from the RF coil or coils. Each region includes elements fabricated on or in a single polymer layer during the same fabrication process.
US Patent Application Publication US 2007/0191909 to Ameri et al. describes a wide-field retinal prosthesis providing an increased field of vision with a relatively small scleral incision. The retinal prosthesis is described as including a flexible substrate comprising a central member and at least one wing, with an array of electrodes disposed therein that are configured to stimulate the central and peripheral nerves of the retina. The prosthesis can include a desired number of apertures for suitable flexibility.
U.S. Pat. No. 5,597,381 to Rizzo describes a method for epi-retinal implantation of an object into a subject. The method includes rendering the normally transparent cortical vitreous visible and separating at least a portion of a cortical vitreous of the subject away from an adherent retinal surface to form an epi-retinal space between the retina and the separated cortical vitreous material. An object to be implanted may be introduced into the epi-retinal space and the object engaged with a surface of the retina. In preferred embodiments, the object may then be adhered to the surface of the retina. A method for implantation of a neural contact structure for contact with neural tissue, for example, neural tissue of the retina within which are ganglion cells to be electrically stimulated is also described. The contact structure comprises a first portion for attachment to a first bodily location, such as the inner surface of the retina, and a second portion interconnected with the first portion via an interconnection and being held in contact with the neural tissue. The interconnection exhibits a weak restoring force which in conjunction with the geometry of the second portion provides a preselected desired pressure of contact against the neural tissue. As adapted for the retina, the interconnection exhibits a weak restoring force developed in response to curvature of the interconnection along the inner radius of the retina.
U.S. Pat. No. 6,368,349 to Wyatt et al. describes a neural prosthesis for implantation within an eye. The prosthesis includes a foldable substrate and at least one electronic component supported by the substrate. At least one microchannel is disposed within the substrate. Upon inflation, the foldable substrate is described as unfolding to provide for close contact of the electronic component with neural tissue, thus facilitating surgical implantation through a narrow incision, yet allowing the unfolded device to cover a sufficiently large portion of the patient's retina to provide useful vision.
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