Retinal Prosthesis for the Blind

Margalit, Eyal; Maia, Maurício; Weiland, James D.; Greenberg, Robert J.; Fujii, Gildo Y.; Torres, G.; Piyathaisere, Duke V.; OʼHearn, Thomas M; Liu, Wentai; Lazzi, Gianluca; Dagnelie, Gislin; Scribner, Dean A.; Juan, Eugene de; Humayun, Mark S.

doi:10.1016/s0039-6257(02)00311-9

Cited by 384 publications

(230 citation statements)

References 119 publications

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“…High stimulation thresholds are at least partially the result of a poor interface between the electrode array and the target tissue [8,11,12]. Chronically implanted devices may become enveloped by fibrotic tissue, which likely increases thresholds by increasing the electrical resistance of the tissue and also by creating a greater physical separation between the electrodes and the neurons.…”

Section: Introductionmentioning

confidence: 99%

Tissue engineering applied to the retinal prosthesis: Neurotrophin-eluting polymeric hydrogel coatings

Winter

Gokhale

Jensen

et al. 2008

Materials Science and Engineering: C

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Several groups are developing visual prostheses to aid patients with vision loss. While these devices have shown some success in the clinic, they are severely limited by poor resolution, and in many cases have as few as 15 electrodes. Pixel density is poor because high stimulation thresholds require large electrodes to minimize charge density that would otherwise damage the electrode and tissue. A significant contributor to high stimulation threshold requirements is poor biocompatibility. We investigated the application of one system popular in tissue engineering, drug-releasing hydrogels, as a mechanism to improve the tissue-electrode interface. Hydrogels studied (i.e., PEGPLA photocrosslinkable polymers) released neurotrophic factors (i.e., BDNF) known to promote neuron survival and neurite extension in the retina. Hydrogels were examined in co-culture with retinal explants for 7 and 14 days, at which time neurite extension and neurite density was measured. Neurite extension was enhanced in samples exposed to BDNF-releasing hydrogels at 7 days; however, these increases were absent by day 14 suggesting declining drug release. Thus, PEGPLA hydrogels are excellent candidates for short-term (< 14 day) acute release of therapeutic factors in the retina, but will require additional modifications for application with neural prostheses. Additionally, these results suggest that the effects of neurotrophic factors are short-lived in the absence of additional support cues, and tissue engineering systems employing such factors may only produce transient benefits to the patient.

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Section: Introductionmentioning

confidence: 99%

Tissue engineering applied to the retinal prosthesis: Neurotrophin-eluting polymeric hydrogel coatings

Winter

Gokhale

Jensen

et al. 2008

Materials Science and Engineering: C

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“…These results were expected due to the relationship of the epiretinal implant with the vitreous humor, which has a greater capacity to dissipate the heat generated by this implant (Margalit et al, 2002).…”

Section: Discussionmentioning

confidence: 79%

“…Both involve degeneration of the photoreceptor cells, rendering the visual system to become insensitive to light (Peachey and Chow, 1999). The development of retinal prosthesis is based on the premise that an application of external electrical stimulus can be an alternative approach to potentially restore the function of the visual system Margalit et al, 2002).…”

Section: Introductionmentioning

confidence: 99%

“…These implants were designed to substitute different physiological functions. The subretinal substitutes the degenerated photoreceptors' cells while the epiretinal stimulates directly the ganglion cells (Margalit et al, 2002). Consequently, the two types of chips are implanted in different places.…”

Section: Introductionmentioning

confidence: 99%

“…Consequently, the two types of chips are implanted in different places. The subretinal is implanted under the retina's surface, between the pigment epithelium and the photoreceptors cells, while the epiretinal one is placed in contact with the inner surface of the retina (Margalit et al, 2002;Schwiebert et al, 2002;Zrenner, 2002).…”

Section: Introductionmentioning

confidence: 99%

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