Retinitis Pigmentosa,(RP) is a blinding disease characterized by massive and progressive reductions in the population of photoreceptor cells, result in losing night vision, followed severely loss of peripheral vision and often total blindness. No effective treatment is yet available for RP. Electrical stimulation of the retina through a bioelectronic implant, replaces some of the lost function of the degenerated neurons, allowing test subjects with experimental implants to perform simple visual tasks. Thus, retinal implants have potential to provide an effective means of restoring vision to RP patients.
Response thresholds and the loss of retinal neurons have been studied separately in clinical trials and in pre-clinical studies, yet no study has simultaneously studied the structure and function of the degenerated retina. Only a few of the threshold studies, using animal model induced retinal degeneration, have performed histological analysis of the same retina, and this examination has been minimal. Safety studies of electrical stimulation of the retina are also limited. Safety is a concern for a high-resolution retinal prosthesis, since a smaller electrode may use a high charge density to elicit a response.
This thesis investigated the response both the electrical stimulation and the ganglion cell densities at different ages of in animal model of retinal degeneration. Acute stimulation was carried out by electrically stimulating the retina and recording responses from superior colliculus simultaneously. This research presents the first quantitative measurement of electrophysiological and morphometric properties in degenerate retina. It also represents the only known study to examine the response threshold and ganglion cell density at multiple time-points following photoreceptor degeneration, and to note the safe charge density with a limited pulse range using a 75-ìm electrode. This thesis also provided a means of investigating the spatial properties of electrical stimulation in a normal animal model. Finally, this thesis proposed a model explaining the increased threshold noted in aged degenerate retina with reduced cell number.
The ultimate goal of this work is to advance the understanding of electrical stimulation in degenerate retina using small electrode and thus enable the transition from low resolution to high resolution retinal prostheses. This research will hopefully lay the groundwork for the successful development of high resolution retinal prostheses to enable individuals suffered with RP to perform important visually-guided tasks, such as navigation, reading, and facial recognition.
|Advisor:||Weiland, James D.|
|Commitee:||Grzywacz, Noberto, Hirsch, Judith, Humayun, Mark S.|
|School:||University of Southern California|
|School Location:||United States -- California|
|Source:||DAI-B 70/08, Dissertation Abstracts International|
|Subjects:||Neurosciences, Biomedical engineering|
|Keywords:||Electrophysiology, Immunocytochemistry, Retinal degeneration, Retinal prosthesis, Tissue-electrode interface|
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