The Development of Subretinal Microphotodiodes for Replacement of Degenerated Photoreceptors

Zrenner, E.; Miliczek, K.-D.; Gabel, Virginie; Graf, H.-G.; Guenther, Elke; Haemmerle, H.; Hoefflinger, B.; Köhler, Konrad; Nisch, W.; Schubert, M.B.; Stett, Alfred; Weiß, Stefan

doi:10.1159/000268025

Cited by 207 publications

(107 citation statements)

References 5 publications

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“…Two main approaches exist: the epiretinal approach in which the implant is placed on the vitreal side of the retina [6] and the subretinal approach in which the implant replaces degenerated photoreceptors [7][8]. The epiretinal approach involves stimulation of the nerve fiber layer with electrodes that receive input from an external camera [6,[9][10][11].…”

Section: Introductionmentioning

confidence: 99%

Status of the feline retina 5 years after subretinal implantation

Pardue

Ball

Phillips³

et al. 2006

JRRD

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Abstract-Retinal prosthetics are designed to restore functional vision to patients with photoreceptor degeneration by detecting light and stimulating the retina. Since devices are surgically implanted into the eye, long-term biocompatibility and durability are critical for viable treatment of retinal disease. To extend our previous work, which demonstrated the biocompatibility of a microphotodiode array (MPA) for 10 to 27 months in the normal feline retina, we implanted normal cats with an MPA implant backed with either an iridium oxide or platinum electrode and examined retinal function and biocompatibility for 3 to 5 years. All implants functioned throughout the study period. Retinal function remained steady and normal with a less than 15 percent decrease in electroretinogram response. The retinas had normal laminar structure with no signs of inflammation or rejection in areas adjacent to or distant from the implants. Directly over the implants, a loss of photoreceptor nuclei and remodeling of inner retinal layers existed. These results indicate that the subretinal MPA device is durable and well tolerated by the retina 5 years postimplantation.

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Section: Introductionmentioning

confidence: 99%

Status of the feline retina 5 years after subretinal implantation

Pardue

Ball

Phillips³

et al. 2006

JRRD

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“…Our approach is the development of electrical devices that could be implanted in the subretinal space as shown in Fig. 1 [8]. The reason why we introduce a subretinal approach is as follow: The device stimulates the early stage of the visual system so that potentially high resolution input to the outer retina could be achieved.…”

Section: Introductionmentioning

confidence: 99%

“…A simple photodiode array has been used as an implantable device in the subretinal space mainly due to its simple configuration without power supply [8]. The photo current is directly injected into the retinal neurons.…”

Section: Introductionmentioning

confidence: 99%

System implementation of a CMOS vision chip for visual recovery

Uehara

Furumiya

et al. 2003

Sensors and Camera Systems for Scientific, Industrial, and Digital Photography Applications IV

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We have developed a CMOS vision chip, an image sensor with pixel-level signal processing, to replace photoreceptor cells in the retina. In this paper, we describe a pixel-level signal processing, which is to control on the stimulus waveform and the amount of the electrical injection charge.Our CMOS vision chip is an array of a pixel, which consists of a photo detector, a pulse shaper, and a current stimulus circuit. The photo detector circuit generates a pulse frequency modulated (PFM) pulse, which frequency is proportional to the intensity of the incoming light [1] [2]. The PFM photo detector is also modified to restrict the maximum frequency of PFM pulse signal for safety neural stimulation [3].The PFM pulse signal should be converted into suitable waveform for efficient neural stimulation. We have employed a pulse shaper to generate one stimulus pulse from one PFM pulse. The pulse parameters (i.e., pulse duration, polarity, etc) of the output pulse signal are controlled by the external signal.For the electrical neural stimulus, the stimulus intensity is given by the amount of the electrical injection charge. The amount of the injection charge should be enough to evoke a phosphene but should be low to avoid the damage of the retinal tissue caused by the excess charge injection. In our prototyped CMOS vision chip, the stimulus current amplitude is used to control the amount of charge. The 6-bit binary-weighted digital-to-analog converter (DAC) with 2µA resolution is used to control the stimulus current amplitude.

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“…This paper will focus on the first bullet. Two possible approaches for retinal implants, an epi-retinal [1] and a subretinal [2], have been proposed and are currently being pursued [3]. In the sub-retinal approach, stimulating electrodes are placed beneath the retina at the location of the retinal photoreceptor layer.…”

Section: Introductionmentioning

confidence: 99%

Image Processing and Interface for Retinal Visual Prostheses

Liu

Fink

Tarbell

et al.

2005 IEEE International Symposium on Circuits and Systems

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Abstract-Controlled electrical stimulation of the retina can result in visual percepts in blind patients. In contrast to the over 100,000,000 photoreceptors in a healthy retina, even hundreds of pixels/electrodes of a retinal implant may restore low-resolution vision for unaided mobility and large print reading. We describe the real-time application of image processing techniques such as contrast and brightness enhancement, grayscale histogram equalization, edge detection, and grayscale reduction, to enhance visual perception provided by a retinal implant. We discuss schemes for reducing the amount of data transmitted wirelessly to the implant, as well as the interface between the external imaging unit and retinal implant.

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The Development of Subretinal Microphotodiodes for Replacement of Degenerated Photoreceptors

Cited by 207 publications

References 5 publications

Status of the feline retina 5 years after subretinal implantation

Status of the feline retina 5 years after subretinal implantation

System implementation of a CMOS vision chip for visual recovery

Image Processing and Interface for Retinal Visual Prostheses

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